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Tall vs. Short Runners

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8/22/05

Gotta disagree with some comments made in this thread.

 

A few posters have implied that taller runners inherently have a longer stride length. And, as a result, if two runners have the same stride rate, the taller one should be faster because of this naturally longer stride length. Neither premise is true. The determination of stride length simply is not that simple.

 

Although leg length, which is largely determined by height, is a factor that does affect stride length, it is a relatively minor one. Stride length is primarily determined by rear leg drive and range of motion. The former (drive) is completely independent of leg length (height) and the latter (range) is only very slightly influenced by leg length....do the geometrical math.

 

Another comment made by a poster was, "The way one generally improves in distance running is by increasing turnover NOT by increasing stride length." Actually, just the opposite is the case. By far, most progress made by runners comes from stride length improvement, not a faster stride rate.

 

According to Bob Glover's book, "The Competitive Runner's Handbook", a study conducted by Peter Cavanaugh, Ph.D. and director of Penn State University's Center for Locomotion Studies, shows that the stride rate of the average runner is about 5-10% slower than that of elites. But, the "average" marathoner is about 100% slower than elites (4:15ish vs. 2:10ish). So, what comprises the other 90-95% difference between them? Obviously, it is stride length.

 

Of course, the average runner cannot hope to catch up to the elites....except in their dreams. ;) However, Dr. Cavanaugh's study indicates that the average runner can only hope to gain 5-10% by increasing his or her stride rate to that of elites. Thus, the "average" marathoner could hope to improve from about 4:15 to about 3:55-4:05 and the 50-minute 10k runner could look forward to improving to 45-48 minutes. Most runners hope for, and many achieve, much more improvement than that. And, biomechanically, most of it comes from stride length increase, not stride rate increase.

 

The following is what a few "experts" say about stride rate vs. stride length improvement.

 

Tim Noakes, MD, in "Lore of Running"....”With training, runners increase the length of their strides and reduce their stride frequency. Some researchers believe this optimizes running efficiency because increasing stride length is more economical than increasing stride rate."

 

Martin and Coe in "Better Training for Distance Runners"....”Both stride frequency and stride length increase as we run faster, with stride length increasing more than stride frequency."

 

Bob Glover in "The Competitive Runner's Handbook"....”As you run faster, stride rate increases slightly; stride length increases even more." and "Quicker strides are better, but not as important as longer, but controlled, strides."

 

The same poster who commented that runners improve by increasing stride rate instead of length also said"....longer strides are less efficient, and therefore, efficiency (stride rate increase, in his opinion) trumps stride length in long distance running." The above quote from Noakes belies that opinion. As further anecdotal evidence of this, I offer the following observation:

 

Shortly after participating in an extensive discussion on the RWOL Beginner's Forum in 1998 concerning stride mechanics, particularly the "need" to consciously increase stride rate to 180, I watched the NYC Marathon live on TV with a specific objective of paying attention to the elites' stride mechanics. The leaders couldn't have cooperated better. The three leading runners ran abreast, literally shoulder to shoulder, for 10 miles from the half way point to mile 23. They were John Kagwe of Kenya, Joseph Chebet of Kenya, and Bayo Zebedayo of Tanzania. There was plenty of opportunity to analyze their stride mechanics.

 

Chebet and Zebedayo, who are about the same height (I don't know how tall), ran in lock step for the entire 10 miles. Their footfalls were precisely synchronized mile after mile. They varied only when going though aid stations. I counted their stride rate several times and it was exactly 180 every time. Kagwe's stride rate was very noticeably slower. His footplant coincided with that of the other two every 17 strides. He was taking 16 strides for every 17 of theirs. That's a 5.88% difference. Thus, he had a stride rate of only 169.4 and a correspondingly longer stride length....and he was a few inches shorter than the other two!

 

They finished 1-2-3 within 6 seconds of each other. Guess which one pulled ahead when the pack separated at mile 23 and went on to finish first? Yep, you are right. Kagwe, the shorter guy with the longer stride and slower stride rate, won in 2:08:45. I think it stands today as the 7th fastest NYCM ever run.....and he also ran one of the 6 faster ones (2:08:12) in 1997! I'm not suggesting that he won because he had a slower stride rate, but that the combination of a slower stride rate....enough slower than 180 that it would concern many runners and prompt them to work on increasing it....and longer stride was most efficient for him and didn't handicap him.

 

Except for the previous anecdote, none of my post so far addresses the primary subject of this thread. All other factors being equal, is a taller long distance runner generally at a disadvantage? I think the answer is yes, with exceptions, obviously. Notwithstanding the above anecdote, my reasons have nothing to do with running mechanics, but with running economy, which is how efficiently one uses oxygen at a given pace. Stated another way, running efficiency is the percentage of aerobic capacity (VO2max) that one utilizes to run a given pace. As Noakes says, "....the best athletes are usually the most efficient."

 

I think that shorter runners have an inherent advantage in running efficiency for one primary reason....body mass. The greater body mass that taller runners generally have results in more weight and heat production than their shorter compatriots.

 

Martin and Coe say that, "A survey of 1500 New York City marathoners suggested that as height increases linearly, body weight increases exponentially to the 2.5 power. Thus, if runner A is 66 in. tall (5'6") and runner B is 72.6 in. (6'1/2")....a 1.1-fold difference....runner B's expected body weight(156 lbs) would be 1.3 times that of runner A (120 lbs)." The greater weight requires that taller runners do more work to move their body mass a given distance. That takes more energy. Thus, they cannot run as far, as fast as shorter runners before running low on fuel and fatiguing.

 

Additionally, the greater work spent to move their larger body mass results in the generation of more heat which has to be dissipated. This relates to the comment that one poster made in reference to Noakes' book, ".... additional height is a negative because of a lesser efficiency of heat dissipation." As a 6'1" runner, I think that is very valid. ;)

 

The dissipation of heat requires that blood be diverted from the primary tasks of transporting oxygen from the lungs, glycogen stored in the liver, and glucose and electrolytes from the stomach (gel and/or sports drink intake) to muscles to be used to burn fuel for energy to the task of transporting heat from the muscles to one's skin where it can be dissipated into the air via a process called convection. The more heat generated, the greater the demand for blood to dissipate it and the less blood available to provide oxygen and fuel to the muscles to be converted to energy. That's known as reduced running efficiency, which results in a slower race pace.

 

This is a very long winded way of saying that I agree with jvalentine's original premise that taller runners are generally at a disadvantage because of weight (body mass). And I think that running mechanics have little to do with the subject one way or the other. OTOH, I also agree with another poster's observation that a 3-foot tall runner will never win the Oly Marathon or set a world record....and neither will an 8-foot tall runner. ;)

 

Jim2