You may have heard your trainer say “leave 2 reps left in the tank”, but why do we say that and what the heck does it even mean?!
In terms of strength training, training to failure means reaching a point where you physically cannot complete another repetition, alternatively, we can train with ‘reps in reserve.’
Look at it like this…. Imagine you have a weight you can only pick up 10 times but not an 11th – we call this your 10 rep max or 10RM. Training to failure would mean every set you do, you complete 10 reps. Training with reps in reserve would mean you might only do 7-8 reps each set, stopping 2-3 reps shy of failure. The same could apply for your 5RM, 12RM 25RM, it wouldn’t matter, you just do that amount of reps or stop 2-3 reps shy of that. Okay – let’s continue.
A lot of resistance-training programs, particularly bodybuilding programs, involve training to failure on each set. People may associate it with a greater muscle “pump” or leave feeling more accomplished by completing the set to the point where they can no longer do it physically.
Now that’s all well and good, but is it really necessary? The short answer. No.
But because I don’t expect you to take my word for it, let’s look at some of the research that led us to that conclusion.
fatigue and recovery are two compelling arguments for not training to failure on each set.
Training to failure reduced performance and increased nasties like blood lactate and creatine kinase (an indirect marker of muscle damage). This ultimately led to the participants giving higher session ratings of perceived exertion (sRPE) significantly more than non-failure training, according to Vieira et al (2022). This just means those that trained to failure had more muscle damage and found the sessions much harder despite having the same improvements in strength. This was demonstrated in both trained and untrained lifters, regardless of whether they used heavy or light weights.
Why does this matter? A higher level of fatigue after a session means a longer recovery period before you’re physically ready to train at the same intensity again. Training to failure is said to have a negative impact on performance in the 24-48 hours following training. When compared to the control, markers of muscle damage (creatine kinase) returned to baseline in the non-failure groups in 24 hours, while it took 48 hours in the failure group. Basically, it takes longer to recover from sessions when you train to failure.
This highlights the fact that training shy of failure allows you to recover faster on average than training all sets to failure. That’s not to say you can’t train to failure, but it’s worth considering when these sessions will take place to help reduce the impact fatigue has on your weekly volume and frequency.
Staying in the 3-5 reps in reserve (RIR) range on the main lifts may be even better to mitigate fatigue over the next few days if you train a lot (three times per week or more). Furthermore, for strength, a training frequency of 2-3 times per week is superior to a frequency of one time per week, and may be preferable for hypertrophy. In other words, doing slightly less intense sessions more often in the week might be better than coming in a obliterating your legs once a week!
Won’t training to failure get me strong? Well yes, BUT training to failure is not necessary to significantly improve muscle strength, hypertrophy, and muscular endurance.
Lacerda et al. (2019) conducted a study in which males trained their legs unilaterally. One leg completes all sets to failure, while the other leg’s sets end at 1-2 before failure. Both protocols significantly increased muscle strength, size, and endurance; however, the non-failure group reported a lower total effort per session (didn’t have to physically work as hard for the same result)
So, essentially, it’s the same as working for 4 hours at $10/hour and receiving $40, or working for 2 hours at $20/hour and still receiving $40. Obviously, you’d choose the one that requires less effort to achieve the same result. Wouldn’t you?
Martorelli et al. (2017) discovered that training to failure produced significant strength and hypertrophy (size) adaptations over 10 weeks in a female-focused study; however, when volume (how much you do) is matched without training to failure, similar progress is observed.
okay, so how far from failure can I train and still maximise strength and hypertrophy?
A growing body of research suggests that training a few reps shy of failure is just as good, if not better, for hypertrophy (size) and strength outcomes than training to failure. Stopping sets 5 reps shy of failure (5 reps of your 10RM) and possibly even further from failure appear to be a viable strategy for maximising strength and hypertrophy at moderate intensities (Andersen et al., 2021). Moderate repetitions (5-7 reps at 5-10 RIR) and high repetitions (12-14 reps at 1-4 RIR) were all found to increase both strength and muscle growth.
to summarise
• Training to failure, even when volume and relative load are matched, causes more fatigue.
• Fatigue will most likely have a negative impact in that session as well as subsequent sessions throughout the week.
• A longer recovery period may reduce volume and frequency for the rest of the week. You can’t train as often because you’re so damn sore!
• This does not imply that training to failure should be avoided entirely. We recommend using it in conjunction with non-failure training. Maybe do it every other week, or even just the last set every other sessions…
so why do we say “leave 2 reps left in the tank” and what the heck does it even mean..
Leaving some reps in the tank (this could be more than two as shown above) will give you the same strength and hypertrophy results while also leaving you more recovered and less sore for your next sessions – winning!
references / to find out more…
Andersen, V., Paulsen, G., Stien, N., Baarholm, M., Seynnes, O., & Saeterbakken, A. H. (2021). Resistance Training With Different Velocity Loss Thresholds Induce Similar Changes in Strengh and Hypertrophy. Journal of strength and conditioning research, 10.1519/JSC.0000000000004067. Advance online publication. https://doi.org/10.1519/JSC.0000000000004067
Lacerda, L. T., Marra-Lopes, R. O., Diniz, R., Lima, F. V., Rodrigues, S. A., Martins-Costa, H. C., Bemben, M. G., & Chagas, M. H. (2020). Is Performing Repetitions to Failure Less Important Than Volume for Muscle Hypertrophy and Strength?. Journal of strength and conditioning research, 34(5), 1237–1248. https://doi.org/10.1519/JSC.0000000000003438
Martorelli, S., Cadore, E. L., Izquierdo, M., Celes, R., Martorelli, A., Cleto, V. A., Alvarenga, J. G., & Bottaro, M. (2017). Strength Training with Repetitions to Failure does not Provide Additional Strength and Muscle Hypertrophy Gains in Young Women. European journal of translational myology, 27(2), 6339. https://doi.org/10.4081/ejtm.2017.6339
Morán-Navarro, R., Pérez, C. E., Mora-Rodríguez, R., de la Cruz-Sánchez, E., González-Badillo, J. J., Sánchez-Medina, L., & Pallarés, J. G. (2017). Time course of recovery following resistance training leading or not to failure. European journal of applied physiology, 117(12), 2387–2399. https://doi.org/10.1007/s00421-017-3725-7
Pareja-Blanco, F., Rodríguez-Rosell, D., Aagaard, P., Sánchez-Medina, L., Ribas-Serna, J., Mora-Custodio, R., Otero-Esquina, C., Yáñez-García, J. M., & González-Badillo, J. J. (2020). Time Course of Recovery From Resistance Exercise With Different Set Configurations. Journal of strength and conditioning research, 34(10), 2867–2876. https://doi.org/10.1519/JSC.0000000000002756
Santanielo, N., Nóbrega, S. R., Scarpelli, M. C., Alvarez, I. F., Otoboni, G. B., Pintanel, L., & Libardi, C. A. (2020). Effect of resistance training to muscle failure vs non-failure on strength, hypertrophy and muscle architecture in trained individuals. Biology of sport, 37(4), 333–341. https://doi.org/10.5114/biolsport.2020.96317
Vieira, J. G., Sardeli, A. V., Dias, M. R., Filho, J. E., Campos, Y., Sant’Ana, L., Leitão, L., Reis, V., Wilk, M., Novaes, J., & Vianna, J. (2022). Effects of Resistance Training to Muscle Failure on Acute Fatigue: A Systematic Review and Meta-Analysis. Sports medicine (Auckland, N.Z.), 52(5), 1103–1125. https://doi.org/10.1007/s40279-021-01602-x