5x 1km – 2min recovery Vo2max Zone 5

3km (15-20min) warm-up

5x 1km (~3-5min) @ 10km – 5km Pace (Zone 5/6) | 2min recovery

2-3km (10-15min) cool down

Many scientists believe that the accumulation of training time at VO2max, or at velocities associated with VO2max (vVO2max), is likely to be the most effective training stimulus for improving VO2max. Training at VO2max intensities induces many favourable aerobic responses, including increases in cardiac output, aerobic enzymes, mitochondrial function, and respiratory capacity. 

If your 1km intervals take longer 5min, use 5min instead of 1km and work closer to 100% than 110% of your threshold.