Gymnastik- och idrottshögskolan, GIH

AIM: To describe ribosome biogenesis during resistance training, its relation to training volume and muscle growth.

METHODS: A training group (n = 11) performed 12 sessions (3-4 sessions per week) of unilateral knee extension with constant and variable volume (6 and 3-9 sets per session respectively) allocated to either leg. Ribosome abundance and biogenesis markers were assessed from vastus lateralis biopsies obtained at baseline, 48 hrs after sessions 1, 4, 5, 8, 9, and 12, and after eight days of de-training, and from a control group (n = 8). Muscle thickness was measured before and after the intervention.

RESULTS: Training led to muscle growth (3.9% over baseline values, 95% CrI: [0.2, 7.5] vs. control) with concomitant increases in total RNA, rRNA, UBF, and rpS6 with no differences between volume conditions. Total RNA increased rapidly in response to the first four sessions (8.6% [5.6, 11.7] per session), followed by a plateau and peak values after session 8 (49.5% [34.5, 66.5] above baseline). Total RNA abundance was associated with UBF protein levels (5.0% [0.2, 10.2] per unit UBF), and the rate of increase in total RNA levels predicted hypertrophy (0.3 mm [0.1, 0.4] per %-point increase in total RNA per session). After de-training, total RNA decreased (-19.3% [-29.0, -8.1]) without muscle mass changes indicating halted biosynthesis of ribosomes.

CONCLUSION: Ribosomes accumulate in the initial phase of resistance training with abundances sensitive to training cessation and associated with UBF protein levels. The average accumulation rate predicts muscle training-induced hypertrophy.