Strength training is a fundamental pillar for both injury prevention and performance enhancement in virtually all sports. However, the benefits obtained with this type of training can depend on a multitude of variables such as intensity (e.g., load or speed of execution) and the volume or density of work (e.g., number of sets or repetitions, and duration of rests). In this sense, one of the variables that has received most attention in recent years is the speed of execution.

Several researchers led by Dr. González-Badillo have proposed that to obtain the greatest gains at a neuromuscular level (including greater recruitment of fast fibres and greater improvements in power) it is advisable to perform repetitions at the maximum possible speed, avoiding losing excessive speed during each set. In fact, in a study published in 2011 it was already observed that the loss of speed during strength sets was associated with greater fatigue, both metabolic (greater accumulation of lactate and ammonium) and mechanical (greater loss of jumping).¹ Thus, the authors proposed that it is important to monitor the speed of execution to avoid excessive levels of fatigue. 

Numerous studies have been published in recent years supporting the importance of execution speed in strength training. For example, Dr. Gonzalez-Badillo’s group evaluated the effect of losing more or less speed during each set (i.e., being further or closer to muscle failure) on the adaptations produced by strength training.² To do this, one group of subjects trained in the same way (2 days a week, 3 sets of squat at 70-85%RM with 4 minutes rest) for 8 weeks, but one group performed repetitions until they lost 40% of the speed achieved in the first repetition (closer to muscle failure), while the other group performed repetitions until they lost only 20%. At the end of the training period, the group that had lost less velocity in each set (and therefore performed fewer repetitions) improved their jumping performance more than the other group (9.5 vs 3.5%). In addition, when analysing muscle biopsies, they observed that the proportion of fast fibres (type IIX) decreased in the group that lost more speed in each set. On the other hand, although hypertrophy occurred in both groups, the group that lost 40% velocity during each set increased the quadriceps cross-sectional area to a greater extent than the group that lost 20% (7.7 vs 4.6%, respectively).

The above results support that performing repetitions at the maximum possible speed and finishing the set before losing too much speed (specifically, losing less than 20% with respect to the first repetition) can be an effective and above all more efficient strategy to increase muscle power, although it may decrease muscle hypertrophy. In this sense, another study recently published in Medicine and Science in Sports and Exercise has shown that losing 20% or 40% of speed during each set produces greater hypertrophy than losing 0% or 10%, but on the contrary it is also associated with a worsening of neuromuscular properties (including a worse strength development ratio).³ On the other hand, another study recently published in The Journal of Strength and Conditioning Research has shown no difference in jump or sprint improvements in subjects who trained for 7 weeks by losing 5 or 20% speed during sets, showing that performing fewer repetitions (33% fewer repetitions when losing 5% speed compared to losing 20%) can yield the same gains.⁴

Monitoring the speed of execution during strength training (for example, by using linear encoders, infrared cameras, accelerometers or even mobile applications) is therefore advisable to allow a greater or lesser loss of speed depending on our goals (hypertrophy or neuromuscular improvements). In summary, if the objective is to maximise improvements in strength or power, it will be advisable to perform the concentric part of the exercises at the maximum possible speed and avoid losing speed during the sets, which will also result in more efficient workouts by requiring a lower volume of repetitions. Conversely, if the goal is to increase muscle hypertrophy – at the expense of less improvement or even worse neuromuscular performance – it may be advisable to lose more speed during the set by getting closer to muscle failure.

References

1. Sánchez-Medina L, González-Badillo JJ. Velocity loss as an indicator of neuromuscular fatigue during resistance training. Med Sci Sport Exerc. 2011;43(9):1725–34.
2. Pareja-Blanco F, Rodríguez-Rosell D, Sánchez-Medina L, Sanchis-Moysi J, Dorado C, Mora-Custodio R, et al. Effects of velocity loss during resistance training on athletic performance, strength gains and muscle adaptations. Scand J Med Sci Sport [Internet]. 2016;(1998):1–12.
3. Pareja-Blanco F, Alcazar J, Sánchez-Valdepeñas J, Cornejo-Daza P, Piqueras-Sanchiz F, Mora-Vela R, et al. Velocity Loss as a Critical Variable Determining the Adaptations to Strength Training. Med Sci Sports Exerc. 2020; Feb 7(Epub ahead of print).
4. Galiano C, Pareja-Blanco F, Hidalgo de Mora J, Sáez de Villarreal E. Low-Velocity Loss Induces Similar Strength Gains to Moderate-Velocity Loss During Resistance Training. J Strength Cond Res. 2020;(12):1.