Volume tolerance of individual muscles

Can large muscles handle more sets than small ones? The only study to compare four muscle groups in the same individuals found the opposite: the largest muscle was the most resilient. What really determines resilience, and why there is no research to support the usual volume guidelines.

Auch bekannt als: Volumentoleranz, Muskelspezifisches Volumen

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What it’s all about

Training plans allocate volume according to a rule of thumb: large muscles can handle a lot, small ones a little. The chest and back get fifteen sets per week, the biceps six. The reasoning behind this is that a muscle’s capacity for training depends on its mass, and that a large muscle consequently takes longer to recover to a trainable state.

Neither of these has ever been tested. What has been tested points in a different direction: muscles do in fact differ significantly in how much a load affects them. However, the factor on which they differ is not size, and in some respects it runs completely counter to the rule of thumb.

Where a difference might arise

Fibre distribution

Muscles consist of varying proportions of slow-twitch and fast-twitch fibres, see Muscle fibre types. An autopsy study mapped the distribution in 36 human muscles, thereby providing the data on which the current view that a particular muscle is inherently endurance-oriented is based.

For the abdominal muscles, the standard example used in this line of argument, biopsy data are available. In samples taken from four layers of the abdominal wall of 13 individuals, the proportion of type I fibres averaged between 55 and 58 per cent, and there was hardly any difference between the four abdominal muscles. What was remarkable was something else: the variation between individuals was large, whilst that between muscles was small.

A high proportion of fatigue-resistant fibres explains why a muscle can sustain continuous exertion for longer. The idea that it can therefore tolerate more training sets or recover more quickly is an extrapolation from endurance performance to recovery. This extrapolation is plausible, but it has not been measured. This is where the argument based on fibre distribution ends.

Everyday use

The second explanation is more straightforward and is supported by more data. A muscle that performs braking work every day is accustomed to such work. The knee extensors absorb the body’s weight every time you go down the stairs, several hundred times a day. The elbow flexor does nothing comparable.

Fitness level

Protection against injury is not an inherent property of a muscle, but can be acquired. A review of 20 studies on multi-joint exercises found that, following a single prior exercise session, the second session resulted in lower muscle soreness and lower creatine kinase (standardised mean differences 0.51 to 1.23) and less loss of strength. This repeated-exercise effect occurred regardless of whether the intensity and volume were altered between the two sessions.

It follows that there is a limitation for all further considerations: injury data from untrained individuals do not describe what happens to a trained person. They describe the unprotected state.

What the studies show

The most direct study on this issue compared four muscle groups in the same individuals. Seventeen untrained men each performed five sets of six maximal eccentric contractions for elbow flexors, elbow extensors, knee flexors and knee extensors, with each group worked on a different limb and with an interval of four to five weeks between sessions. Over a period of five days, strength, optimal joint angle, circumference, range of motion, creatine kinase, myoglobin, muscle soreness and echo intensity on ultrasound were monitored.

The ranking was clear. Both arm muscles showed, across all measured parameters, significantly greater changes than both leg muscles, with no difference between the flexors and extensors of the arm. Among the leg muscles, the knee flexors were affected more than the knee extensors. In the case of the knee extensors, the optimal angle, circumference and echo intensity did not change at all. The authors attribute this to the differences in everyday usage.

This turns the rule of thumb on its head. The quadriceps is the largest muscle in this comparison and proved to be the most resilient, whilst the elbow flexors were among the smallest and most sensitive. Anyone who distributes volume according to muscle size is distributing it along an axis that played no part in this measurement.

As far as volume itself is concerned, the data is sound, though it is not broken down by muscle group. A meta-regression across 34 treatment groups from 15 studies found a graded relationship: each additional set per week corresponded to an effect size of 0.023, equivalent to 0.37 per cent more growth. The more recent and significantly larger meta-analysis of 67 studies involving 2,058 participants confirms this trend with 100 per cent probability, but finds a diminishing marginal utility in the best-fitting models. Both studies report average values across all the muscles examined; neither study provides a breakdown by muscle.

As regards frequency, the findings are even clearer. A meta-analysis of 25 studies found no significant difference between high and low frequency when the weekly volume was the same, and this finding of no significant difference remained when the upper and lower body were analysed separately. The meta-regression of 67 studies reaches the same conclusion regarding hypertrophy, whilst for strength, it shows a clear advantage of higher frequency.

The separate analysis of the upper and lower body is the key point here: it is the only direct test of whether different body regions react differently to frequency, and the result was negative . A null finding, where moderators were investigated, is more robust than a mere mean value.

One finding shifts the focus from the muscle to the individual. In a study involving 21 beginners, one arm and one leg were trained three times a week for ten weeks, whilst the opposite side was trained twice a week, each time to muscle failure at 60 per cent of the one-repetition maximum. The participants had been classified in advance into slow and fast types based on carnosine measurements in the muscle. The variation in the results was considerable (muscle volume +3 to +14 per cent, strength +17 to +47 per cent), but could not be attributed to the type classification. However, participants classified as slow-twitch did have to undergo a significantly higher training volume in order to achieve the same adaptation.

A search in PubMed for muscle-specific volume guidelines and for terms such as ‘maximum recoverable volume’ yields no results. The figures used in training plans – namely five to ten sets per week for the biceps and fifteen to twenty for the back – are derived from practical experience rather than from research. They are not, therefore, incorrect, but they are based on experience, and they are regularly cited as if they were measured values.

What this means for planning

Size is the wrong sorting criterion. In the only study that compared four muscle groups in the same individuals, the largest muscle was the most resilient. Anyone who distributes volume according to mass is not following any measured quantity.
The best approach is to stick to your usual workload. What constantly acts as a hindrance in everyday life is more easily overcome in a single session. This applies to the knee extensors, calves and core, but not to the biceps.
First volume, then frequency. Given the same weekly volume, the frequency does not make a significant difference to hypertrophy. A higher frequency is still useful, but as a means of spreading the weekly volume across the week, not as a stimulus in its own right.
That does not apply to Kraft. There, revenue increases with frequency, whilst marginal utility also decreases. If you want both, plan around the more limited of the two objectives; see Periodisation.
More volume makes an impact, but the effect is becoming weaker and weaker. The increase per additional weekly set is in the region of tenths of a per cent, and the more detailed analysis shows that the curve is levelling off. The point at which it is no longer worth having another child is a question of cost, not a biological limit.
The person moves more than the muscle. In the case of the abdominal muscles, the variation between individuals was greater than that between the muscles, and with the same training stimulus, the range of improvements was between 3 and 14 per cent. A plan that records one’s own reaction is better than any table.
Do not transfer untrained values to trained ones. Even a single previous session significantly reduces damage and loss of strength. The damage ranking for beginners describes the unprotected state, see Delayed onset muscle soreness (DOMS).

Classification

The question of whether individual muscles can tolerate different levels of volume has two answers, and both are inconvenient. Yes, they do differ, and significantly so: when it comes to damage caused by an identical protocol, the difference between elbow flexors and knee extensors is the difference between a clear reaction in every measured parameter and none at all in three of them. No, this difference is not down to muscle size, but rather to what the muscle actually does in everyday life.

What this implies for the recovery period is a conclusion, not a finding. More severe damage is associated with a longer loss of strength, and a muscle that is unable to generate as much tension will receive less stimulation the next time; see Muscle fatigue. The chain is plausible and its links are substantiated. There is no study that has measured muscle-specific recovery times on this basis.

If the chain effect holds true, it should become apparent in a simple experiment: the same weekly volume, the same frequency, two muscles with known differences in susceptibility to damage, and then the question of whether the more sensitive muscle grows less well when the workload is distributed identically. So far, damage has been measured and adaptation separately; never both in the same setup.

In practice, this involves reversing the usual order. It is not the muscle that determines the volume; rather, the weekly volume is spread across so many sets that none of them enters the range where further sets would only cause damage; see Training splits and Hypertrophy training. Whether a battle requires two or three units is determined by the damage inflicted on each individual unit, not by a table listing unit names.

Sources

Chen TC et al. Comparison in eccentric exercise-induced muscle damage among four limb muscles. Eur J Appl Physiol. 2011. PubMed
Johnson MA et al. Data on the distribution of fibre types in thirty-six human muscles. An autopsy study. J Neurol Sci. 1973. PubMed
Häggmark T, Thorstensson A. Fibre types in human abdominal muscles. Acta Physiol Scand. 1979. PubMed
Van Vossel K et al. Can muscle typology explain the inter-individual variability in resistance training adaptations? J Physiol. 2023. PubMed
Pelland JC et al. The Resistance Training Dose Response: Meta-Regressions Exploring the Effects of Weekly Volume and Frequency on Muscle Hypertrophy and Strength Gains. Sports Med. 2026. PubMed
Schoenfeld BJ et al. Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis. J Sports Sci. 2017. PubMed
Schoenfeld BJ et al. How many times per week should a muscle be trained to maximize muscle hypertrophy? A systematic review and meta-analysis of studies examining the effects of resistance training frequency. J Sports Sci. 2019. PubMed
Doma K et al. The Repeated Bout Effect of Multiarticular Exercises on Muscle Damage Markers and Physical Performances: A Systematic Review and Meta-Analyses. J Strength Cond Res. 2023. PubMed

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