Updated: May 8
So you are taking a strength training class and you've heard me or your trainer, slow your reps down. But your goal is to achieve that "toned" look and you've heard fast reps with light weights. I'm confused! Which is best? Truly it will depend on your goals but let's break it down and see which is right for you.
Before we breakdown the difference between slow and fast reps, you need to understand that there are 3 phases of movement. There's the concentric phase which is the lifting phase, isometric phase which is the hold of the movement, and eccentric which is the lowering phase of the movement. Tempo is the speed in which you move through the concentric and/or eccentric phases of movement.
Typically, with an exercise such as a bicep curl, you'll lift for 1-2 seconds, hold for 1 seconds, then lower for 2-3 seconds. This is a standard tempo. Slowing down your movement to 3-4 seconds lifting or lowering, increases your time under tension. The faster tempo you use, the less time under tension your muscles have. Each form of training serves a purpose.
When you increase your time under tension, more muscle fibers break apart and have to repair themselves. This is how you gain muscle size and strength. The more often you do this, the quicker you'll see results.
Taking this slower approach to strength training is also great for beginners. It allows you to focus on form first and then you can increase your speed or weights depending on your goals.
If lets say your goals are for speed, power and strength then fast reps are your answer. When you move through your time under tension faster, you challenge your muscles to tear and rebuild super quickly. Less muscle fibers are broken at this speed so it can take more time to increase muscle mass and strength. Faster reps are linked to more explosive strength such as shooting a basketball, swinging a bat, sprinting or jumping.
Combining the two
While both forms of training have specific outcomes, if your goal is general strength, combining the two is a great option. From time to time take a look at your speed and try changing it. Generally speaking, we all tend to have a "standard" pace for each exercise. Change it up and see if you notice a difference.
The bottom line
Both forms of training are great. If you goal is gain stronger muscles in a shorter amount of time, slow down your reps. If you goal is increase your explosive power, speed it up. If you want both, do both!