The upward phase of an exercise is when the object or weight being moved is ascending. The downward phase of an exercise is when the object or weight being moved is descending. However, this is NOT AWALYS synonymous to concentric and eccentric muscle contractions. Most assume that the upward phase of an exercise is the concentric muscle contraction, and the downward phase is the eccentric muscle contraction. For most exercises, this is true…but not for all exercises. For example:
1️⃣ Barbell Bench Press: when performing the barbell bench press, as the weight is lowered to the chest, this is the downward phase since it is descending towards the ground. The upward phase begins once the barbell begins moving away from the chest. In this example, the downward phase requires an eccentric contraction, and the upward phase involves a concentric contraction.
2️⃣ Lat Pulldown: When the shoulders and arms pull the bar towards the clavicles, this is the downward phase. When the bar travels up towards the pulley, this is the upward phase. In the downward phase, a concentric contraction is needed to pull the weight down towards the clavicles. During the upward phase, the movement is controlled via an eccentric contraction.
Overall, the upward and downward phases are exactly as they sound…when the object or weight being moved is going up and down. Concentric muscle contractions refer to the active shortening of a muscle, where the force a muscle creates is greater than the external force (weight/resistance being lifted). Eccentric muscle contractions involve lengthening of the involved muscles, where the external force (weight/resistance being lifted) is greater than the force being created by the muscles.