Author(s): CHO, Y.H., JO, I., YOON, J., LEE, H., Institution: YONSEI UNIVERSITY, Country: KOREA, SOUTH, Abstract-ID: 1920

INTRODUCTION:
Performance and efficiency enhancement during stretch-shortening cycle (SSC) exercises, such as jumping, are related to the utilization of elastic energy stored in the muscle-tendon complex. A recent study (Kosaka et al., Journal of Sports Sciences, 2023) quantified the elastic energy of the Achilles tendon and found its relationship with the SSC effect in a single joint. However, in daily locomotion or exercise, multi-joint movements are more common than single-joint movements. In this study, we aim to investigate the correlation between jumping in multi-joint situations and Achilles tendon (AT) elastic energy.
METHODS:
Fourteen healthy adult males participated in this study and were divided based on their maximal countermovement jump (CMJ) height into a high jump group (HJG: age: 26.4 ± 0.1 yr, height: 179.4 ± 4.3 cm, weight: 80.7 ± 9.3 kg) and a low jump group (LJG: age: 25.6 ± 1.5 yr, height: 176.9 ± 6.5 cm, weight: 77.4 ± 8.1 kg). Subjects performed maximum plantar flexion (PF) on a custom-built dynamometer, and maximum PF torque was measured. The elongation of the Achilles tendon (AT) was measured using B-mode real-time ultrasound imaging to assess elastic energy and stiffness. Countermovement jump (CMJ) and drop jump (DJ) were performed to measure jumping ability. In the muscle force-elongation curve, the section from 50% to 100% of the force was defined as stiffness (Kubo, Keitaro et al., British journal of sports medicine, 2004), and the section below the curve was defined as elastic energy (Kubo, Keitaro et al., Physiological, 2017).
RESULTS:
The HJG showed greater elastic energy storage than the LJG (HJG: 3.7 ± 1.4, LJG: 2.2 ± 0.9), and higher jump height for CMJ (HJG: 46.9 ± 4.55, LJG: 36.5 ± 4.5), DJ20 (HJG: 42.1 ± 6.1, LJG: 32.3 ± 6.6), and DJ30 (HJG: 42.9 ± 4.6, LJG: 34.2 ±5.5). However, there was no statistically significant difference in stiffness. Elastic energy and jump height showed significant correlation (CMJ: .46, DJ20: .45, DJ30: .31).
CONCLUSION:
Elastic energy has been shown to be associated with jump height involving SSC in both single-joint and multi-joint movements. The HJG exhibited higher Achilles tendon elastic energy at the ankle, supporting a positive correlation tendency with jump height, which suggests a relationship between elastic energy and SSC effect. Additionally, as a measure of tendon properties closely related to SSC, tendon elastic energy has been shown to be more useful than tendon stiffness, which has been used in many previous studies.