Influence of energy cost of walking on gait speed and physical activity level in elderly women

INTRODUCTION It has been demonstrated that the age-associated increase in energy cost of walking (CW) may result in a slowing of gait speed (Schrack 2012). Physical activity level (PA) also declines with age (Troiano 2008). However, in our knowledge, no studies have examined the influence of CW on PA habitually maintained. Therefore, the aim of this study was to define the influence of CW on both gait speed and PA. METHODS 42 healthy young (YA) and older (OA) women (YA: age, 22.6±2.9 yr; BMI, 22.5±2.6 kg/m2; OA: age, 68.3±3.3 yr; BMI, 26.1±3.0 kg/m2) were recruited in the study. NetCW was analysed with indirect calorimetry during treadmill walking at different speeds and calculated subtracting resting metabolic rate measured during standing from gross metabolic rate. Gait speed, defined as the preferred walking speed (PWS) of the subject, was measured as the time taken to walk the middle 10m of 14m. To assess PA, subjects wore a multisensor activity monitor for a whole week, inferring time spent in moderate to vigorous PA (MVPA>3METs). MVPA were analysed in bouts of at least 10 consecutive minutes (MVPAbouts) and in overall minutes (MVPAtot). RESULTS No significant differences were found between the two groups for NetCW at the speed closest to the PWS, the gait speed and both MVPAbouts and MVPAtot (YA: NetCW, 2.89±0.38 J/kg/m; PWS, 5.0±0.7 km/h; MVPAbouts, 28±29 min/day; MVPAtot, 61±52 min/day; OA: Net CW, 3.07±0.63 J/kg/m; PWS, 4.8±0.5 km/h; MVPAbouts, 29±42 min/day; MVPAtot, 61±64 min/day). MVPAbouts was significantly lower than MVPAtot for both groups (p<0.0001) and only MVPAtot exceeded current PA guidelines (p=0.001). Regression analysis, adjusted for age and BMI, revealed that neither PWS nor PA were related to a lower NetCW at the speed closest to the PWS. Only fastest walkers had higher daily level of PA independently of age (r=0.376, p=0.013; r=0.324, p=0.035; for MVPAbouts and MVPAtot, respectively). DISCUSSION In our study elderly women did not show a decrease of PWS and PA due to age. Moreover, an equivalent NetCW of walking was found in healthy elderly women when compared to younger counterparts while walking at their PWS. The present results showed that in healthy elderly women CW is not affected by age allowing a high PWS and an elevated level of PA.