Author(s): KIM, A., JIEUN, L.2, JISUK, C.3, HOSEONG, L.2, Institution: DANKOOK UNIVERSITY, Country: KOREA, SOUTH, Abstract-ID: 767

INTRODUCTION:
Regular exercise reduces the risk of chronic diseases such as coronary artery disease and type 2 diabetes [1]. Resistance training, including both concentric (muscle shortening) and eccentric (muscle lengthening) actions, enhances muscle function and metabolic health [2]. However, the prolonged effects of eccentric exercise on functional and metabolic measures remain unclear. This study investigates the long-term impacts of eccentric training on muscle function and metabolic markers, hypothesizing that eccentric exercise induces beneficial adaptations.
METHODS:
Eighteen healthy males, without eccentric training for six months prior, were randomly assigned to either an eccentric (ECC, n=9) or concentric (CON, n=9) training group. Each group performed a single bout of maximal voluntary contractions of the trunk extensor muscles per week for eight weeks. Measurements of muscle function, soreness, blood lipid profiles, and glycemic markers were pre-exercise, immediately post-exercise, and 48 hours post-exercise in weeks 1 and 8. Repeated measures ANOVA were used for analysis.
RESULTS:
ECC participants showed increased muscle soreness and plasma creatine kinase (CK) levels in week 1, which significantly decreased by week 8, indicating adaptation. Both training types improved muscle function; however, ECC training led to significantly greater increases in resting isometric torque (p<0.05). ECC training also reduced total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG), while increasing high-density lipoprotein cholesterol (HDL-C) by week 8 (p<0.05), whereas CON training improved only TG (p<0.05). In terms of glycemic response, acute ECC exercise initially increased glucose, insulin, and homeostasis model assessment (HOMA) values in week 1. However, chronic ECC training significantly reduced fasting insulin, glucose, and HOMA values by week 8 (p<0.05), along with decreased glycosylated hemoglobin (HbA1c), indicating improved insulin sensitivity. CON training did not significantly alter these metabolic markers.
CONCLUSION:
Eccentric exercise has been demonstrated to enhance muscle function, lipid metabolism, and glycemic control. Despite the initial muscle damage that occurs, prolonged ECC induces adaptations that reduce soreness and improve muscle performance. These observations align with the findings of previous research, which demonstrated that eccentric training improves metabolic health via neuromuscular and molecular adaptations [3]. Future studies should explore ECC exercise in clinical populations to optimize training strategies for disease prevention and rehabilitation.