Table of Contents
- Read More Strength and Hypertrophy Articles
- Training frequency
- Isolation exercise vs. compound movements
- Exercise Order
- Training to failure
- Rest duration between sets
- Range of motion (ROM)
- Practical applications
- The limitations of fitness research
Training a muscle group 2-3 times per week seems to be better than 1 time per week for hypertrophy 11x per week is typical for the bro-split. In terms of strength, the picture is more unclear. More training days allow you to do more volume.
According to volume-unmatched research 2In studies with high-frequency and low-frequency training groups, the former will typically use higher volumes because they train more. Hence, volume is not matched, training a muscle group 2-3 times per week is superior to once a week for strength development (given that higher frequency = more volume). Remember that this recommendation doesn’t account for periodization. Several research teams think that sticking to one frequency year round is suboptimal.
Isolation vs. compound exercise
Isolation exercise has its uses in rehab, injury prevention, muscle imbalance correction, recovery, programming, and bodybuilding. There isn't much evidence that isolation exercise is required to maximize gains. At least not in “mirror muscles”. Yet, it is possible that a muscle group needs to be hit by different compound exercises to maximize growth (i.e. the bench press suboptimally stimulates triceps growth compared to the pectorals). Isolation exercise is particularly useful for certain muscle groups like calves, rotator cuff, etc.
You can order exercises based on how important they are to you and what your strengths/weaknesses are. The most important exercise(s) should be done first in the session if you want to maximize the amount of reps you can do. Debates are raging about what’s ideal for hypertrophy and strength. There’s a slight trend for better gains in the exercises you do first in a training session. However, we can’t say this is highly probable, because there’s not enough studies. Remember that science deals with probabilities rather than certainties.
Going to failure early in an exercise decreases the number of reps you can do in later sets and limits volume. Excessive use of failure can lead to overuse injuries, fatigue, overreaching, etc. Some researchers recommend going to failure occasionally, but the evidence is mixed and we don’t know what’s ideal for the long-term. You can make good gains without going to failure, but as always, it depends on other factors like frequency, intensity, volume, rest durations, and so on.
Rest between sets
Generally speaking, short rest periods reduce the amount of reps you can do in subsequent sets. Longer rests 3i.e. more than 3 minutes are better for developing strength and when you're training at high intensities to failure. For hypertrophy, you are free to choose your rest interval. You can choose shorter rests, but you have to account for things like: Did you go to failure? How many reps are you doing the exercise for? At what intensity? How important is it for you to hit your target reps per set?
Range of motion (ROM)
Full range of motion generally causes more muscle hypertrophy, but partial ROM can cause site-specific hypertrophy. Strength is specific to the ROM you are using, but you can gain strength 20-30 degrees outside of the ROM you train with. Partial ROM lifts can be used in addition to full ROM to break through sticking points or weak points. Trained and advanced lifters might want to periodically include partial ROM training into their programs.
- There is no cookie-cutter program that will be ideal for everyone, however some programs are better than others
- More frequency/failure/intensity isn’t necessarily better
- Individual variability (genetics, epigenetics) affects how your body adapts to exercise. If a program doesn’t work after months of trying, you might want to switch to something with different movements, frequencies, more/less volume, intensity, etc. This principle applies even if you’re doing something that is “ideal”, on paper.
Many studies use untrained college-aged men as participants, study durations are short (6-12 weeks), there is little ecological validity, and several of the studies have methodological issues. For more, read: Why study results don’t always apply to you (the limitations of research)
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This is part 1 of 3! Part 2 will include information on sets, reps, intensity, time under tension, and eccentric training. Part 3 will be about periodization.
We encourage you to always use critical thinking when reading fitness articles.
In this section, we mainly focus on the following question: if everything else is equal (i.e. volume, sets, reps, intensity, exercises, etc.) is it better to divide strength training volume over more days or fewer days?
How frequency affects hypertrophy
Volume-matched research (training frequency per muscle group per week)
In frequency research, participants are usually divided into two or three groups. For example 1x, 2x, or 3x per week. This refers to how often they train a muscle group per week. There are several ways to train a muscle 1x per week. You can train one day per week as a whole-body session, or you could split the 1x into multiple days (one body part per day). Hence, you can train multiple sessions a week but only have 1x training frequency per muscle group. On the other hand, you can do a 3x program (per muscle group per week) and only do three whole-body sessions.
When testing different frequencies, it’s important to give groups similar programs. To figure out whether high frequency or low frequency is best, we need to make sure both groups use the same amount of volume per week. Volume-matched means that two programs have the same weekly training volume, even if they train a muscle group with different frequencies per week. In studies where volume isn’t matched, high-frequency groups tend to do more volume.
Below is an overview of volume-matched research that looks at hypertrophy.
Note: Most of the research listed above didn’t reach statistical significance when looking at outcome differences between groups. This is probably because the study durations were too short, and because there were too few participants in the studies (amongst many other reasons!). This makes the studies underpowered. Hence, they wouldn’t be able to detect statistically significant differences even if they existed. However, the studies on the left trended towards being better for higher frequency.
Some might argue that the research presented above actually didn’t support higher-frequency training because results weren’t statistically significant (when comparing gains between groups). In other words both groups got the same gains if we look at it from the point of view of statistical significance. However, as I wrote in the paragraph above, if a study is underpowered, it’s meaningless to look for significant differences. It’s much more valuable to look for effect sizes, aka the differences between the groups (i.e. compare percentage % gains):
"The widespread practice of interpreting p values as evidence in support of hypothesized effects constitutes a blatant disregard for the limitations of statistical significance testing." (Ellis, 2010)
Please read the frequency limitations section for more details
Moving on from this issue, a recent meta-analysis by Schoenfeld et al. (2016) looked at most of these studies. In agreement with the table above, they found that training every muscle group twice a week is better for hypertrophy than once a week. This is because most of the evidence shows a positive trend for training a muscle group twice a week for hypertrophy.
Here are our thoughts on the meta-analysis by Schoenfeld et al., 2016:
- Strengths of the meta: across a wide range of different trials, we see a consistent pattern that favours higher-frequency training, even with substantial heterogeneity between trials.
- Weaknesses of the meta: The meta could have discussed the limitations of the studies at greater length: several studies had (post-menopausal) obese women, mostly untrained participants, low-quality methodology, lacking randomization and in some studies the participants self-selected which group they wanted to be in, women and men were unevenly mixed in groups, low-quality body composition measurement tools (BodPod, BIA, limb circumference), major strength differences at baseline, short durations, heterogeneity, etc.
- Final thoughts: There seems to be a trend that favours training a muscle group twice per week for hypertrophy, rather than once per week. However, most of the studies are limited by many factors. And if the overall study quality levels were higher, we might see different results. Also, most of the studies apply to untrained populations, and several of the studies examine older women. Most studies are also very short, which means we don’t know whether a higher-frequency program is better in the long-term (i.e. a year):
"Although increasing the training frequency may provide greater muscle growth, it may be difficult to increase the training frequency beyond a certain point. We propose that once an individual has been training at a higher frequency for a sufficient duration (e.g., 16 weeks), it may then be beneficial to decrease the training frequency for a period of time (e.g., 24 weeks)." (Dankel et al., 2016)
Several recent reviews now state that a training a muscle group 1x per week (“bro-split”) is non-ideal for hypertrophy (Schoenfeld et al., 2016; Dankel et al., 2016) while some disagree (Fisher et al., 2013; Gentil et al., 2015). In a study where subjects did bro-splits, the lower-volume group had better gains than the higher-volume group (Amirthalingam et al., 2017). Meaning that doing a lot of volume on one day might not be ideal (Helms et al., 2014). So, for natural athletes there doesn’t seem to be much reason to dedicate training days to a single body part (though it might be different for enhanced athletes or elite lifters?).
It should be said that the research we have on frequency right now is mostly low/medium quality (the Schoenfeld et al., 2015 study and 2016 meta being exceptions), and it’s mostly done with untrained, old, obese, (etc.) participants. There is very little research on healthy, young, trained, men/women. We’re not aware of any frequency hypertrophy research on elite/advanced lifters.
Non-matched volume research (training frequency per muscle group per week)
How frequency affects strength
There aren’t many high-quality studies that examine high-frequency muscle-group training vs. low-frequency muscle group training when it comes to strength. Most of the studies are on the untrained elderly, etc. Some volume-matched studies suggest that training a muscle group more (i.e. 2-3x per week) is better than 1x per week, but much of the data is mixed as you can see in the table below.
Volume-matched research (training frequency per muscle group per week)
Non-matched volume research (training frequency per muscle group per week)
In these studies, higher training frequencies implies higher weekly training volumes. Here we see more studies supporting the notion that higher training frequencies (2-3x per muscle group per week) are better for strength development. This shouldn’t be surprising given that more volume usually means more gains, whether it is strength or hypertrophy.
Higher frequency = more volume. Figure by McMaster et al., 2013 (edited for clarity)
We don’t really know how frequency affects trained and elite lifters, because there aren’t many studies that compare low-frequency to high-frequency in a volume-matched manner, in these lifters (Helms et al., 2014). Though we have an interesting case-series on three well-trained powerlifters (Zourdos et al., 2015). The study shows that three lifters are able to make good progress with daily 1RM training (they didn’t compare different groups).
Figure: Changes in squat 1RM after 36 days of daily 1RM squat training (Zourdos et al., 2015)
Very high frequency training should probably only be done in blocks, because it is unsustainable in the long-term (Fry et al., 1994; Zourdos et al., 2015; Schoenfeld et al., 2016). As some point out, it’s important to look at how you respond as an individual (Helms et al., 2014).
"It is unlikely this type of training can nor should be maintained year-round and rather may be more appropriate as a single intensity block (mesocycle) to peak for competition within a macrocycle of sound periodization principles. Furthermore, it is advisable that only lifters with multiple years of training experience and technical proficiency should engage in daily 1RM training; novice/ intermediate trainees can make progress with much lower volume/ frequency and should take advantage of the opportunity to progress with less demanding training" (Zourdos et al., 2015)
Indeed, 2 weeks of daily squat training for 10 sets (1RM) per session was detrimental for a group of trained lifters (Fry et al., 1994). Though their strength loss could simply be a result of them overreaching. It’s possible their strength would super-compensate and exceed their previous 1RM if the researchers waited for 1 more week before testing. After the study was over, two of the subjects in the overtraining group were diagnosed with overuse injury of the knee. Questionnaires of the lifters show that they didn’t look forward to the daily sessions.
Figure by Fry et al., 1994 (edited). Lifters had 4.5 years mean experience, minimum of 1.5x bodyweight squat.
Conclusions for frequency (strength and hypertrophy)
If we look at all the evidence as a whole with all of its limitations, we can conclude that higher frequency training (i.e. 2-3x per muscle group per week) might be better than 1x per week. Nonetheless, frequency shouldn’t be an unchangeable or permanent factor. It’s highly likely that long-term high frequency training (i.e. 3x-7x per muscle group per week) can lead to overreaching, injury, and fatigue. Thus, it might be a good idea to use moderate frequencies (i.e. 1-3x) as a foundation for your program, with periods of intensified training (i.e. 3-6x). There are many ways to play around with this, and due to practical considerations (i.e. time, interest), genetics, and inter-individual differences, there’s no answer that will fit everyone. It should be said that substantial gains can be made with low frequency training, and the differences when volume is matched, are not huge.
Limitations of frequency research
When it comes to hypertrophy, painfully little volume-matched research has been done on the frequency of strength training. Volume-matched means that two groups use the same weekly training volume, even if they train a muscle group with different frequencies per week. In studies where volume isn’t matched, high-frequency groups tend to do more volume. This poses a problem, because we don’t know for sure whether the study outcomes (i.e. gains) are a result of the higher frequency, or higher volume (Serra et al., 2015).
With that said, volume and frequency have a symbiotic relationship. A low training frequency strongly limits the amount of volume you can do (Serra et al., 2015), unless you spend several hours in the gym per session. Some studies also suggest that it’s not necessarily better to do a ton of volume in one session (Amirthalingam et al., 2017). Hence, the higher training frequency you have per week, the more total volume you can do.
Another issue with most frequency studies is that they have very small sample sizes (Crewther et al., 2016), which limits their statistical power (Purcell et al., 2003; Ellis, 2010). As we see in many of the studies, high frequency training tends to be better for hypertrophy and strength. However, these results often do not reach statistical significance, likely due to lacking power.
Ideally, we’d see authors do a power analysis to see if their study is sufficiently powered to detect differences between groups. If a study with a small sample size finds no differences between two groups, we need to see calculations that show their study was sufficiently powered to detect these differences if they exist. If they haven’t done a power analysis, we can’t say whether they made a type II error or not.
The graph below shows us how sample size (number of participants) is connected to power, and effect size (the magnitude of the difference).
As you can see, power is very low when we have 10 participants per group (which is standard in fitness research) and we need to see very large effect sizes (differences between groups) to reach statistical significance. If we follow convention and aim for 80% (0.8) power, we need large effects or large sample sizes. In fitness research the effects are usually small, and so are the sample sizes. Hence, studies aren't likely to detect a difference between groups even if it exists.
Isolation exercise vs. compound movements
Most programs are built around a couple of main compound movements. Most of the emphasis is placed on improving these main lifts like the bench, squat, overhead press, and deadlift. Though when it comes to strength and hypertrophy, would we benefit from adding “isolation exercises” (aka single-joint movements)?
Some research groups would say that no, isolation exercises are not necessary since they don’t give us extra benefit and they are time-inefficient (Gentil et al., 2013; Gentil et al., 2015; de França et al., 2015; Gentil et al., 2016).
"In order to save time [we] can choose exercises that target a higher number of muscle groups at a time. This strategy can increase training volume and reduce the time commitment, which, in turn, may improve exercise adherence since lack of time is the most cited barrier for an individual engaging in any exercise program (20-23)." (Gentil et al., 2015)
Others point out that isolation exercises gives trained lifters more DOMS for a longer period of time (Soares et al., 2015).
Figure by Soares et al., 2015 showing how an isolation exercise increases DOMS to a greater extent compared to a compound exercise in lifters with 5 years experience. The 72 hour DOMS might be because the exercises were unfamiliar to the participants (DOMS is stronger and lasts longer when you do unaccustomed exercises, even if you’re highly trained). Though, we should note that DOMS only lasted 48 hours when doing the compound exercise.
However, this doesn’t necessarily mean that it takes longer to recover from isolation exercise. In fact, one study reports the opposite: it seems to take at least 48h hours to properly recover compound exercise performance for most participants (Korak et al., 2015). The 48+ hour recovery recommendation is supported by others as well (McLester et al., 2003; Jones et al., 2006). Though there seems to be a lot of inter-individual variability (people recover differently) and 48 hours isn’t a “rule” or “law” that applies to everyone (Bishop et al., 2008). Also, since recovery is muscle and exercise-specific, this opens up to the idea that we can switch between which muscle groups and compound exercises we train from session to session to optimize progress.
It is also possible that the body will adapt to a high-frequency program over time and that performance is maintained between sessions. Though this remains speculative until we see specific studies testing this hypothesis over a longer period of time. See Frequency section for more.
Figure by Korak et al., 2015 shows that only 30% of the participants (trained lifters) had recovered completely 24h after doing compound exercises (i.e. deadlift, bench, leg press). To determine recovery, they measured how many reps the lifters could do, compared to last session. 70% of the lifters had recovered in all compound lifts after 48 hours. Though some individual lifts recovered faster in some individuals:
Figure by Korak et al., 2015: Some lifts recover faster than others
Several research teams agree that isolation exercises have their use, namely for bodybuilding and for correcting muscle imbalances that usually affect the rotator cuff, hamstring, and hips (Tovin, 2006; Ferreira et al., 2016; Gentil et al., 2016). They also note that we might need to add isolation exercises for muscles that aren’t worked directly by compound movements (Gentil et al., 2016).
Some studies and articles speak against Gentil et al’s conclusions that isolation exercises are generally unnecessary (Kompf and Arandjelović, 2016; Ribeiro et al., 2016): Beginners who trained the bench press for 6 months increased their pectoral CSA (hypertrophy) by ~37% while their tricep CSA only increased by ~20% (Ogasawara et al., 2013). This could mean that isolation movements might need to be added for maximal tricep gains. Though, they only trained bench press in this study (they didn’t do a whole-body program). It’s possible the tricep would catch up if they did other compound exercises that included the tricep, like overhead presses and dips.
Some studies show that muscle activation and hypertrophy varies depending on which exercise we do (Bryanton et al., 2012; Wakahara et al., 2012; Wakahara et al., 2013; Schoenfeld et al., 2014; Matta et al., 2015; Wakahara, 2015; Mendez-Villanueva et al., 2016). This could mean that it’s important to hammer a muscle with different types of exercises to get optimal growth (Antonio, 2000). But this remains slightly speculative until we get more studies.
Figure by Ogasawara et al., 2013 (red lines & text added by us): TB = triceps brachii, PM = pectoralis major, CSA = cross-sectional area (hypertrophy). This study suggests that compound exercises like the bench press leads to solid pectoral growth, but suboptimal tricep growth.
The question “should we add isolation movements to a compound program?” can be approached from many angles: first, we have to identify which muscle(s) we are talking about. Some muscles are usually trained much more than others. For example, the quadriceps are worked through a long range of motion in the squat exercise (given high bar to depth). But what about the calves? They are somewhat stimulated in the leg press, squat, and deadlift, but the range of motion is very short (Ribeiro et al., 2016). We could make the case that muscle groups like calves and rotator cuffs need to be trained separately from the lower-body compounds. Indeed, some muscles and muscle groups are notoriously undertrained compared to their counterparts (compare rotator cuff and posterior deltoid to the anterior deltoid which is included in basically every upper-body pressing exercise).
When calculating how many weekly sets to do per muscle, we should include muscles that are worked by compound movements (Ferreira et al., 2016). For example, we could say that a bench press set means 1 set for pec + 1 set for tricep + 1 set for anterior deltoid. However, Ogasawara et al’s (2013) study suggests that maybe we should only count “partial sets” for some muscles. What we mean by that is for every bench press set, we count it as 0.5 sets for the tricep. This way we acknowledge that the tricep is involved and stimulated, but we also acknowledge that the stimulus is suboptimal. So if you’re looking to do 20 sets for the tricep per week, 10 sets of bench will only get you 1/4th of the way to that volume goal.
Beyond hypertrophy and strength, muscle weakness or imbalance could increase injury risk (Baumhauer et al., 1995; Wang and Cochrane, 2001; Croisier et al., 2002; Tovin, 2006; Kolber et al., 2010; Witchalls et al., 2012; Bourne et al., 2015; Gentil et al., 2016), though we still need more evidence before we can accurately predict injuries in certain sports (McCall et al., 2015). Using isolation exercise could be an effective way to correct muscle imbalances and lower injury risk (“prehab”) (Gentil et al., 2016). For example, external rotations (rotator cuff exercise), decreases risk of shoulder impingement (Kolber et al., 2014). Isolation work could also help us overcome “sticking points” in compound exercises (Kompf and Arandjelović, 2016)
"When the serratus anterior becomes fatigued, the scapula fails to protract and upwardly rotate and the subacromial space may be compromised" (Tovin, 2006)
"Individuals with a muscle strength imbalance as calculated by an elevated eversion-to-inversion strength ratio (>1.0) had a higher incidence of inversion ankle injury." (Baumhauer et al., 1995)
To conclude this section, the choice of compound vs. isolation exercise goes beyond the issues of strength and hypertrophy. Isolation exercise has its uses in rehab, injury prevention, muscle imbalance correction, recovery management, programming, and bodybuilding (Tovin, 2006; Korak et al., 2015; Kolber et al., 2010; Gentil et al., 2016; Kompf and Arandjelović, 2016). There’s evidence that it could improve hypertrophy in muscles that are only indirectly targeted in compound movements (i.e. rotator cuff muscles, posterior deltoid, calves, hamstrings) but it’s unclear whether it will improve hypertrophy and strength in “mirror muscles” that already get a lot of stimulus via compound movements (pectorals, quads, anterior deltoid, etc.). Thus, it’s probably a good idea to do calf raises and external rotations to reduce injury risk and improve hypertrophy in these relatively unstimulated muscle groups.
Some organizations recommend that multi joint exercises should be placed at the beginning of a training session (ACSM). In our article, we refer to volume and frequency as two of the most important factors when designing a program. So, if you’re doing enough total volume does it matter what order you do exercises?
Anecdotally, it makes sense to work large muscle groups before small muscle groups. If we pre-fatigue a smaller muscle like the tricep with isolation exercises, we may not be able to use as much weight on the bench press to overload the chest.
One of the first studies to look at exercise order used an acute test (Sforzo and Touey, 1996). They used a crossover design where the same trained subjects completed a small to large workout or a large to small workout. Using four sets of 6-8 rep max with popular exercises like the squat, bench, leg curl, tricep extension, etc. The results suggest that when smaller muscle groups were trained before larger muscles, the subjects did less total volume (Sforzo and Touey, 1996).
Several others have gone on to do acute studies and most of the research agrees that placing an exercise first in a training session, allows you to do more repetitions for that exercise (Sforzo and Touey, 1996; Spreuwenberg et al., 2006; Miranda et al., 2010; Simão et al., 2012; Soncin et al., 2014; Soares et al., 2016, Romano et al., 2013). But some disagree (Shelkholeslami-Vatani et al., 2016).
As you get further into your workout, it’s possible that you induce more central fatigue even if you switch muscle groups. This fatigue could make you less confident in performing a lift later in the workout - so you lift less overall (Simão et al., 2012). Imagine doing a 1RM deadlift after a high volume leg day. We will do a full review on central and local fatigue in the future.
“Muscle fatigue increases the variability of movements, changing the strategies of biomechanic coordination and / or a muscle activation pattern.” - Soncin et al., 2014
In a study by Shelkholeslami-Vatani et al., 2016, they used two exercise orders in untrained men. One group worked small to large, and the other group worked large to small muscle groups. There was no significant difference between the duration and volume of the training protocols. They found placing an exercise late in the session reduced the number of reps lifter were able to do, regardless of the amount of muscle involved. Overall, the groups completed the same total number of reps. Yet, Rating of Perceived Exertion (RPE) was higher in those who worked from smaller muscles to larger. This same result was found in other studies as well (Simoa et al, 2005).
If the training session is not supervised by a coach or trainer, higher RPE could cause a reduction in volume/load (lack of adherence) (Mazzetti et al., 2000, Coutts et al., 2004, Gentil and Bottaro, 2010, Amagliani et al., 2010). One exception to this is teenage boys (Romano et al, 2013) who were able to do the same number of reps per set even when going to failure - in 3 sets using different exercise orders. The authors speculate this may be because younger subjects can’t produce as much force. Some suggest adolescents also recover better from fatigue (Falk and Dotan, 2006). Oddly, this study found an increase in RPE during the first exercise session for one of the exercise sequences.
Exercises that are done later in a training session could be negatively affected by the buildup of fatigue. In other words, less repetitions can be done per set when the exercise is placed late in the workout. To add some practical application to the mix - it seems that women can withstand more volume than men. We’re sure Lyle’s new book will cover the gender differences more in depth.
In an athletic population acute power production could be affected by exercise order. Spreuwenberg et al. compared performance for 4 sets of 85% 1RM squats when completed before or after a whole-body exercise routine (2006). Much like the previous studies - subjects could do more repetitions if squats were done first in the workout. Surprisingly, the average power for each set of squats was higher when performed last in the workout. This indicates that we might need different recommendations for different sports.
“athletes aiming for maximal strength gains should perform multi-joint muscle group exercises first in a session and athletes striving for maximal power gains may perform a power-type exercise before strength-type exercises” - Spreuwenberg et al., 2006
So far it seems we can do more reps for a given exercise if it’s done at the beginning of the session and it’ll have a lower RPE than if done later in a training session. Does it matter in the long run? Well, Dias et al tested this on 48 young untrained men. They assigned lifters into a large to small group, and small to large group exercises (like the acute studies previously mentioned). After 8 weeks of training 3x per week they found no differences in strength between groups for the large muscle groups. There were also no differences in total work performed. But as you can see below, the group that did bench press and lat pull-down first, improved those exercises the most. The same is true for the group that started with triceps extensions and biceps curls.
Figure from Dias et al., 2010
Black = Order: Bench press, lat pulldown, shoulder press, bicep curl, tricep extension
White = Order: Tricep extension, bicep curl, shoulder press, lat pulldown, bench press
The trends indicate that doing an exercise first in a session improved it more than doing it later.
They conclude that:
“if an exercise is important for the training goals of a program, then it should be placed at the beginning of the training session, whether or not it is a large or a small muscle group exercise” - Dias et al 2010
How exercise order affects hypertrophy
In respect to more advanced, hypertrophy based athletes - one method that has been used in bodybuilding circles is pre-exhaustion techniques. Basically, you complete a set of isolation exercises prior to compound exercises. For example, leg extensions before squats. This idea is based on the hypothesis that a point of failure in a compound exercise occurs when the weakest muscles are no longer able to apply enough force (Jones 1970).
Gentil et al, (2007) compared two trained groups using a pre-exhaustion (pec dec then chest press) or priority system (chest press then pec dec). Subjects completed more reps in the first exercise, but ultimately the volume was not different between groups. They also measured EMG from the triceps, delts and pec major during both exercises and found no differences in pec activation between groups.
Table 1 from Gentil et al, 2007
The issue here is acute studies may not predict long-term gains, especially EMG studies (Vigotsky et al., 2015; Enoka et al., 2015). In studies that look at the short-term and the long-term gains, it appears that pre-exhaustion may not matter (Gentil et al, 2007; Simão et al., 2012; Fisher et al, 2014). One study compared hypertrophy between two groups with equated volume: a pre-exhaustion group and normal exercise order group. The normal exercise group trained large to small muscle groups. There were no differences between groups in terms of muscle mass and strength after 12 weeks of training (Fisher et al, 2014).
“...strength gains are not influenced by the use of [pre-exhaustion], exercise order, or between-exercise rest intervals. “ - Fisher et al, 2014
Based on the current literature, it might be a good idea to order exercises based on how important they are to you and what your strengths/weaknesses are. The most important exercise(s) should be done first in the session (Sforzo et al., 1996; Spreuwenberg et al., 2006; Gentil et al, 2007; Dias et al., 2010; Simão et al., 2012). Larger muscle groups don’t have to be exercised before smaller ones (for example, you might want to train small, lagging muscle groups first in the workout) (Simão et al., 2012). For hypertrophy and strength, several studies show a trend where lifters get better gains for exercises that are done early in a session (Simão et al., 2012, Dias et al 2010), but a recent study disagrees (Fisher et al, 2014).
Training to failure
Most studies and reviews find that failure is either superior to, or equal to non-failure training for hypertrophy and strength gains. No study or review found that failure was worse than non-failure training. Failure might be more important the lower the intensity (Mitchell et al., 2012; Ogasawara et al., 2013; Nóbrega and Libardi, 2016; Gieβsing et al., 2016) and it might be more important to go to failure if you’re trained (Nóbrega and Libardi, 2016). Beginners seem to be able to gain strength and hypertrophy pretty well when they’re doing unilateral training, regardless of whether they go to failure or not (Nóbrega and Libardi, 2016; Nóbrega et al., 2017). Though many of the studies are not ecologically valid.
Mitchell et al., 2012 - Similar hypertrophy between high-load and low-load when sets are taken to failure
“training to failure should not be performed repeatedly over long periods, due to the high potential for overtraining and overuse injuries” (Willardson, 2007)
In addition, failure also makes the workout feel more difficult (Sampson and Groeller, 2015) and it might slow recovery and possibly lead to overreaching (Helms et al., 2014; Davies et al., 2015; González-Badillo et al., 2016; Nóbrega and Libardi, 2016). Exertion (RPE) and physical discomfort is higher when training to failure (Davies et al., 2015; Fisher et al., 2016). If a program contains a lot of failure sets, it will be more taxing physiologically, and psychologically. This could affect program adherence (i.e. you’re more likely to drop out if it’s very difficult and unrewarding) (Wienke and Jekauc, 2016).
Going to failure early on the first set cuts down on the amount of reps you can do in subsequent sets (Senna et al., 2011; Davies et al., 2015; Fink et al., 2016; González-Badillo et al., 2016; Jenkins et al., 2016). Hence, excessive training to failure could lower the total volume you’re able to do per session, and it could mess with your program if it has a specified set/rep scheme (for example 5x5, 4x8, etc.).
Figure by Senna et al., 2011 where 15 trained men were doing bench press for 5 sets. It shows that going to failure on every set leads to drastically less reps on the last set vs. the first set (10RM to 6-7RM) when taking 3-5 minute breaks between sets. The result is even more drastic with 1 minute rests.
If you want to go to failure, it might be better to do so on the last set(s) rather than the first sets of an exercise. Some programs use AMRAP sets (where you do “As Many Reps As Possible”) on the last set. That way you get the best of both worlds; volume without decreased reps, combined with failure. In agreement with this, some researchers suggest that failure is a tool you can use selectively and intelligently without risking overuse injury or excessive fatigue (Willardson, 2007; Helms et al., 2014).
Overview of failure studies
This is the studies we reviewed for failure. The table encompasses as many failure studies we could find, but we might have missed some studies. Low quality studies (i.e. Folland et al., 2002), and studies that didn’t test dynamic 1RM strength nor hypertrophy (i.e. Fisher et al., 2016) are omitted from the table. Older studies that have been covered in Willardson (2007) are not included (i.e. Izquierdo et al., 2006). and Sampson and Groeller, 2015 included in Davies et al., 2015 (in regards to strength, but not hypertrophy).
Limitations: Does failure research apply to you?
Isolation machine exercise
Most failure studies use unilateral single-joint (isolation) machine exercises for one muscle group during the entire study. And in many studies they would take every set to failure. This might work if you’re only exercising one body part in isolation, because it’s not too fatiguing. It is possible the results would be different with a whole-body program where every exercise and every set was taken to failure. Most likely, a program like that would be overwhelmingly difficult not only physically but psychologically, as some studies show. In other words, very few studies were practical or realistic (“ecological validity”)
Many studies didn’t match volume between groups (i.e. one group would do more volume, in addition to going to failure (or not going to failure)).
The short duration of most the studies (6-12 weeks) can’t tell us whether failure is an optimal strategy in the long-term. It’s likely that constant use of failure leads to overreaching, and later overtraining.
There’s a lot of disagreement and heterogeneity in the literature. I.e. many of the studies are dissimilar.
Most, if not all of the studies, used convenience sampling. Almost all participants were 23 year old untrained university males. This isn’t good in terms of representativeness. It’s possible people of different ages and genders would experience different effects. For example, older people might be at greater risk of injury, hence they might want to train with lower intensities and not go to failure because failure increases injury risk.
Rest duration between sets
Rest intervals are interesting when it comes to strength and hypertrophy training. In general, many research groups suggest that longer rest intervals allow you to accumulate more volume because you can complete more reps per set (Willardson and Burkett 2006; Miranda et al., 2007; Senna et al., 2009; Senna et al., 2011; Filho et al., 2012; Henselmans and Schoenfeld, 2014; Schoenfeld 2016a, Fink 2016a). On the other hand, shorter rest periods (i.e. 1 minute rest between sets), means that you can do more sets in the same amount of time.
A good example of this is a study that looked at how different rest durations affected bench press, machine fly, leg press, and leg extension in trained men (Senna et al., 2011):
“Shorter rest intervals resulted in greater reductions in the number of repetitions completed and higher RPE scores for all exercises”
Figure by Senna et al., 2011
If you use shorter rest intervals you may need more sets to hit your target volume for each workout. Plus, you may need to adjust the weight because each set will become progressively harder to do (increased RPE). This also means that short rests could lead you to take many sets to failure. As we have discussed above, excessive failure is not ideal.
How rest duration affects hypertrophy
The recommendation to use short rests for hypertrophy was originally taken from research that looked at acute anabolic hormones (Kraemer 1990, McCall 1999). With short rests, we would see these hormones spike to a greater extent after exercise, compared to long-rest. Hypothetically, this leads to more gains. However, this have been called into question by many (Henselmans and Schoenfeld 2014, Morton 2016, McKendry 2016). Though, others still support the theory (Mangine 2017). It’s a big debate between two camps. The hormone research has previously been analyzed here on SCI-FIT in an article called “Is post-exercise hormone secretion linked to gains?”.
Until recently, most studies found the minimum rest interval for hypertrophy should be at least 2 minutes (Buresh 2009, Ahtiainen 2006, Schoenfeld 2016). Then, Fink et al., published a study to show there was an increase in muscle thickness for an untrained group of men who used 30s rest (Effect size = 3.17) vs those who used 3min rests (ES = 0.42). Both groups trained to failure and significantly increased muscle CSA (9.3% for short rests, 4.7% for long rests) only having differences in volume for the BB curl which could explain the hypertrophy differences since the bicep was used to measure CSA.
Figure by Fink et al 2016
In another study by Fink et al., 2016b., on relatively untrained subjects, there was no difference in muscle CSA when comparing short rest (30s) to long rest (150s). We say relatively because the criteria was no resistance training in the past two years. Volume was matched and the study lasted 8 weeks but participants only trained with 4 sets of squat and bench press, two times per week. It appears from the literature there may be a discrepancy in hypertrophy for trained vs untrained. Untrained subjects may be able to get the same hypertrophy with shorter rests (~30s) (Fink et al., 2016a, Fink et al., 2016b). Yet, longer rest intervals may be more important in trained subjects (Buresh 2009, Ahtiainen et al., 2006, Schoenfeld et al., 2016). This leads back to the idea that you can do almost anything to an untrained subject to get muscle and strength gains.
There is even some data to suggest that reducing rest intervals from 2min to 30s over 8 weeks causes the same response as 2min rest periods (De Souza 2010). The short rest group did less volume, as a result of the reduction in time, yet there were no differences in muscle strength or size in between groups (De Souza 2010). These were in recreationally trained males.
However, others disagree:
“the literature as a whole suggests that rest interval manipulation has minor effects on muscle hypertrophy compared with other training parameters such as work volume, which suffers when inter-set rest is insufﬁcient even in trainees accustomed to this type of training [6,12,13] (...) the literature does not support the theory that training for maximum muscle hypertrophy requires shorter rest intervals than training for strength” (Henselmans and Schoenfeld, 2014)
Their conclusion is supported by others, see our table below for more details.
How rest duration affects strength
In regards to strength - longer rest periods may allow you to train at a higher intensity (Willardson 2005; Willardson, 2006). Furthermore, resting 3-5 minutes between sets produced greater increases in absolute strength, likely due to the higher intensity of exercises (De Salles 2009). One study found that a long rest (2.5 minutes) resulted in an ~50% increase in 5RM BP compared to a short rest (1 minute) (Buresh 2009).
Another study found no significant difference in strength gains between 2 minutes and 4 minutes, but the 4 minute group had trends to gain more strength (ES = 2.96 vs ES = 1.96) (Ahtiainen 2006).
Both of these figures are from Ahtiainen et al. 2006. Which concluded with:
“The present study also shows that long-term training adaptations in muscle strength and mass did not differ between the 2 hypertrophic strength-training protocols examined in the group of young men with a background in strength training.” - Ahtiainen et al. 2006
Another study shows college football players who rested for 3min had a 7% increase in squat compared to those who only rested 30 seconds. Although the 3 minute group was able to use higher training intensities (Robinson et al., 1995).
Most of the literature suggests that longer rest periods are better if you want to gain strength (Lesinski et al., 2016, Buresh 2009, Willardson and Burkett 2008, Robinson et al. 1995, Schoenfeld et al., 2016a) . For older men it may be beneficial to train with shorter rest intervals (Villanueva et al., 2015; Borde et al., 2015).
Limitation: these studies have only tested rests in the range of 30-300 seconds, so we don’t know if there are any benefits to waiting >5 minutes between sets. It makes sense to use longer rests when doing high-intensity compound exercises to failure (Willardson, 2006). One study even found it takes longer to recover from a complex movement (bench press) vs a machine based movement for consistent rep performance (Senna et al 2015). Is it possible to do deadlift 5RMs to failure, rest for 2 minutes and then keep going at the same intensity and rep-range? In practice, you should use rest durations that allow you to do the sets and reps at the intensity you have planned (Willardson, 2006).
Here’s a summary by Willardson, 2006:
“the length of the rest interval between sets is only 1 component of a resistance exercise program directed toward different training goals. Prescribing the appropriate rest interval does not ensure a desired outcome if other components such as intensity and volume are not prescribed appropriately. (...) strength coaches should consider individual differences and the type of workout being performed when prescribing the rest interval between sets.”
Overview of rest duration studies
Range of motion (ROM)
Some clarifications before we start this section: there is a difference between physiological ROM and exercise-specific ROM. Physiological ROM refers to how much a muscle can stretch and contract, and it’s limited by factors such as anatomy and general mobility (i.e. muscle tightness). Exercise-specific ROM is how much a muscle contracts and stretches in a given exercise. For example, you can move through the full ROM for the barbell bench press without going through the full ROM for your shoulder joint, elbow joint, and pectoral muscle. This is because your chest and the bar limit the physiological ROM. An example of an exercise that has longer total ROM for your pectoral is the dumbbell bench press. For the purposes of this article, “train through full ROM” refers to exercise-specific ROM.
Picture by Muscularstrength.com - The DB bench press ROM is not limited by the bar (however, even this exercise does not take the pectoral through the full physiological ROM)
Picture by T-nation.com - Here, the BB bench press ROM is limited by the bar
A question that most of us would ask is, why would we not want to use a full range of motion? Generally, not using a full ROM is seen as bad - like the person who stops an inch short of the chest on the bench press. However there are certain circumstances when partial range of motion can be useful.
A good place to start is to look at training level (beginner vs. intermediate vs. advanced) as those who are intermediate or novice benefit from full range of motion in both strength and hypertrophy (Pinto et al., 2012).
Illustration from Pinto et al. 2012 demonstrating exercise-specific ROM
One study used the bicep curl (aka elbow flexion) to test forty young men with no resistance training experience (Pinto et al. 2012). As seen in the illustration from Pinto, one group completed a full ROM while the other only did a partial ROM. They did 2 days per week training for 10 weeks.
The study found significant improvements in muscle thickness for both partial and full ROM compared to control, with full ROM having a ~2% hypertrophy advantage over partial ROM. The effect size for the changes in strength was 1.89 (moderate/large) for full ROM and 0.87 for partial ROM. So in this reductionist style experiment, the full ROM wins.
Table 1 from Pinto 2012 (edited for clarity)
Another group of researchers, using untrained subjects, had women complete a partial, full, or mixed ROM over a 10 week training period. They found each of the groups had an increase in bench-press strength from pre- to posttest. In addition, a statistically significant difference was found between the full ROM group and the partial and mixed groups showing an advantage for the full ROM (Massey et al., 2005). Yet, this group had previously found, using untrained men with the same protocol, that there was no difference between partial ROM and full ROM on strength (Massey et al., 2004).
In a unique lumbar extension study, subjects completed 0 - 36 (A), 36-72 (B) or 72 (AB) degrees of movement 1x per week for 12 weeks. Not ideal, but somewhat relevant to understanding ROM. The results show that all groups increase lumbar strength, which indicates that a carryover of strength occurred into the untrained ROM (Graves et al., 1992).
This same group showed a carryover of partial ROM to full ROM strength gains in knee extension (Graves et al 1989). So, maybe, there is a benefit to doing partial ROM if you have a specific reason to do it (i.e injury). Basically, strength is very specific (Roig et al., 2009; Hedayatpour and Falla, 2015). Some data from these studies show that there is a ~20 degree range which you can improve strength within a set range of motion (Graves et al., 1989, Bloomquist et al., 2013).
One study found that there was a two-fold increase in muscle size after only 8 weeks of full ROM squats compared to partial squats (McMahon et al., 2014) in relatively untrained subjects. An interesting note from this study and others, is that a muscle can grow at specific regions (Antonio, 2000; Wakahara et al., 2012; Wakahara et al., 2013; McMahon et al., 2014). The hypertrophy at 75% of femur length was 3-times greater in the longer ROM vs shorter ROM. Another study, using somewhat trained lifters, found that after 12 weeks of heavy load squat training there were increases in 1RM strength. This study compared a shallow squat vs a deep squat. However, only the deep squat increased muscle mass in the legs and front thigh muscle size. The shallow squat gained muscle only at the most proximal sites measured (Bloomquist et al., 2013).
Figure 2 from Bloomquist et al. 2013
The studies above used mostly untrained subjects and we know they respond to a wide variety of training. I think we can speculate full ROM is more beneficial in new trainees for both strength and hypertrophy although partial ROM may be sufficient to induce strength and size. Plus, full ROM may help reduce risk of injury later (imbalances). Unless the person is having difficulty learning technique and you need to break it down into a sequence then put it back together into one fluid motion.
Maybe partial ROM is more helpful in experienced lifters? Let’s take a look.
Clark et al., 2011 used semi-professional rugby players to determine if variable ROM or standard ROM was better at increasing bench press over 12 weeks. Variable range of motion used ½, ¼, or a full bench press throw.
Figure 2 from Clark et al., 2011
“The inclusion of a VROM resistance training microcycle into an athlete’s training program provides superior reactive strength and dynamic force improvements in comparison with performing strictly full ROM training. This method of training appears to be a beneficial component in an athlete’s attempt to achieve optimal sporting performance while reducing their risk of injury. However, the heavy loads used in this method of training indicate that it may be appropriate for preseason strength enhancement training microcycles, and that it should be restricted to athletes with sufficient resistance training backgrounds.” - Clark et al., 2011
As your training age increases it may be necessary to use partial ROM to help overcome sticking points in certain exercises (Mookerjee and Ratamess, 1999; Kompf and Arandjelović, 2016). This is best done by adding partial ROM lifts into a program containing full ROM exercises (Bazyler et al 2013; Clark et al., 2011). It’s also possible to include partial ROM training as a part of a training block for trained or elite lifters (Mookerjee and Ratamess, 1999; Bazyler et al 2013). Working with a partial ROM when you're injured might also a good idea (Fisher et al., 2013). Ultimately, whether you are a novice or intermediate lifter, you should primarily train through a full range of motion.
Some interesting factoids:
- It appears that most people are strongest 2-5 inches from the completion of a repetition in the bench press (Massey et al., 2005).
- Full ROM seems to induce greater muscle damage than partial ROM even if more volume is lifted in the partial ROM (Baroni et al., 2016).
- “the use of full ROM may lead to less psychological and bone joint stress, because full ROM uses a lesser load for the same number of repetitions than partial ROM does” - Pinto et al., 2012
Overview of ROM studies
What you do in the gym leads to specific improvements. Strength is highly specific to the exercise, contraction type (eccentric vs. concentric), intensity, rep range, movement speed, range of motion, etc. that you train (Morrissey et al. 1995; Kraemer and Ratamess, 2004; Roig et al., 2009; Schoenfeld et al., 2014; Hedayatpour and Falla, 2015; Beardsley, 2015; Pritchard et al., 2016; Rhea et al., 2016). There is carry-over between exercises, but training should be more specific the better the athlete is:
Model by Kraemer and Ratamess (2004)
In addition to specificity, people respond differently to the same training programs. This means that two different people could make vastly different gains with identical time and energy investment.
Some researchers believe this is due to genetics and epigenetics which are affected by lifestyle factors (i.e. diet, sleep, life stressors, etc.) (Simoneau and Bouchard, 1995; Mead, 2007; Bamman et al., 2007; Liu et al., 2009; Erskine et al., 2010; Puthucheary et al., 2011; Hughes et al., 2011; Ahmetov et al., 2012; Thalacker-Mercer et al., 2013; Guth and Roth, 2013; Kim et al., 2014; Mann et al., 2014; Schutte et al., 2016; Zarębska et al., 2016; Ahtiainen et al., 2016; Klimentidis et al., 2016; Broos et al., 2016; Gineviciene et al., 2016; Heffernan et al., 2016).
We usually divide people into low-responders and high-responders (Hubal et al., 2005; Davidsen et al., 2011; Mann et al., 2014; Parr et al., 2016; Ogasawara et al., 2016; Bonafiglia et al., 2016; Buckner et al., 2017).
Figure by Angleri et al. (2017) (edited for clarity) shows us how different people gain strength and muscle mass. Every bar is a person.
Furthermore, it’s possible that some people respond better to certain types of diets or training programs (Kikuchi and Nakazato, 2015; Parr et al., 2016; Jones et al., 2016; Bonafiglia et al., 2016). For example, you might be a high-responder to low volume high intensity training, but a low-responder to high volume low intensity training. This is something we need to account for when designing training programs, and it’s very easy to misinterpret study results as something that has to apply to everyone.
What are the practical implications of specificity?
Specificity dictates that you get good at the specific exercises you do, which also depends on how much time you dedicate to doing them. Specificity applies to the rep-range, intensity, range of motion, volume, exercise, etc. that you choose to use. So if you want to be really strong at squats, do squats and variations of squats. If you want to be really good at doing biceps curls, do a lot of biceps curls with variations.
Individual variability indicates that people might need different programs to get the “same” gains. In other words, there is no cookie cutter program that will be ideal for everyone. However, this doesn’t imply that all programs are equally good. What we’re getting at is that even if we give you recommendations based on research, these recommendations are based on averages, and might not be ideal for you and your goals.
"The long-term effects of periodized resistance training programmes on strength and power seem to follow the law of diminishing returns, as training exposure increases beyond 12-24 months, adaptation rates are reduced" (McMaster et al., 2013)
How to implement this knowledge into your programming
- You can use the information presented here in a myriad of ways. You can make your own program (not advisable for beginners), you can choose a program that adheres to these principles, or you can modify a program you’re already on. The guidelines in the table are not a program, they’re more like building blocks you can use to make a program.
- The most important consideration when choosing or building a program is the goal: what does this program accomplish, specifically? As most know, a powerlifting program will be vastly different to a hypertrophy program. The PL program will focus to a great extent on the three main movements, while a hypertrophy program does not have to contain squatting, deadlifting, or barbell benching, given that muscle groups can be adequately stimulated by other exercises. However, using these three exercises is a very time-efficient way to exercise multiple muscle groups at a time.
- Most decent programs will already use most of these recommendations. Though some programs might suggest very high training frequencies (squat every day) or volumes (50 working sets per muscle group per week). This advice is yet to be supported in the literature. In fact, excessive exercise could lead to overtraining or injury. Though, highly trained individuals might be able to sustain this type of programming, especially if intelligent deloads are added to avoid overuse and burnout.
- Do what you can (adherence). Let’s say you train 2x per week doing a whole-body workout with 5 working sets per muscle group per session. Every session is going to take quite some time, as you can imagine. It might be more practical to divide the sessions into 3 or 4 days per week. Now, many people don’t have the time to do this. If you can’t, just do your best. Try to get a couple of working sets in, and hit the major muscle groups at least once per week. This isn’t optimal, but for many people with jobs and kids it’s reality. It’s much better to consistently hit one or two days a week rather than trying to do an inconsistent 4-day split.
- More volume/frequency/failure/intensity isn’t necessarily better (Fry et al., 1994; Zourdos et al., 2015; Murach and Bagley, 2015; Schoenfeld et al., 2016; Amirthalingam et al., 2017)
- We will do a review on periodization studies in the future
The limitations of fitness research
- Poor study methodology
- And more
If you like limitations, you can read more about them in this article on SCI-FIT