Rest Quality and quantity of rest are a huge factor in training frequency
Quality rest increases your ability to train more frequently. I’m defining quality and quantity in two principal ways: your level of activity on your rest days, and hours of sleep per night. If you shovel tar for half a day on your rest day then it wasn’t especially effective rest.
Similarly, if you sleep only 5-6 hours per night then you also didn’t rest very effectively. The most effective rest is lack of prolonged or intense physical activity during the day plus 8.5-9 consecutive hours of sleep per night. Yes, that’s asking a lot of the typical American schedule. Guess what, your body doesn’t give a damn. Less/low quality rest means training less often.
More/high quality rest means you can train more often without overtraining or incurring overuse injuries.