Methods for Controlling and Reporting Resistance Training Proximity to Failure: Current Issues and Future Directions

Area of Science:

• Exercise Physiology
• Sports Science
• Biomechanics

Background:

• Resistance training variables like volume, load, and frequency are established.
• Proximity to failure, defined as repetitions in reserve (RIR), lacks consistent quantification.
• Definitions of muscular failure vary across studies (momentary, volitional, or undefined).

Purpose of the Study:

• To critically evaluate current methods for quantifying proximity to failure in resistance training.
• To identify the strengths and limitations of each quantification approach.
• To propose standardized methods for future research and practice.

Main Methods:

• Review of existing literature on resistance training variables and proximity to failure quantification.
• Analysis of methods including percentage-based prescription, repetition maximum zones, velocity loss, and self-reported RIR.
• Discussion of inter-study variability in failure definitions and RIR reporting.

Main Results:

• Percentage-based prescriptions can lead to varied RIR due to individual differences.
• Velocity loss is objective but its relation to RIR fluctuates.
• Self-reported RIR is subjective and can be inaccurate; many studies fail to report RIR.
• Current methods hinder specific recommendations for optimizing hypertrophy and strength.

Conclusions:

• There is a critical need for standardized quantification of proximity to failure in resistance training research.
• Future research should explore objective measures like velocity loss, potentially combined with individualized RIR relationships.
• Clear guidelines for reporting RIR are necessary for consistent and actionable recommendations.