Slow tempo training has been around for a while with a wide range of personas throwing different protocols around. Mike Mentzer was one of the first guys that made slow reps popular. The idea behind them is their difficulty, they work your muscle's time under tension more and lead to greater muscle gains.
The time under tension is the amount of time your muscle produces force. Let's take the bench press for example. When you lower the bar to the chest, it usually take around a second and then you push it back up in two seconds. This rep has a tension time of thee seconds: one second on the way down plus two on the way up for a total of three . Now say that you lower the bar for four seconds, and raise it for two, you double your time under tension.
Where things become interesting is the weight that can be used. If you did two reps of three seconds at 100 pounds, you could probably do 1 slower rep of six seconds at 115 pounds for the same time under tension. Hence slower reps allow you to go a little heavier stress your muscles more.
The other way to use slow reps is to work the muscles longer. In this aspect, you take lighter weights than usual and do longer reps, taking five seconds on the way down and on the way up for a total rep time of ten seconds. It is under this scope that the Superslow training protocol came to life.
I would like to stress here that this is only one of numerous different ways to stress your muscles and gain strength or muscle size.
So what exactly is Superslow training?
The method was developed by Ken Hutchins in the 1980s. It came about when he was studying women with osteoporosis. Seeing that their bones where potentially at risk, he wanted to find a way to challenge their muscles without compromising their bone health. Hutchins gave them extra light weights and increase the time under tension to fifteen seconds. From there, he trademarked the name and made it his protocol. The protocol has now been changed to twenty seconds per rep, ten seconds each way. Sets are meant to be between 60-120 seconds which is around 3-6 reps.
What does the studies show?
The first study looked at sedentary men and women with an average age of 53. The importance here being the term sedentary, meaning currently not engaged in any physical activity. This studied showed greater increases in strength using slow training.
The second study looked at sedentary women with an average age of 32. This study proved greater strength increase with normal speed protocol.
From these two studies we could conclude that the Superslow protocol is best for the sedentary older population. From a practical point of view, the only people concerned would be those coming back from an injury or those who suddenly start exercising.
Counter arguments to the Superslow training
I think that slow reps are good to work on endurance or rehab work, but don't challenge the muscles enough for absolute strength gains.
This protocol calls for sub maximal loads used for extended period of times. If the loads are submaximal, then the muscle adaptions will not be very high.
Superslow training is a valid training method for sedentary older adults. It provides a safer workout, with less momentum at the end of reps which is easier and safer on the joints.
Slow reps can have a place in anyone's training plans but the time under tension of reps shouldn't be as long as twenty seconds because the weight you will use will not be challenging enough.
My recommendation for slow reps is to play around with the various time parameters to find the most challenging one for you!