Strength training: What are the benefits of training to muscle failure?

Voluntary muscle failure is the neuromuscular inability to perform a concentric contraction over the full range of motion [1-3]. Training to muscle failure is thought to result in complete recruitment of motor units, which is a possible prerequisite for muscle growth stimulus [4].

What are we talking about

When the external load is high (≥ 85% 1-RM), motor units with higher recruitment threshold (type FF and FR) are immediately recruited to ensure high force production. At low loads, these motor units are not immediately recruited because high force production is not initially required [5]. As neuromuscular fatigue increases, motor units with higher recruitment thresholds are gradually recruited to compensate for the motor units that could no longer maintain force production [6]. Consequently, when voluntary muscle failure was reached, the entire available pool of motor units was recruited for the corresponding task [6]. Thus, if the training load is reduced, training to voluntary muscle failure plays an important role. In addition, training to failure may also influence muscle growth via increased metabolic load [7].

Literature on the topic.

Mitchell et al. [8] demonstrated in untrained subjects (21 ± 1 years, n = 18) that a variety of intensities (i.e., 30% versus 80% of 1-RM) can be used to induce muscle hypertrophy when training to muscle failure. In their study, the researchers used different intensities (i.e., 30% versus 80% of 1-RM) and training volumes (i.e., 1 or 3 sets) three times a week for 10 weeks. Study participants exercised quadriceps muscles at the Leg Extension each time until muscle failure. The target muscles grew in all participants. No significant difference was found between the group that trained with 80% 1-RM, with one set or with three sets, and the group that trained with 30% and three sets. The increase in strength did not differ within the group training at 80%, but was significantly greater than in the group training at 30% and three sets.

Morton et al. [9] showed in trained subjects undergoing total body training that intensity had no effect on strength training-induced hypertrophy or strength gains. Forty-nine trained men (23 ± 1 years) trained for 12 weeks. Participants were randomly assigned to a higher or lower intensity group, training at either ~30-50% or ~75-90% of 1-RM to muscle failure. Strength increased in both groups, with no significant difference between groups. The researchers found the same for hypertrophy. The authors' conclusion was that intensity has no effect on hypertrophy or strength increase in trained individuals if training to muscle failure.

Studies that found no benefit of training to muscle failure.

In contrast to the studies above, Sampson and Groeller [2] found similar adaptations with three different intensity strength training protocols, suggesting that training to muscle failure is not critical for neural and structural changes in skeletal muscle. They subjected 28 men to 4 weeks of weight training habituation. Subsequently, the subjects were divided into three groups according to their increase in strength:

• Fast contraction without muscle failure (fast concentric, 2 s eccentric).
• Fast training without muscle failure (fast concentric, fast eccentric)
• Control: training to muscle failure (2 s concentric, 2 s eccentric).

The experimental period was 12 weeks and included one-arm strength training of the biceps at 85% 1-RM three times a week with 4 repetitions each time. The control group was instructed to exercise to muscle failure in each of the 4 sets. Strength was determined by measuring 1-RM, while muscle cross-section was measured by magnetic resonance imaging. No differences were found between groups, suggesting that training to muscle failure is not a necessary condition for training adaptation.

Nobrega et al. [10] studied a strength training program that required participants to train either to muscle failure or to the point where they self-selected to stop the exercise. The intervention period was 12 weeks, during which 32 untrained men (23.0 ± 3.6 years) performed one-legged leg extensions twice weekly. Participants' legs were randomly divided into the following groups according to 1-RM and muscle cross-sectional sizes:

• High intensity (80% 1-RM) to muscle failure.
• high intensity (80 % 1-RM) until self-selected termination by the participant
• low intensity (30 % 1-RM) until muscle failure
• low intensity (30 % 1-RM) until self-selected termination by the participant.

Three sets of each were performed. Muscle cross-sectional area and 1-RM were not different at 6 and 12 weeks after the intervention. The authors believe that all study protocols were similarly effective for inducing hypertrophy and strength. Therefore, training that is terminated close to muscle failure beforehand could indicate higher efficiency. However, caution should be exercised in this interpretation, as volume load was very similar among intervention groups and thus a potential confounder.

Neves da Silva et al. [11] investigated the muscular adaptations of the quadriceps to combined strength and endurance training in elderly men. The experimental period lasted 12 weeks and consisted of strength training always preceded by endurance training within the same training session twice a week. Since the quadriceps were studied, the strength training included leg press and bipedal knee extension. Fifty-two elderly men (66 ± 5 years) were recruited and divided into 3 groups.

• Approximately 70% 1-RM, 2 - 3 sets to muscle failure.
• 50 % 1-RM, 2 - 3 sets of 8 - 10 repetitions.
• 50 % 1-RM, same training volume as the group that trained to muscle failure.

The thickness of the quadriceps muscle was measured using ultrasound. In both the group that trained to muscle failure and the group that completed the same volume, there was a significant change in size in the quadriceps. In the group that trained with 50% 1-RM for 2 - 3 sets of 8 - 10 repetitions, a statistically relevant difference in size was observed after 12 weeks. All groups increased in strength with no significant difference noted between groups.

Conclusion

In summary, the results of the cited studies indicate that lower loads may be as effective as higher loads when training is performed to muscle failure. However, the issue is not yet clear-cut, as some studies showed benefits of training to muscle failure in dynamic strength training [12-14], while others found no additional benefit [2,10,15].

Training volume and training to failure appear to be equally effective in inducing hypertrophy and strength in untrained older men, whereas younger and strength-trained individuals may benefit from training to failure. Because full recruitment of motor units can be achieved with high loads (i.e., >80% 1-RM) [5], training to muscle failure at high loads is not necessarily a prerequisite for achieving increases in functional and structural/morphological adaptations [16]. In contrast, reaching muscle failure at lower loads (i.e., ≤ 50% 1-RM) appears to be essential for increasing muscle strength and mass. Therefore, a practical recommendation is that the lower the load, the more important the intensity of the effort and thus the muscle failure in a motor task.

You can find the original article in English here.

References

1. Steele J, Fisher J, Giessing J, Gentil P. Clarity in reporting terminology and definitions of set endpoints in resistance training. Muscle and Nerve. 2017;56: 368-374. doi:10.1002/mus.25557.
2. Sampson JA, Groeller H. Is repetition failure critical for the development of muscle hypertrophy and strength? Scand J Med Sci Sport. Blackwell Munksgaard; 2016;26: 375-383. doi:10.1111/sms.12445.
3. Schoenfeld BJ. The Mechanisms of Muscle Hypertrophy and Their Application to Resistance Training. J Strength Cond Res. 2010;24: 2857-2872. doi:10.1519/JSC.0b013e3181e840f3.
4. Wernbom M, Augustsson J, Thomeé R. The influence of frequency, intensity, volume and mode of strength training on whole muscle cross-sectional area in humans. Sports Med. 2007;37: 225-64. Available: http://www.ncbi.nlm.nih.gov/pubmed/17326698
5. de Luca CJ, Contessa P. Hierarchical control of motor units in voluntary contractions. J Neurophysiol. 2012;107: 178-195. doi:10.1152/jn.00961.2010.
6. Adam A, De Luca CJ. Firing rates of motor units in human vastus lateralis muscle during fatiguing isometric contractions. J Appl Physiol. 2005;99: 268-280. doi:10.1152/japplphysiol.01344.2004.
7. Schott J, McCully K, Rutherford OM. The role of metabolites in strength training - II. short versus long isometric contractions. Eur J Appl Physiol Occup Physiol. 1995;71: 337-341. doi:10.1007/BF00240414.
8. Mitchell CJ, Churchward-Venne TA, West DWDD, Burd NA, Breen L, Baker SK, et al. Resistance exercise load does not determine training-mediated hypertrophic gains in young men. J Appl Physiol. American Physiological Society Bethesda, MD; 2012;113: 71-77. doi:10.1152/japplphysiol.00307.2012.
9. Morton RW, Oikawa SY, Wavell CG, Mazara N, McGlory C, Quadrilatero J, et al. Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. J Appl Physiol. 2016;121: 129-138. doi:10.1152/japplphysiol.00154.2016.
10. Nóbrega SR, Ugrinovich C, Pintanel L, Barcelos C, Libardi CA. Effect of Resistance Training to Muscle Failure vs. Volitional Interruption at High- and Low-Intensities on Muscle Mass and Strength. J Strength Cond Res. 2018;32. Available: https://journals.lww.com/nsca-jscr/Fulltext/2018/01000/Effect_of_Resistance_Training_to_Muscle_Failure.19.aspx
11. Neves LX da S, Teodoro JL, Menger E, Lopez P, Grazioli R, Farinha J, et al. Repetitions to failure versus not to failure during concurrent training in healthy elderly men: a randomized clinical trial. Exp Gerontol. Elsevier; 2018;108: 18-27. doi:10.1016/j.exger.2018.03.017
12. Drinkwater EJ, Lawton TW, Lindsell RP, Pyne DB, Hunt PH, McKenna MJ. Training leading to repetition failure enhances bench press strength gains in elite junior athletes. J Strength Cond Res. 2005;19: 382-388. doi:10.1519/R-15224.1.
13. ROONEY K, HERBERT RD, BALNAVE RJ. Fatigue contributes to the strength training stimulus. Med Sci Sports Exerc. 1994;26.
14. Schoenfeld BJ, Peterson MD, Ogborn D, Contreras B, Sonmez GT. Effects of low- vs. high-load resistance training on muscle strength and hypertrophy in well-trained men. J Strength Cond Res. NSCA National Strength and Conditioning Association; 2015;29: 2954-2963. doi:10.1519/JSC.00000000000958.
15. Martorelli S, Cadore EL, Izquierdo M, Celes R, Martorelli A, Cleto VA, et al. Strength training with repetitions to failure does not provide additional strength and muscle hypertrophy gains in young women. Eur J Transl Myol. PAGEPress Publications; 2017;27. doi:10.4081/ejtm.2017.6339
16. Davies T, Orr R, Halaki M, Hackett D. Effect of Training Leading to Repetition Failure on Muscular Strength: A Systematic Review and Meta-Analysis [Internet]. Sports Medicine. Springer International Publishing; 2016. pp. 487–502. doi:10.1007/s40279-015-0451-3