Matt Metzgar

Sprinting, Rest Periods, and Weight Loss II

Continuing from my last post, it appears that longer rest periods between sprints burns more total calories compared to short rest periods (for the same number of sprints). 

The "Run Now, Pay Later" paper I cited also shows how the evolutionary function of the longer rest periods is to increase endurance.  With longer rest periods between high-intensity efforts, an organism can continue to cover more distance chasing after prey.  With shorter rest periods, an organism eventually exhausts itself and is unable to continue. 

For example, how long can a person perform a 20 second sprint, followed by a 10 second rest (the Tabata protocol) continually?  Not too long, just a few minutes.  Yet how long can a person sprint 20 seconds, rest a few minutes, and then continue?  A fairly long time - hours most likely.  And this longer pursuit will end up burning more total calories than a quick workout with short rest periods.

In summary, it appears that short, high-intensity efforts with long rest periods is very "costly" to an organism; that is, it's very expense metabolically because it burns many calories.  If a person is trying to lose fat, then this type of protocol should be the best choice due to the large energy expenditure.

Sprinting, Rest Periods, and Weight Loss

I have been digging deep into lots of sprinting and interval training studies, and found some neat things.  First, you can divide sprinting-type activities into three general categories:

1. Aerobic Interval Training
2. Anaerobic Interval Training
3. Sprint Training

Aerobic interval training usually consists of longer intervals (2 min or more), and can be used to improve performance in distance events like a 5k race.  Anaerobic interval training deals with shorter intervals and is more applicable to stop-and-go events like basketball or football.  Sprint training consists of high-intensity sprints with long rest periods to recharge the muscles.

None of these types of training is inherently "better" than the others.  They all can be used to improve performance in the appropriate events.  But my interest is, which of these protocols is better for fat loss?

The first step is to look at this from an evolutionary perspective.  Hunter-gatherers' physical activities were directed towards acquiring food.  They did not "exercise" in the traditional sense - they were chasing after game (or occasionally being chased by it!).  Hence, I was curious as to why hunter-gatherers (or other animals) would engage in something resembling "interval training".

I found some answers in this fascinating paper, "Metabolic Implications of a "Run Now, Pay Later" Strategy in Lizards".  The paper begins by pointing out that the major energy expenditure with short, high-intensity efforts is in the calories burned after the exercise.  The scientific name for this is "excess post-exercise oxygen consumption", or EPOC for short.

The paper then compares the total energy expenditure between short sprints when the rest periods are short or long.  The authors find that there is a "metabolic savings" (less energy expenditure) when the pauses between the efforts are short.

In other words, let's say a person was going to perform 4 high-intensity, 20 second sprints.  What would be the cheapest way metabolically to do this?  The answer is to do them with little rest in between.  This is because the longer the rest periods, the more calories are burned in EPOC while resting between sprints.  If a person did them with only ten seconds rest between the sprints, the whole workout would be over in 2 minutes.  Yet if a person put 10 minutes between each sprint, the person would get the full calorie afterburn or EPOC for each sprint.  With both workouts you still get the after-workout calorie burn, but with the longer rest periods you also burn more calories during the workout.

Interval Training & Weight Loss II

Here's a nice LA Times article on how people are using sprint or interval training to lose weight.

Interval Training & Weight Loss

I came across this new report that investigates a unique protocol for fat loss.  Researchers had two groups of overweight women perform different cycling routines.  The first group cycled for 40 minutes at a regular, continuous pace 3 times per week.  The other group performed a 20 minute workout (also three times per week), that consisted of 8 seconds of cycle sprinting, followed by 12 seconds of cycling lightly.  Subjects kept repeating this pattern for the full 20 minutes.

The researchers reported that the interval training group lost 3 times as much fat as the regular group.  It does not say how much weight was lost, but this is still a big difference across groups. 

I am trying to get more details on this study, but in the meantime it is very thought-provoking.

Weight Loss Success Stories

I came across this MSN site the other day that chronicles weight loss success stories.  Some of the stories are truly inspiring - people in very bad condition turned things around and got in shape.

A few people chose surgery as a means to lose weight.  This is, in my opinion, a very dangerous and misinformed choice.  The other success stories show that the old standbys, diet and exercise, are powerful enough to lose almost any amount of weight.

The Few, The Proud, The Exercisers

Whenever I go out to exercise, I am amazed at the number of people who are not out doing the same.  Earlier today, I went out to do some sprints.  It's decent weather today, the sun is shining and it's not too cold.  But walking to my local park, the neighborhood looked like a ghost town.

And once I got to the park (around noon), it was completely empty.  There's tennis courts, a playground, and a grass field, and I was the only one there.  This doesn't seem to be unusual either, as I've gone out at different times and I still see very few people.

Are exercisers a dying breed?  I hope not.  When I was a kid, it seemed like there was more people out and about, staying active.  Maybe my memory isn't accurate on this, I'm not sure.  I'm betting over the last twenty years that hours that were previously spent in physical activity by many people are now being replaced by tv/computer time.

I'm not sure what can reverse this trend, but I hope things do change.

Continuous vs Intermittent Walking

One other thing I've noticed about walking is that continuous walking is more beneficial for me than intermittent walking - especially for fat loss.

You would think that "on paper", the calories burned during 60 minutes of walking is the same as two bouts of 30 minutes walking.  But the two protocols do seem to have a different effect on the body, at least for me. 

Some people say that you start burning more fat after 20 minutes of exercise, but I'm not sure I buy that.  Regardless of the mechanism, I believe that continuous walking is better for fat loss than intermittent walking.  Research suggests this is true - this study shows that continuous walking does indeed burn more total calories than intermittent walking.

Soy

I'm seeing more soy-based products in the marketplace.  In my opinion, this is an unfortunate event.  From an evolutionary viewpoint, soybeans are legumes(beans) and were not part of the diets of hunter-gatherers.

The clues that soy is unhealthy are everywhere.  There's suggestive evidence in animal studies that soy consumed during infancy has effects on puberty development and adult hormone levels.  There's also evidence soy can harm the reproductive system in animals. 

As for research with humans, here's a paper showing that midlife tofu/soy consumption can lead to "brain aging".  Some also think that women consuming soy are reducing their odds of becoming pregnant.

There are other sides to this issue.  Soy may help slow prostate cancer - but this is primarily because it acts like estrogen in men and reduces testosterone levels.

The medical research on soy and its dangers is just beginning.  In the coming years, I predict researchers will show that soy is detrimental to men, women, and especially infants.  But why wait until all the research is in?  The eating practices of hunter-gatherers show us the diet we are meant for.  Soy was not a part of their diet, and it shouldn't be a part of yours.

Green Grass

Plush, green lawns are valued by many people.  Even here in the desert, homeowners struggle to keep small lawns of green grass watered and healthy.  Businesses have caught on too, as lawn fertilizers all promise their product will lead to soft, green grass.

But why do we care so much about green lawns?  The first reason is that we are "wired" for the geography of the African savannah.  Scientists call this "biophilia", and the theory suggests that we prefer the landscape under which humans evolved: rolling hills, grass, an occassional creek or stream, and scattered trees.  If you go to the zoo, many zoos try to recreate this environment for creatures of African descent, such as the giraffe or lion.

The second reason comes from a book I'm reading titled, "The Old Way".  It documents the lifestyle of one of the last "true" hunter-gatherer tribes in Africa.  The book states that green grass was somewhat limited, being produced by either an unseasonal rainstorm or where a wildfire had burned off the dry grass.  The antelopes there fed off of grass, and preferred the green grass.  Hunter-gatherers knew this, and hence were always alert to the presence of green grass.  Green grass meant animals would be coming, and that meant hunting opportunities for the tribe.

It's likely then that humans' preference for green grass was built-in over millions of years of evolution.  Nowadays, people like green grass but have no idea why - it just feels good to have and look at.  This is just one of the many mechanisms that guided our hunter-gatherer ancestors and still guides us today in a much different environment.

What Makes A Good Sprinter?

As I've been looking more into sprinting lately, I've wondered what variables contribute to a fast sprint performance.  Obviously, there is a genetic component involved - no one can just "train" themselves to Olympic level speed.  But certainly there's room for improvement, and I was curious as to what factors are important.

The first thing I found involved the strength part of the equation.  This study shows that squat strength is highly correlated to sprint speed and also vertical jump height.  Therefore, improving strength in the squat should improve a person's sprinting time.

Another piece to the puzzle is power output.  This study showed that athletes performance in the jump-squat (with weights added) correlated very substantially to sprint time.  I had assumed that the power output was important as well as the strength portion, since in a sprint a person has to apply force very quickly (power).  The jump-squat is a good measure of power output, since it tests the ability to move weight quickly.

There are other factors involved in improving sprint performance, but it appears that improving squat strength and power are a good start.