Running with an Exotendon can Reduce Metabolic Rate Across a Range of Speeds

Metabolic rate, the amount of energy expended over time, can be influenced by passive assistive devices like specialized footwear and exoskeletons. While most assistive device research has focused on elite athletes or recreational runners at a single speed, few studies have explored how these devices might affect metabolic rate across a range of running speeds. This study investigates the effect of a passive assistive device (exotendon), which connects a runner's legs, on metabolic rate in recreational runners across multiple speeds. In contrast to previous work, only 9 of 16 participants reduced metabolic rate with the device at $2.67 ~\mathrm{m} / \mathrm{s}$, by an average of 7.6 %. While all participants significantly increased stride frequency - a key factor identified in previous work for its influence on metabolic rate - the group that did not reduce metabolic rate exhibited greater variability in average stride frequency for both conditions. For those who reduced metabolic rate with the exotendon at $2.67 ~\mathrm{m} / \mathrm{s}$, similar improvements extended across speeds from 1.68 to $4.36 ~\mathrm{m} / \mathrm{s}$. These results indicate that the exotendon's effect on metabolic rate varies across individuals but can extend beyond a single running speed in those who respond to the device. This suggests that passive assistive devices may benefit some runners across a range of speeds, with potential applications for training and performance as well as rehabilitation, where reducing energy demand could aid recovery and mobility.