The assessment of one-repetition maximum (1RM) is a fundamental component of strength training and conditioning, providing a key benchmark for evaluating maximal strength and guiding appropriate training loads. Over time, several methodologies have been developed to estimate 1RM, each offering distinct advantages and challenges. This paper reviews the current literature on various methods used to evaluate 1RM, including direct measurement techniques, predictive equations, velocity-based assessments, and perceived exertion scales.

Direct 1RM measurement involves the lifter attempting to lift the heaviest weight they can manage for a single repetition. While this method is widely regarded as the most accurate for determining maximal strength (Dhahbi, 2024), it has been criticized for being time-intensive and potentially risky, especially for untrained individuals or those with underlying health concerns (Pérez-Castilla et al., 2021). For instance, Nickerson et al. (2020) highlighted the risk of muscle soreness and temporary functional decline following direct 1RM testing, which can make it impractical for use in larger groups (Hosseini et al., 2023). Additionally, the psychological pressure of performing a maximal lift can lead to underperformance, further complicating the accuracy of the test (Pérez-Castilla et al., 2021).

To address the limitations of direct measurement, predictive equations have been developed to estimate 1RM based on submaximal lifts. This approach involves performing multiple repetitions at a lighter load, using regression models to predict the 1RM (Bianco et al., 2015). While this reduces physical strain, it is not without drawbacks. As Bianco et al. (2015) observed, predictive equations can either underestimate or overestimate actual 1RM performance, potentially introducing errors into training programs. Moreover, these equations tend to be population-specific, often developed with young, trained individuals, and may not accurately translate to older adults or untrained populations (Tan et al., 2015).

Velocity-based methods have emerged as a promising alternative for estimating 1RM. These methods leverage the relationship between load and movement velocity, where the speed of the barbell during a lift is used to predict the maximum load an individual can lift (Jidovtseff et al., 2011). Studies have shown that individualized load-velocity profiles can offer highly accurate 1RM predictions, with correlations as high as 0.99 in some cases (Thompson et al., 2021). For example, Macarilla et al. (2022) demonstrated that average concentric velocities at specific percentages of 1RM could yield precise predictions in trained athletes. However, factors such as the type of exercise and the athlete’s experience level can influence the accuracy of this method (Larsen, 2023).

Another innovative approach involves perceived exertion scales, such as the Borg Rating of Perceived Exertion (RPE) scale, where individuals self-report their exertion levels during submaximal lifts. These perceived exertion levels can then be used to estimate 1RM (Bonnevie et al., 2019). While promising in healthy populations, the applicability of this method in clinical populations, such as those with chronic obstructive pulmonary disease (COPD), requires further exploration (Bonnevie et al., 2019). Additionally, the subjective nature of perceived exertion introduces variability, as individuals’ perceptions of effort may differ based on their psychological or physiological conditions.

Building on subjective perception scales, the introduction of the Velocity Perception Scale (VPS) as a method for determining 1RM (one-repetition maximum) represents a significant advancement in strength evaluation within resistance training. This methodology is based on the athlete’s subjective perception of movement velocity during load lifting, allowing for the estimation of 1RM in a less fatiguing and more individualized manner. The VPS is used to quantify the intensity of resistance exercise through execution velocity. The velocity at which a load is moved is a determining factor in the muscular adaptations induced by training (Bautista et al., 2016). Perception of velocity has been studied in various research settings, showing that athletes can accurately assess movement velocity, which allows for effective adjustments to training loads (Sindiani, 2020).

Integrating multiple methods can enhance the precision and reliability of 1RM assessments. For instance, combining velocity-based assessments with perceived exertion ratings could offer a more comprehensive view of an individual’s strength capabilities (Thompson et al., 2021). Similarly, blending direct measurements with predictive equations may help offset the inherent limitations of each approach (Fitas, 2023). This mixed-method approach is particularly advantageous when working with diverse populations, as it allows for tailored assessments that account for individual differences in strength, experience, and health status.

Evaluating 1RM is a multifaceted process that can be approached through various methodologies, each with its own strengths and limitations. While direct measurement remains the gold standard for accuracy, practical constraints often necessitate the use of alternative methods such as predictive equations, velocity-based assessments, and perceived exertion scales. Future research should continue refining these methods and examining their applicability across diverse populations to improve the effectiveness of strength training programs.

Another way to approach 1RM calculation thanks to new technologies

The determination of 1RM (one-repetition maximum) using the intra-set progressive method with a Functional Electromechanical Dynamometer (FEMD) is an innovative technique that allows for the controlled and precise evaluation of an individual’s maximum strength. This method is based on the progressive increase of loads within the same set, where resistance is incremented with each repetition until muscle failure is reached. Below, the fundamentals, procedure, advantages, disadvantages, and practical applications of this method are detailed. 

1. Fundamentals of 1RM Calculation with Electromechanical Dynamometer 

The FEMD allows the application of a progressively increasing load, automatically adjusting the resistance and speed with each repetition. This device measures the force generated by the subject in real-time, facilitating the identification of the point of muscle failure. The ability to continuously monitor force and speed provides a dynamic approach to maximum strength assessment, which is especially useful in training and rehabilitation environments (Hidalgo et al., 2022). 

2. Procedure for Calculating 1RM Using the Intra-Set Method with Dynamometer 

The procedure for calculating 1RM using a FEMD involves several key steps: 

1. Dynamometer Setup: Adjust the dynamometer for the specific exercise (e.g., bench press, squat) and ensure that the load can be progressively increased. 
2. Determination of Execution Speed: Establish a constant movement speed, which will be maintained throughout all repetitions. This speed may vary depending on the training goal (e.g., maximum strength or hypertrophy) (González-Millán et al., 2015).
3. Submaximal Initial Load: Start with a load between 40% and 60% of the estimated 1RM to allow the subject to complete the initial repetitions with ease. 
4. Progressive Load Increase: Gradually increase the load with each repetition, generally between 5% and 10% of the initial load. 
5. Recording of Force and Resistance Generated: The FEMD records the force generated during each repetition, allowing for the monitoring of the subject’s ability to move the load. 
6. Reaching Failure: Failure occurs when the subject can no longer complete the repetition with proper technique. The load in the last completed repetition is taken as the basis for the 1RM. 
7. Final Calculation of 1RM: Based on the data collected, the FEMD can extrapolate the subject’s 1RM, automatically adjusting the final value based on observed performance.

3. Advantages of the Intra-Set Progressive Method with Electrical Dynamometers or Motorized Devices

The advantages of this method include (González-Millán et al., 2015): 

• Precise Measurement: The FEMD provides precise real-time data on force and speed, enabling accurate 1RM calculation. 
• Controlled Progression: Load increments are automatic and consistent, reducing the risk of human error in load progression. 
• Lower Risk of Injury: By precisely controlling the load and failure point, the risk of injury is minimized compared to a direct 1RM test. 
• Fatigue Monitoring: This method allows for detecting athlete fatigue and adjusting the load or stopping the exercise before severe failure occurs. 

4. Disadvantages of the Intra-Set Method with Electrical Dynamometer or Motorized Devices

There are some disadvantages in the use of Motorized Devices: 

• Limited Access to Technology: FEMDs are not available in all training centers, limiting their use. 
• Learning Curve: Trainers and athletes must familiarize themselves with the use of the dynamometer and data interpretation. 
• Accumulated Fatigue: If load increments are not well-calibrated, the athlete may fatigue too quickly, affecting the accuracy of the 1RM calculation. 

5. Practical Applications of the Intra-Set Method with FEMD or Motorized Devices

This method has various practical applications (González-Millán et al., 2015), such as: 

• Continuous Strength Assessment: It allows for regular 1RM assessments without subjecting the athlete to maximum lifting tests that could be more dangerous. 
• Advanced Programming: The data obtained can be used to adjust training loads accurately and dynamically. 
• Rehabilitation: In rehabilitation contexts, the method allows for precisely adjusting the load progressively, avoiding overloading that could hinder recovery.

6. Recommendations for Calculating 1RM Intra-Set with FEMD

To optimize the calculation of 1RM, it is recommended to: 

• Moderate Progression: Ensure load increments are small enough to avoid premature fatigue. 
• Velocity Control: Maintain a constant velocity during the exercise to ensure reliable results. 
• Frequency of Tests: Perform this method every 6-8 weeks to avoid overworking the athlete. 

The intra-set progressive method using a functional electromechanical dynamometer (FEMD) is a valuable tool for maximum strength evaluation, offering a precise and controlled approach that can be adapted to various populations and training objectives.

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