If young guys who already lift weights do intense leg workouts every day for two weeks, they get about 6% stronger in their leg press, showing their muscles and nerves adapt quickly.

If you train your legs with the leg press machine for 9 weeks, you’ll get stronger and your thighs will get bigger—even if you do it just once a week or spread it out over three days.

If young guys lift weights in a structured way for 10 weeks, eat about 1.8 grams of protein per kilo of body weight every day, and have supervision, they can get way stronger—adding around 80–85 kg to their leg press and 11–12 kg to their bench press max lifts.

If female college athletes who already lift weights add a specific workout plan and eat 24 grams of protein before and after each session, they’ll get way stronger in their legs—adding about 90 kg to their leg press max in just eight weeks.

When untrained young men lift heavy weights three times a week for five months, they get much stronger—some exercises more than double their original strength.

If you lift heavy weights (80–85% of your max) instead of doing lots of lighter reps (60% of your max), your legs get stronger faster — after 6 weeks, you’ll likely gain 5–6 kg more in leg strength.