PhD Scientific Days 2025

Poster Session I. - N: Health Sciences

Assessment of Muscle Function and stretch-shortening cycle Performance in Older Adults: A Foundation for Eccentric Overload Resistance Training - A Pilot Study

Name of the presenter

MOHAMED Mohamed Abdelaziz Emam

Institute/workplace of the presenter

Semmelweis University

Authors

Mohamed Abdelaziz Emam MOHAMED, PhD¹, András Horváth¹, Bálint Kovács², Akman Mehmet², Beáta Csizmadia², Jingyi Ye², Linjie Zhang², János Négyesi², Tibor Hortobágyi²

1: Semmelweis University
2: Hungarian University of Sports Science

Text of the abstract

Introduction: Age-related decline is not uniform in measures of neuromuscular function. There is a relative maintenance in maximal voluntary eccentric vs. concentric and isometric force (MVC). It is unclear how age effects measures that are even more closely related to daily function such as stretch-shortening cycle (SSC) efficiency tested during dynamometry and vertical jumps. Identifying age-differences in neuromuscular outcomes could inform prescription of resistance training especially with an eccentric overload to target age-typical deficiencies at the start of a resistance training program.

Methods: We compared healthy, active young adults (32.4 ± 5.59 years, n=4) and older adults (73.75 ± 2.75 years, n=4) in selected neuromuscular outcomes of the knee extensor muscles. Participants performed MVC knee extension and SSC contractions on a dynamometer and peak strength, the rate of torque development and mechanical efficiency was calculated. In addition, squat and counter-movement jumps were also performed where jump height and related parameters calculated. All measurements were conducted twice to establish test-retest reliability.

Results: Mechanical efficiency and SSC effect during SSC contractions were similar between Young (Y: 45.09 ± 2.06%) vs. Old (O: 44.92 ± 1.13%) and (Y: 1.10 ± 0.10 vs. O: 1.08 ± 0.17) respectively. However, younger adults demonstrated knee extensor higher torque and rate of torque development during the isometric contractions (Y:0.78 ± 0.24 vs. O: 0.25 ± 0.17 Nm/ms, p = 0.01, d = 2.50). There also were no age-differences in MVC (Y: 130.45 ± 15.91 vs. O: 122.87 ± 23.26 Nm, p = 0.60, d = 0.39). Squat jump height (Y: 0.27 ± 0.05 vs. O: 0.13 ± 0.02 m, p < 0.01, d = 3.17), and countermovement jump height (Y: 0.34 ± 0.06 vs. O: 0.15 ± 0.03 m, p < 0.01, d = 3.87). All measurements demonstrated excellent test-retest reliability (ICC > 0.85).

Conclusion: While mechanical efficiency and SSC effect remain preserved with aging, explosive strength and jump performance show significant age-related declines. The lack of significant difference in MVC despite age differences suggests it may not be a sensitive indicator of age-related muscle function changes. Such data inform our subsequent eccentric overload training intervention to improve older adults’ neuromuscular function especially affected by aging.