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I would like to know why all Olympic sprinters have muscular arms. They probably have muscular arms to help them sprint, but the reason is unclear. These are the two paradoxes I cannot fathom:

  • Heavy arms increases the force the legs have to supply to move the body. So it seems big arms will slow down a sprinter.
  • The legs are stressed far more than the arms when sprinting, so it is common sense that legs would grow from training. However, the arms only swing against the air, so how are they stressed enough to grow?

Below is an example of how big Olympic sprinters' arms are.

enter image description here

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Found this interesting… – Manoochehr Aug 11 '12 at 8:19
They do use powerful swings of their arms to propel themselves forward. And they probably have a ridiculously low body fat percentage, which makes any muscles they have look very accentuated – Ivo Flipse Aug 11 '12 at 12:15
Seems like the resistance training is mostly focused on larger muscle groups, see – FredrikD Aug 11 '12 at 13:27
I think it's incorrect to assume their arms are growing simply by sprinting. – Dave Newton Aug 14 '12 at 0:27
up vote 18 down vote accepted

The main role of the arms in sprinting is to stabilize the torso and provide drive forward, especially in the start (Which is critical in 100/200m races).

This stabilization allows power to be transferred through the center of mass in an efficient fashion. Since you've got to be able to oppose a significant driving force from the hips and legs, you need the strength in the arms to do so, as well as in the abdomen, lats, etc.

There is this writeup, Sprinting Mechanics that also suggests that the arm swing doesn't necessarily contribute to horizontal motion, but contributes to the vertical drive component. It also cites a couple of studies that confirm the role of the arms in stabilization (Hinrichs et al., 1987; Mann & Hermann, 1985).

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Look closer, sprinters have muscular everything...

People tend to lump all different types of running into one category but it's more complicated than that.

Marathon runners run long distances, within an aerobic heart range (ex 133 < 152 bpm for a 30yr male), maximizing distance by decreasing load as much as possible. Typically, if you do a dedicated endurance running regiment your body will favor Type I (slow twitch) muscle mass which uses energy (oxygen, glycogen) more efficiently and reduce Type II (fast twitch) muscle mass which trades efficiency for power. That's why experienced marathon runners will typically appear very skinny.

Sprinters are the opposite. Sprinting requires exercise to be pushed into the aerobic ranges up the V02 max (ex 152 < 190 bpm for a 30yr male). The body has a limited amount of time it can maintain an anaerobic intensity due to the impurities that anaerobic metabolism create. To increase the intensity and duration you need more Type II (fast twitch) muscle mass and an increased ability to process the impurities created by anaerobic stress.

That's why you can hit the 'runners high' during an aerobic workout where you feel like you can keep going forever and you get the 'muscle burn' from doing anaerobic workouts.

So why are sprinters so muscular?

First, increase your anaerobic range to be higher by doing HIIT (High Intensity Interval Training) workouts. Basically, do short hard bursts for of activity (like sprinting) for a few minutes followed by recovery periods to allow your body to recover from the anaerobic stress. The rule is, the harder you push, the harder you will be able to push.

Second, here's where distinguishing between marathon runners and sprinters will start to make sense. HIIT training (including sprinting) uses your whole body. Make no mistake, high impact, high intensity exercises work your core and upper body as well as your lower body. Unlike endurance running, it's actually beneficial to focus on all muscle groups as long as you're not just putting on unnecessary bulk.

Third, Type II muscle burns lots of energy and I mean a lot. Not only do sprinters have a lot of Type II mass from head to toe, they also have highly optimized circulatory systems. The high energy burn and increased blood flow lead to a very low body fat percentage giving a very defined 'cut' look.

In conclusion, Type II muscle mass and upper body strength is bad for an endurance runner because it adds weight and unnecessarily consumes more energy. But, for a sprinter Type II upper body mass is generally a result of working out and also a good counter to balance the force being exerted by the lower body.

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