Concentric Muscle Movement

The lifting phase of an exercise, when the muscle shortens or contracts. For example, When a weightlifter lifts the weight in a bench press, pressing it from the chest to the lock-out position, that's the concentric, or ""positive,"" phase of the exercise.

done as the muscle contracts; "concentric strength" is the weight that can be lifted working against gravity (that's what people usually think of as 'weightlifting')