Many coaches use the term “interval” as a catch-all term for different types of workouts that call for periods of faster running separated by easy running. For those of you who aren’t familiar with Daniels’ Running Formula Jack has assigned a very specific meaning and purpose for Interval training. Training at your interval pace is just one of the components on how to train properly for a particular race.

Below we break down everything you need to know about training at your “I” pace. Jack includes some element of Interval training for all race types but more so in our 5k and 10k plans


Purpose:  To improve your aerobic capacity (VO2Max)

Intensity:  Generally in the range of 98-100% of HRmax. Intervals are “hard” but not all-out running by any means. Usually at a pace that you could maintain for about 10-15 minutes in a serious race.

Duration:  It takes about two minutes for you to gear up to functioning at VO2max so the ideal duration of an “Interval” is 3-5 minutes each. The reason not to go past 5-minutes is to prevent anaerobic involvement, which can result in blood-lactate build-up. “I” running should be no more than 8% of your weekly mileage.

Recovery: Keep recovery to very easy jogging and equal to the duration of the interval or slightly less than.

Sample workout:  2 miles easy, 5 x 3 minutes at I pace, 2 miles easy

Now input a recent race result on Jack’s calculator and then click the Training tab to learn your current “I” pace to get started. For instance, if you recently ran 1:50 for a half marathon your “I” pace would be roughly 7:29 per mile.