Friday, February 4, 2011

Optimal Hiking Grade - A 50 Hike GPS Analysis

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:

Tuesday, January 18, 2011

Walking Mechanics Part 1: Center of Mass Control

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.

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.