Excess body weight and gait influence energy cost of walking in older adults

Purpose: The objective of this investigation is to study how excess body weight influences the energy cost of walking (Cw) and determine whether overweight and obese older adults self-select stride frequency to minimize Cw. Methods: Using body mass index (BMI), men and women between the ages of 65 and 80 yr were separated into normal weight (NW, BMI <= 24.9 kg.m(-2), n = 13) and overweight-obese groups (OWOB, BMI >= 25.0 kg.m(-2), n = 13). Subjects walked at 0.83 m.s(-1) on an instrumented treadmill that recorded gait parameters and completed three 6-min walking trials; at a preferred stride frequency (PSF), at +10% PSF, and at -10% PSF. Cw was determined by indirect calorimetry. Repeated-measures ANOVA was used to compare groups, and associations were tested with Pearson correlations, alpha = 0.05. Results: OWOB had 62% greater absolute Cw (301 +/- 108 vs 186 +/- 104 J.m(-1), P < 0.001) and 20% greater relative Cw(kg) (3.48 +/- 0.95 vs 2.91 +/- 0.94 J.kg(-1).m(-1), P = 0.046) than NW. Although PSF was not different between OWOB and NW (P = 0.626), Cw(kg) was 8% greater in OWOB at + 10% PSF (P < 0.001). At PSF, OWOB spent less time in single-limb support (33.1% +/- 1.5% vs 34.9% +/- 1.6 % gait cycle, P = 0.021) and more time in double-limb support (17.5% +/- 1.6% vs 15.4% +/- 1.4% gait cycle, P = 0.026) than NW. In OWOB, at PSF, Cw was correlated to impulse (r = -0.57, P = 0.027) and stride frequency (r = 0.51, P = 0.046). Conclusions: Excess body weight is associated with greater Cw in older adults, possibly contributing to reduced mobility in overweight and obese older persons.