A tale of 2 different 5K run tests, and the training in between them.
I had heard for a while about the cardio benefits to training in Zone 2 (heart rate at 60-70% of your max), but when I did the math it became difficult for me to find a way to stay in this zone on what I would call “runs.” Any time I’d think to myself “this will be an easy run,” I would end up overshooting HR Zone 2 and going “too fast.” For me in my early-mid 30’s, Zone 2 would equate to about 110 beats per minute (bpm) to 130bpm. On any kind of jog at all, I’d very quickly surpass Zone 2 and get into the 130-150 range, which was training “too hard,” or so the guidance said.
Note: Widely-accepted “age-related” max heart rate works out to be 220 – your age = max HR.
I did not intend to run this experiment, but in hindsight I’m glad things worked out this way. Let’s talk about my baseline (first) 5K run first.
Initial 5K Test
Date: November 25, 2022 (the day after Thanksgiving)
Conditions: clear and calm, low 40s F
Time: 23:57
Average HR: 173
Max HR: 182
Notes: this felt like a test. I had been working out regularly and wanted to see how I would do with a 5K distance, aiming for my personal best time. At the end I was pretty spent, I would say RPE (rate of perceived effort) for this run was like an 8 or 9. That day, I don’t think I could have gone faster. It was the day after Thanksgiving, but I was well-rested and well-hydrated.
The Training Montage
In-between these two 5K runs, I completed a whole bunch of rucking focused training. I’m pretty often signed up for PATHFINDER Ruck Training and trying to complete Endure or Advanced level, which involves a lot of ruck miles (for me). They usually end up being 2-3 mile rucks, which take me about 25-45 minutes with a ruck weight of 30-50 pounds. Based on my goal pace and the terrain near my house, I’m typically moving at a good pace, aiming to exceed 4mph (go faster than a 15:00/mile pace).
I’ve been doing this for a while with the goal of improving my cardio fitness for sub-30 minute efforts. I volunteer as a firefighter in town and want to get the most out of my SCBA cylinder’s limited air supply. It’s commonly called a “45 minute” air cylinder, and 1/3 of that is the reserve air/time for you to get out of dangerous atmosphere, i.e. your work is done and now time to get out. Thus the 30 minute goal – to maximize amount of work I can do before the alarm goes off.
Training frequency for these type of 2-3 mile rucks: between November and March, approximately 3-4 times per week. I did not complete a PATHFINDER program during this time – I had a habit of putting off challenges or letting life get otherwise “in the way.” But that’s OK. The community is great, their workouts are also great and utilize the same equipment I have at my home garage gym setup, and there’s basically no reason not to be involved. Even if sick kids make you miss your timed 12 mile ruck, etc. If there’s one thing that the conclusion of this tiny study imparts upon you, let it be this:
You do not need to finish the PATHFINDER program to see huge fitness gains. There is a lot of value in going after the ruck miles and the workouts, even if you don’t check every box required to get your patch.
Sure, it is a great feeling to complete your program, earn your morale patch, and all that. But it’s not the end-all/be-all, it was not a waste of time if you “come up short.” The journey is the destination, or something like that. What I’m getting at here is that I spent a few months doing a ton of Zone 2 HR training, in the ballpark of that half hour duration, and saw great benefit. My resting heart rate and HRV have improved over this time, in addition to the pace/speed gains mentioned below.
(Though, due to the stomach bug in the week leading up to the race on 3/25, my HRV (heart rate variability) numbers were out of whack. But +1 for tracking this data: by knowing my normal ranges for resting/awake heart rate and having an idea of my HRV, I knew I was fighting off a bug versus some momentary indigestion, etc.)
Follow-up 5K Test
Date: March 25, 2023 (Schenectady Firefighters’ Cancer Foundation Run 4 Your Life 5K, certified course)
Conditions: clear and calm, low 40s F
Time: 24:23
Average HR: 142
Max HR: 158
Notes: this run felt… so easy. I was coming off of a stomach bug for a couple of days, which had kicked my butt and made me feel like I didn’t really want to push the pace. I wasn’t going into this one to race. RPE I’d say was about a 5-6, I was moving with a purpose but could have talked with a friend as I ran. Then I looked down at my watch at the 1 mile split.
7:48.
What? How was this possible? I was hardly trying – I felt like I had barely broken a sweat during the first mile. I had started further back in the pack at the starting line, setting myself up around ~9 minute mile or so runners. To be honest, I was a little worried I might have a negative GI experience during the run and need to bail into the woods, emerge 1 sock shy of a pair – you get where I’m going with this. At the start, the strollers were basically right behind me. But then as the race played out, I was passing plenty of runners, and feeling easy, breezy, beautiful, covergirl.
In fact, the frustrating thing about this run was that at the end I saw my finish time was pretty dang close to my November 5K test, and that the race day course had more elevation, and I’d been sick. So by all accounts I should have been worse-off. Now, at the finish line, I was left with a major feeling that I had left some time out on the course and I could have easily shaved a minute or more off of this run.
Numbers all in one place:
| Date | Time | Average Heart Rate | Max Heart Rate |
| 11.25.2022 | 23:57 | 173 | 182 |
| 3.25.2023 | 24:23 (1.8% slower) | 142 (21% improvement) | 158 (15% improvement) |
Conclusion
I’m attributing the improved RPE, feeling, and average heart rate numbers at the 2nd run to all of the ruck training I had done in between. The months before the November 5K test did not have as much rucking/cardio endurance type work in them, though I was working out and doing some runs. In hindsight, they were too fast – I don’t know that I did a single “zone 2 specific” run in the period leading up to the 11/25/22 test.
So: you’re probably running or doing your cardio days too hard, and some very productive training will happen in sessions that don’t FEEL “hard” enough to be productive at all. It’s a “trust the process” type of thing, and definitely something that I had overlooked in my prior training. As best I can explain it, it seems that the Zone 2 work sort of recalibrated the cardio gauge of what is “easy” and thus made me faster at the same perceived effort – or (6 of one, half dozen of another), made that same speed/pace feel a lot easier to achieve and maintain. I plan to continue testing this out, but it would seem that max efforts are going to be a lot faster moving forward.
Special thanks to PATHFINDER Ruck Training for the community and programming library. Learn more about their ruck-based fitness training at their website: http://www.pathfinderrucktraining.com
Have any thoughts? Put them in a comment below or email them to me: albanygrt@icloud.com.
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