You need to watch the speed of the workout when choosing drills and exercises for your training. Your program should take your individuality into account if you want to get the most "bang for your buck." This will be easy to understand if you compare the strength variables of any two athletes – no two are alike.
A common bodybuilding myth says that when weights are lifted fast more Type IIA and IIB muscle fibers are recruited. The reality is that fiber recruitment does not depend on speed, but on muscular effort. In fact, contrary to what most believe, fast type fibers can be used the most during certain slow movements. This is because as effort increases your movement speed is naturally going to decrease.
Slow training movements only produce improvement in low velocity exercises, while faster training movements produce almost the same results at both high and low velocity exercises. This does not mean that you should avoid slow, heavy training. However, the best way to increase muscle power is to train with faster movements. One method for developing muscle power is to use a moderate resistance and move it with fast, but controlled rhythm.
Lifting speed is one of the most important aspects of weight lifting; one that has a big effect on how much blood is targeted to your muscles. In strength training exercises for each muscle there are two different parts for each repetition of the exercise set performed. One, the concentric contraction, called the "positive" phase of the repetition, is the part where the muscle is actually doing the work, such as the lifting motion of the bicep curl – from the beginning where your arms are hanging straight down to the point where the weight is lifted up. The second part is the eccentric contraction, called the "negative" phase of the repetition, is the part with resistance, because you are returning the weight to the end of the positive phase back to the beginning.
If you want to build more muscle on the other hand, most authorities recommend contraction speed on the order of 4-10 seconds for one complete rep. This usually breaks down to something like 4 seconds to lower the weight, no pause, and 2 seconds to lift the weight. Do you ever see anyone lifting at those speeds in your gym? You can't lift nearly as much weight (at first) with such slow and deliberate movements, but you will be rewarded with bigger muscles and increased strength.
Lifting a weight gradually keeps it under tension longer which causes the muscle to work for a longer period of time. This is also easier on the joints and decreases the danger of injury slightly. Some experts advocate performing the eccentric phase pretty slowly, and then lifting the weight as fast as possible on the concentric phase. However, there are also plyometrics exercises that help develop strength and power by causing a greater load on the eccentric phase and taking advantage of the stretch shortening cycle.
So the idea of doing both slow and fast reps is good. Many reps by power lifters are slow – but not by choice of the lifter. Deliberately slowing down the rep simply lowers the number of motor units being fired, which is not a good idea if maximal strength is the goal. Power lifters must lift as explosively as possible to maximize recruitment, but the reps are relatively slow.
Exercise tempo refers to the amount of time it takes to perform a repetition. Fitness expert Charles Poliquin pointed out the natural trade-offs in contraction speeds in a 1988 article for the NSCA Journal:
In North America, there are conflicting schools of thought on the optimal speed at which strength work should be performed. One school advocates high velocity training, while another contends that strength gains can optimally be gained through only slowly performed repetitions. However, both schools are correct.
The topic of explosive weight training is one that has been at the heart of a maelstrom among strength and conditioning practitioners for quite some time. Explosive lifts include – but are not restricted to – the Olympic lifts (i.e. the snatch and clean and jerk), power clean, speed-squats, push jerks and any variation of these movements. There exists a preponderance of evidence indicating that explosive weight training movements carry a high risk of injury, both acutely and cumulatively, to muscle tissue, fascia, connective tissue and bony structures.
A study was done in 1993 and repeated in 1999 by Wayne Westcott, fitness research director at the South Shore YMCA in Quincy, Massachusetts. In both studies, Westcott assigned untrained volunteers to one of two regimens. One group did 10-12 regular speed reps (7 seconds: 2 seconds lifting, 1 second pause, 4 seconds lowering). The other group used a super slow training protocol calling for 4-6 reps of 14 seconds each (10 seconds lifting, 4 seconds lowering). Significantly, the slow lifters gained more strength than the regular-speed lifters – by 50 percent.
"Super slow" is a form of lifting that has been around for several years where each repetition is performed slowly. The case for training using slower repetitions revolves around a number of interrelated points:
- The difference between demonstrating and building strength
- The role of intensity in building strength and muscle
- How muscle fibers respond to intensity
- How to increase intensity and
- Specificity of training effects.
While it is true that explosively performed repetitions can be potentially more dangerous than low velocity movements, it's just as true that heavier weights, since they put more tension on the musculoskeletal system, are potentially more dangerous than lighter weights. It really becomes an issue of using the right tool for the right job. Too much stress on your system leads to injury, too little leads to little or no effect, just the right amount leads to a training effect.