Mistakes. I have made a lot with programming.
I usually thought more was better. How many people are lying on the floor dictates a good workout. Doing a max effort back squat on Monday followed by 150 wall balls for time on Tuesday followed by tempo front squats with 15 minutes as many rounds as possible of 50′ overhead walking lunges, 20 calorie bike and 15 squat cleans on Wednesday was a good leg sequence for that week. And then being surprised why on Thursday, Friday…and Saturday people couldn’t walk up and down stairs. Then I would get frustrated when I would retest strength or energy system pieces the following Monday and see no gains (or even decreases).
Our bodies do a phenomenal job of adapting. But they also can only adapt so far before overtraining starts to become a factor. Overtraining leads to a halt in progress and even injury.
Sequencing, rest, rep schemes are so important. How often you train muscle groups, energy systems, max effort versus dynamic effort matters in order for the body to train, rest and adapt well.
The longer I do this and spend time learning from those that are respected in the field I keep reading the same thing: less is more. Training two energy systems in one session often provides minimal results. Spreading out training of muscle groups with 48-72 hours recovery between sessions provides adequate recovery in order to allow for adaptation. AND, it set you up to improve health markers (like PRs in strength and conditioning, body composition changes, decreases in resting heart rate).
More is just more. Often more leads to a decrease in performance. Training smarter doesn’t mean less intensity. It means adding intensity in appropriate doses.