Physiological and biomechanical analysis of treadmill walking up various gradients in men and women

This investigation was undertaken to examine the physiological and biomechanical responses during treadmill walking up various gradients in men and women. Groups of 11 men and 11 women took part in four experiments consisting of 8 min treadmill walks at 1.3 m·s^-1 up gradients of 0%, 5%, 10% and 15%. The subjects also underwent an anthropometric assessment during which their height, body mass (BM), percentage (%) body fat, lean body mass (LBM), and waist-to-hip ratio (WHR) were obtained. During exercise, each subject was videotaped during three walking cycles so that sagittal kinematics including stride length (SL) and frequency (SF) and ranges of motion achieved at the shoulder, hip and knee during a walking cycle could be determined using a motion analysis system. The motion capture was followed by a measurement of steady-state oxygen uptake (V̇O₂) and heart rate (HR) using indirect calorimetry and a HR monitor. Compared to men, women were higher in % body fat, but lower in height, BM, LBM, and WHR. The V̇O₂ in millilitres per kilogram per minute and HR were similar between men and women at 0% and 5%, but greater in women than men at 10% and 15%. The SL and SF were greater and smaller, respectively, in men than women up all gradients. Shoulder extension was greater up gradients of 10% and 15% in women than men, whereas no sex difference in shoulder flexion was noted. Hip extension and flexion as well as knee flexion remained the same between men and women up all gradients. An inverse relationship was observed between V̇O₂ in millilitres per kilogram per minute and BM, LBM, and WHR when men and women were combined. In conclusion, the mass-specific metabolic cost of treadmill walking up high gradients is greater in women than men. Such an increase in relative metabolic cost may be attributable to the fact that women are smaller in size, and/or have relatively more BM distributed peripherally. This sex difference may also be due to a greater movement of the upper limbs in women during walking uphill, although direct evidence is needed to support this contention.