Articles

Methods of Quantifying Training Volume For Muscle Hypertrophy

Estimated read time = 10-15 min

Background

Increasing muscle mass is important for potentiating strength gains, improving sports performance, general health and healthy ageing (Liao et al., 2019; Taber et al., 2019). Muscle hypertrophy is best achieved through resistance training, and the variables applied within the program such as intensity, rest times, exercise selection and order, weekly frequency, and volume will influence the program’s effectiveness (Morton et al., 2019). Out of all variables, volume is suggested to be the most potent stimulator of muscle hypertrophy, whereby higher training volume generally promotes greater gains in muscle size (up to a point) (Morton et al., 2019; Schoenfeld et al., 2017).

When designing training programs, it is important to measure volume to determine if the program is supplying adequate stress to the individual. Too little stress may result in little or no adaptations, whereas too much may lead to maladaptation or injury (Kreher & Schwartz, 2012). Thus, being able to find what amount of volume is adequate for an individual becomes essential. However, difficulty can arise when deciding on how to quantify volume. Therefore, this review will focus on four-volume quantification methods for muscle hypertrophy:

  1. Counting repetitions
  2. Volume load
  3. Total Work
  4. Counting sets

Each method’s limitations and benefits will be discussed to assist you with choosing the best way to quantify training volume specifically for hypertrophy training/programming.

For the scope of this article, the focus is limited to volume quantification/tracking methods in relation to increasing muscle hypertrophy. Quantifying volume for other adaptations such as strength and power may need different tracking methods, as additional variables such as training intensity would be important for promoting these adaptations (Morton et al., 2019).

Repetition method

The simplest way to quantify training volume is by using the repetition method. This is done by counting the number of repetitions achieved for a particular exercise, training session or entire training cycle (Haff, 2010; Scott et al., 2016). Although simplistic, this method is limited because it cannot accurately reflect the total work performed and physiological stress experienced. For example, 10 sets of very high effort singles would provide a much greater training and physiological stress relative to one set of 10 repetitions, although the total number of repetitions is equal (Haff, 2010; Scott, Duthie, Thornton, & Dascombe, 2016).

Additionally, matched training volumes but with varied training intensities can result in vastly different repetition numbers. Jenkins et al. (2017) found a 6-week program of performing 3 sets of leg extensions to failure using loads corresponding to either 30% or 80% of 1RM resulted in 1751 and 558 repetitions performed, respectively, with no significant differences in training volume (sets x reps x weight). The low load high rep group could be perceived as a greater training stimulus according to the greater number of repetitions; however, muscle hypertrophy gains were similar between groups as training volume was equated. Thus, when quantifying training volume, it is vital that the load lifted is accounted for as well (Haff, 2010).

The repetition method could be used as a simple way to track progression when all other variables are held constant (Kraemer & Ratamess, 2004). For example, performing 3 sets of 90kg for 8 repetitions, at a 9RPE one week, and then doing the same in the following week but for 9 repetitions. Still, counting repetitions should likely be used in combination with other tracking methods to work around its limitations.

Volume load

An expansion of the repetition method is volume load (VL). This is typically used in research and by coaches to quantify workload due to its simplicity (Genner & Weston, 2014). VL is usually expressed as the volume load (kg) or tonnage and can be calculated from absolute or relative load lifted (Haff, 2010). Absolute load is calculated by:

Sets X reps X weight lifted (kg)

This equation can be limiting as it does not reflect relative intensity. For example, a lifter with a squat 1RM of 120kg could lift 3 sets x 5 reps x 100kg = 1500kg. If the same lifter improves their 1RM to 150kg, 3 sets x 5 reps x 100kg would still give the same absolute load value; however, the training stimulus and associated fatigue would be significantly less (Haff, 2010; Scott et al., 2016).

A possible correction is to calculate the relative load. Using the previous 120kg 1RM example, 100kg be approximately 83% of the lifters 1RM; thus, the relative load equation would now become:

Sets X reps x %1RM =

3 sets x 5 reps x 83 = 1260kg

A downfall of this equation is finding the %1RM value requires knowledge of the lifter’s 1RM. Max effort testing may not be practical to test on all exercises or with beginners (Haff, 2010; Scott et al., 2016). A possible solution could be to use rated of perceived exertion (RPE), which can estimate the %1RM value. This can be calculated from using the values in table 1 (Helms et al., 2016). An example of lifting 125kg X 5 reps at an 8RPE. According to table 1, five repetitions at an 8 RPE equates to 91% 1RM. Thus, the relative volume equation would become:

3 sets x 5 reps x 91 = 1365kg

It should be noted the percentages derived from RPE are based on mean values from the barbell back squat using a specific population and may not be entirely valid with machine based, single-joint or upper body exercises (Helms et al., 2016). Furthermore, individual variability effects how many repetitions someone can perform at particular percentages (Ormsbee et al., 2019). Lastly, individual’s ability to predict the number of repetitions they are from failure can sometimes not be totally accurate, however, can improve with experience (Steele et al., 2017).

Table 1

Reprinted from “Application of the Repetitions in Reserve- Based Rating of Perceived Exertion Scale for Resistance Training” by Helms, E. R., Cronin, J., Storey, A., & Zourdos, M. C. (2016). Strength Cond J, 38(4), p. 43

Limiting the relative volume equation is it cannot account for load changes at the same %1RM. For example, a person with a 150kg 1RM squat lifting at 65% 1RM would equate to 97.5kg. If the individual increases their squat 1RM to 200kg, 65% 1RM would now become 130kg. Keeping sets and reps equal, the relative VL equation would give the same outcome, although there is a 32.5kg difference between the loads lifted.

Another issue with VL is that it does not account for rest times between sets (Scott et al., 2016). However, explicitly to muscle hypertrophy, adding rest times to the VL equation may not be overly important. A review by Grgic et al. (2017) found that short rest times reduces the total volume performed and may be the same or less effective compared to longer rest for increasing muscle size. Under regular training conditions, rest times may not be an important factor when using VL to calculate training volume, as the total volume and mechanical tension is likely most important for hypertrophy (Schoenfeld & Grgic, 2018; Schoenfeld, 2010).

VL also cannot account for repetition velocity/duration (Scott et al., 2016). Reducing repetition tempo to increase the time the muscle is undergoing tension is hypothesised to positively influence cell signalling and enhance the hypertrophic response (Schoenfeld, 2010; Westcott et al., 2001). A review by Schoenfeld et al. (2015) found repetition durations between 0.5 to 8 seconds performed to failure leads to similar muscular hypertrophy. As long as repetitions are not intentionally performed very slow (>10 seconds) or excessively fast (<0.5 seconds) with very light loads, a wide range of repetition durations can be used for promoting muscle hypertrophy (Schoenfeld et al., 2015). However, long term training interventions using very slow repetition durations >10 seconds were limited and only studies where subjects trained to failure were included. The limitation of VL not accounting for repetition durations may not be important when the goal is muscle hypertrophy.

Lastly, VL does not account for barbell distance as this can have a significant impact on the total work performed (Haff, 2010; Hornsby et al., 2018). Not including barbell displacement can cause over or underestimations of the total work performed (Haff, 2010). For example, greater loads can be used during a partial relative to a full squat, which would increase the VL when sets and reps are matched. However, total work may be less during a partial squat (depending on the range of motion) even with greater absolute loads, because of the shorter barbell displacement (Drinkwater et al., 2012).

If barbell is displacement known, the VL equation can become:

Sets X reps x load (kg) X distance (m)

This equation is suggested to provide a more accurate estimation of total work performed, however, measuring the displacement of the mass in a gym setting would likely not be practical, and also, time-consuming (Haff, 2010; Hornsby et al., 2018; Scott et al., 2016) However, detecting changes in work during RT using the VL equation has been found to correlate to VL with displacement (r = 0.78), and could still be effective to use for quantifying training volume (Hornsby et al., 2018).

Total work

Total work is suggested to be the most valid method for quantifying training volume as it takes into account the force produced and displacement of the mass (McBride et al., 2009). During RT, this can be calculated by:

Force (load lifted in kilograms) X vertical displacement X repetitions

This equation can quantify the amount of work or calorie expenditure a lifter has done within a training session:

Work = 180kg x 0.75m x 8 = 1080 kg.m = 10591 J = 2.53 kcal

McBride et al. (2009) assessed the validity of using total work to quantify training volume. Subjects performed 3 different exercise protocols on separate days, including: 1) hypertrophy: 4 sets x 10 repetitions using 75% of 1RM on a barbell back squat 2) strength: 11 sets X 3 repetitions with 90% 1RM and 3) power: 8 sets x 6 repetitions on jump squats using no external load (0% 1RM). Volume quantification methods were compared between:

  1. volume load – (repetitions X load [kg])
  2. maximum dynamic strength volume load – (repetitions X body mass – shank mass [kg] + external load [kg])
  3. time under tension – (eccentric time + milliseconds] + concentric time +milliseconds])

Results found that total work provided the most valid determination of training volume as total work was not significantly different between the 3 exercise protocols. The authors propose that total work is the most accurate representation of a resistance exercise stimulus because both the actual force and barbell displacement is measured.

But this should be interpreted with caution as all work is not created equally. Over an extended training period, the power protocol would not result in the same amount of muscle gains relative to the hypertrophy protocol, likely due to the lack of mechanical tension experienced by the muscle fibres during explosive type movements (Earp et al., 2015; Schoenfeld, 2010). Thus, how the work is performed and not just the total would affect the subsequent training adaptations.

Another issue with the work method is the practicality of taking measurements in a gym setting. It can be expensive as it would require specialist equipment to measure force and displacement variables. Additionally, analysing the displacement of the mass for each repetition for each exercise may be difficult and time-consuming (Scott et al., 2016). For programs focusing on muscle hypertrophy, the work method may not be worth the time and effort for measuring training volume.

Counting sets

Baz-Valle et al. (2018) has recently proposed counting the total amount of sets to quantify training volume specifically for hypertrophy. The review included 14 studies which compared either; total number of sets, repetition ranges or training frequency, on muscle hypertrophy, using experienced lifters. They concluded that when the total numbers of sets are matched, training frequency, intensity and repetition range (within specific parameters) did not appear to affect gains in muscle hypertrophy significantly. The authors stated that using the total numbers of sets to quantify training volume is most reliable when sets are between 6 to 20 repetitions and are taken to near failure (3 or fewer repetitions in reserve).

Limitations of the review were as such; firstly, studies only used trained lifters, and the results may not extrapolate to untrained individuals. Secondly, the methods and muscle groups used to measure hypertrophy differed between studies and as such, particular methods and muscle groups would be more or less sensitive to changes in muscle size relative to others. Thirdly, the authors extrapolated findings from research which were not specifically designed to compare sets between programs, thus, the conclusions should be interpreted with caution.

Only one paper in the review compared sets between groups whilst keeping all other variables equal. The study involved one group performing 10 sets x 10 repetitions, and the other group performing 5 sets x 10 repetitions. Both groups increased total body muscle hypertrophy but with no significant differences between each (Amirthalingam et al., 2017). This paper did not support counting sets as a method to quantify training volume for hypertrophy (Baz-Valle et al., 2018). However, this could potentially support counting sets to quantify training volume; It might suggest there is a range of training volume/total sets where muscle gains are best, and going over this can result in diminishing returns (Barbalho et al., 2019).

A limitation with counting sets is the inability to track volume changes from performing more reps or weight. For instance, an individual over a 12-week training block may not change their total sets during the entire time; however, increases in repetitions and weight would make a significant impact on the total training volume performed. Viewing total sets alone may give the perception that training volume has not changed, where in fact, the volume may double over a 12-week period (Schoenfeld & Grgic, 2018).

It is also not clear of how sets should be counted on multi-joint (MJ) exercises which utilise multiple muscles. During MJ exercises, the contribution of particular muscles and their magnitude of stimulation can be affected by various biomechanical and physiological factors such as; muscle lengths and moment arms, joint ROMs, individual anthropometrics, and the duration and magnitude of voluntary activation. A case could be made that relative to MJ exercises, single joint (SJ) movements provide a greater hypertrophic stimulus to the targeted muscle groups. As such, MJ exercises should be counted partially, compared to SJ exercises for certain muscle groups (Schoenfeld et al., 2019).

Longitudinal research comparing MJ and SJ exercises and their effects on hypertrophy are mostly limited to the elbow flexors, and evidence is conflicting. Thus, it is not entirely clear how to count sets for individual muscle groups during MJ exercises. The authors suggest counting set volume for hypertrophy should be done on a 1:1 basis, but practitioners should also use logical rationale and personal expertise (Schoenfeld et al., 2019).

Although having limitations, using total sets to quantifying training volume could work as a planning tool to assess if the training program seems logical. Too little volume would not be optimal for muscle growth, and too much may result in diminishing returns (although an upper volume limit has not been identified) (Schoenfeld et al., 2017). This could be combined with VL to keep track of volume changes occurring from reps and weight. However, limitations and scarcity of literature on counting sets to quantify volume for hypertrophy make it difficult to draw definite conclusions.

Conclusions

Each volume quantification method presented in this review has its benefits and drawbacks. There does not appear to be one best method to use when programming for hypertrophy. It would be important that coaches take into consideration the limitations of each when using any to guide programming decisions.

Practitioners are advised to use multiple quantification methods at a given time to minimise the limitations of each. When planning or assessing programs, counting the number of sets for each muscle group performed per workout and for the week could be used to check if the training program includes too little or too much volume. VL can be utilised to see what has been done in the training plan and can compare volume performed between training weeks and blocks. Counting repetitions can be included to compare weekly progression on the same exercises if all other training variables are held constant. Although the validity of each quantification method for improving hypertrophy is not clear, it is likely most important that coaches are consistent in how they apply their chosen methods when programming for hypertrophy.

Further Research

– Research focusing on volume quantification methods and their validity, specifically for hypertrophy, is scarce. Furthermore, it is unclear how to best interpret the information provided from these methods, and how they should be used to guide programming decisions. An evidenced-based framework which can assist practitioners on how to apply and interpret volume quantifications methods for hypertrophy purposes would be beneficial.

– Very little direct research exists on counting sets per muscle group for hypertrophy purposes and the validity of this method. Furthermore, it is unclear what the upper limit of sets per muscle group per week is before muscle hypertrophy begins to decline.

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