Hello, I'm a not only a doctor but a fitness & bodybuilding lover also..well for bodybuilders there are not any definite checkups or timings, until & unless any symptoms appear..like pain in any specific movement or joint or anxiety & vertigo during workout. Still if you want to go for any checkups it depends upon ur age,nutrition & previous history of any disease.for example- Lipid Profile test, blood  & urine routine,Sugar levels, Vit-B12 level & CT scan of the painful region etc. Hope it will help ur query.thanks :)