An Underwater Exoskeleton for Scuba Diving: Reducing Air Consumption and Muscle Activation Through Knee Assistance

Evolutionary pressures have pushed humans to become efficient walkers, but inefficient divers. People consume more energy to travel the same distance underwater than on land. In diverse overground locomotion, emerging exoskeletons have reduced the metabolic cost of humans. Can we also improve the energy economy in underwater locomotion via exoskeletons? Here, we propose an underwater exoskeleton to assist scuba diving using flutter kick, by applying assistive knee extension torque during the strike phase of the diving kick cycle. When divers wore the powered exoskeleton, the average net air cost across six experienced divers was reduced by 22.7 $\pm$ 10.0%, and the peak quadriceps activation was decreased by 20.9 $\pm$ 7.5%, compared with normal diving without the exoskeleton. The average gastrocnemius activation also decreased by 20.6 $\pm$ 5.3%, suggesting that the divers sufficiently utilized the exoskeleton assistance. These results indicate that applying exoskeleton assistance is conducive to improving the endurance of human underwater diving and enhancing our ability to explore the underwater world. Our study extends the application boundary of wearable robots, and provides a reference for the design and assessment of future underwater assistive devices, with the potential to strengthen the connection between humans and the ocean.