Energy consumption during level walking with arm and knee immobilized

Objective: To determine whether there is an increase in energy use for able -bodied subjects with their arm and/or knee immobilized, while walking on a level surface at comfortable walking speed (CWS). Design: Prospective, quantitative, with randomly sequenced experimental tri als. Setting: Rehabilitation center. Participants: Ten healthy subjects, none of whom had gait abnormality. Intervention: Subjects walked on a treadmill at CWS under 4 conditions: (1) without an arm or knee immobilized (N); (2) with an arm immobilized (AI); (3) with a knee immobilized (KI); and (4) with both arm and ipsilateral kne e immobilized (KAI). Main Outcome Measures: Breath-by-breath oxygen cost; differences in energy consumption in trials during which constraints were used were compared with energy consumed under the N condition and the percentage of change was cal culated. Results: Mean oxygen cost increased by 22.7% with a knee immobilized compar ed with N values (mean difference, .044mL . kg(-1) . m(-1), p < .0001), and increased by 24.7% with a knee and arm immobilized (mean difference, .048m L . kg(-1) . m(-1), p < .0001). However, no significant differences existed in oxygen cost with Al compared with N, or with KAI compared with KI. The differences in CWS between the stages followed a similar pattern. Conclusions: Arm immobilization does not increase energy expenditure during level walking at CWS, and does not further increase energy expenditure whe n the ipsilateral knee also is immobilized.