Dozens of studies have found that carrying loads less than half one’s body weight typically costs an extra 20 percent of the added weight, and when loads get really heavy, the costs increase exponentially.21 Carrying stuff while walking is generally expensive because we not only spend more calories to elevate more weight during the first half of stance but also have to spend more energy to redirect our body as a whole upward and forward at the end of each step. In addition, when we carry things, our muscles have to work harder to keep us and the load stable.
