Walking with back pain and not breathing

Chester does have back pain sometimes which Chester thinks might have been caused because he doesn't breathe when he exercises or swims.  This can result in a huge internal pressure buildup and is dangerous.  Or it could be because of his weight.  The reason Chester does not breathe is because Chester thinks that it is related to his meditation and affects his mind.  Chester is not sure about this one though.

Chesters back also hurts when he walks sometimes and the pain is unbearable.  Now either Chester is doing something very wrong when he goes swimming and weightlifting.  Chester did remember it only happened on the first day when he went swimming.  Is it because Chester does not breathe when he swims or is it the fact that his body is not use to swimming or exercising or aerobic workout like conditions?