October 1, 1990Acta Physiologica Scandinavica
Myosin heavy chain composition of single fibres from m. biceps brachii of male body builders
Why the study?
Does body building alter the myosin heavy chain composition of single fibres in human skeletal muscle compared to a sedentary lifestyle?
Population
8 men, comprising young sedentary men and male body builders
Comparison
Body building vs Sedentary lifestyle
Design
Cross-sectional
Authors
Discussion
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Implication
Bodybuilding-associated MHC IIa predominance is observational only; leaves open causality and any performance or health implications.
Key Points
- To compare the myosin heavy chain (MHC) isoform composition of single muscle fibres in the biceps brachii between resistance-trained bodybuilders and sedentary controls.
- Obtained single muscle fibres from the m. biceps brachii of young sedentary men (mean age 28 ± 0.4 years, n = 4) and male bodybuilders (mean age 25 ± 2.0 years, n = 4).
- Analyzed MHC isoform distribution using one-dimensional electrophoresis and compared findings against traditional myofibrillar ATPase histochemical fibre typing.
- Bodybuilders had a significantly higher proportion of fibres expressing exclusively MHC type IIa compared with sedentary controls (36 ± 4% vs 12 ± 2%; P < 0.05).
- Bodybuilders exhibited significantly fewer coexpressing MHC IIa/IIb fibres (16 ± 3% vs 34 ± 2%; P < 0.05) and virtually no pure MHC type IIb fibres (1 ± 1% vs 12 ± 1%; P < 0.05).
- Myofibrillar ATPase histochemistry showed only non-significant trends toward higher type IIa fibres (31 ± 6% vs 25 ± 6%) and lower type IIb fibres (18 ± 5% vs 26 ± 6%) in bodybuilders.
Structured PICO
Does body building alter the myosin heavy chain composition of single fibres in human skeletal muscle compared to a sedentary lifestyle?
P
Population
8 men, comprising young sedentary men (n=4, mean age 28 +/- 0.4 years) and male body builders (n=4, mean age 25 +/- 2.0 years)
I
Intervention
Body building
C
Comparator
Sedentary lifestyle
O
Outcome
Myosin heavy chain (MHC) composition of single fibres from m. biceps brachiisurrogate
Body building is associated with an altered expression of MHC isoforms within histochemical type II fibres of human skeletal muscle, specifically an increase in type IIa and decrease in type IIb fibres.
Cite This Study
Klitgaard et al. (1990) studied this question.