Do 4 to 12 Minutes of Hard Sustained Endurance Work

Include a middle-ground endurance session where you sustain hard work for roughly 4 to 12 minutes at around 80% effort rather than true max. Example structures included 2 minutes hard with 2 minutes rest done twice, mile repeats, or 800-meter repeats. Use about a 1:1 work-to-rest ratio for these hard endurance intervals.