Why training to heart rate can be soul destroying.

This workout was carried out by attempting to stay within a narrow band of heart rate.

For me when heart rate goes over 150 I am beginning to work that little bit harder. Keeping the heart rate in the 140s enables me to have a workout that is comfortable to achieve but is not a recovery ride.

However the trace shows that keeping the heart rate within my arbitrary parameters displays a power drop off that is quite marked.