Velocity Loss as a Metric for Controlling Induced Fatigue in Different Resistance Training Approaches

Velocity loss (VL) within the set has been established as a method to control and quantify the level of effort induced during resistance training (RT). Considering that, to serve as a valid fatigue indicator, the execution intent must be maximal. The formula to calculate it would be as follows, taking into account the highest velocity value in the set (which should typically be the first repetition) and the lowest velocity value reached within the set (which should be the last repetition performed):

The use of VL as a fatigue indicator was originally proposed in the work by Sanchez-Medina and Gonzalez-Badillo (2011), titled ‘Velocity loss as an indicator of neuromuscular fatigue during resistance training’. This study evaluated the impact of different training protocols on full squat (SQ) and bench press, finding that VL is a valid indicator of induced fatigue due to its strong correlation with fatigue markers, such as lactate and ammonia levels, as well as mechanical fatigue markers like CMJ loss and V1-Load (which is the load related with the 60% 1RM in SQ) performance reduction. Specifically, for SQ, the correlations were high: r = 0.97 for lactate, R² = 0.85 for ammonia, r = 0.92 for CMJ loss, and r = 0.91 for V1-Load performance decline, indicating VL’s predictive value for within-set fatigue. Regarding, research by Rodriguez-Rosell et al. (2020) showed that a given VL% achieved in SQ and bench press aligns with the percentage of repetitions completed, though the percentages vary by exercise. For example, for SQ, achieving ~20% VL means about half of the possible repetitions have been completed, whereas, for bench press, a ~25% VL indicates a similar threshold within intensity ranges of 50% to 80% of 1RM. This indicates that VL not only serves as a fatigue indicator but also provides insights into induced fatigue by reflecting both repetitions completed and repetitions in reserve remaining within the set.

In this line, using the VL as an independent variable to equalize exertion levels, the study by Pareja-Blanco et al. (2019) compared the acute mechanical response (CMJ, 20-meter sprint time (T20), and V1-Load) across different effort levels controlled via VL (20% and 40%) at varying relative intensities (60% and 80% of 1RM) in the SQ exercise. Results showed that higher VL within a set led to greater neuromuscular performance declines and slower post-exercise recovery. Notably, a greater VL (40%) at a lower intensity (60% 1RM) caused more fatigue and a slower recovery rate than a lower VL (20%) with a higher relative load (80% 1RM). Therefore, both factors should be considered to know the acute effort evoked after an RT session.

In summary, scientific evidence supports the use of VL as a reliable indicator of fatigue achieved within the set during RT. Besides, higher induced fatigue within the set will induce greater performance loss associated with a slower recovery rate, increase post-exercise muscle damage, and enhance the metabolic response due to increased blood lactate and ammonia concentrations.

WHAT HAPPENED WITH THE USE OF VL USING OTHER TRAINING METHODS?

In this part, the use of VL as a metric to evaluate fatigue employing different RT approaches such as cluster set or blood flow restriction (BFR) implementation will be explained.

In this regard, a cluster set involves incorporating short rest intervals between small groups of repetitions, which helps maintain performance levels during resistance training sessions (Haff et al., 2003). This method, known as cluster training, has gained significant attention due to its effectiveness in reducing the mechanical and metabolic fatigue often induced by RT (Jukic et al., 2020). Additionally, cluster training can diminish acute post-exercise mechanical and metabolic fatigue as well as hormonal stress (Oliver et al., 2015), with these beneficial effects being especially pronounced during the exercise itself.

In this line, the mechanical response (CMJ, T20, and V1-Load) at 70% of 1RM was recently compared with different set configurations (reaching 20% VL in a traditional manner and using the cluster method, as well as 30% and 40% VL traditionally) in the squat (SQ) exercise. The results showed that protocols with a higher degree of induced effort led to greater performance loss and a slower recovery rate, while the cluster protocol, despite involving a greater number of repetitions, generated the same post-exercise fatigue upon reaching the same VL value (20%) as the group that trained traditionally with the same VL (Cornejo-Daza et al., 2024). 

For that, it seems that if the same level of effort is reached during a set, regardless of the method used (traditional vs. cluster set), the acute response obtained will be similar despite the number of repetitions performed within the set.

More on this topic:

How to Train with Specific Velocity Zones | Velocity-Based Training

On the other hand, another novel approach during RT is related to including BFR during it. In this regard, the implementation of resistance exercise with blood flow restriction (BFR-RE) involves applying an inflated pneumatic cuff to the uppermost section of the limbs being exercised. This technique reduces arterial blood flow and completely occludes venous return (Scott et al., 2015). As a result, a localized hypoxic environment develops within the muscle tissue (Larkin et al., 2012). This hypoxic environment involves BFR-RT accelerates fatigue development, requiring lower mechanical work to attain a certain fatigue level (Kolind et al., 2023). A recent paper by  Sanchez-Valdepeñas et al. (2024) evaluated the acute effects of various VL thresholds during SQ with BFR on strength performance, neuromuscular activity, metabolic response, and muscle contractile properties. Results showed that increasing VL led to a greater number of repetitions completed. However, this rise was accompanied by reduced mechanical performance and more significant alterations in neuromuscular activity (as measured by RMS and MDF) during the set. In the post-exercise evaluation, higher VL thresholds resulted in greater impairments in mechanical performance and muscle contractile characteristics, along with heightened responses in blood lactate levels. 

The following figure shows the post-exercise lactate response of the previously mentioned article.

Hence, also with BFR implementation, VL will be a critical variable to determine the response after an RT exercise.

To sum up, VL should be considered a metric to monitor induced fatigue, even when some resistance training approaches, such as cluster training or blood flow restriction, are implemented.

REFERENCES

Cornejo-Daza, P. J., Villalba-Fernandez, A., Gonzalez-Badillo, J. J., & Pareja-Blanco, F. (2024). Time Course of Recovery From Different Velocity Loss Thresholds and Set Configurations During Full-Squat Training. J Strength Cond Res, 38(2), 221-227. https://doi.org/10.1519/JSC.0000000000004623 

Haff, G. G., Whitley, A., McCoy, L. B., O’Bryant, H. S., Kilgore, J. L., Haff, E. E., . . . Stone, M. H. (2003). Effects of different set configurations on barbell velocity and displacement during a clean pull. J Strength Cond Res, 17(1), 95-103. https://doi.org/10.1519/1533-4287(2003)017<0095:eodsco>2.0.co;2 

Jukic, I., Ramos, A. G., Helms, E. R., McGuigan, M. R., & Tufano, J. J. (2020). Acute Effects of Cluster and Rest Redistribution Set Structures on Mechanical, Metabolic, and Perceptual Fatigue During and After Resistance Training: A Systematic Review and Meta-analysis. Sports Med, 50(12), 2209-2236. https://doi.org/10.1007/s40279-020-01344-2 

Kolind, M. I., Gam, S., Phillip, J. G., Pareja-Blanco, F., Olsen, H. B., Gao, Y., . . . Nielsen, J. L. (2023). Effects of low load exercise with and without blood-flow restriction on microvascular oxygenation, muscle excitability and perceived pain. Eur J Sport Sci, 23(4), 542-551. https://doi.org/10.1080/17461391.2022.2039781 

Larkin, K. A., Macneil, R. G., Dirain, M., Sandesara, B., Manini, T. M., & Buford, T. W. (2012). Blood flow restriction enhances post-resistance exercise angiogenic gene expression. Med Sci Sports Exerc, 44(11), 2077-2083. https://doi.org/10.1249/MSS.0b013e3182625928 

Oliver, J. M., Kreutzer, A., Jenke, S., Phillips, M. D., Mitchell, J. B., & Jones, M. T. (2015). Acute response to cluster sets in trained and untrained men. Eur J Appl Physiol, 115(11), 2383-2393. https://doi.org/10.1007/s00421-015-3216-7 

Pareja-Blanco, F., Villalba-Fernandez, A., Cornejo-Daza, P. J., Sanchez-Valdepenas, J., & Gonzalez-Badillo, J. J. (2019). Time Course of Recovery Following Resistance Exercise with Different Loading Magnitudes and Velocity Loss in the Set. Sports (Basel), 7(3). https://doi.org/10.3390/sports7030059 

Rodriguez-Rosell, D., Yanez-Garcia, J. M., Sanchez-Medina, L., Mora-Custodio, R., & Gonzalez-Badillo, J. J. (2020). Relationship Between Velocity Loss and Repetitions in Reserve in the Bench Press and Back Squat Exercises. J Strength Cond Res, 34(9), 2537-2547. https://doi.org/10.1519/JSC.0000000000002881 

Sanchez-Medina, L., & Gonzalez-Badillo, J. J. (2011). Velocity loss as an indicator of neuromuscular fatigue during resistance training. Med Sci Sports Exerc, 43(9), 1725-1734. https://doi.org/10.1249/MSS.0b013e318213f880 

Sanchez-Valdepeñas, J., Cornejo-Daza, P. J., Rodiles-Guerrero, L., Paez-Maldonado, J. A., Sanchez-Moreno, M., Bachero-Mena, B., . . . Pareja-Blanco, F. (2024). Acute Responses to Different Velocity Loss Thresholds during Squat Exercise with Blood-Flow Restriction in Strength-Trained Men. Sports (Basel), 12(6). https://doi.org/10.3390/sports12060171 Scott, B. R., Loenneke, J. P., Slattery, K. M., & Dascombe, B. J. (2015). Exercise with blood flow restriction: an updated evidence-based approach for enhanced muscular development. Sports Med, 45(3), 313-325. https://doi.org/10.1007/s40279-014-0288-1