In the last decade more attention has been paid to the effects of speed of movement in strength training than ever before. It is against this background of research interest that the current obsession with rep speed has filtered down in to gyms and marketing departments and infused some individuals with a religious fervour.
One group with a clear view on what constitutes the “best” rep speed for building muscle are the disciples of SuperSlow®. SuperSlow® followers perform all their reps very slowly - taking around ten seconds to raise the weight and a further ten seconds to lower it. They do this in the belief that it “maximises safety, improves concentration of muscular effort and minimises momentum for better loading of the muscles” (1). The SuperSlow® group is headed by ex-Nautilus employee Ken Hutchins. In the 1970’s Nautilus founder Arthur Jones proposed a system of exercise in which the trainee performed one set of each exercise to the point of total fatigue, which he called “High Intensity Training”. He then used this system to market his Nautilus exercise machines and gyms. Since 1992 Ken has expanded this ethos of infrequently performed minimal amounts of work into the SuperSlow Exercise Guild through which he now offers instructor certifications in SuperSlow® training and a further line of exercise machines. There are many other principles involved in SuperSlow® but here I will focus on rep speed as it is by far the most popular tenet in gyms today.
So, what can we expect to gain by simply doing all of our exercises very slowly? Is it really the best way to build muscles, and what specific adaptations can we expect? First of all we must consider that the majority of published research indicates that adaptations to strength training are both load and velocity specific. Therefore if you were to use a slow rep count for several weeks you could expect to get “stronger” within the constraints of that slow rep speed but there would be little carryover of that strength to other speeds of movement.
By deliberately reducing acceleration you would not be producing much actual force nor attempting to do so until the very end of a fatiguing set so we would expect strength gains to be minor. We also must consider the inverse relationship between force production and intra-muscular tension. The slower we move a load the more time the body has to couple actin and myosin cross bridges and therefore the more tension is developed within the working muscle. Surely this is a worthwhile stimulus for muscular growth? Well, yes and no. The amount of tension that can be developed is ultimately still governed by the load, and of course the slower we move the smaller the available force and hence the lighter the load that must be used so there comes a point where the load utilised is just too low to develop any great amount of tension regardless of speed of movement.
This is relevant to muscle growth as the basic “recipe” for hypertrophy is load lifted x work done = cross sectional area. The guy’s and gal’s who lift the biggest weights for the greatest volume of work (total reps) usually have the biggest muscles. If I handed you a dumbbell and asked you to perform the greatest number of reps possible with a fixed weight would you do those reps with a ten second concentric and a ten second eccentric? Of course not! You would perform them at a smooth, natural tempo and that is what is really the “best way to build muscles”.
(1) SuperSlow of Scottsdale website.
