Climbing exercise with a newly‐developed apparatus for hypertrophy of the FHL, FDS and FDP muscle in rats

Abstract

The mass of the biceps brachii and the hind limb muscles, such as the gastrocnemius, do not significantly increase when performing climbing exercise with a newly‐developed apparatus in rats (EB 2007). The current study investigated whether the flexor hallucis longus (FHL), flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP), which contract to grip the wire mesh surface of the apparatus, increased in unloaded (Exp. 1) or weight‐loaded (Exp. 2) rats. In Exp. 1, 14 male rats were separated into a control (C) or exercise (E) group, group E was trained to climb inside a wire mesh box (1m height, 0.38 m width, 0.28 m depth) which was placed on a 53°C electric hot plate, without a weight. The exercise regimen consisted of 5 min × 6 sets/day, 3 days/wk for 8 weeks. Each group was pair‐weighed. In Exp. 2, the protocol was similar to Exp. 1 except that group E wore a rucksack containing a weight during the exercise. The masses of the FHL, FDS and FDP were significantly greater in group E than in group C in both Exp. 1 and Exp. 2 (P < 0.05). The differences in the FHL, FDS and FDP between groups E and C were 14, 13 and 17% in Exp. 1 and 12, 7 and 11% in Exp. 2, respectively, thus suggesting that the muscle hypertrophy in group E was not different between Exp. 1 and Exp. 2. In contrast, the gastrocnemius did not differ between the groups in either experiment. Therefore, the climbing exercise with the apparatus caused hypertrophy in the FHL, FDS and FDP but not in the gastrocnemius, thereby indicating that this exercise regimen causes regiospecific hypertrophy in the skeletal muscle. Although both models are considered to be useful as an exercise model of muscle hypertrophy since the hypertrophy was observed in both experiments, the unloaded model is considered to be a more user‐friendly model than the weight‐loaded model.