If we use sensors to see which parts of a muscle are working hardest during a workout, those same areas are the ones that will grow the most over time.

For female soccer players, how much your glutes 'light up' on an EMG machine during exercises doesn't necessarily match how much force they're actually producing — so the electrical signal might not tell the full story.

When guys who’ve never lifted weights before start training, their muscles get stronger partly because their brain gets better at telling the muscles to fire harder — but most of the strength gain still comes from the muscles actually getting bigger.

In resistance exercises, the biceps muscle shows greater electrical activity than the triceps muscle, whether it is doing the main work or opposing the movement, in healthy young adults aged 20–30.