When young women lift weights until they can't anymore, their arm and leg muscles get thicker by about 6-9% after 6 weeks. It doesn't matter if they lift heavy or light weights—both work the same for muscle growth.

When young women do strength exercises until they can't do any more, their arm and leg muscles get stronger by about 15-27% after 6 weeks. It doesn't matter if they lift heavy or light weights—both ways work just as well for building strength.

When young women lift weights until they can't anymore, using lighter weights gives about the same muscle growth as heavier weights over 6 weeks, with arms and legs both getting a bit bigger.

When young women lift weights until they can't anymore, using lighter weights or heavier weights leads to about the same muscle growth in their arms and legs after 6 weeks.

When young women lift weights until they can't anymore, using lighter weights or heavier weights doesn't make a big difference in how much stronger they get. Their arm and leg strength both go up about the same amount after six weeks.

When young women lift weights until they can't anymore, using lighter weights (30% of max) gives about the same strength gains as heavier weights (80% of max) over 6 weeks, with arms and legs getting stronger by similar amounts.