Fast Reps vs Slow Reps: What Science Says About Speed of Movement

Fast reps vs slow reps: which one builds strength without raising injury risk? In this final installment of the Principles of Exercise Design Series, Amy Hudson and Dr. James Fisher break down one of the most misunderstood topics in training: speed of movement. They unpack what really matters when it comes to fast reps vs slow reps, why intent is more important than rushing the weight, and how smart tempo choices can improve strength without increasing injury risk. Tune in to hear how rethinking speed of movement can completely change the way you train.

• Amy and Dr. Fisher explain the mechanics of speed of movement in each phase of a lift. The concentric phase is when the muscle shortens and moves the weight away from the body. The eccentric phase is the controlled return, when the muscle lengthens as the weight comes back.
• Dr. Fisher explains why speed of movement is often misunderstood. Most people can't accurately tell how fast they're moving during normal exercises. That's why they rely more on tempo and control.
• Dr. Fisher reveals how isokinetic Exobotics devices measure exact distance and exact velocity throughout the lift.
• Amy and Dr. Fisher explain why moving fast is not required to produce power. The body responds to effort and tension, not reckless speed. This is a key shift many people miss when training without a personal trainer.
• Dr. Fisher covers what the research really says about rep speed and muscle growth. Studies show no difference in hypertrophy whether reps are performed quickly or slowly. That finding challenges a lot of outdated gym myths.
• Dr. Fisher reveals why slower lifting can be the smarter option for most people. You still get the same strength, muscle, and health benefits. The difference is reduced stress on joints and connective tissue.
• Learn how resistance training supports overall health beyond just muscle size. Benefits like myokine release, metabolism, and energy expenditure occur regardless of rep speed. This reinforces why control matters more than rushing reps.
• Why resistance training should never increase injury risk. Amy emphasizes that exercise is meant to improve health, not compromise it. If training causes injury, it's moving in the wrong direction.
• Amy explains why exercise should always leave you more capable than before. Training should enhance function, not reduce it.
• Dr. Fisher explains how speed of movement can vary depending on the exercise being performed. Different movements may call for different tempos to maintain tension.
• Amy explains how personal trainers guide clients using clear tempo prescriptions. A coach can say four seconds up, six seconds down, and explain exactly why. That clarity improves safety, effectiveness, and motivation in strength training sessions.

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