Morning vs. afternoon run

Even during 80/20 the prescribed warmup my HR was often racing even at the slowest paces; it would eventually settle, but not until I was well into a workout.

Adding a relaxed mobilization warmup session for 5-10 minutes seems to be the cure for me. Just opening up the thoracic area and hip flexors and I can start workouts without the morning tightness and the elevated HR phenomena has disappeared.

I guess that aligns with the 80/20 philosophy – sometimes you have to slow down to get faster…

Oliver, in general, yes. I recommend relying on power independent of HR, except in extreme situation such as temperature and extended workout (2 hours run and 4 hours bike). Whether it’s AM or PM, whether HR says 140 or 150 for the same watts, use the reliable output that power provides over the sketchy feedback of HR.

It’s not a perfect analogy, but let me refer back to the automobile comparison from our document Intensity Guidelines for Running:

There are four ways to measure intensity: pace, heart rate, power, and perceived effort. The testing protocols for all four types are listed below. Each metric has different applications among the three triathlon disciplines. Each metric also has certain advantages and disadvantages. Power is an output, pace is an outcome, and heart rate is an indicator. Let’s use an automobile as an example. Horsepower (power) is the output, and represents actual work performed regardless of terrain, grade, or environmental factors. Your speedometer (pace) indicates the speed, or outcome. Your engine temperature (heart rate) represents how the car is responding to the output and environment. During a hilly ascent, the output (power) might be high, but the outcome (speed) might be low. On a hot day, the engine temperature (heart rate) might be very high even when stopped at a light with almost no output and zero outcome. For this reason, power is considered superior to pace, and pace superior to heart rate to measure intensity. There are some exceptions, such as hills, where HR can be superior to Pace to measure intensity. The recommended best-practice is to use Power or Pace as your primary measure, with HR as a secondary measure.

How often do you check your engine temperature when driving? Probably only when it exceeds a certain threshold. If you have Power, HR should be the same. Rely on Power and only use HR it it is flashing a warning sign, like Zone 3 HR when your Power says Zone 2.

Consider this test: run with power for 4 weeks, capture HR, but don’t actually look at HR for 4 weeks of running. Let yourself learn to trust power. After 4 weeks, analyze your AM and PM runs and find the Power:HR ratio for each run. I’ll bet you’ll find it won’t be more than about 5 beats off.

I understand this reluctance as athlete move from HR to Power. In the early 2000s, when cycling power meters were just coming out, there was this same hesitation. It was almost a grieving period as athletes “broke up” with HR and committed to Power. Now that running power meters are mainstream, I’m seeing the same hesitation with runners.

My mentor, Joe Friel, said it best to me when he said “introducing training with power was like getting glasses. I didn’t know I was blind until I got glasses.”

Any (ok, that’s hyperbole, almost any) athlete who trains with Power will quickly realize how powerful it is relative to Pace and HR, and you’ll soon let go of those other options.

David

Oliver,

Yes, I would expect power:pace ratio to be the same AM or PM, regardless of the difference in HR.

I can think of only one scenario where, for a given course and conditions, a set power output would equal different pace, and that is athlete weight. No other internal factors would change the power:pace ratio, only external factors like wind, temperature or terrain. Unless your weight is significantly different AM to PM, you won’t see a change in power:pace ratio.

Your raw power output might be lower AM vs PM for other reasons, but the power:pace ratio won’t change.

There are other reasons to prioritize workouts in the morning, independent of what we have discussed here. Morning workouts are more likely to get done, morning workouts trigger metabolic advantages for the remainder of the day, training late in the day can interfere with sleep… outside of HR or power:pace ratio considerations, AM training has more advantages over PM training.

You’re also really asking: where will I get the best training effect? AM or PM? In terms of direct fitness benefits, there is no difference. In terms of auxiliary advantages, morning is recommended.

Apologies for implying you were hesitant on switching to power, you’re clearly on -board and want to get the most out of it. What I observe with athletes is the reluctance to let go of heart rate, even after switching to power.

David