Reach one hand down your back from over your shoulder, and bring your other hand up your back from below. A good result is your fingertips touching or overlapping, then switch which arm is on top and check the other side. This checks how much your shoulder can rotate both ways, which is the range a throwing arm lives in. If it is tight, your arm cannot get into a safe throwing position, so you lose speed and the shoulder and elbow take the stress. A big difference between your two sides is a common warning sign in throwers.

Stand with your back, hips and head against a wall and keep your lower back flat on the wall. Raise both arms straight overhead and try to touch the backs of your hands to the wall, without your ribs flaring or your back arching off the wall. A good result is hands reaching the wall while your lower back stays flat. This checks how well you can get your arms fully overhead. If it is limited, your arm cannot get all the way up, so it drags low and late when you throw, which is a big cause of a tired, sore arm.

Sit up tall with your arms crossed over your chest. Without letting your hips turn, turn your shoulders to look behind you on each side. A good result is turning about halfway around (about 45 degrees) using your mid-back, not by twisting your lower back. This checks how well your upper back, the part between your shoulder blades, can rotate. If it will not turn, your arm has to make the power your body should, which costs speed and overworks the shoulder. Stiff rotation here is one of the most common problems in throwers.

Stand with your feet about shoulder-width, then squat down as low as you can with your heels flat on the floor and your chest tall. A good result is your hips dropping below your knees with your heels down and chest upright. This checks how well your hips and ankles move together, which is the base that starts every throw. If your lower body is stiff, the power has to come from your arm instead of the ground, which is slower and a lot harder on the shoulder and elbow.

Stand on your dominant-side leg with your eyes open and hold steady for 20 seconds, with no hopping, big wobbles, or grabbing anything. Want a tougher test? Try it with your eyes closed for 10 seconds. This checks the single-leg balance and core control your front (landing) leg needs to absorb force. If that leg cannot hold steady, your body cannot pass the power from the ground up through the chain, so your arm makes up the difference and both your control and your speed suffer.