It is always tempting to lower a barbell or dumbbell slowly, or hold a position for an extended period of time, as these protocols generally produce the burning sensation that conveys an idea of a more challenging workout. The impending soreness that occurs on the following day is a result of greater muscle damage, but not necessarily improved athletic performance.
The slow lowering portion of an exercise mentioned above is called the eccentric phase, while the holding aspect is called isometric. During the eccentric phase, a muscle is contracting, while being stretch simultaneously, creating greater muscle damage than normal. A 2008 study out of Edith Cowan University in Australia, one of the top sports science departments in the world, evaluated these eccentric effects on perhaps the most simple, athletic movement, a vertical jump (see Sparta Point 10/28/09). The study split 20 males into 2 different training groups, one using a braking method that stressed a slower eccentric phase and the other minimizing this portion.
While the power output in relatively slow movements improved more in the braking group, high velocity movements were improved more in the non-braking group. These results occurred because the braking mechanism, or a prolonged eccentric phase, decreases the speed of movement. In other words, there are velocity specific adaptations of training; train slow to move slow.
But the answer is not to run out and perform every movement as fast as possible, because each individual requires something different (see Sparta Point 1/27/10), and every exercise serves a unique goal. Some of you need more velocity to perform your sport at faster speeds, while others require a greater muscular stimulus found in the slower aspects of eccentric and isometric exercise. At Sparta, we use our force plate technology, similar to the study mentioned above, to diagnose our athletes’ needs, but a good coach and athlete instincts can never be ignored.
Regardless of your needs, it is generally best to not separate the phases of movement, by focusing solely on eccentric and/or isometric aspects. Sport movements do not occur in isolation, they generally emphasize the stretch shortening cycle (see SpartaPoint 10/19/09). Rather than separating phases, you can focus on perfecting a particular phase while performing a full movement. For example, some of our athletes work on relaxing towards the end of their squat for a faster eccentric speed, while others need a slower approach to keep the right posture.
So avoid searching for the right exercise for your particular sport, and focus more on adapting the speed of exercise to suit your needs.