A single bout of resistance exercise is all it takes to stimulate the synthesis of new muscle proteins, which is why bodybuilders undertake chronic weight training to enhance muscle growth; a process known as hypertrophy. However, there are many variables within weight training that can be modified to potentially maximise hypertrophy. Training at low intensities with an occlusion device as well as training at low intensities to muscular failure can produce comparable results to conventional high-intensity low repetition weight training. Another variable is the time that a muscle is under load throughout a given exercise. This relates to the speed of the eccentric and concentric phases of the exercise. Some theories stipulate that it is important to perform the eccentric phase slowly and the concentric phase quickly, while other say both phases of the exercise should be performed slowly.
Slow Eccentric and Concentric
In a study published in The Journal of Physiology in 2012 researchers set out to examine whether unilateral leg extension exercise at 30% of one-repetition maximum (1RM) with a slow lifting movement (6-sec up and 6-sec down) performed to fatigue produces greater increases in rates of muscle protein synthesis than the same movement performed rapidly (1-sec up and 1-sec down)5.
Weight Load and Volume
The slow and fast groups both lifted the same weight in each unilateral leg extension exercise (i.e. 31kg) and performed the same number of reps for each set, namely, 12, 7 and 6 for sets one, two and three respectively5. Both groups rested for 2-minutes between each set. However, as one would expect, the time taken to perform each set was where the major difference occurred. In the slow group, leg muscle was under tension for 198, 119 and 90-seconds for sets one, two and three respectively. While in the fast group, on average, leg muscles were under tension for 25, 14 and 11-seconds for sets one, two and three respectively5.
Time Under Tension Important
In a nutshell, researchers found the slow lifting resistance exercise resulted in a significantly greater increase in muscle protein synthesis (i.e. 2.3-fold) compared with the fast group5. The results suggest that the time the muscle is under tension during exercise may be important in optimising muscle growth. Until this study was conducted exercise physiologists did not know whether increasing the time that muscle is under tension would lead to greater increases in hypertrophy. It remains to be seen whether very slow eccentric and concentric movements using a heavy weight of 70-80% 1RM will produce similar results. However, these preliminary findings provide some interesting food for thought. It's certainly worth trialling this model of training if one is looking for novel ways to break up their training regime.
1. Fujita S, Abe T, Drummond MJ, et al. Blood flow restriction during low-intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis. J Appl Physiol. 2007;103:903–910.
2. Abe T, Kearns CF, Sato Y. Muscle size and strength are increased following walk training with restricted venous blood flow from the leg muscle, Kaatsu-walk training. J Appl Physiol. 2006;100:1460–1466.
3. Moore DR, Burgomaster KA, Schofield LM, et al. Neuromuscular adaptations in human muscle following low intensity resistance training with vascular occlusion. Eur J Appl Physiol. 2004;92:399–406.
4. Takarada Y, Sato Y, Ishii N. Effects of resistance exercise combined with vascular occlusion on muscle function in athletes. Eur J Appl Physiol. 2002;86:308–314.
5. Burd NA, et al. Low-load high volume resistance exercise stimulates muscle protein synthesis more than high-load low volume resistance exercise in young men. PLoS ONE. 2010;5(8):e12033.