Many students of strength find their grip to be the bottleneck in their progression towards swinging a heavier kettlebell with one arm.
In the one-arm swing, the static strength endurance of holding on to the kettlebell is a very different animal from the power endurance of the lower body. In the latter, alternating cycles of tension and relaxation enable blood to flow. In the former, prolonged tension shuts down the circulation and makes the gripping muscles fatigue rapidly. As the intensity of an isometric contraction increases, the blood vessels get squeezed shut. They get fully occluded around 50% of your maximal strength.
Thus, provided that you already grip the bell loosely and correctly, as explained in Kettlebell Simple & Sinister, you have several ways to improve your ability to hold on to it as it gets heavier: Intermittently relax your grip during a set Improve your grip strength Improve your grip strength endurance
Today we will focus on item number one: find a way to sneak muscle relaxations into a set of swings. Relaxing your fingers and letting go of the kettlebell even briefly is a lot more effective than one would imagine. Soviet scientists discovered that during the relaxation following an isometric contraction circulation rapidly increases 12.5 times! A burst of oxygenated blood is a game changer for your grip endurance.
Once your swings are looking good—meeting the Kettlebell Simple & Sinister technical standards—start practicing totally releasing your grip on the top of a rep, when the kettlebell is floating.
When the bell starts to pendulum down, barely hook its handle with your fingers. Grip harder when the kettlebell is about to reach the bottom of its trajectory. Be ready to drop the bell, so practice outside. First, get the drill down with two-arm swings, then one-arm ones. Start light, then go heavier. | 
