Once-a-miler wrote:
Would HR data help adjust the score? Or is this not calculated in the TSS? Either way, it would probably be beneficial to pay attention to HR and compare when at altitude.
Heart rate is not a variable in TSS. But I think you can get a gauge of your response to elevation increases and decreases using heart rate by analyzing the correlation between heart rate and power as you do a steady climb starting from sea level or 3,000 feet and going up to 9k (Tucson) or even up to 12k feet (Maui). But yeah, you'd have to test either in an altitude tent or somewhere like Maui, while controlling the conditions that you know impact the absolute and the variability within my heart rate for a given day (for me, total training stress across sports, caffeine intake, sleep, and temperature/hydration levels are known variables that impact heart rate) and on a specific level within a given ride (cardiac drift, temperature again).
Physiologists hate when plebes try to come up with a way to "adjust" TSS based on heart rate because heart rate is so impacted by those variables, and how those variables impact a given individual varies wildly from individual to individual. When I'm feeling my worst, my Garmin 935 thinks I'm in my best condition (10 minutes into a ride or run) because
look how fast you're going at such a low heart rate when the reality is my heart rate is altogether anemic because I'm shelled from training stress. But if you spend enough time looking at your heart rate and power numbers, day after day, month after month, year after year, then you have a pretty good sense of what those things are for you.
When I lived in Denver I couldn't wait to go on a business trip to sea level and crush my tempo / threshold efforts 25 seconds per mile faster than I could back home. I felt like superman with an extra oxygen reservoir or something.
Going the other way is similar for me: a couple weeks ago, I was up from sea level in Tucson and climbed up Mt. Lemmon and Mt. Graham within a few days of each other but it reasonably similar weather conditions (~3,500 to ~9k feet). These are steady climbs and I made an effort at holding steady power within a tight band. My heart rate (netting out typical in-ride cardiac drift) was ~15 beats higher for the same wattage at 8,500+ than it was at 3,500 (which is basically sea level equivalent for me in my testing) and that's with an imperfect weighting to the significantly cooler weather at the top, which has a material impact on heart rate for me. All else equal, with respect to elevation, things start separating for me at 4k always -- by the time I'm in Reno at 4,500, how fast I can go is significantly different from how fast I can go at sea level, which I only learned, of course, when I showed up in Reno from Texas and blew up my race because I was trying to run what I could in Dallas -- and I can see this in my Lemmon/Graham data on a same day/ride basis (with the elevation as my axis).
To Coggan's point, when I ride with my friends up Lemmon or Graham, they seem to see fairly similar shifts with their heart rate/PE/power tracking as they climb. But when I do a big ride with my friends who are impervious to humidity on a very humid/hot day, well it's pretty obvious to me that I just shouldn't be riding with those friends on very hot and humid days because my numbers are much much more impacted on account of those conditions than theirs are, even if at 70 degrees with 20% humidity our FTs / FTs per kg are identical, and I end up dropped -- this is because for me, the impact of humidity and high heat (with the related variables like hydration) on my heart rate and effectively on the power I am capable of generating seem to be significantly greater than altitude.