This is a great discussion...personally, I have become more objective to understand the role of training paces in producing the most effective training effect for race preparation. I concluded that the best marathon training for me blends the two methods outlined. I am not offering anything new, just what worked for me especially for the time crunched family, working individuals (which is many of us). I am not a high mileage guy, typically only peaking around 60 miles in a week, but the majority of the weeks are 50-55mile range. I value harder days/easy recovery days in general when training, but the harder days need to make sense in terms of what training stimulus you need for a goal race. If you train for a 5k, VO2 max is more important, but for marathons, running tempos and longer fartleks with HMP-10k efforts and faster recovery rest periods make more sense, which I would run on Tuesdays. For most Wednesdays I usually value a medium long run for marathons (1-1.5hrs) and ran at the very easiest pace to recover from Tuesdays workout and to be ready for Thursday's pace day. I have come to value running at goal paces on Thursday, especially for marathons....these days are focused on running at goal pace and somewhat progressive starting above MP at the beginning finishing a bit faster than MP. The closer to race day Thursday becomes even paced at MP for 8-10 miles. Fridays are always easy 30-40min. For Long Runs, I aim to run at a comfortable easy pace for 1.5-2hours, 60-90 sec slower than MP. I try to alternate the training stimulus with either time increases at long run pace for the remaining minutes 30-50 minutes above 2 hours, or with MP work for 20-40min or 3-6 miles at the end, or as a faster finish progression, or broken up into 2-3x2 miles at pace and sometimes running as fast as I can for the final mile or 5 minutes at the end to run hard on tired legs. The overall training program in a week features more aerobic "time" versus tracking miles, 1min-2min slower than MP, turnover work but continuous running in the form of fartleks, and most importantly, pace work to know my goal pace like the back of my hand. In a given week, my workout paces go from faster than MP, MP, to Long Run pace with MP at the end of a long run on tired legs from the week. Below I go into more detail about my experience and background of what I did most recently that led me to the general pace structure of my runs for marathons.
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I have run 5 marathons so far in my lifetime and the most recent marathon I ran was the best in terms of my execution. It wasn't my PR, however, the goal for me that day was to run a negative split half marathon, or at the very least even split and not bonk the final 10k. To outline what I did, my goal marathon pace was sub 3 hours, and I ended up with great conditions come race day and ran a 1:28:30 first half, and 1:27:30 second half. My PR is 2:47 and ran a couple mid-2:50 races, but each of those races I blew up around mile 18. The year I PR'd in my marathon I ran a 1:14:50 half marathon though much earlier in the year. My basic takeaway from my previous marathon experiences where I bonked was that I was going out too fast the first 30-45 minutes of my race...I decided to adjust my training schedule that featured more miles at an aerobic effort and to focus on marathon pace work. From a metabolic, though well substantiated physiological view, I wanted to make sure that the first 1/3 of the race wasn't too fast so that I could save my glycogen stores for the last 2/3s or 2 hours of the race. Many studies point to the fact that we only have about 2 hours of glycogen which is a quicker source of energy versus fat for the faster marathon paces (Sub 3 hours, and more so for 2:30). However, since my fitness pointed to the fact I was in the 2:50 range for my marathons, I needed to figure out what to do for the first 30-50 minutes of a marathon.
To tackle this, I took some guidance using HR rate training to dictate many of my aerobic miles, aiming to keep my HR in the "fat burning, 1/2 zone" for most of my easy runs and long runs. I am 30 yrs old, and have tested out with a high max HR around 195, and based on some HR zone tables of around 140-150 for my Z2 I found my avg aerobic paces were in the 8:30-8 early in my program and as aerobic threshold improved, the pace improved to about 8-7:30. I also valued progression running as well. Overall, a focused 12 week plan was suitable with 3x3 weeks of [2 weeks of mileage increases and 1 recovery week of about 20% less volume/moderate intensity]. For the 2 week builds, I did one week allowing increased long run time to be my training stimulus, and would run these starting out slow (like a Kenyan shuffle), and then run the next week with Marathon Pace. Tuesdays were fartleks (I decided to not do intervals of 800-2ks, but do a variation of fartlek ladders going down, like 3x 3/2/1, with moderate equal recovery paces during the rest). Thursdays were "aerobic threshold pace days" targeting my time goal at MP 6:40 , and keeping an eye on my HR was around zone 3-4 in the first few weeks, but with fitness gains became predominantly Z3. What this meant, was that I was able to run Z2/Z3 at a faster pace and not burn too much glycogen, and with a solid nutrition plan be able to run the last 10k without my body shutting down.
Overall, keeping an eye on my HR helped me slow down on easy days. But, I also evaluated my marathon pace by feel, and fartleks helped me to feel more comfortable at MP. Objectively, it was encouraging to see that at a given HR my pace was faster which gave me confidence that my body was more adept to burning fat early on in a marathon race to reserve the majority of glycogen stores to push the pace on the back half of the marathon. In terms of Squier versus Kenyan, I think my experience with training falls in the middle, maybe leaning towards Kenyans for some aspects of my Tuesday Fartleks and Thursday Progression/Tempo/pace days, and towards Squier for my Long Runs with surges and faster efforts, but for the most part slower than MP. I enjoy the discussion on this topic!