In Part 1 of this series I took a very long look at eccentric contractions and their role in stimulating muscle growth. I also looked at some of the other possible factors that may signal muscle hypertrophy to take place including adenosine tri phosphate depletion, creatine phosphate depletion, increased blood flow, restricted blood flow, oxygen deprivation and time under tension. In Part 2 I continued talking about time under tension and looked at rep speed in relation to Olympic lifters as a possible reason as to why training to failure may not be necessary in order to build new muscle tissue. In this third installment I intend to continue my quest to get to the bottom of the question: Is training to failure necessary for muscle hypertrophy?
I came across this very interesting research paper (1) conducted at McMaster University (and those of you from Toronto reading this who thought no good ever comes from Hamilton, shame on you) when looking around for information on this subject and through this paper alone I believe we can draw some kind of conclusions. The researchers posited that it would be the total number of contractions that would result in the highest amount of motor unit activation and fiber recruitment and be a greater factor in the stimulation of muscle protein synthesis that the intensity of the exercise taking place, and that the stimulation of myofibrillar protein synthesis would occur regardless of the intensity as long as the exercise was done until muscular failure. Wait, what?
What this study suggests is that it is the total volume of work completed, rather than the intensity, will lead to greater muscle fiber recruitment, as long as the exercise is done until failure. So there is apparently an argument for training until failure. Allow me to continue with this study in particular.
In the case of this study the subjects who trained in the 30 reps until failure range had the highest number of reps completed and the largest workload (in other words, the largest amount of time under tension, regardless of failure being reached). One of the most interesting findings in this study is that at 24 hours post exercise, myofibrillar protein synthesis elevated in the group that performed 30 reps to failure. That’s right, the rate of protein synthesis actually increased AFTER 24 hours had passed since training was completed. I have never heard of this happening in any other case. This makes for very strong evidence that it is the amount of work that the muscles do that is the most important factor in stimulating muscle growth. The more work, the more time under tension, the more muscle growth. Period.
This can be explained by looking at how strength is built. Strength is reliant on training your body to recruit motor units to all fire in unison in order to lift the heavy weight. This is not the same as training the muscle. Working the muscle is using those motor units to move the weight and doing so many times. The authors of this study went on to say that increasing protein synthesis post exercise is not entirely load dependent, but it appears to be dependent of the exercise volume which is what leads to the much longer rate of elevated protein synthesis. It isn’t just initiating protein synthesis that matters, but continuing that elevated rate of muscle hypertrophy over the longest period of time possible.
By using this elevated protein synthesis and its ability to stimulate mixed protein fractions, meaning both sarcoplasmic and myofibrillar growth, bodybuilders have managed to grow larger muscles that those who focus primarily of lifting heavy weights. Once again, it appears to be the volume of work done, regardless of rep range, rep speed or load, that is the greatest factor in muscle-building. It also means that taking your reps until failure, or very close to failure is in fact more important than we may have thought up until now in this series.
There are many research papers (2, 3) that suggest that not only time under tension, but fatigue is a critical component to stimulating muscle hypertrophy. Now we’re finally getting somewhere. Fatigue can be best accomplished when training to failure.
When training to failure the muscle cell lacks the ability to function normally. The fatigue contractions cause the sarcomere units to be unable to return to their unattached resting state and calcium ions flood the muscle cells which further disrupts the delicate balance of the cell. This massive cellular disruption that is the result of the failure reps cause a dramatic increase in myogenic regulatory factors that are responsible for protein synthesis and also in various markers of inflammation and regeneration.
Let’s put this all together and see if we can come up with some sort of formula for growing our muscles. One way to put it would be that training until failure in order to maximize fatigue and the muscle signaling that is the result of the failure reps, combined with the total volume of work that we are accomplishing during training are what is responsible for new muscle tissue growth. This means that in order for you or I to grow new muscle we must either train to failure if we are not already and/or we need to up the total volume that we train with by either adding more work sets, more high rep training (this can also be accomplished by performing slower reps as this will increase the time under tension thereby increasing the workload), or both . By increasing the workload that we are asking of our muscles, and by training them to failure we are creating an environment that makes muscle growth inevitable.
The biggest variable in this equation is you. Are you prepared to work progressively harder each time you train? Are you willing to train well into the pain zone to get those last failure reps? I know that researching for these articles has changed my mental approach to training. Time will tell if I reap the results from this newfound knowledge. Until next time my friends,
1. Burd NA, West DW, Staples AW, Atherton PJ, Baker JM, Moore DR, Holwerda AM, Parise G, Rennie MJ, Baker SK, & Phillips SM (2010). Low-load high volume resistance exercise stimulates muscle protein synthesis more than high-load low volume resistance exercise in young men. PloS one, 5 (8) PMID: 20711498
2. Goldspink G, & Howells KF (1974). Work-induced hypertrophy in exercised normal muscles of different ages and the reversibility of hypertrophy after cessation of exercise. The Journal of physiology, 239 (1), 179-93 PMID: 4855427
3. Goldberg AL, Etlinger JD, Goldspink DF, & Jablecki C (1975). Mechanism of work-induced hypertrophy of skeletal muscle. Medicine and science in sports, 7 (3), 185-98 PMID: 128681