Metabolic power response to added mass on the lower extremities during running

Background: Wearable exoskeletal devices can enhance locomotor performance, but their mass results in a metabolic penalty. Previous studies have quantified the metabolic cost of running with added mass on the feet, but less is known about the effects of adding mass to the thigh and shank segments. Aim: To quantify the metabolic cost of running with additional leg mass. Methods: 15 participants (7 F, 8 M) completed treadmill running trials (3 m/s) normally and with lead mass (300–1350 g) attached to either the thigh, shank, or foot, bilaterally. We measured metabolic power using expired gas analysis. Results: Per 1000 g of added mass per leg, gross metabolic power increased by approximately 16% (foot) and 11% (shank) for females which was slightly greater than the 11% and 8% increases for males, respectively. For thigh loading, metabolic power increased by just 4% per 1000 g in both sexes. Conclusion: Adding mass more distally on the leg increases the metabolic cost of running to a greater extent. For the same absolute added mass on the foot or shank, metabolic power increases more in females.