Key result
Bilateral ablation of gastrocnemius and plantaris muscles in rats depressed specific force of the hypertrophied soleus muscle by 38% at days 1 and 3, and by 28% from days 5 to 30.
During early skeletal muscle hypertrophy induced by synergistic ablation, initial force deficits are associated with enlarged interstitial space and decreased protein concentration, while later deficits are likely due to intracellular changes.
Identifies interstitial and intracellular drivers of force deficits in early hypertrophy; hypothesis-generating for human resistance training adaptations.
The purpose was to study selected structural changes associated with the deficit in maximum specific force (N/cm2) during the early development of skeletal muscle hypertrophy. Ablation of gastrocnemius and plantaris muscles was performed bilaterally in 35-day-old rats (n = 41), and the soleus muscle was studied from days 1 to 30 thereafter. Compared with control muscles from age-matched unoperated rats (n = 48), muscle mass and cross-sectional area increased in parallel from 28 to 52% over the 30-day postoperative period. Specific force of hypertrophied muscle was depressed 38% at days 1 and 3, and by 28% from days 5 to 30 after synergistic muscle ablation compared with age-matched control values. Interstitial space was 38% greater than the control value of 20.4 +/- 1 microliters/100 mg at day 1 only. Protein concentration was depressed 15% for 7 days after the ablation operation, and connective tissue protein concentration was unchanged. The relative magnitude of increased mean fiber cross-sectional area was less than that of muscle mass until day 7 after ablation. Mononuclear cell infiltration in interfascicular spaces occurred from days 3 to 30 without light microscopic evidence of muscle fiber injury. Initial functional deficits are explained in part by an enlarged interstitial space and decreased protein concentration; later deficits are likely accounted for by intracellular changes.
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Kandarian et al. (1989) studied Skeletal muscle hypertrophy (n=89). Bilateral ablation of gastrocnemius and plantaris muscles vs. Age-matched unoperated rats was evaluated on Maximum specific force (N/cm2). Bilateral ablation of gastrocnemius and plantaris muscles in rats depressed specific force of the hypertrophied soleus muscle by 38% at days 1 and 3, and by 28% from days 5 to 30.
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