I have just come back from a 4 km trial and that are my results:
1st km - Pace: 4:14:95 Avg Hr: 163 bpm Max Hr: 183 bpm
2nd km - Pace: 4:44:05 Avg Hr: 178 bpm Max Hr: 182 bpm
3rd km - Pace: 5:16:35 Avg Hr: 166 bpm Max Hr: 171 bpm
4th km - Pace: 4:56:32 Avg Hr: 171 bpm Max Hr: 177 bpm
total: 19:13.3 Min Pace: 4:48/km Avg Hr: 169 bpm Max Hr: 183 bpm
What are you suggest me to do next?