[JAP] Exercise volume and muscle protein synthesis

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    [JAP] Exercise volume and muscle protein synthesis

    Resistance exercise (RE) volume is recognized as an important factor that stimulates muscle protein synthesis (MPS) and is considered, at least in part, to be involved in the mammalian target of rapamycin complex 1 (mTORC1)-associated signaling. However, the effects of relatively high doses of muscle contractions on mTORC1 and MPS remain unclear. In the present study, we used an animal model of RE to investigate the relationship between RE volume and MPS. Male Sprague-Dawley rats were subjected to RE, and muscle samples were obtained 6 h after performing 1, 3, 5, 10, or 20 sets of RE.

    Although one set of RE did not increase MPS (measured by the SUnSET method), multiple sets (3, 5, 10, and 20 sets) significantly increased MPS. However, the increase in MPS reaches a plateau after 3 or 5 sets of RE, and no further increase in MPS was observed with additional RE sets. In contrast to the MPS response, we observed that p70S6K phosphorylation at Thr389, a marker of mTORC1 activity, and Ser240/244 phosphorylation of rpS6, a downstream target of p70S6K, gradually increased with higher RE volume. The above results suggest that the relationship between RE volume and MPS was not linear. Thus, the increase in MPS with increasing RE volume saturates before p70S6K phosphorylation suggesting a threshold effect for the relationship between p70S6K activation and MPS.

    They had a group of male rats do resistance exercises for a different number of sets, waited six hours, and then took muscle samples. One set did not increase the amount of muscle growth, 3-5 sets did, but 10 and 20 sets failed to increase the amount further, suggesting that there's a 'saturation point' for muscle growth within a specific time period.

    Additional questions raised:

    1. Is this saturation point the same for humans as it is rats? Humans are much larger than rats and may have a much higher upper limit. It's possible that humans could see benefits up to 6 or 8 sets.

    2. What's the recovery time before the body will increase muscle protein synthesis again? This is difficult to tell because to take muscle samples, you have to take a chunk of muscle, which may alter the process.

    3. While MPS reaches a saturation point, mTORC1 continues to increase. mTORC1 controls protein synthesis in the body. Is there something else happening we're not aware of?

    Makes me kinda rethink doing multiple workouts in one day.


      Depends what the multiple workouts are.

      I tell my clients that they should take their muscles to maximum overload 2 to 3 times per week depending on where they are at in their exercise programme. With a warm-up set and a results set, at their max weight or 75% of their max weight and lift to failure. Then allow them to recover for 3 up to 7 days, depending on what they are training for.

      Essentially muscles can't count, the overload stimulates the protein development, while the recovery builds the muscle back up.

      Interesting reading this though.
      Thanks for posting this.


        So there is a capping effect but the synthesis does not decrease with bigger sets again?
        That's good news!


          I just want to see the rats doing the resistance exercises. That would be entertaining...