RIR and Muscle Growth: Putting Options Back on the Table
It's often recommended that sets be performed with 0-4 RIR for muscle growth. This article discusses why that may be unnecessarily taking some options off the table, especially with multi-joint movements.
Key Points:
The common recommendation to only perform sets with 0-4 RIR for muscle growth may unnecessarily take options off of the table.
With heavy loads (~75% of 1RM and greater), some evidence suggests that sets can be performed with >4 RIR while still maximizing muscle growth. If this approach is taken, we recommend completing more sets to match total reps at the given load.
For fatiguing multi-joint movements, performing sets farther from failure may offer multiple benefits. Specifically, less fatigue per set may allow for more total training volume and the stimulus to the target muscle may be more efficient due to less technical deviation. We also speculate that higher RIR training may be able to potentiate future lower RIR training.
Training with high or low RIR’s should not be viewed as all or nothing, and programming decisions should be made after a cost-benefit analysis.
Introduction
We recently wrote an article making the case for what we call “low fatigue training” for strength gains (check it out here). We discussed the idea that avoiding intraset fatigue, thus keeping bar speeds high for a given load, maximizes force production. Since a 1 rep max is the ultimate test of force production, the principle of specificity leads us to heavily value the amount of force produced in our training. We will operationally define a typical set in low fatigue training as the below:
Load is >75% of 1RM (~10RM load and heavier)
Reps per set are low (typically less than 6) to minimize intraset repetition velocity decline
Each repetition is performed with maximal concentric intent
To accomplish the above criteria, more total sets at a given load will often be necessary. Below is an example of how one may apply these criteria while keeping relative volume (% of 1RM x reps x sets) equated.
High Fatigue: 75% of 1RM x 8 reps x 3 sets (~2 RIR)
vs.
Low Fatigue: 75% of 1RM x 4 reps x 6 sets (~6 RIR)
Within the article, we also claim that training in this manner can provide a sufficient stimulus for muscle growth despite each set being terminated far from failure (up to ~8 RIR in some cases). This goes against the common recommendation that a set needs to be terminated within the range of 0-4 RIR to be effective for hypertrophy. While we think 0-4 RIR may be a solid practical recommendation, the empirical support seems to be lacking. A recent study by Lasevicius and colleagues illustrates why this recommendation may not paint the entire picture. When using 80% of 1RM, a group training with an estimated 5-7 RIR saw the same muscle growth as a group training to failure. Volume was matched between groups, so the non-failure group performed more sets. Other studies have also found that groups training farther from failure (4+ RIR) can see similar growth to groups training closer to failure (0-3 RIR) (One,Two,Three). Importantly, this only applies to training with heavy loads (see criteria #1 above); for instance, the mentioned study by Lasevicius found inferior muscle growth when staying shy of failure with lighter loads.
Further clues can be found in the EMG research. First of all, we want to be clear that EMG is only a rough proxy for muscle activation and is limited in inferring hypertrophic potential. So, this evidence should be interpreted with extreme caution, but there may be reason to believe that our return on investment for the prime movers is maximized fairly early on in a set. A paper by Król and Gołaś found no difference in pectoralis major EMG activity between single repetitions of the bench press performed between 70% and 100% of 1RM. While this isn’t the exact same as comparing the reps within a set at the same load, it seems that there may be a load (and thus proximity to failure) in which a single repetition “maxes out” the stimulus we’re providing to the prime movers. Similarly, a paper by van den Tillar et al. found that EMG activity of the quads was similar between 70, 80, and 90% of back squat 1RM with slightly greater values at maximal effort (100% of 1RM). Overall, it appears as if maximal or near maximal EMG activity of the prime movers (i.e., quads in the squat and pecs in the bench) can be found without training in the 0-4 RIR range when using multi-joint movements.
Of course, this isn’t to say that the story is completely one-sided. When examining the literature as a whole (Greg Nuckols has an excellent article on this topic), there does seem to be a small benefit of training to or close to failure in two main scenarios: 1) when lifters are less experienced and 2) when using single-joint movements. Thus, our discussion in this article is going to be centered around experienced lifters performing multi-joint movements (e.g. squat, deadlift).
Overall, we view the current state of the literature as a proof of concept that higher RIR’s may have utility for muscle growth (e.g., physique athletes and strength athletes far from competition). Generally speaking, the evidence investigating proximity to failure and muscle growth is far from conclusive (an issue we talk about in a recent episode of our podcast), so we are not saying that training far from failure is better for hypertrophy. We simply think there is sufficient evidence to put higher RIR’s back on the table and add them to your metaphorical programming tool belt. Next, we will examine the potential benefits of higher RIR training and how they may be applicable for hypertrophy.
1. Less Fatigue Per Set
The most obvious benefit of low fatigue training for muscle growth is that each set induces less fatigue. Now, fatigue is a really complex phenomenon, but the research we have on proximity to failure and fatigue is fairly straightforward. Sets performed to or close to failure cause significantly greater muscle damage and decreases in performance the following days when compared to training farther from failure, even when total repetitions are equated (One, Two, Three). By breaking up the training volume into more sets while keeping the load the same, each set will be terminated farther from failure (and include less reps per set) with the intention of avoiding the disproportionate fatigue cost of the reps closest to failure.
Let’s revisit the two protocols mentioned earlier:
Protocol A: 75% of 1RM x 8 reps x 3 sets (~2 RIR)
vs.
Protocol B: 75% of 1RM x 4 reps x 6 sets (~6 RIR)
While each protocol accumulates a total of 24 repetitions, protocol B will likely result in considerably less fatigue. If we are able to apply the same or a similar stimulus for muscle growth while inducing less fatigue, that's a huge win. This could improve the rate at which we are adapting to the given workload. There are a few potential benefits to this. First, and probably most importantly, it may allow for more total training volume to be completed while still recovering. This is likely beneficial because greater weekly training volumes generally lead to greater rates of muscle growth. Secondly, deloads may be required less often. While it's definitely not clear if this actually matters in the long run, one could make the case that more weeks with a high workload in a training career could lead to more growth over time. Lastly, overall session quality may be improved. For example, if leg extensions are performed after squats, a squat protocol that spares mental and physical energy (while maintaining its hypertrophic effect) could promote greater focus and intent on the leg extensions, ultimately making the overall stimulus of the session greater.
The last thing to touch on here is time efficiency. A really common concern to protocol B above is that it takes more time. We’d argue that this doesn’t have to be the case. Since you’re accumulating less peripheral fatigue set to set, you can autoregulate your rest times in order to complete the protocol in a similar amount of time as protocol A. This autoregulatory approach to rest periods has been shown to be an efficacious strategy.
Overall, higher RIR training on multi-joint movements spares fatigue, allowing the lifter to potentially do more work, keep the work the same but at a higher quality, or a combination of the two. This added flexibility can be used to suit the needs of an individual to increase their rate of progress.
2. Less Technical Deviation on Multi-Joint Lifts
When training close to failure on multi-joint movements (e.g. squat, deadlift), it's natural for technique to change throughout a set. To be clear, we are defining muscular failure as the inability to complete another repetition, even while allowing for some deviation in technical execution. Others may consider failure as “technical failure” or the point in a set where no additional repetitions can be completed with excellent technique. Either of these definitions are totally reasonable, but we think the former has a bit less ambiguity. As a set approaches muscular failure, muscles other than those we are specifically targeting may begin to help move the load. This technical deviation may indicate the point in the set at which our return on investment has been maximized.
Using a squat as an example, if your quads are no longer able to meet a majority of the loading demands, your knees will slide back as your body looks to get some help from your back and hip extensors. If we’re using the squat as a tool to primarily train the quads, the next few reps will likely provide a poor stimulus. Moreover, those reps will likely be suboptimal in training the other muscle groups mentioned. This presents a scenario where all muscles involved aren’t receiving a great stimulus and the fatigue increases disproportionately as you approach failure - a “worst of both worlds” situation.
By training farther from failure in free-weight multi-joint movements, we may be able to provide a more targeted stimulus to the prime movers while sparing unnecessary fatigue due to shifting of loading demands. We could then use other movements to target the auxiliary muscle groups rather than trying to hammer a nail (provide an efficient hypertrophic stimulus to the lats and hamstrings) with a screwdriver (high bar squat). A final benefit is that training farther from failure could offer greater consistency; in other words, every rep looks nearly the same. This makes assessing progress easier as performance improvements very likely are coming from the prime movers rather than additional noise in the execution of the movement. This is a give and a take, though; it is generally more difficult to rate the RPE of sets farther from failure.
3. Low Fatigue Training May Potentiate Future “Traditional” Hypertrophy Training
A final and much more speculative possibility is that low fatigue training might be able to potentiate future training that is more along the lines of “traditional” hypertrophy training. To be clear, the data on resensitization is far from conclusive. We will mention some preliminary data later in this section, and we have witnessed the phenomenon enough in our coaching practice to take the idea seriously.
We started considering this idea when Josh, Jake, and I independently came to similar conclusions that intensity techniques such as myo-reps and drop-sets subjectively seem to be effective for a few weeks but then get stale rather quickly after that. We’ve also observed that when athletes needed to take a large step back (inevitably reducing proximity to failure) following an injury, the rates of progress once “normal” training was resumed would often surpass where they were prior to the injury, even when they returned to baseline strength. Again, these are simply subjective observations subject to our biases, but we found it interesting that we all came to similar conclusions independently.
Based on these speculations, low fatigue training might offer a way to maintain training volume, provide a solid hypertrophy stimulus, and also potentiate the effects of further higher fatigue training (taking most sets closer to failure). This would fit into a periodization scheme that starts considerably lower than typically recommended on the RIR spectrum but progresses steadily towards failure throughout the macrocycle (Figure 1).
Figure 1: This figure omits reductions in training stress/volume from deloads and intro weeks throughout the macrocycle. Notice that load must be high in the ‘Low Intraset Fatigue Phase’ to ensure the hypertrophy stimulus is high with higher RIR’s. To reemphasize, this graph is simply conceptual and largely speculative.
There is some preliminary data indicating this concept may be effective. A recent study by Carvalho and colleagues demonstrates how a lower volume strength phase might potentiate further hypertrophy training. A major caveat with this study is that the absolute changes in muscle thickness were rather small, which should make us cautious in how we interpret these results. Again, we view this data as preliminary. It’s also important to point out the general consensus that the research investigating the benefits of periodization for hypertrophy isn’t very convincing. However, this is often examining the manipulation of load (% of 1RM) rather than proximity to failure, which may be a more effective strategy for those focused on muscle growth for the mentioned reasons.
Conclusion
Overall, we think there is potential utility of low fatigue training in a hypertrophy-focused training program. Again, the research on proximity to failure for muscle growth is far from conclusive, and we are not saying that training farther from failure is better. We just want to put more options on the table.
Throughout this article, we mentioned multiple anecdotes. I also want to acknowledge that there are plenty of anecdotes on the other side of the aisle (i.e., training to or close to failure). Many iron enthusiasts claim there is a significantly greater stimulus for growth induced during the last couple reps to failure. While we’re not convinced this is the case based on the current research (One, Two), we also value this perspective.
The potential utility of low fatigue training pointed out in this article applies best to multi-joint exercises. For example, breaking up the total volume on a high bar squat into more sets to spare fatigue can be really useful, but doing so on a bicep curl is probably unnecessary. Apply these ideas critically and understand that they do not have to be all or nothing. Use the evidence as a compass to guide you to potential strategies. Then, update your mental model with what you observe from the individual athlete.
We hope the layer of caution on this article is clear. We’re not saying to go out and never train close to failure. Research is an ever-evolving process, and recommendations should be continually updated. We do not claim that this area of research is settled.
Practical Applications
Cost-Benefit Analysis:
We like to frame the utilization of these ideas as a cost-benefit analysis (Figure 2). The cost (fatigue) of training to or close to failure may outweigh the benefit (hypertrophic stimulus) in the context of multi-joint exercises like the squat or bench press. However, this cost-benefit analysis may not be the same in the context of single-joint movement like bicep curls where the accumulation of excessive fatigue is not nearly as big of a concern. Finally, it's important to note that this analysis is relative to the individual; for example, some individuals may be able to tolerate a greater amount of training volume accumulated from sets taken to or close to failure than others.
Figure 2: If there is a meaningful cost to training to or close to failure for a given exercise for a given individual, experimenting with higher RIR sets may be warranted.
Exercise Selection:
This article pertains primarily to multi-joint exercises that may generate a considerable amount of fatigue per unit volume.
E.g., squat, deadlift, hack squat
Load:
To be confident training with higher RIR’s, use loads equivalent to a 10RM or heavier.
This is roughly >75% of 1RM
For some exercises, you may know your 1 rep max or an estimated 1 rep max that you can easily calculate a percentage from, but here are some other strategies to make this process easier:
1) Work up to a top set prior to your volume work of 1-4 reps at 1-4 RIR and calculate an estimated 1RM from this.
2) Use a higher rep “tester” set (e.g. 6-8 reps at 2-4 RIR) to roughly determine a 10 rep max load on that day. This set will allow for an accurate RIR rating for most.
3) Utilize a previously known 10 rep max load from recent training. For example, if you used 175 kg for 8 reps at 2 RIR in a recent week/block, that can be used as a rough 10 rep max.
Repetitions per Set:
Our guidelines on this follow the below train of logic:
1) Select your load (e.g., 80% of 1RM or ~185 kg)
2) Select your total amount of repetitions (e.g. 18 total repetitions)
3) Break up those repetitions into the amount of sets you feel is logistically feasible. The more you break the work up, the more fatigue you theoretically spare. Be sure to consider other variables such as fatigue from unracking the bar for each set.
Tempo:
All repetitions should be performed with maximal concentric intent. This is likely necessary to match the hypertrophic stimulus when staying far from failure since this probably helps to maximize motor unit recruitment at a given load.
Volume and Frequency:
An advantage of training far from failure is less fatigue and muscle damage per set. Due to this, you may be able to complete more weekly volume and/or use higher frequencies.
Rest Periods:
If using more sets to equate relative volume, rest times should be autoregulated to manage total training time. We recommend resting long enough so that your subjective perception of bar speed is not decreasing set to set.
Additional Reading:
We have a free RPE/RIR guide that integrates our thoughts on the topic for both strength and hypertrophy.
Check it out here