Key Takeaways:
There are two main ways to gauge how intense you’re lifting, rating of perceived exertion (RPE) and percentage of 1-rep max (%1RM).
RPE is a subjective assessment as to how close you are to failure (i.e., it’s a guess as to how many more reps you could have done with a given weight before failing). Although it is subjective, RPE is reliable and valid (even for beginners).
%1RM is an objective metric used to assign how much weight to lift on a given exercise. Essentially, someone will see how much weight they can lift for a single repetition (1RM) on a given exercise. Then, a coach will take a percentage of that weight and ask an individual to perform a certain number of reps at that percentage. %1RM is also reliable and valid, although the charts used to estimate the number of reps an individual can perform at a certain %1RM can vary substantially.
To maximize muscle growth, it’s more important to take your sets *close* to failure (i.e., ~ RPE > 5).
To maximize your strength, it’s more important to train with heavy enough weights (i.e., > 80% 1RM) than about taking your sets super close to failure.
Remember, the above recommendations are to maximize muscle growth and strength, but any workout is still better than no workout so please don’t feel like you’re not going to make progress if you don’t adhere to the above recommendations! The most important thing is that you show up to the gym consistently!
Our group classes, personal training options, and expert coaches will help measure your strength and muscle growth over time through regular testing to ensure that you’re meeting your goals!
Intensity is probably one of the most important concepts to understand as a beginner because if a given exercise is not challenging *enough*, your body will not want to adapt, get stronger, and build muscle. But, what exactly is challenging enough? Well, even researchers have difficulty defining what “enough” is but we’ll go ahead and take a stab at it. But first, let’s talk about how to measure how intense you’re lifting. There are two common methods, rating of perceived exertion (RPE) and percentage of 1-repetition maximum (%1RM). We won’t be covering velocity-based training (VBT) as that is a method of intensity prescription that we don’t commonly use in our programming, but that approach can definitely still be useful.
Rating of Perceived Exertion (RPE)
We’ll be using rating of perceived exertion (RPE) as a term to describe how close you’re taking your set to failure, for our purposes this may also be termed repetitions in reserve (RIR) based rating of perceived exertion (RPE). The RPE scale goes from 1 to 10 with 10 representing failure (i.e., the inability to perform another repetition through the prespecified range of motion) and 1 representing little to no effort (see Figure 1 below for the RPE scale we’ll be referring to).3 When using this scale while lifting, we typically ask people to shoot for a specific “target RPE” on their exercise to ensure it is challenging enough. For example, an exercise might ask you to “Squat for 1 set of 5 repetitions @ RPE 8” and we would expect you to perform 5 repetitions with a weight, rack the weight, and it should’ve felt like you could’ve only gotten 2 more reps with that weight before failing. However, if we asked you to perform a “Squat for 1 set of 5 repetitions @ RPE 10,” we would expect you to perform 5 repetitions, rack the weight, and it should’ve felt like you could not have gotten another repetition. It’s important to understand that RPE is a SUBJECTIVE guess or estimate about how close you are to failure or how many reps you have “left in the tank.” You probably won’t be the best at estimating these values the first time you do it, but the more experience you get with understanding what failure feels like, the better your estimate will probably become. That said, we actually don’t see a huge impact of training experience on the ability to accurately predict RPE, unless there’s a large difference in training experience.1 So, please don’t feel like you’re going to be super inaccurate with the RPE scale as a beginner! You can start using this scale right away to ensure you’re lifting with sufficient intensity.
Figure 1: Repetitions in Reserve (RIR) based Rating of Perceived
Exertion (RPE) Scale.
Image Credit: https://www.strongerbyscience.com/autoregulation/
Percentage of 1-Repetition Maximum (%1RM)
Percentage of 1-Repetition Maximum (%1RM) is the most common method to prescribe training intensity for individuals who participate in resistance training. With this approach, an individual will see how much weight they can lift for one repetition for a given exercise (i.e., their 1 repetition maximum or 1RM). After testing their 1RM, a coach can prescribe a certain number of reps at a percentage of that 1RM. For example, a coach may ask you to perform a bench press for 1 set of 6 repetitions @ 80% 1RM. So, if your 1RM is 100 lbs, you would bench press 80 lbs for 6 reps. Many strength training textbooks will say that most people can lift 80% of their 1RM for a maximum of 8 repetitions (a common chart for the number of reps you can perform at a certain percentage of your 1RM is shown in figure 2). This chart is a useful start, but it’s important to note that these values may not always be accurate and are actually exercise-dependent.2 For instance, when you compare individuals performing a leg press @ 50% 1RM compared to a bench press @ 50% 1RM, individuals are typically capable of performing significantly more repetitions on the leg press compared to the bench press at the same %1RM.2
Figure 2: Average number of repetitions performed at a given %1RM.
This data is a nice starting point but probably inaccurate since the number of repetitions performed at a given %1RM highly depend on the exercise and individual.
Image Credit: https://www.themovementsystem.com/blog/cscs-program-design
How Close Do You Need to Train to Failure to Build Muscle?
From an efficiency perspective, it’s recommended to use a weight that’s above 30% 1RM or a weight that keeps you in the 4-30 rep range, although very light loads (< 30% 1RM) may still grow muscle they unfortunately won’t get you as strong.4,5 Muscle growth does not occur solely in the 8-12 rep range (as shown in Figure 2), it actually spans an incredibly wide range, provided one takes their set close to failure. If you’re using lighter loads (< 60% 1RM) or if you’ve been lifting for a longer period of time, it may become increasingly important to take your sets to failure or closer to failure to maximize muscle growth. But how close to failure do we actually need to be? Well, the closer the better, since there seems to be a positive relationship between RPE and muscle growth.6 However, in other systematic reviews and meta-analyses, there is no difference between training to failure and not training to failure when it comes to muscle growth.5, 8 How do we reconcile these findings? Simple, lifting at ~ RPE 5-9 intensity might be just as effective as lifting at an RPE 10 intensity when it comes to muscle growth, especially if you’re using heavier weights. The RPE 5 cutoff above is based on my personal experience and coaching expertise rather than precise data. Trying to accurately estimate anything below ~ RPE 5 seems to be difficult because you’re going to be further from failure and estimating RPE becomes less accurate the further away from failure you train and if you perform more than 12 repetitions in a set.7 We need to get close to failure but we don’t actually have to fail all the time, but sometimes it might be beneficial to take your sets to failure to gauge progress, understand what failure feels like to better inform your subjective assessments of your own RPE, or if you’re more experienced and potentially require a higher degree of stimulus to gain muscle.9
Figure 3: This a theoretical rep range model many textbooks still use where it’s stated that muscle growth (hypertrophy) occurs primarily in the 8-12 rep range. We now know this to be a myth!
Image Credit: https://www.lookgreatnaked.com/blog/what-is-the-best-rep-range-for-muscle-strength-and-size/
How Close Do You Need to Train to Failure to Build Strength?
Unlike muscle growth, we don’t need to train as close to failure to get stronger.6 What’s more important is that we’re using weights that are heavy enough to maximize the amount of force you’re producing on each repetition, this is somewhere at or above 80% 1RM.5 This does NOT mean that training below 80% 1RM will not get you stronger! It’s just not “optimal” and that’s okay, not everything needs to be optimized. Something is always better than nothing. From an efficiency perspective, however, if I’m trying to get someone stronger AND build muscle, we’d probably still want to take sets close to failure to reduce the amount of time spent in the gym. If your goal is specific to strength, then you could perform more sets at a lower RPE (e.g., sets of 3 repetitions @ 80% 1RM), which would minimize the amount of fatigue generated and allow you to perform more sets more times per week which would potentially help improve strength. From an RPE standpoint, if I have to put a number on how low you can go and still get stronger, I’d say assuming training at or above 80% 1RM maximizes strength gains, you could theoretically perform 1 repetition @ 80% 1RM and therefore leave 7 reps in reserve and still probably get stronger, so maybe ~ RPE 3 or 7 RIR. This is honestly a guess and a recent meta-regression that just came out said you can go up to 10 RIR assuming the weight is heavy enough. Just remember, it’s hard to estimate RPE the further away you are from failure so if you’re doing low-fatigue strength work this is where %1RM or velocity-based training would really be useful.
Summing It Up:
No proxy for intensity is perfect and that’s OK. If you’re getting stronger, building muscle, and the proxy is reliable enough for you, that’s really all that matters! You can use RPE, %1RM, or velocity-based training, they all work, and all have their relative advantages and disadvantages as touched on previously. At D1, we use a combination of RPE and %1RM in our programming, depending on the exercise. To maximize your strength, it’s more important to train with heavy enough weights (i.e., > 80% 1RM) than about taking your sets super close to failure. Many other group fitness classes may fail to track these metrics, and you might be leaving gains on the table. In our group classes, we track these numbers to ensure you’re training at the appropriate intensity to get stronger which has a myriad of health benefits. To maximize muscle growth, it’s more important to take your sets *close* to failure (i.e., ~ RPE > 5). To reiterate, you do not have to train to failure to maximize muscle growth, just close to it. And training to failure all the time is probably ill advised for certain movements like squats and deadlifts where substantial fatigue might be generated and compromise the rest of the workout. Remember, these recommendations are to maximize muscle growth and strength, but any workout is still better than no workout so please don’t feel like you’re not going to make progress if you don’t adhere to the above recommendations! The most important thing is that you show up to the gym consistently!
References:
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