EccentricEccentric phase · Negative
The phase of a lift where the muscle lengthens under load, the 'lowering' part.
The eccentric phase is the part of a rep where the muscle produces force while lengthening: lowering into a squat, letting the bar down to your chest, the descent of a curl. Lifters call it the negative, and it is the half of the rep most likely to be thrown away.
Muscles are stronger eccentrically than concentrically, typically by a meaningful margin, which is why you can lower a weight you cannot press and why a training partner helping you up on the last rep is not cheating so much as changing the exercise.
It matters for growth. A meta-analysis comparing eccentric with concentric training in healthy adults found eccentric work produced greater gains in strength and muscle mass, with the advantage clearest when the eccentric was performed at high intensity. The practical reading is not eccentric only training, but that the lowering phase deserves the load and the attention.
It is also the main driver of next day soreness, because lengthening under load causes most of the mechanical disruption behind DOMS. That fades fast with exposure, which is why a new eccentric emphasis wrecks you once and then stops.
Tendons respond to it particularly well, and loading programmes for Achilles and patellar tendinopathy were built around eccentric work for years. Later trials found heavy slow resistance, which loads both phases under control, works at least as well, so the current reading is that load and control matter more than isolating the lowering.
The practical version is undramatic: take roughly two seconds to lower, keep tension rather than collapsing into the bottom, and stop treating the descent as the rest between reps. Extreme protocols with supramaximal loads need a partner and cost a great deal of recovery for a small return.
In practice, control the eccentric on every set, use our one rep max calculator to keep the loads honest, and expect a few sore days when you first start doing it properly.
Sources
- Roig M, et al. The effects of eccentric versus concentric resistance training on muscle strength and mass in healthy adults: a systematic review with meta-analysis. Br J Sports Med 2009;43:556-568
- Beyer R, et al. Heavy Slow Resistance Versus Eccentric Training as Treatment for Achilles Tendinopathy: a randomized controlled trial. Am J Sports Med 2015;43:1704-1711