Doing strength exercises with your muscle stretched out for 8 weeks can make the muscle fibers longer, but doing them with your muscle bunched up doesn’t change their length.

Doing strength exercises with your muscle bunched up for 8 weeks can make the muscle fibers angle more sharply, which might help them generate more force.

Doing 8 weeks of strength training with your muscle either stretched or bunched up doesn’t make you much better at resisting fatigue — the improvement is very small and not clearly real.

In men aged 69–70, performing supervised slow resistance training three times a week for 12 weeks leads to a small but measurable increase in the thickness of the patellar and Achilles tendons.

When people train with their muscles stretched out, the longer their muscle fibers get, the more quickly they tire out during repeated efforts.

If you're a guy who already lifts weights, doing full-body workouts five days a week will make your forearm and thigh muscles grow bigger than if you only work each muscle group once a week, after eight weeks of training.