| Been lifting for over a decade now, and gone down the deep rabbit hole on this stuff. Also older. My advice: completely ignore the X by X stuff. Focus on time under tension, form, control and how your body feels. Lifting with a goal to hit numbers causes sloppy form and cheats (and injuries) to just try to hit X reps. Every day is different, how you slept, what you ate, whether you're training fasted, where your muscles are in recovery, and a million other variables. As an example (bragging a bit), as a ~50 year old, 165lb, 5' 7" guy, I'm able to lift 100lb dumbells on flat bench chest press, one in each arm. I can hit around 10-12 reps with that, most of them BS cheat reps where I'm powering with my shoulders. It also causes me all sorts of problems with tendon issues, etc... I find when I do 50-70lb weights, and forget about hitting numbers and just feeling the workout, I get way better results. Fewer injuries, better focus on the muscles I'm targeting, and real progress with strength. It's hard to do, because I'm always comparing my performance with my last workout, trying to compete with myself. I have to constantly remind myself that small things, even a couple inches in variation of form have a massive impact on volume. So, I try to throw out the numbers. I vary my rep speed, vary explosiveness, and try to feel what's hardest to do, and then do that. Basically, what I'm trying to get better at is learning to lift with my muscles, not my ego. |
Beginner lifters don't know what their max potential is and might overtrain by accident (because they are naturally strong and might do more reps to try and get to failure) or might not do enough volume to trigger the musculoskeletal adaptions needed to lift more weight (because they are not naturally strong and might tap out early).
> As an example (bragging a bit), as a ~50 year old, 165lb, 5' 7" guy, I'm able to lift 100lb dumbells on flat bench chest press, one in each arm. I can hit around 10-12 reps with that, most of them BS cheat reps where I'm powering with my shoulders.
I personally never recommend cheating reps.
Bodybuilders do them to localize hypertrophy in specific regions, like the upper pecs or shoulders, to improve physique during competition. Most people aren't bodybuilding though and would not benefit from this style of training.
At best, you're short-changing the development of primary and secondary movers this way in the name of moving more weight (like not engaging the lats enough when you do a bent-elbow pull up).
At worst, the risk of injury goes way up (shoulder blowouts are super duper duper common in bench presses; doubly so for dumbbell bench presses, since there isn't a bar to stabilize your arms).
In my experience, I've found that it's better to go lower in weight and use an assistance exercise and/or increasing rest/recovery time and, if needed, decreasing volume instead of cheating reps when you're stuck.
Anecdotal example. When I was struggling with getting to 225x5x3 on the bench, I dropped back 20%, added weighted dips to my rotation and decreased bench press volume. Dips engage the pectoral and tricep muscles more directly, which contributes to forward progress on bench. I can do 250x3x6 now at around 9.5 RPE.