To make progress, you need to stimulate muscles deeply. One set typically cannot recruit all fibers in the muscle. That's why you do more sets, to fatigue some of them, then recruit the rest in subsequent sets.
To gain strength, you need to lift around 70% ... 90% of your 1RM (one-rep-max - the maximum load that allows the complete execution of exactly one repetition). On the lower end of that spectrum, that means 8 rep sets. On the higher end, that means 3 rep sets.
I'd be fine with doing one set of 8 reps at 70% 1RM. But it just doesn't sound right to only do one set of 3 reps, even if it's 90% 1RM. There's no way you're stimulating the whole muscle. Lots of fibers will remain unrecruited, and will not be pushed to improve.
Perhaps you're stimulating the same muscle with several different exercises during the same session, but then you're not really doing "one set".
All this boils down to: you need around 24 ... 25 reps per exercise to really dig into all fibers. Shorter sets = more sets = higher load. Longer sets = fewer sets = lower load.
For whole body training, this strategy leads to 40 ... 60 minutes required per session to stimulate all major muscles. Given 3 sessions per week, that means 2 ... 3 hours per week of weight lifting. That's not excessive by any means.
Basically, I consider all of the above as the gold standard of whole-body strength training for amateurs. Using these principles (and others) I transformed myself from a pencil-neck into the guy who bench presses 100 kg (220 lb).
A better way to look at it is that 1 hard set gets one most of the benefit that is possible from the exercise. An athlete would definitely want to do 2 or 3 sets (or more depending on level of competition, etc.), but an average person just trying to get into shape or maintain shape doesn't. I went from pencil-neck to bench pressing 215 lbs using the one-hard-set method.
Without wanting to sound rude, you were a beginner.
Training programs for beginners are notoriously effective. I could bring a beginner's squat max up by making them walk up hills.
One of the major problems with the scientific literature on weight training is that it tends to take untrained males of college-attending age and then do dippy stuff to them. And then, surprise! The weird training protocol works! The happy researcher concludes that their pet theory is proved.
But as I say, beginners can be trained with almost anything and improved. So one might as well get them used to what they will need to do as an intermediate or advanced trainee and teach them to squat, deadlift, bench, overhead press and (in my case) the snatch and C&J.
Oh, it will work, no doubt, just at less than the ideal speed. Such a minimalist program was espoused by Mike Mentzer, one of the great bodybuilders of past decades. But his views are not considered mainstream.
I agree that a full 24 ... 25 reps (3x8, 8x3, 5x5, etc.) program is not required for maintenance only.
To get into shape... well, I guess it depends on the temperament. I'm inclined to achieve the goal as quickly as possible, then focus on something else. Hence my previous reply.
To make progress, you need to stimulate muscles deeply. One set typically cannot recruit all fibers in the muscle. That's why you do more sets, to fatigue some of them, then recruit the rest in subsequent sets.
To gain strength, you need to lift around 70% ... 90% of your 1RM (one-rep-max - the maximum load that allows the complete execution of exactly one repetition). On the lower end of that spectrum, that means 8 rep sets. On the higher end, that means 3 rep sets.
I'd be fine with doing one set of 8 reps at 70% 1RM. But it just doesn't sound right to only do one set of 3 reps, even if it's 90% 1RM. There's no way you're stimulating the whole muscle. Lots of fibers will remain unrecruited, and will not be pushed to improve.
Perhaps you're stimulating the same muscle with several different exercises during the same session, but then you're not really doing "one set".
All this boils down to: you need around 24 ... 25 reps per exercise to really dig into all fibers. Shorter sets = more sets = higher load. Longer sets = fewer sets = lower load.
For whole body training, this strategy leads to 40 ... 60 minutes required per session to stimulate all major muscles. Given 3 sessions per week, that means 2 ... 3 hours per week of weight lifting. That's not excessive by any means.
Basically, I consider all of the above as the gold standard of whole-body strength training for amateurs. Using these principles (and others) I transformed myself from a pencil-neck into the guy who bench presses 100 kg (220 lb).