Skeletal Muscle Damage in the Rat Hindlimb Following Single or Repeated Daily Bouts of Downhill Exercise

This study was conducted to quantify and compare the extent of fibre degenerative and regenerative processes indifferent muscles of the rat hindlimb following single or repeated daily bouts of treadmill exercise. Wistar rats were used as non-exercised controls, or subjected to one, five, or ten (n = 8 per group), 30-minute daily bouts (- 16 °, 12 - 15 m · min^-1) of downhill exercise. Soleus (S), vastus laterals (VL), medial gastrocnemius (MC), plantaris (P), and tibialis anterior (TA) muscles were analysed from transverse cryosections stained with either H & E for morphological alterations indicative of fibre degeneration or regeneration, or mATPase activity for determination of fibre type. Results showed that in all groups, the percentage of morphologically altered fibres ( % AF) was greater in S (4 - 8 %) than in MC, VL, P, or TA (1 -2 %). The % AF across all muscles was; greater following only one, versus multiple exercise bouts, or versus no exercise. The proportions of AF of different histochemical types followed the same distribution pattern as the fibre type in the muscle area examined. These direct assessments indicate that the extent of fibre degenerative and regenerative processes varies among the different muscles involved, and is greater following a single bout, compared to repeated daily bouts, of exercise.

Key words

Treadmill exercise - degeneration - regeneration - histology - morphology - training