Understanding Velocity Loss

Understanding velocity loss is key to managing fatigue and optimizing performance in resistance training. This article explores how objective metrics like bar speed can guide training intensity and adaptation without necessarily relying on advanced technology.

By Antonio Squillante, Ph.D CSCS*D RSCC*D

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Introduction

Velocity-based training (VBT) has become increasingly popular over the last decade or so. Many consider VBT the future of heavy resistance training and for good reason. VBT makes it possible to measure training intensity and training volume with a degree of accuracy that would otherwise be impossible without the use of objective metrics. VBT is also extremely useful when it comes to monitoring the effect of fatigue. The number of studies investigating velocity loss and its effect on strength, power, and hypertrophy is simply overwhelming. What we have learned in recent years tracking and measuring bar velocity has helped shape our understanding of resistance training. We can now rewrite old guidelines and recommendations in a way that benefits all, those who do live and breathe VBT and those who are still debating whether or not purchasing a linear position transducer may be a good investment.

Training Load Chart: Old News

Let’s talk about load, repetitions, and all things strength and power. Shall we?

We are all way too familiar with the following chart:

Training Load Chart

Both the National Strength and Conditioning Association (NSCA) and the American College of Sports Medicine (ACSM) have published a more or less updated version of this chart edition after edition of textbooks and manuals for the last 15 to 20 years. This is also known as the training load chart. It indicates the number of repetitions expected to reach concentric failure under different loading conditions. For those who may not be familiar with the concept of concentric failure, this is the same as volitional failure. 

A more recent version of this chart can be found in a paper published by Nuzzo et al., in 2024. To date, this is the most comprehensive literature review, including a total of 952 repetitions-to-failure tests, completed by 7,289 individuals in 452 groups from 269 studies.

Nuzzo, J. L., Pinto, M. D., Nosaka, K., & Steele, J. (2024). Maximal number of repetitions at percentages of the one repetition maximum: a meta-regression and moderator analysis of sex, age, training status, and exercise. Sports Medicine, 54(2), 303-321

As useful as it may seem, this chart does little to no good when it comes to heavy resistance training. Suffice to say, volume as measured by the number of repetitions per set is vastly overestimated. Let’s take a look at numbers to understand what that means. When it comes to heavy resistance training, one would expect to do sets of 5-6 repetitions with a load equal to or greater than 80% of 1RM. Although it is possible to do sets of 5-6 repetitions at a load of, let’s say, 85% of 1RM, it is hard to sustain effort for more than 2-3 repetitions at best. The same is true for explosive lifts. With a load of 50-60% of 1RM, it is possible to do sets of up to 15 repetitions, but it is unlikely, to say the least, to be able to sustain effort for more than 8-10 repetitions.

Understanding Adaptation 

Adaptation to heavy resistance training is predicated upon the ability to increase motor unit recruitment by exerting maximal effort at every repetition. Motor unit recruitment has very little to do with volume; it is mainly about intensity. Effort is measured in terms of velocity and sheer mechanical power output. To preserve effort, it is necessary to manage the effects of fatigue. Broadly speaking, autoregulation by repetitions in reserve (RIR) or rating of perceived exertion (RPE) has been used to measure effort and monitor fatigue in the weight room. The so-called estimated repetitions to failure (ERF) scale, first published by Hackett et al. in 2012 and later revisited by Zurdos et al. in 2016, has helped revise the original training load chart, making amendments where possible to account for the effect of fatigue on neuromuscular performance.

Helms, E. R., Cronin, J., Storey, A., & Zourdos, M. C. (2016). Application of the repetitions in reserve-based rating of perceived exertion scale for resistance training. Strength and conditioning journal, 38(4), 42.

RPE measures fatigue as proximity to muscle failure. It is not a measure of true effort. To understand effort  it is important to understand fatigue and how fatigue affects neuromuscular performance. It is important to understand velocity and power and how effort and fatigue are tied into objective metrics – i.e velocity loss –  rather than a subjective scale. 

Here is where things get really complicated, really fast.

Neuromuscular Fatigue: What It Matters

Muscle fatigue is one of the most complex topics in all of scientific literature. In his original paper from 1995, Dr. Roger Enoka – one of the pioneers in the study of muscle physiology – defined muscle fatigue as a temporary impairment in muscle function measured as a decrease in mechanical power output. If the definition of muscular fatigue does not seem to pose a challenge, understanding the physiological factors contributing to fatigue is quite complex.

Measuring fatigue is difficult, to say the least. Measuring the effects of fatigue on performance, however, is somewhat more feasible. Lifting heavy weights creates a fair amount of fatigue, and that fatigue is measured as a decrease in neural drive. The type of fatigue experienced when lifting heavy weights is often referred to as central fatigue, as it primarily affects the motor cortex. Central fatigue is normally measured using what is known as the interpolated twitch technique (ITT), a laboratory method used to quantify loss of muscle function – i.e., fatigue – by delivering a brief electrical stimulus to a muscle or its nerve during a maximal voluntary contraction.

Pushing a set to volitional failure triggers different mechanisms, which are linked with a decrease in intracellular pH rather than a sheer decrease in neural drive. This is often referred to as peripheral fatigue. A single set of 10-12 repetitions of any compound lift can spike a five- to seven-fold increase in blood lactate compared to resting conditions (Lawson et al., 2022). This is often called metabolic stress, and it’s a byproduct of the temporary decrease in oxygen available to the tissues, also known as hypoxia. It is a very common condition when training for muscle hypertrophy. It is less common when training for strength and power. 

Monitoring The Effects of Fatigue: RPE-RIR

RPE and RIR can measure the effects of peripheral fatigue very well, quantifying effort as proximity to volitional failure. However, RPE and RIR fall short when volitional failure is not an option.  In a study published by Vasquez-Huot et al. in 2013, RPE was measured under three different loading conditions: 50% of 1RM, 70% of 1RM, and 90% of 1RM. Under each condition, subjects were asked to perform, in a randomized order, sets to failure or sets of 3 repetitions only. The number of repetitions and RPE were recorded at the end of each set. Peak concentric power output was also measured at the first and last repetitions of each set to monitor a change in performance over time. RPE increased with the number of repetitions, scoring above 15 on the Borg scale (which ranges from 6 to 20). A score equal to or greater than 15 indicates a very hard effort. Sets of 10-12 repetitions at 70% of 1RM (12RM) scored as high as sets of only 3 reps at 90% of 1RM (4RM).

Vasquez, L. M., McBride, J. M., Paul, J. A., Alley, J. R., Carson, L. T., & Goodman, C. L. (2013). Effect of resistance exercise performed to volitional failure on ratings of perceived exertion. Perceptual and Motor Skills, 117(3), 881-891.

RPE and RIR captured fatigue but not effort. A higher score on any of the ERF or RPE-RIR scale does not correspond to a true measurement of performance, as indicated by the drastic decline in mechanical power put associated with a higher perception of effort. Effort and performance are objective metrics. The perception of effort is not indicative of true performance. When it comes to heavy resistance training, performance drives adaptation. It is all about performance. 

A more suitable option for managing fatigue during heavy lifting is velocity loss. Velocity loss is linked to volitional failure, RIR, and RPE, but it is objective and supported by solid scientific evidence. Bar velocity is a measurement of performance and as such, any decrease in bar velocity is relevant (Morán-Navarro, et al., 2019). Sánchez-Medina and González-Badillo were the first to explore the idea of using velocity loss to measure fatigue in the weight room. Well over a decade after their first publication in 2011, velocity loss is now considered a reliable and objective metric to assess the effects of fatigue on neuromuscular performance.Two numbers are especially important to remember: 20% and 40%. A velocity loss of 10-20% is indicative of little to no fatigue. This is when true effort can be measured and bar velocity stays well above average through the entire set. Conversely, a velocity loss equal to or greater than 40% is indicative of extreme fatigue. Effort deteriorates and bar velocity suddenly drops half-way through the set. This holds true across different loading conditions, for explosive lifts or heavier lifts alike.

Here is where things get really interesting, really fast.

Monitoring The Effects of Fatigue: Velocity Loss

Velocity loss not only helps to measure the short-term effects of fatigue, but also provides insights into long-term adaptations to resistance training. Velocity loss explains the difference between neurogenic and myogenic adaptation, two very familiar terms for those who became acquainted with all things VBT reading the work of  Dr.Carmelo Bosco. You cannot discuss VBT without mentioning Bosco, can you? No, at least I cannot. 

Bosco used to talk about neurogenic adaptation as opposed to myogenic adaptation to differentiate between strength training proper, and hypertrophy training. Heavy resistance training promotes an increase in strength and rate of force development by enhancing neural drive and motor unit recruitment, with little to no change in muscle size. In simpler terms, heavy resistance training trains the brain, not just the muscle. Hence, the term neurogenic adaptation or adaptations that originates – genesis in Greek means giving birth – from the brain (neuro). Conversely, hypertrophy training promotes an increase in muscle cross-sectional area (CSA), which may or may not lead to increases in strength and power Hence, the term myogenic adaptation, or adaptations that originates from the muscle, in Greek myo used to indicate the muscle tissue. 

In a randomized controlled trial published in 2020 in Medicine & Science in Sports & Exercise, 64 participants were assigned to one of four groups. They trained twice a week for 8 weeks using different velocity loss thresholds: 0% (VL0), 10% (VL10), 20% (VL20), and 40% (VL40). Training intensity was similar across groups (70-85% 1RM), and the number of sets was kept the same. Measures such as muscle cross-sectional area, jump height, and peak isometric force were taken before and after training. All groups showed significant improvements in strength and power, but those who trained with higher velocity loss (V20-V40) presented with a more significant increase in muscle mass. The difference in adaptation was explained by looking at overall training volume, with the number of repetitions per session nearly doubling with each increase in velocity loss, reaching almost 300 repetitions at 40% velocity loss.

Pareja-Blanco, F., Alcazar, J., Sánchez-Valdepeñas, J., Cornejo-Daza, P. J., Piqueras-Sanchiz, F., Mora-Vela, R., … & Alegre, L. M. (2020). Velocity loss as a critical variable determining the adaptations to strength training. Med Sci Sports Exerc, 52(8), 1752-1762.

A velocity loss of about 20% is considered ideal when training for strength. With heavier loads (70-80% 1RM), training volume is usually limited to no more than 3-6 repetitions per set. A velocity loss of less than 10% may even be better when training with lighter and more explosive lifts (50-60% 1RM).

Heavy Resistance Training

Explosive Resistance Training

A velocity loss of 30% or more is considered ideal when training for muscle hypertrophy. Although training to volitional failure may not always be necessary to promote muscle growth, increased volume (sets and repetitions) and greater time under tension can lead to a more significant increase in muscle protein synthesis and lean body mass (LBM).

Practical Applications

Those who are keen to explore the use of velocity loss and VBT can elevate their understanding by studying the work of Preja-Blanco and Galiano, applying principles of evidence-based practice with a linear position transducer (LPT). For everyone else, the following table offers a great starting point to replace the old training load chart, helping to make more educated decisions about training intensity and volume.

VBT is a whole field of research in itself. I strongly recommend exploring all aspects of velocity and resistance training, not limiting your keywords on PubMed or Google Scholar to just velocity-based training and velocity loss. Typing the following keywords will open a wealth of knowledge:

The list of research papers and books on the topic is extensive. It ranges from some of the early classic works in sports science by authors like Behm and Sale, to studies on isokinetic training published in the early 1970s. It is quite an endeavor to delve into so much science and publications, but for those who prefer a more conservative approach following these guidelines will be more than enough to begin appreciating the power of evidence-based practice and the benefits of velocity-oriented training with no need for high-tech equipment. All it takes is a little effort: start by making small adjustments to your sets and repetitions, and you’ll see significant improvements in performance. It’s time to put science into action.

References

  1. Enoka, R. M. (1995). Mechanisms of muscle fatigue: central factors and task dependency. Journal of Electromyography and Kinesiology, 5(3), 141-149.
  2. González-Badillo, J. J., Marques, M. C., & Sánchez-Medina, L. (2011). The importance of movement velocity as a measure to control resistance training intensity. Journal of human kinetics, 29, 15.
  3. Helms, E. R., Cronin, J., Storey, A., & Zourdos, M. C. (2016). Application of the repetitions in reserve-based rating of perceived exertion scale for resistance training. Strength and conditioning journal, 38(4), 42.
  4. Lawson, D., Vann, C., Schoenfeld, B. J., & Haun, C. (2022). Beyond mechanical tension: A review of resistance exercise-induced lactate responses & muscle hypertrophy. Journal of Functional Morphology and Kinesiology, 7(4), 81.
  5. Morán-Navarro, R., Martínez-Cava, A., Sánchez-Medina, L., Mora-Rodríguez, R., González-Badillo, J. J., & Pallarés, J. G. (2019). Movement velocity as a measure of level of effort during resistance exercise. The Journal of Strength & Conditioning Research, 33(6), 1496-1504.
  6. Nuzzo, J. L., Pinto, M. D., Nosaka, K., & Steele, J. (2024). Maximal number of repetitions at percentages of the one repetition maximum: a meta-regression and moderator analysis of sex, age, training status, and exercise. Sports Medicine, 54(2), 303-321
  7. Pareja-Blanco, F., Alcazar, J., Sánchez-Valdepeñas, J., Cornejo-Daza, P. J., Piqueras-Sanchiz, F., Mora-Vela, R., … & Alegre, L. M. (2020). Velocity loss as a critical variable determining the adaptations to strength training. Med Sci Sports Exerc, 52(8), 1752-1762.Vasquez, L. M., McBride, J. M., Paul, J. A., Alley, J. R., Carson, L. T., & Goodman, C. L. (2013). Effect of resistance exercise performed to volitional failure on ratings of perceived exertion. Perceptual and Motor Skills, 117(3), 881-891.
Antonio Squillante

Antonio Squillante 
Ph.D CSCS*D RSCC*D

Antonio Squillante is an Assistant Professor of Kinesiology at Point Loma Nazarene University in San Diego. He serves as the Head of Sport Performance and Training for the USA Cycling National Track Sprint Program. Since 2023, Antonio has been a member of the NSCA Board of Directors. In addition to his academic and professional roles, Antonio is a published author and a highly sought-after international speaker and lecturer.