re: Help me optimize my split please.

In my mid-40s and mostly use a 4-day 531 schedule but no matter what plan I use I found I have diminishing returns on my workouts after lifting more than 3 days in a row. I know everyone is different, but this wasn't an issue when I was younger. You don't need to take a true rest day, if I have a week where my schedule only allows me 4 straight days to get it in, I will double up on day 2, then program a mobility day with very light lifting and a maybe a long row on day 3, then finish up day 4 with my normal planned workout.

If I try to power through by Day 4, no matter what main lift or bodypart I'm focusing on, I'm not as strong and worse, less focused. I also find this approach keeps me healthier, I haven't hurt or tweaked anything during workouts in a long time. That might also be a focus on better form and mobility, but it all adds up.