There has been much discussion in recent years about proper running form. From foot strike to knee drive to torso position, the experts debate endlessly about what will make us faster and more efficient runners. One aspect of running form that receives less attention is arm carriage. While most runners can recognize what proper upper body form looks like, many of us fail to practice it. Even the famous four-time Boston and New York City Marathon champion Bill Rodgers was notorious for swinging his arms across his body. Although it worked for him, most runners who aren't already using their arms efficiently could benefit from some form correction and directed strength training.

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A new study published in the Journal of Experimental Biology sought to discover just how much arm swing affects metabolic cost while running. To test this, they had runners run with their arms behind their back, across their chest, and on their head. While this exercise undoubtedly looked peculiar, it elicited some interesting results, finding that metabolic cost was greater in all three conditions compared to when using a normal arm swing. More specifically, the metabolic cost was three percent greater when they held their hands behind their backs, nine percent greater when they had their hands across their chest, and 13 percent greater when they put their hands on their head. They concluded that the traditional swinging of the arms has real metabolic and biomechanical benefits. Of course it should be noted that metabolic cost may have simply increased as a result of the fact that these alternate arm positions were not natural for the participants.

To be sure, any time you change anything about your running form, energy costs can increase until you've grown accustomed to the changes. Anecdotally, however, most runners would likely agree that running with your arms overhead or across your chest is less efficient than pumping at your sides, even if you took the time to try to train your body to function in those alternate positions.

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Mark Sullivan, a coach in Freeburg, Pennsylvania who has run 28 consecutive Boston Marathons, says you can easily spot a runner who has less than ideal arm carriage. "The most obvious sign is when their fists come up too high or they cross their body and some have their arms hanging almost straight down," he says. He often sees this in new runners and sometimes more experienced runners when they reach the point of fatigue.

While there are many reasons why runners don't carry their arms correctly, overall deficiencies in form are often the culprit. "I see it as a possible overcompensation for lack of forward lean," says Sullivan. "When they aren't leaning with their body correctly and driving with the legs, they try to make up for it by driving their arms more."

He also notes that lingering injuries or issues with range of motion can affect how your upper body is functioning on the run. "Because of the corresponding arm/leg connection, poor arm swing can be a result of a leg issue that may be caused by an injury or lack of flexibility," he explains.

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