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Allegra-D (pseudoephedrine) and changes to maximum heart rate and HRV

JazzRunnerDP
11 months ago

BACKGROUND

Starting in mid-September, I took Allegra-D, a decongestant, for two weeks. A known side effect of one of its active ingredients, pseudoephedrine HCI, is an elevation of heart rate. Starting the day I started the Allegra-D, I noticed two side effects:

  • The heart rate readings on my 965 were 5-10 beats above normal. This was both at rest and during exercise. By "during exercise," I mean that my heart rate was 5-10 beats above what I would expect for the effort being performed.
  • My seven-day HRV average began to decline. Prior to taking the Allegra-D, it had been ranging from 43-49. After taking the Allegra-D, it ranged from 28-32.

I consulted my pharmacist about these side effects and was assured that the drug would be out of my body in about four days. I stopped the drug at the end of September, expecting the effects to be gone by early October. They were not gone by then. In fact, it is only now, in early December, that my heart rate seems more in sync with my running effort and my HRV is starting to climb back to its normal range.

During the period when my heart rate was high, I continued to exercise at my normal level.

HEART RATE QUESTION

My 965 detected the higher heart rates and raised my maximum heart rate from 173 to 180. It also raised the target heart rates for the workouts it prescribed. This was fine while my heart rate was elevated. But now that it's back in its normal range, I can no longer hold the heart rate the 965 demands for Threshold runs, 157, as my lactate threshold is about 154. I know I could enter a manual heart rate maximum, but would prefer to let the 965 auto-adjust downward. Does anyone have any idea how long this will take?

HRV BASELINE QUESTION

As my seven-day HRV average declined, so did the baseline HRV range calculated by Garmin. Pre-Allegra-D, my range was generally 38-56. It dropped to as low as 30-43. The drop was not immediate, but seemed to follow the drop in seven-day HRV average by weeks. See the first screenshot below with my normal baseline and early decline of the seven-day average. In fact, the HRV baseline continued to drop, even as my seven-day HRV average began to return to normal in early December. See the second screenshot below for this time period. Does anyone have any idea how long the HRV baseline takes to change upward after a decline like mine?

  • 0 11 months ago
    JazzRunnerDP said:
    I know I could enter a manual heart rate maximum, but would prefer to let the 965 auto-adjust downward.

    Why?

    JazzRunnerDP said:
    Does anyone have any idea how long this will take?

    According to Garmin's document, forever, because the HR Max is only increased from an existing value when certain qualifying conditions are met.

    If I were you, I would drop your HR Max to a recent maximum effort workout peak HR, and let the watch auto-detect it for you to HR Max.

    Note: I personally have disabled HR Max auto-detection because it gave me idiotic values several times. I now use field tests to (re-)evaluate my HR Max as I go. Recently, I have noticed that several users have reported good HR Max detections, so I am testing it yet again. Otherwise, my preferred method is to run a 5k PB and to add 5bpm to the peak HR of that race.

    (emphasis below added)

    AUTOMATIC MAXIMUM HEART RATE DETECTION

    Compatible Garmin devices can automatically update your maximum heart rate using your performance data. If a heart rate higher than your currently set maximum is identified and passes a reliability threshold, your personal maximum heart rate is updated on the device or in the Garmin Connect app.

    This feature can be turned on or off in the Physiological Metrics -> Auto Detection menu of the device.

    https://www.garmin.com/en-US/garmin-technology/health-science/heart-rate-monitoring/

    JazzRunnerDP said:
    Does anyone have any idea how long the HRV baseline takes to change upward after a decline like mine?

    We know that it takes about three weeks for the HRV baseline to be established and that the rolling comparison period is a week average. If we assume that the baseline continues to be evaluated over 3 weeks, we can expect to see significant intra-week peaks and drops to be reflected within 1 to 2 weeks into the baseline, and slower trends after 2 to 3 weeks.

    Note: Garmin doesn't publish the formula(s) used to calculate the baseline. I speculate the baseline represents an interval of confidence of the range of the overnight averages, since it seems to respond to overnight average peaks and drops within about a week.

  • 0 11 months ago in reply to Etupes25

    It turns out that at least with the latest firmware, the HR Max auto detection can LOWER your HR Max. It just happened to me today as I am back to testing this HR Max auto-detection feature. This is a good development.

    I will continue testing to see if the feature is still sensitive to erroneous HR data during warmups, for example (mostly using the chest strap in cold/windy weather, despite wetting it and using gel).

    Back to your question, there is no indication of how long it takes for a new HR Max to be evaluated, or what kind of run(s)/acitivty is takes. My downward update occured during a base+fartlek run where the higher speed intervals were 1mn at threshold.

  • 0 11 months ago in reply to Etupes25

    I have the HR Max auto detection almost every day. Because it's bouncing between 188/189. But I'm always using an HRM-Pro+. are you using a HRM strap? I guess this could help you also to get better readings.

  • 0 11 months ago in reply to StefanScheddy

    Thanks for the idea. I am not currently using a chest strap. My maximum HR gets updated without it.

  • 0 11 months ago in reply to Etupes25

    Thanks for your insights.

    I prefer to allow the watch to set the maximum HR as I am hoping it will be more accurate than any estimate I can input.

    Dropped my HR max to a falsely low 160 (My lactate threshold is about 155.) with the idea of resetting the ranges for Garmin's offered workouts. I turned off HR Max auto-detect overnight and turned it back on in the morning. The target values for the offered workouts were lowered to more realistic levels. When I saved this morning's Base workout, average HR = 121, the 965 did an auto-reset of max HR to 178, which seems a bit high. Pre-decongestant it was 173. Perhaps the 965 is including the time of the decongestant elevated HR when it calculated this most recent max HR. Those rates were 5-10 BPM higher than pre-decongestant.

    The HRV baseline does seem to be reacting to the uptrend in my HRV with a lag of about a week. Perhaps it will be back to what it was in three weeks.

    Thanks again for your information and your dedication to analyzing just what to expect from these watch features.

  • 0 11 months ago in reply to JazzRunnerDP
    JazzRunnerDP said:
    My maximum HR gets updated without it.

    Yes it will, but if you really care about the metrics (including HR Max) you should only use a chest strap during exercise. Even with a chest strap, there are some slight risks of erroneous data (dry skin, wind/cold weather during warm up).

    JazzRunnerDP said:
    When I saved this morning's Base workout, average HR = 121, the 965 did an auto-reset of max HR to 178

    Yes, the updated algorithm is obviously looking at historical data (Garmin doesn't publish the details). You can get a higher  HR Max than the last workout when the detection happen. I guess it could even be lower that the peak HR of the last workout since the watch is filtering data for that purpose, and the last peak might not qualify for inclusion...

    At any rate, I am changing my tune on the HR Max detection and it might work well now. Note that some users have been complaining that auto-detected HR Max has messed up with their LTHR zones. I am using HRR these days and I didn't see these issues. When they happen, you'd have to reset the zones.

  • 0 11 months ago in reply to Etupes25

    Think I'm going to give it a few weeks to see if the drug-induced high HR readings get eliminated from the algorithm's calculations and see if the auto-detect resets max HR back to around 173. In the meantime, I will continue experimenting with manual max HR settings with and without auto-detctect turned on.

  • 0 10 months ago in reply to JazzRunnerDP

    How did it go? I'm in a similar situation and hoping with time it'll auto adjust.

  • 0 9 months ago in reply to Anthony

    I stopped the Allegra-D in late September. In early December (!) I started to see a return to my normal 7-day HRV range of mid to high 40s.  A few low daily readings brought the 7-day average floated down to the low 40s, where it is now. Am hoping for some higher daily readings to bring the 7-day average back up. The baseline range floated up as my daily readings increased, though the baseline increase lagged the daily increase by at least a week.

    You should know that I continued my normal training load through my period of low HRV without difficulty. In mid-December, I even ran a 72 mile week that included one run of 27.5 miles.

    Since I've seen how a drug can affect HRV without any noticeable effect on my performance, visited a cardiologist and talked with him about HRV, and done plenty of Internet research to see how peer-reviewed research papers claim HRV can be used, I am putting much less weight on what Garmin claims HRV can predict. It was the cardiologist's opinion that current heart research does not attribute much in the way of general well being to any HRV measurement and that I shouldn't be too concerned about it. Based on these three factors, it appears to me that Garmin puts undue and unsupported emphasis on HRV as a factor that can predict general health and/or exercise readiness.