“Cheating” with momentum while strength training may feel appropriate in the moment, but ultimately you are only cheating yourself out of long-term gains.


As personal trainers, we have the opportunity to bear witness to any number of inappropriate and potentially dangerous weightlifting practices during a typical day at the gym.

Consider for a moment the frequency with which each of us has observed individuals engaged in the following maneuvers:

  • Bouncing up and down while performing weighted squats
  • Pumping quickly through a set of chest presses
  • Swaying of the middle back while doing bicep curls

Such moves are prime offenders of the use of momentum versus pure strength while performing a workout.

Momentum Unwrapped

The term “momentum” is defined by two key aspects: (1) mass, or size, of the exerciser as well as the weight being moved, and (2) velocity, or speed. The larger the exercise participant is, the more weight she is typically capable of lifting. If she proceeds through the lifts too quickly and/or places fewer constraints on her movements during the exercise, the greater are the risks caused by the use of momentum.

For everyday movements, the use of momentum is normal and even adaptive. It is the body’s way of conserving energy, particularly during activities involving running, throwing or pushing movements.

During strength training, however, momentum becomes counterproductive. It decreases the work done, reducing the tension on the muscle and thereby minimizing the effectiveness of the exercise. The danger comes from the athlete failing to realize the hazard of such a practice to the joints and spinal cord. Momentum over time will overload these areas, causing unnecessary “wear and tear.”

Figuring Out The Physics

Newton’s Second Law of Motion is commonly referred to as the Law of Acceleration, which states that a net force on an object will accelerate it, or change its velocity, in proportion to the magnitude of the force and in the same direction as the force. Simply stated, the rate of change in the momentum of a body is proportional to the applied force and takes place in the direction in which the force acts.

During strength training, momentum is additive—it gains strength with each repetition. The tempo of exercise becomes faster, the muscle works less, and the joints and spine work harder. We can help clients optimize strength training and avoid injury by discouraging their use of momentum.

Stop Momentum Before it Starts

The velocity of a contraction refers to the speed at which a muscle contracts and performs a movement. Controlling the speed of a repetition will stop the use of momentum and force the muscles to do the work since slower movements by their very nature will not cause momentum to build. By cueing a client to stop and “squeeze” or “acknowledge” the contraction at the midpoint of the exercise, we can further eliminate the risk of momentum being employed.

Leaving Ego at the Entrance of the Gym

When working with a new or inexperienced individual at the gym, remind him to forget about competing with the other lifters around him. The purpose of his going to the gym may vary from striving to improve his physique to encouraging and facilitating stress release.

Either way, we are there to take care of only one person: The Client. Help him forget about his ego (with regard to how much he can lift, how fast he executes each move, etc.) and coach him to concentrate on himself and his goals/ needs. The long-term safety of his joints, muscles, and tissues needs to be a priority for both parties involved.

It is Not About the Weight Being Lifted

Another factor that contributes to implementing momentum and bad form is the use of excessive weight. Exercises executed with heavy weight accompanied by good form will definitely improve one’s musculature, but excessive weight lifted incorrectly can have adverse consequences. Not only might the lifter experience joint pain; eventually he increases the risk of suffering a muscle/ligament/tendon tear.

The benefits of using lighter weight are threefold:

  1. If the muscle is lifting a weight that is manageable, the risk of injury is negligible.
  2. Lifting a lighter weight allows total and complete control of the exercise.
  3. A lighter weight allows the individual to totally focus on contracting the muscle to the fullest, rather than relying solely on hoisting the weight to complete the repetition.

Guiding the Process

The following 4-step plan will allow us to best serve our clients while allowing them to understand the basics of eliminating the use of momentum in their workouts.

1. Set up. It is our job as trainers to keep our clients’ bodies in the correct spinal/joint alignment before starting an exercise. When placing a client into position, check his alignment – are his spine and joints in neutral position? Are his abdominal muscles pulled in to his spine?

2. Define the start, middle, and end. Every exercise has a start, middle, and end, with the end position being the same as the start position. To prevent swinging and bouncing during each repetition, know where these points are. Treat each point as its own distinct movement instead of one movement blurred together.

3. Contract at the peak. At the midpoint of the repetition, always cue the client to pause and contract the right muscles. Counting to control the rate of contraction – and breathing — back to the start will help the client focus, and stop him from using momentum, thereby allowing the recruitment of more motor units to increase force.

4. Control the speed. Slower repetitions build less momentum than faster ones. Rushing through reps increases the likelihood of relying on momentum. Encourage clients to slow down and practice awareness through each rep.

By understanding the differences between “tempo”, “speed” and “momentum”, we can help our clients ensure a safe and effective workout every time they visit the gym. Gains in physique, muscularity, strength, and aesthetics come together when muscles are placed under tension appropriately. The blending of physics and fun begins with you!


  1. https://personaltrainertoday.com/tweaking-training-tempo-get-results
  2. http://www.ideafit.com/fitness-library/counteracting-momentum-during-exercise-0
  3. https://virtuagym.com/blog/lifestyle/exercise/momentum-time-under-tension-range-of-motion/
  4. https://www.bodybuilding.com/fun/manny1.htm
  5. https://www.quora.com/Is-it-always-bad-to-use-momentum-when-weight-lifting
  6. https://stronglifts.com/consistency-momentum-are-the-keys-to-success/

Cathleen Kronemer

Cathleen Kronemer is an NFPT CEC writer and a member of the NFPT Certification Council Board. Cathleen is an AFAA-Certified Group Exercise Instructor, NSCA-Certified Personal Trainer, ACE-Certified Health Coach, former competitive bodybuilder and freelance writer. She is employed at the Jewish Community Center in St. Louis, MO. Cathleen has been involved in the fitness industry for over three decades. Feel free to contact her at trainhard@kronemer.com. She welcomes your feedback and your comments!