3-2-1 Intervals

This is a timed session, with intervals marked by a whistle. We do 3 sets of the following pattern, so the session lasts for 30 minutes in total.

1. 3 minutes effort
2. 1 minute walk/jog recovery
3. 2 minutes effort
4. 1 minute walk/jog recovery
5. 1 minute effort
6. 2 minutes walk/jog recovery