Habitual endurance running does not mitigate age-related differences in gait kinetics.

Older adults often walk with smaller ankle joint kinetics and larger hip joint kinetics compared to young adults. These age-related differences have been attributed, in part, to weaker plantarflexor muscles. While it is thought that regular physical activity helps to maintain muscle strength and mobility in older adults, physical activity levels on average decline with age. Therefore, understanding the effect of physical activity level on gait kinetics is an important objective for the management of mobility impairment in older adults. The purpose of this study was determine the effect of habitual endurance running on lower-extremity joint kinetics. 12 male older long-term runners (67 ± 5 yrs., 1.79 ± 0.07 m, 77.3 ± 13.7 kg) and 12 male older non-runners (70 ± 3 yrs., 1.78 ± 0.06 m, 79.68 ± 10.6 kg), performed overground walking trials at 1.3 m/s while kinematic and kinetic data were collected. Participants also performed maximal voluntary contractions at the hip, knee, and ankle joints on an isokinetic dynamometer. Older runners displayed similar ankle plantarflexor strength, similar hip extensor strength, and greater knee extensor strength compared to older non-runners, and walked with similar ankle joint kinetics (p > 0.05), and larger hip joint kinetics compared to older non-runners (p < 0.05). Thus, physical activity, in the form of running at least 20 miles/wk. and training for at least one race per year, did not mitigate the characteristic age-related differences in gait kinetics. Our findings may indicate that age-related differences in lower-extremity gait kinetics are a normal consequence of natural aging.