Hosand Heart Rate Telemetry:

Measuring your heart rate is a key indicator of your body’s response to activity. Essentially your heart rate determines what you are training for; recovery, endurance, sprint etc… As a rough guide your maximum heart rate can be found by subtracting your age from 220.

A rough guide to training zones:
Recovery Training: <70% (of maximum heart rate)
Extensive Endurance: 70 – 80% (of maximum heart rate)
Intensive Endurance: 80 – 90% (of maximum heart rate)
Anaerobic Intervals: >90% (of maximum heart rate)