Muscles respond favorably when they're placed under continuous tension with no resting phases during the rep. Maintaining continuous tension can be achieved in several ways:
- By avoiding rest periods at the top or bottom of an exercise.
- By avoiding the top range of motion during certain movements.
- By minimizing momentum – excessive momentum can cause a considerable deceleration phase at the top of a movement, characterized by decreased muscle activation.
Research supports that lifting with continuous tension can provide a potent stimulus for muscular hypertrophy, even when relatively light loads are used (Tanimoto et al., 2008). The true benefit probably has less to do with reduced momentum and more to do with an acute restriction of circulation to the working muscles.
Repetitive muscular contractions cause a compression of blood vessels, impeding both inflow and outflow during exercise and creating a hypoxic intramuscular environment. There's evidence that the hypoxic effect mediates a hypertrophic response, conceivably by the buildup of metabolites and reduction in pH levels associated with such training.
In combination, these factors are believed to enhance muscular growth through various mechanisms including increased fiber recruitment, acute elevations in anabolic hormones, alterations in myokines, production of reactive oxygen species, and/or cell swelling (the pump).
When To Use Continuous Tension
When performing the big basic lifts such as squats, deadlifts, and bench presses, focus on lifting big weights, using good form, and setting PR's. Go ahead and rest at the top or bottom of the movement if need-be, take advantage of increased momentum when appropriate, and make sure you use a full range of motion.
However, for more targeted movements, use continuous tension. Think of a piston continuously moving up and down with no built-in rest periods – that's what you want your reps to look like.
For many exercises, using partial reps merges well with continuous tension as some movements lead to a complete drop-off of joint torque and muscle activation in the targeted region. For example, the top of a chest flye or dumbbell pullover fails to place adequate tension on the targeted musculature. Therefore, partial reps that only rise two-thirds of the way up may be ideal for these movements. It allows for more consistent tension on the muscles.
When performing movements such as chest flyes, pullovers, hip thrusts, and certain types of curls and triceps extensions, focus on keeping continuous tension on the muscle. Don't rely on momentum, don't be afraid to limit range of motion, and simply squeeze your muscles against resistance.