Quote (cloudkicker @ Jan 5 2015 03:31pm)
Cardio training in general in combination with strength training will yield slightly subpar results in each aspect through chronic competitive down regulation of mTOR by ampk phosphorylation. The difference isn't crazy but you won't really be able to avoid the decrement in adaptation.
Nah, exercise training upregulates the alpha-2 isoform of AMPK which doesn't antagonize mTOR. That's why exercise possesses its robust repartitioning effect, concomitant activation of both of these myriad pathways doing ostensibly contradictory actions.
Beyond that, apart from like long-distance running I'd presume, HIIT and typical cardio exercise also upregulates mTOR. Albeit not nearly as much as strength training, it still also does activate mTOR. Has there been a study to test the effect of these groups we're mentioning and tested differential mTOR responses? None that I'm aware of, so I'm going to assume the difference is probably present but small and maybe even negligible. Besides, in general purely measuring rates of protein synthesis & mTOR levels aren't a proxy that's indicative of gains. There's also the influence of upstream mTOR kinases (Akt and Erk) that are anabolic on their own independently, as well as downstream mTOR players that may not be affected by the influence of cardio due to already being phosphorylated (p70s6k and 4E-BP1). Not to mention the satellite cell response that does correlate with longer time size gains in at least one study that probably wouldn't be quite as influenced I wouldn't gather (as many of the factors probably aren't as affected due to cardio).
All in all, unless doing excessive amounts of cardio I don't think it'd make a difference. Especially if said person stuck to HIIT and didn't do it literally daily pwo (I don't know it but the slight difference there is may accrete over time. It's too hard to say imo).