Skills - practice when you are not tired

The Effect of Muscle Fatigue on Position Sense in an Upper Limb Multi-joint Task

When your muscles are tired you are less able to sense where your limbs are in space.  Think of the implications of this for complex skills.  Trying to use complex skills as strengthening moves is risky.

That is why I favour big simple movements with low skill levels.  Skill conditioning is something different.  I apply this in Hillfit