I just ran my first full and first half this year.My full was 3:22 and my half was 1:34.I used to run 5k in my mid 20's and have a pr of 17.24 i am now 39 and ran a 5k last sat in 19.52 i've been back to running now for about 18 months and i just can't get my speed back is it because im older or can anyone give me some training tips to help.