One-repetition maximum
The one-repetition maximum (1RM), often abbreviated as one-rep max, is defined as the maximum external load an individual can lift for a single complete repetition of a given exercise through a full range of motion while maintaining proper technique.[1] This measure serves as the gold standard for assessing maximal dynamic muscular strength in non-laboratory environments due to its simplicity, minimal equipment requirements, and ability to quantify strength levels for exercise prescription and progress monitoring.[2] In strength and conditioning programs, 1RM testing is commonly applied to major resistance exercises such as the bench press, squat, and deadlift to establish baseline strength capacities and tailor training loads, with intensities typically prescribed as percentages of 1RM depending on training goals.[3] Direct 1RM assessment involves a progressive warm-up followed by incremental load increases until failure, but it carries risks including acute cardiovascular strain (e.g., systolic blood pressure exceeding 300 mmHg) and injury rates of 2.4–19%, particularly for novices or older adults, prompting recommendations for spotters, medical screening, and avoidance of the Valsalva maneuver.[3] To mitigate these hazards, indirect prediction equations—such as those using submaximal loads and repetitions to failure (e.g., 1RM = weight × (1 + 0.0333 × reps) for loads up to 10RM)—are frequently employed, offering reliable estimates with correlations often exceeding 0.90 to traditional testing.[4] The reliability of 1RM testing is high, with intraclass correlation coefficients typically above 0.91 across upper- and lower-body exercises, showing no significant gender differences but slight variations by muscle group in females.[5] Despite its utility, 1RM does not fully capture other strength qualities like power or endurance, and repeated testing can induce temporary fatigue, necessitating 48–72 hours recovery between sessions for accurate results.[5]Definition and Fundamentals
Definition
The one-repetition maximum (1RM) is defined as the maximal amount of weight that an individual can lift for one complete repetition of a given exercise using proper technique and full range of motion.[6] This measure serves as the gold standard for assessing maximal dynamic strength in non-laboratory settings within exercise science.[5] It encompasses the concentric (muscle shortening), eccentric (muscle lengthening), and brief isometric (muscle stabilization) phases of the movement, performed without external assistance to ensure the load reflects the lifter's true capability.[7] In scope, the 1RM applies specifically to individual exercises, such as the bench press, squat, or deadlift, rather than representing total-body strength.[1] It differs from multi-repetition maximums (e.g., 10RM, the maximum weight for 10 repetitions) or muscular endurance tests, which involve submaximal loads sustained over multiple reps.[8] This exercise-specific focus makes 1RM a targeted indicator of strength in resistance training modalities like weightlifting and powerlifting.[9] The concept of 1RM emerged within progressive overload principles of early 20th-century strength training, with foundational practices traced to Olympic weightlifting competitions formalized in the 1920s, where maximal single lifts determined performance outcomes.[10] The term gained scientific prominence in the 1940s through Thomas L. DeLorme's rehabilitation protocols, which emphasized determining 1RM to prescribe individualized resistance exercise loads.[11] This historical development underscores 1RM's role in quantifying strength for training intensity prescription.[12]Physiological Significance
The one-repetition maximum (1RM) represents the maximal voluntary contraction (MVC) of skeletal muscle, wherein the central nervous system recruits high-threshold motor units to achieve peak force output. This process primarily involves the activation of type II (fast-twitch) muscle fibers, which are specialized for rapid and powerful contractions due to their higher myosin ATPase activity and sarcoplasmic reticulum efficiency.[13] Such recruitment follows the size principle of motor unit activation, escalating from low-threshold type I fibers to high-threshold type II fibers as force demands increase during the lift.[14] Physiologically, 1RM performance reflects a combination of neural efficiency—improved synchronization and firing rates of motor units—and structural factors like muscle cross-sectional area (CSA), which determines the potential number of actin-myosin cross-bridges for force generation. Hormonal influences, particularly circulating testosterone, enhance force production by promoting muscle protein synthesis and satellite cell activation, thereby supporting greater 1RM values in individuals with higher baseline levels.[15] These adaptations underscore 1RM as an indicator of integrated neuromuscular function rather than isolated muscular capacity. The energy demands of a 1RM effort are met predominantly by the anaerobic phosphagen system (ATP-PC), which provides immediate high-energy phosphates for the brief, explosive contraction lasting under 10 seconds. This reliance on stored ATP and phosphocreatine minimizes contributions from glycolytic or oxidative pathways, emphasizing the test's focus on maximal power without fatigue accumulation.[16] As the gold standard for assessing absolute strength—the total force an individual can produce—1RM differs from relative strength (force normalized to body mass) or explosive power metrics like the vertical jump, which incorporate velocity and bodyweight dynamics.[17]Methods of Assessment
Direct Measurement Protocols
Direct measurement of the one-repetition maximum (1RM) involves performing maximal lifting attempts with progressively increasing loads until the heaviest weight that can be lifted for one complete repetition with proper form is identified. This method serves as the gold standard for assessing maximal strength, providing precise data essential for training prescriptions and performance evaluations. Protocols emphasize safety, standardization, and minimization of fatigue to ensure accurate results. Preparation for 1RM testing begins with a thorough warm-up to enhance performance and reduce injury risk. Participants typically perform a general warm-up consisting of 5-10 minutes of light aerobic activity, followed by specific warm-up sets using progressive loads estimated at 40-60% of the predicted 1RM for 5-10 repetitions, and then 70-80% for 3-5 repetitions. Rest intervals of 1-2 minutes are observed between these warm-up sets to allow recovery without inducing fatigue. This approach prepares the neuromuscular system while familiarizing the lifter with the movement pattern. Additionally, participants should be screened for health risks, with medical clearance obtained if necessary, and tested in a controlled environment free from distractions. The core testing protocol starts with a submaximal load approximately 80-90% of the estimated 1RM for 2-3 repetitions to gauge readiness, followed by incremental increases of 5-10% for upper-body exercises or 10-20% for lower-body exercises until failure occurs. Each maximal attempt is limited to one repetition, with the process typically concluding within 3-5 attempts to prevent excessive fatigue and central nervous system overload. Rest periods of 3-5 minutes between maximal attempts are standard to facilitate partial recovery of phosphocreatine stores and maintain effort quality. For multi-exercise sessions, such as testing bench press and squat, at least 5 minutes of rest is recommended between different lifts. Standardization is critical to ensure reproducibility and validity. Proper lifting form must be maintained throughout, including full range of motion—for instance, the barbell must touch the chest in bench press and thighs must reach parallel in squats—with consistent grip width, stance, and bar path. Spotters, ideally two for free-weight lifts, provide safety by assisting only if form breaks, using techniques like hand spotting under the bar for bench press. Environmental controls include using calibrated barbells and plates verified for accuracy, stable flooring, and consistent testing times to account for circadian variations in strength. Equipment setup, such as rack height in squats, should remain identical across sessions. As the criterion standard for maximal strength assessment, direct 1RM testing demonstrates high validity when protocols are adhered to, directly measuring the physiological capacity for a single maximal effort. Reliability is excellent, with intra-class correlation coefficients (ICC) exceeding 0.90 across various exercises, populations, and testing occasions, provided standardization includes a short warm-up and prior familiarization. For example, test-retest ICC values of 0.91-0.99 have been reported for bench press and squat in trained individuals. When direct testing poses risks or is impractical, indirect estimation techniques may serve as alternatives.Indirect Estimation Techniques
Indirect estimation techniques provide a safer, non-maximal alternative to direct 1RM testing by predicting the maximum load based on submaximal lifts performed to failure or near-failure, typically using mathematical formulas derived from load-repetition relationships. These methods rely on the inverse relationship between load intensity and the number of repetitions possible, allowing estimation without attempting a true one-repetition effort. Common approaches include rep-based equations and velocity-based training (VBT) models, which have been validated across various populations and exercises. Among the most widely adopted rep-based formulas is the Brzycki equation, which estimates 1RM as: $1RM = \frac{w}{1.0278 - 0.0278 \times r} where w is the weight lifted and r is the number of repetitions performed to failure. This formula, developed from empirical data on resistance-trained individuals, assumes a linear fatigue model. The Epley equation offers a simpler linear approximation: $1RM = w \times \left(1 + \frac{r}{30}\right) derived from observations in collegiate athletes, emphasizing proportional increases in capacity with repetitions. Another established model is the Wathen equation, incorporating exponential decay to account for fatigue: $1RM = \frac{100 \times w}{48.8 + 53.8 \times e^{-0.075 \times r}} which was formulated for practical application in strength conditioning programs. These equations are best applied within a rep range of 2-10, corresponding to submaximal loads around 85% of 1RM (yielding approximately 6 repetitions), as higher or lower reps introduce greater prediction errors due to non-linear fatigue patterns. Validation studies indicate these formulas achieve accuracy within 5-10% of actual 1RM for upper-body exercises like the bench press, with the Brzycki, Epley, and Wathen models showing the lowest mean errors (around 3-7%) in trained populations. Accuracy diminishes for lower-body exercises such as the squat, where errors can exceed 10%, and is generally lower in novices compared to athletes due to inconsistent technique and fatigue resistance. VBT enhances precision by using linear position transducers to measure bar velocity during submaximal lifts, generating a load-velocity profile; the 1RM is extrapolated by intersecting this profile with a minimum velocity threshold (e.g., 0.16 m/s for bench press). A meta-analysis of VBT applications found estimation errors of 4-8% across exercises, outperforming rep-based methods in dynamic movements by accounting for individual velocity-loss patterns. Practical tools, such as mobile apps and online calculators, implement these formulas for quick estimations; for instance, lifting 100 kg for 5 repetitions on the bench press yields an approximate 1RM of 113 kg using the Brzycki equation, guiding load selection without maximal testing. While indirect methods reduce injury risk, direct confirmation remains advisable for high-precision needs in competitive settings.Applications in Training and Research
Strength Training Programs
In strength training programs, one-repetition maximum (1RM) serves as a foundational metric for prescribing training loads, allowing coaches to tailor intensity to specific goals such as hypertrophy or maximal strength. For hypertrophy, loads typically range from 60% to 80% of 1RM, paired with 8-12 repetitions per set to optimize muscle growth through metabolic stress and mechanical tension.[18] In contrast, strength development emphasizes higher intensities of 85% to 100% of 1RM, often with 1-5 repetitions to enhance neural adaptations and force production.[19] A representative example is the 5x5 program, which uses approximately 80-85% of 1RM for five sets of five repetitions on compound exercises, promoting progressive strength gains while managing fatigue.[20] Periodization strategies leverage 1RM percentages to structure training over time, preventing plateaus and overtraining. Linear periodization involves gradual increases in intensity, such as progressing from 70% to 90% of 1RM across weeks or mesocycles, while maintaining or reducing volume to build toward peak strength.[21] Undulating periodization, by comparison, varies intensities within shorter cycles, such as alternating days or weeks at 70% 1RM for hypertrophy and 85%+ for strength, which meta-analyses indicate may yield superior strength improvements in trained individuals.[22] Deloading phases, integrated every 4-6 weeks, reduce loads to 50-60% of 1RM or 40-60% of normal training volume to facilitate recovery and supercompensation.[23] Applications of 1RM vary by exercise type to align with biomechanical demands and recovery needs. For compound lifts like the squat and deadlift, which recruit multiple muscle groups, programs often prescribe higher percentages (80-95% of 1RM) with lower repetitions (3-6) to prioritize force development and systemic strength.[24] Isolation exercises, such as the bicep curl, are typically programmed at moderate intensities (65-80% of 1RM) with higher repetitions (8-15) to target specific muscles for hypertrophy without excessive joint stress, integrating seamlessly into rep schemes that complement compound work.[18] To ensure progressive overload—the principle of incrementally increasing demands to drive adaptations—trainers re-test 1RM every 4-12 weeks, adjusting subsequent loads based on improvements to maintain optimal stimulus.[25] This periodic reassessment allows for precise scaling, such as raising working sets by 2-5% of the updated 1RM, supporting long-term program efficacy.[26]Performance and Research Evaluation
In sports such as powerlifting, the one-repetition maximum (1RM) serves as a key benchmark for performance evaluation, with the International Powerlifting Federation (IPF) competitions emphasizing maximal efforts in the squat, bench press, and deadlift to determine athlete classifications and records.[27] For instance, elite male powerlifters in the 83 kg class typically achieve squat 1RMs exceeding 250 kg, reflecting advanced relative strength greater than 2.5 times body weight.[28] In CrossFit, 1RM testing establishes baselines for programming mixed-modal workouts, where athletes must handle loads from 20% to 90% of their 1RM across lifts like the clean and jerk to optimize work capacity and scaling.[29] Similarly, in team sports like American football, 1RM assessments of the bench press and squat provide strength baselines for position-specific demands, such as linemen targeting bench 1RMs over 180 kg to correlate with on-field power output. In scientific research, 1RM functions as a primary dependent variable to quantify the efficacy of interventions, including nutritional supplements and rehabilitation protocols. Studies on creatine supplementation, for example, demonstrate that 5-20 g daily combined with resistance training yields 5-15% greater 1RM gains compared to placebo, particularly in the bench press and leg press, due to enhanced phosphocreatine stores and training volume.[30] Training interventions often track 1RM changes to evaluate hypertrophy and recovery outcomes, with protocols showing 10-20% improvements in squat and bench press 1RMs over 12 weeks in recreationally active adults.[31] In injury recovery research, 1RM deficits post-rehabilitation (e.g., 15-25% reductions in lower-body lifts after ACL reconstruction) serve as metrics to assess return-to-play readiness. Normative 1RM data from large cohorts, such as those compiled by the National Strength and Conditioning Association (NSCA) and powerlifting databases, enable percentile comparisons across demographics. For adult males aged 20-39 weighing approximately 80-90 kg, average bench press 1RMs range from 70-100 kg (intermediate level), while elite squat 1RMs exceed 180 kg or 2 times body weight. Longitudinal tracking in these cohorts reveals typical gains of 10-20% in multi-joint 1RMs after 12 weeks of progressive overload in recreationally active adults, supporting periodized program efficacy.[31]| Lift | Sex/Age Group | Average 1RM (kg, relative to ~80 kg BW) | Elite Percentile (>95th) |
|---|---|---|---|
| Bench Press | Male, 20-39 | 80-100 (1.0-1.25x BW) | >140 (1.75x BW)[32] |
| Squat | Male, 20-39 | 120-150 (1.5-1.9x BW) | >200 (2.5x BW)[28] |
| Bench Press | Female, 20-39 | 40-60 (0.5-0.75x BW) | >90 (1.1x BW)[32] |