A normal repetition takes about 2 seconds for the movement and 1 second to lock. There is way of exercising the muscles slower then normal, thus trigering heavier tention on muscular fibers in order to increse muscle growth. Slower repetitions have 15 to 17 seconds covering 4-6 repetitions.There are benefits from slower workout, but look out for unwanted injuries if unprepared.
Saftey first. When you performe slower repetitions he ocasional body swing that helps form time to time is to a minimum. Lets say barbell biceps curls – there is always a bit body swing when perfoming the repetitions on a heavy set. If you decide to do a slower set barbell bicep curl, make firm body bposition with a streight back and sligthly bendet knees. Concentrate on a firm postion in order to protect the back and weist.
Sets with slower repetitions require lighter weights. Moving lighter weights slower then usual can be tougher then normal repetitions. Stress on the muscles is longer then usual, thus activating more muscular fibers and metabolic byproducts(like lictic acid). But the sence and look of the muscles being pumped up doesn’t last long. So this sometimes acts on a motivational level, having the sence that pumping is a realistic result.
Because the muscular mass of slowr repetitions doesn’t last long, it is not recomendable that you practice slower sets too long. Have some rest after few weeks, or practice slower sets with some exercises or some muscular groupe, then switch.
Since seconds are increased in the repetitions, increase the pause seconds also. Take an additional minte inbetween sets to rest the muscles that worked slower and harder.