An ongoing debate related to resistance training is whether it’s better to do your reps quickly or slowly.
Some say it’s better to lift explosively, maximizing force production, while there’s a strong camp of people who believe you need to do your reps in a slow and controlled fashion, maximizing time under tension (TUT).
So, which side is right? The answer, as with most things in fitness, depends on your goals (and isn’t as clear as social media “experts” will have you believe). Keep reading and we’ll explain all you need to know.
Understanding Repetition Speed
Before we can determine which approach is "better," we need to establish what exactly constitutes fast or slow reps.
Rep speed is usually discussed using a four-digit tempo notation that breaks down each repetition phase:
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Eccentric (lowering)
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Pause at the bottom
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Concentric (lifting)
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Pause at the top
Fast reps typically follow a cadence like 1:0:1:0, meaning:
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One second to lower the weight
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No pause at the bottom
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One second to lift the weight
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No pause at the top
This would be a fast, explosive movement, like the quick, powerful movement of a clean and jerk in Olympic weightlifting or an explosive push-up.
Slow reps, by contrast, might follow a tempo like 3:1:3:1:
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Three seconds lowering
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One-second pause at the bottom
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Three seconds lifting
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Another one-second pause at the top
This tempo means a slower and more controlled movement, maximizing time under tension, where muscles remain activated for extended periods throughout each repetition.
Many believe that these different cadences lead to different training adaptations, including muscle recruitment, metabolic stress, and neuromuscular efficiency – and ultimately, provide different results in terms of hypertrophy (aka muscle growth) and strength gains.
Benefits of Fast Reps
Fast, explosive reps are believed to have several key benefits, such as improved strength gains and improvements for functional athleticism.
However, there are some potential downsides to this approach as well.
Let’s dive a little deeper.
Strength and Power Development
Fast reps recruit more fast-twitch (Type II) muscle fibers, which are responsible for explosive strength and power.
These fibers are essential for Olympic weightlifting, powerlifting, and any sport requiring maximal force output.
Thus lifting quickly may allow you to generate greater force and lift heavier weights, leading to stronger muscles.
Improved Athletic Performance
Many sports require explosive movements, such as sprinting, jumping, and cutting.
Training with fast reps enhances rate of force development (RFD), which is believed will improve overall athletic ability and functional strength.
Neural Adaptations
Fast reps train the nervous system to fire more motor units efficiently, leading to better muscle recruitment.
This results in stronger, more coordinated movement patterns, which are critical for high-performance training.
Potential Drawbacks
Opponents of fast rep cadences say the increased momentum can mask form issues and potentially increase injury risk, especially with complex movements like deadlifts or squats.
Additionally, relying solely on fast reps might shortchange your hypertrophy (muscle-building) potential due to reduced time under tension.
Many novice lifters also struggle to maintain proper technique when moving weights quickly, which can reinforce poor movement patterns.
Benefits of Slow Reps
Here are the purported benefits of slow reps, as well as the potential downsides of this style of training.
Increased Time Under Tension (TUT) for Hypertrophy
By increasing time under tension (the total duration your muscles work during a set) slow reps may create greater metabolic stress and mechanical tension, two primary drivers of muscle hypertrophy.
A typical set may take 4x as long to complete, dramatically increasing the stimulus for muscle growth.
This extended tension forces your muscles to adapt by increasing in size to handle the prolonged strain.
Better Mind-Muscle Connection
A controlled tempo allows for greater focus on muscle contraction and form.
When you slow down your movements, you become more aware of which muscles are working and how they're being engaged.
This heightened proprioception (body awareness) can lead to better muscle recruitment patterns and more targeted stimulation of the intended muscle groups.
Lower Injury Risk & Joint Health
The controlled nature of slow repetitions typically reduces the forces placed on joints and connective tissues.
Without momentum to mask weakness or compensations, you're more likely to identify and address form issues before they lead to injury.
This makes slow-rep training particularly valuable for those with a history of injuries or joint problems.
Potential Drawbacks
The primary downsides to slow-rep training are practical ones.
Workouts take longer to complete, and you'll typically use lighter weights than with explosive movements.
This can be mentally challenging for those who equate heavier weights with better progress.
Additionally, exclusive focus on slow reps might limit development of power and explosive strength needed for many sports and daily activities.
How Rep Speed Affects Different Training Goals
Most believe that different approaches have different benefits, based on your training goals.
For Strength and Power
When training for strength and power, faster reps are generally accepted as being more efficient.
For this type of training, you’ll typically want to focus on weights in the 80-100% of your one-rep max range, moving them as explosively as possible while maintaining good form, to maximize neural drive and fast-twitch fiber recruitment
For Muscle Growth (Hypertrophy)
It’s often claimed that slower tempo lifting is better for hypertrophy.
Slow, controlled reps result in more time under tension, and greater metabolic stress and overall muscle fiber recruitment, which some studies find result in increased muscle growth.
For Endurance and Fatigue Resistance
If you’re looking to build muscular endurance, moderate to slower repetition speeds with lighter loads (50-70% of max) tend to be most effective.
These protocols improve your muscles' ability to sustain effort over time, with extended periods of tension that’s applicable for endurance athletes or those in professions requiring sustained physical effort.
For Fat Loss and Conditioning
Both fast and slow rep methods can contribute to calorie burning and fat loss, albeit through different mechanisms.
Fast reps in high-intensity interval training (HIIT) or circuit workouts help burn calories quickly and improve cardiovascular conditioning.
Slow reps, on the other hand, ensure sustained muscle engagement and caloric expenditure.
Ultimately if the end goal is calorie expenditure and cardiovascular health, you can achieve similar benefits with a range of different approaches.
What Does the Science Say?
While there are camps that claim both fat reps and slow reps as the clear winner, if you're looking for a definitive scientific answer to settle the fast versus slow rep debate, you might be disappointed.
Research on optimal repetition speed presents conflicting findings. This is true even for strength, power and muscle growth as goals.
For example, one 2022 study found that high-TUT training was better for skeletal muscle endurance, hypertrophy, and strength.
Yet this study from 2023 found that both fast and traditional velocity training was better for muscle strength than ISVRE (intentionally slow-velocity resistance exercise) training.
Another study, from 2012, showed better muscle activation from fast-velocity training.
The takeaway? Both sides can point to scientific studies that back up their belief in slow reps or fast reps.
Final Thoughts: When to Use Fast vs Slow Reps
As you see from the findings above, there’s no scientific consensus over whether slow reps or fast reps are more effective.
Your key takeaway should be that it doesn’t really matter that much.
For most people, it’s not worthwhile to devote your energy and focus to figuring out the “right” way to lift.
What’s more important is that you train consistently, and achieve progressive overload (regularly increasing the intensity/volume of your workouts over time, in terms of weight, number of reps or duration).
As long as your form is decent and you’re not at risk of injury, you’ll get results with either fast or slow reps, as long as you hit those two principles.
It may make a difference for serious athletes or high-level lifters. But then again, each person’s body may respond differently, so even if the consensus shows one tempo is usually “better” than the other, you’ll want to try yourself to find out what works best for you.
