Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions

Introduction

It is evident that climbing harder routes requires greater physical strength. The holds are generally small, moves can be long and the climbs themselves tend to be steep. Baláš et al. (2014) found a significant interaction between the inclination of a wall and the force-time integral of foot support, and accordingly, the load on the upper extremities increased by 1% for each 1% increase in inclination. 

Higher performing climbers therefore tend to have stronger fingers, better endurance, more shoulder and upper body power, and higher anaerobic fitness (For reviews see Langer et al., 2023a; Saul et al., 2019; Stien et al., 2022).

Incorporating strength training within training for climbing has been shown to enhance climbing performance and climbing-specific strength outcomes (For reviews see Langer et al., 2023b; Stien et al., 2023). Strength training comes in two main methods: hypertrophy training increases muscle volume while maximum strength training focuses on neuromuscular adaptations. Combining the two tended to be the most effective (Langer et al., 2023b).

Strength training can be complex with a lot of variation in training metrics such as frequency, volume, and load. One parameter that recently gained interest is proximity to failure. It describes when to end a set: either when it is no longer possible to perform another rep, or when the capacity exists to perform a few more reps, thus having “repetitions in reserve” (RIR).

Previous studies and meta-analyses (Grgic et al., 2022; Refalo et al., 2022; Vieira et al., 2021) have compared the effect of training to failure versus not to failure, either directly (failure vs. not to failure) or indirectly (alternate set structure, velocity loss). However, this categorical comparison limits understanding of the dose-response relationship between RIR and training outcomes. This study addressed the limitations of previous research by considering proximity to failure as a continuous variable, examining the effects across a range of RIR values using meta-regressions. This approach provides a more nuanced understanding of how different proximities to failure influence maximum strength and hypertrophy outcomes.

Study details

How was this study conducted?

  • An exploratory meta-analysis was performed without a systematic search or preregistration.
  • Studies were collected from existing relevant meta-analyses and additional sources known to the authors.
  • Data were extracted and multi-level meta-regressions were performed to analyze the effect of proximity to failure with repetitions in reserve (RIR) on strength and muscle hypertrophy.

What were the inclusion criteria of the studies?

  • Studies published in English in peer-reviewed journals, pre-print repositories, or as MSc/PhD theses.
  • Measured maximal strength and/or muscle hypertrophy.
  • Compared at least two different proximities to failure.
  • Included set and/or repetition volume-equated conditions.
  • Load-equated conditions (±5% of 1RM).
  • Participants had no known medical conditions or injuries.

How many studies were included in the review/meta-analysis?

  • 55 studies with 243 total effects for strength outcomes.
  • 26 studies with 140 total effects for muscle hypertrophy outcomes.

What are the main characteristics of the included studies?

  • Characteristics of the participants:
    • Average age: 27.83 years.
    • Varied training statuses from untrained to trained individuals.
  • Characteristics of the training interventions:
    • Interventions lasted an average of 8.28 weeks.
    • Training variables included load, volume, and frequency, with most studies involving 2-3 sessions per week and using loads of around 75% of 1RM.

Conclusion and practical application

Central conclusion:

  • Strength gains are minimally influenced by proximity to failure.
  • Muscle hypertrophy increases as sets are terminated closer to failure. 

Corollary or secondary conclusions:

  • Load (or intensity) is a more significant predictor of strength gains than RIR. Currier et al., (2023) demonstrated that high intensity is the most important metric for maximum strength training. Higher strength gains are elicited by training at higher intensities (≤ 8RM, >60% 1RM) (Lopez et al., 2021; Refalo et al., 2021). Experienced athletes need to train at an intensity of at least 80% 1RM for further strength gains (Kraemer et al., 2002).
  • This study highlights the difference between load-mediated and intra-set-fatigue-mediated changes in proximity to failure. Training with a higher load automatically leads to a closer proximity to failure. Research indicates that this load-mediated proximity to failure favors strength gains.
  • Training closer to failure or further away from failure each offers distinct benefits for building maximum strength. Training closer to failure may enhance strength by improving motor pattern specificity, psychological resilience, and muscle size. On the other hand, training further from failure helps manage fatigue, allows for higher training frequencies, enhances the rate of force development, and reduces the risk of overtraining.

What does the review leave out?

  • The exact relationship between RIR and training outcomes remains unclear due to the exploratory nature of the meta-analysis.
  • Long-term effects and potential differences in populations in the response to training proximity to failure are unknown.

References

Robinson, Z., Pelland, J., Remmert, J., Refalo, M., Jukic, I., Steele, J., & Zourdos, M. (2023). Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions.

Baláš, J., Panáčková, M., Jandová, S., Martin, A. J., Strejcová, B., Vomáčko, L., Charousek, J., Cochrane, D. J., Hamlin, M., & Draper, N. (2014). The effect of climbing ability and slope inclination on vertical foot loading using a novel force sensor instrumentation system. J Hum Kinet, 44, 75-81. https://doi.org/10.2478/hukin-2014-0112

Currier, B. S., Mcleod, J. C., Banfield, L., Beyene, J., Welton, N. J., D’Souza, A. C., Keogh, J. A., Lin, L., Coletta, G., & Yang, A. (2023). Resistance training prescription for muscle strength and hypertrophy in healthy adults: a systematic review and Bayesian network meta-analysis. British Journal of Sports Medicine, 57(18), 1211-1220.

Grgic, J., Schoenfeld, B. J., Orazem, J., & Sabol, F. (2022). Effects of resistance training performed to repetition failure or non-failure on muscular strength and hypertrophy: A systematic review and meta-analysis. Journal of sport and health science, 11(2), 202-211.

Kraemer, W. J., Ratamess, N. A., & French, D. N. (2002). Resistance training for health and performance. Current sports medicine reports, 1, 165-171.

Langer, K., Simon, C., & Wiemeyer, J. (2023a). Physical performance testing in climbing—A systematic review. Frontiers in sports and active living, 5, 1130812.

Langer, K., Simon, C., & Wiemeyer, J. (2023b). Strength training in climbing: a systematic review. Journal of Strength and Conditioning Research, 37(3), 751-767.

Lopez, P., Radaelli, R., Taaffe, D. R., Newton, R. U., Galvão, D. A., Trajano, G. S., Teodoro, J. L., Kraemer, W. J., Häkkinen, K., & Pinto, R. S. (2021). Resistance training load effects on muscle hypertrophy and strength gain: systematic review and network meta-analysis. Medicine and Science in Sports and Exercise, 53(6), 1206.

Refalo, M. C., Hamilton, D. L., Paval, D. R., Gallagher, I. J., Feros, S. A., & Fyfe, J. J. (2021). Influence of resistance training load on measures of skeletal muscle hypertrophy and improvements in maximal strength and neuromuscular task performance: A systematic review and meta-analysis. Journal of Sports Sciences, 39(15), 1723-1745.

Refalo, M. C., Helms, E. R., Hamilton, D. L., & Fyfe, J. J. (2022). Towards an improved understanding of proximity-to-failure in resistance training and its influence on skeletal muscle hypertrophy, neuromuscular fatigue, muscle damage, and perceived discomfort: A scoping review. Journal of Sports Sciences, 40(12), 1369-1391.

Saul, D., Steinmetz, G., Lehmann, W., & Schilling, A. F. (2019). Determinants for Success in Climbing: A Systematic Review. Journal of exercise science and fitness, 17(3), 91–100. https://doi.org/10.1016/j.jesf.2019.04.002

Stien, N., Riiser, A., Shaw, M. P., Saeterbakken, A. H., & Andersen, V. (2023). Effects of climbing-and resistance-training on climbing-specific performance: a systematic review and meta-analysis. Biology of Sport, 40(1), 179-191

Stien, N., Saeterbakken, A. H., & Andersen, V. (2022). Tests and Procedures for Measuring Endurance, Strength, and Power in Climbing-A Mini-Review. Frontiers in sports and active living, 4, 847447. https://doi.org/10.3389/fspor.2022.847447

Vieira, A. F., Umpierre, D., Teodoro, J. L., Lisboa, S. C., Baroni, B. M., Izquierdo, M., & Cadore, E. L. (2021). Effects of resistance training performed to failure or not to failure on muscle strength, hypertrophy, and power output: a systematic review with meta-analysis. The Journal of Strength & Conditioning Research, 35(4), 1165-1175.

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