Walking Economy and Preferred Speed in Old and Very Old Men

Purpose: With aging, the decline in preferred walking speed (PWS), influenced by the increased energy cost of walking (CoW), is a key predictor of morbidity. However, the determinants associated with PWS and CoW remain poorly understood, especially after 80 years old. The aim of the study was to characterize the amplitude and mechanisms of age-related decline in CoW and PWS in old (OM) and very old (VOM) men.

Methods: Thirty-nine young men (YM, 22.1 ± 3.4 years), 34 OM (71.7 ± 4.1 years) and 23 VOM (85.8 ± 2.7 years) performed aerobic, neuromuscular, and gait assessments. Net CoW was measured on a treadmill. Physical activity (PA) was evaluated by questionnaire and accelerometry.

Results: Net CoW was 32% (p < 0.001), 19% (p < 0.01), 26% (p < 0.001) higher in VOM compared to OM for 1.11, 1.67 m.s-1 and PWS. Net CoW was also 27% (p < 0.001), 26% (p < 0.01), and 29% (p < 0.001) higher in OM compared to YM at these speeds. Linear regression stratified by age showed that net CoW at PWS was associated to step frequency (r = 0.79; p < 0.001) for OM and to both CV of stride mean time (r = 0.48; p < 0.05) and maximal strength of knee extensors (r = -0.54; p < 0.05) for VOM. The same analysis revealed that PWS was correlated with net CoW (r = -0.56; p < 0.05) and PA (r = 0.47; p < 0.05) in VOM.

Conclusions: The progressive increase in net CoW with age was associated with gait and neuromuscular impairments, particularly after the age of 80. This increase in net CoW was related to a decrease in PWS in VOM, suggesting an adaptation of PWS to compensate for the increase in energy demand. Maintaining a high level of PA may potentially delay the age-related decline in PWS despite an age-related increase in net CoW.