Reps: How Many Repetitions Should You Do?
A rep, or repetition, is one complete cycle of an exercise.
Perform a squat from standing, descend, stand back up and you've completed one rep.
Do that ten times and you've completed ten reps.
Those repetitions together make up a set.
Simple enough.
But how you perform those reps—and how many you choose to perform—can significantly change the demands of an exercise.
EVERY REP IS PRACTICE
The original version of this guide said:
"Every individual rep is a battle for good form."
I still like the sentiment, although I'd probably replace battle with practice.
Each repetition is an opportunity to practise the movement you're trying to perform.
That doesn't mean every rep needs to look absolutely identical or conform to some imaginary textbook definition of perfect technique.
Bodies differ.
Exercises differ.
And technique can change slightly as loads and fatigue increase.
Instead, aim for movement that is appropriate for the exercise, your body and the goal of the set.
If you're learning a new exercise, pay attention to the demonstrations and coaching cues you've been given.
As you become more experienced, good technique should require progressively less conscious thought.
THE DIFFERENT PARTS OF A REP
We can divide a repetition into several parts.
ECCENTRIC
The eccentric portion occurs when a muscle is producing force while lengthening.
Think about lowering yourself into a squat or lowering a dumbbell during a biceps curl.
This is sometimes called the negative portion of a rep.
CONCENTRIC
The concentric portion occurs when a muscle is producing force while shortening.
Standing up from a squat or curling a dumbbell towards you are examples.
This is sometimes called the positive portion of a rep.
ISOMETRIC
An isometric contraction occurs when you're producing force without meaningful movement occurring at the joint.
Pause at the bottom of a squat.
Hold a plank.
Stop a dumbbell halfway through a curl.
You're producing force while maintaining a position.
An exercise doesn't necessarily fit perfectly into a simple three-part sequence, but these terms give us a useful language for discussing movement.
They also become particularly useful when we prescribe tempo.
HOW MANY REPS SHOULD YOU DO?
It depends on what you're trying to achieve.
As a general rule, lower-repetition sets allow you to use heavier loads, while higher-repetition sets require lighter loads.
But I'd avoid treating rep ranges as completely separate physiological zones.
You may have seen charts suggesting something like:
1–5 reps = strength
6–12 reps = muscle
15+ reps = endurance
That's a useful simplification for understanding why programmes look different.
It isn't a biological rule.
REPS FOR STRENGTH
If your primary goal is maximal strength, relatively heavy loads and lower repetitions are particularly useful.
If you want to become good at lifting very heavy weights, at some point you need to practise lifting relatively heavy weights.
Lower-repetition sets allow you to do this without accumulating an enormous number of fatiguing repetitions within each set.
You'll also generally take longer rest periods so you can produce high levels of force again on subsequent sets.
That doesn't mean sets of 10 can't make you stronger.
They absolutely can.
They're simply less specific to demonstrating maximal strength than heavier, lower-repetition work.
REPS FOR BUILDING MUSCLE
Muscle growth isn't confined to a magical 8–12 rep hypertrophy zone.
Muscle can be built across a fairly broad range of repetitions provided the sets are sufficiently challenging and you accumulate an appropriate amount of training.
Moderate rep ranges are extremely popular because they're practical.
They allow you to use meaningful loads, accumulate useful training volume and get reasonably close to failure without every set taking forever.
But you can build muscle with sets of 5.
You can build muscle with sets of 15.
And you can build muscle with considerably higher repetitions too.
The number on its own doesn't determine whether a set builds muscle.
REPS FOR MUSCULAR ENDURANCE
Higher-repetition sets can be particularly useful for developing local muscular endurance—your ability to repeatedly produce force or maintain muscular work.
They also come with a very distinctive sensation.
The burn.
Learning to tolerate that discomfort is part of performing high-repetition work effectively.
But again, there isn't a precise repetition where your body announces:
"Right. Hypertrophy finished. Endurance starts now."
The adaptations overlap.
REP RANGES
Rather than always prescribing one exact number, your programme may give you a rep range.
For example:
8–10 reps
That gives us flexibility.
Imagine you perform:
60kg × 8
Over subsequent sessions you might progress to:
60kg × 9
then:
60kg × 10
Once you're comfortably reaching the top of the range at the intended level of effort, we might increase the weight.
Perhaps:
62.5kg × 8
Then the process begins again.
This is one simple way of applying progressive overload.
THE NUMBER OF REPS ISN'T THE WHOLE PRESCRIPTION
This is important.
Imagine two people perform:
100kg × 8
Person A finishes knowing they could have performed another five repetitions.
Person B finishes knowing they could perhaps have managed one more.
They've performed the same exercise.
The same weight.
The same number of reps.
But they haven't necessarily experienced the same training stimulus.
That's why we may also prescribe or record RIR — Reps in Reserve.
For example:
8 reps @ 2 RIR
means:
Perform eight repetitions using a weight where you estimate you could have completed approximately another two good reps.
This gives us considerably more information than simply writing:
8 reps.
YOU DON'T ALWAYS USE THE HEAVIEST WEIGHT POSSIBLE
This is another part I'd change from the original guide.
If I prescribe:
10 reps
that doesn't automatically mean:
Find the heaviest weight you can possibly lift ten times.
That would essentially turn every prescribed set into a test of failure.
Instead, the appropriate weight depends on the intended effort.
10 reps @ 3 RIR is very different from:
10 reps to failure.
Both have their place.
The programme should tell you what we're trying to achieve.
WHAT HAPPENS AS YOU FATIGUE?
Repetitions often change as a set becomes difficult.
They may slow down.
Your technique may change slightly.
Your perception of effort increases.
Eventually, you may reach technical failure or muscular failure.
That doesn't mean every difficult rep is automatically a bad rep.
A repetition taking longer because you're producing maximal effort against a heavy load is completely different from deliberately performing a slow repetition.
This is why rep speed and lifting tempo aren't quite the same thing.
You might be trying to move a heavy bar as explosively as possible.
It just isn't going anywhere particularly quickly.
QUALITY AND QUANTITY
Your goal isn't simply to accumulate as many repetitions as humanly possible.
The reps should serve the purpose of the exercise.
Sometimes that's:
Heavy, low-rep strength work.
Sometimes it's:
Moderate-rep muscle-building work.
Sometimes it's:
High-rep muscular endurance.
Sometimes it's:
Explosive repetitions performed with maximal intent.
Sometimes we're simply practising a movement.
Don't become so obsessed with categorising rep ranges that you forget the bigger picture.
IN CLOSING
A rep is simply one repetition of a movement.
But the number of reps you perform affects the load you can use and the demands of the set.
Lower reps generally allow heavier weights.
Higher reps require lighter weights and place greater demands on muscular endurance.
Muscle can be built across a broad range.
Strength can be developed across a broad range too, although heavier training becomes increasingly important when maximal strength is the goal.
And your prescribed reps only make sense when considered alongside load, effort, sets, rest and tempo.
There isn't a magical rep range.
Choose the reps that make sense for what you're trying to achieve.