Faster reps vs slow reps: Why you should be using both in your program

When it comes to resistance training, the speed at which you perform each repetition can have a significant impact on the results you achieve.

Do fast reps or do slow reps? It can seem like a straightforward question, with an answer for each training quality.

• Lift fast when training for power
• Lift heavy when training for strength (but try to lift fast(er) on the up phase, and slowly control the down phase)
• Lift slow and with a deliberate controlled tempo for hypertrophy and muscle growth.

If you stopped reading here and just followed those three bullet points your lifting will go just fine!

However, there is a ton of nuance and intricate details in this question. The debate between fast reps and slow reps has been ongoing in the fitness community, with arguments for both sides.

In this post we'll explore the benefits, limitations, and use cases for faster reps and slower reps in your training, helping you make informed decisions to optimise your strength gains.

How to measure the speed of your lift

To understand whether fast reps or slow reps are better for developing strength, we first need to measure the velocity of your reps. This is commonly referred to as velocity based training (VBT).

Unlike load or reps which we can simply add up and count out, barbell velocity tracking requires specialised equipment in the form of a bar speed tracking app like Metric VBT.

The Metric app uses computer vision to provide real-time feedback about your lifting performance, while tracking tempo, range of motion, and the mean/peak velocity of all your reps.

It also automatically calculates your estimated one-repetition maximum (e1RM) during training and tracks progress on velocity, power, and load lifted through its built-in workout planner and training diary.

Metrics used when measuring lifting speed

In barbell velocity tracking, there are a number of valuable metrics you can collect and analyse with apps like Metric. For strength development we are really only worried about two.

Mean velocity (m/s)

This is the average speed of the barbell throughout the entire repetition, measured in meters per second. We will refer to this as just simply velocity and almost always when talking about velocity we are referring to the concentric portion of a rep (the up phase).

Tempo (seconds)

Tempo refers to the time taken to complete each phase of the repetition (eccentric, isometric, and concentric). Tempo can be valuable to track in all portions of the repetition, but for this article we will focus primarily on eccentric tempo.

What does it mean to lift fast?

Fast is a tricky term to define, and to decide if something is fast, we need to first determine faster compared to what?

There are two ways to define fast reps when it comes to lifting weights:

Absolute fast reps (power training)

This involves moving the bar as quickly as possible, regardless of the weight being lifted. Power training focuses on generating maximum force in the shortest amount of time.

Relatively faster reps (intent to move)

This involves trying to move each weight as fast as you are able to, attempting to accelerate the weights. According to the force-velocity relationship, force is equal to mass times acceleration, so the intent to move the weight quickly can lead to greater force production.

Move each weight as fast as you are able to, try to accelerate the weights. Force is mass * acceleration so higher.

Are faster reps better for strength?

In terms of absolute speed, faster reps are not necessarily better for strength. If your reps are too fast (e.g., above 0.8 m/s for most exercises), the load on the bar is likely too light, and you may be below the 80% of 1RM minimum typically recommended for strength development.

To get strong, you should be lifting heavy weights, which will inherently move more slowly due to their mass. However, this doesn't mean bar speed is irrelevant. You should still try to lift these heavy weights with a high intent to move, attempting to accelerate the bar as fast as you can to apply maximum force and challenge your largest type II muscle fibres via the Henneman Size Principle.

What is the best rep speed for strength?

There is no perfect velocity for developing strength, as it varies by individual and exercise. However, as a general guide:

• For most barbell lifts (e.g., squats, trap bar deadlifts, barbell rows), the strength zone typically starts at a mean velocity of 0.65 m/s or slower.
• For bench press, overhead press, and sumo deadlifts, the strength zone starts at a slower velocity, likely around 0.55 m/s and slower.

These are only indicative values, and your velocities may vary. Typically, the stronger you are, the slower your reps will need to be to achieve a strength stimulus due to a concept known as neuromechanical efficiency.

Measuring progress on strength in the gym.

There are three ways to make progress and measure increases in your strength:

1. Increase the weight you can lift: Lifting more weight over time is a clear indicator of improved strength.
2. Increase the number of repetitions you can lift a weight for: While going from 12-15 reps may primarily indicate endurance adaptations, increasing from 3-5 reps suggests improving strength.
3. Lifting the same weight but at a faster mean velocity: If you lift 100kg at 0.4 m/s one week and then 0.43 m/s the next week, this indicates increasing strength levels.

Contextual velocity

The idea of improving your own velocity on each exercise is called contextual velocity—your ability to move weights faster today than you did last week. Comparing your own performance and bar speed over time can provide valuable insights into your strength progress.

When slow reps might be beneficial for strength?

Slow reps can be beneficial for strength gains in certain contexts. Controlling the pause, working through the sticking point, and slowing down the eccentric (lowering) phase can all contribute to strength development. These techniques prevent the lifter from bouncing the weight and relying too heavily on their elastic muscular qualities.

Fast and slow reps by contraction type - eccentric, concentric and isometric

This is where things start to get even more nuanced. To lift weights fast, really depends on the direction the barbell is moving and the type of contraction you are performing. Often the way you should try to lift a weight wil vary drastically between the lowering and the raising phases.

Eccentric contractions - Do this part of the rep slowly

The eccentric phase of a lift, also known as the lowering or negative phase, is when the muscle is lengthening under load. Performing this part of the rep slowly can lead to greater muscle damage, stimulating hypertrophy and strength gains. Slow eccentric reps are particularly useful for exercises like squats, bench press, and pull-ups.

When to perform fast eccentric reps

Fast eccentric reps may be appropriate in certain situations, typically these instances are reserved for field sport athletes developing their brakes and load absorption capacity. For example a basketball or volleyball athlete who jumps a lot might do deliberately fast eccentrics on a squatting type movement in order to improve their ability to control and absorb landing forces.

Plyometric exercises, like depth jumps or medicine ball throws, often involve rapid eccentric contractions followed by explosive concentric contractions.

There are methods where doing these eccentrics with loads on barbell exercises is possible however these are quite advanced and can be risky if programmed incorrectly or done without coach supervision.

Concentric contractions - Do these as fast as you can for the weight

The concentric phase of a lift, also known as the up or positive phase, is when the muscle is shortening under load.

Applying high levels of intent to move on the concentric portion of your working sets is almost always the superior approach when developing strength. Performing concentric reps as fast as you can, given the weight being lifted, can lead to greater force production and strength gains. This is particularly important for compound exercises like squats, deadlifts, and presses.

What is important here is to remember that fast is a relative term, when developing strength you still must be focusing on lifting heavier and heavier weights, but tracking velocity and trying to achieve new velocity records on all your heavy weights (and therefore lifting fast in comparison to your own lifting history) is the key.

When to do deliberately slow concentric reps

Deliberately slow concentric reps may be useful for exercises targeting smaller muscle groups or when focusing on form and accumulating time under tension.

Examples include bicep curls, lateral raises, or leg extensions. However, for the majority of compound lifts, the concentric phase should be performed with the intent to move the weight as quickly as possible.

You might also use a deliberately slow concentric phase of your repetition when learning a new exercise or when going through a rehabilitation or rebuild phase in your training.

How do you combine fast reps and slow reps

Incorporating both fast and slow reps into your training program can lead to well-rounded strength and hypertrophy gains. Here are some ways to combine them:

• Use slow eccentric reps followed by explosive concentric reps for exercises like squats, bench press, and pull-ups.
• Incorporate power-focused exercises with fast eccentric and concentric phases, such as plyometrics or Olympic lifts, into your training program.
• Use slow concentric reps for isolation exercises or when focusing on form and mind-muscle connection.
• Vary your rep speeds throughout your training cycles, focusing on power and explosiveness in some phases and controlled, slower reps in others.

Both fast and slow reps have their place in a well-rounded strength training program. By understanding the benefits and limitations of each and applying them strategically, you can optimise your strength, power, and hypertrophy gains in the gym.

Remember to track your progress using an app like Metric VBT to dive into analytics and insights like mean velocity, eccentric tempo and estimated 1RM to ensure you are consistently challenging yourself and making progress over time.