Written by Luke Ashton
This article has been written by Luke Ashton for the SUBITO Summer Series. Luke draws on his formal education in Medical Science from Macquarie University and his practical experience as a qualified Personal Trainer to produce proven results for his clients in both bodybuilding and powerlifting arenas. In addition to being a qualified Personal trainer, he is a Powerlifting Australia Level 1 Coach and is the 2014 INBA South Coast Classic Overall Champion in bodybuilding.
It seems that wherever you look in the Fitness Industry that there’s a secret training tip or “one weird secret” that will get you “ripped abs” or “bigger muscles in no time”. With all of this hype, it’s easy to become side-tracked or even misled from the core tenets that will provide optimal muscle growth.
This article aims to educate you on the 3 most important elements of muscle hypertrophy, by simplifying the science behind them and providing practical tips on how to employ them. Hopefully, you will also pick up some tips to apply more structure to your training.
In 2010, Brad Schoenfeld, PhD, an internationally renowned expert on muscle hypertrophy, conducted a significant review of the scientific literature regarding training and exercise-induced hypertrophy. From this, it was hypothesised that there are 3 primary factors responsible for inducing muscular hypertrophy in response to resistance training:
- Mechanical tension.
- Muscle damage.
- Metabolic stress.
Now you may be thinking “Cool, but what the hell does this mean to me?” Well let me explain.
Mechanical tension is the load or volume you place upon a certain muscle.
Volume is often defined as: the weight you move multiplied by the number of reps and sets performed.
Research since 1975 (Goldberg et al.) has shown that overloading the mechanical tension (volume) associated with a muscle will induce a hypertrophic response. Consequently, it is clear that a continuous overload must be applied to the muscle in order for it to grow.
Put simply - if you’re able to increase your 8 repetition max over the course of a few training blocks, then it’s safe to say that you’ll have induced a hypertrophy response in the muscles associated with that exercise (neurological adaptations aside).
Another significant factor of mechanical tension is the intensity of the load.
Intensity, in the context of hypertrophy, refers to the percentage of your 1 repetition max (1RM).
In many studies, volume has been accounted for and different intensities have been used to determine their effects upon hypertrophy. The optimal range for a hypertrophic response is above 65% of your 1RM (McDonagh and Davies, 1984).
Muscles are damaged when they are subjected to a load above a certain threshold. When they’re damaged, an inflammation response occurs to repair the damaged tissue. Muscle protein synthesis (MPS) is the process of repairing these damaged muscle proteins.
MPS is an adaptive process and over time the muscle tissue will be able to withstand greater loads. This pesky habit is one of the main reasons “newbie gains” slow down after a few months.
Studies have consistently shown that MPS levels will return to baseline 36-48 hours after training (MacDougall et al. 1995). As such, training a muscle group 2-3 times per week will ensure that cumulative MPS levels are maximised over the course of that week. Nevertheless, other principles should also be used to maximise muscle damage to ensure an optimal hypertrophy response.
Another way to maximise muscle damage and resulting hypertrophy is to take an exercise to concentric failure – this means performing an exercise until you can no longer achieve the full range of motion for that exercise.
Studies have shown that taking a muscle to failure will increase the number of motor units utilised and confer a hypertrophic response (Willardson, 2007). However, training to failure on multi-joint exercises can build up stress on the central nervous system rapidly. As a result, it would be optimal for fatigue management, to perform one set of a single joint exercise, of each muscle targeted, to failure towards the end of a workout.
Many bodybuilders also use the time-under-tension principle, however some blow this concept way out of proportion by performing reps with 5 second concentric and eccentric movements. The principle however, does have its merits.
Studies by Hakkinen and his co-authors (1985) found that concentric movements of 1-2 seconds were most favourable for muscular damage (and resulting hypertrophy). Although, it is the eccentric movement, especially one where there is a stretch in the muscle present, that will provide the most bang-for-your-buck in terms of muscle damage and resulting hypertrophy response.
Shepstone et al (2005) found that eccentrics performed over 2-4 seconds produced significantly greater results in terms of muscle hypertrophy than any other duration.
Muscular hypertrophy as a result of metabolic stress is thought to be due to the accumulation of metabolites – substances produced during the process of metabolism (such as digestion or other processes within the body). This build-up of metabolites has an impact upon cell swelling, the hormonal cascade and various growth factors. These factors increase the adaptive hypertrophic response to training.
To maximise the role of metabolic stress, rest periods between 30-60 seconds and repetition ranges of 10-15 reps are best served to provide the build-up of anabolic metabolites (Goto et al, 2004).
First and foremost, these factors do not act in isolation from one another. The use of all 3 techniques will ensure a cumulative effect to help increase muscular development.
Here are some key changes you could make to your training regime to ensure that the 3 primary factors of muscular hypertrophy are accounted for, sports performance aside:
- First and foremost, consistency with your training is key.
- Begin the workout with multi-joint compound movements with the intent of increasing the weight on the bar each week. When this linear progression stalls, look to increase the number of repetitions or sets performed (or begin research for periodising your training).
- For these initials lifts, keep the intensity above 65% of your 1RM (less than 15 reps).
- Increase the frequency with which you train a muscle or muscle group. For example, if you train 3 times a week, look into a full body split that you perform three times each week. If you train 4 times throughout the week, perhaps look at an upper/lower body split which you would repeat twice each week.
- Once the multi-joint lifts have been completed, then the tempo of repetitions can be altered. To elicit the greatest amount of muscular damage, attempt exercises that encompass a stretch component (such as flies and Romanian deadlifts) and seek to perform a 2-4 second eccentric.
- For your last few single-joint exercises, you can cut down the rest period to 30-60 seconds and utilise higher repetitions (10-15) in order to build up metabolic stress on the muscle. The last set of each of these exercises should be taken to failure to ensure that a greater number of motor units are recruited.
By employing these tips and changes to your training regime, you will likely find yourself well on your way to achieving muscle hypertrophy.
Goldberg, A.L., Etlinger, J.D., Goldspink, D.F., and Jablecki, C. 1975. Mechanism of work-induced hypertrophy of skeletal muscle. Med Sci Sport Exerc 7: 185–198.
Goto, K., Nagasawa, M., Yanagisawa, O., Kizuka, T., Ishii, N., and Takamatsu, K. 2004. Muscular adaptations to combinations of high- and low-intensity resistance exercises. J Strength Cond Res 18: 730–737.
Hakkinen, K., Komi, P.V., and Ale´n, M. 1985. Effect of explosive type strength training on isometric force- and relaxation-time, electromyographic and muscle fibre characteristics of leg extensor muscles. Acta Physiolog Scan 125: 587–600.
MacDougall, J.D., Gibala, M.J., Tarnopolsky, M.A., MacDonald, J.R., Interisano, S.A., and Yarasheski, K.E. 1995. Can J Appl Physiol. 20(4):480-6.
McDonagh, M.N., and Davies, C.M. 1984. Adaptive response of mammalian skeletal muscle to exercise with high loads. Eur J Appl Physiol 52: 139–155.
Shepstone, T.N., Tang, J.E., Dallaire, S., Schuenke, M.D., Staron, R.S., and Phillips, S.M. 2005. Short-term high- vs. low-velocity isokinetic lengthening training results in greater hypertrophy of the elbow flexors in young men. J Appl Physiol 98: 1768–1776.
Willardson, J.M. 2007. The application of training to failure in periodized multiple-set resistance exercise programs. J Strength Cond Res 21: 628–631.