Discover the key to more effective resistance training by learning how the intensity of your efforts affects muscle hypertrophy and strength, backed by recent meta-regression findings.
Overview
- What did they test? Robinson et al. (2023) investigated the dose-response relationship between the proximity to failure (measured as Repetitions in Reserve, (RIR)) during resistance training and its effects on strength gains and muscle hypertrophy.
- What did they find? The study found that muscle hypertrophy significantly increases as training sets are performed closer to failure. In contrast, strength gains showed negligible differences with different proximities to failure.
- What does it mean for you? For individuals aiming to maximize muscle growth, training closer to failure may be beneficial. However, when focusing solely on strength gains, proximity to failure is less important, allowing for more flexible training approaches.
What’s The Problem?
Training to failure has been a hotly debated topic on fitness forums and social media for decades. The concept behind training to failure is that it optimizes neuromuscular adaptations by recruiting more motor units and maximizing muscle fiber activation. This is thought to trigger muscle fibers to adapt by increasing both size and strength. In the past few years, a surge of new studies and meta-analyses has improved our understanding of the advantages and drawbacks associated with training to failure.
A meta-analysis in 2021 analyzed four studies and found that training to failure was associated with a greater increase in muscle size compared with non-failure 1. However, the subgroup analysis revealed that when volume was equalized, the advantage of training to failure disappeared 1. A subsequent meta-analysis included seven studies, finding that training to failure produces similar results as non-failure for muscle hypertrophy 2. Interestingly, a subgroup analysis on trained individuals indicated there was a small benefit to training to failure 2. The most recent meta-analysis found there was a small advantage for training to failure versus non-failure for muscle hypertrophy, but the effects were dependent on the definition of failure 3. The authors stated that “there is no evidence to support that resistance training performed to momentary muscular failure is superior to non-failure resistance training for muscle hypertrophy and (ii) higher velocity loss thresholds, and theoretically closer proximities-to-failure do not always elicit greater muscle hypertrophy 3.” Taken together, this indicates that the benefits of training to failure for muscle hypertrophy are not universally consistent and may be influenced by several factors such as volume and training status.
Muscle strength is a little more tricky when deciding to train to failure (or not) because intensity is a stronger determinant of changes in strength than volume 4. Indeed, some of the aforementioned meta-analyses suggest there are no differences in muscle strength when training to failure, independent of overall training volume 1, while others suggest an advantage of not training to failure 2 5.
Recently, the debate on training to failure has turned towards repetitions in reserve, which is a relatively new concept to guide training intensity, defined as how many reps you have left prior to reaching failure 6. Another new(er) method is using velocity loss thresholds, which are often used in strength sports and in collegiate or professional teams’ strength and conditioning 7. In the present study under review, the authors Incorporated these two aspects into their analysis, while including other variables like volume, training status, proximity to failure, and other factors, to help us understand if training to failure is needed to maximize muscle size and strength.
Purpose
To meta-analyze existing research and quantify the dose-response relationship between proximity to failure (RIR) and resistance training outcomes, specifically muscle strength and hypertrophy.
Hypothesis
The authors did not state a specific hypothesis.
What Did They Test and How?
Participants
All studies referenced in existing meta-analyses were gathered. Subsequently, any additional studies identified during the data extraction process or known to the researchers that met the inclusion criteria were also included.
To qualify for this meta-analysis, studies had to be published in English within peer-reviewed journals, pre-print repositories, or as MSc or PhD theses. Additionally, participants in these studies needed to have no known medical conditions or injuries. The studies must have standardized either set or repetition volumes and maintained load conditions within ±5% of one-repetition maximum (1RM). Furthermore, they were required to compare at least two different proximities to failure and include measurements of maximal strength (such as isometric, isotonic, or isokinetic tests) or direct assessments of muscle hypertrophy (like ultrasound or magnetic resonance imaging). Any studies that did not meet these criteria were excluded from the analysis.
Data extraction involved collecting information on the study populations, training intervention specifics, and outcomes of interest, including muscle hypertrophy and strength gains. When necessary data were not reported in the studies, the researchers contacted the original authors to request the raw or mean values. If there was no response within three months, the required data were calculated based on the information available in the figures and tables provided in the manuscripts.
