The potential role of the myosin head for strength gain in hypertrophied muscle

In recent years, there have been several viewpoints regarding the role of hypertrophy for increasing muscle strength. Although experimental data has yet to demonstrate a role for muscle growth on changes in muscle strength, it has been suggested that multiple lines of evidence, combined with theory, must be considered prior to drawing definitive conclusions on the role of hypertrophy for strength gain. There is evidence that a population of myosin motors with extremely low adenosine triphosphate (ATP) turnover exists in skeletal muscle. These myosins demonstrate motor heads that are folded back, in a helically ordered state, against the thick filament backbone, which does not allow them to readily interact with actin and generate muscle contraction. If the muscle protein accrued via hypertrophy were to promote an increase in the fraction of myosin heads that are unavailable for actin interaction, then this may provide some rationale as to why muscle growth following resistance training does not appear to contribute to adaptation in muscle strength. Herein, we discuss this hypothesis and the potential role of the myosin head for strength adaptation following resistance training.