Swimming fitness is a broad versatile term. Not only is swimming great for cardiovascular capacity, but also, since swimming is low impact, it’s perfect for rest and recovery. The lack of impact with swim training allows the body to do a higher volume of training with less risk of acute injury. But in order to properly incorporate swimming into your workout, your strokes must be perfect.
An important point to consider is that all of the different swim strokes have one thing in common: shoulder rotation. The shoulder is one of the body’s most vulnerable joints. It’s a relatively small muscle group requiring multi-planar mobility and stability.
Unfortunately, the most common shoulder strength exercises—like Shoulder Presses, Raises and Flies—build up external movers, while doing little or nothing for the internal stabilizers. An acceptable swimming stroke requires maximum mobility and stabilization. Traditional exercises fail to teach the rotator cuff to stabilize the joint, and this can lead to injury.
Try adding the following rotary stability exercise to your strength and conditioning program. This out-of-pool strengthening drill will make a splash in your swimming results.

The Arm Bar

Lie flat on your back with your legs straight out and press a dumbbell or kettlebell straight up to the ceiling. “Pack” the shoulder down and back, squeezing like you are trying to hold a pencil in your armpit. Stretch the unloaded arm flat on the ground towards the far wall, and bend the leg on the same side as the weight.

Keeping your head on your unloaded arm, bring the bent knee across your body and to the ground while keeping the dumbbell or kettlebell fixed in the same position while you roll to your side.

Press your raised hip towards the ground, but don’t let the weight pull your arm back; keep it straight up in the air.
Pause, breathe and then roll back to starting position.