AUTHOR=Chen Shiqin , Wang Dan , Zhang Qin , Shi Yue , Ding Haiyong , Li Fei 

TITLE=Relationship Between Isokinetic Lower-Limb Joint Strength, Isometric Time Force Characteristics, and Leg-Spring Stiffness in Recreational Runners

JOURNAL=Frontiers in Physiology

VOLUME=Volume 12 - 2021

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.797682

DOI=10.3389/fphys.2021.797682

ISSN=1664-042X

ABSTRACT=Neuromuscular characteristics, such as lower-limb joint strength and the ability to rapidly generate force, may play an important role in leg-spring stiffness regulation. This study aimed to investigate the relationship between isokinetic knee and ankle joint peak torque (PT), the force-time characteristics of isometric mid-thigh pull (IMTP), and leg stiffness (Kleg) /vertical stiffness (Kvert) in recreationally trained runners. Thirty-one male runners were recruited and underwent three separate tests. In the first session, the body composition, Kleg, and Kvert at running speed of 12 and 14 km·h-1 were measured. In the second session, isokinetic knee and ankle joint PT at 60°·s-1 were tested. The force-time characteristics of the IMTP were evaluated in the final session. Pearson’s product-moment correlations, with the Benjamini–Hochberg correction procedure, showed that the knee flexor concentric and eccentric, and extensor concentric PT (r = 0.473 to 0.654, p < 0.05) were moderately to largely correlated with Kleg and Kvert at 12 and 14 km·h-1. The knee extensor eccentric PT (r = 0.440, p = 0.050) was moderately correlated with the 14 km·h-1 Kvert. The ankle plantar flexor concentric and dorsiflexor eccentric PT (r = 0.506 to 0.571, p < 0.05) were largely correlated with Kleg at 12 km·h-1. The ankle plantar flexor concentric and eccentric, and dorsiflexor eccentric PT (r = 0.436 to 0.561, p < 0.05) were moderately to largely correlated with Kvert at 12 and 14 km·h-1. For IMTP testing, high correlation was only found between the IMPT PF and Kvert at 14 km·h-1 (r = 0.510, p = 0.014). Thus, superior leg-spring stiffness in recreational runners may be related to increased knee and ankle joint strength, eccentric muscular capacity, and maximal force production.