For maximum leg growth, the primary exercise should be the full back squat. No other lift even comes close to the muscle fiber activation created by squatting. Squatting also increases the amount of growth hormone the body releases.
An increase in growth hormone will not only increase leg size but you will have more full-body hypertrophy as well. Full back squats hit all the quadriceps muscles, the hamstrings, and the glutes which is why they are the king of all exercises.
However, squatting for the whole year might put too much pressure on the spine. A few spine de loading cycles should be implemented throughout the year to prevent this. For example, unilateral exercises can be used instead. That issue aside, here are the top exercises for complete leg development:
Get your heavy work done with functional movements like the squat and deadlift. These two exercises should be the cornerstone of any leg routine. Focus on correct technique on these exercises and your legs will start to change before your eyes.
Concentrate of Loose weights. Doing heavy weights on machine-based exercises can cause both structural issues such as patellar tendonitis as well as muscular imbalances
Add Lunges too
Add unilateral exercises such as lunges or single leg squats and single leg dead lifts to ensure that both legs develop evenly, minimizing any muscular imbalances
No, the 10-20 minutes on the treadmill/elliptical/bike do NOT constitute a proper warm up. Merely doing the cardiovascular warm up has done little to prepare your body for what is about to ensue. Always begin your session with a good 5-10 minutes of active stretching (movement based) then your stabilization work.
There are other exercises that isolate the quadriceps to a high degree such as Leg Extensions and Leg Presses and can be effective for Pre-Exhaust and Post-Exhaust Super sets when combined with one of the top 5 exercises.
Day 1: Cheat - Shoulder - Triceps
Day 2: Back - Biceps - Trapz - Upper Abs
Day 3: Rest
Day 4: Legs:
Warm up - 3 minutes spot walking,
3 minutes tread mill,
Calves Raises 3 sets x 20 reps,
Free Full squats 2 sets of 20 reps,
Back Squats 3 sets x 10 reps,
Leg Press 3 sets x 10 reps,
Lunges 2 sets x 10 reps,
Leg extensions 2 sets x 10 reps,
Leg Curls 2 sets x 10 reps
Leg Raises 2 sets x 20 reps,
Hanging Leg Raises 2 sets x 10 reps
Day 5: REST
Day 6: Same as day 1
Day 7: Same as Day 2
Day 8: REST
Day 9: Same as day 4
All the best