It has been well established that you can build just as much muscle from using lighter weights as you can from heavy but are there any other factors to consider?
Classically, there has always been a hypertrophy (muscle building) repetition range, which has always been 10-12 reps per set. However, providing that you are working close to failure in your sets, almost any rep range will build muscle equally well. This has been proven and it is now considered pretty well nailed on by researchers such as Schoenfeld et al (2017) and Fink et al (2016) to name a few.
Below is considered a good guide to build muscle:
6- 30 reps (choosing a resistance or exercise that is close to failure somewhere in this repetition range)
3-5 sets with 1-3 minutes rest between sets.
You should train each exercise between 2-3 times per week as a guide.
So with such a range of reps and loads where should you train? There are some practical considerations to consider before just simply training 30 reps per set, close to failure, with a light load.
Now we know that volume is very important when it comes to building muscle, so you still need to get adequate training volume, which is reps x sets x load.
Here are two examples of the extreme ends of this spectrum:
6 reps x 3 sets x 100kg: Total volume equals 1,800kg. Exercise time with rests equals roughly 9 mins
30 reps x 3 x 20kg: Total volume equal 1,800kg. Exercise time with rests equals roughly 12 mins
So, if your sessions consisted of 10 exercises then the heavy load session would take 90 mins but the light load session would take 120 mins!
So for the same training volume, the light session would take longer by a substantial amount.
There is a solution to this though
It is called Myo-reps, which is training with a light load but with 3 deep breaths as your rests between sets. We know that you need to be working close to failure and in a study by Haun et al (2018), they found that 4.4 Reps In Reserve (RIR) and above was the point at which the muscle-building effects started to significantly lessen. So this highlights the most important reps of any sets of the last 5 or so.
Straight sets with a light load and long rest times, mean most of each sets’ repetitions are just getting you to the last, most important reps for muscle building but Myo-reps keeps you fatigued and always in and around those last reps and has added efficiency of time.
Here is a Myo-reps set out as an example:
All done with 20kg:
Set 1: 30 reps
Set 2: 25 reps
Set 3: 18 reps
Sets 4: 11 reps
Set 5: 6 reps
This is 90 reps x (The same volume) 20kg so 1800kg
So how long does this take?
Under 4 mins per exercise so 10 exercises would be under 40 minutes!
So you can train with light weights and be time-efficient by using a strategy such as Myo-reps but remember that time is not the only practical consideration to overcome with light load training.
Now, I remember a TV programme that did an experiment with women who trained one arm and one leg with a heavy load and the other with a light load and they went to failure on both types of training protocols. As expected, they grew just as much muscle on both sides of their bodies but what I found funny was before they started they asked the women a question. They asked them what they thought about being able to train with light weights and build muscle. Their response was “Amazing that sounds easy”. I thought no it’s not, it’s harder. I knew that by the end of the training they would change their mind and guess what they did! When asked again they said that they much preferred training heavy because training light to failure made them feel sick, their muscles burned and they got out of breath etc.
Try lightweight training yourself and make sure that you go close to failure and you will find it very demanding. So if you are going to train light then be prepared to work ‘rock’ hard and if not go heavy instead!
This is the big issue!
In a session with light weights, whether done straight or with Myo-reps you may just find that the session is so demanding on your acute recovery that you can’t do what you had planned. I would say that you have a better chance with Myo-reps due to its super-short session length but this still taxes your cardiovascular and central nervous system a lot! This is not only an issue in your session but the fatigue can last for days, therefore affecting your next training session.
It is important to note that central nervous system fatigue means that you will be underperforming throughout your entire body not just where you have trained. So even if you have a body part rotational split you may be recovered in the muscles themselves but not in the central nervous system, meaning your next session will be negatively affected even if it’s a different body part.
If you try it yourself you will know what I mean but the research has already shown that training with lighter loads causes greater and more sustained post-workout fatigue than heavier load training. Farrow et al (2020), found greater and more sustained post-workout fatigue after single-limb training and this affected both the trained and untrained limbs, which is a clear indicator that lighter load training causes more central nervous system fatigue and more peripheral fatigue.
Practical implications of this are your sessions may deteriorate as they go on and your sessions afterwards could be negatively affected.
To summarise our article on “Light weights build muscle just as well as heavy weights but should we train light really?”
You can train light, heavy or moderate and you can train with straight sets or Myo-reps but light load training is harder to do and harder to recover from. You need to understand how good or bad you are at working really really hard and how good your cardiovascular fitness is. Finally how good you are at recovering? If you are great and you sleep well, eat well and have low stress in your life then you will cope better with lighter load training. Even if this is the case you should have block periodised phases of training with light, moderate and heavy at various points through the year as to keep your body from fully acclimatising and desensitising to training.
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