As I’m sure you’re all aware, Monday is ‘International Chest Day’, Tuesday is ‘Leg Day’, Wednesday is ‘Back Day’ and so on. On each of these days we must perform a variety of exercises for multiple sets culminating in 30 sets per muscle group at the very least! This typical training split, commonly known as the ‘Bro Split’, is used by the majority of recreational lifters and has been advocated by magazines and supplement companies worldwide who report the training routines that their big name, often enhanced, sponsored athletes have used to get them to the top…along with their supplements of course. And if it’s worked for them it’ll work for you right?!
Although there is no doubt that non-enhanced individuals using this weekly, high volume, body part split can get into great shape, for the majority of us ‘hormonally challenged’ lifters this method may not result in optimal muscle or strength gain. For enhanced athletes, their increased concentrations of anabolic hormones allows for the utilisation of lower frequencies as muscle protein synthesis (MPS), hypertrophy, and muscle anabolism is increased for longer durations compared to ‘natural’ trainers. In mere mortals like you or I, the lower physiological levels of anabolic hormones results in a more rapid decrease in MPS after workouts, with increased MPS sustained for around 48-72 hours1,2.
Therefore, more frequent training for a particular muscle group may be required to maintain anabolic signalling.
It is also clear that the use of an increased number of repetitions and training volume has a greater hypertrophic effect in enhanced athletes. This may be due to the training volume threshold at which the onset of overtraining occurs, and at which any further volume does not increase the hypertrophic response, are significantly greater in enhanced individuals. Put simply, enhanced athletes can train harder, with a greater number of repetitions, for longer, with a greater number of sets, and see a greater return, in terms of hypertrophy, for their effort.
In the case of non-enhanced trainers, it is becoming increasingly accepted in natural bodybuilding circles, that progressive overload and greater frequency are key to stimulate MPS and maintain anabolic signalling, rather than increased volume. This article will examine the research behind the effects of training volume and frequency upon muscle gain, identifying the key parameters to help optimise your training.
Although it is likely that excessive volumes are not necessary to stimulate maximal hypertrophy in non-enhanced athletes, it has been reported in a number of studies, and it is now generally accepted, that high volume training stimulates greater MPS and anabolism than lower volumes3,4,5,6,7,8. This has been found to be due to neural, hypertrophic, metabolic and hormonal responses and adaptations to training9,10,11,12. It has also been proposed that it may be the time under tension aspect of increased volume, rather than the mechanical work output (force x distance), that is the most important parameter that determines the influence of increased volume on hypertrophy13.
The utilisation of higher volume training has also been found to induce greater lactate production as well as greater Growth Hormone levels compared to lower volume training14. However, these studies which investigated anabolic effect of different training volumes often only compared volumes ranging from 1 to 6 sets for a muscle group, with the majority of these studies identifying the peak hypertrophic effect at 3 sets and little further increase with greater volumes.
It must also be noted that differences may exist between trained and untrained individuals, and it has been identified that single or multiple set programmes have been found to be effective for untrained individuals, whereas multiple set programmes have been found to be superior for trained individuals15. It must also be recognised that, regardless of whether volume is standardised, differences in time under tension, force production and power output can exist within in a set due to differences in temporal, kinematic and kinetic characteristics16.
Despite recruiting untrained subjects whom are likely to respond favourably to a variety of training volumes, a paper by Paulsen and colleagues17 demonstrated that the anabolic effects of increased volume may not be as straightforward as they seem. By comparing two groups, one utilising training volumes of a single set for lower body and 3 sets for upper body and another utilising the opposite, the authors demonstrated that, as expected, the increase in one-rep max (1RM) for leg exercises was greater in the groups that had a training volume of 3 sets for lower body rather than a single set. However, they also observed that no difference in the increase 1RM for upper body exercises was observed between the single set and 3 set upper body training volume groups.
These findings may suggest that the larger muscle groups of the lower body may require greater training stimulus and volume to induce strength and muscle gains compared to the smaller muscle groups of the upper body, for which the training stimulus and volume required may be lower.
The literature also suggests that, in order to continually progress and stimulate hypertrophy, volume should gradually increase within a training programme7, a concept which aligns with that of progressive overload. This programme should culminate in a brief ‘overreaching’ phase which is followed by a ‘deloading’ phase. However, it must be stressed that prolonged overreaching can lead to ‘overtraining’, characterised by chronically decreased testosterone and increased cortisol, which has been found to be correlated with excessive volume rather than intensity18. This ‘overtraining’ phenomenon is known to have a catabolic effect upon muscle tissue. It should also be acknowledged that an inverse relationship exists between training volume and training intensity. Long workouts and high training volume have been associated with reduced intensity of effort, decreased motivation and alterations in immune response19, whereas increased intensity is known to require a reduced optimal training volume20.
However, multiple studies have contended the hypothesis that an increased training volume results in increased hypertrophy, with both Starkey and colleagues21 and Ostrowski and colleagues22demonstrating that lower volumes were as effective as higher volumes, up to 12 sets, at increasing strength and muscle size, although long-term utilisation of high volumes was found to be correlated with hormonal shifts associated with overtraining. However, the lack of any noticeable difference between volumes may have been due to the low frequency of training for each body part (once per week), and it may be that the additive effects and adaptation to training were not realised when long intervals between training sessions were present.
These findings suggest that training frequency may play an important role in hypertrophy, as will be discussed further in this article.
‘Split’ routines, rather than full body routines, allow for weekly training volume to be maintained with fewer sets per session and greater recovery between sessions. This allows for the utilisation of heavier training loads in each sessions and therefore increased muscular tension, metabolic stress and a prolonged training stimulus7. But how frequently should we train each body part?
Training frequency is known to depend upon volume, intensity, exercise selection, conditioning, training status, recovery ability, nutritional intake and training goals8. As you might expect, the majority of research regarding training frequency and muscular adaptation has demonstrated that a greater weekly training frequency for a muscle group results in greater muscle and strength gains, and frequencies of 2-4 times per week are often recommended6,8,13,15,23,24.
It has also been discovered that only a working single set was required to increase strength if training frequency was at least twice per week25. However, as mentioned previously, the recommended training frequency may vary depending upon training experience with frequencies of 2-3 times per week shown to be effective in novice lifters and 5-7 times per week shown to be optimal in elite weightlifters23. Although it is likely that untrained individuals adequately respond to low training frequencies, advanced trainers have been shown to respond most effectively to frequencies of 2-3 times per week with increases in muscle size twice that of when a training frequency of once per week was utilised26.
Training frequencies greater than 3 times per week were found to yield no further advantage, suggesting that rest intervals between workouts of 48-72 hours are required to allow for optimal hypertrophy which correlates with the duration of elevated rates of protein synthesis. However, studies have also shown that shorter rest intervals and higher frequencies can also induce strength increases27,28, which is likely to be due to increased frequency of muscle stimulation compensating for the necessary reduced muscular tension associated with training at higher frequencies.
Very high frequency training (12 times per week) has also been examined and this was found to increase muscle size to the greatest extent compared to lower frequencies29. However, studies exploring higher frequency training usually last between 2 and 4 weeks, and the long term effects of this training method are yet to be determined. It is unclear whether high frequencies continue to yield high rates of muscle gain or whether it results in diminishing returns or overtraining. However, increasing training frequency (up to 5 consecutive days per muscle group) for brief periods has been found to cause an initial decrease in strength followed by an increase over the next three weeks and the maintenance of this strength once frequency in reduced to normal levels8. These findings once again support the concept of brief periods of overreaching.
As with training volume, it has been identified that muscle groups of the upper body may respond differently to those of the lower body with regards to training frequency.
It has been found that the smaller muscle groups of the upper body respond more favourably to higher frequencies, of up to 5 days per week, compared to the larger muscle groups of the lower body (3-4 days per week)28,30. However, the findings in these studies are limited by the volumes for each training group not being equated.
A method of increasing training frequency involves splitting workouts into two sessions per day, which is often used in competitive strength athletes. Investigations into this method have discovered that when training is split into two sessions in a single day rather than one, and volume is equated, greater increases in muscle size and strength are observed31.
This strategy is often utilised by elite athletes and bodybuilders, allowing for a greater weekly training frequency per muscle group, however this strategy is not recommended for novice lifters- and is not feasible for most of us!
Examining the effect of detraining and reducing frequency has also yielded some interesting results. Graves and colleagues24 identified that a frequency of 3 times per week induced greater improvements in isometric strength compared to a frequency of twice per week. Additionally, this study demonstrated that reducing frequency from 3-2, 3-1 or 2-1 times per week did not significantly impact strength over 12 weeks. However, the cessation of training all together reduced strength by 68%.
This demonstrates that a frequency of 1 session per week can maintain strength, and that not training will be significantly detrimental to strength.
However, in contrast to the majority of the literature, a few studies have demonstrated that increasing frequency may not be beneficial to strength and hypertrophy. Carroll et al32 showed that no difference in increases in 1RM strength was observed between frequencies of 3 and 2 times per week, and Graves et al33 found that once per week training frequency provided as effective training stimulus as twice or three times per week.
Despite these few contradictory findings, it can be recommended that untrained individuals perform full body training splits 2-3 times per week, with frequencies of 3-4 times per week and 4-6 times per week being more effective for trained and advanced lifters respectively. These higher training frequencies in trained individuals will require the utilisation of alternative training programmes, such as an Upper/Lower or Legs/Push/Pull training splits, and individual body part training splits with multiple sessions per day may be most effective for elite athletes.
With regards training volume, although I would not recommend following the training volumes and protocols from the literature, as these are often designed for untrained individuals, it is likely that most lifters that currently utilise a ‘Bro Split’ would benefit from dividing their current weekly training volume into 2-3 sessions per week, allowing for an increased training frequency without reducing training volume.
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