ABSTRACT The purpose was to test whether lower-extremity vertical stiffness and gait mechanics explain differences in energy cost of walking (Cw) between individuals with normal weight (NW) and obesity (OB).… Click to show full abstract
ABSTRACT The purpose was to test whether lower-extremity vertical stiffness and gait mechanics explain differences in energy cost of walking (Cw) between individuals with normal weight (NW) and obesity (OB). Ten OB (33.1 ± 2.0 kg m−2) and 10 NW (24.2 ± 1.3 kg m−2) walked for six minutes on an instrumented treadmill at 1.25 m s−1 while Cw, lower-extremity kinematics, and vertical stiffness (K vert) were measured. NW completed another trial with a loaded vest (NWL) to simulate the BMI of the obese group. Cw was 24% greater in OB (277.5 ± 45.3 J m−1) and 23% greater in NWL (272.7 ± 35.7 J m−1) than NW (211.0 ± 27.0 J m−1, P < 0.005). Mass-specific Cw (Cwkg) wasn’t different between conditions (P = 0.085). Lower-extremity K vert was 40% higher in OB (32.7 ± 5.2 kN m−1) than NW (23.3 ± 4.7 kN m−1, P < 0.001), but neither was different from NWL (27.5 ± 3.4 kN m−1, P > 0.05). Mass-specific K vert (P = 0.081) was similar across conditions. K vert was related to Cw (r = 0.55, P = 0.001). Cwkg wasn’t different between NW or OB, but there was a negative correlation between BMI and Cwkg driven by lower Cwkg in NWL. Cw and K vert covaried in proportion to body mass, but mass-specific K vert was unrelated to Cwkg. Mass-specific K vert was lower in NWL than OB due to NWL’s greater angle of attack, center of mass displacement, and joint range of motion.
               
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