Should you train to failure?

“No pain no gain! Has it ever occurred to you to think about the science behind this phrase? Unfortunately, the level of pain experienced is not always proportional to the gains. The reality is far more nuanced. Training to failure refers to the voluntary inability to complete a given movement when performing an exercise. While this may be relevant for the development of certain physical qualities, it’s definitely not for others. These include the development of maximum power and speed. These qualities need to be trained without accumulated fatigue, so that maximum effort is achieved with each repetition. For example, if my level of fatigue reduces the speed I’m able to generate during a throw, I’m no longer working on maximum speed. Similarly, optimal development of the cardiorespiratory system should take place at target intensities, which are usually expressed as a percentage of the reserve heart rate. So, if the onset of fatigue during a cardiovascular training session forces me to greatly reduce my running speed, the target intensity is not maintained and the gains will be sub-optimal. Where muscle failure could be relevant is in hypertrophy.

On the one hand, the main reason proposed for training to failure is to maximize muscle fiber recruitment (6). Only fibers recruited by the nervous system will be worked on and will be able to gain volume and mass. However, there is no direct evidence that training to failure maximizes muscle recruitment (3). With a load allowing 15 maximum repetitions, the muscle’s electrical activity (muscle recruitment) peaks three to five repetitions before failure (5). In this way, even to maximize muscle recruitment with light loads, it’s not necessary to achieve failure. What’s more, in the presence of heavy loads, the different types of muscle fibres are recruited from the outset.

On the other hand, the metabolic stress associated with achieving failure would be non-negligible for hypertrophy purposes. Extensive use of the anaerobic-lactic pathway in bodybuilding will create an acidosis localized to the muscles worked. For a given load, the higher the number of repetitions, the greater the acidosis. The latter stimulates the production of growth hormones, confirming that maximizing the number of repetitions while achieving failure would be of some use. What’s more, when the intensity of the muscle contraction requested is above 50% of the maximum voluntary contraction, the compression on the arteries due to the contraction of the muscles requested completely blocks arterial flow. The longer this muscular contraction lasts, the more the muscle’s oxygenation decreases. This depletion of oxygen would contribute to hypertrophy (4). Consequently, training to failure, which maximizes time under muscular tension, would have hypertrophic benefits by optimizing the decrease in muscular oxygenation.

In concrete terms, the scientific literature suggests that there are benefits to performing at least a few sets to failure in a hypertrophy-oriented program (3). Caution is called for, however, as few studies have examined the subject, and there are disparities between their conclusions and protocols. Furthermore, training consistently to failure increases the risk of overtraining (1). Notably, in a 16-week study (2) of resistance training in active men, it was observed that constant training to failure can have deleterious effects on the production of hormones involved in the development of muscle mass.

In conclusion, as Schoenfeld suggested in a recent writing (3), the best approach is to plan training use to failure to maximize muscle mass gains and avoid overtraining. Once again, this method is not suitable for developing power and speed. For optimal training content, refer to a kinesiologist near you.

Written by Mathieu Lanoue, Kinesiologist.

References:
1. Fry, A. C., & Kraemer, W. J. (1997). Resistance exercise overtraining and overreaching. Sports medicine, 23(2), 106-129.
2. Izquierdo, M., et al. (2006). Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength, and muscle power gains. Journal of Applied Physiology, 100(5), 1647-1656.
3. Schoenfeld, B. (2016). Chapter 4: Role of resistance training variables in hypertrophy. Science and Development of Muscle Hypertrophy. Human Kinetics.
4. Scott, B. R., Slattery, K. M., & Dascombe, B. J. (2015). Intermittent hypoxic resistance training: Is metabolic stress the key moderator?. Medical hypotheses, 84(2), 145-149.
5. Sundstrup, E., et al. (2012). Muscle activation strategies during strength training with heavy loading vs. repetitions to failure. The Journal of Strength & Conditioning Research, 26(7), 1897-1903.
6. Willardson, J. M., Norton, L., & Wilson, G. (2010). Training to failure and beyond in mainstream resistance exercise programs. Strength & Conditioning Journal, 32(3), 21-29.