Many leg exercises, particularly compound leg exercises like squats and lunges, can be performed without equipment. When performing exercises without equipment for added resistance, it's important to make sure you're performing enough repetitions to take your muscles almost to failure. This means you may end up performing more repetitions per set than you would perform if you had dumbbells or other pieces of equipment. While you may think you can't see strength gains when performing exercises with light resistance and high reps, that's actually not true. As long as you're performing enough reps to take your muscles almost to failure, you'll enjoy strength gains from your workout.