The opening session of the 12 weeks is to activate the required muscle groups used when running. During the 20 minutes block focus on the correct running technique - take note of the Steps per Minutes (SPM).
Critical Speed (CS) represents the pace that can be sustained for 30 minutes. Once the 30 minute test has been completed, followed the guide in the handbook to establish your training zones.
A general pacing guide is to start 40 bpm under your max heart rate then build throughout.
A good measure of improvement is to compete a 5 km before and after the training programme. Completing the local park run would be a tremendous way of completing today's session.
The theme for the next few weeks is largely about accumulating training volume to build an endurance. Similarly, today's workout, is aerobic in nature.
A recovery style run to enhance adaptations made. Effort level low zone 2/1. If preferred the workout can be a 30 minute walk of light intensity (zone 1).
Same theme to last Sunday. Endurance runs increase in duration over time to improve exercise capacity (the amount of exercise that can be completed without over training).
A shorter duration, but a higher intensity. Make sure to take note of the SPM as this increases proportionally with speed.