I ran my best 10k about 13 years ago in 43m. I've not done a huge amount of running since then due to work stuff and shin-splints. But the last month or so I've felt quite good and done a fair amount of training, not run a 10k yet but I did a 5k in 23m. Was hoping for better. Is there any chance of me beating my pb or basically am I just too old???