ABCbodybuilding - View Single Post - Conflicting reports on MPS refractory period
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Old 03-27-2014, 01:07 AM
BigFitness BigFitness is offline
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Originally Posted by nexus View Post

3 hours of MPS vs. 24 hours of MPS are both conflicting and vastly different values. There must be something I'm missing, can anyone shed any light on why this might be?
Actually I read that review yesterday! What you’re missing is Regulation of MPS by nutrition vs. Exercise nutrient interactions regulating MPS. The 3 hour is related to nutrient intake regulation alone, meaning that if you intake a protein meal, protein synthesis lasts for about 3hours at a giving rate before returning to baseline, and you have to restart the system after some time (unknown?). However, nutrient x exercise changes the game, you can do it for 24h continuously if you keep providing EAA, no time breaks, before returning to baseline after 24-36h.

In the section “regulation by nutrition”:
“The time course of the feeding response with a saturable amount of protein is as follows. After a lag of around 30 min there is a large increase (∼3-fold) with MPS peaking around 1.5 h before returning to baseline by 2 h (Atherton et al. 2010) despite continued increased availability of circulating amino acids and sustained ‘anabolic signalling’ (Bohe et al. 2001; Atherton et al. 2010).”

In Bohe et al. it says “Rates of mixed MPS were not significantly different from basal (0.076 0.008% h_1) in the first 0.5 h of AA infusion but then rose rapidly to a peak after 2 h of ~2.8 times the basal value. Thereafter, rates declined rapidly to the basal value” (this is from Bohe et al. 2001, Latency and duration of stimulation of human muscle protein synthesis during continuous infusion of amino acids).

Meaning that nutrient stimulation alone increases protein synthesis rate (∼3-fold), and then after 2-3h it returns to baseline, it doesn’t stop, the rate decreases.

However with exercise “Regulation of MPS by acute exercise”:

"At intensities greater than 60% 1-RM, exercise increases MPS 2- to 3-fold (Kumar et al. 2009). The latency for lower intensity exercise (68 repetitions at 75% 1-RM) is <1 h (Kumar et al. 2009). After this latent period, MPS rises sharply between 45 and 150 min and may be sustained for up to 4 h (Kumar et al. 2009b) in the fasted state (limited by substrate availability), and in the presence of increased AA availability, up to and beyond 24 h (Cuthbertson et al. 2006).”

Meaning that it lasts longer (up to 4 hours vs. 2-3 hours) due to acute exercise stimulus, but still limited by the fasted state. Now when and if AA are available protein synthesis lasts even longer if you keep it going (24 hours or more). This is to say, the rate increases with acute exercise stimulus (the same 2-3 fold as with nutrition alone), but it lasts longer “the delaying of the muscle-full response appears to last at least 24 h (Burd et al. 2011) after a single bout of exercise,”

They say “In general, we believe that it is largely irrelevant whether the feed is given pre-, during or post-exercise” because “nutrient sufficiency per se, rather than timing of intake, is the more important aspect to successful hypertrophic adaptation (that is not to say some acute performance/recovery benefits may be afforded by consumption of nutrition in close proximity to exercise) (Ferguson-Stegall et al. 2011).

I believe they are mistaken when saying “largely irrelevant”, it’s less important than maintaining AA sufficiency for at least 24, but it’s not “largely irrelevant”. You can get them both, timing in close proximity to exercise and maintaining for 24h. Because breakdown is increased following exercise you need to balance it with synthesis for a slightly positive balance.
(But you can also stop breakdown to be even more positive, but that’s not done only with AAs, but also with insulin and or HMB, phosphorylation of the FoXO pathway, another subject)

You say “They seem to suggest that there is a delay in the refractory period for upto 24 hours after training. This would imply that there is no need to dose with BCAAs during the first 24 hours to re-initiate MPS.”

It doesn’t imply that, it implies that you can sustain MPS for 24 hours due to acute exercise with no breaks with sufficient AA availability, so there’s still a need to dose with BCAAs and Essential Aminoacids (EAA. You must sustain it with BCAAs and EAAs otherwise it will stop after 4 hours and you’ll be catabolic for 24 hours also at a higher rate, or at least catabolic until you get more EAAs. Acute exercise increases both the rate of synthesis and breakdown, if there’s no EAAs breakdown keeps going also at a higher rate to feed the muscle with muscle.
The only limiting factor in the 24h anabolic window is lack of EAAs and you have to intake them again and restart, but if you keep eating them MPS doesn't stop; on the other hand with nutrition alone (no exercise) it will stop after 2-3h anyway no matter if you keep pumping EAAs, "despite continued increased availability of circulating amino acids and sustained ‘anabolic signalling’". With exercise it will only stop after 24h-36h, unless there's a decreased availability of EAA, that's the diference. So keep feeding the muscle with proper doses of protein every 3h for 24h-36h at least.

“Muscle protein breakdown (MPB) exceeds muscle protein synthesis (MPS) in the fasted state, and MPS exceeds MPB in the fed state. In response to exercise, MPS is transiently increased whereas MPB also increases, or remains the same (the latter of which is on the proviso of sufficient exogenous nutrient supply; Kumar et al. 2009a). It follows that on a cumulative basis, increases in MPS after each exercise bout ‘drives’ adaptation to exercise training. (in the Background section)

“Increasing dietary EAA availability after exercise enhances both the magnitude and duration of the increase in MPS (Pennings et al. 2011). Therefore, in essence, exercise is able to pre-condition muscle to delay the muscle full ‘set-point’ (in Exercise nutrient interactions regulating MPS).

Makes more sense now? Hope so.

Last edited by BigFitness; 03-29-2014 at 05:15 AM.
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