Joint Angles at Heel Strike and Toe Off during Motorized and Non-Motorized Treadmill Locomotion

Abstract

Treadmill exercise during spaceflight may mitigate cardio-respiratory, musculoskeletal, and neuromuscular deconditioning. The International Space Station (ISS) treadmill operates in a motorized (M) and non-motorized (NM) mode. Differences in peak vertical ground reaction forces (GRF) between M and NM treadmill locomotion have been demonstrated, however, lower body joint kinematics have not been compared between treadmill modes. PURPOSE: To compare hip, knee, and ankle joint angles at heel strike and toe off between M and NM treadmill while walking (1.34 m·s−1; 3 mph) and running (2.68 m·s−1; 6 mph). METHODS: Twenty subjects (10 men, 10 women; 31±5 yr, 172±10 cm, 68±13 kg) exercised on a ground-based version of the ISS treadmill. Subjects completed three 10-s trials at each speed on separate days in random order. Kinematic data were collected at 60 Hz with a multiple-camera infrared video motion capture system. Paired t-tests were used to assess differences between treadmill modes within each speed (p<0.05). RESULTS: Hip and knee flexion and ankle dorsiflexion at heel strike were greater for NM. At toe off, subjects had greater hip flexion and less knee flexion during NM locomotion.Table: Caption not availableCONCLUSION: Subjects altered their gait kinematics from M to NM, perhaps in response to the increased horizontal force required to propel the treadmill belt during NM locomotion. Kinematic differences between M and NM may influence neuromuscular activation patterns, resulting in different training adaptations in normal gravity and perhaps dissimilar protection against microgravity-induced deconditioning.