Scientifically speaking, the two phases of any lift are actually referred to as the concentric and eccentric phases of strength training exercise. Concentric – or positive – phases of a lift are the actions or directions of a lift where the muscular tension increases as the muscle shortens. This is the most common focus for gym goers. However, allowing yourself some TLC, paying attention to the eccentric phase of a lift, is important for overall strength development.
An eccentric – negative – phase increases tension as the muscle lengthens. The negative phase of any lift is 40 percent stronger than the concentric phase, despite the fact that this is where any given strength workout fails. This failure prevents you from reaching maximal effort on the concentric phase.
Identifying the two phases can be challenging, but here’s a trick: if you were to drop your weight during an exercise and watch it fall, the direction it is falling is typically the concentric phase.
Incorporating concentric/negative attention to your lifting program can increase and improve strength and performance.