Body Fat and Running Performance

A runner’s body fat level has an undeniable and most direct impact on running performance. Due to the direct upward motion against gravity that occurs during the push off phase as well as the support of weight required with every stride, running is likely the sport that is most significantly impacted by the athlete carrying around extra weight.

Obviously, for a long list of basic health and metabolic reasons lean muscle mass is far and away preferred over body fat, but when it comes to running and long distance e running in particular, carrying around any extra weight will have a detrimental impact on running performance. Sure most elite endurance athletes take on a more emaciated look, but consider also how many local age groupers or even good recreational endurance athletes you’ve seen who are not quite lean. The answer is very few!

Ok so while we recognize that a runner’s body fat can certainly make running feel harder, is it possible to quantify exactly how much harder? There was a very interesting study that focussed on the effect of weight on running performance. During a 12 minute time trial, results revealed that adding 5 pounds of body weight to a runner caused a performance decline of 5%. To put that into perspective, for a 5k race this would be the difference between a 20 and 21 minute performance. While this may not seem like much to some, to others 1 minute for a 5k can mean the world when you’re trying to break a time barrier. If there is such a decline over short distances, what about the cumulative effects of extra weight over the course of a marathon?

Think about how much your weight fluctuates in a given year. The great news about these findings is despite age, gender or genetics there is still a significant part of our running performance that is well within our control! Regarding body composition, it’s a runner’s body fat, rather than bone or lean muscle mass that will decline as a result of intelligent nutrition and training .

What’s a Healthy Runner’s Body Fat Measurement?

We are all truly individuals with a unique brain, DNA not to mention training and racing experiences so any proposed fixed measurement of a runner’s body fat would be theoretically impossible to present.

Having said this, several sources show that an average of 5% or 6% is a healthy for males 39 and under and slightly over 10% for masters and up. For female runners, the numbers are a bit higher with an average body fat measurement of 15.5% for 39 and under and closer to 20% if over 40.

In his recent book Racing Weight, Matt Fitzgerald makes a few excellent points about individuality and optimal race weight. He surmises that probably the best way to determine your ideal race weight is by measuring your body weight and composition when you have actually arrived at what you consider to be your ‘peak’ fitness. What about those of us who know we’re not in peak shape but certainly aspire to be through proper training and nutrition ? He states that a runner’s body fat and total ‘ideal’ weight is that weight which “…he or she can attain without overtraining or consuming too little energy to support optimal running performance and recovery”.

In summary, a runner’s body fat measurement does have a significant influence on running performance and the loss of that unwanted body fat can be effectively achieved through the execution of consistent running training and nutrition.



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