Some researchers believe some sets should be taken to complete muscular failure, while others believe you should stop just short of failure. Lifters use what is called repetitions in reserve (RIR), which is the number of reps away from failure or reps left in the gas tank.
The Science Behind Reps in Reserve: How It Affects Your Muscle Growth SUMMARY
- Reps in Reserve are a valuable way of measuring workout fatigue during a training plan.
- Sets do not need to take sets to complete muscular failure; studies have shown that stopping short of muscular failure results in similar muscle growth.
- Most sets should be stopped with 1-2 reps before muscular failure for optimal increases in muscle growth.
WHAT DOES RPE MEAN IN LIFTING?
RPE stands for the Rate of Perceived Exertion (RPE). People can gauge exercise intensity on a scale of 1-10. RPE can be used for measuring exercise intensity levels during running and HIIT training. If you are sprinting and, let’s say, you could possibly run for 2 more seconds, that would correspond to an RPE 8.
You may hear people talking about using an RIR scale while lifting (For example, RIR 3). What does RIR mean? RIR stands for Repetitions in Reserve RIR) and was explicitly designed for weightlifters. RIR measures how many reps you could have done before reaching complete muscular failure.
REPS IN RESERVE (RIR) VS RPE
RPE vs RIR are used interchangeably to measure the intensity of exercise, but there are differences. RPE is a broad range of gauging exercise effort, whereas reps in reserve (RIR)is a more accurate way of gauging effort. For example, some people can tolerate more pain during exercise. Two people can both be at an 8 during exercise (i.e. 1-10 exercise exertion level), and one can last longer, whereas the other will stop very shortly. In an RIR, you are gauging the number of repetitions you could have possibly done before technical failure (i.e., complete muscular failure).
RIR or Repetitions in Reserve and RPE basically measure exercise intensity levels, but reps in reserve is specific to weightlifting and bodybuilding. For example, in weightlifting, two people’s 8 RPE can be very different. For example, a beginner just starting to lift a weight will feel he is at an 8 if effort level, but in reality, he is at a 6. A very useful tool is an RPE calculator to measure what 1 RM percentage (i.e., rep max).
Reps in reserve is a more useful gauge because it measures how many repetitions they could have performed before reaching failure. RIR is a more useful approach to gauging effort levels during resistance exercise.
10/19 RESEARCH UPDATE: YOU CAN TRAIN FURTHER AWAY FROM FAILURE THAN PREVIOUSLY THOUGHT AND STILL MAKE STRENGTH GAINS!!!
The newest research suggests that you can train further away from failure and still gain strength. Training to failure is associated with more neuromuscular fatigue and less gains in strength. The research on velocity-based training has found that training further away from failure is better for strength gains, whereas training closer to failure is better for muscle growth.
REPS IN RESERVE STUDY
An exciting abstract was recently published, which suggests that you can train further away from failure than previously thought. Researchers took 14 resistance-based males and divided them into two groups of squats:
A.) One group trainer with an RIR (Reps in Reserve) of 4-6,
B.) The other group trained with an RIR of 1-3.
RIR is an indicator of how close to muscular failure you are training. If you are training with an RIR of 1-3, this means you are training at a relative intensity in which a person is 1-3 reps away from muscular failure. Most lifters would suspect that the group training further away from failure would gain less strength, but that’s now what the researchers found.
RESULTS
The group that trained with a 1-3 RIR or those that trained closer to failure trained at a higher intensity and performed more repetitions (i.e., higher volume), but strength gains were similar between groups. The researchers found you can make similar strength gain training further away from failure (i.e., 4-6 reps away from failure) compared to those that train closer to failure (i.e., 1-3 reps away from failure.). The full article is yet to be published, but this research aligns with other research suggesting that if strength gains are your main goal, limit the number of sets in which you are training to failure. If you are involved in sports, you can maintain your strength throughout the season while training further away from failure.(12)
ABSTRACT: ACSM 2022 Conference. Effect Of Proximity To Failure During Resistance Training On Back Squat Strength. Zac P. Robinson, Christian T. Macarilla, Nicholas M. Sautter, Matthew C. Juber, Landyn M. Hickmott, Rebecca M. Cerminaro, Brian Benitez, Jacob F. Remmert, Joshua C. Pelland, Thomas A. John, Ethan Elkins, Shawn Dinh, Seth R. Hinson, Laura C. Canteri, Eric R. Helms, Robert F. Zoeller, Michael Whitehurst, FACSM, Michael C. Zourdos. Florida Atlantic University, Boca Raton, FL.
REPETITIONS IN RESERVE (RIR) MEANING
Some researchers believe some sets should be taken to complete muscular failure, while others believe you should stop just short of failure. Lifters use what is called repetitions in reserve (RIR), which is the number of reps away from muscular failure or reps left in the tank. For example, it is recommended that for hypertrophy, most of your lifting should be an RIR of 1-2. Meaning you perform sets until near maximal failure with 1-2 repetitions left before complete voluntary muscle failure. One of the best metrics to use whether you are close to failure is rep speed velocity. A relationship exists between repetition velocity and proximity to failure.[1]
If you watch a person lift the weight, you will notice a noticeable decrease in how fast the weight moves toward the end of the set. This is where RIR begins. If you are doing a set of bench presses for eight repetitions, but you could have done two more reps before complete muscular failure, then your RIR or reps left in the gas tank is 2.
REPS IN RESERVE ISSUES
The biggest issue with gauging RIR (i.e., exercise intensity effort level) is that RIR is highly variable among subjects. Untrained lifters tend to underpredict how hard they are exercising and are more accurately able to gauge how close they are to failure when fewer reps are performed.[2] This means that untrained lifters are more likely to know how close they are to true failure when doing a max set of 8 reps compared to a set of 30 reps. However, well-trained lifters are much more accurate in determining how close to failure they are. [3]
One drawback of super high rep training (>30 reps) is that it’s much harder to gauge whether you are training to complete muscular failure. For example, anyone that has ever done high-repetition squats knows how exhausting it is on the body. Did you stop the set because of cardiovascular fatigue, or are you training your muscle to complete failure?
For example, you can jump rope before a set of squats; it’s not your leg muscles that are being taken to the point of failure, your heart rate is elevated, and your cardiovascular system is taxed rather than your muscles. The same concept applies with high-rep squatting (> 30 reps); cardiovascular fatigue is more likely to stop the set than maximal muscle fatigue.
GAIN SIMILAR AMOUNTS OF MUSCLE WHILE NOT TRAINING TO COMPLETE MUSCULAR FAILURE
- Repetitions to failure with low load (30% of a 1RM); ∼34.4 repetitions) = +7.8%
- Repetitions to failure with high load (80% of a 1RM); ∼12.4 repetitions) = +8.1%
- Repetitions not to failure with low load (30% of a 1RM); ∼19.6 repetitions) = +2.8%
- Repetitions not to failure with high load (80% of a 1RM); ∼6.7 repetitions) = +7.7%
All the groups, except those that used light weight and stopped short of failure (i.e., not a statistical increase in muscle growth compared to the other groups), gained roughly similar increases in muscle mass. All the failure groups had exertion or intensity of effort levels at max or close to max. The heavy load group that stopped short of failure average exercise level was about a 5 RIR (~80% of a 1RM).
RESULTS OF REPS IN RESERVE STUDY
The group that trained with 80% until failure averaged 12 repetitions, yet the group that used 80% and performed 7 repetitions (i.e., stopped 5 reps short of failure) gained the same amount of muscle mass. This suggests that 5 RIR should be the minimum that you stop short of failure for increasing muscle growth.[4] It should be emphasized this is a single study, but it suggests that 5 RIR is the minimum for muscle growth. Many of your sets should be in the 2-3 RIR range.
RIR
It does not matter what weight you are using either; whether you are doing reps of 20 or reps of 12, the last five reps seem to be the most critical for muscle growth. You can do certain things to psychologically push you closer to hitting your RIR numbers, such as listening to your favorite music, having a spotter, and reducing mental fatigue. Typically, your RIR will drop by 1 RIR with each successive set. As you progress through your training cycle, fatigue is inevitable. Fatigue cannot be eliminated, but it can be managed.
At the end of the study, training further away from failure had the same muscle growth as the group training to failure.
Repetitions in Reserve: TRAINED LIFTERS MAY BE ABLE TO TRAIN FURTHER AWAY FROM FAILURE
There is evidence that trained lifters can train with an intensity further away from failure and still make impressive gains in muscle growth. This is a highly controversial study, but researchers trained subjects with 80% of 1RM. The total volume was equal; one group trained with an estimated 5-7 RIR (far from failure), and the other group trained to complete muscular failure.
At the end of the study, the group that trained further away from failure had the same muscle growth as the group training to failure. Again, this is one study, but it suggests that advanced lifters may be able to train further away from failure; and still gain muscle! Other studies have replicated these findings by finding that training with a heavier weight and further away from failure (4+ RIR) can see similar growth to groups training closer to failure (0-3 RIR).[5]
Remember that training with a light weight (i.e., 30% of a 1RM) and avoiding failure results in inferior muscle growth. These studies provide valuable insights for those looking to manage workout fatigue; advanced lifters can train further away from failure while benefiting from increased recovery and muscle growth.
Repetitions in Reserve:
Muscle growth is more dependent on the level of effort and less on the amount of weight you are using and rep ranges. Muscle hypertrophy occurs with both light and heavy weight provided the intensity of effort is sufficiently high. If you are performing enough sets and using a full range of motion with suitable form, you may be able to train with 1-2 reps away from failure. Many repetitions can stimulate muscle growth if they are taken close to failure.
*If you are a personal trainer, you should not only track their sets and reps but also monitor how hard they are exercising, such as I could have done 3-5 more reps (add more weight or reps next session), I could have done 1-2 more reps (i.e., sweet spot), that was extremely hard (i.e., back off the next set).
The intensity of effort is an important variable for increasing muscle growth. When you start a new training cycle, start with around 4-5 reps in reserve, and as the volume increases, progress from 4 to 5 to approximately 0-1 the last week of your training.
GRADUALLY DECREASE YOUR REPS IN RESERVE AS THE TRAINING CYCLE PROGRESSES
Starting a new training cycle with 0-1 RIR means the training stimulus is too high, leading to overtraining as the volume progresses. A recent study found that gradually increasing RIR over 12-weeks (i.e., 3 blocks) was superior to % of a 1RM for increasing strength despite using a similar training volume.
In the RIR group, subjects in blocks one and two (weeks 1-8) increased RIR increased from 4 RIR in week one to 1 RIR in week four); in block three (weeks 9-12), they did sets that increased from 2 RIR in week nine to 0 RIR in week 12). The % 1RM group did sets with 65%-72.5% in block one; in block two, they used sets with 77.5%-85%; in block three, they did sets between 87.5%-95%. In each % 1RM block, there was a 2.5% increase per week.
The difference between the groups was that the RIR group allowed the lifters to adjust loads based on how they were feeling on that day, whereas the %1RM had to train with a fixed weight that day. The group using RIR had superior increases in strength due to using heavier absolute loads over the 12-week training period. The RIR group increased front squats by 11.7% versus 8.3% with fixed loading.
RESULTS
The RIR led to a 10.8% increase in strength compared to 7.1% for fixed loading for back squats.[6] Some of the superior strength increases using RIR were because of the ability to not use a maximal effort each set and not training to failure except in the last week of the training program. Remember that multi-joint exercises like the squat are more fatiguing than single-joint exercises like the machine preacher curl. It’s more likely that you can train single-joint exercises like arm curls and triceps extensions to failure with less overall strain on the nervous system than taking multi-joint exercises like the squat and deadlift to muscular failure.
WHY MORE WEIGHT DOES NOT ALWAYS LEAD TO MORE MUSCLE GROWTH
It’s well known that muscle activation increases with increasing exercise intensity. Therefore, light weight exercise taken to failure can stimulate muscle growth. This is due to the muscle fiber fatiguing, resulting in greater activation of Type II fibers similar to training with a heavy weight.
Also, the same principles apply to BFR training, which uses a very light weight, but can increase muscle growth similar to heavy weight because of the high levels of fatigue and metabolic stress. As you add more weight, muscle activation will not further increase at a certain point, and other muscle groups increase in activity. Your goal is to build muscle, not see how much you can lift in the gym.
BFR STUDIES
A moderate weight can often result in more muscle activation and better exercise form. For example, researchers had subjects train on the bench press with 70%, 80%, 90%, and 100% of their 1RM.The Pec EMG (i.e., chest muscle activation) reached its maximum at about 70%.
Beyond 70%, the anterior deltoid and triceps started to dominate at higher weights. Interestingly, you experience greater pec activity at 70% than at 100%.[7]
The squat comparison of 80%, 90%, and 100% of a 1RM yielded similar findings.
Researchers observed increases in muscle activation only in the vastus medialis and gluteus maximus during 90% and 100% of a 1RM, respectively, compared to the activation levels during 80%.
There was no statistically significant difference in muscle activation between 90% and 100% for any muscle. Subjects using 100% RM resulted in a forward lean, which resulted in changes in hip joint kinematics. The author concluded that using 90% of a 1RM was safer and resulted in the same muscle activation as a 100% RM. [8]
EMG AND MUSCLE HYPERTROPHY
Caution should be emphasized by extrapolating “muscle activation” studies to muscle growth. There are no longitudinal studies to suggest increased “muscle activation” or increased EMG is predictive of muscle growth. [9] Jenkins et al. (2015) conducted an EMG study. When taken to momentary muscular failure, they found that 3 sets of 80% 1 RM caused greater muscle activation (i.e., greater EMG amplitude) than did 3 sets of 30% 1 RM. However, muscle growth increased in both groups. [10] This suggests that muscle activation is a poor method of predicting long-term muscle growth.
SQUEEZE THE MUSCLE
With experienced athletes, focusing on the muscle and actively “squeezing the muscle” can increase muscle activation of the arms and chest. Mentally focusing on a muscle has been found to increase the muscle activation of these regions during the bench press at relative loads between 20 and 60% of a 1RM. However, mentally focusing on a muscle resulted in no greater muscle activation above 80% of a 1RM. The researchers found that selectively focusing on a muscle has a threshold between 60%-80% of a 1RM. [11]
More weight causes more fatigue; you should keep the weight between 30-85% of a 1RM to stimulate muscle growth.
You can incorporate a system like Push/Pull Workouts. In this system, you structure muscle groups involved in pushing movements in one workout, allowing pulling muscle fibers to rest and train them on a separate day.
If you train your chest and biceps on Monday, the fatigue in your biceps from that workout might impact your back workout on Tuesday, reducing the volume the next day.Sample Push/Pull Routine
DAY 1: “Push” workout: Train all the upper body pushing muscles, i.e., the chest, shoulders, and triceps. Example: bench press, incline press, military press, dips
DAY 2: “Pull” workout: you train all the upper body pulling muscles, i.e., the back and biceps. Example: Deadlifts, Lat pulldown, biceps curls
Day 3: “Legs” workout: you train the entire lower body, i.e., the quads, hamstrings, calves, and abdominals. Example: Squats, leg press, leg curls.
Repetitions in Reserve Key Points
- Repetitions in Reserve are a valuable way of measuring workout fatigue.
- Sets do not need to take sets to complete muscular failure; studies have shown that stopping short of muscular failure results in similar muscle growth.
- For strength training, training further away from failure is beneficial.
REFERENCES
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