One rep consists of movement through the full range of an exercise.
For example, in a bench press, lowering the bar to your chest then pushing it back up counts as one repetition.
A rep typically includes two phases:
|Muscles contract (shorten)
|Muscles relax (lengthen)
While both phases of a rep are important for the development of overall strength, the negative phase has been shown to induce greater improvements in muscular size and strength in comparison to the positive phase.
Special rep types
As the name suggests, partial reps involve stopping before completing the full range of motion of an exercise. While partials are not a typical method of training, they can be beneficial for rehabbing injuries, strengthening a certain portion of a lift, prolonging muscular tension, strengthening tendons/joints, etc.
Half, third, or quarter reps, are sometimes used in power training to emphasize speed at a certain portion of a lift. For example, squatting only to a point that mimics a jump produces more specific adaptations to the movement, and may therefore result in a higher vertical jump compared to full range squats.
The stretched portion of an exercise has been found to stimulate muscle growth to a greater extent when compared to the contracted portion. Therefore, performing partial repetitions around the stretched portion of an exercise may be a time-efficient method of training. However, since strength and power adaptations are range-specific, performing only partial reps at the stretched position of an exercise would cause the remaining range to lag behind.
They do not follow the typical definition of a rep as there is no range of motion; they constitute holding a specific position in an exercise. Since strength adaptations are specific to the trained range of motion, performing isometrics can significantly improve one’s ability to hold certain positions in calisthenics, yoga, and even armwrestling.
Slowed eccentric reps
While bodybuilding-style reps typically involve slow, controlled, eccentrics (the easier part of the movement), slowing eccentrics even further (around 6 seconds) can be vastly beneficial for strengthening connective tissue like tendons and ligaments. Such structures have been shown to heal and strengthen better when slow eccentrics or isometrics (holding positions with no movement) are emphasized instead of the concentric portions.
When nearing the end of a set due to fatigue, rep speed decreases and the difficulty of continuation increases exponentially. At a certain point, performing more full range of motion reps without rest becomes physically impossible without assistance either by yourself or another person.
Assisted/forced reps place even further tension on muscle and theoretically increase muscular stimulation. However, one must factor in the increased fatigue and risk injury associated with pushing beyond physical limits.