Increased muscle oxidative potential following resistance training induced fibre hypertrophy in young men

Hartman, Joseph W.; Phillips, Stuart M.; Tang, Jason E.
October 2006
Applied Physiology, Nutrition & Metabolism;Oct2006, Vol. 31 Issue 5, p495
Academic Journal
Some evidence suggests that resistance training may lower relative muscle mitochondrial content via “dilution” of the organelle in a larger muscle fibre. Such an adaptation would reduce fatigue resistance, as well as compromise oxidative ATP synthesis and the capacity for fatty-acid oxidation. We investigated the effect of resistance training on mitochondrial enzymes of the citric acid cycle (citrate synthase; CS) and β-oxidation (β-hydroxyacyl CoA dehydrogenase; β-HAD), as well as markers of the potential for glucose phosphorylation (hexokinase; HK) and glycolysis (phosphofructokinase; PFK). Twelve untrained men (21.9 0.5 y; 1.79 0.03 m; 83.2 3.2 kg) participated in a 12 week progressive resistance-training program. Muscle biopsies were taken from the vastus lateralis before (PRE) and after (POST) training. Training increased mean muscle fibre cross-sectional area (p < 0.05) and the activities of CS (PRE = 4.53 0.44 mol·kg protein–1·h–1; POST = 5.63 0.40 mol·kg protein–1·h–1; p < 0.001) and β-HAD (PRE = 2.55 0.28 mol·kg protein–1·h–1; POST = 3.11 0.21 mol·kg protein–1·h–1; p < 0.05). The activity of HK increased 42% (p < 0.05), whereas the activity of PFK remained unchanged. We conclude that resistance training provides a stimulus for improving muscle oxidative potential, as reflected by the increased activities of CS and β-HAD following resistance training induced hypertrophy.


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