This type of fibre contracts quickly and is useful for rapid movements such as sprinting.
Fast vs slowĬhimps possess about twice the amount of “fast-twitch” muscle fibre. However, they did find key differences in the length of the fibres – chimp muscle fibres tend to be longer than corresponding ones in humans – and in the distribution of different muscle fibre types. “What we found was that there was really no difference in the fundamental contractile properties of chimp muscle fibres and human muscle fibres, for any of the individual fibres,” Dr O’Neill said. “We really wanted to get a handle on the basic properties of chimpanzee skeletal muscle – and find out whether they were different from those of human muscle,” he explained.Īlong with cardiac muscle and smooth muscle, skeletal muscle is one of the three main muscle types, and is mostly found attached to bones via the bundles of collagen known as tendons. “It was something we needed to do before getting into the substance of our paper.”Īccording to ideas put forward in previous work, the difference might be accounted for if chimpanzee muscles were able to generate more force per area, or, alternatively, if chimp muscle was able to shorten faster than human muscle – helping increase its power output.ĭr O’Neill and his colleagues set out to test these ideas and others, by directly measuring the properties of muscle fibres taken from chimps that had been frozen after death. “My sense of it was there had not been a critical review of all the experiments that had been done up until our study,” Dr O’Neill told BBC News. Writing in PNAS journal, Dr Matthew C O’Neill, from the University of Arizona College of Medicine-Phoenix, and colleagues reviewed the literature on chimp muscle performance and found that, on average, they are 1.5 times more powerful than humans in pulling and jumping tasks. In the 1920s, anecdotal evidence along with investigations by the biologist John Bauman, helped feed a perception that chimps were between four and eight times stronger than an adult human.īut subsequent studies failed to replicate these figures, as later researchers found that chimps did not greatly outperform adult males when given physical tasks. The findings do not support previous work suggesting mechanical aspects of chimp muscles are responsible.īut the difference in chimp-human muscle performance is more modest than sometimes depicted in popular culture. The greater strength of chimpanzees, relative to humans, may have been explained by American scientists.Ī study suggests the difference is mostly due to a higher proportion in chimps of a muscle fibre type involved in powerful, rapid movements.
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