Previous studies show that lifting to failure using 30% of your one-rep max (1RM) elevates protein synthesis the same amount as using 90% of your 1RM. In other words, absolute weight is not the determining factor for stimulating muscle growth. Instead, it appears it is the amount of time your muscles are under tension that’s the more effective stimulus for increasing muscle protein synthesis rates—and overall growth.
Defense
Explosive lifting stimulates type-II B fibers, which have the most capacity for muscle growth. During muscle contraction, motor units or muscle fibers are recruited in relation to the force generated by the muscle. Bodybuilders should lift as explosively as possible to grow bigger.
Prosecution
Time under tension stimulates greater muscle protein synthesis than traditional lifting. Bodybuilders should focus on muscle tension as opposed to just the amount of weight on the bar.
Evidence:
Numerous studies using resistance exercise training combined with blood flow restriction have shown that muscle hypertrophy occurs with a training intensity as low as 20% 1RM. This demonstrates that weight is not entirely responsible for muscle growth; other factors such as metabolic stress and time under tension are involved. In line with the type II fiber recruitment, recent studies show that moderate weights lifted until close to fatigue can stimulate protein synthesis to a similar extent as heavier weights. In a recent Canadian study, researchers instructed men to lift and lower the weight in either one second or lift and lower the weight in six seconds. The group that performed the leg extensions slowly with a tempo of six seconds up and down had greater increases in protein synthesis not only after exercise but also over the next 30 hours.
Verdict:
Time under tension stimulates greater protein synthesis: Lifting weights in a slow, controlled manner may be a more effective way of increasing muscle mass.
Sentencing:
Everyone wants to go into the gym and throw heavy weight around, yet the research clearly shows that lifting in a slow and controlled manner and really focusing on the muscle enhances protein synthesis. Just ask Mr. Olympia Phil Heath. When he trains, every rep is performed slowly and with perfect form. Heath is constantly talking about the purpose of “squeezing” the muscle while lifting and not jerking or bouncing the weight.
