Perceived Effort vs "Real" Effort

I run quite a bit and almost always have my heart rate monitor and GPS watch. So, I tend to have lots of data about route, distance, time, pace, heart rate, weather, elevation, etc. Most of my runs are classified as "easy" (less than 70% heart rate reserve) and they do feel easy. I'm not breathing hard, I feel fine, and the miles roll by at a leisurely pace. Those easy runs are meant to be easy, they feel easy, and my heart rate monitor confirms they are run at an easy effort. Perceived effort equates to real effort (as measure by HR monitor).

Once a week, I run harder--that's my tempo run. It's intended to be a moderate-hard effort at about 80-85% HRR. Tempo runs are great for increasing your lactate threshold. You do enough of these tempo runs, at the right pace/effort, and you'll see improvement in your running and racing. In addition to pushing your lactate threshold, these targeted runs will build running economy, speed, and "harden you" to race efforts. They build character and discipline without the higher risk that other types of speed work entail. I closely monitor my heart rate during these tempo efforts. I warm-up before and cool-down afterward. Lately I've been running the same 2-3-2 pattern: 2 miles easy (but building in speed), 3 miles at tempo effort (usually right at 80-81% HRR), and 2 miles easy recovery jog. My HR-based effort is very consistent, but my "perceived effort" varies from week to week. Even on the same course. What's up with that?

I always figured if it was hot and sunny, then my heart rate would be elevated, so I'd run the same effort, but at a slower pace. This does seem to be true. Same with being stressed out or tired. Elevated HR, slower pace. So, if I run the same HR, shouldn't my perceived effort be the same? Not for my tempo runs! If the conditions are good (cool, dry air) I run much faster with the same heart rate, but I also feel more comfortable and my perceived effort, while moderate, is definitely not hard. Yet when I run in warmer and humid conditions, at the same heart rate, I run slower, but feel like I'm working very hard. The efforts in those tough conditions seem much harder. My perceived effort does not match the "real" effort measured by the HR monitor. On the better days, at the same 80-81% HRR, I feel like I'm working at about a 7/10 effort. Bad days feel like 9/10 at the same heart rate reserve!

I can't explain it. I suppose I am less comfortable on those warmer days, but that should figure into the actual heart rate. On easy days, my perceived effort matches my heart rate. Sure I may run slower or faster on easy days, but it's still about the same heart rate and perceived effort. Not so on tempo efforts. My breathing and heart rate are almost identical on each tempo run, but the perceived effort varies week to week mostly based on weather. Even considering cardiac drift, dehydration, and fatigue, my HR should go up, my pace should slow, but my perceived effort should be about the same. Doesn't seem to be the case. I'm sure there is an extra mental thing going on in the poor weather.

Oh well, I'm going to continue the tempo runs and see where they bring me. I'm convinced they are making me a stronger runner at all distances and paces. And my easy runs are becoming faster. I'll keep an eye on other variables to see how my "perceived effort" correlates with my "actual effort" based on heart rate. I love data.