| Christina McLoughlin
What is better for Strength? Intentionally Fast or Slow Repetitions?
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The intention to move fast or slow during repetitions has a big influence on force production and therefore strength adaptation. There have been many training studies, blog posts and even YouTube videos attempting to answer this question while struggling to find objective scientific support. I recently had a Systematic Review and Meta-Analysis published in the journal ‘Sports Medicine’ to investigate what the research says about intentionally fast and slow repetitions on gains in strength. A Systematic Review collates a series of studies based on specific inclusionary criteria and presents their collective methodologies, results and quality. While a Meta-Analysis analyses the results (strength outcomes in this case) statistically to see if there are significant differences between two interventions.
We found 15 studies that manipulated movement velocity with intensity (%1RM) and volume (same sets and repetitions within studies) controlled with study populations varying in training status and age. Together, all studies showed no difference in gains in strength when repetitions were performed intentionally fast or slow. Therefore, repetition speed is not a major acute resistance training variable to increase strength, at a particular amount of volume. This finding was irrespective of age and training status. However, we did find a trend for faster resistance training to be slightly better than slower resistance training at 60%-79% 1RM.
Intending to move as fast as possible: The most important aspect of movement velocity?
Almost all coaches say it, ‘on the up phase, move the barbell as fast as you can’. Why do we say it, what is the rationale behind it? This idea goes back to 1993 when Professor David Behm and Emeritus Professor Digby Sale published the most cited piece of work in this field, ‘Intended rather than actual movement velocity determines velocity-specific training response’. An elegantly designed study, participants trained their calf muscles on one leg in an apparatus which allowed rapid movements as well as resistance so high that no movement could occur (known as isometric). One group performed rapid calf raises against a moderate load while another group also performed rapid calf raises but were restrained so the resultant movement was isometric. This experiment allowed the central nervous system to behave similarly when attempting to move an object as fast as possible, whether there was movement in the object or not. All participants performed 5 sets of 10 maximal repetitions either with the rapid movement or the isometric movement.
What they found was that both groups exhibited the same strength response (as measured by isokinetic torque at varying velocities). They concluded that the principal stimuli for the high-velocity strength response are the repeated attempts to perform explosive contractions along with a high rate of force development. Many other training studies since, especially from a Spanish research group led by Dr. Juan Jose Gonzalez-Badillo (research profile here), have taken this concept and performed training studies manipulating the squat and bench press, movements of great importance to Powerlifters. Their findings indicate that when movement velocity was intentionally fast, it lead to a 43.6% greater increase in bench press strength (Gonzalez-Badillo et al., 2014) and a 45.8% greater increase in squat strength (Pareja-Blanco et al., 2014) as compared to an intentionally slow velocity. Dr. Gonzalez-Badillo attributed the superior increases in strength to neurological contributions. These are; the increased activation of working muscles, higher forces attained in each repetition in the fast group, increased drive to the muscle from the brain, changes in motor unit recruitment thresholds and frequency of motor unit firing (known as rate coding) (Folland et al., 2007). Acutely, when the intention is to move is as high as possible, high threshold motor units (fast-twitch muscle fibres) will be activated, regardless of load (to some extent). Motor units will then start to drop off as fatigue develops (if the intention to move is as high as possible throughout the set) (Sale, 1987).
Check out the result when you train fast. This is Idalberto Aranda (Cuba, -77kg) squatting 280kg / 617lb so fast that the bar clears his head and hits the floor. 280kg is 19.5kg above the current IPF world record in the -74kg class (as of January 2017). In weightlifting, you must lift with the highest movement intention and this results in some incredibly powerful and strong athletes, China are the best at this in the current era.
In Powerlifting, speed in competition is less of a concern, but the faster you are, the less time-under-tension there is in a single lift which reduces fatigue experienced between attempts. Lower amounts of fatigue means you are more recovered for the next attempt. The third attempt is what this spared energy is for. SBD athlete Ray Williams (USA) and Jezza Uepa (Nauru) are the best example of this.
Why slower velocities also increase strength.
Training with an intentionally slow velocity was popularised by founder of Nautilus exercise equipment, Arthur Jones. Jones believed that slow and controlled cadences are superior as they reduce momentum, increase muscle time-under-tension and increase metabolic stress. The increase in metabolic stress (i.e. fatigue experienced) and muscle tension have been proposed as important factors when attempting to increase muscular size.
Example of an Arthur Jones training philosophy:
An increased time-under-tension caused by slower velocities causes a high muscular tension, higher amounts of metabolic stress in active fibres leading to greater muscle damage (in fast-twitch fibres which are more susceptible to increasing in size). This damage activates and mobilises satellite cells to the muscle that is damaged and signals it to grow. The longer time-under-tension also increases muscle protein synthesis rates which increases growth potential, this process is optimised when protein is ingested during this period. The veins around the worked area are also compressed during fatiguing contractions which occludes blood flow and accelerates the metabolic stress response (Folland et al., 2007).
All of the mechanisms above are related to the increase in muscle size, known as hypertrophy. It is extremely well known that a muscle that is larger in terms of cross-sectional area can produce more force than one that is smaller. This premise is the reason why Powerlifting competitions are divided into weight classes, bigger people can produce larger forces and are therefore at an advantage over smaller lifters. However, muscle size does not perfectly correlate to strength, especially dynamic strength, this is called specific tension or muscle quality (force per cm2 of muscle), a topic for another day.
My opinion on movement velocity for strength gain, specifically in Powerlifters.
You can see above that the increase in strength can occur through many mechanisms, but two stand out, neurological and morphological (hypertrophy). Our review has a great line in it and it states, “The mean change in muscle hypertrophy across these studies favoured moderate-slow compared to fast training (6.2 vs. 2.8%, respectively), which provides some support for the conclusion that improvements in dynamic muscular strength for each condition may have resulted through different mechanisms.” This suggests that slow velocities favour the increase in hypertrophy, while fast velocities favour the improvement in the neurological contributions to strength (muscle activation etc.).
In my opinion, both fast and slow velocities can be used effectively to increase strength, however, manipulating intended velocities must be a lower priority to volume and intensity. Volume and intensity provide the largest influence in program design to affect training adaptation, any adaptation. In annual plans (vital in training theory and periodisation), intentionally slow training is best used when training is at its least specific, off-season and general preparation phases. In Powerlifting competition, lifts are performed with heavy load and with maximal intent, therefore intentionally fast movements are preferred as training moves into its most specific phases, specific preparation and competition phases.
I use intentionally slow training with accessory exercises targeting muscle mass with a 4 second eccentric and a 2 second concentric, as recommended by Arthur Jones, and it works well for most people. I also use intentionally slow training with competition movements but only on the eccentric to train control and stability as well as increase time-under-tension which has been shown to increase muscle mass and strength in the biceps (Assis-Pereira et al., 2016). When in competition phases, I recommend intentionally fast movement velocities at heavy and lighter loads. Heavy loads for skill practice mainly, lighter loads for the accumulation of volume under fatiguing conditions and building speed under non-fatiguing conditions.
Until next time, train hard, train smart and dominate on the platform.
Tim Davies – Team PB Powerlifting
PhD Candidate - University of Sydney
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