The intensity continuum

Last week we talked about all manner of different training variables ranging from lifting tempo and exercise selection all the way over to range of motion and rest between sets. Two weeks ago we talked about intensity and I hinted at different kinds of intensity – which is exactly the topic for today (which you probably ascertained from the title).

One more formality before we start digging into today’s topic, next week marks the beginning of the new phase of this series of articles. Namely, we will start discussing individual body parts – how to train them in terms of the holy trinity (volume, intensity and frequency) as well as exercise selection and many other considerations.

We need to establish two assumptions before continuing any further and the first one (the more important one) is that everything I am about to discuss applies and makes sense only if you’re training hard enough. So if I say doing low repetitions builds strength that means that you did a low number of repetitions with a heavy weight and you did not leave too much in the tank. For instance, let’s take heavy triples, meaning you only do 3 repetitions, in order for that to be included in the discussion below, 3 repetitions have to be very close to failure for you (think of the RIR scale). The second assumption is that you’re executing exercises with proper form.

With all of that out of the way, let’s explain the intensity continuum. You can think of this concept as a straight line with overlapping categories on it. These overlapping categories are: strength, hypertrophy (muscle growth) and muscular endurance. I say overlapping because all three types of intensity cause adaptations in all three domains, but to differing degrees. You’re probably still confused, don’t worry I’ll explain.

If you’re doing fairly heavy weight in the low repetition zone you’re gaining a lot of strength, building some muscle and very little if any muscular endurance.

If you’re doing moderately heavy weight with a moderate number of repetitions, you’re gaining some strength building a lot of muscle and some muscular endurance.

Lastly, if you’re doing relatively light weight with a lot of repetitions you are gaining very little if any strength, building some muscle and a lot of muscular endurance.

I tried to illustrate this with a “graph” which you can find below (please excuse my horribly lacking skills in MS Paint).

Piece of art

Now we should put this into the right context, in this case that is the goal of this series of texts – building muscle. I would like to highlight three points from an earlier text on the topic of what you need to do to grow:

1. Adequate tension stimulus – meaning that the weight you are lifting is sufficiently heavy. Usually this means 60% of your 1RM and above. Again, assuming that you’re working relatively close to failure in terms of the reps left in reserve (RIR scale)

2. Adequate volume – meaning that you do enough effective sets and reps

3. Progressive overload – you need to be increasing the weight on the bar over time

Studies by Brad Schoenfeld and his research team have shown that all three types of intensity build muscle pretty much identically if volume is equated (volume here means weight times sets times reps). What does this mean practically? Can you do all heavy work and still make fantastic gains? Yes, BUT and it’s a huge but, you will suffer in doing so. Imagine squatting 125 kg for 3 reps and that’s very close to failure for you. That one set equates to 375 kg of total volume. Now imagine squatting 75 kg which is very light for you given your 3-rep-125kg-squat. You would need to do only 5 repetitions in order to match the same volume. Now just stop and think for a moment. How long do you need to recover after a heavy set of 3 repetitions? How tired are you going to feel? How banged up are your joints going to be if you only did this kind of heavy work? How many times a week will you be able to stimulate your muscles if you work this heavy all the time? The answers to all these questions are negative. You are going to be very tired, your joints and tendons are going to be completely fried, and you will have to rest between sets for a long time and between workouts as well. All of this makes training only heavy a choice with many flaws like risk of injury, suboptimal recovery, suboptimal frequency, a lot of fatigue accumulation.

On the other hand, if you go too light and work in the muscular endurance domain, you will need to be doing a lot of work just to get the same benefits of drastically less work at a higher intensity. This is due to the fact that full motor unit and muscle fiber recruitment with lighter loads happens only as you approach failure (meaning on the last few reps).

So it seems like the bro scientists were onto something by doing everything in the 6-12 rep range. They were partially right in that this range will give you some strength gain especially if you work at the lower end of that (6 reps), and it will also maximize motor unit and muscle fiber recruitment. In addition, damage to your joins as well as fatigue accumulation will be lower than with pure strength work.

Does that mean that you should be working only in the “hypertrophy zone”? No, far from that. Getting better in the strength and endurance zones will have carryover and it will help you break plateaus when you start stagnating. There is also the issue of muscle fiber type and working in a variety of repetition ranges will help you maximize stimulating all types (I will go into more detail in a future post). It is also very boring to work in the same rep range all the time, so add variety which means your workouts will be more fun and more fun usually means better adherence and better effort which in turn means better gains.

So the final recommendation is that you should do between 60% and 80% of your total work in the so-called hypertrophy range while the remainder should be done in the other two. The way you split this in a week is entirely up to you (or your coach). You can hit all three ranges within a single workout, you can have heavy, medium and light days. You can have a strength and a hypertrophy day. The combinations and schemes are endless.