Journal of Trainology



September 2012; Vol. 1, No. 2: Pages 28-31

Skeletal muscle hypertrophy: how important is exercise intensity?

Jeremy P. Loenneke


Current recommendations for training protocols aimed at increasing muscle mass are commonly based on a percentage of the concentric one repetition maximum (1RM) for a particular exercise. However, research utilizing lower exercise intensities (20-30% 1RM) has been observed to result in skeletal muscle hypertrophy similar to that of higher intensity resistance training. These findings appear to question the overall importance of exercise intensity for increasing muscle mass. Objectives: The purpose of this manuscript is to discuss the skeletal muscle hypertrophy exercise intensity recommendations and provide discussion on overall exercise volume, which is likely more important for stimulating skeletal muscle hypertrophy than exercise intensity per se. Design and Methods: Non-systematic review Results: It appears that a large portion of the exercise recommendations for skeletal muscle hypertrophy appear to be based on protocols that elicit short term changes in systemic ‘anabolic’ hormones; although little conclusive evidence exists to support that ‘anabolic’ hormone hypothesis. Exercise volume may be of much more importance for stimulating and maximizing the duration of the muscle protein synthesis (MPS) response than exercise intensity per se. In addition, chronic training studies confirm the acute findings that volume, not exercise intensity is the mediating factor for skeletal muscle hypertrophy. Conclusion: The data suggests that skeletal muscle hypertrophy recommendations on the basis of exercise intensity are too simplistic and more focus should instead be placed on total exercise volume. The current recommendations for muscle hypertrophy do not reflect current science.

Received July 16, 2012; accepted September 5, 2012