Looking at the metabolic costs of running and the burden of arms. The paper is behind a paywall - the estimate of the metabolic cost of arms seems a bit contrived in this disucssion (the paper may be robust), but the overall conclusion seems reasonable.
The metabolic cost of human running: is swinging the arms worth it?
Christopher J. Arellano1,2,* and Rodger Kram1
1Integrative Physiology Department, University of Colorado, Boulder, CO 80309, USA
2Ecology and Evolutionary Biology Department, Brown University, Providence, RI 02912, USA
Although the mechanical function is quite clear, there is no consensus regarding the metabolic benefit of arm swing during human running. We compared the metabolic cost of running using normal arm swing with the metabolic cost of running while restricting the arms in three different ways: (1) holding the hands with the arms behind the back in a relaxed position (BACK), (2) holding the arms across the chest (CHEST) and (3) holding the hands on top of the head (HEAD). We hypothesized that running without arm swing would demand a greater metabolic cost than running with arm swing. Indeed, when compared with running using normal arm swing, we found that net metabolic power demand was 3, 9 and 13% greater for the BACK, CHEST and HEAD conditions, respectively (all P<0.05). We also found that when running without arm swing, subjects significantly increased the peak-to-peak amplitudes of both shoulder and pelvis rotation about the vertical axis, most likely a compensatory strategy to counterbalance the rotational angular momentum of the swinging legs. In conclusion, our findings support our general hypothesis that swinging the arms reduces the metabolic cost of human running. Our findings also demonstrate that arm swing minimizes torso rotation. We infer that actively swinging the arms provides both metabolic and biomechanical benefits during human running.