Does sunburn affect muscles?

Sun burn will not affect your muscle mass. To a certain degree, the sun provides the body with some essential vitamins. Generally when it is cooler out, your body will try to retain as much heat as possible. So what you may find in the cooler temperatures is that your muscles are not as juicy as they may seem in the warmer weather because in the warmer weather, your body has enough heat and it does not need to keep everything close together in order to keep heat in the body. Also in the heat we tend to drink much more water which helps the muscles as our bodies are composed of a lot of water. Plus we're far more active than we may even think during the warmer weather.