Upper Extremity Function in Running. II: Angular Momentum Considerations

Abstract

Ten male recreational runners were filmed using three-dimensional cinematography while running on a treadmill at 3.8 m/s, 4.5 m/s, and 5.4 m/s. A 14-segment mathematical model was used to examine the contributions of the arms to the total-body angular momentum about three orthogonal axes passing through the body center of mass. The results showed that while the body possessed varying amounts of angular momentum about all three coordinate axes, the arms made a meaningful contribution to only the vertical component (Hz). The arms were found to generate an alternating positive and negative Hzpattern during the running cycle. This tended to cancel out an opposite Hzpattern of the legs. The trunk was found to be an active participant in this balance of angular momentum, the upper trunk rotating back and forth with the arms and, to a lesser extent, the lower trunk with the legs. The result was a relatively small total-body Hzthroughout the running cycle. The inverse relationship between upper- and lower-body angular momentum suggests that the arms and upper trunk provide the majority of the angular impulse about the z axis needed to put the legs through their alternating strides in running.

Three-dimensional angular kinematics of the lumbar spine and pelvis during running

“…During running the angular momentum about a vertical axis of the upper trunk and arms has been shown to be opposite to the angular momentum about a vertical axis of the lower extremities (Hinrichs, 1987). It is therefore likely that the kinematic pattern for axial rotation of the lumbar spine during running is a reflection of the angular momentum about a vertical axis of the upper trunk and arms developed to directly counteract the angular momentum about a vertical axis of the reciprocally swinging lower extremities.…”

“…Wiklander, Lysholm, and Lysholm (1987) reported a significant negative correlation between the degree of pelvic obliquity and the flexibility of the hamstrings. Interestingly, this group of investigators found that distance runners in comparison to sprinters had stiffer hamstrings, greater pelvic obliquity and suffered more exertion injuries around the lower back (Lysholm, Gillquist, & Nordin, 1982;Lysholm & Wiklander, 1985, 1987Wiklander et al, 1987). In order to verify any of these proposed relationships, an understanding of the typical kinematic patterns of the lumbar spine and pelvis during running is clearly the crucial starting point.…”

The metabolic cost of human running: is swinging the arms worth it?

“…Yet, removing the arms could lead to compensatory strategies that exact a metabolic cost. As Hinrichs (Hinrichs, 1987) discovered, the momentum effects of arm swing are due to the relatively longer distance of the arm's COM from the vertical axis, acting to generate the largest component of the vertical angular momentum of the entire upper body, which includes the head and trunk. Although the momentum effects of arm swing reduce the amount of torso rotation, there is likely a small cost resulting from the tonic muscular activity required to hold the arms in a flexed position at the elbow, a common style of swinging the arms during human running.…”

“…Both Hinrichs (Hinrichs, 1987) and Hamner et al (Hamner et al, 2010) identified that the primary function of arm swing during distance running is to counterbalance the angular momentum generated by the swinging legs about the vertical axis, resulting in a net vertical angular momentum that fluctuates with a relatively low magnitude about zero. Much earlier, Hopper (Hopper, 1964) speculated that in addition to helping maintain posture and balance, arm swing might assist with increasing the vertical ground reaction force to lift the runner, thus bouncing off the ground more quickly.…”

Control and function of arm swing in human walking and running

“…Our arms tend to swing out of phase with our legs, the right arm swinging forward with the left leg and vice versa. Although it has long been established that the arms do not swing as simple, unrestrained pendulums (Elftman, 1939;Fernandez Ballesteros et al, 1965;Jackson et al, 1978;Hinrichs, 1987;Ohsato, 1993;Webb et al, 1994;Gutnik et al, 2005), the extent to which the shoulder muscles actively drive the arms, and the effect of arm swing on stability and economy during walking and running are poorly understood. In this paper, we examined the control of arm swing during walking and running, and investigated the effect of restricting arm swing on stability and metabolic cost.…”