Often, people overlook the flexibility factor of vertical jumping. Being able to jump high is based on the elasticity of your muscles and tendons. Without having a high level of flexibility, you won’t ever really be able to jump as high as you potentially could – even with proper training to maximize your full capacity. Make sure that before you start any vertical jump training program that you take into account your flexibility and that you employ some basic stretching exercises and drills to help increase your static and dynamic flexibility.
The basic hamstring and quadricep stretches can be done easily and don’t take particularly long, they can be performed standing or sitting on the floor. There are many basketball training gadgets and accessories available to assist you with your stretching and flexibility routine – and to make it easier. The advantages of increasing your flexibility are not limited to just increasing your vertical though – being flexible will decrease the likelihood of injuries are reduce the chance for any muscle strains or tears.
Here are some basic stretches that you can perform easily:
To do the shin stretch, first start by kneeling in the above position and slowly sitting backwards onto your heels – place your hands behind you. Remember not to force this stretch. If you begin to feel any pain – ease up on the stretch. Hold the position for 20-30 seconds to stretch your shin tendons, muscles, and quads.
The quads can be stretched in many different ways, but all of them are essentially doing the same movement. Pull the heel of your foot gently towards your bum, your quads will feel a nice stretch. If you’re doing the stretch in the standing position you may need to lean against a wall or use some prop to help you stay upright.
The IT band stretch is for stretching the Ilitoral band that can be combined with a hip flextor stretch as follows: Sit down on the ground and with both of your legs out infront of you – pull your shin towards your chest. Holding this position for 15 – 30 seconds, then place your foot across your leg as in the above picture. Twist your torso and place your opposite elbow on your knee that is bent. The first part of the stretch is working on your hip extensors – the second part stretches your IT band and your back. Do both legs.
The hamstring stretch is easy and simple to do, lay on your back and gently pull you knee towards your chest, keeping your leg bent and foot in the air.
The side stretch, or groin stretch is done by standing in the above position with your hands on your hips. Lean to one side and bend this knee while keeping the other leg straight – keep both your feet pointing forward and do both legs.
The ab stretch is done facing down on the floor, place your hands on the ground infront of you and prop yourself up by extending your arms. Hold the position for 15-30seconds, this stretch also works your ab muscles.
The calf stretch is done by using a curb, or a set of stairs, or some elevated platform. Put the leg you want to stretch in the rear, with the toes just on the platform – and your other leg forward. Keep the stretching leg straight and hold for 15 – 30 seconds before you switch your legs.
Be warned though — stretch AFTER, not before your strength training or plyometric routine. Stretching statically before your exercises will decrease your power and strength for the next hour or so, meaning that you aren’t able to unlock all your power. If you must stretch BEFORE working out, then I suggest dynamic stretching as this does not decrease power or strength when working out.
Good luck 
-Will
