A tempo run is a type of training workout that typically lasts for 20 to 30 minutes and is performed at a steady pace equal to about 25 to 35 seconds slower than your 5K race pace.
In more simple terms, the pace you would perform a tempo run at, according to Daniels’ Running Formula by renowned running coach and researcher Jack Daniels, should feel “comfortably hard.” Exercise physiologist and coach Pete Pfitzinger told Runner’s World that if you train with a heart rate monitor a tempo run should be performed at 90% of your maximum heart rate.
Tempo runs are sometimes referred to as anaerobic threshold (AT) or lactate-threshold workouts because the purpose of the workout is to help train your body to use the oxygen that’s delivered to your muscles more efficiently by increasing your lactate threshold— or the point at which your body is no longer able to clear lactate and your muscles begin to fatigue.
The most important aspect of a tempo run is making sure to consistently maintain your specified pace for the entire duration of the workout. Keep in mind that hills, rough terrain and wind are all factors that can hinder your ability to keep a consistent pace so these workouts are best performed on a flat route on non-windy days.
Tempo runs are most beneficial for athletes who cover distances of 15K or more because the physiological developments achieved will be most advantageous for competing in endurance events.