Hypertrophy – Everything Science Currently Knows



It has been widely suggested that power output is one of the most fundamental characteristics underlying sporting success in anaerobic athletes (Lorenz et al., 2013); additionally, it has also been found to exist as a determinate factor which may distinguish elite Olympic Weightlifters from non-elite Olympic Weightlifters (Fry et al., 2006: Beckham et al., 2013). Since power output is such a key variable in determining sporting success, it has been targeted as an athletic characteristic which is necessary to develop in order to raise the athletic profile and individual success of Olympic Weightlifters (Flores et al., 2017) and anaerobic athletes (James et al., 2016). Since power is a work rate expressed as the equation Power = Force x Velocity, it is necessary to understand the two key components which are central to both the equation and the development of power. More specifically, velocity (expressed as change in displacement divided by change in time) is directly related to momentum, since momentum = mass x change in velocity. Moreover, force is directly related to impulse, since impulse = force x change in time. Put more simply, if an external load such as a barbell is to be moved powerfully by an athlete, the athlete must exert maximal force to the barbell in order to accelerate the barbell with the greatest momentum achievable, resulting in the barbell being moved from the floor to overhead as quickly as possible. Additionally, when the mass in question changes, for example, an increased weight on the barbell, but the impulse remains the same, the velocity of the lift will decrease. Since the ability to generate maximal force is limited by the time constraint of the sporting task, the need to rapidly develop force is essential; furthermore, with maximal strength representing the upper limit of the ability to produce force, an increase in maximal strength may increase the ability to generate higher forces through a spectrum of velocities. This concept points towards a pattern with which the rate of force development is the underpinning mechanism behind the expression of power in sport. If the goal is to increase the rate at which the barbell velocity changes, and both the mass of the weightlifter and the time period over which the force may be applied are not readily modifiable, the rate at which such force is created must be increased.

It is understood that force and velocity exist on a continuum known as the force-velocity curve, and located at the centre of this continuum is maximal power output. Since the shortening velocity of human muscle is limited, maximal force becomes increasingly important in order to provide a window during which greater increases in power can be achieved; as such, any desired improvements made to the force-velocity curve (and therefore impulse applied to the barbell), must derive from an increase in maximal strength. There are numerous physiological benefits which can be derived from strength training which have been shown to improve rate of force development, however, the focus of this article shall be directed towards the training methods for muscular hypertrophy, since an increase in strength has been shown to increase overall anatomical muscle size (cross-sectional area or volume), representing an effective means to increase RFD, since maximal contractile force capacity (and thereby RFD) is strongly governed by the macroscopic size of the muscle.



Traditionally, hypertrophy training consists of exercises using moderate loads and moderate to high repetitions utilised for multiple sets per exercise (Kraemer and Ratamess, 2004). Furthermore, with repetitions being classified into three basic ranges (low (1-5), moderate (6-12), and high (15+)) the extent of the hypertrophic response may be impacted by the use of different energy systems and subsequent taxation upon the neuromuscular system (Schoenfeld, 2010). There has been substantial debate surrounding the superior repetition range that will increase muscular hypertrophy to the greatest degree; however, the general consensus has centred upon an optimal range of 6-12 repetitions (Kraemer et al., 2002: American College of Sports Medicine, 2009). It has subsequently been theorized that repetition ranges of 15+ aren’t heavy enough to innervate the highest threshold motor units that control the fast twitch type 2B fibres, which possess the greatest potential for hypertrophic growth (Schoenfeld, 2000: Verdijk et al., 2009). More specifically, it has been shown in untrained men that both type 1, 2A and 2B muscle fibre types hypertrophied with low repetition range (3-5 repetitions maximum (RM) for four sets of each exercise with 3 minutes rest) and intermediate range (9-11 RM for three sets with 2 minutes rest), whereas a high repetition range (20-28 RM for two sets with 1 minute rest) causes no significant increases in muscular hypertrophy in any fibre type (Campos et al., 2002). Of interest is the occurrence of a fibre type transition shown by Campos et al., (2002); notably, for both the low, intermediate and high repetition range groups, the percentage of type 2B fibres decreased, with a concomitant increase in 2AB fibres and an associated decrease in MHCIIb accompanied by a significant increase in MHCIIa. This supports the concept that muscle fibres can exist on a continuum which may transform in response to the amount and type of training performed (Staron et al., 1983). In addition to the hypertrophic events shown by Campos et al., 2002, they also found that one repetition max (1RM) strength increased to the greatest degree in the low repetition group, whilst less significant improvements were also made in the intermediate and high repetition range groups.


Muscular hypertrophy has been further shown to increase when training intensity is manipulated; more specifically, Holm et al., 2008 compared low intensity (15.5% of 1RM), high volume (36 repetitions) leg extensions versus high intensity (70% of 1RM), low volume (8 repetitions). Following a 12 week training protocol which utilised leg extensions performed on a leg extension machine, a 2.6% (± 0.8%) increase was seen in quadriceps cross sectional area within the low intensity group, whereas an increase of 7.6% (± 1.4%) was seen in the high intensity group. Furthermore, 1RM strength increased by 19% (± 2%) in the low intensity group, whilst a 30% (± 5%) increase was seen in the high intensity group. In contrast, Barcelos et al., (2015) have shown that low-load resistance training until failure, utilised in young individuals with negligible training experience, is sufficient to induce significant improvements in quadriceps hypertrophy (3.6 % (CI 2.2–4.3)) and 1RM leg extension strength (22.3 % (CI 18.6–26.3)) following an 8 week leg extension protocol. It is interesting to note that the greatest hypertrophic effect from pre to post-intervention was in the 1×20% of 1RM to failure group when compared to the 3×20% of 1RM to failure, 1×50% of 1RM to failure and 3×50% of 1RM to failure training groups. On the contrary, the greatest strength increase was shown by Barcelos et al., (2015) to occur in the 3×50% of 1RM group when compared to all other training groups.

Moreover, in untrained, college age female subjects, quadriceps muscle cross-sectional area was shown to increase by Hisaeda et al., (1996) following an 8 week leg extension training protocol which utilised three training sessions per week and targeted traditional strength and hypertrophy training styles. More specifically, Hisaeda et al., (1996) demonstrated an increase of 3.6% (± 1.1%) in the strength group (8-9 sets of 4-6 RM with 90 seconds rest between sets) post intervention training cycle and an increase of 3.3% (± 0.7%) in the hypertrophy group (4-5 sets of 15-20 RM with ‘sufficient’ rest in between sets) post intervention training cycle. In agreement with this, Alegre et al., (2015) assessed quadriceps cross sectional area in University age females following a 10 week leg extension and single leg press training protocol; it was demonstrated that increases in both muscle size and strength occurred in both the intense and volume specific groups. As such, the intensity focussed group completed 3 sets of 8, 6 and 6 repetitions during week 1 to 3, whilst training intensity increased from 50% to 70% over this time period. During weeks 4 to 10, 3 sets of 6 repetitions at 80% of 1RM were performed in each exercise. In contrast, the volume group utilised a constant intensity (3 sets at 50% of 1RM); however, the number of repetitions performed within a session was continuously adjusted for each session from the second week onwards, in order to match the mechanical work performed by the intensity group. Interestingly, a deload, by way of a decrease in training frequency was utilised by Alegre et al., (2015) in both groups during weeks 4, 7, 9, and 10. Alegre et al., (2015) demonstrated an increase in quadriceps cross sectional area from baseline to post-intervention, with an increase of 4.6-12% in the intensity group and 3.1-11% in the volume group. Additionally, there was also a notable increase shown in strength measures, with the intensity group increasing their 1RM from baseline to post-intervention by 10-16% and the volume group by 10-14%. These results are also echoed by Mangine et al., (2015) who found a significant increase in both upper and lower body mass and strength when comparing an intensity focussed training cycle against a volume focussed training cycle. Lean arm mass increased from pre to post-cycle by 5.2% (± 2.9%) in the intensity group, whilst the volume group increased by 2.2% (± 5.6%). Furthermore, lean leg mass increased by 46.7% from pre to post-intervention in the intensity group, whilst the volume group increased by 21.4%. A concomitant improvement was gained in 1RM strength by both the intensity and volume groups following the training intervention; however, the intensity group obtained the greatest strength gains on 1RM bench press, whilst both the intensity and volume group gained the same improvements on 1RM squat.

In contrast, however, Burd et al., (2010) found low-load, high volume (volume dominant) resistance exercise to be equally effective at increasing acute muscle protein synthesis as high-load, low volume (intensity dominant) resistance exercise is at 4-hours post exercise; however, protein synthesis was elevated to a greater extent at 24-hours post-exercise in the low-load, high volume group. This is integral, since resistance exercise stimulates the synthesis of skeletal muscle proteins, which is ultimately expressed as muscular hypertrophy (Burd et al., 2010: West et al., 2010). Despite this, further investigation by Mitchell et al., (2012) has shown high-load, low volume training (80% of 1RM x 1 or 3 sets) to produce similar protein synthesis rates to low-load, high volume training (30% of 1RM x 3 sets), alongside the occurrence of greater increases in strength gained by the high-load, low volume group when compared to the low-load, high volume group. Crucially, however, is the occurrence of no statistically significant difference shown by Mitchell et al., (2012) in the degree of quadriceps hypertrophy between the 80%x1 and 80%x3 conditions, despite a mean gain in total quadriceps volume of 7% in the 80%x3 condition and 3% in the 80%x1 condition. Additionally, it was shown by Mitchell et al., (2012) that the 80%x3 and 30%x3 conditions demonstrated more than double the average hypertrophy of the 80%x1 condition, suggesting that a manipulation of both volume and intensity can induce hypertrophic changes when training is intensity or volume focussed.


Research investigating parallel areas of interest has shown that volume-load (the total amount of kg lifted per session) is independently associated with hypertrophy, but only among females (Peterson et al., 2011); in males, baseline strength is independently and inversely related to changes in total muscle mass (Peterson et al., 2011), whilst volume-load itself is heavily correlated to changes in 1RM for both males and females, (whilst controlling for age, body mass, and baseline strength) (Peterson et al., 2011). Aside from the total volume-load lifted per session, both the duration of the movement, the speed of the movement and the type of contraction will also contribute to changes in muscular hypertrophy when both intensity and volume is considered. For example, greater increases in muscular hypertrophy were found by Farthing and Chilibeck (2003) during fast (180°/s) eccentric contractions as opposed to slow (30°/s) eccentric contractions, fast (180°/s) concentric contractions or slow (30°/s) concentric contractions. However, caution is needed when interpreting these results, since Farthing and Chilibeck (2003) did not equalize the total volume-load for each group. More specifically, since the protocol utilised by Farthing and Chilibeck (2003) called for two to six sets of eight maximal repetitions per training session for both the eccentric and concentric training groups, it is supposed that the eccentric group produced a created amount of volitional force, time under torque, total reps and ultimately a greater amount of total muscular load, since maximal eccentric strength is approximately 20-60% greater than maximal concentric strength (Bammam et al., 2001: Hollander et al., 2007). When sets and reps are equated between eccentric and concentric exercises, it can be further seen that higher loads are developed during eccentric contractions, and both Roig et al., (2009) and Schoenfeld et al., (2017) attribute this to the significantly greater ability of eccentric exercise to develop total muscle cross sectional area and maximal strength ability when compared to concentric exercise. With this in mind, it is also fascinating to note that in untrained individuals, 9 sets of maximal eccentric muscle actions is superior to 12 sets of concentric muscle actions in increasing lean muscle mass (Wernbom et al., 2007). With regards to the duration of each repetition, Schoenfeld et al., (2015) suggest that hypertrophic effects are attainable when repetition durations for concentric exercise are between 0.5-8 seconds; it is further concluded by Schoenfeld et al., (2015) that whilst repetition durations over 10 seconds per repetition can cause hypertrophy, they are inferior to shorter durations of 0.5-8 seconds. In addition, both Burd et al., (2012) and Pereira et al., (2016) found that comparatively longer duration repetition times (1 seconds concentric and 4-6 seconds eccentric) were more effective at producing hypertrophic muscular changes than faster repetition speed (1 second concentric, 1 second eccentric). Finally, Gehlert et al., (2015) conclude that force output, rather than time under tension, is a greater mediator of hypertrophic gains since a larger number of type 2 muscle fibres are recruited.


Additional research has focused on the effect of training intensity and volume on muscular hypertrophy in the elderly population. Csapo and Alegre (2016) concluded, via their meta-analysis, that whilst hypertrophic and strength effects are small in the elderly population, training with higher intensities of load is more effective in producing changes in muscular hypertrophy and strength than low intensity load is. However, Csapo and Alegre (2016) add that the ability to increase muscle size is reduced in the elderly population, and whilst high intensity training may be favourable with regards to increasing muscle size and strength, low intensity training is still sufficient to increase muscle size and strength when compared to inactive populations. However, in contrast, both high intensity and high volume (2 × 10–15 repetitions at 80% of 1RM) and very low intensity and high volume (1 × 80–100 repetitions at 20% of 1RM) training protocols have both demonstrated positive effects on muscular hypertrophy following a 12 week training period, as demonstrated by (Roie et al., 2013). Additionally, both high and low volume training have been shown to provide similar improvements in muscle quality and cross sectional area in elderly women (Radaelli et al., 2013), suggesting that simply training, in its’ essence alone, is enough to improve muscular hypertrophy in the elderly.


It is evident to see there are numerous methods which can be utilised in order to attain muscular hypertrophy. In the specific interdependence of hypertrophy, speed and muscular strength in weightlifters, it would seem that high intensity, low volume training is a suitable method which can be employed in order to increase muscular hypertrophy. It must be remembered, however, that training age, time spent in the sport and kinaesthetic learning experiences will all, to a degree, interplay, and shall therefore influence the method of hypertrophy training selected (Hass et al., 2001: Pathak et al., 2016). Therein lies the question of which method is most suitable for each individual. It is known that with relatively untrained athletes, low intensity, high volume training is sufficient to induce a significant degree of hypertrophy, as demonstrated in the discussion section of this article. Moreover, it could be beneficial with regards to injury prevention, since the risk of injury in weightlifting is reported to be greater with increased feelings of fatigue, especially during the initial training years (Keogh and Winwood, 2017). However, although excessive and rapid increases in training loads are deemed responsible for a large proportion of non-contact, soft-tissue injuries, chronic, high intensity workloads have been shown to demonstrate a protective mechanism against injury and must therefore be taken into consideration when designing an appropriate training programme for an athlete (Gabbett, 2016). Additionally, adherence to training is postulated to be elevated when an individual enjoys their training, and for the majority of the population, training programmes must be achievable in the early stages of participation, since this heightens enjoyment and may therefore increase programme adherence. However, when athletes possessing a greater training age are considered, it would appear that a higher intensity training programme, utilising an array of rest intervals is a far more efficient training method that can be used in order to induce muscular hypertrophy, through the targeting of specific mechanical and metabolic mechanisms (Mangine et al., 2015). Additionally, since strength increases linearly with muscular hypertrophy, it would seem that both hypertrophy and maximal strength can be achieved by utilising one training method per cycle, and therefore maximise training efficiency.

The common perception that ‘hypertrophy’ training must be within high repetition ranges for multiple sets remains a unique paradigm that exists due to its repetitive use in weight training. However, it is perhaps not the most efficient way in which muscular hypertrophy, and therefore increased strength, can be achieved. Both high intensity-low volume and low intensity-high volume training are able to produce gains in maximal strength and muscular hypertrophy; however, the selection of one method over another should be based upon an athlete’s physical maturation, their experience of physical activity and movement patterns and phase of weightlifting. It is hoped that this article will enable a new insight into the methods that can be used for hypertrophy training, and therefore assist in the ‘de-bunking’ of a long-standing training philosophy which has been thought of as the optimal method for many years. Ultimately, there is no ‘one size fits all’ method, as each individual athlete requires a unique tailoring of their programme in order to adjust for their physical differences. However, it is useful to understand the spectrum of tools that are available to the weightlifting coach as this enables a broader understanding and depth of knowledge that will produce better athletes.

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