4km: The feeling of speed and heart jumping out

Since morning, i have been having monday blues...another reason for it is that i was unable to discipline myself to get out of the comfortable bed in the aircon room for a morning run..... So i decided a run is a MUST tonite.....late afternoon, sky getting dark due to the cumulated clouds....pray and pray that rain will not come (it came yesterday afternoon) Finally, off from work and dashed home to get changed up...out of the door in no time.... decided to do just a 4km run...but maybe a bit faster one.....legs felt hard at first but becos fot he initiate downslope for the 1st 2km, it was easily warmed up....i was already running too fast before i reached the U-turn point..... Second 2km was tough as usual due to the upslope ill the end....i just tried to maintain my effort and push a bit faster to finish it within 10min....my heart was pumping so fast that it seems to jump out soon seldom speed....and dun like speed...i prefer long slow comfortable run...... But this run shows that my legs are ready..no tiredness on the legs going upslopes...only breathless and hard pumped heart.....so my heart and lungs are not ready.....need more run consistently for conditioning..... till the next run......................................................................................... shoes: adizero SN total distance: 4km total time: 20:30min ave speed: 5:08min/km laps: 2km for 10:37@5:18min/km 2km for 09:57@4:57min/km