Weight training is the best solution. Four times per week, split system for more resting and recovery.
For beginners eight sets for each muscle group, 8-10 reps.
For intermediate 10 sets for each muscle group, 8-10 reps.
For advanced athletes 12 sets for each muscle group, 8-12 reps.
Add good quality supplements like: Multivitamins and minerals, 90% whey protein and L-glutamine. For advanced athletes add creatine.