One-Repetition Maximum / Repetition Maximum

1. Abstract

The One-Repetition Maximum (1RM), conceptually mirrored in Dutch clinical exercise science as the Herhalingsmaximum, represents the gold-standard operational metric for assessing human dynamic muscular strength. Defined as the maximum external load or resistance an individual can displace through a complete, standard range of motion (ROM) exactly once with sound biomechanical technique, the 1RM serves foundational roles across exercise physiology, neuromuscular assessment, sports psychology, and physical rehabilitation. While conventionally categorized as a physiological and biomechanical measurement tool, the 1RM is intrinsically bound to psychomotor and psychological constructs, notably perceived exertion, task-specific self-efficacy, pain catastrophizing, central motor drive, and psychophysiological tolerance to near-maximal neuromuscular distress. Assessment methodologies encompass both direct maximal testing protocols—involving progressive, ramped loading until volitional exhaustion or technical failure—and indirect submaximal prediction paradigms derived from linear, exponential, or multi-repetition regressions (e.g., Brzycki, Epley, Lombardi, O’Conner formulations). Psychometrically, direct 1RM testing demonstrates extraordinary reliability across clinical and athletic cohorts, with intraclass correlation coefficients (ICCs) regularly exceeding .95 to .99 and coefficients of variation (CV) typically residing below 3.5% to 5.0%. Validity evaluations demonstrate profound construct and criterion validity against laboratory-based isometric peak force transducers, isokinetic dynamometry, and cross-sectional skeletal muscle mass quantified via magnetic resonance imaging. Furthermore, within clinical exercise psychology and physical therapy contexts, such as those formalized in the Dutch manual Training van spierkracht en spierfunctie (Van Gestel et al., 1997), the 1RM protocol operates as an objective behavioral benchmark for calibrating exercise intensity, assessing rehabilitation trajectories, combating kinesiophobia, and tracking neuroplastic neuromuscular adaptations.

2. Keywords

One-Repetition Maximum, 1RM, Herhalingsmaximum, muscular strength, neuromuscular assessment, exercise psychology, submaximal strength prediction, self-efficacy, psychophysics, resistance training

3. Authors

The historical origin of the repetition maximum concept dates back to post-World War II rehabilitation, pioneered predominantly by military physician and physical medicine pioneer Dr. Thomas L. DeLorme (1917–2014) along with physical therapist Arthur L. Watkins at the Gardiner General Hospital in Maine during the late 1940s. DeLorme initially conceptualized the ’10-repetition maximum’ (10RM) to establish systematic progressive resistance exercise (PRE) regimens for rehabilitating orthopedically injured soldiers, which subsequently evolved into the formal assessment of the singular 1RM across sports science and athletic performance.

In the Dutch clinical and physical therapy sphere referenced in the source documentation, the adaptation and operational protocol were systematized in the textbook Training van spierkracht en spierfunctie (1997), co-authored by M. J. M. Van Gestel, J. M. A. Mens, H. J. Stam, and colleagues within academic rehabilitation networks in the Netherlands, including the Department of Physical Therapy and Rehabilitation Medicine at Erasmus University Medical Center, Rotterdam. Inquiries regarding modern clinical adaptations of standardized 1RM testing in the Netherlands are commonly directed through Dutch physical therapy organizations such as the Koninklijk Nederlands Genootschap voor Fysiotherapie (KNGF).

4. Purpose

The primary purpose of the One-Repetition Maximum (1RM) assessment is to determine an individual’s absolute dynamic muscular capacity for a specified compound or isolated kinetic chain movement. From an applied physiological and psychometric viewpoint, accurate identification of the 1RM satisfies several distinct clinical, experimental, and psychomotor objectives:

• Precision Prescription of Exercise Intensity: Muscular adaptations (e.g., myofibrillar hypertrophy, absolute strength gains, metabolic endurance, or power development) depend heavily on the relative percentage of mechanical load utilized during resistance exercise. Clinicians and strength scientists use direct or predicted 1RM values to establish targeted training zones, such as prescribing 80–85% of 1RM for neural strength gains, 65–75% for structural hypertrophy, or 40–60% for muscular endurance and submaximal motor re-education.
• Diagnostic Assessment of Neuromuscular Asymmetries and Deficits: The 1RM provides a standard, reproducible metric for evaluating bilateral strength differences (e.g., comparing dominant versus non-dominant limb capacity) and agonist-to-antagonist ratios (e.g., quadriceps-to-hamstring balance). Significant deviations highlight neuromuscular inhibition, chronic disuse atrophy, or elevated musculoskeletal injury risk.
• Quantification of Therapeutic Rehabilitation Outcomes: In orthopedics, rheumatology, and geriatric medicine, longitudinal tracking of 1RM or estimated 1RM assesses the restoration of physical function following surgical interventions (such as total joint arthroplasty or anterior cruciate ligament reconstruction) and aids in monitoring sarcopenia reversal.
• Integration with Exercise Psychology and Psychophysics: Beyond physical mechanics, the 1RM serves as an objective anchor in psychological investigations of perceived physical competence, task-specific self-efficacy, and tolerance of intense sensory discomfort. Exposure to progressive 1RM testing protocols has been validated in behavioral medicine to mitigate kinesiophobia (fear of movement or reinjury) by systematically challenging negative cognitive appraisals through graduated, successful physical performance.

5. Psychological Construct

Although commonly viewed as a purely physiological or biomechanical index, the One-Repetition Maximum operates at the intersection of neuromuscular capacity, behavioral volitional persistence, psychophysics, and self-efficacy theory. In measurement frameworks, performance on a 1RM test reflects a complex composite construct composed of several interacting physiological and psychological dimensions:

Maximal Dynamic Neuromuscular Capacity

This dimension represents the biomechanical core of the construct: the coordinated recruitment, rate coding (discharge frequency), synchronization, and firing patterns of alpha motor units against a peak external resistance. It includes cross-bridge actomyosin cycling velocity under heavy loads and effective intra- and inter-muscular coordination, which together prevent excessive antagonist co-contraction.

Task-Specific Self-Efficacy and Outcome Expectancy

Drawing on Albert Bandura’s social cognitive theory, executing a true maximal lift requires high task-specific self-efficacy. When lifters approach near-maximal loads (above 90% of expected capacity), self-efficacy directly impacts central motor unit recruitment. Lifters with low self-efficacy often display hesitation, suboptimal motor trajectories, premature voluntary abandonment during sticking regions, and higher baseline sympathetic distress.

Perceived Exertion and Sensory Processing Tolerance

Maximal physical efforts provoke intense somatosensory and interoceptive feedback, including acute muscular strain, baroreceptor stimulation from elevated intra-abdominal and intra-thoracic pressures (e.g., during the Valsalva maneuver), joint shear stress, and rapid metabolic acidosis. Successful completion of a 1RM requires an individual to tolerate extreme sensory discomfort, anchoring the absolute maximum of the Borg Rating of Perceived Exertion (RPE) scale (an RPE of 10 or Borg CR10 score of 10) and the Repetitions in Reserve (RIR) scale (an RIR of 0).

Central Inhibitory Overcoming (Central Motor Drive)

Human skeletal muscle possesses protective central nervous system and autogenic inhibitory mechanisms, such as input from the Golgi tendon organ (GTO) and cortical inhibitory circuits, which shield the musculoskeletal system from structurally damaging forces. The true expression of a 1RM requires high central motor drive and intentional volitional disinhibition. This process can be shaped by verbal encouragement, psychological arousal, motivational state, and learned mental strategies.

6. Theoretical Framework

The measurement foundation of the One-Repetition Maximum is grounded in two primary theoretical domains: classical neuromuscular physiology and psychophysical behavioral theory.

Neuromuscular and Henneman’s Size Principle

From a neuromuscular perspective, the 1RM operates according to Henneman’s Size Principle. This principle dictates that motor units are systematically recruited in order of increasing size and excitation threshold: smaller, fatigue-resistant Type I motor units are engaged first under low loads, while larger, high-threshold Type IIa and IIx fast-twitch motor units are progressively recruited as external resistance nears maximal capacity. Consequently, the 1RM is the single behavioral test that requires simultaneous recruitment and maximal firing frequency of all available motor units within a targeted functional muscle group.

Hill’s Force-Velocity Relationship

The biomechanical foundation of the 1RM also derives from A. V. Hill’s characteristic hyperbolic force-velocity relationship of skeletal muscle. As the external load approaches the 1RM threshold, the shortening velocity of the contracting muscle fascicles declines toward zero (the quasi-isometric boundary). In modern velocity-based training (VBT) paradigms, the 1RM corresponds to the minimal velocity threshold (MVT)—the lowest concentric barbell velocity at which an individual can complete a repetition without failing.

Psychophysical Scaling and the Central Governor Model

Psychologically, the 1RM test aligns with Gunnar Borg’s psychophysical scaling theory and Timothy Noakes’s Central Governor Model. Borg posited that physical performance is directly regulated by a conscious synthesis of peripheral physiological signals, including mechanoreceptive, metabolic, and cardiovascular feedback. Under the Central Governor framework, the sensation of fatigue and the urge to stop a lift before true physical failure operate as protective psychological mechanisms. Thus, reaching a valid 1RM requires the lifter to manage central affective feedback, maintain task engagement, and deliberately push past the protective perceptual impulse to cease effort.

7. Validity

Extensive psychometric and biomechanical research confirms the robust validity of the One-Repetition Maximum across athletic, healthy adult, and clinical populations.

Construct Validity

Construct validity is shown through the test’s ability to differentiate distinct levels of muscular conditioning, training experience, and athletic specialization. Experienced strength athletes consistently demonstrate higher 1RM scores, lower variability across consecutive attempts, and superior minimal velocity thresholds compared to untrained counterparts. Furthermore, construct validity is supported by strong positive correlations with non-invasive physiological markers of strength, including skeletal muscle cross-sectional area (CSA) assessed via magnetic resonance imaging (MRI) or computed tomography (CT), with correlation coefficients routinely between r = .70 and r = .88.

Criterion and Convergent Validity

When evaluated against laboratory gold standards, dynamic 1RM measures show strong convergent validity with peak isometric force measured by load cells or force platforms (e.g., Isometric Mid-Thigh Pull [IMTP]), with correlations ranging from r = .78 to r = .92. Similarly, high concordance is observed between 1RM values and peak torque measurements gathered via isokinetic dynamometry across velocities of 60°/s and 180°/s (r = .75–.89). Submaximal predictive models (such as those developed by Brzycki, Epley, and Mayhew) also show acceptable criterion validity against direct 1RM tests, especially when the test sets involve fewer than 10 repetitions to failure.

Predictive Validity

The 1RM exhibits strong predictive validity across practical athletic and clinical metrics. In athletic contexts, 1RM values in compound movements such as the barbell back squat and power clean account for 50% to 75% of the variance in sprinting acceleration, vertical jump height, and change-of-direction performance. In clinical and geriatric contexts, baseline lower-extremity 1RM scores predict mobility preservation, operational scores on the Short Physical Performance Battery (SPPB), activities of daily living (ADL) independence, and long-term fall risk.

8. Reliability

The One-Repetition Maximum is recognized as one of the most reliable performance measures in human movement science, provided testing follows standardized warmup and execution protocols.

Test-Retest Reliability and Intraclass Correlation Coefficients

Numerous methodological studies document high test-retest reliability across multiple exercise modalities, muscle groups, and populations:

• Upper Body Movements: In standardized assessments such as the barbell bench press, latissimus pull-down, and seated chest press, test-retest reliability coefficients (ICCs) regularly range between .96 and .99 in healthy young adults, and between .92 and .97 in clinical and older cohorts across 48- to 72-hour retest intervals.
• Lower Body Movements: Complex lower-extremity movements, including the 45-degree leg press, barbell back squat, and knee extension, consistently yield ICC values exceeding .95, frequently reaching .98 to .99 in resistance-trained individuals.

Measurement Error and Bland-Altman Limits of Agreement

Absolute reliability indices confirm low inherent measurement error. Standard error of measurement (SEM) values are generally reported between 1.5% and 4.2% of the total measured weight, while coefficients of variation (CV) fall comfortably below the accepted 5.0% threshold for physiological metrics. Bland-Altman analyses confirm that systemic bias between repeated trials is minimal, though unfamiliarity can introduce a small learning effect (typically an initial 2% to 6% performance gain) between sessions 1 and 2, highlighting the importance of familiarization trials.

9. Factor Analysis and Structural Dimensionality

While the 1RM is a performance test rather than a subjective psychometric questionnaire, its structural dimensionality has been examined using Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) across dynamic athletic testing batteries.

Latent Factor Structure of Dynamic Strength Batteries

When multiple 1RM exercises are administered together (e.g., bench press, squat, deadlift, overhead press, leg press, lat pull-down), factor analytic studies consistently reveal distinct, robust latent dimensions:

• Upper-Body Pushing Strength: Heavy factor loadings (> .80) for bench press, dumbbell press, and overhead barbell press onto a common anterior-chain dynamic strength factor.
• Upper-Body Pulling Strength: High factor loadings (> .75) for seated cable row, bent-over barbell row, and latissimus pull-down.
• Lower-Body Axial/Triple Extension: Substantial loadings (> .85) for barbell back squat, trap-bar deadlift, and 45-degree leg press onto a foundational lower-extremity dynamic force factor.

Structural Equation Modeling with Psychophysical Constructs

Structural equation models examining the relationship between 1RM performance and psychological scales (such as the Exercise Generalized Self-Efficacy Scale and the Borg RPE Scale) show that self-efficacy exerts a strong direct effect (β = .34 to .48, p < .001) on true maximal effort achievement. In these models, higher self-efficacy buffers against premature technical failure, producing acceptable overall fit indices (CFI > .95, TLI > .94, RMSEA < .06).

10. Instrument / Measurement Tool

The One-Repetition Maximum assessment protocol is an instrumental, performance-based test requiring standardized equipment and clear movement criteria.

• Test Classification: Performance-based maximal physiological and psychomotor assessment; can be conducted directly (Maximal test) or predicted indirectly (Submaximal test).
• Target Populations: Healthy adults, competitive athletes, geriatric populations, and clinical rehabilitation patients (e.g., orthopedic, musculoskeletal, and cardiopulmonary rehabilitation).
• Assessment Scope: Multi-joint compound and single-joint isolated exercises covering the upper extremities (e.g., bench press, chest press, seated row), lower extremities (e.g., squat, leg press, knee extension), and axial skeleton.
• Standard Direct Testing Procedure:
  1. General Warm-up: 5–10 minutes of low-intensity aerobic activity, followed by dynamic mobility exercises specific to the joint complexes being tested.
  2. Specific Warm-up Sets:
     • Set 1: 8–10 repetitions at approximately 40–50% of the estimated 1RM.
     • 1-minute rest interval.
     • Set 2: 5–6 repetitions at approximately 60–70% of the estimated 1RM.
     • 2-minute rest interval.
     • Set 3: 2–3 repetitions at approximately 80–85% of the estimated 1RM.
     • 3-minute rest interval.
  3. Maximal Load Attempts: The participant attempts a single repetition at their projected 100% capacity. If successful, load is increased by 2.5–5.0% for upper-body movements or 5.0–10.0% for lower-body movements after a 3- to 5-minute passive rest period. If the attempt fails, load is reduced by a corresponding increment.
  4. Protocol Termination: The final successfully completed load represents the 1RM. To avoid excessive neuromuscular fatigue, the definitive 1RM should ideally be established within 3 to 5 maximal attempts.
• Submaximal Prediction Equations (Indirect Testing): When direct maximal testing is clinically contraindicated (e.g., in individuals with severe osteoporosis, acute cardiovascular disease, or active joint pathology), submaximal repetitions to volitional failure (2–10 repetitions) are recorded, and the 1RM is calculated using validated formulas:
  • Brzycki Equation: 1RM = Weight Lifted / [1.0278 – (0.0278 × Repetitions)]
  • Epley Equation: 1RM = Weight Lifted × [1 + (0.0333 × Repetitions)]
  • Lombardi Equation: 1RM = Weight Lifted × Repetitions^0.10
• Scoring and Metrics: Absolute strength (kg or lbs lifted) and relative strength (load lifted divided by body mass or fat-free mass, expressed as kg/kg).

11. Permissions & Fee and Test Year

The 1RM concept and its operational protocols reside firmly in the public domain and carry no licensing or access fees. Dr. Thomas L. DeLorme published the foundational methodology for progressive repetition maximum resistance testing in 1945, followed by the comprehensive text Progressive Resistance Exercise: Technic and Medical Application (Appleton-Century-Crofts) in 1951. Standardized institutional testing criteria have since been published by international bodies such as the National Strength and Conditioning Association (NSCA) and the American College of Sports Medicine (ACSM).

The Dutch clinical adaptation detailed in Training van spierkracht en spierfunctie by M. J. M. Van Gestel, J. M. A. Mens, and H. J. Stam was published in 1997 by Bohn Stafleu van Loghum (Houten, Netherlands). While the written text and commentary forms in that volume remain copyrighted by the publisher, the underlying 1RM protocol and submaximal predictive formulas may be freely used for clinical practice, athletic conditioning, and scientific research without royalites.

12. References

Baechle, T. R., & Earle, R. W. (Eds.). (2008). Essentials of strength training and conditioning (3rd ed.). Human Kinetics.

Borg, G. (1998). Borg’s perceived exertion and pain scales. Human Kinetics.

Brzycki, M. (1993). Strength testing—Predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance, 64(1), 88–90. https://doi.org/10.1080/07303084.1993.10606684

DeLorme, T. L. (1945). Restoration of muscle power by heavy-resistance exercises. The Journal of Bone and Joint Surgery, 27(4), 645–667.

Epley, B. (1985). Poundage chart. Boyd Epley Workout.

Grgic, J., Lazinica, B., Schoenfeld, B. J., & Pedisic, Z. (2020). Test-retest reliability of the one-repetition maximum (1RM) strength assessment: A systematic review. Sports Medicine – Open, 6(1), Article 31. https://doi.org/10.1186/s40798-020-00260-0

Kraemer, W. J., Ratamess, N. A., Fry, A. C., & French, D. N. (2006). Strength training: Development and evaluation of methodology. In P. J. Maud & C. Foster (Eds.), Physiological assessment of human fitness (2nd ed., pp. 119–150). Human Kinetics.

Levinger, I., Goodman, C., Hare, D. L., Jerums, G., Toia, D., & Selig, S. (2009). The reliability of the 1RM strength test for untrained middle-aged individuals. Journal of Science and Medicine in Sport, 12(2), 310–316. https://doi.org/10.1016/j.jsams.2007.10.007

Van Gestel, M. J. M., Mens, J. M. A., & Stam, H. J. (1997). Training van spierkracht en spierfunctie. Bohn Stafleu van Loghum. https://doi.org/10.1007/978-90-313-8106-7

13. Items of the Scale