Walk into any gym and you’ll see completely different approaches to training. One person is lifting heavy weights for just a few reps, while someone next to them is using a lighter weight for 12, 15 or even 20 reps.
So, who’s doing it right?
The answer is: potentially both of them.
When it comes to building muscle and getting stronger, both the weight you lift and the number of reps you perform matter. The trick is understanding when to prioritise each.
What Do We Mean by Reps and Weight?
A rep (repetition) is one complete movement of an exercise. If you perform 10 squats, you’ve completed 10 reps.
The weight is simply the resistance you’re working against.
Generally, the heavier the weight becomes, the fewer good-quality repetitions you’ll be able to perform.
But heavier doesn’t automatically mean better.
Heavy Weight vs Higher Reps
Different rep ranges can be useful for different training goals.
Heavier Weight + Lower Reps
Working with heavier resistance and fewer repetitions is particularly useful when your goal is to increase strength.
You might typically see sets in the region of:
3–6 reps
Because the resistance is heavier, you’ll normally need longer rest periods between sets.
Exercises such as:
Squats
Deadlifts
Bench press
Shoulder press
Rows
can all work well with lower-rep strength training.
Moderate Weight + Moderate Reps
If building muscle is your main goal, you’ll often see people working somewhere around:
6–12 reps
This is a very practical range because you can use enough resistance to challenge the muscle while still accumulating plenty of quality repetitions.
However, there is nothing magical about reaching exactly 8, 10 or 12 reps.
Muscle can be built across a much wider range of repetitions.
Lighter Weight + Higher Reps
Higher-rep sets — perhaps 12–20+ reps — can also be effective for building muscle when the resistance is sufficiently challenging.
They’re particularly useful for exercises such as:
Leg extensions
Lateral raises
Cable exercises
Bicep curls
Tricep extensions
Machine exercises
The key word here is challenging.
Doing 20 repetitions with a weight you could comfortably perform for 40 isn’t likely to provide the same stimulus as a set where the final few repetitions require genuine effort.
So Can Light Weights Actually Build Muscle?
You don’t necessarily need to lift extremely heavy weights to build muscle.
A lighter weight taken sufficiently close to the point where you couldn’t perform many more good-quality repetitions can still provide a strong muscle-building stimulus.
This is one reason varying your rep ranges can work so well.
You might perform a heavier compound movement earlier in your workout before moving onto moderate and higher-repetition accessory exercises.
How Do You Know If Your Weight Is Heavy Enough?
Here’s a simple question to ask yourself at the end of a set:
If you’ve completed 10 reps but could easily have performed another 10, the resistance probably isn’t particularly challenging.
If you’ve completed 10 and feel like you could have managed another 1–3 quality reps, you’ve likely created a much more demanding set.
You don’t need to reach absolute failure on every exercise.
The aim is to challenge yourself without allowing your technique to fall apart.
When Should You Increase the Weight?
This is where progressive overload comes in.
Your body adapts to training. If you repeatedly perform exactly the same workout with exactly the same resistance, eventually that workout becomes easier.
Imagine your programme says:
Incline Press — 3 sets of 8–12 reps
You start with a weight that allows you to perform:
10 / 9 / 8 reps
Over the following weeks you improve:
11 / 10 / 9
Then:
12 / 12 / 11
Eventually you achieve:
12 / 12 / 12
with good technique.
That’s a good indication that you may be ready to increase the resistance slightly.
Your repetitions might then drop back towards 8–10 — and you begin building them up again.
That’s progression.
Don’t Chase Weight at the Expense of Form
One of the easiest traps to fall into is believing every workout needs to involve heavier weights.
It doesn’t.
If adding weight means you’re suddenly:
Performing half reps
Swinging the weight
Losing control
Using momentum
Completely changing your technique
you haven’t necessarily progressed.
Sometimes performing the same weight with better technique, greater control or an improved range of motion is progress.
Reps vs Weight: Which Wins?
Neither.
For strength
Prioritising heavier resistance and lower-to-moderate repetitions generally makes sense.
For building muscle
A range of repetitions and loads can be effective, provided your sets are sufficiently challenging.
For muscular endurance
Lighter resistance and higher repetitions become increasingly useful.
For many gym members, the best approach is therefore a combination of all three.
Try This in Your Next Workout
Instead of performing every exercise for the same number of reps, try varying your approach.
For example, an upper-body workout could look like:
Incline Press3 × 6–8 reps
Seated Row3 × 8–10 reps
Chest Press3 × 10–12 reps
Lateral Raises3 × 12–15 reps
Bicep Curls3 × 12–15 reps
This gives you a mixture of heavier and lighter resistance while still keeping every exercise purposeful.
The Apex Takeaway
Don’t get caught up thinking heavy weights are automatically better.
A successful workout isn’t determined by the number written on the weight stack.
Focus on:
Some days that might mean lifting heavier.
Other days it might mean performing more reps with complete control.
Both can move you closer to your goals.
And if you’re unsure what weight, rep range or exercise is appropriate for you, speak to a member of the Apex Gym team — we’ll be happy to help you get more from your training.