Here is a recently published study.
1. J Appl Physiol. 2012 Apr 19. [Epub ahead of print]
Resistance exercise load does not determine training-mediated hypertrophic gains
in young men.
Mitchell CJ, Churchward-Venne TA, West DD, Burd NA, Breen L, Baker SK, Phillips
We have reported that the acute post-exercise increases in muscle protein
synthesis rates, with differing nutritional support, are predictive of
longer-term training-induced muscle hypertrophy. Here, we aimed to test whether
the same was true with acute exercise-mediated changes in muscle protein
synthesis. Eighteen men (21±1 yr, 22.6±2.1 kg•m(-2) means±SE) had their legs
randomly assigned to two of three training conditions that differed in
contraction intensity (% of maximal strength [1RM]) or contraction volume (1 or 3
sets of repetitions): 30%-3, 80%-1 and, 80%-3. Subjects trained each leg with
their assigned regime for a period of 10wk, 3 times/wk. We made pre- and
post-training measures of strength, muscle volume by magnetic resonance (MR)
scans, as well as pre- and post-training biopsies of the vastus lateralis, and a
single post-exercise (1h) biopsy following the first bout of exercise, to measure
signalling proteins. Training-induced increases in MR-measured muscle volume were
significant (P<0.01), with no difference between groups: 30%-3 = 6.8±1.8%, 80%-1
= 3.2±0.8%, and 80%-3= 7.2±1.9%, P=0.18. Isotonic maximal strength gains were not
different between 80%-1 and 80%-3, but were greater than 30% -3 (P=0.04), whereas
training-induced isometric strength gains were significant but not different
between conditions (P =0.92). Biopsies taken 1h following the initial resistance
exercise bout showed increased phosphorylation (P<0.05) of p70S6K only in the
80%-1 and 80%-3 conditions. There was no correlation between phosphorylation of
any signalling protein and hypertrophy. In accordance with our previous acute
measurements of muscle protein synthetic rates a lower load lifted to failure
resulted in similar hypertrophy as a heavy load lifted to failure.
PMID: 22518835 [PubMed - as supplied by publisher]
Of course you have to read the full text to see that these are untrained individuals...i.e. they do not lift weights. The authors make note however, that everybody prescribing weight lifting protocols for muscle hypertrophy are simply ignorant of the growing body of evidence showing that load doesn't matter as long as you train to failure. They use occlusion studies as their examples.
I try not to spout HST this and HST that all the time, but in this case it is surprising to me that academia is not recognizing the existence of a "threshold" for a loading stimulus to be effective. In addition, this threshold is a moving target. One HST principle I have repeated over the years is that the effectiveness of any load is dependent on the condition of the tissue at the time the load is applied. As the muscle tissue adapts to the previous loading sessions it pushes the threshold higher. Repeated training sessions cause the effective weight threshold to go up and reduces the effectiveness of any previous load.
So no, you don’t see a linear dose-response by simply increasing the weight load. The seemingly equivalent results from widely varying weight loads demonstrate a “threshold” effect. As with other threshold-type models, once the threshold is crossed you see diminishing returns as you push things higher. The same is true for weight; heavier doesn’t necessarily mean more effective. The only time heavier equals better is when you haven’t reached the effective weight threshold for your specific situation (i.e. level of conditioning).
Ok, I'm done with my rant now. I just hate to see data being interpreted by academics who apparently have no experience with weight lifting and hypertrophy. Sure, I might be going a little overboard with that but still, to say that weight doesn't matter as long as you try really hard (my flippant paraphrasing of this study's conclusions) is to ignore the repeated bout effect, progressive load, and a mountain of data showing that once a lifter has adapted to lifting, his/her muscle changes genotypically in such a way as to make further growth very difficult, necessitating an increase in the intensity of the stimulus (i.e. weight/volume).
Ok, now I'm done for real.