Research shows that the positive portion of a rep (the lifting of the weight) should be done as fast as possible to engage the greatest number of muscle fibers and build strength, speed and size. It also suggests that just the opposite should be done for the negative, or lowering, phase of a rep.
Slow It Down
Try slowing down the eccentric part of every rep. Focusing on controlled rep speed is known as tempo, or time under tension, training; and the benefits are numerous. Making muscles work longer under high tension creates more muscle trauma, leading to greater muscle growth in response. It also poses a challenge to your stability and core strength, as you’re being forced to remain upright with a rigid torso under load. Of course, longer, more tiring sets mean improved conditioning and greater caloric expenditure.
While there is a strong endurance component to tempo training, the effect isn’t the same as just doing more reps. Heavy weights can still be used, and making your muscles work harder during their eccentric contraction is where they gain the most benefit when it comes to adding size to your frame.
On squats, for instance, perform 3–4 sets of 6–8 reps, taking 3–5 seconds to lower your body. Remember, however, to explode upward during each concentric phase.
Slower tempos will immediately reveal any flaws in your exercise technique, and they’ll expose weak muscles. For example, if your knees start to collapse inward as the result of a slow descent on the squat, your glutes aren’t firing hard enough. you need to be cognizant of pushing your knees out and sitting back more as you squat down.
Jim Smith is a highly respected, world-renowned strength and conditioning coach. A member of the LIVESTRONG.com Fitness Advisory Board, Jim has been called one of the most "innovative strength coaches" in the fitness industry. Training athletes, fitness enthusiasts and weekend warriors, Jim has dedicated himself to helping them reach "beyond their potential." He is also the owner of Diesel Strength & Conditioning in Elmira, NY.