Focus on load or repetition generates the same muscle mass – 05/30/2023 – Health

What else promotes muscle mass gain, a bodybuilding workout that emphasizes the load or the number of repetitions? According to a study carried out at Unicamp (State University of Campinas), whatever.

The researchers followed 18 individuals who underwent different training protocols over eight weeks. Part did exercise with higher weight and fewer repetitions, while the others did longer series and with less load. Muscle mass was measured in the first and last exercise sessions. When the two groups were compared, no difference was observed either in terms of mass gain or metabolic stress – measured by the analysis of substances released in the bloodstream after exertion.

In high-load training, participants carried up to 80% of their own weight. In resistance training, with low load, this percentage reached a maximum of 30%, but the repetitions were done until exhaustion (when the muscle no longer responds). The complete data from the survey, supported by FAPESP, were published in Metabolites magazine.

“Strength training is a recognized way to promote muscle growth. However, it is still not completely clear whether it is more efficient to value the load or the number of repetitions to achieve hypertrophy. Our study reinforces the theory that the two types of training work in a similar way. In addition, we were able to show that muscle activation occurs differently in each training session, but the metabolic stress is the same and, therefore, the hypertrophy result was the same”, explains Renato Barroso, professor from the Faculty of Physical Education at Unicamp.

In the assessments made during the first and last weight training session, blood samples were collected at three different times: before training, five minutes after exercise and one hour after. The collected material was submitted to a metabolomics analysis, whose objective is to identify the set of metabolites (products of metabolism) present in the circulation. Muscle activation was measured by an examination called electromyography, performed with electrodes capable of monitoring the electrical activity of the muscles in real time.

“What was expected was that in the group that trained with a low load, the metabolic stress responses were more exacerbated. This is because, in theory, this stress would compensate for the lower muscle activation. However, that was not what we found”, says Barroso.

Analyzes indicate that, although muscle activation was greater in the group that trained with higher loads, metabolic stress was similar in both groups. “This result suggests that, eventually, the two types of training, as they have very similar metabolic responses, can act through the same pathways to induce hypertrophy”, he says.

VARIATIONS

The metabolomic analysis detected the variation of 50 metabolites in the blood when the muscles were activated in both types of training. However, of the 50 metabolites selected, few showed any difference between the groups of volunteers. Of those few, the researchers analyzed six (asparagine, 3-hydroxyvalerate, acetoacetate, carnitine, creatine, and phosphocreatine).

Although the researchers found no difference in overall metabolic response, it was observed that some metabolites correlated with muscle hypertrophy in both training groups. According to the researchers, some of these correlations may be associated with the characteristics of the muscle fibers activated by exercise (type 1 or type 2) and also with the metabolic demand of the training protocols used in the study.

“Some studied metabolites come from anaerobic energy systems, produced by glycolysis [quebra da glicose] that occurs in muscle or by the breakdown of creatine and phosphocreatine – a process that provides enough energy to maintain an exercise intensity for a few seconds. Asparagine and acetoacetate are more associated with the Krebs cycle, which uses oxygen and nutrients such as fat, protein and carbohydrates to produce energy for the muscle and lasts much longer”, exemplifies Barroso.

Therefore, what is expected is that creatine and phosphocreatine are at their highest level when anaerobic metabolism is used. “This type of metabolism is a characteristic of type 2 fiber, a fast-twitch fiber. While asparagine, for example, could be found when the stage of cellular respiration known as the Krebs cycle is more activated, that is, a characteristic type 1 muscle fiber”, he explains.

Barroso points out that, during workouts that value load, type 2 muscle fibers are activated with greater predominance. “These muscle fibers have low oxidative activity but high glycolytic activity and may be more responsive to hypertrophy compared to type 1 muscle fibers. On the other hand, training that values ​​repetition may preferentially activate type 1 muscle fibers, that have low glycolytic capacity, but high oxidative capacity and are highly resistant to fatigue”, he concludes.

The article Serum Metabolites Associated with Muscle Hypertrophy after 8 Weeks of High- and Low-Load Resistance Training can be read at: