How can "social definitions of the body" be related to social relations? It sounds really abstract...Too much. This is a very tricky sentence to understand, if you just roughly understand what it means from the perspective of common sense, please let me know.
ex)The body has been viewed as a ‘natural’ phenomenon ― a fixed, unchanging fact of nature. Recently, however, it is also being seen as a part of culture in the sense
that it can be socially defined in different ways. Social definitions of the body are grounded in social relations and influenced by those with the power to promote agreement about what should be considered ‘natural’ when it comes to the body. This new way of thinking about the body has challenged the traditional mind-body split that has characterized Western thought since the time of Plato. It has also opened up new questions and issues in the sociology of sport. Some people in the sociology of sport are now working with colleagues in other disciplines who share interests in the body. In their work they are asking critical questions about how the body is trained, disciplined, and manipulated in sports and how some sport scientists are using technology to probe, monitor, test, evaluate, and rehabilitate the body as a performance machine.
It sounds to me like meaningless socio-psycho-babble.