You've probably heard of accentuated eccentric loading. And you may have thought, "Yeah, that's just a fancy term for negative training – lowering a weight slowly." Well, yes and no. It's actually a strategy where you increase resistance during the eccentric (negative) phase of each rep. You do it by mechanically altering an exercise mid-rep.
For example, do a dumbbell bench press on the way up (concentric phase), then transition smoothly into a dumbbell chest flye on the way down (eccentric phase).
You can also do the concentric half of a machine exercise with two limbs (bilaterally), then do the eccentric with one limb (unilaterally). For example, do the "up" portion of a leg extension with both legs, remove one leg at the top, then lower the weight with just that remaining leg.
You can increase the workload on each set and make it easier to hit the stress thresholds necessary to stimulate meaningful adaptation. You can experience similar or greater strength gains with accentuated eccentric loading if programmed appropriately than with standard loading parameters (1, 2). These gains probably come from neurological adaptations.
Whenever you're training at a really high intensity and producing a large amount of force, you'll recruit a ton of motor units and fire them pretty quickly (3). When comparing this style of training to standard training methods, the amount of time your muscles spend contracting at a high intensity is far greater, meaning tons of motor units will fire quickly for a longer period of time. You'll end up feeling a bit more fatigued, but it'll trigger some awesome strength gains.
Let's go over some other exercise pairings, then I'll break down the details.
There are plenty of ways you can pair exercises together when performing accentuated eccentrics, but these are easy to do and very effective.
Why not the deadlift? With supramaximal loads, the torque it places on your lumbar spine isn't favorable. It's best to use accentuated eccentric loading to improve the strength of muscles involved in producing this movement pattern more indirectly.
The best time to use this sort of training is when you've been stuck or when you're at the beginning of a training cycle and well-rested. Otherwise, the extra training stress this method adds can lead to excess fatigue and reduce training quality later on in your training cycle. Use heavy accentuated eccentric loading for 3 weeks at a time, and skip it if you're a newbie.