Protein only builds strength if you are lifting as well
Across 82 trials, protein alongside strength training raised muscle strength by 2.01%. On its own it raised it by 0.13%, on an interval running from below zero to above it.
What the study found
Without resistance training, extra protein moved strength 0.13%
Eighty-two trials, pooled. Alongside strength training, more protein raised muscle strength by 2.01%. On its own it raised it by 0.13%, an interval running from below zero to above it. The dose-response climbs to about 1.5 g per kg a day and then stops.
The caveat · Mixes grip, lift and static strength
A null result is harder to establish than a positive one, and this one carries the weight of the finding. Strength was pooled across one-rep-max tests, isometric tests and handgrip, which do not always move together. The spline curves are smooth in a way the underlying trials are not. The search covered two databases.