Resistance Training Reduces Skeletal Muscle Work Efficiency in Weight-Reduced and Non-Weight-Reduced Subjects.

OBJECTIVE: The objective of this study is to determine whether resistance training is similarly effective in reducing skeletal muscle efficiency and increasing strength in weight-reduced and maximal weight subjects.

METHODS: This study examined the effects of supervised resistance exercise on skeletal muscle in 14 individuals with overweight and obesity sustaining a 10% or greater weight loss for over 6 months and a phenotypically similar group of 15 subjects who had not reduced weight and were weight stable at their maximal lifetime body weight. We assessed skeletal muscle work efficiency and fuel utilization (bicycle ergometry), strength (dynamometry), body composition (dual energy x-ray absorptiometry), and resting energy expenditure (indirect calorimetry) before and after 12 weeks of thrice-weekly resistance training.

RESULTS: Non-weight-reduced subjects were significantly (10%-20%) stronger before and after the intervention than reduced-weight subjects and gained significantly more fat-free mass with a greater decline in percentage of body fat than weight-reduced subjects. Resistance training resulted in similar significant decreases (~10%) in skeletal muscle work efficiency at low-level exercise and ~10% to 20% increases in leg strength in both weight-reduced and non-weight-reduced subjects.

CONCLUSIONS: Resistance training similarly increases muscle strength and decreases efficiency regardless of weight loss history. Increased resistance training could be an effective adjunct to reduced-weight maintenance therapy.