A Novel Weighted Suit to Assess Ambulatory Performance Under Reduced Strength-to-Body Weight Conditions

Abstract

Performance outcomes of ambulatory tasks are influenced by human performance capabilities as they relate to one’s own body weight (e.g., strength to body weight). Alterations in this body-weight-specific performance are relevant to situations in which performance is impaired with minimal impact to body weight (e.g., muscle deconditioning in astronauts or aging), and also conditions where total weight to be carried is increased without a corresponding increase in performance (e.g., firefighters or soldiers who are required to carry heavy gear). PURPOSE: To use a novel weighted suit that has been specifically designed to manipulate strength to body weight (BW) ratios to determine the effects on extended duration (5 minutes to 2 hours) task performance. METHODS: Baseline aerobic capacity, isokinetic knee extension strength, isometric knee extension strength, isometric leg press strength, and isotonic leg press power were assessed in 17 individuals. Subjects performed 4 self-selected pace performance tests on a ladder ergometer (480 total rungs) and a motorized treadmill (10 km) while wearing a weighted suit under mock conditions (0%, suit fabric only) and with 40%, 60%, and 80% of their BW added. Survival curves were plotted for intermediate check points and completion under each condition, and performance to BW curves were generated. RESULTS: Percentage of subjects that completed the half-way point and end point, respectively, for the ladder were as follows: 100% and 100% for the mock load; 100% and 93% for 40% BW load, 100% and 79% for 60% load; and 69% and 62% for 80% load. Percentage of subjects that completed 5 km and 10 km, respectively, for the treadmill were as follows: 100% and 100% for the mock load; 93% and 79% for 40% BW load, 64% and 29% for 60% load; and 8% and 0% for 80% load. Scatter plots for aerobic capacity to BW (including external load) and muscle performance measures to BW versus ladder and treadmill performance reveal the laboratory metric to performance relationships. CONCLUSIONS: Manipulation of strength to BW using a weighted suit affects task performance and can be used to define the relationships between altered capabilities and task performance outcomes.