Bar none, the best form of progressive overload is adding weight to the bar. You really can't go wrong with strong. But once you've established a good baseline of strength and can consider yourself to be pretty strong – and this means different things to different people depending on whom you ask – the rules change a bit.
While "just get stronger" makes for a good tagline and even a good game plan in the beginning, you can't just keep adding weight to the bar ad finitum without stalling out or getting hurt. This is especially true for more experienced lifters with more mileage on their joints or lifters with previous injuries. So at some point along the way – and again, this point will differ from lifter to lifter – it becomes prudent to find other ways to up the ante beyond just trying to add weight to the bar every time you hit the gym.
Elevator reps serve as a great way to challenge yourself and build muscle with relatively light weights. You can use elevator reps with lot of different exercises, but the basic concept is to start each rep by performing a half rep, then a three-quarter rep, and then a full rep all in succession, back-to-back-to-back. That counts as one rep. Then repeat the sequence in that order for the desired number of reps. The key is to figure out if you should start the rep from the top position or the bottom position, and that depends on the exercise in question. Some exercises are harder in the bottom position while others are harder in the top position. Figure out which portion of the rep is hardest for the exercise in question and start there. The other key is to make sure to wear your big boy panties because this stuff ain't for sissies.
Front squat down, come halfway back up, go down again, then come three-quarters of the way up, go down again, and come all the way back up. If that sounds hellacious, it most certainly is – and that's just one rep. Now repeat for the desired number of reps. I like to use a box to serve as a depth gauge, but that's just personal preference. If you forego the box, make sure you don't start cutting the squats too high as the set goes on and your quads start screaming at you.
Interestingly, I generally don't do heavy back squats because they piss off my knees and back, but I'm okay using elevator reps because the weight is significantly lighter than I'd normally use for squats. So these may be an option for those who love back squatting but find that heavy squats bug your lower back or knees. I recommend keeping squats in the 3-8 rep range, meaning 3-8 elevator reps.
Elevator reps work really well for Bulgarian split squats as well, especially for people who don't feel comfortable using a lot of weight on single leg work or for people who find that heavy Bulgarian split squats aggravate their knees. Just like with regular squats, squat down, come halfway back up, go down again, then come three-quarters of the way up, go down again, and come all the way back up.
I've found that these can feel awkward and uncomfortable in lower rep ranges, so I recommend working in the 6-8 range. You won't be able to handle nearly as much weight as you'd normally use for regular Bulgarian split squats, but trust me, you won't need it. For people without a lot of experience with single-leg work, bodyweight alone may suffice at first. Your quads are going to hate you, but in a good way. I guarantee that anyone who thinks Bulgarian split squats are a sissy exercise will be singing a different tune after trying just a few sets of these.
First pull yourself halfway up and lower back down. Then pull three-quarters of the way up and lower back down. Then pull all the way and lower back down. That's one rep. If you have rings – which I highly recommend for chin-ups – you can also switch grips throughout the set to take advantage of the slight differences that each grip provides. I like to a use a pronated grip for the half rep, a neutral grip for the three-quarter grip, and a supinated grip for the full rep. If you don't have rings, a regular chin-up bar will work too, and you can use whichever grip you prefer, or better yet, switch grips from set to set.
I recommend staying in the 3-5 rep range here and making sure to do controlled reps with good form because otherwise you tend to start swinging and it disrupts the rhythm of the set. If you prefer lat pulldowns to chin-ups for whatever reason, that's fine too, and you could use slightly higher rep ranges if you want since swinging won't be an issue.
Elevator reps work with most pressing variations including bench presses and overhead presses with both dumbbells and barbells. Whichever type of pressing you choose, start from the bottom position and press halfway up. Then come back down and press three-quarters of the way up. Then come back down again and press all the way up to lockout. I recommend working in the 4-8 rep range for pressing exercises.
Lateral raises are different from the previous exercises in that the top position is harder than the bottom position, so you want to start from the top and work down rather than vice versa. Start by raising the dumbbells until your arms are approximately parallel to the floor. From there, lower halfway down and then return to the top position. Next, lower three-quarters of the way down and then return to the top position. Lastly, lower the dumbbells all the way down to your sides and then raise them back up to the starting position. Perform the reps continuously and try to keep your arms straight or almost straight throughout the set. Six to ten of these work really well at the end of an upper body workout to leave you with one hell of an awesome pump.
These can be done either lying on a bench or on the floor, though using a bench allows for a greater range of motion, of course. Either way, start with your hands behind your head and lift the bar halfway up until your forearms are approximately parallel to the floor. Next, lower back down to the start position and then lift three-quarters of the way up. Lower back down to the starting position and then come all the way up. I recommend keeping these in the 6-8 rep range as lower rep ranges can wreak havoc on the elbows. You won't be able to handle much weight on these so your ego may take a slight hit at first, but if you can get over your narcissistic pain, you'll find it's a great way to hit the triceps.
This is just a smattering of exercises you can use elevator reps with so get creative and apply the idea to your personal favorite exercises. Elevator reps work best at the end of a workout after you've done your heavy lifting for the day or on days where your body isn't feeling up to crushing heavy weight but you still want to get a good training effect. They can also be useful as a way to get stubborn body parts to start growing again by introducing a new stimulus. Don't ditch the heavy stuff entirely as getting strong is and always will be the name of the game, but the more tools you have in your toolbox, the better off you'll be in the long run.