Changes

: Repeated '''exercise''' causes the [[muscle]]s of the [[heart]] to become stronger which allows the [[heart]] rate to be lower. A person with a low resting [[heart]] rate is able to pump [[blood]] more efficiently and can be described as more 'fit' than a person with a high resting [[heart]] rate.

: When [[muscle]]s are not provided with enough [[Oxygen]] they go into [[Oxygen Debt]] and begin producing [[Lactic Acid]] which builds up in the [[muscle]]s causing a [[stitch]]. [[Lactic Acid]] is [[toxic]] in large quantities so it is transported to the [[liver]] where it is removed from the [[blood]] and [[Detoxification|detoxified]] by turning it back into [[glucose]].