The Treadmill-ARC Aerobic Crossover Workout

Since ramping my training volume back up I’ve had an ongoing problem with staying in an aerobic, zone-2 type of heart rate zone during my “easy” runs.

The general rule is always to run as slow and as easy as you need to in order to stay in zone 1-2 (up to 75% max heart rate). When you’re undertrained and you go to run easy, what often happens is your heart rate steadily climbs at the same effort, until finally there is no pace slow enough for you to continue running.

From experience, I definitely have the aerobic endurance to go for hours, but I often get into 75-80% of max HR after a while, and then it’s no longer an easy workout. It’s more of a moderate, or what Jack T. Daniels would call an M Pace workout. Different stimulus, different training result, than I’m seeking. Even if I walk for a bit, when I run again it just spikes right back past zone 2. Walk breaks do no good. I’ve redlined my cardiovascular system for that workout, and there’s no going back.

Lately my 45 minute easy training runs, while I can complete them, are rather arduous. Whether the gym is well air conditioned or not, I was struggling and my heart rate would typically get into zone 3 before I was done. I actually got to the point where I was dreading the idea of doing another one. That’s not good. I’m not going to just beat my head against that wall again.

I’m looking primarily to build aerobic endurance, to build slow-twitch mitochondria below my aerobic and lactate thresholds, so that faster paces become easier for my body over time. As the late John “Hadd” Walsh has pointed out, if you go even a bit harder than easy, even if it’s well within your capabilities, you don’t get the needed stimulus to build those mitochondria. You have the strength to run faster, but you still don’t have the endurance to maintain it for as long as you want without revving your heart rate.

Adopting a ketogenic diet has helped me in that I’ve tapped out my prior glycogen stores. I took a longer run early Sunday morning, and was astonished at how super-easy it felt to run easy indefinitely, even though I was super slow, and lacked any ability to speed up without a sprint-like effort.

Now, while my body can go forever, it lacks the rocket booster glycogen effect to go too fast. However, when indoors (which is at ‘higher than ideal for running’ room temperature), or when encountering any sort of unavoidable stress outdoors (crossing a street with traffic, encountering an incline, someone or something interfering with your run, running in warmer than ideal temperatures)… your heart rate is often going to climb anyway despite your best efforts, until you’re so well aerobically trained that you can stay level for hours through any normal stimulus.

So I had a dilemma. I didn’t want to do treadmill runs at 12:30 minute miles just to keep my heart rate below 140 bpm, as while I would stay at a low heart rate my legs are now getting accustomed to running slow. As soon as I go outside and run at a comfortable intensity, my heart rate would just spike again, because my body’s not yet used to the naturally faster outdoor pace.

In Chicago, I worked around this by not working on this at all. Until my last year in town I never endurance trained indoors. I ran-commuted home from work many days, as easy as I needed to run because I had to. I couldn’t practically end these runs early: I needed to get home!

On weekends I just ran the lakefront trails near home, which loop in on themselves a lot and allowed me to get home easily once I decided I had enough. It also helped that Chicago’s notorious winters made it hard to overheat, and when snowy it was hard to run fast.

I don’t have that in Vegas. The coming winter will make temperatures easier to run in, but I do a lot of running on treadmills and outside briefly during lunch breaks in much warmer weather.

Cross training has a huge limitation, aside from the intensity being far below running: It’s very hard to get into the needed Zone 1-2 training zones doing any of these activities alone. I can go long, though in most cases it’s very hard to even get into zone 1, let alone spend much time training there. I don’t know that I’ve gotten much of a training benefit beyond general fitness and valuable blood/nutrient circulation from my cross training. While these workouts are generally beneficial, they don’t specifically train my zone 1/2 aerobic endurance, which is at this point what I need out of these workouts.

However… I noticed in some weekend workouts that, if I had a tough strength workout or similar, and then transitioned to the ARC Trainer, I could maintain a heart rate of 120-135 bpm, well within zones 1 and 2, for the entire 45 minute session. That made this a productive aerobic workout using a similar range of motion to running.

I tried using my standard 10 minute treadmill warm-ups, where I’d start super easy and ramp to relatively fast running, before these sessions. This worked relatively well for getting ARC Trainer workouts into zones 1-2. However, if I used the elliptical or spin bike it didn’t work as well: My heart rate would once again stay under zone 1 much of the time.

So, I needed to work on running at a more appropriate easy pace, even though (while comfortable) just doing a run at that pace on a treadmill would redline my heart rate out of zone 2 within 20 minutes. But I also didn’t want my training to be a bunch of 15-20 minute treadmill runs I would have to inch longer every week. There’s no way I could do the volume needed to get in racing shape, let alone marathon shape.

But I didn’t want to just go back to running however hard and letting things sort themselves out. I’ve gotten burned out before, and more recently injured, training this way. I wanted, this time around, to train “right”, to build my aerobic fitness through sustainable zone 1-2 base training, by hook or by crook.

A short while ago, I decided to try the following protocol at the (too) warm (for treadmill training) gym near my home.

  • I get on the treadmill and start an easy run at the same comfortable pace I would do those prior 45 minute runs.
  • I would watch my heart rate as I ran. Once it got to certain point, I would immediately stop the treadmill workout. Arbitrarily I decided to use Phil Maffetone’s MAF Method max heart rate formula (180 minus age), which gave me a result of 137, reasonable enough of a barometer.
  • (The following item may be skipped and is probably too complicated for even this description, but here is how I determined the pace to use: I actually reverse engineered my measured VO2max and used Runalyze dummy workout entries to approximate a treadmill pace that would be appropriate for an average heart rate between the bottom of my zone 1 and 137 bpm, which is an average of 128 bpm. I made sure the pace of an entered dummy workout would at least keep my estimated VO2max even in Runalyze.)
  • After stopping the treadmill workout, I immediately go to the ARC Trainer and work out for 30-45 minutes, depending on how long I lasted on the treadmill. If I had the time and energy, I’d go a full 45 minutes.

Long story short, it worked great, exactly as I hoped it would.

  • I was able to run a little over a mile in 16 minutes before my HR hit 137 and I immediately kill-switched the workout.
  • Once I got on and started the ARC Trainer, my HR cruised at 122-134 bpm the entire time, over the entire 45 minute workout.
  • This meant I spent a little over an hour (with minimal interruption) training easy at zone 1-2. My body did get the base training stimulus of running in this critical range, while making sure my heart didn’t have to work any harder than zone 2.
  • After initially starting with running I could still approximate the running motion with the no-impact ARC Trainer (another key reason other cross training tools didn’t work as well; even the elliptical’s motion is too much more of a bounce than normal running).

So now, going forward, I can use this combo workout as a base training or foundation aerobic workout. As I get more comfortable running in the slightly too warm gym environment, I’ll be able to spend more time in the workout running and less time on the ARC Trainer.

In a perfect world, eventually I can run 45 full minutes on the treadmill in these conditions without my heart rate ever exceeding the threshold, and never need to use the ARC Trainer. But I don’t have any expectations for now, beyond that over time my last-long time on the treadmill will improve.

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