Energetics of walking in elderly people: factors related to gait speed.

BACKGROUND Slow walking speed in elderly people predicts increased morbidity and mortality. We examined factors that may be associated with decreased habitual walking speed in older men and women. METHODS Older (range: 60-88 years, mean = 72.5 years) men (n = 25) and women (n = 24) were recruited. The Short Physical Performance Battery, body composition, VO(₂peak) on a treadmill, VO₂ and rated perceived exertion during 10 minutes of walking at habitual gait speed and at a walking speed of 0.9 m/s, muscle strength, and level of physical activity were measured. RESULTS VO(₂peak) was strongly related to habitual gait speed (r = .744, p < .001) and remained significant even after controlling for age, muscle strength, and gender. Compared with the tertile of fastest walkers (mean gait speed, 1.37 ± 0.04 m/s), the tertile of slowest walkers (0.87 ± 0.02 m/s) were older (p < .001), shorter (p = .026), had lower lean body mass (p = .011), lower strength ( p < .001), less self-reported daily physical activity (p = .102), and higher relative (to VO(₂peak)) intensity during walking at their habitual speed (65.3% ± 3.9% vs 54.3% ± 2.1% of VO(₂peak), p = .013). CONCLUSIONS VO(p₂eak) was strongly associated with habitual walking speed, suggesting that as aerobic capacity declines with age, the exertion associated with habitual gait speed increases. A slowing of walking speed may be a response to increased perception of exertion. The extent to which exercise training affects habitual gait speed and fatigue is not clear.