Heart Rate, Heat training and Cardiac Drift

Triathlon Forum
1

Sorry if this is a duplicate of some topics that have been hammered here, but there are some specific points of clarification around multiple of these points.

I recently moved to Texas from the Northeast, I moved in April. The temperature from the 6 months up to me moving was low. Highs in the 30s in Dec, Jan and Feb then in the 40’s and 50’s in March and April.

Since moving to Texas its been mid-90s into the 100’s a lot, especially when accounting for heat index. As such, my HR is understandably higher than in the cooler climate (like 20 BPM for the same effort)

Pivoting for a second to Lionels recent video, talking about leaving Tucson and heading to Flagstaff. He talked about heat being a primary factor and not being able to train appropriately in that heat.

Now back to the question. Is HR the source of truth for training zones? Or is power/pace? If my Z2 pace in a cooler climate was 7:00 per mile, and now to hit that same HR I need to run closer to 9:00 per mile, what is correctly hitting my training stimulus? I feel like that data is conflicting on this and I have seen “HR is too erratic and not trustworthy” but also, HR is used to set training zones and many zone 2 advocates talk about people setting their Z2 pace too high and not getting the proper aerobic adaptations. This extends to cardiac drift. As I run further at a given pace, and HR drifts, am I leaving the aerobic zone and should long runs be decelerations? Or should I use my zones set in good conditions to guide my training and ignore HR when it is hot?

2

Sorry if this is a duplicate of some topics that have been hammered here, but there are some specific points of clarification around multiple of these points.

I recently moved to Texas from the Northeast, I moved in April. The temperature from the 6 months up to me moving was low. Highs in the 30s in Dec, Jan and Feb then in the 40’s and 50’s in March and April.

Since moving to Texas its been mid-90s into the 100’s a lot, especially when accounting for heat index. As such, my HR is understandably higher than in the cooler climate (like 20 BPM for the same effort)

Pivoting for a second to Lionels recent video, talking about leaving Tucson and heading to Flagstaff. He talked about heat being a primary factor and not being able to train appropriately in that heat.

Now back to the question. Is HR the source of truth for training zones? Or is power/pace? If my Z2 pace in a cooler climate was 7:00 per mile, and now to hit that same HR I need to run closer to 9:00 per mile, what is correctly hitting my training stimulus? I feel like that data is conflicting on this and I have seen “HR is too erratic and not trustworthy” but also, HR is used to set training zones and many zone 2 advocates talk about people setting their Z2 pace too high and not getting the proper aerobic adaptations. This extends to cardiac drift. As I run further at a given pace, and HR drifts, am I leaving the aerobic zone and should long runs be decelerations? Or should I use my zones set in good conditions to guide my training and ignore HR when it is hot?

I’m curious what other people say about this, and can only comment on my experience coming from the Northeast (though having run a bit in the Tropics as well as soupy summer days with a ‘feels like’ over 100), and in particular contrasting summer and winter training cycles for spring/fall marathons.

My 2 cents:

  1. I think that aerobic stimulus and relative energy utilization of fat vs carb cares mostly about heart rate; muscular and nervous system stimulation on the other hand care about pace/power. Depending on whether your training stress is intended to be dominated by aerobic vs musculoskeletal (or neuromuscular) considerations, you should use HR or pace/power as your primary constraint. So for aerobic base like Z2 work, you should use heart rate as a guide. For race-specific or higher intensity work, you might want to weigh pace or power more heavily – while still realizing that heat stress or exceeding HR thresholds might require you to adjust downward if you cannot hit the targets. For intervals too short to be at cardio steady state, use pace/power as a goal and tweak recoveries if needed so that you’re not hitting a thermal wall.

  2. Big cardiac drift indicates that you’re either not aerobically conditioned enough, you are not well acclimated to the heat, or it’s impossible for your body to reach a thermal steady state under the given combination of weather and intensity. IMO if you’re seeing big cardio drift you should start out slower and aim to keep pace constant so that you don’t leave Z2. Don’t do long runs as decelerations, that’s a really bad habit.

3

You should test in the conditions that you are going to be doing your routine training.

Whatever it is, use those figures. Adjust conservatively for race day.

4

  1. interesting about the fat vs carb being related to HR and muscular and nervous system being related to pace and power. That may explain the discrepancies in what to use, because people are referring to training those different systems

  2. Im definitely not well conditioned enough. I come from an American Football background, bigger guy (compared to triathletes and runners anyway) and very anaerobic leaning. I started in triathlon last year, and my Z2 runs were walk run combos, and eventually down to 7 min/mile before I moved here. Now I feel like I would be back to 9 or 10 min/miles combos but maybe I just need to suck up my pride and slow back down.

Thank you for the feedback!

5

FYI you should take my comment 1) with a grain of salt, I’m no particular authority on the subject.

If you’re bigger than the average triathlete / runner then your performance will take much more of a hit under hot/humid conditions. The smaller and leaner you are, the easier it is to run in hot conditions without overheating, because of higher surface area/volume ratio.

6

power / pace as the primary metric, hr as a lagging metric that needs to be considered in high temp environments.

the more you train in the heat the better you will be at adjusting your power / pace.

the more you train in the heat the better you will be at training and racing in the heat, and the faster you will be when its cool.

also, im in hot / humid texas.

7

I do almost all my training based on HR (except shorter intervals which are power based). When it’s hot, my pace slows down … it is what it is

Over time your body will get animated to the Texas heat and you won’t be impacted as much by the heat. But for now, it’s crushing us all :slight_smile:

8

I pay some reference to heart rate, but quite often my RPE does not reflect what I see in terms of rate, so sometimes I push things a little.

There are occasions when I am out on a long session and just looking at my watch seems to add 10-15bpm, which annoys me and then adds more. So I end up jogging along super slow with a heart rate in zone 4/5 despite being at an intensity I could run an ultra at.

I have a lot of mixed zones in my training so a lot of the time I make sure on that day that my heart rate moves up and down with the intensity of the intervals, this is the constant I use to negate the fact that zones can be flexible day to day.

One thing that kills me other than the heat is having colds constantly, I fly a lot and have young kids so I generally always have some form of sniffle

9

In terms of measuring or quantification of training load or a workout, we have RPE, breathing rate, HR, blood lactate (for about the price of a watch) etc for internal load and power/pace sometimes cadence or frequency for external output etc.

For a while there everyone was in a tizzy about using a a power meter and ditching everything else as “inaccurate”.

If you have a bunch of tools available to you it doesn’t hurt to use more than one at a time, in conjunction with each other :slight_smile:

Maurice

10

Sorry if this is a duplicate of some topics that have been hammered here, but there are some specific points of clarification around multiple of these points.

I recently moved to Texas from the Northeast, I moved in April. The temperature from the 6 months up to me moving was low. Highs in the 30s in Dec, Jan and Feb then in the 40’s and 50’s in March and April.

Since moving to Texas its been mid-90s into the 100’s a lot, especially when accounting for heat index. As such, my HR is understandably higher than in the cooler climate (like 20 BPM for the same effort)

Pivoting for a second to Lionels recent video, talking about leaving Tucson and heading to Flagstaff. He talked about heat being a primary factor and not being able to train appropriately in that heat.

Now back to the question. Is HR the source of truth for training zones? Or is power/pace? If my Z2 pace in a cooler climate was 7:00 per mile, and now to hit that same HR I need to run closer to 9:00 per mile, what is correctly hitting my training stimulus? I feel like that data is conflicting on this and I have seen “HR is too erratic and not trustworthy” but also, HR is used to set training zones and many zone 2 advocates talk about people setting their Z2 pace too high and not getting the proper aerobic adaptations. This extends to cardiac drift. As I run further at a given pace, and HR drifts, am I leaving the aerobic zone and should long runs be decelerations? Or should I use my zones set in good conditions to guide my training and ignore HR when it is hot?

You HR measures stress. So scrapping the stress gauge and training via performance (power/pace) in the heat can cause great harm. Training in heat is like training at altitude without any of the benefits. That’s why Sander’s left to train elsewhere, bc in heat your legs just don’t get as good of a workout while your heart/cardio get overworked. Good news is that you’ll partly adapt to the heat and your workouts will speed up in time. I’m big on HR in the summer because of the dangers related to over doing it.

11

Training in heat is like training at altitude without any of the benefits…

Nah, disagree with that. One winter I ran a 17:25ish 5k in December (chilly). Next week went on vacation to a tropical country and spent 2 weeks slogging out 7:45 miles in 75 degree dewpoints. Zero workouts. Barely finishing runs. Had to double most days just to maintain volume. Came back and the next Saturday went sub 16:50 when the temp was in the mid 30s.

Similar stories every fall going from slogging through summer runs in dew points of 72+ and then crushing a 5k/10k when the weather cools. Same for the bike. No power, no power, no power, dew point drops 10 degrees, massive power.

12

power pace speed is what the organism is doing. Hr is the strain of what you’re doing on the organism.

Not uncommon to see hr’s values 10+ bpm higher in early summer compared to winter for the same route/time/duration/intensity.

As you get more heat adapted you’ll be able to better handle the heat/humidity. unfortunately though at some point it just sucks and you can expect somewhat of a ok this is all I’ve got for this heat/humidity.

the good news is that you can go to just about anywhere else in the country and laugh at them when they complain about how hot it is.

13

If you’re bigger than the average triathlete / runner then your performance will take much more of a hit under hot/humid conditions.
Strong n=1 confirmatoin here.

14

“ Studies have found that, in addition to an increased rate of perspiration, training in the heat can increase an athlete’s blood plasma volume (which leads to better cardiovascular fitness), reduce overall core temperature, reduce blood lactate, increase skeletal muscle force, and, counterintuitively, make a person train better in cold temperatures. In fact, heat acclimation may actually be more beneficial than altitude training in eliciting positive physiological adaptations, says Santiago Lorenzo, a professor of physiology at Lake Erie College of Osteopathic Medicine”

15

Sorry if this is a duplicate of some topics that have been hammered here, but there are some specific points of clarification around multiple of these points.

I recently moved to Texas from the Northeast, I moved in April. The temperature from the 6 months up to me moving was low. Highs in the 30s in Dec, Jan and Feb then in the 40’s and 50’s in March and April.

Since moving to Texas its been mid-90s into the 100’s a lot, especially when accounting for heat index. As such, my HR is understandably higher than in the cooler climate (like 20 BPM for the same effort)

Pivoting for a second to Lionels recent video, talking about leaving Tucson and heading to Flagstaff. He talked about heat being a primary factor and not being able to train appropriately in that heat.

Now back to the question. Is HR the source of truth for training zones? Or is power/pace? If my Z2 pace in a cooler climate was 7:00 per mile, and now to hit that same HR I need to run closer to 9:00 per mile, what is correctly hitting my training stimulus? I feel like that data is conflicting on this and I have seen “HR is too erratic and not trustworthy” but also, HR is used to set training zones and many zone 2 advocates talk about people setting their Z2 pace too high and not getting the proper aerobic adaptations. This extends to cardiac drift. As I run further at a given pace, and HR drifts, am I leaving the aerobic zone and should long runs be decelerations? Or should I use my zones set in good conditions to guide my training and ignore HR when it is hot?

my 2 cts: you have to adapt your zones to the new enviroment, that means retest, recalculate, and follow up them until you are acclimated.

using zones for training are a simplication, you encapsulate the benefits of working in one zone, but also “its costs” and “recovering time”.

You have to take into account that HR higher means higher costs: because the dehydration (you need to improve it), because the working temperature internal and intramuscular, and also has impact increasing the time to full recovery (including a better nutrition and rehydration)

So, if you think that because you can sustain the efforts in Z2 or Z5 as before, but with higher HR, and then you don’t have to adapt your zones, you are only viewing the half side of a problem.

So, as said, if you open the view, you could understand that the better is:

  • recalculate your zones,
  • perform a specific adaptation period to new climate conditions
  • recover the normal training process

Or alternative:

  • try to adapt your training hours / locations to make it easier: some trainings indoor, some other in the night and some others outside to adapt your body, during the adaptation process.
16

Hit 235 last week, can confirm.

17

I agree with this and with the post by ajthomas. A section from a paper below, Saunders et al (2019) “Special Environments: Altitude and Heat”

TL;DR - heat training likely improves performance in cooler conditions, reasons unknown and findings slightly inconsistent. Possibly, as ajthomas says, due to increase in plasma volume from training in heat.

"Heat Training for Improved Performance in Temperate Conditions

In recent years, there has been a noticeable shift in trying to use heat acclimation to provide an added benefit to performance in cool conditions. There have been reported improvements in VO2max in untrained (13%) and unfit (23%) individuals in cool conditions after 8 days of working in the heat (Shvartz et al., 1977) and an increase (32%) in running time to exhaustion following postexercise sauna bathing (Scoon et al., 2007); although others have reported no improvements (Keiser et al., 2015) or inconclusive findings (Neal et al., 2016a).

The mechanisms modulating the potential transfer of adaptations and performance improvements between hot and cool conditions remain unresolved, but could be linked to a variety of ergogenic responses, such as cardiovascular, thermoregulatory, and cellular adaptations. For example, an increase in plasma volume resulting from chronic bouts of exercise in the heat may decrease whole blood viscosity, which has been shown to have positive effects on endurance performance (Telford et al., 1994). Adaptations from training in hot conditions may also allow athletes to train at any given speed with a lower heart rate and core body temperature, both factors being associated with improved exercise economy (Thomas et al., 1995). This is supported by findings from Lorenzo et al. (2010) of increased performance in a cool environment following heat acclimation being associated with improved economy, lactate threshold, and cardiac performance. Accordingly, heat acclimation may provide a stimulus for enhancing performance in nonthermally challenging environments by improving VO2max, lactate threshold, and exercise economy (Corbett et al., 2014). It has also been suggested that heat acclimation may preserve or enhance performance at altitude (White et al., 2014). The purported pathways for such a response include plasma volume expansion and improved cardiac efficiency, and involve the upregulation of hypoxia-inducible factor-1 in boosting oxygen delivery. Additional research is required, however, to thoroughly elucidate the mechanisms associated with improvements in performance in cool conditions and at altitude, as well as to fully substantiate the ergogenic cross-benefits of heat training on performance in these environments (Lee et al., 2016; McCleave et al., 2017; White et al., 2016)."

18

Training in heat is like training at altitude without any of the benefits…

Nah, disagree with that. One winter I ran a 17:25ish 5k in December (chilly). Next week went on vacation to a tropical country and spent 2 weeks slogging out 7:45 miles in 75 degree dewpoints. Zero workouts. Barely finishing runs. Had to double most days just to maintain volume. Came back and the next Saturday went sub 16:50 when the temp was in the mid 30s.

Similar stories every fall going from slogging through summer runs in dew points of 72+ and then crushing a 5k/10k when the weather cools. Same for the bike. No power, no power, no power, dew point drops 10 degrees, massive power.

I’ll give you that. I do see some benefit.

19

Lots of great points everyone. I can beat all the Texans on here as i live in the southern most part of Texas. This week has been brutal. Significant rise on my HR through all zones. Have you tried using a temperature/humidity running calculator?

20

no I haven’t, do you recommend one?

Thank you all for the advice. I sometimes train in the mornings, and I definitely notice its easier/improvement when I do my runs in the mornings. I can hold much higher paces than I could before. Unfortunately I have to swim in the mornings so I can only do morning runs on days that I dont also have a swim.

The heat adaptations is interesting I remember something about that same paper in on of the TR podcasts awhile ago.

I will make sure to focus on the metrics to hit my goals (HR for aerobic adaptations and reducing stress, pace for intervals)

I also started splitting some runs into doubles, I definitely am able to control the HR for the entire run so thank you for that tip!