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
