The effect of rat resistance ladder climbing exercise on skeletal muscle hypertrophy

Abstract

Backgrounds: Resistance exercise is one of the methods that are used to maintain skeletal muscle mass and to increase muscle strength. Muscle quality (MQ) is a force per unit muscle mass

it is used to represent one of the resistance exercise effects. Recent studies suggested that ladder climbing exercise as a resistance exercise and they reported the increase in flexor hallucis longus (FHL) skeletal muscle mass. In this study, ladder climbing apparatus was modified for rat to mimic human resistance exercise. The purpose of this study was to confirm and evaluate whether a ladder climbing exercise is an efficient resistance exercise for an animal model. Methods: Male Sprague-Dawley rats (n=16) were divided into 2 groups

control group (CON

n=8) and exercise group (EX

n=8). Ladder climbing exercise was performed three times in a week, for 12 weeks (total 36 bouts, each bout consists of 10 climb ups). EX group climbed 100 cm high and 25 cm wide ladder angled at 85º with the weights secured to its tail. The intensity of ladder climbing exercise was progressively increased every week. Grip strength was measured at the first, fourth, eighth and the last week. Body weight was measured in every week. Skeletal muscles including biceps (BIC), soleus (SOL), gastrocnemius (GAS), tibialis anterior (TA), extensor digitorum longus (EDL), flexor hallucis longus (FHL) and plantaris (PLN) were dissected and their weights were measured. In addition, skeletal muscle cross sectional area was analyzed in EDL and TA. The muscle quality (MQ) was calculated by the ratio of grip strength (g) to the sum of skeletal muscle masses (g) in each muscle. Results: There was no significant difference in body weight between CON and EX group, which were from ten-week-old to fifteen-week-old. However, from the point of sixteen-week-old to the end of experiment, CON group showed higher BW than EX group (p<0.05). In relative skeletal muscle weights of EX group, it was resulted that only the FHL muscle showed greater tendency than that of CON group (p=0.065). In CSA analysis, EX group showed bigger fiber size in EDL and TA muscles than those of CON group (p<0.001 each). In the grip strength test, EX group had stronger grip strength than CON group after the 12th week of exercise training (p=0.01). In Muscle quality, EX group showed significantly higher values than CON group (p=0.01). Conclusion: In this study, 12 weeks of progressive resistance laddering exercise 1) decreased body weight, 2) increased relative skeletal muscle weight in FHL muscle, 3) enhanced CSA in EDL and TA muscles, and 4) elevated MQ index. Therefore, the ladder climbing exercise and exercise protocols were found to be an appropriate, yet effective exercise program that lead toward skeletal muscle hypertrophy. Key words Ladder climbing exercise, Progressive resistance exercise, Skeletal muscle mass, Muscle strength, Muscle quality

Student number: 2011-21606