Hiking Science

Optimal Hiking Grade - A 50 Hike GPS Analysis

2011-02-04T11:15:00.000-08:00

Do you care about optimal hiking grade? Maybe not, but it's interesting for us to think about.

Intuitively, some may think that steeper trails should get you up higher more quickly because less energy is being put into the "horizontal miles" that a less steep trail would need.

However, we probably also feel that at some point something becomes too steep to ascend without the looseness of the terrain affecting our pace.

So what's the "optimal" grade? Well, I'm sure the answer is unique to an individual, but let's look at one person.

We previously did a little exploration into how Vertical Ascent Rate (VAR) varied with the steepness of a trail, but only with one example. Now I've combined 50 hikes worth of data.

The hikes:

Mostly in southern California (especially San Gabriels), some in Sierra and Bay Area
Diverse in conditions, includes much on trail and off trail
Some have brush
Varied terrain (loose, bouldering, etc...)

But it's a set of "real" hikes that I've done. A little Matlab coding and analysis, and we can see how often a given grade of terrain was hiked:

Interesting to see, but no surprise that as the terrain got steeper, it was encountered / hiked with less frequency.

Now, for further analysis, I didn't want to look at all of the data. I know that my hiking pace was generally consistent between hikes, but of course would vary some depending on, among others

How hard I was trying
How long the hike was
Was I with others, going at varied paces?

So I wanted to cut out the lower and upper ends. So I took all the data and sorted it by grade, and created "bins" that spanned every 1% of grade. For each % grade, I wanted to reduce the amount of data we were going to look at. Specifically, I cut out the lower 50% and top 10% of values, leaving the 50-90% values. (Note: this reduced data, but the trends remained the same even if I didn't)

So, over 50 hikes, this is how my hiking speed varied with grade:

Again, no surprise that speed decreases as grade increases. But let's move on to the good stuff - how does VAR vary with grade?

Of course there is some variance, but we see an increase in VAR from 0% to a bit above 40%, then we see some decreasing. We see a similar trend when going downhill (negative grades) although the variance is higher.

As seen in the first graph, the amount of time spent on steep slopes is much less than on less steep (<20%) slopes, so perhaps not enough conditions have been crossed to give a broad conclusion about VAR on steep slopes. But the current set includes much diverse hiking - hiking on very steep use trails, hiking off trail, scrambling, etc... And in those conditions, after 40% grade, the steepness began costing energy, likely due to looseness of terrain, brush, change in mechanics.

The "why" is speculative. But the data is real. And at least for this hiker, 40% grade seems just right.

I'd like to compare to this other hikers. If you have a collection of GPS files you wouldn't mind sending me, I'd like to perform this analysis on others' data.

Hiking Biomechanics Part 1 - Center of Mass Control

2011-01-18T18:49:00.000-08:00

Understanding mechanics provides the foundation for strong understanding of human movements (like hiking).

Why would you care about hiking mechanics? Well perhaps you have some questions about joint loading, energy expenditure, technique...and grasping basic principles may lead you to better understanding to answer such questions (and also realize that usually it is not as black and white as some may say).

For instance, why do we expend energy when walking on flat ground?

Short Take Home Message:

The need to keep angular momentum low (no rotating) constrains our choices in how we move.

Longer Explanation (Just go to "summary" if it's too long-winded)

Center of Mass
Now, biomechanics can have many levels of analysis, but we must start with the most basic, which would take us back to physics and representing the entire body as one point mass, called your Center of Mass (CM). We'll stick to 2D.

The CM is a theoretical point in which allow Newton's Law's of Motion to be easily applied.

åF = ma, remember? In any direction, the sum of the external forces acting on the human body must equal the mass of the body (m) times the acceleration of the CM. This is why the CM is special - even though a reaction force (Fy) is applied at the foot, the toe itself is actually not accelerating. What is guaranteed to accelerate at a known rate is the CM. Movement of any specific segment requires more information.

In the horizontal direction, the horizontal force at the feet define CM acceleration. In the vertical direction, its the vertical force at the feet minus bodyweight force (mg).

When walking on flat ground, horizontal acceleration should be 0 in theory. Once we have a forward velocity, the body should continue forward at the same velocity unless a backwards force is applied. Why would we do that?

In the vertical direction, acceleration on average should also be 0, since our CM shouldn't be changing in vertical position (this is much different when ascending a mountain, of course). Since we have a bodyweight force acting downward, we need an equal force in the upward direction on our feet to maintain acceleration of the CM at 0.

If these were easily maintained, then we wouldn't have to add force to the system ever. But clearly we do. Why is that?

Well there's one more direction - angular

Are you doing somersaults when hiking?

åM = Iα

The sum of the moments (M) about the center of mass must equal the inertia of the CM times the angular acceleration of the CM. Basically, if the force at the foot is not directed in the path of the CM, then it will create a moment about the CM. This, in turn will induce rotation, such as when attempting a somersault.

Take a look at the diagram below. If the resultant force acting of the feet pass through the center of mass (b), then no angular acceleration is generated. However if the force does not pass through the CM (a), then we begin rotating forward or backward.

Regulation of angular impulse during fall recovery

How do you walk?

So, in 2D, you have 3 constraints defined by CM control: 1) Horizontal acceleration ~ 0, 2) Vertical acceleration ~ 0, and 3) Angular acceleration ~ 0.

#3 is by far the least considered, but the most important. If you start rotating, you will soon be out of position to correct yourself, whereas with the first two your orientation relative to the ground still allows you to correct your balance easily.

How does this affect how you walk? Think about where your foot contacts the ground the ground. It's probably somewhat in front of the rest of your body. If that's the case, then the horizontal force must be in the negative direction so that the resultant force passes through the CM (blue). It has to to keep you from rotating. The negative force starts slowing you down, so then you must generate a positive horizontal force later to speed you back up (green).

This means you must generate both positive and negative work in the horizontal direction, both of which require some energy.

So why do you think you put your foot ahead of you, if it produces a backwards force? Well I think that would be good discussion to continue in another post.

Summary

Your body can be represented as one point, called the Center of Mass, for some basic analyses.
The CM must be tightly controlled in both linear and angular directions to maintain balance.
When walking, we produce both forward and backward forces in order to keep angular acceleration minimal.
This creates both positive and negative work which violates the generic assumption that no mechanical work is performed in the horizontal direction.

Salt and Cramp Tips

2010-12-11T20:54:00.000-08:00

This is a post from nutritionist Ellen Coleman that was made in this post and she allowed me to repost it here.

Howdy All :)

A lot of people were having muscle cramps on Skyline yesterday. Although it wasn't hot, it was warm for those of us who live in more temperate climates (Riverside, Orange County, San Diego) and who normally start hiking at 5 to 6 K.

Warm, dry weather can cause significant sweat losses and people may not be aware of how much fluid they're losing. In addition to water losses, sweating results in losses of electrolytes, especially sodium and chloride (salt). Muscle cramps are caused by sodium losses, not potassium or magnesium.

Although the amount of salt in sweat varies, most people lose about 800 mg for every two pounds (one quart) of sweat. Some people are salty sweaters and lose much more, regardless of their fitness level or degree of heat acclimation. Salty sweaters generally have white stains on their shirts/shorts and the sweat burns the eyes.

Heat-related muscle cramps occur during prolonged exercise when there has been profuse and prolonged sweating. Muscle cramps can occur when the salt lost in sweat isn't replaced. Hikers/athletes who are prone to heat cramps have high sweat rates and/or lose a considerable amount of salt in their sweat.

Prevention is always best. Eating salty foods and/or consuming a sports drink with salt can replace sodium losses and maintain hydration (the body needs salt to retain water).

For cramp prone people, it may be helpful to add additional salt to the sports drink -- 1/4 to 1/2 teaspoon of salt to 32 ounces of sports drinks. Some sports drinks contain a higher amount of salt -- Gatorade Endurance and Powerbar Endurance. Both provide about 800 mg per quart.

If you're drinking plain water while hiking in warm weather, it's even more critical to have a source of salt. Sources of salt:

1) Table salt -- 1/2 teaspoon has 1000 mg of sodium -- close to the amount hikers lose in 2 lbs of sweat. You can carry salt in a baggie, carry those little fast-food salt packets, or even salt your water (which isn't appealing to most people).

2) Salt tablets -- vary in sodium from 100 to 1000 mg per tablet. I am not a fan of Endurolytes as they don't provide enough sodium. Cramps are caused by sodium losses. I recommend using a salt tablet that provides at least 500 mg.

3) For those folks who can't do sports drinks, NUUN can be added to plain water. It's flavored so you don't notice the salt.

4) Salty foods. Pretzels, beef jerky, baked or regular chips, salted nuts, salted crackers.

5) Carbohydrate gels with a higher sodium content = 200 mg per gel.

How much sodium? Depends on your sweat rate and how much sodium you lose. I am a salty sweater. I drank three quarts of Gatorade Endurance yesterday (2400 mg) and ate three PowerGels with 200 mg of sodium (600 mg). Total = 3000 mg. It took me 5.5 hours, so I consumed about 500 mg per hour.

Prior to my jacked up spine, I did marathons and the Ironman triathlon. I work with endurance athletes to improve their performance and help them feel better when they compete. Skyline is an endurance activity, as is hiking Whitney or the Grand Canyon. My goal with hiking nutrition is to help people feel better when they hike.

Miles of smiles,

Ellen

VO2 Max Test - Useful for training but does not predict performance

2010-09-27T20:27:00.000-07:00

I recently did another VO2 max test in USC's Kinesiology lab to help some new instructors get acquainted with setup and and watch how a test goes.

VO2 max tests are pretty cool - if you enjoy high intensity exercise. You don't need to have one done to evaluate performance, but it does act as a good reference tool for training guidelines.

Here's the blurb I wrote in the description:

VO2 max absolute units : 5.45 L/min
Workload at Failure: 14% grade, 8 mph (last stage of Modified Bruce Test)
Max Heart rate: 194 bpm
Blood Lactate at Failure: ~ 19.5 mmol/L

Bodyweight: 190 lbs
VO2 max relative units: 63 ml/min/kg

A VO2 max test attempts to measure your maximal oxygen consumption i.e. aerobic capacity of your cardiovascular system. Fitness, genetics, gender, age, and body composition all play roles in a person's value. While VO2 max is great for creating a sort of reference for training, it is not a great indicator of aerobic performance. A person can yield a high VO2 max score, but not be able to sustain a high % of VO2 max for a given time.

If you want to evaluate cardiovascular performance & endurance, one way would be to see how long you could last at 80% of the VO2max workload. This weens out some factors such as bodyweight and efficiency - both of which affect performance but not cardiovascular conditioning.

VO2 max in relative units scales significantly by variance in bodyweight. A subject's bodyweight could vary up to 40 lbs while having the same cardiovascular conditioning and absolute VO2 max in (L/min), but would have drastically different relative VO2 score.

Let me comment a little more, and add a better link to hiking.

You don't need to be training for a VO2 max. You should be training in a way that optimizes around the hike / climb / run intensity and duration that you are focusing on. 30 second sprints might elicit improvement in VO2 max, but they are hardly going to do much for multihour endurance activities. 5-6 minute interval runs, however, can improve both endurance and VO2 max. The point is, proper training will lead to improved endurance and increased VO2 max as a byproduct.

For elite athletes looking for every edge, I'm sure very specific training protocols could call for specific VO2 max training. But for most of us mortals, don't worry about it. It helps to know what your max output is so you can set training paces for intervals (i.e., run at 90% VO2 max for 6 minutes, rest for 3, repeat), but you can do that with heart rate alone.

Even for hiking, intervals of 5 -10+ minutes can yield great results. This relates to the post below talking about anaerobic and aerobic energy pathways. A 5 min interval will be at an intensity high enough to use up your anaerobic capacity in the first 2-3 minutes, then leaving you with 3-4 minutes of high intensity aerobic training. The key is to get to aerobic (high heart rate) stages for at least a few minutes to get a sufficient stimulus to improving aerobic endurance. Intervals of 2 or less minutes may not get the same aerobic workout.

A few intervals in a quick 1/2 hour hike up can vastly improve your endurance on long treks on the weekends to come.

Why moving a little too fast can cost you a lot, especially at altitude

2010-08-29T13:50:00.000-07:00

Ever head out trying to follow someone's blistering pace, only to finally slow down and feel depleted? When that happens, you actually can't just slow down a little bit to "make up" for speeding up before. No, basically you've screwed yourself for the rest of the day. Why?

When you hike (or run, bike, etc...), you are using multiple energy pathways. The rate of energy production from each of these pathways is different.

Reference

For the sake of simplicity, we are only going to talk about the two systems that use glycogen (stored sugar). Anaerobic glycolysis can produce ATP (energy) at a faster rate than aerobic glycolysis can. The faster you are moving and harder you are working, the more energy you are going to get anaerobically. Ok sounds great!

But as you would guess, there's a cost to that. The cost is how much glycogen is used.

Aerobic glycolysis requires 2 molecules of glucose to produce 32 ATP (mid 30's, it's not clear the exact amount).

Anaerobic requires 2 molecules of glucose to produce 2 ATP.

That means that using anaerobic energy will suck up 16 times the amount of stored glycogen as using aerobic!!! And since stored glycogen takes days to replenish, you aren't getting that energy back during the day.

Below is a theoretical (as in don't take the number literally, but they make a point) graph of how much elevation you can gain depending on how fast you are going, approximately based on the carbs in / energy out values above. And yes it's a "duh" conclusion - slow but steady will take you a lot farther.

Its like having two engines in your car that share a fuel source - one engine is a Civic and one is from a drag racing car. If you wanna go fast enough that you need to use the drag car engine (at least partially), you are gonna suck down the gasoline a lot more quickly than if you only used the Civic engine. And you won't go nearly as far on a tank of gas, just as in the graph above.

Another point is that you will pay dearly for going too fast. Rate of glycolysis is nonlinear with speed. Let's say you know you can hike at 3 mph steady for 4 hrs. One time you start hiking at 4 mph for 1/2 hour, then you slow up. Think you can slow down to 2 mph for 1/2 to make up for it. NO. 4 mph takes up more than twice the glycogen as 2 mph, meaning you may have to go 2 mph for the rest of the day to save your fuel.

If you go sprint up a hill for a minute, it may cost you 10 minutes (totally making this number up) over the next few hours. When people "hit the wall", they have run out of glycogen too early b/c they are moving just a little too fast.

Taking many breaks does very little. It doesn't get the energy back. Two guys - one moving steady but slower and the other moving a bit faster but taking breaks - may end up at the summit at the same time, but the slow guy is going to have more energy left.

Ok Ok But What About Altitude?

People always mention that you need to eat more when hiking at high altitudes because you are burning off more calories. This is partially incorrect. The workload is the same, no matter the altitude. You may have some physiological changes that require more energy, but these are probably slight relative to energy used from hiking.

So what's happening? Well you should know that altitude has lower pressure and it's harder to get oxygen into the bloodstream and to the muscles. This means that if you are moving at a certain speed / workload, you are getting less of your energy from aerobic glycolysis, and more from anaerobic glycolysis!

When you are hiking the last few miles up to the summit of Mt Whitney, you are already going slow as you can because of the low pressure. Even at that speed, your body is sucking up glycogen at a high rate because too much is coming from anaerobic energy.

This is why it's important to eat a lot (especially carbs) when doing multiday treks, especially at altitude. Your body will be sapped of glycogen from altitude. And while conditioning won't affect your likely hood of getting AMS, it may help increase glycogen storage.

Are Porter's More Efficient?

2010-07-01T15:11:00.003-07:00

Link to Abstract, Embedded article below

I came across an interesting paper that was looking how and why are Himalayan porters able to move much faster than their Caucasian counterparts...outside of their superior chronic acclimation to high altitudes. Basically, they are more efficient, but why?

Short Answer:

Porters are not only better acclimated and lighter, they also move more efficiently, seemingly due to a more horizontal trunk posture which they are able to control well.

Long Discussion:

Although its the largest factor, it's not all about conditioning.

Evaluation of "performance" in hiking / climbing is often defined at least partially by how fast someone ascends a mountain (i.e. ft / hr, like ascending 4000 ft in 2 hrs). While this may be a decent way to illustrate "performance", it does not necessarily defined cardiovascular fitness, or economy of movement. Factors that may affect performance include

1. Cardiovascular conditioning
2. Altitude and level of acclimatization
3. Bodyweight and backpack weight
4. Efficiency of movement

If you do not consider how all of these parameters may vary between people, you may incorrectly attribute performance differences between people to only one. For example, if one person ascends 4000 ft in 2 hrs, and another guy in 2.5 hrs, is the former in "better shape" than the latter?

Or, was the latter hiking at a higher altitude? Was he carrying an extra 50 lbs of bodyweight or backpack weight? Or was he simply that much less efficient in movement? Someone can be in better cardiovascular shape but slower because they weight more.

In the paper below, the authors were trying to control for #1, #2, and #3 to see if there was a difference in economy (#4). Economy of movement is best defined as:

Efficiency = Power Out / Power In

In climbing, power out is defined as the energy needed to overcome gravity:

Power out = (Bodymass + Backmass) * gravity * distance / time (Watts output)

Power in is defined by the amount of energy consumed, which is related to oxygen consumption.

Power in = Oxygen consumption rate (Liters O2/time) * Constant (Energy / Liter) --> # Watts input

Power out will always be less than power in, which ratios generally around 0.2 - 0.25. That is, your body will consume 4-5 times the minimal energy needed to lift your mass a certain height. Why is effiency so low? Probably a lot of reasons, like a car there are energy losses along the way. Energy loss in heat during muscle contraction, damping of of movement, and conversion from linear (muscle) --> rotational (joints) --> linear (vertical mass movement).

Everyone is different, and the researchers found that porters' efficiencies were higher than caucasians. So aside from already moving faster because of lower bodyweight and better aclimitization, porters also are more efficient in movement! But why?

The study found that porters had better control and less variability in their trunk movement. Less variability means less energy co-contracting muscles and correcting for errors in trunk motion. In addition, it was noted that porters generally had a more forward-leaning trunk than caucasian climbers. Not mentioned in the article, but my own reasoning indicates that this trunk posture should actually be harder to control, making the results even more impressive. There may be an efficiency benefit to leaning the trunk forward, but only if one is able to control it well!

Editing GPX Files

2010-06-23T14:22:00.000-07:00

Many GPS devices come with their own mapping / editing software that may or may not be sufficient for your own analysis. Personally, I use Matlab for much of my processing b/c I have a lot of control, but you'll also have to do a bit of programming.

First, if you want to convert your file from your specific file type to .gpx (or vice versa), I suggest using GPS Babel.

For some editing / analysis, you can use Excel. Open Excel then open the .gpx file. I would open it as "read only" or "xml-source" which seems to disable the macros. From here, you can plot / analysis the columns of data, including latitude, longitude, altitude, and time. However I don't think you'll be able to save it back as a .gpx file.

The easiest way is to download the free GPX Editor. Open up a .gpx file inside, and select the specific track segment you wish to edit. While I have not checked out all the options, I know you can double click on a row and edit the information inside. Make sure you hit the "check" box or it won't save the change.

Google Earth Mapping Discussion Update

2010-06-22T09:30:00.000-07:00

Earlier this year I outlined a way to overlay topographic maps in Google Earth, and subsequently get out path information to make maps and upload to your GPS device. The main downside with this method was that Google Earth did not provide elevation data when you created a path, so you would also have to use something like GPS Visualizer to get that information.

I was tipped off by Modern Hiker that the new version of Google Earth (5.2) is out and now it provides the elevation from its digital elevation model (DEM). Now when you create a path, you can right click on it's name in the sidebar and go to "Show Elevation Profile." Something like below should open up:

If you try to save the .kml file, the elevation data won't be included, so use of the elevation is inclusive only to viewing in Google Earth. Still, this addition combined with the topo overlay offers excellent options for route planning.

Some Thoughts on Knee Loading Mechanics

2010-05-13T10:28:00.000-07:00

When hiking and doing other physical activities, our musculoskeletal system undergoes increased loading - in the muscles, tendons, cartilage, etc... Understanding how different postures / mechanics change loading may be beneficial in terms of hiking - how do you walk downhill to redistribute load in an ideal way for you?

For instance, many people end up with some knee problems from hiking downhill. There are several specific problems that could arise in the knee that are affected by different loadings, but an important one is the moment / torque --> muscular demand of the muscles crossing the knee joint. To illustrate how the magnitudes of these loads could change, we'll use a simple example of a weighted squat.

Here are three different positions where one could hold a barbell while performing a squat. A fundamental requirement of whole body movement is the balance constraint. To not lose your balance, you must keep your center of mass (CM) in a horizontal position in which you can maintain. Your CM accounts for the weighted average position of all your body segments (and the weight and position of the barbell, in this case). To remain stable, the force acting on your feet must be vertical and go directly through the CM (dashed lines in figure above).

If the force acts vertically but is in front of your CM, you will start to tip backwards. This is because you are generating a moment about your CM. Same effect if the force is behind the CM. And the CM must be aligned horizontally to be withing the horizontal range of your feet, or else you won't be able to keep the force aligned!

Given these requirements, if one changes where the barbell is positioned, this will change the overall CM location. In order to ensure the CM sits at the middle of the feet, one must change the kinematics of their segment / joint orientations, as seen in the figure above.

The consequence of this can also be seen in the figure - look at how the distance between the dashed line and middle of the knee decreases from left to right in the figures. The moment arm about the knee joint is decreasing. Given a force "F" that includes the barbell weight + bodyweight, and a moment arm "x", the moment / torque that is needed to be generated about the knee is T = F * x. As x decreases, the moment needed will decrease.

What does this imply? Well the smaller the moment demand, the less force the quadriceps muscles will have to generate. Less force will mean less contact force between the femur (thigh), patella (knee cap), and tibia (shank). This may be good, depending on your current state and injury history. On the other hand, the decrease in moment about the knee means an increase in moment about the hip.

Now there is a lot more complexity than this, but the take home message is that you can redistribute muscle and joint loading by orientation of your body segments, whether in squatting or hiking or anything else. Changes may be beneficial if you are suffering from musculoskeletal problems.

Salt Stains and Tips on Electrolyte Replenishment

2010-05-04T19:05:00.000-07:00

Here's a decent article on electrolyte loss from sweating and replacement. Of course, this can be extremely important on strenuous hikes on hot days. Especially because you'll be a little more stranded in the wilderness than in a race!

Does High Altitude Exposure Increase Energy Expenditure?

2010-04-27T20:50:00.000-07:00

There have been many claims that exposure to high altitude increases energy expenditure. While overall this is likely the case, I was interested in seeing if there was information specifically addressing 1) Is there an increase in basal metabolic rate (BMR) alone or 2) Is there also an increase in energy expenditure during exercise and 3) Are any increases actually due to the increased hypoxia, or is it something else?

I looked up on PubMed and found a 2006 review paper that investigated weight loss at altitude. Unfortunately the abstract says little - I have the actual article but I am not "allowed" to provide it (that whole copyright thing) - you can contact me for more detail if interested.

The paper in general shows that there hasn't been a whole lot of controlled studies to answer these questions, but do have some tidbits

1) One study (Nair 1971) had 2 groups with group A exposed to hypoxia alone for 3 weeks then cold & hypoxia. Group B had the reverse order. Under hypoxia alone, group A actually had a decrease in BMR after 3 weeks. After inclusion of cold temperatures, BMR increased. In group B, exposure to both hypoxia and cold increased BMR after 3 weeks. After taking away the cold, BMR stayed elevated.

The results are definitive but point to cold temperatures being the significant factor in increased BMR at altitude. Another study showed increased BMR after exposure at 4300 m for 21 days, but did not distinguish exactly what was causing the increased BMR. The review article states there is no conclusive evidence and more research is needed to see if hypoxia affects BMR.

So that address #1 and #3 (somewhat), what about #2? Well there seems to be even less controlled work done on this. The article states (and what I have believed) that work requires the same amount of oxygen at high altitudes as at sea level. However, the maximal work output (VO2max) is reduced and thus all levels of exertion are more tiring. But there doesn't seem to be any studies really showing comparative energy expenditure at altitude versus sea level, at least according to this review.

This goes back to the idea of eating high carbohydrate diet at altitude. You'll have an increased BMR (at least due to cold temperature exposure) but more importantly you'll burn relatively more glycogen at a given workload than you would at sea level. This goes back to how our aerobic energy pathways utilize fats and carbohydrates depending on intensity - the more intense, the more glycogen (carb) is used instead of fatty acids.

Ascending from 13,000 ft to 14,000 ft may not be more work than 1,000 ft to 2,000 ft, but the lack of oxygen forces the body to get more energy out of that oxygen, and therefore uses glycogen reserves more (both aerobically and anaerobically) than fat.

The article goes on to talk much about appetite suppression as being a larger factor in overall weightless at altitude.

So overall, estimation of caloric expenditure of a hike may not be affected by altitude - but a person's basal metabolic rate will likely increase causing an overall increase in expenditure. Even at the same caloric expenditure, glycogen reserves are used more and therefore a high carb diet is beneficial.

There may be pertinent research that this review article didn't address, so if you find some it would be great if you let us know.

How to Ford a River

2010-04-05T20:48:00.000-07:00

Props to the Hike Guy for linking to this trails.com post on steps & tips for properly crossing rivers of different levels.

Dehydration Good at High Altitudes?

2010-04-03T08:05:00.000-07:00

The conventional wisdom says as you ascend in altitude, you get more dehydrated, and you should drink more water / electrolytes to prevent mountain sickness.

Peter Hackett, a well known researcher in the field of altitude sickness, suggests in this interview that you actually want to be dehydrated at altitude.

There's evidence that the people who do best at altitude are dehydrated. That is the body resets the serum of molality level which has to do with the water balance. And the body, for some reason, prefers to be dry at high altitude. My own thinking is that this is good for the body because it keeps the brain a little bit drier and softer. So that if it does start to accumulate a little water or get a little swelling, it can be tolerated better.

Wow. Conventional wisdom that hikers / climbers digest elsewhere may need to be altered. I suppose it's time to read up more on this issue. Maybe I've been drinking too much water in the Sierra!

Estimating Energy Cost while Hiking

2010-03-22T20:44:00.000-07:00

It's something many people are interested in knowing. How many calories are you really burning while hiking?

In reality, highly accurate estimations are specific to the individual, but there are some basic properties to start with. So, we'll start laying at least a foundation now.

A paper from the Journal of Applied Physiology has looked at how energy expenditure is affected by the slope (grade) while walking (and running). You can read the full study with the link provided. Basically, they put people on a treadmill at different gradients and measure how much oxygen they are consuming. From that, they find an equation relating the relative work performed at a given grade relative to the work performed while walking on flat ground.

Concept: Oxygen Consumed ~ Work ~ Calories Burned

Given this relationship, if one know's how much work and oxygen they are consuming at any velocity and grade, one can estimate how many calories they are burning. The figure below (from the paper) shows how the relative work changes as a function of incline for both walking and running. The values of Cw are not intuitive, but how the numbers change relative to a 0 gradient may be. Given a certain velocity, positive grades increase energy expenditure, while slightly negative grades decrease expenditure. At about -10% grade, expenditure increases as the grade gets more negative.

Minetti et al 2002

So how well does this translate to outdoor hiking? There are plenty of other variables to consider such as terrain & altitude, but I think this will do a decent job estimating energy expenditure while going uphill. Downhill? I'm not as confident. I think the terrain will play a big part in make actual expenditure higher outdoors while hiking down steep trails.

You'll notice an equation deriving the energy relative to the treadmill grade:

(Minetti 2002)

With this equation, we can estimate the instantaneous energy expenditure at any given grade. If we have GPS data with information about the steepness as a function of distance along the trail, we can integrate and estimate the expenditure for the entire hike. Or more simply, use the average grade and distance values.

With this info, we will determine how many equivalent flat miles of walking the hike was worth. For example, I may estimate a hike up Mt Baldy (4 mile uphill, ~ 4000 ft gain) to be about the same as walking 12 flat miles (not in terms of time, but calories burned).

If we have a known quantity of energy expenditure and bodyweight for a given hike, we can make generalized estimates for other hikes and other bodyweights. For right now, the basic assumption is that calories burned is linearly related to bodyweight. So, a person weighing 100 lbs will burn 1/2 as many calories as someone weighing 200 lbs.

As I have measured my own caloric expenditure using indirect calorimetry, I use that as a basis to start with. The assumption of linear relationship between weight and calories burned will probably be improved, but we will start with that.

Also, I incorporated estimates for backpack weight, and a terrain "scaling" factor. The backpack weight inclusion will need improvement as it seems that there is a non-linear relationship between pack weight and calories burned.

So, here is the first version! Also place as a tab at the top.

Does Hiking Pole Weight Matter?

2010-03-13T15:32:00.000-08:00

People are always looking for the newest, most advanced technology in any area of interest. Hiking, of course, is included. And people love to get the lightest poles available (as long as they don't break!). But does weight matter?

One study compared hiking poles of three different weights. and found that muscle activity (electromyography) of the biceps brachii and anterior deltoid increased with increasing pole weight. The anterior deltoid assists in flexion of the shoulder (brining your upper arm from your side to in front of you horizontally) and also is needed to resist gravity and the weight of your arm. With a hiking pole with increasing weight, this muscle should increase in activation. The biceps brachii (or just your biceps) work to flex your elbow, and again will be increasingly activated as more load is placed on the hand as your arm is out in front of you.

Lightweight Leki Poles are nice, but is it worth it?

However, this study found no significant difference in energy expenditure (VO2 consumption) with increasing pole mass. Looking at the paper, they are not clear on what the actual values for VO2 intake were (regardless of whether the differences were significant), so its hard to tell if there still was possibly an increase in energy expenditure (albeit not statistically significant). I'll have to read through it further.

Another paper also somewhat looked at the effect of pole mass and did not find any significant change in energy expenditure.

So it seems that the current research is indicating that pole mass (within realistic levels as found in stores) does not make much of a difference in energy. The mass will, however, increase the loading and activation of a few muscles, although it's not clear whether these levels could be tiresome over the course of a day.

How can upper arm muscle activity increase but not energy expenditure? Well the mechanics are pretty complicated, but it may be simply that those muscles aren't consuming much energy to begin with. Or the heavier poles have some benefit in other manner (natural arm swing frequency?). It's not clear.

For those of you that use poles? What do you think? Certainly lighter poles feel better. But have you noticed an effect on performance with different pole weight?

Link to some discussions

SGMDF

Summitpost

Food / Fluid Intake & Improving Hiking Performance

2010-03-07T17:01:00.000-08:00

This article gives a nice overview of some of the things people can do to improve endurance performance right away. I am not promoting Hammer Nutrition - I'm not even sure I've ever had anything made by them - but the article is good.

When preparing for a long, strenuous trek, following such tips about hydration and proper food consumption will undoubtedly make your effort easier and make you feel better doing it.

Vertical Ascent Rate

2010-02-26T10:48:00.000-08:00

While we just looked at an example of how walking speed changes with change in trail steepness, it is also interesting to look at how vertical ascent rate (VAR) changes with trail steepness.

Of course, I think most people would generally hypothesize that VAR increases as the grade increases, since a larger % of energy will be spent on vertical movement. I would also hypothesize that above some grade (perhaps 60-70%), VAR would begin to decrease - I am thinking about loss of friction, change in terrain, and change in biomechanical efficiency - but that is simply conjecture at this point.

We will look at only one exemplar hike (Big Iron again) which is suitable because of the breadth of gradients encountered and I was attempting to hike at a constant pace. Below is a plot of VAR vs grade % (this time I multiplied by 100% so it makes more sense, like 15% grade on a treadmill).

We can confirm in this case that VAR increases as grade increases. We see a similar pattern while going downhill as well, although the vertical descent rate appears to be slightly faster at each grade.

Let's look at a magnified view of the positive region:

We see VAR increasing rapidly as grade increases from 0 to 15%. From 15% and up, the VAR still increases but at a smaller rate. The variability also decreases with increasing grade.

VAR from 0-15% could be increased nonlinearly if a person was running - as mentioned in the previous post - for me walking under 15% grade reduces energy expenditure. However, since we are discussing hiking, this sort of graph is what we generally would get.

The increase in VAR from 20 - 50 % does not seem that great. perhaps from 0.8 to 0.9 ft / s, but it is in reality a decent difference, leading to a difference in 360 ft / hr.

This data cannot really discuss what happens at really steep slopes. I thought perhaps the looseness of the terrain could possibly affect VAR around 50%, but perhaps the grade needs to be higher for any effect to be seen. But the VAR certainly does seem to be slowing down.

Of course, the absolute values here are affected by pace, altitude, terrain, weight, etc..., but a decent trend emerges. I have looked over graphs for a whole bunch of hikes and see a similar trend. In the future it would be nice to overlay different hikes, if they are controlled and say only vary in the altitude.

For trail design purposes, I'd think 20-25% grade trails would certainly lead to high enough VAR for anyone while getting a good workout if so chosen.

How is Hiking Speed Affected by Steepness? A GPS Graphical Analysis

2010-02-24T09:17:00.000-08:00

The short answer is we slow down as the trail gets steeper. Yes, I know, pretty obvious.

But how much? And what steepness / speeds are equivalent...is hiking a 10% grade fire road fast the same exertion as hiking up a 30 % grade mountain at 2 mph?

This is one of many things interesting to look at through the experimental data that a GPS device can collect. Take a look at the graph below, which shows my hiking speed versus the steepness of the trail while on a hike up Iron Mountain in the San Gabriels.

The grade is defined as (vertical distance / horizontal distance) at any given moment. Velocity in this case is defined as the horizontal velocity ('true velocity' would be in the diagonal direction - but this does not vary much from the horizontal). The measurement is really speed (velocity being direction dependent).

The left side of the graph is information about my movement downhill, and the right side information about uphill. We'll focus only on the uphill part, although it is interesting to see the symmetry created...

So over a whole hike with many samples, we get a picture of how my velocity changed as a function of the steepness of the trail. For this hike, I was going at a very strong, consistent pace, so we can assume my energy expenditure was similar at different grades. For instance, I was working equally as hard at (0.2, 3 mph) and (0.4, 2 mph).

However, notice as the grade decrease from 0.2 to 0, my velocity increases, but not that much. It reaches a limit of about 4 mph. Well we are hiking, right? So I was keeping to actually walking and not running, even though it was probably possible that I could run at those speeds.

And if I wanted to make sure that my exertion was the same at all grades, I'd have to run on the lower ones. So now I present you a similar graph for when I did a trail run in the Santa Monica Mountains. The pace I was running at was similar in exertion to the Iron mountain hike I did.

Now you can see my velocity increases a lot at the lower grades of steepness. Let's combine the two graphs.

Now we are starting to see a clearer picture. My top velocity around 0 grade is a bit above 8 mph, and it drops quickly as the grade increases. It keeps dropping quickly, but eventually the rate at which my speed decreases begins to slow. We notice that at grades above 0.2, my speed decreases, but not by as much.

Now, I want to find an equation that best relates my speed to the steepness, so I could determine that based on the information in this graph.

Such a line could be called an "isoEnergy" line. At every point on the line, I am exerting the same amount of energy. The position of this line will shift outward or inward depending on a person's fitness and the length of the hike. But given an individualized equation, any person could then estimate approximately how long a hike (and/or trail run) would take them.

For example, if a hike is 1000 ft / mile, that is about 0.19 grade and I'd be able to hike the uphill in about 3 mph. If I had a gps track from someone else, I could input the steepness at every point on the trail and determine even more accurately how long it would take.

You will also notice that if just looking at the hiking data, at grades under 0.15, there is a sort of hiking "deadspace". It is an area where I will not be working hard, unless I'm running it. But that's not hiking, and I don't like to do that on most hikes. So some time is lost.

Is this all really important? No, but maybe it justs get you thinking about this stuff. There's plenty more of this to look at too. Maybe you have some suggestions as well?

Energy Systems Part 2 - Aerobic Exercise

2010-02-21T14:05:00.000-08:00

We previously went over some basics of anaerobic exercise, now on to the aerobic portion.

3. Glycolysis - Aerobic
The burning of glycogen using oxygen can last much longer than without...but how long? Well, it's going to be directly related to how much glycogen you have stored in your muscles. So when you workout, you need to eat carbohydrates to replenish these storages. If you don't, you will feel fatigued, as your body can't produce energy at the rate you are used to. That's why you'll see people eating all sorts of sugary stuff when doing multi-hour endurance activities. Gatorade came to signficance partly due to showing that by giving carbohydrate calories to people during exercise, the participants could perform the exercise for longer.

In Hiking Terms
A main energy system to use when hiking. When you are breathing hard, you are using this pathway. Breathing hard = using a lot of oxygen! You'll use it all the time when doing moderate + hikes. The key, of course, is to make sure you don't deplete your glycogen stores before you finish the hike (or at least the hard part). This is done partly by bringing some carb-dense food, and partly by hiking at an intensity that also uses #4 below.

Training
Again very important. You want to be able to take in a lot of oxygen for your body to use. Although it seems that you are limited by your lungs when working and breathing hard, it almost always comes down to the fitness of your heart and muscles. Training at intensities that you can only do for less than 1 hour will train your heart to pump strongly, and train your muscles to process oxygen for glycolysis more efficiently.
So training to get stronger at hiking is based around switching between aerobic and anerobic glycolysis. Mixing up intensities that you can hold between 5 and 20 minutes will sufficiently tax the cardiovascular system. It will help push the AT up higher, so you can hike at a higher intensity for longer - as long as you have the glycogen reserves!

4. Fatty Acid Metabolism - Aerobic
Uses oxygen and fatty acids to produce ATP. Burning fat will not give you as much energy / time as you need for strenuous exercise, so your body uses it more at lower intensities. I will not get into the discussion about thinking this means you should exercise at a lighter intensity to burn more fat, but basically it's not true. You want to burn the most calories to lose weight.

In Hiking Terms
You'll be using this energy pathway during hiking, especially for the longer ones. Unlike aerobic glycolysis, you won't run out of fat to use for energy. You just can't go as fast when relying on it. That's why when you are planning to go far, you have to go slow enough to use a good amount of your energy from fat. You'll plan on the rest coming from carbohydrates, but you may have only 1000 - 1500 kcal of glycogen available, so plan to spread it out over a few hours!

Training
While some may argue specifically about improved ability to extract ATP from fat, this is not an important system to focus on when training. Basically, it's not intense enough. It's not pushing your heart to pump oxygen, nor pushing your muscles to use it. You'll use it when doing high-intensity intervals - in the rest portion. Otherwise, don't expect to exercise at this intensity and gain significant improvements in fitness.

Energy Systems Part 1 - Anaerobic Exercise

2010-02-18T08:28:00.000-08:00

We will start backwards. When we hike (or run) we move our limbs in desired motions and speeds. To get the desired movements, we need our muscles to contract. Muscles cannot contract without having energy available. So we need to get energy to the muscles.

Where does the energy come from, you say? Well, it depends on the energy demands of the muscle. Compare walking at 3 mph on a flat terrain to walking 3pmh on a steep trail and running 6 mph on a steep trail. Wouldn't you agree the energy demands are different? In the 6 mph case, there is a high energy demand and it is probable that this pace could not be kept up for long. High energy demand exercise is considered anaerobic exercise. This basically means that the energy for the muscles is produced without using oxygen, and that the energy supply is quite limited - only lasting for a few minutes. But because the energy can be created without oxygen, a lot of it can be produced quickly, so fast movements that last up to 3 minutes will rely on this source.

If you try to run up a 25% grade, you'll be quickly using up your anaerobic energy

While still depending on fitness level, the two 3 mph cases are more likely to utilization of aerobic energy. We can broadly classify exercise into 2 forms: 1) Anaerobic & 2) Aerobic exercise. "Aerobic" indicates that energy used for exercise requires oxygen, while anerobic exercise does not use oxygen. Now, you might be able to guess which one is going to be important in endurance exercise - aerobic. Energy derived from chemical reactions without oxygen will give you energy more rapidly - but cannot last very long.

We can break down energy stores to 4 sources. We'll look at the 2 anaerobic sources in this post.

1. ATP-CP - Anaerobic

ATP-CP uses creatine phosphate to produce energy (ATP). It is known as the "immediate" energy source, and will basically depleted after 6-10 seconds of the highest energy exertion. So activities such as sprinting 100 m will use mostly this energy pathway. You'll notice in an all-out effort that you quickly cannot go as fast as when you started. This is because after 10 seconds, you run out of this energy and have to utilize the other energy pathways which cannot give as high of an energy output.

In Hiking Terms

Ideally, you will not be focusing on this energy system when hiking, but it can happen. Take, for instance, a really steep, but short climb that you want to ascend as fast as possible. You may push as hard as possible to get to the top, and you will be using ATP-CP to do it. But obviously, you cannot do that for long, and if you are doing a long hike, you wouldn't want to try that and then wear yourself out.

Training

This energy system will only be utilized during interval training. Intervals from 5 seconds to 5 minutes will at least partially tap the ATP-CP system, and for hiking you would only want to focus on the longer duration intervals. As you will be hiking for several hours, you will want to train with longer intervals that also heavily utilize oxygen. More on this later.

2. Glycolysis - Anaerobic

Glycolysis is the generic term for the breaking down of glycogen. Glycogen is basically a storage of carbohydrates in the muscles. It can be broken anaerobically (without oxygen) or aerobically. Anerobically, the process cannot last as long as lactic acid is produced and glycogen is consumed. This acid is the burning sensation you feel in muscles when doing high intensity exercise...and so the fact that this energy lasts from 30 seconds to a few minutes makes sense.

The rate of ATP production is high, behind ATP-CP. However, the efficiency is low, with

1 molecule glucose --> 2 ATP

In comparison to the yield from aerobic glycolysis (more on this later), it's paltry. So it's fast, but inefficient.

Glucose molecule

In Hiking Terms

An important system to consider when hiking - if only because when doing steady state hiking, its something you want to avoid. If you are planning on doing several hours of hiking, you do not want to feel the burn in your muscles at the beginning - unless you are doing it for training. You will be able to go further if avoiding this intensity of exercise (you can only do for a few minutes). So when the hikes get steep, trying to keep the same pace will require more energy for your muscles, and they'll start using anaerobic glycolysis. To avoid it, slow your pace down!

Training

Very important. One determinant of cardiovascular fitness is your aerobic/anaerobic threshold (AT). The level of intensity at the AT is when the body can flush out the lactate as quickly as it is created. At higher intensity, the body cannot remove it quickly enough. By training above this threshold, you can train your body to better flush out the lactate, and increase the intensity at which AT occurs. (This is not to say that lactate is the cause of fatigue, but it is correlated).

Bouts of exercise from 30 seconds to 10 minutes will tax the anaerobic glycolysis system. Training in this range will be an important part to improve hiking performance, more on this later.

This is a basic overview of the anaerobic systems. Next up will be aerobic energy.

Google Earth Topo Overlay - A Mapping Discussion

2010-02-11T15:49:00.000-08:00

One of the 10 essentials is a map (and a GPS is nice too), especially if you are going into a new area, or even better (worse) going off maintained trails to do some fun exploration.

When this happens, often times available maps (i.e. USGS topo, Tom Harrison maps) are not sufficient because the trail / area you planning on using isn't there.

So some people like to use mapping software like National Geographic TOPO! or Garmin Mapsource to make maps and wapoints to print out and download to a GPS.

Well now I think there's a better, if not somewhat more tedious option.

You can now overlay USGS topo maps in Google Earth! The main benefit to me is the ability to create paths that rely on a combination of satellite imagery and topo maps. There are many instances where trails on topos aren't totally reliable, and if you are planning on going off trail, the satellite imagery is a big plus.

This stuff comes out from over at the Google Earth Library, who have created KML files not only standard 24K topos (USGS Topo KML), but also for historical topo maps! Historical Topo Maps KML

1) Save the kml files to your computer.

2) Open Google Earth, and open up the topo kml file. When opened make sure the button is marked on.

Now you'll see something like this:

3) Find the topo you want, and you'll click on the name centered in the middle, and this blue screen should pop up:

Now after clicking on "view map", the topo should load as such:

Now, find the text labeling the map in the Places panel on the left side. Click on this, then go down to the horizontal scroll beneath the panel. You can use this to adjust the opacity of the topo overlay, like so;

You could print this out, or, more likely, you'd like to add a path using the Path icon near the top. Make sure to increase the width to make it clear on the display.

4) Add points and make a path based on the topo / satellite data. When you're done, you could simply print this out, or continue on and export the data. Right click on your path in the Places panel, and save it as a .kml file.

Now, one downside with using Google Earth is that they will not allow access to the digital elevation model (DEM) they are using, so you will get out the latitude/longitude coordinates, but not the altitude. If you want to look at the elevation profile, you'll have to use other software. You could use TOPO! or Mapsource software perhaps. However, also take a look at GPS Visualizer.

5) Here you can click on the "Google Earth KML" option. Make sure to check on the "Add DEM elevation data". Select to import the kml file you created from Google Earth.

After processing, you'll be able to save the .kml file that know includes elevation data.

You can also view the elevation profile (and many other options) using other choices on the GPS Visualizer website.

But let's say you now want to import this file onto your GPS device. If your software does not allow import of .kml files, you'll want to check out the very handy GPS Babel.

With the GUI interface, you can choose from many input / output options to convert GPS files. For instance, I chose to convert my .kml file to a .gpx file:

Now I import this file into my Garmin Mapsource software, where I can upload the track to my device as well as view the elevation profile.

Lastly, if you want to embed a topo on a website, you can do so using a few Google Earth embedding websites. One is the Google Earth Embed. Another which I use below is the TakItWithMe site.

The main step is determining the URL for the topo file. Back in Google Earth, check the numbers/letters that correspond to your topo file. For instance, my topo was called "o34118c1". Notice how the URL is created based on this info:

http://www.topomaparchive.com/maps/Topos_Current/34118/o34118c1.kmz

Add this in, you can create an embedded map like this:

These are just some examples of what can be done. I appreciate if anyone provides other suggestions.

Hyperventilation - Does it do any good?

2010-02-04T10:07:00.000-08:00

There has been some disagreement that hyperventilating helps absorb more oxygen into the blood when at high altitudes.

Does it?

Yes

Here's why
You can read a good explanation of it here. This is a great website for an overview of the physiology of exercise at altitude.

The basic idea is that, when you hyperventilate, you reduce the partial pressure of CO2 (carbon dioxide) in the blood. This allows more oxygen to diffuse into the blood as there is less "resistance."

But don't take it from me, I'm just someone who tries to digest this science. Here's a paragraph I'm taking from a respiratory physiology textbook from a course I took some years ago, called Respiratory Physiology, The Essentials by Dr. John West.

Hyperventilation

The most important feature of acclimatization to high altitude is hyperventilation. Its physiological value can be seen by considering the alveolar gas equation for a climber on the summit of Mount Everest. If the climber's alveolar PCO2 were 40 and respiratory exchange ratio 1, the climber's alveolar PO2 would be 43 - (40/1) = 3 mm Hg! However, by increasing the climber's ventilation fivefold, and thus reducing the climber's PCO2 to 8 mm Hg (see p. 16), the climber can raise his or her alveolar PO2 to 43 - 8 = 35 mm Hg. Typically, the arterial PCO2 in permanent residents at 4600 m (15,000 ft) is about 33 mm Hg.

The point is, increasing ventilation (hyperventilating) can significantly increase the concentration of oxygen in the blood. This is why we naturally hyperventilate when going to altitude.

This is also why some high altitude residents chronically hyperventilate.

Understanding Altitude Sickness

2010-02-03T07:32:00.000-08:00

I originally posted this on the socalhikes blog but this is a more appropriate home for it.

Background: You want to hike Mt. Whitney (~ 14,500 ft), the tallest peak in the contiguous United States. Or you may want to ascend other high peaks in the Sierras, or elsewhere.

Perception: This is the hardest hike you will do, therefore you need to train for it. I have heard this many times.

Reality: The hike certainly is a biggie (~ 22 - 24 miles, 6500 ft gain), but there are many other hikes that have more stringent cardiovascular conditioning demands. In fact, the main trail up to Mt. Whitney is not very steep.

What makes Mt. Whitney difficult is the altitude and the low pressure of oxygen.

Problem: Cardiovascular training does not improve a person's ability to handle low altitude, so how else can we adapt?

Discussion:

First, we need to understand what exactly is the problem with hiking up to high altitudes. A good discussion of these problems can be found here. The problem is that at increasing altitudes, the atmospheric pressure decreases. Atmospheric pressure is used to get air into our lungs and then into our blood. There is a pressure gradient, with lower pressure in the blood than the lungs, and lower in the lungs than in the air.

As the air pressure decreases, less oxygen will go into the lungs. Normally, we have certain breathing patterns that are based on having certain oxygen pressure in the air. If there is now less oxygen but we breathe with the same rate, we will not get enough oxygen into our body to use for energy. This is called hypoxia.

Less oxygen means less energy, and if nothing else changes, we will have to move slower. Luckily, the body realizes that we need more oxygen, and begins to breathe deeper and more frequently. This allows for more oxygen to get to the blood. Sounds good right? The problem is, this phenomenon is also known as hyperventilation and has its own side effects including making our blood alkaline (opposite of acidic) and makes us lightheaded and gives us tingling sensations.

So if we start hiking up to high altitudes, our body will start hyperventilating, but only so much so quickly. Lots of hyperventilization will worsen those side effects, which we don't want. But if we don't breath more, we won't get enough oxygen and will have to slow down. And lead to altitude sickness.

How do we prevent this crap from occurring? Well, it is known that fitness level does not affect chances of getting altitude sickness. This is why the common thought of "training for Whitney" is flawed as it won't tackle the real problems of dealing with altitude. In theory, my conditioning is such that I could ascend Whitney in 3 hours if it was at low elevations, but I took 6 and still felt like crap. Certainly I wasn't challenged in the normal conditioning sense.

The time proven way to prevent it is to only ascend 1000 ft a day...ha! This gives you time to acclimate - time to let the body get used to hyperventilation. But there is obviously a large elephant standing in the room, no one wants to ascend only 1,000 ft a day on a hike, it would just take too long. But that is the best way to avoid issues with altitude (and enjoy nature).

How else? Some people take a drug known as diamox, which basically works by making your blood more acidic and therefore stimulates hyperventilation to balance the blood pH. So this lets you hyperventilate without such strong side effects of hyperventilation, and therefore allows you to take in more oxygen.

But who wants to take drugs? Shouldn't there be a more natural way to adapt and 'train' for high altitude hiking? I think so. It is of my opinion that it would make sense to practice hyperventilating for several days before the big hike. This allows for the body to "acclimate" to the change in pH in the blood by adjusting how much CO2 and bicarbonate it allows in the blood. By the time you really need to hyperventilate, your body will be able to do so with less side effects.

This seems somewhat odd but basically this is what short term acclimatization is...getting used to hyperventilating. You can get used to hyperventilating at altitude (multi-day excursions with gradual increases in altitude) or consciously force yourself to get used to it. You won't have the hypoxia to stimulate the hyperventilation, so you'd have to do it yourself.

One of these choices should be made, otherwise you may come down with some serious acute mountain sickness (AMS). Throwing up on the top of Mt. Whitney (me) is not a good sign!

Keep in mind, hydration and consumption of carbohydrates are also important in helping your hiking performance at altitude. High altitudes suck even more water out of us, so we need to drink even more than normal. But this doesn't mean hydration will do anything to change the hypoxia/hyperventilation issue; it just means that dehydration due to altitude will make you feel even crappier - lethargic, headaches, etc...

Carbohydrates are needed because when there is less oxygen, our bodies will uses glycolysis (burning of carbohydrate storages) for energy. If we run out of those storages, we will move slower and have less energy. Not good!

Hopefully these thoughts provide some tips and thought provocation on how to deal with hiking at altitude. I have looked over journal articles and other sites to educate on this, but certainly do not have the issue down pat. Please let me know your thoughts.

Zé

Energy Storage for Long Hikes

2010-01-24T09:31:00.000-08:00

I'll probably repeatedly go over this topic. Right now I'm going to repost a discussion I added to this thread.

For nutrition, the general trend to follow is, the harder and longer you are hiking, the more simple carbs you need to be eating. This goes for any endurance activity.

The higher the intensity, the larger % you are burning energy from your muscle glycogen stores. When these run out, you will hit the "wall" as well known in marathon runs for example. You simply have to slow down when burning energy from fat.

So the key is to stop those glycogen reserves from running out. How do we do this? Carbs. Simple carbs. Sugar. Bread. These substances (foods with high Glycemic Index ratings) are the best for the same reason they are looked down upon when eating while sedentary: They will be absorbed into the blood stream very quickly.

Carbs with fiber take longer to breakdown (and may cause stomach issues), and fat and protein have to go through other chemical reactions before getting into form for usable energy.

Obviously, I'm talking about extreme case here. But since this thread was based on the idea of a "death march", trying such a hike would certainly need to follow this mantra. I think that's where AlanK's classic "thank god for GU" came from while doing some very strenuous hike. GU is all simple sugar. Cyclists, marathoners, etc... consume this sort of thing during races. Not fat and protein, or even carbs with a lot of fiber.

When I learned how to apply this, I was able to work out very intensely 4 days a week, with my hikes considered a "moderate" workout. 2 rest days, and I don't fatigue, because I make sure I recover properly by eating carbs after working out.

That said, I don't really do this on hikes. I mix a sandwich, jerky, cliff bar, trail mix, etc... (things I like!). I can go 6000 ft without eating and not be affected.

But when I did cactus to clouds (~11000 ft gain), I ate a decent amount during the hike, but not a lot of carbs, and I started 'hitting the wall' the last 1000 ft. In that case, it's good to have the knowledge that to be successful with those extreme hikes, carry a few French baguettes with you!

VO2 Max Values - Applicable to Hiking?

2010-01-24T09:20:00.000-08:00

Necessary for hiking? Not so much. But one way to test cardiovascular strength is the VO2 "Max" test.

VO2 stands for volume of oxygen consumed, and is generally measured in liters per minute (L/min) and also scaled for different bodyweights (mL/min/kg). That is, the amount of oxygen that your heart can pump to your muscles. One can say that the larger the value, the better cardiovascular shape you are in, as your heart can pump more oxygen and so you can perform more work during exercise (move faster).

The test generally lasts from 10 - 15 minutes, and works by increasing the workload each minute. In my case, the grade was set at 14%, and the speed was increased 0.5 mph each minute until failure. I think I failed at about 7 - 7.5 mph. The clip only shows the end of the test.

There are plenty of specifics one could talk about in regards to exercise performance - such as the applicability of such a test versus a lactate threshold test, which I will discuss in the future. Just keep in mind that getting a high maximum output does not mean that you can sustain a high level for a long period of time. That is a more important, and stronger indicator your endurance capacity.

How it Relates to Hiking:

VO2 max is tested a lot in runners, cyclists, cross-country skiers...but hikers may encounter similar endurance tasks. A nonstop effort of Iron Mountain can be quicker if you can pump more oxygen. Or, for a given pace, it will feel easier. More on training for this sort of thing later.

Final stats

Max VO2 (L/min): 5.4
(ml/kg/min): 64
Max heartrate: 194

Don't try to max out while hiking!