To continue to grow, your muscles need to be challenged in different ways. One way to vary the stimulus you place on a muscle is to change the “lifting tempo,” or the speed with which you do a rep. You’re probably familiar with super-slow training where you reduce the speed or tempo of a rep to maximize the time the muscle is under tension. At the other end of the spectrum, you can increase the speed and make the movement faster and more explosive, thereby stimulating the muscle in a different way. What role does rep speed play in muscle gains and is one rep speed more effective than another?
What Rep Tempo is Best for Strength and Muscle Hypertrophy?
According to one small study, fast rep speeds may be more effective for building strength than slow reps. In this study a group of young males did 4 sets of bench press, completing 12 reps with each set. One group used a fast rep tempo, completing each rep in 1.5 seconds, while the other used a slow rep speed, finishing a rep in 6 seconds. At the completion of the study, researchers measured one-rep max on the bench press exercise and compared them to values measured before training. How did they fare? Participants who used a fast rep tempo experienced greater strength gains than those who used a slow one – not surprising since a fast rep tempo maximizes recruitment of fast-twitch fibers, those optimized for strength and power.
What about muscle hypertrophy? What’s most important for muscle growth is exposing muscles to progressive overload AND maximizing time under tension. With high-velocity reps, your muscles spend less total time under tension compared to when you slow down the speed of your reps. Because you’re moving the weight quickly and using more momentum, you can use more resistance. This is beneficial for developing strength, but it also comes with a price, less time under tension due to the speed of the movement. For this reason, a fast rep speed works well for developing strength and for increasing power – but slow rep speeds are better for muscle hypertrophy.
Varying the Rep Speed
As you might have guessed, there isn’t a right or wrong rep speed. The rep speed you use will depend upon your short-term and long-term goals. If your primary goal is to become stronger, become more powerful or improve your performance in sports that involve power, fast rep speeds will help you accomplish that. If muscle hypertrophy is your main goal, average rep speed and super-slow training maximize the time your muscles spend under tension, giving your muscles a strong stimulus to grow. Fortunately, you don’t have to choose between the two. Periodizing rep speeds, by doing slow reps during one training cycle and fast, explosive reps during another cycle, will help you avoid a plateau.
One disadvantage of fast rep speeds is it’s easy to get sloppy and completely lose your form when you’re using momentum. The risk for injury is also greater. When you slow down the speed of your reps, you eliminate most of the momentum and force your muscles to do all the work.
Why Fast Reps Should Make Up a Portion of Your Training
With so much focus on losing muscle strength and mass as we age, it’s easy to forget that we also lose power. Research shows lower limb strength declines by between 1 and 2% per year of life between the ages of 65 and 89, while lower limb power declines by 3.5% per year. Plus, experts now point out that it’s a loss of power capability, even more than strength, that causes people to become less functional with age.
How do strength and power differ? Strength refers to how much force you can generate without regard to speed, whereas power equates with how much force you can generate in a given amount of time. One-rep max for squats is a good indicator of lower body strength, but power capabilities are better measured by jump squat performance.
It’s not hard to see why power capabilities are so important for functionality. Getting up from a chair takes lower body strength, but it takes power too. As older adults lose power, tasks like climbing stairs and getting up from a chair become more difficult, leading to loss of functionality and a greater risk for falling. Even if you aren’t older, developing power helps performance in a variety of sports, including volleyball, soccer, and basketball.
If you think about it, power is more applicable to everyday life than strength. Unlike a powerlifter who has unlimited time to lift a heavy weight, in sports, a time element is involved, and strength and speed both matter. Strength training increases the total amount of force your muscles produce, while power training, using fast rep tempos, increases the rate or speed at which you can produce that force.
It’s clear that power development and preservation are important at all stages of life, but fast rep weight training isn’t the only way to boost power capabilities. Plyometric drills that involve explosive movements like jump squats, tuck jumps, burpees, box jumps and hops help to enhance power as do activities like sprinting and ballistic medicine ball throws. These activities should be part of an overall strength and conditioning program designed to improve athletic performance and enhance functional capabilities.
The Bottom Line
Average rep speeds, slow reps, and fast reps all have their place in a resistance training program. Your muscles will benefit most from a variety of rep tempos rather than being subjected to the same rep speed every time you train. Slow training, using slow rep speeds, may be the most advantageous for hypertrophy, but fast and explosive rep speeds are most effective for developing power and strength. Consider your goals when planning your routine, but make sure you’re varying the tempo of your reps.
Strength and Conditioning Research. “Does strength training need to be velocity-specific?”
IDEA Health and Fitness Association. “Power Training For Older Adults”
Int J Exerc Sci 2(2): 131-151, 2009.
Mike Boyle Strength and Conditioning. “Delaying the Loss of Power as a Function of Aging”
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