Time to tempo

Through the festive period of Lunar New Year, I did some tempo runs after my son advise me to trry after reading the triathlon magazine. Wow, what a surprise. While I was doing good for 10km comfortably hittin gslightly over an hour, my short runs are actually in pretty bad shape. It was the other way around 5 years ago. I used to run under 12 mins for 2.4km. But now, I felt like dying just doing 250m and 400m sprints. My breath was running out, my legs quickly became dead weight and I cannot pump my arms adequately. At this moment, my quads still hurts. I think I better do the tempo thingy to take care of parts that I have neglected. I also found out that my lung capacity or technique to breath in burst mode has degraded. My first 400m dash was 100sec, rest 2 days, the next try became 97 sec. On both occassions, I tried to do a second burst run after getting my pulse rate down but the repeat attempts end up being aborted, legs/quads yielded. Nice to discover the things I lost ... time to get it back.