Author(s): TSENG, K.W., TSENG, W., HSIEH, C., FU, S., Institution: UNIVERSITY OF TAIPEI, Country: CHINA, Abstract-ID: 1714

INTRODUCTION:
Unilateral trainings benefits on contralateral muscles have long been established, yet evidence for heterologous muscle cross education remains scarce. This study explored the overflow effect from ipsilateral exercises via two methods: firstly, a maximal eccentric contraction (MaxEC1) on elbow flexors, followed by one (MaxEC2) on same-side knee extensors; secondly, MaxEC1 on knee extensors, then MaxEC2 on elbow flexors. The aim was to investigate cross-educations protective effects, potentially reducing muscle damage and boosting recovery across different muscle groups with sequential eccentric contractions.
METHODS:
The study recruited 32 healthy women aged 20–30, divided into four groups: non-dominant upper limb / lower limb (NU/NL), control / non-dominant lower limb (C/NL), non-dominant lower limb / upper limb (NL/NU), and control / non-dominant upper limb (C/NU), each with eight participants. NU/NL group undertook 30 MaxEC1 with non-dominant elbow flexors and 60 MaxEC2 with knee extensors. NL/NU reversed this, with 60 MaxEC1 on knee extensors and 30 MaxEC2 on elbow flexors. C/NU did 30 MaxEC1 on elbow flexors, while C/NL did 60 MaxEC1 on knee extensors. NU/NL and NL/NU conducted their MaxEC2 14 days after MaxEC1. Variables measured included plasma creatine kinase (CK), muscle soreness (DOMS), limb circumference (CIR), joint range of motion (ROM), maximal voluntary isometric contraction (MVC) torque, maximal isokinetic concentric strength (ISOK), acoustic radiation force impulse (ARFI), and joint release angle (JRA), assessed before MaxEC1, after MaxEC2, and daily for five days post-MaxEC2.
RESULTS:
NU/NL exhibited quicker recovery in CK, DOMS, ROM, JRA, MVC, ISOK, and ARFI metrics compared to C/NL. Similarly, NL/NU demonstrated faster recovery across all measured variables when compared to C/NU. Notably, significant differences were observed between NU/NL and C/NL in DOMS on Day 2 post-MaxEC2 (p < .05), in MVC on Days 0–2 post-MaxEC2 (p < .05), in ISOK on Days 0–2 post-MaxEC2 (p < .05), in JRA at angles of 45° and 60° on Day 3 post-MaxEC2 (p < .05), and in CK on Days 1 and 2 post-MaxEC2 (p < .05). Between NL/NU and C/NU, significant differences emerged in ROM on Days 3–5 post-MaxEC2 (p < .05), in ARFI on Days 0–2 post-MaxEC2 (p < .05), in MVC on Days 0, 1, and 4 post-MaxEC2 (p < .05), in ISOK across Days 0–5 post-MaxEC2 (p < .05), and in CK on Days 1 and 2 post-MaxEC2 (p < .05).
CONCLUSION:
The results of this study are similar to those found by Ben in 2018, which demonstrated that unilateral leg press resistance training can enhance both contralateral homologous and heterologous muscles (2). This study suggests that a maximal eccentric contraction on elbow flexors or knee extensors can reduce subsequent muscle damage in the same-side muscle group. These findings can aid coaches, trainers, and therapists in improving rehabilitation and training practices.
Reference:
1. Hyldahl, et al., Exerc Sport Sci Rev., 2017
2. Ben Othman, et al., Appl Physiol Nutr Metab., 2018