If you have been exercising for any length of time and following a strength training program, you will undoubtedly have been confronted with a choice. Should you a) lift more weight or b) do more reps.

Doing the same workout over and over will not result in improved fitness and you need to expose your muscles to more stress if they are to get stronger, bigger, or perform better. But what form should that stress take? The answer is: it depends!

Adding weight – effect, pros and cons

If you can complete all of your prescribed reps with a certain weight, increasing the weight will make your workout more demanding and therefore more productive.

For example, if three sets of 15 reps using 10 kg is no longer demanding, using 12.5 kg probably will be. After a while that same 12.5 kg will no longer provide your muscles with the overload they require and so you’ll graduate to 15 kg.

Adding weight predominately increases strength – strength being the ability of your muscles to generate force. Stronger muscles are invariably bigger and more toned and have a greater capacity for work.

Increasing the weight is simple but not always easy. In the example above, moving from 10 kg to 12.5 kg represents a 25% increase in weight and that’s a lot. Many machines go up in jumps of 10 kg so moving from 20 kg to 30 kg represents a 33% increase.

Moving up to the next set of dumbbells or increment on a resistance training machine may be a step too far unless the repetition range changes too – a method commonly referred to as double progression. 

This problem becomes worse with “small” exercises like biceps curls and leg extensions but presents less of an issue for big, compound exercises such as deadlifts and squats where larger increases can be more easily accommodated.

It is also somewhat unrealistic to expect to be able to add weight indefinitely. If you added as little as one kilo per week, that would equate to 52 kg per year which is simply not sustainable.

Adding reps – effect, pros and cons

Increasing the number of reps while keeping the weight constant increases the amount of exercise your muscles have to do. This predominately improves muscular endurance which is the ability of your body to perform work.

For example, if you manage three sets of ten reps with 30 kg, next time do one set of eleven and two sets of ten. Continue adding a rep per week until you hit a plateau and can no longer continue or you reach the upper limit of your set/rep scheme i.e. assuming the prescribed rep range is 10-12:

Week 1. 10, 10, 10

Week 2. 11, 10, 10

Week 3. 11, 11, 10

Week 4. 11, 11, 11

Week 5. 12, 11, 11 etc.

On reaching 12, 12, 12, increase the weight by 5-10% and go back to three sets of 10 reps.

The main disadvantage of adding reps is that invariably you will come to a point where you simply are at your limit and cannot do more reps. Also, because you don’t want to add reps indefinitely (sets of 50 are kinda pointless) you’ll have to add weight anyway.

Which option is best?

The best option is the one that suits your goals. If you specifically want to increase strength, adding weight is probably the best way to go. If, however, you are more interested in muscular endurance, you’d be better served by adding reps. Increasing muscle size is often best achieved with a combination of the two.

Make sure though that you never sacrifice good exercise form for more weight or reps. Doing so makes any increases meaningless and also increases your risk of injury.

As both options are effective, there is no reason to use one method and ignore the other. If you reach the point where adding more weight is impossible, start to increase your reps. In contrast, if you can no longer increase your reps, try adding weight. These methods are simply tools to be used and one is not superior to the other.

Whichever option you choose, make sure your set and rep scheme is appropriate for your goals:

  • 1-5 reps for strength and power
  • 6-12 reps for hypertrophy (muscle building)
  • 12-20 reps for endurance

Manipulate your reps and the weight to keep you in the right range for your goals.