I feel fortunate to have gone through many different phases of training. Bodybuilding, Crossfit, HIT, running, kettlebells, etc., and each phase has taught me different things about training, good and bad.
I currently have many students who take group classes at my facility so it was important to give them simple instructions to achieve their goals in the best way possible.
I realized along the way in my own training that lifting as heavy as possible, while staying as fresh as possible, really does the trick for almost anyone--and I think this is a fact that is sometimes forgotten by many coaches. I can't physically stand over each of my students and tell them to stop when I feel they've done the "perfect" amount of reps. Not only that, but that perfect number of reps is going to change from set to set.
I think that having set reps as a goal can be a good thing, but it can also force people into reps they shouldn't even be attempting.
You can plan to do a set of 5, stop at 4 reps because you want your body mechanics to be solid. You'll still be a good person if you don't do 5 reps--and what's wrong with taking a break and coming back for another set? You have nothing to lose and everything to gain.
My students constantly were asking me how many reps to do--and my classic response used to be 5-8 or 3-5 or whatever matched what I had planned. But of course, they would start out with a set of 8 and their last set they would FORCE a set of 6 well beyond their own ability, which would contribute to bad mechanics, breathing, tension, squinty-face etc. Giving them a set number didn't work except as a jumping off point--it was incomplete instruction.
This is how the 80% rule came about.
My classes run similar to my own training (because I believe what I do works best, so I have my students do the same, even in a group setting), and we try to superset a pair of unrelated strength exercises back to back with a rest after the 2nd exercise (i.e. pullup+front squat, or Press+deadlift).
Now whenever they ask me how many reps, I will simply say "80 percent."
What does that mean? If you think you can do 5, only do 4. If you think you can do 10, just do 8. 80% effort.
What I saw was a lot more sets, and a lot more competence in the movements--and a lot more strength.
80% doesn't mean light, we still lift heavy and most w at this point are swinging 40 kilos 2 handed for reps as a frame of reference.
As far as instruction goes, I will still give a guideline or a qualifier depending on the drill "If you get 10 reps, go heavier" or "Aim for around 5 reps."
Occasionally I will go as high as 90% effort for a set but 80% is typically that "sweet spot."
This rule doesn't necessarily apply for a PR lift for a single or for conditioning, but if you can communicate the essence of the 80% rule to your students, I can guarantee you see a major paradigm shift in their training.
So the 80% rule serves as a terrific training philosophy when training groups due to the logistics, but also prevents injury, allowing for greater strength and better movement. This is, of course, the goal to begin with.
So how do you implement it? Couldn’t be simpler, that’s the key.
Take two exercises that don’t affect each other as above. Let’s say press and deadlift for now. Keep an eye on the clock and practice sets of 80% on both exercises for a while. 10 minutes, 15 minutes, whatever feels "right."
Shoot for somewhere between 3 and 8 reps depending on the exercise (of course it is absolutely acceptable to do a heavy single if you feel up to it!). Keep yourself honest and work on some mobility after the second exercise. Could put a hip flexor stretch here.
So it would look like this:
Press: 80%
Deadlift: 80%
Hip flexor stretch (rest)
After 10-15 minutes of good solid strength practice—don’t worry you’ll sweat too—move on to another superset.
Pullup: 80%
Front Squat: 80%
Thoracic Spine Mobilizations (rest)
Throw in a get-up or two for your warm up and some swings for a finisher and you have a solid program that can vary in intensity based on how you feel that day. This is a very good thing.
Don’t get caught up in each set, if it feels too hard, just stop before you even get to that "bad rep" and come back to it after you’ve rested a minute. You’ll be better for it.
Enjoy.