I'm a 16 year old junior. 157 lbs 6'1'' 10-11% body fat. Problem is, my cardio is pretty weak (tennis cardio. I can run for a long period(Think 9.4-10.1 beep test) but tennis tires me out quickly in the high intensity drills. I'm thinking my legs need to have better explosiveness/endurance. What does talk tennis suggest. I squat 185lbs at 12 reps 3 sets(45 second break between sets). Havent tried for a max because I do it on my own. However that completely drains me for a few minutes.