Effects Of Lower Body Positive-pressure Treadmill Walking On Joint Kinematics And Electromyography In Obese Women.

Abstract

Obesity reduces knee flexion and ankle plantarflexion concomitant with prolonged activation of quadriceps and gastrocnemii during walking. PURPOSE: To determine how reduced body weight, independent of changes in body segment volume, affects lower extremity joint kinematics and muscle recruitment during walking. METHODS: Eight apparently healthy, obese women (Age: 37.3 ± 8.5y; BMI: 36.3 ± 4.1 kg/m2) walked at a self-selected pace on a lower body positive-pressure treadmill (LBPP) under four conditions: 1) control (CON), 2) 10% incline (INC), 3) 25% body weight support (BWS), and 4) BWS + INC. Joint kinematics were measured through bi-axial wireless electrogoniometers and time-synchronized with surface electromyography (EMG) of the vastus lateralis (VL), vastus medialis (VM), semitendinosis (ST), and medial gastrocnemius (MG). The gait cycle was defined by swing, weight acceptance (WA), midstance (MS), and pushoff (PO) according to plantarflexion (PF) and dorsiflexion (DF). Statistical comparisons were made by two-way repeated measures ANOVA. RESULTS: Joint kinematics and EMG activity were unchanged throughout swing. At the knee joint, INC increased mean knee flexion during WA (28.3 ± 12.9 v 21.8 ± 14.20, p < 0.001) and MS (25.3 ± 9.1 v 19.4 ± 12.00, p = 0.044) compared to CON. BWS + INC reduced mean knee flexion during WA (23.8 ± 13.3, p < 0.001) and MS (21.1 ± 12.40, p = 0.020) compared to INC. Similarly, mean PF was reduced during INC during WA (10.1 ± 1.7 v 13.6 ± 2.20, p < 0.001) and MS (4.4 ± 5.3 v 8.0 ± 4.90, p = 0.008) compared to CON. BWS + INC increased mean PF compared to INC during WA (12.3 ± 1.70, p = 0.009) and MS (7.0 ± 5.50, p = 0.006). During PO, both BWS (10.8 ± 4.8°) and BWS + INC (9.8 ± 5.4°) increased mean PF compared to CON (8.1 ± 4.6°) and INC (6.5 ± 6.1°). Compared to CON, INC increased mean VL EMG activity during WA (31.3 ± 10.1 v 17.8 ± 6.0 %MVIC) and MS (19.2 ± 5.2 v 9.5 ± 2.3 %MVIC), which was restored by BWS + INC (19.5 and 12.1 %MVIC). There was a main effect for body weight support to reduce mean MG EMG during MS. CONCLUSIONS: Weight loss, independent of changes in body segment volume reduces knee flexion during WA and MS phases of incline walking concomitant with reduced VL EMG activity. Weight loss increases PF throughout stance during incline walking despite reduced MG EMG activity.