A critical component of both sports training and injury rehabilitation is strength training. A better understanding of the relationships between various training variables such as frequency, mode, volume and intensity is important to obtaining the best results in both arenas. A research team and the mLundberg Laboratory for Human Muscle Function and Movement Analysis in Sweden conducted a comprehensive review of relevant journals, books and reference lists in order to identify dose-response relationships for muscle hypertrophy induced by the different training variables. The results are published in the journal Sports Medicine.
In the review, the analysis was limited to the elbow flexors and quadriceps femoris, as the available literature only allowed dose-response evaluations for these muscle groups. Strength training modes included isometric resistance, dynamic external resistance, such as weight machines and free weights, and accommodating resistance including isokinetic and semi-isokinetic devices.
The review revealed that all three modes of strength training can induce significant muscle hypertrophy given sufficient intensity, frequency and volume of effort. There is currently no evidence that one mode or type of muscle action is superior over another. In terms of optimal training suggestions, the results suggest that two or three sessions per week is better than once per week, even when the volume of work is the same. In terms of intensity, there is a wide range of intensity levels that produce hypertrophy. However, higher intensities can produce hypertrophy more quickly. Current recommendations are intensity levels of 70-85% of maximum, with the caviat that hypertrophy can occur at both higher and lower intensity levels. Regarding volume, 30-60 repetitions per session seem to achieve the best response. However, with very high loads, such as 90% 1RM, high growth is found with 12-14 repetitions per session. However more research is needed in this area to confirm these results. Finally, in terms of rest periods, the review confirms the importance of rest days, particularly when maximum or near-maximum effort is employed.