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03.12.2016

Too intense strength training doesn't result in muscle growth

There are two schools of thought when it comes to bodybuilders' training. According to one, muscles grow faster if you push them hard during a workout. This philosophy says you have to surprise muscles or, even better, push them to the limit. The sorer the muscles afterwards, the better. If it hurts, it works, the saying goes. The other philosophy says that strength athletes should push their muscles, but they'll grow faster if they are not pushed to the limit. Always leave a little bit in the gas tank. According to a Brazilian study, the latter training philosophy is probably the right one.

Study
The researchers got ten young men, all of whom had not touched a barbell for at least six months, to train their legs by doing leg presses and leg extensions twice a week for 10 weeks.

In week 1 [T1], 3 [T2] and 10 [T3] the researchers took a small sample of muscle tissue from the vastus lateralis muscle just before, and 24 and 48 hours after the workout and studied it under the microscope. The researchers also took blood samples at the same time, measured the strength in the participants' legs and asked the men to indicate how sore their muscles were feeling on a scale of 0-10.

Results
The figure below shows that the muscle fibres in the vastus lateralis only showed growth in week 10. Nevertheless, the synthesis of muscle proteins [FSR] was higher in the first week, when the muscles were overcome by stimuli they weren't used to, than in weeks 3 and 10. This is shown in the second figure below.

The men had more creatine kinase in their blood after doing the workout in week 1 and 3 than in week 10. A high level of creatine kinase is a sign of muscle damage.

The men reported more muscle soreness in week 1 than in weeks 3 and 10, as the figure above shows. In addition, the men lost a considerable amount of muscle strength after their workout in week 1. The figure below shows this.

Conclusion
The cells in the men's leg muscles only started to grow when the men had become used to the training stimuli. Hypertrophy in the muscle tissue only started to occur once the men did not have sore muscles after working out, and once their creatine kinase levels were not spiralling high.

Of course strength training stimulates muscle growth, the Brazilians concluded. But not if the stimulus is too intense.

Source:
J Physiol. 2016 Sep 15;594(18):5209-22.

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