One of the biggest misconceptions people hold is the belief that you need to lift heavy weights to build muscle and light weights are next to useless.

In truth, you can build muscle with ANY load (including light weights), as long as your sets are difficult and come close to failure.

There is strong evidence supporting this from many scientific studies, like this one.

The study split 18 men into two groups. One group trained with light weights they could lift for 25-35 repetitions. Yes, you read that right. This is a far higher rep range than what people traditionally train with in gyms. The other group trained with weights they could lift for 8-12 repetitions.

It’s important to point out that the participants in this were “well trained men”. These weren’t beginners to resistance training who will likely see improvements easily regardless of the sophistication of their training approach.

Both groups trained with 3 sets of 7 different exercises which covered all major muscle groups for a total of 21 sets. Both groups performed 3 workouts per week on non consecutive days.

After 8 weeks, the results were that both groups gained muscle. The muscles tested were the biceps, triceps and quads. There was no significant difference between the two groups.

No such thing as a “hypertrophy rep range”

These findings kill the idea that there’s a “hypertrophy rep range” an “endurance rep range” or a “strength rep range”.

This is really significant because “old school” thinking about training would have you avoiding a rep range like 25-35 reps like the plague if you wanted to build muscle. Anything above 12 reps is seen as “the endurance rep range”. Not good for building muscle, but good for building muscular endurance. The “hypertrophy rep range” was always considered to be 6-12 reps (may differ slightly depending on who you ask).

It’s important to stress the point that sets have got to be difficult and close to failure. There’s more risk of this not happening with lighter loads. Sets moving heavier loads are already closer to failure even on the first rep. A light load that you could lift for 15 reps before failing won’t do much if you only lift it for 5 reps. The pink 1lb dumbbells that you could lift for 10,000 reps are still useless.

But if you use that 15RM load and take the set close to the point of failure (probably anything upwards of 12 reps) then that set will be just as valuable for building muscle as a set with a heavier weight.

Any rep range is useful for building muscle, but what about strength?

Any rep range will help you to build muscle and build strength. However, if you have a goal to lift as much as possible on your 1 rep max, then training with higher reps won’t be the best approach all of the time. Lifting weights is about skill as well as strength. Lifting weights in the 1-2 rep range is a different skill to lifting weights in the 10-12 rep range.

You would still get stronger training exclusively with lighter weights, but you wouldn’t be able to effectively use all of that strength in a one rep max attempt if you hadn’t been practising with heavier weights. Improvements in any rep range will transfer over to other rep ranges to a large degree. But, if you want to be particularly good at one of them, you should practice it specifically. If you want to improve at something, the closer your training resembles that thing, the more carry over it will have.

People planning to compete in strength sports which are judged on 1 rep max lifts will need to train with heavier loads at least some of the time if they want to maximise their performance.

Likewise, if your goal is to increase your 12 rep max, training with weights you can’t lift for more than 3 reps will still help you, but it won’t be as useful as training with weights you can lift for 10-12 reps. Some strength sports, such as strongman, involve events where the competitors need to lift for max reps. Training with lighter weights in higher rep ranges would therefore be more useful for these events than lifting in lower rep ranges.

How heavy should I train?

If your goals are health oriented or aesthetics oriented, then there isn’t really much need to ever lift that heavy. You’ll get the maximum benefits from resistance training even if you always lift in higher rep ranges, provided they’re taken close to failure.

You’ll also avoid all of the risks associated with heavier weight training and you’ll likely use better form – leading to better hypertrophy results.

Whilst you can get injured with any load, you’re far more likely to get injured training with heavier loads. Injuries are far more frequent with 1 rep max attempts than they are with lighter loads.

It’s much easier to use good form with lighter weights too. Good form makes it easier to target the right muscles. With heavier loads, you may shift load onto other muscle groups in order to get the weight to move. Your body will try to find a way to move the weight using leverage or momentum. This isn’t as effective for building muscle.

You don’t build muscle because of something your muscles did to a weight. You build muscle in response to something the weight has done to the muscles. This is a subtle difference. Try to see building muscle as more about using load or resistance to reach failure in specific muscles, not about moving weights.

If having enough weight seems like a barrier to making progress (weights too light) then trainees should know that this won’t prevent progress if hypertrophy gains are the goal. Weight is not even necessary if coming close to failure can be achieved with bodyweight exercises like squats, pushups and pullups. Of course, for practicality reasons these may have to be made more difficult so you don’t have to do sets of 50-100 to achieve muscular failure.

Should Competitive Strength Athletes Ever Train with Light Weights?

Speaking about the effectiveness of different training approaches for competitive strength athletes isn’t something I’m really qualified to do. I’m not one myself, nor have I ever coached any.

Still, it would make sense for these athletes to train with heavy loads – but not all the time. As mentioned previously, lifting heavy loads is strength and skill. Skills get better by practising them or training in a way that replicates them as closely as possible.

However, it would make sense to periodise training and lift in a variety of different rep ranges. This is because of the intense stress that lifting very heavy loads places on the body, not just joints, muscles and connective tissue, but also the nervous system.

Training with heavy loads all of the time is a good way to eventually end up beaten up, run down and injured.

Training in a higher rep range will also add more strength, and spending periods that are not as close to competition dates focusing on hypertrophy would probably be a wise approach. A bigger muscle is a stronger muscle. It would probably make sense to start training with some heavier loads when competition dates get closer. This would allow the athlete to hone their skill with lifting heavy weights. Any training program would have to be balanced with deload weeks and periods of backing off – not training so close to failure – to maximise performance on competition day. Performance won’t be at peak levels if the competitor is exhausted from their training protocol!

Other considerations for building muscle with light weights

So, you can lift light weights and build muscle, provided your sets are taken close to failure. But there are also other considerations. This alone isn’t enough.

Training

You must have progressive overload present in your training,. This means that over time the work that your muscles do is getting harder. The easiest way to do this is to track your workouts and always ensure you’re aiming to beat what you did last time.

You can do this whilst still lifting light weights, but over time they will get heavier – otherwise you’ll end up lifting 100s of reps per set. You should try to add at least one rep to one of the sets on each exercise. There’s isn’t a point where you NEED to increase the weight to keep the gains coming. Even sets of 35 reps are still be valuable for building muscle. However, that may not be that practical. Many people will also get more enjoyment from their training if the reps are kept in the moderate-high range. A guideline I like to use for increasing the weight is when I can do more than 12 reps. Then I up the weight by the smallest possible increment and carry on.

Nutrition

Another box to tick is your protein intake and your calorie intake. Studies have found that hypertrophy is better with increased protein intakes, up to 1.6g per kg of body mass. Weigh 80kg? Take in at least 128g of protein per day. No additional benefits are indicated from eating more than 1.6g per kg. Eating more than this may be good for fat loss though, because good sources of protein are also often filling foods and they lead to increased thermic effect of feeding.

It’s also easier to build muscle in a calorie surplus, especially if you’re no longer a beginner to resistance training. To get an estimation of how many calories you need, and what your macronutrient breakdown should be, try this macro calculator.

Recovery

Muscle isn’t built in the gym. It’s broken down in the gym and rebuilt while you recover, before your next training session. Make sure you’re getting adequate sleep and leaving enough time between sessions that work the same muscle groups. 48 hours is the absolute minimum. Many people will not be fully recovered until longer. Needing 72 hours to be fully recovered is common. Even needing 96 hours for full recovery has been observed for many people (especially older trainees).