Sunday Runday
In this weekly column, Android Central Wearables Editor Michael Hicks talks about the world of wearables, apps, and fitness tech related to running and health, in his quest to get faster and more fit.
Apple and Google/Fitbit jumped onto the training load bandwagon in 2024, and it’s long overdue. I credit my boosted VO2 Max directly to following my running watches’ training load guidance, especially Garmin’s training load focus graph. But no brand does it perfectly, and I’m more than happy to vent about their flaws.
Some leave their training load data too vague to understand. Some don’t differentiate enough between different types of load. And some put too much weight on your heart rate average when deciding on load instead of your varied heart rates throughout a run.
I’d love to combine training load elements from Garmin, Coros, Apple, and Fitbit into one ideal training tool that better reflects my actual training effort.
The training load TL;DR
For people who have no idea what I’m talking about, training load is an arbitrary number calculated by your minutes of activity multiplied by your heart rate effort level.
A 30-minute zone-2 or 3 run might net you 60 points of training load (aka 30 x 2), while a steady two-hour walk might only give you 40 points (120 x 0.33). A 15-minute track workout might net you 150–200 points, depending on your effort.
Different brands calculate load with similar methods but their own multipliers and unique heart rate zones. I ran a 10K wearing four watches today and got training load scores of 130, 140, 160, and 220 despite near-identical HR and GPS data. As I said, the number is arbitrary.
Why does it matter, then? Because they compare your acute load — your added-up score across a week of workouts — against your chronic load — four weeks of workouts — and see how they compare. You always want your recent acute load to match or beat your long-term chronic load. It doesn’t matter if your load total is 200 or 1,000, only whether it’s a better number than it was last week or month, without being so much higher that you hurt yourself overtraining.
What Garmin gets right (and wrong) about training load
Like other brands, Garmin tells you if your acute load is “optimal” to get fitter, with a training load ratio comparing your weekly total and monthly average. What I especially need, though, is “training load focus.”
Under Training Status on my Garmin Forerunner 965, I can find a graph that splits my four-week load into three categories: anaerobic, high aerobic, or low aerobic workouts.
Conventional running wisdom is that you can’t improve your VO2 Max by running hard every time. You need “conversational pace” workouts in lower heart rate zones to improve base fitness (low aerobic), plus max-effort sprints where your body can’t gain oxygen fast enough and burns muscular energy instead (anaerobic).
Garmin’s graph yells at me every time I have a low aerobic or anaerobic “shortage,” so I make a point of varying my training load types, whereas other brands might simply encourage you to gain as much load as possible. It’s helped me improve my VO2 Max from 46 to 51 in the past year or so.
My one (major) complaint with Garmin training load focus is that it puts way too much stock on heart rate average. If I run three miles in my zone 2 heart rate zone (HRZ), I usually get about 60 low-aerobic load. Today, I ran three miles in zone 2 and three miles in zones 3–4; in the end, all of that load went directly to high aerobic.
Every run “is analyzed from start to finish to determine the *primary* category into which it falls,” the Garmin Forerunner team explained to me. They do “split the load within an activity into anaerobic and aerobic, but we will not further split it into high and low aerobic.”
When I asked if they would “consider calculating and splitting up load focus based on mile splits or other criteria,” I received the rather terse response, “We have considered it.”
Their reply made me less than optimistic, but in an ideal world, Garmin would split up training load in smaller increments instead of focusing on the average. That way, I could jog for a few miles and then end with a high-aerobic mile for fun without worrying that it’ll drag the average up enough to cancel out my earlier restraint.
I’m also skeptical about how well Garmin’s aerobic/anaerobic split works, for what it’s worth. I ran a half marathon last month where I was mostly in zones 3/4 but consistently hit 90%+ my maximum heart rate for most of the last 30 minutes. I got no anaerobic training effect at the end, only high aerobic.
What Apple, Fitbit, and Coros get right (and wrong)
My ideal training load system would use the guts of the Garmin experience. I still love its training load focus and daily suggested workouts that adjust based on whether you need more anaerobic or low-aerobic load. I’d just “borrow” some things from Coros, Apple, and Fitbit/Google.
With my COROS Pace 3 or Vertix 2X, I don’t have to worry about averages. Each run splits the training load into three categories: easy, medium, and hard. So, when you look at the four-week intensity distribution graph, you know it’s accurate. You also get more specifics with the monthly Pace Zone Distribution graph, which splits exact load totals across each heart rate zone.
What holds me back from using COROS more often is the lack of guidance. I like how Garmin marks the “optimal” easy/hard training load I should have and adjusts workout suggestions accordingly, whereas COROS lets independent runners figure that out for themselves. I’ll admit I need the extra help