light weights vs heavy weights: which is better?

Light Weights vs Heavy Weights: Which is Better?

There is a lot of debate when it comes to light weights vs heavy weights. Which is better for building muscle – lifting light or lifting heavy? Everyone seems to have their own opinion on this topic.

Some believe that high reps and body weight calisthenic-type exercises are best. Meanwhile, others swear that low rep, heavy weight training is better for faster muscle growth. So today, let’s go over which style of training will lead to the best results. This information is based on scientific data rather than just giving you another opinion. 

To actually find out the answer, we first have to be clear on what training intensity is. In exercise science, training intensity refers to the percentage of your one-rep maximum that you can train with for a given exercise.  

What is a One Rep Max?

If you were using 100% of your one-rep max, that would mean that you’re using a weight load that’s so heavy that you can only complete one repetition and no more. On the other hand, 80% of your one-rep max would be a weight load that you could probably rep out for seven to eight reps before hitting failure. Each training intensity level, whether it’s 70, 80, or 90%, correlates with a certain rep count based on data gathered from many strength training studies. 

You can see all that data simplified in the table below:

As you can see, it’s pretty obvious that if you train with a smaller percentage of your one rep max, you’ll be able to do more reps. On the other hand, if you train with a larger percentage of your one rep max, you’ll only be able to perform fewer reps.  

Light Weight High Reps vs Heavy Weight Low Reps

So let’s see why some lifters claim that you should train with lighter weights for higher reps if you want to maximize muscle growth. Well, first, the high rep crowd claims that lightweights and high reps are better because they create a lot of metabolic stress. That stress is a physiological process that happens during resistance training as a response to low energy levels inside the cell leads to metabolite accumulation

Second, training with high reps many times feels more effective. I mean, you get a huge pump and you can see your muscles blow up when you look in the gym mirror. So it must be the ideal training style, right? Well, not necessarily. There’s nothing magical about doing lightweight, high rep pump training. 

It’s not a bad strategy for muscle growth either, and many popular bodybuilders rely primarily on light weight training, but there’s nothing special about it. For example, several studies found that you can build the same amount of muscle with low, moderate, and high reps. 

Diving deeper into the data, research shows that very high rep sets where you only use 30% of your one rep max can stimulate as much muscle growth as a traditional bodybuilding rep range, where you use 80% of your one rep max. However, before you assume you can use any weight load or any rep range to build muscle, hear us out – it’s not as simple in real life as the studies that are done in a controlled lab setting. 

man lifting lighter weights vs heavier weights for muscle growth

Light vs Heavy Considerations

Specifically, there are three important things to keep in mind when thinking about light weights vs heavy weights.

First, very low rep training, such as doing one or two reps per set, is very unlikely to be optimal for muscle growth. We can see this play out in a study that found that doing eight heavy sets of one rep max outs led to worse results than eight sets of eight to twelve reps. So make sure you select a weight load that allows you to squeeze out at least three reps per set if you want to maximize muscle growth. 

Second, training with very heavy loads for low reps happens to be much more stressful on your joints and connective tissues compared to training with a moderate or a high rep range. 

Even if you look at the studies that found that people who trained with low reps gained the same amount of muscle, you also usually see that they had a higher injury rate as well. So very low rep training might not be ideal if you have aches or pains in your joints or if there’s some other reason that makes you more susceptible to injuries. 

Also, even if you like to train with a really heavy weight for a low amount of reps, it’s not recommended to do that for isolation exercises like bicep curls or lateral raises. This is because it’s simply very difficult to maintain proper form when doing these isolation movements with heavy weights, and you’re much more likely to cheat and use momentum. 

Compound exercises like the squat, bench press, and deadlifts, on the other hand, can be performed with heavier weight loads and for lower reps without issue as long as you maintain proper form and aim for at least three reps.

High Reps Pros and Cons

Now let’s look at the other end of the spectrum at high reps.

Right away, we find our third issue with selecting any random rep range to build the same amount of muscle with high rep sets as you would with moderate rep sets, you would have to train to failure. Research indicates that if you don’t train to failure with those higher rep sets, you won’t reap the full benefits. 

Since most people don’t have the stamina to grind out five sets of failure with a very lightweight of, let’s say, 30% of your one rep max, it tends to be better to do more sets in moderate and lower rep ranges. I mean, think about it. If you’re using about 30% of your one rep max, you’ll be able to rep anywhere between roughly 25 to 35 reps. 

Are you going to have the stamina to do that for five sets? Also, will you be able to keep your mind focused for 25 to 35 reps without giving up or resorting to horrible form before you actually hit failure. Imagine right now, even if you did 50% of your one rep max for an exercise like squats and try to do as many reps as possible, you’d probably be completely wiped out after just one set. With all that said, don’t avoid high rep training altogether, or any rep range. For that matter. 

You can use higher repetition sets for isolation exercises like lateral raises or bicep curls, where excessive fatigue isn’t as much of an issue. And research actually shows that you’ll grow more muscle when you train with a variety of rep ranges instead of always trying to hit the same number of reps every set. The reason for this is that different rep ranges emphasize different muscle-building pathways in the body.

Is it Better to Lift Heavy or Light?

High rep training primarily triggers the metabolic stress pathway, which, like was mentioned before, is a process that causes very low energy levels within the cell and leads to the accumulation of lactate, phosphate, and hydrogen ions. All of this has its benefits for muscle growth. On top of that, high rep training is also better for training your slow-twitch muscle fibers, which are fibers that aren’t as strong as fast-twitch fibers, but they’re more resilient to fatigue. 

Low rep heavy weight training, on the other hand, creates high amounts of mechanical tension and that stimulates muscle growth in a different way. It activates specialized proteins and muscle cells known as mechanosensors, which in turn kick off a cascade of genetic and hormonal signals that stimulate your body to build new muscle tissue.

Related: The 6 Best Lifting Straps

Those mechanosensors are only activated by very high levels of tension, which is why it’s beneficial to also include low rep heavy weight training into your workout routine. Again, usually higher than three reps is best for low rep sets for injury prevention and faster muscle-building progress. 

Aside from providing higher mechanical tension, low reps and heavy weights are also more effective for training fast-twitch muscle fibers, which are muscle fibers that can generate a lot of force, but also tire out very quickly. Another major benefit of training with heavy weights is that even though heavyweight, lower rep sets are great at building muscle, they’re also one of the best ways to get physically stronger.

Even if you don’t care about gaining strength and you just want to become as big as possible, strength gains are still beneficial for size gains. Research shows us that strength development is accompanied by increased muscle activation levels during exercise. 

light weights vs heavy weights

Light vs Heavy Weight for Building Muscle

Developing more strength from heavy weight training ends up benefiting muscle growth, even if you train with moderate or higher reps, because the strength gains you get from your lower rep sets will carry forward to your moderate and high rep sets, allowing you to lift a heavier weight load for those sets as well, leading to more overall muscle growth.

To sum it up, it’s best to include low rep, moderate rep, and high rep sets because they all activate different growth pathways in the body. 

That being said, from a practical perspective, you probably want to do most sets at a moderate rep range. It’s less strenuous than doing many high rep sets, and it’s less taxing on your joints and connective tissues than focusing on lifting very heavy weight loads for a small number of reps.

Light vs Heavy Rep Ranges

Let us provide you with some examples of how you can incorporate all these different rep ranges into your workouts for maximum results. 

A big favorite is periodization. You could switch up your rep ranges every workout, every week, or every month by using periodization. 

Better results are often seen from switching every month because it gives the body enough time to adapt and grow stronger for the specific rep range that you’re working on. 

Periodically Change Your Rep Range

One of the simplest ways to do this is to spend about three to four weeks within one of three rep ranges before moving on to the next one. The three rep ranges that have worked for me the best are three to five reps, six to eight reps, and twelve or more reps.

So you spend three to four weeks lifting a heavy enough weight load that makes you hit failure within three to five reps. Then for the next three to four weeks, you would switch to the six to eight rep range, where you would select a lighter weight than what you were using for the three to five rep range. 

You should still be lifting heavy enough to hit failure within your new six to eight rep range. Then after three to four weeks, do the same for the twelve plus rep range. Then, simply cycling back and forth like this should help you get stronger and build more muscle faster.

Each time you come back to a previous rep range that you might have done weeks or months ago, try to up the weight that you do for that rep range in comparison to last time. Now, if you don’t want to stick to one rep range for up to a month at a time, you can also incorporate different rep ranges during each workout and set those rep ranges depending on your goals. 

Rep Range Examples

Set Percentages pyramid 1

So let’s say you’re not too focused on gaining more strength as you gain muscle. You can aim to do only 15% of your sets in the three to five rep range, 70% of your sets in the six to twelve rep range, and 15% of your sets in the 13 plus rep range.

And this is just to give you an idea. You don’t need to do the math to figure this out or be exact. 

With this setup, you would just incorporate one to two heavy sets and one to two light sets for every seven moderate rep sets that you do. And understand there’s nothing particularly magical about this setup, it’s just one way to incorporate all rep ranges for maximum muscle stimulation. 

Set Percentages pyramid 2

Another scenario where you are also focused on gaining strength in addition to building muscle would be performing about 30% of your sets in the 3-5 rep range, 60% of your sets in the 6-12 rep range, and only 10% of your sets for 13+ repetitions. 

One last scenario is if you’re older, more prone to injury, recovering from a previous injury, or have achy joints, then you can focus more on high rep work.  

Set Percentages pyramid 3

People who are older can especially benefit from high rep sets because they have less connective tissue due to a lower protein turnover rate which increases injury risk when training heavy by weakening joints and tendons.

So for older adults and people with nagging joints or injuries, they can do 0% of their sets in the 3-5 rep range, 60% of their sets in the 6-12 range, and 40% of their sets for 13+ reps.

Light Weights vs Heavy Weights for Fat Loss

There isn’t really much competition when it comes to light weights vs heavy weights for fat loss. If your main or only goal is to lose weight, then you should be trying to burn as many calories as possible.

Lifting lighter weights for a higher number of repetitions is the way to go here as by doing this your body won’t fatigue as quickly compared to lifting heavy weights for lower reps and you’ll be able to work out for longer and burn more fat.

That being said, if you also want to gain a little muscle while also losing fat, incorporating some heavy weight, lower repetition sets will still be a good thing to do. As stated before, increasing your strength will help you gain muscle as you’ll be able to lift more and with bigger muscles, your body will naturally burn more calories in your day-to-day life.

The Verdict 

As a general rule of thumb, we would say that most people can benefit from incorporating all rep ranges into their training if possible.

This will help to ensure that you’re stimulating all the different muscle fibers, which will lead to more overall growth in the long run.

So experiment with different rep ranges, find what you enjoy most, and make sure to keep progressing in some way each week whether that’s by adding more weight, reps, or sets.

As long as you’re consistently progressing and challenging yourself, you’ll eventually reach your goals. 


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