Two-A-Day Runs

An exercise physiologist I follow on Twitter is Stephen Seiler, who does research on the effects of polarized training with endurance athletes. Seiler's research points to a ratio of 80 percent low intensity coupled with 20 percent high intensity lead to optimal performance gains. Awhile back, Seiler came out with 12 "Experimental Challenges" for Recreational / Amateur Endurance Athletes in 2019 (pictured).

Seiler's #3 Experimental Challenge is:
3. Complete a 45-60 minute morning training session in zone 1. Then, come back and repeat the same exact session in the evening. How do they compare? (Bonus experiment: compare this with doing the same total duration as one session.)

Reaction After Completing this Challenge
I haven't done two runs in a single day for a few years. After deciding to do it, the novelty of a new challenge motivated me and I came into this challenge excited. I did two 60 minute runs, one in the morning and the other at lunch (not the evening like Seiler outlined).

I had about the same level of fatigue after completing each run.

Compared to one 120 minute run, I noticed less muscle stiffness (?neuromuscular fatigue?) doing two 60-minute runs. After a 120 minute run, it's a real challenge doing toe touches and single-leg toe touches. However, with two 60-minute runs, I had greater flexibility doing these movements after each run.

Thanks for reading! Let me know how this challenge worked for you, if you give it a try.



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