This was not the article I read since it seems to be only several days old...and doesn't say the same thing I was implying anyway...but is interesting to the discussion none-the-less
https://phys.org/news/2017-06-chimpanzee-super-strength-human-muscle.html
The idea I was thinking of was that in humans more nerves service the muscle fibers (which is believable given our much larger brains.) This makes it less easy to contract all muscle tissue simultaneously. I will say that when a jolt of adrenaline hits humans can achieve impressive feats of strength.
You seem to be of the relatively antiquated idea that humans are not apes. I learned that we are, and it makes perfect sense to me. In fact, I'm of the understanding that humans and chimps are more closely related than are chimps and gorillas. That is to say, the divergence was farther back time-wise on an evolutionary tree.
As for the 98% similar genome, I believe that a 0.1% change would be perfectly sufficient to produce a vastly different muscular pattern. The function of DNA in protein synthesis is such that genome percentages are not a terribly meaningful metric when it comes to defining physiology.
Currently it is in vogue to shit-talk humans, consider ourselves inferior in all ways, and generally engage in self-loathing. As I understand things, humans are uniquely good at long duration running and it is probably and artifact of being evolved for 'endurance hunting.' That is, running game such as large ungulates to exhaustion. From a physical fitness point of view I find that 'something to be proud of' so to speak.