Everything You Need to Know About Training Intensity

WorkoutsMindset
Written By Guest User

In the resistance training and fitness world, we generally tend to associate the term "intensity" with how hard we train. In fact, there is more nuance to the meaning of the concept of intensity than one might think. In particular, there are two distinct categories of intensity: intensity of load and intensity of effort. While the former is a key variable of resistance training, strength, and hypertrophy (together with volume), intensity of effort is what we usually talk about when judging a workout as "intense", generally speaking (i.e. high effort).

If we dig deeper into the definitions of these different types of intensity, we will first notice that intensity of load is the percentage of our 1 rep max lifted in any given exercise. The 1 rep max (1RM) of any resistance training movement (e.g. squat, db bench press, etc.) is the most amount of weight one can lift for one repetition, with good form and full range of motion. So, this means that intensity of load refers to how heavy the weight we use in an exercise is, relative to the most amount of weight we can handle for that exercise.

Intensity of effort is somewhat related to load, in that it can be defined as "the effort exerted during resistance training. This is generally gauged by the proximity to muscular failure" (Brad Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd edition).

The two types of intensity are correlated because a high intensity of effort seems to become crucially important as the intensity of loading is reduced. So, there is an inverse correlation between intensity of load and intensity of effort. This is a key idea that we will treat more extensively later on in the article.

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Intensity of Load

Let's dive into the details of intensity of load. This training variable can be established on a percentage based approach (i.e. the % of your 1RM), or on RPE (rate of perceived exertion) and RIR (reps in reserve). The main difference between the two approaches is that RPE is a relative, subjective measure of intensity (how close to failure does the set feel on a scale from 0 to 10?), whereas the % of 1RM is objective, therefore allowing for a more steady loading progression over time. As a matter of fact, in the %-based system nothing is left to your physical sensations of the day; there is a set weight prescribed based on a fixed percentage. This key difference makes RPE be a valuable tool for advanced trainees, who have significant training experience and can likely "listen" to their body more effectively compared to beginners and intermediates.

The Percentage Based Approach to Finding Your 1RM

So, let's look at these two approaches of managing load more precisely, starting from the percentage based approach. In order to use a percentage based approach, you need to know what is (more of less precisely) your one rep max. There are two main ways of measuring 1RM:

  1. you can lift as heavy as possible for one rep using great form in every main exercise (this may be unnecessarily risky, and you can find better ways of estimating your 1RM more safely);

  2. you can do a set of as many reps as possible with 90 percent of your estimated 1RM (or a weight you think is challenging enough for you to only manage a few reps to technical failure - 3 to 5).

Were you to choose the second, safer approach (definitely more appropriate unless you are a powerlifter or know what you are doing) to calculating your one repetition maximum, you can then plug the results of the AMRAP test into a 1RM calculator.

RPE Approach to Load

When it comes to using RPE, on the other hand, there is a lot of room for subjective physical sensations at play in such an approach. The general consensus here is that RPE is best suitable for advanced athletes, who tend to have mastered movements and become well in touch with their body. This statement is predicated on the fact that as you advance in your training journey, you become increasingly more capable of recruiting the right muscles during any given exercise; you supposedly become very good at performing exercises; and you also have the capacity to lift significantly heavier load compared to a beginner. As a consequence, these elements imply that you are able to effectively gauge how many reps you have "left in the tank", which is the key concept behind RPE and RIR. This is however a generalization, as someone may have been training for a long time but still be an intermediate or beginner trainee in reality.

The Role of Intensity of Load in Resistance Training

In order to find an answer as to why intensity of load is a relevant variable in resistance training, we first need to understand the main mechanisms behind muscle and strength growth: mechanical tension, muscle damage, metabolic stress. And the most important mechanism elicited by intensity of load is mechanical tension. One of the fundamental principles behind increasing muscle size and strength is that muscles have to be stressed through load (either with external resistance or bodyweight). Not only that. Over time, we adapt to stimuli and get used to executing a certain movement pattern, hence getting better at it (e.g. your ability to do a great squat increases as you deliberately practice the movement). So, when these adaptations occur, we need to ramp up the amount of tension in our muscles (progressive overload) in order to maximize our results.

Consequently, intensity of load is a key variable at play in the mechanical tension mechanism. This is because as we increase the weight (load) in any given exercise, we also increase the tension on the muscles worked (provided that the form of execution remains the same). And, by slowly progressing tension over time with great form of execution, we manage to grow stronger and more muscular over time (provided that other elements including nutrition are coherently accounted for).

Intensity of load, however, is not merely a matter of increasing load over time, regardless of how heavy that load is. Training in a medium repetition range (6 to 12) has been shown to be optimal for inducing optimal muscle hypertrophy, as it is the perfect spot that maximizes mechanical tension and metabolic stress. Loads during such training are heavy enough to recruit the majority of fibers in the target musculature and to maintain their stimulation over a sufficient period of time.

However, these findings have been challenged and it seems reasonable to postulate that including a wide rep range spectrum in training programs is optimal in order to recruit maximally all muscle fibers (fast and slow twitch). So, there is a key characteristic that is crucial to the understanding of load as a variable in resistance training: if your goal is muscle hypertrophy, including a wide spectrum of repetitions (with the majority of sets being in the 6 to 12 rep range) seems to be optimal in order to stimulate the best mix of mechanical tension and metabolic stress. Low-load high-rep training emphasizes metabolic stress and muscle endurance, while high-load low-repetition training requires high level of mechanical tension and increases neural adaptations. In addition, training below 30% of 1RM may be insufficient to fully stimulate muscular development and full recruitment of muscle fibers. Using an excessively light weight compared to your potential can be a waste of time.

Intensity of Effort

Intensity of effort is closely related to load in resistance training, and can be defined as the effort exerted during resistance training, which is generally gauged by the proximity to muscular failure. Muscular failure is the point at which you cannot do any more repetition of an exercise with decent form. A high intensity of effort becomes fundamental as the intensity of loading is reduced (inverse relation). This implies that in order to elicit maximum hypertrophic response and adaptations, we need to train to failure (or very close to it) when the weight lifted is light (15+ repetitions).

Reaching muscular failure seems to be of particular importance when employing high-repetition training because of the relationship between the proximity to failure and muscle activation during light-load training, and with increasingly greater resistance training experience. At the same time, persistently training to failure increases the chance of overtraining, which is the main reason for which it is generally agreed upon that most sets be carried out with an RIR (reps in reserve) of 1 or 2. Failure training must, therefore, be implemented selectively and usually reserved for the last set of an exercise or the high rep movements of a training session.

In addition to this, a useful rule of thumb is that failure must be used judiciously with compound movements (e.g. Squat, Bench Press, Deadlift), while more freely with single-joint (isolation) exercises. This is due to the fact that compound movements allow for significantly greater load compared to isolation exercises, which makes them (1) more risky for causing injuries, and (2) more focused on fostering mechanical tension and neuromuscular adaptation as opposed to metabolic stress.

Here are, therefore, 3 crucial pieces of knowledge regarding intensity to keep in mind:

intensity of load and intensity of effort are two distinct elements of resistance training.

Intensity of load is a key training variable, which must be carefully periodized and manipulated also taking into account other factors such as training volume and frequency of training.

Intensity of effort is a feeling-related element of resistance training which must be mindfully calibrated in order to avoid overtraining and foster effective growth.

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