Is there value in doing 20-25x 400m w/ 20s rest at 'threshold effort' as a stand alone session?

do 20-25 at threshold but jog the 100m in between reps. High quality workout.

KAV wrote:

Same for the number of reps.... 20-25x too many unless you run 64"s

This is a good point. Kenyans do this workout a lot too, however, in the timed Fartlek format. 20-25 x one minute on and one minute off is a very similar workout.

As others have said this an excellent workout to get high volume threshold. Along with improving economy at the faster 5k pace. More Americans need to drop the 20 minute threshold for workouts like this.

none of this is new. Grete Waitz was doing 20x 300m (15sec recovery) back in the mid- 1970's. Didn't call it Threshold back then, but that is what is was really. extrapolate that out to 400 - 20sec recovery. But the point of it being threshold isn't the intensity per se, but the lactate level incurred. Breaking this into sets changes the value of the session. Nothing wrong with doing that, but it isn't the same thing.