Saturday, December 11, 2010

Salt and Cramp Tips

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).

Monday, September 27, 2010

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

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:

Sunday, August 29, 2010

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

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.


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.

Thursday, July 1, 2010

Are Porter's More Efficient?

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?

Wednesday, June 23, 2010

Editing GPX Files

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.

Tuesday, June 22, 2010

Google Earth Mapping Discussion Update

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.

Thursday, May 13, 2010

Some Thoughts on Knee Loading Mechanics

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.

Tuesday, May 4, 2010

Salt Stains and Tips on Electrolyte Replenishment

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!

Tuesday, April 27, 2010

Does High Altitude Exposure Increase Energy Expenditure?

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.

Monday, April 5, 2010

How to Ford a River

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

Saturday, April 3, 2010

Dehydration Good at High Altitudes?

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!

Monday, March 22, 2010

Estimating Energy Cost while Hiking

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

Saturday, March 13, 2010

Does Hiking Pole Weight Matter?

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?

Sunday, March 7, 2010

Food / Fluid Intake & Improving Hiking Performance

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.

Friday, February 26, 2010

Vertical Ascent Rate

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).

Wednesday, February 24, 2010

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

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 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.

Sunday, February 21, 2010

Energy Systems Part 2 - Aerobic Exercise

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.

Thursday, February 18, 2010

Energy Systems Part 1 - Anaerobic Exercise

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

Thursday, February 11, 2010

Google Earth Topo Overlay - A Mapping Discussion

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.

Thursday, February 4, 2010

Hyperventilation - Does it do any good?

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

Does it?


Here's why

Wednesday, February 3, 2010

Understanding Altitude Sickness

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?

Sunday, January 24, 2010

Energy Storage for Long Hikes

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.

VO2 Max Values - Applicable to Hiking?

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