Momentum in Resistance Training

There are many ways to develop momentum. The most common technique is using assisting muscle groups to begin the lifting movement — for example, using the back muscles and trunk movement to initiate barbell curls. Although heavier weight loads can be used this way, the target muscle group (the biceps, in this example) actually receives less training stimulus because of the momentum factor.

Another example is bouncing the bar off the chest during the bench press. In addition to the high injury potential, this careless use of momentum reduces the training effect on the target muscle groups (chest, shoulders, and triceps).

While momentum certainly has its place in sporting events, it should play a minor role in weight-training programs. Momentum-assisted lifting gives the appearance of greater muscle strength, but it actually decreases the demand on the target muscle groups and increases stress on the joint structure.

The physics also work against fast training: as the momentum component increases, the muscle-force component decreases — by developing momentum, one can lift heavier loads with less sustained muscle effort. With a barbell curl, torque about the elbow is minimal at the bottom position, and the momentum generated through the rest of the curl reduces the experienced load compared with the static load at later positions; this is especially true during fast (power-training) repetitions but is not so critical with slow movements.

• Momentum is generated mainly by recruiting assisting muscle groups to start the lift.
• Heavier loads become possible, but the target muscle gets LESS stimulus.
• Examples: trunk swing on barbell curls (robs biceps); bouncing the bar off the chest on bench press (robs chest/shoulders/triceps + high injury risk).
• Increases stress on joint structures; gives a false appearance of strength.
• As momentum increases, muscle force decreases.
• Should play only a minor role in weight training (its place is in sport).

• movement-speed — slow controlled lifting is the direct countermeasure to momentum.
• cheat-system — the cheat system deliberately uses momentum to push past the sticking point.
• proper-form — breaking form to recruit momentum increases injury risk.
• tempo — controlling tempo minimizes momentum.
• eccentric-action — momentum is most damaging at the start/finish of the lift.