I've recently been running a hill loop of 1350m comprised of 100m flat at the bottom, 600m uphill with 45 feet of gain, 100m flat at the top, 550m downhill with 45 feet elevation loss. A recent session I had on this loop was 6 laps with 60s jog between each rep, at a goal pace of 5:10/mile. The session went well, averaging 5:03/mile for the reps, and afterwards I had a few thoughts on using hills in place of flat terrain for lactate threshold work like this.
As I understand it, lactate threshold pace is usually suggested as the pace that you can run all out for 1 hour, or for most sub-elite to elite runners half marathon race pace. Training lactate threshold involves getting right up on the line of your limit to produce and clear lactate effectively and trying to become as efficient as possible at this pace.
My question is then, would using a hill loop like this be as beneficial, or even more beneficial? For this example I ran the first 800m (100m flat, 600m uphill, 100m flat) in between 2:35-2:40 (5:10-5:20/mile) each time, then finishing the next 550m downhill to complete the reps starting at 5:13/mile working down to 4:52/mile for the last rep.
I am theorizing that running uphill at the same pace as lactate threshold, 5:10/mile, would produce more blood lactate than running the same pace on flat terrain. With this higher accumulation of lactate due to running uphill the body needs to clear it. After 800m, coming back downhill I am able to run at a faster pace, say 5:00/mile, while maintaining the same effort. From a mechanical standpoint, is the body then able to clear the lactate while running at a faster pace?