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 you're a guy who lifts weights and gets close to failure—like stopping just 1 or 2 reps short—you'll get just as strong as if you pushed yourself to the absolute max. Over 10 weeks, both ways boost leg strength by 20–35%.

For women who already train regularly, increasing leg workouts from 22 to 34 sets per week for 12 weeks does not lead to greater strength gains in the leg press compared to 22 sets, suggesting that there is a point beyond which more volume does not improve strength.

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.