Isometrics are a great way to train a desired athletic position, whether it is a volleyball player working on their defensive stance or a sprinter holding a track start. Isometric exercise in the training environment involves the static contraction of a muscle without any visible movement of the joints. At Sparta, we often hold a barbell at the knee level to ensure a safe and powerful back curvature before Olympic lifts are performed. What we did not expect were the beneficial effects these static holds have on the nervous system, particularly stiffness.
A 2009 study, out of University of Northhampton in the United Kingdom, made a novel discovery that isometric exercise actually caused a significant decrease in stiffness of the lower leg muscles. Such characteristics are crucial because tendon stiffness allows you to transmit force quickly, an ability known as the RATE of force development. This RATE is regulated by the nervous system and often results in a higher vertical jump or quicker ground contact times in sprinting. Such stiffness can also prevent injuries (see SpartaPoint 5/13/2009). Think of your muscles and tendons like a series of rubber bands. You don’t want your rubber bands to be too loose, they will be slow to respond to quick changes in direction or speed, and put dangerous amounts of stress on ligaments and other soft-tissues.
But like everything in life, you can have too much of a good thing. Some athletes, usually males who have made a lifetime of lifting heavy weight in a short range of motion, have become so stiff that they cannot stay on the ground long enough to apply the force needed to make movements smooth and graceful. This concept of enhancing performance through a longer contact TIME, is a biomechanical variable known as impulse (see SpartaPoint 11/3/10). Baseball pitchers with higher impulses tend to load and drive off the rubber in a more prolonged fashion and basketball players can keep a wider defensive stance with ease.
So if you feel like you need to be smoother and require more TIME on the ground, try isometric exercise. We usually work our athletes up to heavier reps of 5-6 second holds in various positions and grips. You will be surprised that stiff exercise makes you less stiff.