Training Intensity Threshold And Muscular Hypertrophy  


Key Points:

1) More total volume over time (reps x sets x tonnage) is key to more muscular hypertrophy. 

2) Hypertrophy can only be maximised once a THRESHOLD level of training intensity is reached. This is likely to be around 40% 1RM (but more research is needed, especially in TRAINED individuals!)

3) Lifting heavy weights all the time is NOT the answer to optimal hypertrophy. 

4) Periodising your training intensities can help prevent injuries and fatigue without comprimising your ability to maximise muscular hypertrophy

5) More total volume can ONLY be effective in increasing hypertrophy IF the THRESHOLD point is reached for training intensity. 


Heavier Weight, More Gains?

When it comes to developing more muscle, many people fall into the trap of thinking that more weight is always best for more gains. It is not a surprise that I frequently see people piling on lots of weight onto the bar in the hopes of squeezing out extra muscle growth. While increasing weight is not a bad thing, there are a few problems which beginners can fall into: 1) more weight at the expense of good exercise execution. If your form is sloppy, then you risk injuring yourself and not activating the target muscle(s) you want to grow. 2) joint overload. Heavy lifting continuously takes its toll! You can’t grow muscle if your joints are destroyed, and 3) Fatigue. Repeated heavy lifting eventually wipes you out, and fast! While heavy lifting should have an important place in your hypertrophy routine, you don’t need to be doing it week in, week out in order to maximise your muscle growth. In my experience, those who are just concerned with weight on the bar, tend to be the first to stall, get injured or lose motivation all together due to lack of progress.

One of the questions that has been asked over the past few years is: do we need to be lifting above a certain threshold level of intensity (weight) in order to activate muscular hypertrophy? We know that total training VOLUME over time is the main driver of muscle growth. That is simply the total number of repetitions, sets and the tonnage (weight) that you utilise over time (reps x sets x tonnage). The greater the total volume you can use over time, the greater your gains could be, provided however that you can successfully recover from it all.

However, in order for volume to play its role in your gains, you need to be lifting above a certain intensity level. In order words, you can do all the volume you want over time, but if you aren’t hitting a minimum threshold level of intensity during your workouts then you are not maximising your muscular hypertrophy potential. Why is knowing this threshold value of importance to you? Well for one, it ensures that you are always lifting heavy enough to maximally activate muscular hypertrophy. But also, it gives you greater clarity on what intensity ranges you can be working within to maximise your muscle gains. Up until now, many people have assumed that higher intensities are better for muscular hypertrophy development. But as mentioned, using heavy weights all the time brings a range of problems, which ultimately can act to slow down your future progress. By knowing the existence of a threshold level of intensity for maximum muscle growth, you can better plan your training to

Avoid some of the problems with lifting too heavy, too often.

Ensure that you always train within an optimal intensity range so that the total volume you utilise over time, is directed to eliciting maximum muscle gains. After all, if you are not hitting a minimum intensity level during your training, then all the volume you do, will simply be wasted energy!

Think of it this way: more training volume is the engine that drives muscular hypertrophy, but a minimum intensity level is the key that starts this engine to ultimately get the whole process moving.

Lasevicius et al. (2018): Threshold Intensity Level For Maximum Hypertrophy Study

A recent study has helped shed some light on what the minimum intensity level is likely to be for stimulating maximal muscle growth. Lasevicius et al. (2018) investigated the impact of different training intensities (% 1RM): 20% (G20), 40% (G40), 60% (G60) and 80% (G80) on the cross sectional area of the vastus lateralis and elbow flexor muscles over a 12-week training period in UNTRAINED healthy men. Each participant performed two weekly sessions of unilateral elbow flexion and leg press. The great thing about this study is that this is the first study to equate total training VOLUME (sets x reps x weight) between the different intensities used. In other words, by keeping volume the same in each experimental condition, we know that any changes occurring are due to intensity and not other effects such as changes in overall volume.

However, after 12-weeks it was found that all training intensities produced significant increases in the cross-sectional area of the vastus lateralis and elbow flexors muscles above pre-training levels, with training intensities in the range of 40-80% producing the greatest gains. While a training intensity of 20% did increase muscle size significantly above baseline, these increases were much smaller than those of the G40, G60 and G80 groups, suggesting that 40% could be the threshold level needed to maximise the muscular hypertrophy process. Furthermore, the extent of increase in muscular size above baseline for G40, G60 and G80 training intensities were similar, suggesting that you don’t always need to train with super heavy weights to get the best responses. It is important to note though that no intensities were tested between 20% and 40% in this study, making it difficult to pinpoint exactly where the threshold point might be.

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Lasevicius et al. (2018). FIgures show the changes in cross-sectional area of the elbow flexors (top graph) and vastus lateralis (bottom graph) in UNTRAINED men following 12-weeks of resistance training in response to different training intensities: G20 (20% 1RM), G40 (40% 1RM), G60 (60% 1RM) and G80 (80% 1RM). In all cases, all training intensities increased muscle size significantly, with G40, G60 and G80 producing the largest increases, suggesting a threshold point for optimal muscular hypertrophy at around 40% 1RM. All increases in muscular hypertrophy were similar between G40-G80 suggesting that above a threshold point, maximum hypertrophy is obtained. This allows for one to periodise training intensities in order to minimise the negative effects of very heavy lifting while still maintaining optimal training for hypertrophy. 

This study is the first to investigate different intensities on muscular hypertrophy when total training volume is kept the same. Since many previous studies failed to control the total volume, it has been difficult to know exactly, the role different intensity levels have played in the hypertrophy process. In this recent study, keeping volume the same has made it easier to study the role of only intensity on muscle growth in response to weight training. The major drawback however is that this study was done in UNTRAINED people. As untrained people are hyper-responsive to training stimuli, it is not a surprise that they responded significantly to a range of training intensities. Since muscular adaptations are much more difficult to stimulate in more trained individuals, the question is whether the same training intensity ranges (certainly those at the lower end, 40-60% of 1RM), would produce the same significant increases in muscle size. It is possible that the minimum threshold level is shifted upwards for experienced lifters. We don’t know this at this time. Still, this study helps give us some guidelines on what intensity ranges might be best to work within when it comes to maximising our muscle growth and it seems like a range of between 40-80% 1RM might be best, with 40% being the threshold level. Below 40% 1RM and you risk missing out on a lot of potential gains!

How Does This Threshold Level Help Your Training?

If there is a minimum intensity level for eliciting maximum hypertrophy, then this gives you some guidance on your own training programming. If 40% 1RM is indeed a threshold point, then you will want to ensure that your training has you lifting at least this heavy. That way, you know you are lifting heavy enough to start the hypertrophy process. Once you have achieved this threshold level, working on increasing your total volume over time (through a combination of reps, sets and weight) will be your top priority in order to drive your muscular progress further forward. Given that 40%, 60% and 80% all produce significant gains in muscle size, we know that training with super heavy weights all the time is not necessary for maximum muscle growth. Which is great! This means you can PERIODISE your training intensities. In other words, you can spend time training in all intensity ranges, allowing your body and joints a rest from very heavy weights, but still keeping you in a range that maximises muscle development (provided your total volume is still increasing over time). For instance, you might spend 6 weeks training at 80% 1RM and then the next 6 weeks training at 60% 1RM. While you will still be training within a intensity level that maximises your muscular hypertrophy gains, you give your body a rest from heavy loads at 80% 1RM, preventing possible fatigue and over use of your joints.

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However, I am not saying you should now neglect heavy training work. Intensities of 80% and above are still the most effective at building maximum strength. Even if your goal is not maximum strength, improving your maximum strength ceiling will translate into you being able to lift more at lower training intensities. In other words, you gain an increase in total volume efficiency. If you can lift more, your total volume can increase without you having to do endless amounts of reps and sets. Therefore, you don’t want to neglect heavy work all together! At the moment, we know two things: 1) more total volume over time is needed for more muscle growth 2) 40-80% 1RM seems to be the range to train in for maximum growth, with 40% being the threshold point. By knowing these two things, you can put a training plan together that maximises your muscular potential and also, reduces your risk of burnout and injury through heavy weight lifting.



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