11.8 & 23.9 at aged 46 is really good, especially if you are now aiming for the 400m!
I'm actually quite jealous; I'm 48, and my decision to sprint again happened in 2020. Stupidly went hell for leather doing hill sprints with no warm-up (what was I thinking?) and straight away strained my groin before I'd even begun. Next to go was the left achilles. So winter of 2020-2021 was jogging on grass, just once a week, with 2 sessions on the exercise bike. I started to pick it up a little in 2020, then strained my left hamstring. That's all healed now, and managed to get on a track once a week, with another session on grass. Now my other achilles is giving me pain!
I was never fast as a youth (12.4 & 25.2 as a 14 yr old) just ok. My aim was always to come back & do the 200m, because the 100 is just so bloody tough, but I'm debating between the 200 or 400 now. Initially I wanted to start at 27 for my first few races and get down to 25 again (and around 56-57 for 400m). With all my injuries I will be happy to break 30 secs!
I'm 181cm tall and 85.5 kg. Despite hitting PBs in the gym, it isn't translating to the track, and I agree with the other poster that if you want to run fast you have to...run! Sounds obvious, but in my head, with my squat PBs, and my power on the bike, I just assumed running would be fine. Nada. Nope. Nah. Nein. Non.
I'm currently on the cusp of "do I stick with this and see it through?" vs "this is battering my body like nothing else, is it worth it?". If I don't see some improvements soon, I'm throwing in the towel. It's a fine balance between enjoying it, and being frustrated (due to injury).
I ran yesterday (speed endurance sesh, 8 x 150m with 2.5min rest) and I have a slight limp today with the sore achilles.