Acute effect of HAL (limb type)-assisted cybernic voluntary control squat exercise on tennis serve speed

Abstract

The fastest serve at the 2022 US Open Tennis was 141 mph (226.9 km/h, Alexander Bublik, KAZ) and 128 mph (205.9 km/h, Coco Gauff, USA) for men and women, respectively. This speed is expected to increase in the future. Most studies focused on improving serve performance have been conducted in the fields of sports biomechanics and exercise physiology. There are no studies focusing on the voluntary control of the brain, spinal cord, motor nerves, musculoskeletal system, and service performance. Recently, a wearable cyborg, Hybrid Assistive Limb (HAL), has been utilized as a rehabilitation device in patients with stroke, cerebral palsy, and spinal cord injury. We aimed to determine the acute effect of Cybernic Voluntary Control squat exercises using HAL on the serve speed. Four male tennis coaches with extensive teaching experience (mean age: 32.5 ± 0.6 years, teaching experience: 10.5 ± 0.6 years) were included in the study. The results showed an increase of approximately 7% in the in serve speed after HAL-assisted squatting. This was attributed to the interactive biofeedback between HAL and the participants, which may have produced the immediate effect. HAL use could maximize the physical functions of tennis players and guide post-injury rehabilitation exercises.