Which Are More Effective, Slow Reps or Fast Reps?

When it comes to slow vs. fast reps, you first need to understand the significance of repetition speed. In strength training language, repetition speed means tempo, or how fast you lift a weight or resistance. Tempo is demonstrated through both the eccentric and concentric part of a movement.

The concentric or lifting phase of a movement happens when you begin an exercise. It is the lifting part of the move. When you reach the top of a movement, which is called the isometric phase, you pause for about one second and then lower the weight to the starting position. This lowering phase represents the eccentric part of the movement.

For example, when doing a biceps curl, the concentric phase happens when you curl the dumbbell up towards your shoulders. After pausing at the top (isometric phase), you lower the weight slowly to the starting position, which represents the eccentric phase. Typically, the speed of this rep follows a one to two seconds up (pause at the top for one second), followed by a one to a three-second range when lowering the weight. Changing this tempo, to either a faster rep pace or slower rep pace, alters the goal of your workout.

Read more: The Ultimate Guide to Sets and Reps for Strength

Whether you're just starting out or you've been lifting weights for years, you might be wondering what the best workout is to build muscle fast. If your goal is hypertrophy or increasing muscle size, then focusing on slow reps to build muscle is a good place to start.

When you do a slow rep workout, your muscles experience a greater time under tension than they would if you were doing fast reps. Time under tension refers to the amount of time a muscle is under strain. This can lead to a greater increase in muscle size than faster reps which spend less time under tension.

Taking a slower approach to strength training while using lighter weights is also a safer approach for beginners. Slowing the tempo down allows you to focus on form and make sure you're doing the move correctly.

Read more: How Many Reps Are Needed to Build Lean Muscle?

If your fitness goals involve strength and power, then using a faster tempo may be more beneficial. According to a 2015 study published in Physiological Reports, participants that trained for eight weeks at a high intensity, low volume resistance program demonstrated increased bench press and lean body arm mass with fast rep resistance exercise training. While faster reps are generally linked to more explosive movements that result in power, training with this tempo can also produce gains in muscle size.

While both training styles serve a specific purpose, you can't go wrong incorporating slow and fast reps into your overall workout. According to a 2016 meta-analysis published in the Journal of Sports Medicine, using a fairly wide range of repetition durations is ideal if the primary goal is to maximize muscle growth. The bottom line is this: You will benefit from strength training with both tempos.