Correlation between HRV, sRPE and subjective fatigue in athletes

Today I will review the research I’ve read that investigates the relationship between perceived exertion ratings of a workout session (sRPE), subjective levels of fatigue and HRV in effort to examine the usefulness of HRV in reflecting training load in athletic populations. Like all of my articles, this report is based on my interpretation of the research and perspectives from personal experience.

The Research

In a brand new study from the JSCR, Sartor and colleagues (2013) followed elite male gymnasts (n=6, age 16) over 10 weeks of training. HRV was monitored daily every other week while sRPE was collected immediately following each workout. HRV strongly correlated to previous day sRPE in both supine (HF%, HF%/LF%) and supine to seated measurements (mean RR, mean HR, HF%, SD1). Relationships were also seen between HRV, and perceived wellness (foster’s index). HRV correlated with training load (sRPE) and psychophysiological status.

Though sRPE wasn’t used in this next study, KeTien (2012) monitored HRV, blood-urine nitrogen (BUN) and profile of mood states (POMS) in 24 national level rugby players over an 8 week conditioning program. The program progressed from more aerobic based work to more anaerobic/interval based work. Spectral measures of HRV correlated with both POMS and BUN at each time point throughout the training period.

During the 2006 World Cup, Parrado and colleagues (2010) set out to determine if perceived tiredness could predict cardiac autonomic response to overload in elite field hockey players (n=8).  A strong correlation was found between per­ceived tiredness scores and HRV. Higher levels of perceived tiredness (acquired from questionnaire) were related to lower values of parasympathetic tone (RMSSD), pNN50 and higher LF/HF ratio. In order to discern changes in HRV brought on by fatigue from changes in HRV caused by pre-competitive anxiety, the researchers had the athletes complete anxiety questionnaires.

“Results show that cognitive anxiety and self-confidence sub­scales of the CSAI–2 were not related to perceived tiredness nor to heart rate variability. In the absence of a relation between cognitive anxiety and heart rate variability, it can be assumed that the relationship established between heart rate variability indexes and perceived tiredness scores are attributable to the fatigue state.”

Accounting for pre-game anxiety is very important as previous research has shown this to affect HRV (Edmonds et al. 2012, Mateo et al. 2012, Murray et al. 2008), thus making it difficult to distinguish fatigue from acute anxiety on the morning of a competition.

Edmonds et al. (2012) found that HRV (HF) correlated with sRPE in youth rugby players (n=9) during a one week microcycle of practices and a game. However, game day HRV values were lower which was attributed to the aforementioned pre-game anxiety since training loads were reduced before the competition.

Smith and Hopkins (2011) monitored performance, HRV, sRPE and subjective fatigue in elite rowers (n=10) throughout an intense 4 week training period. Interestingly, the most improved athlete and the only overtrained athlete both had statistically similar levels of perceived fatigue and changes in LF/HF ratio. However, after looking closely at the data, RMSSD showed a noticeable decline in the OT athlete compared to the most improved who had a moderate increase in RMSSD. The determining factor however in this case was performance changes.

Thiel at al. (2012) found that in 3 elite male tennis players, HRV, serum urea and psycho-physical state (assessed by EBF-52 questionnaire) each responded to overload training. As training load increased, HRV (RMSSD) decreased, perceived fatigue increased and serum urea increased. However, performance increased (V02 max, Single Leg CMJ, DJ index) and therefore performance metrics should always be considered when trying to discern functional overreaching (FOR) from non-functional overreaching (NFOR). HRV changes act as an early warning sign while performance decrements may represent the initial transition from FOR to NFOR.

Cipryan et al (2007) found that HRV correlated to performance in hockey players (age 17, n=4) but did not correlate to self-reported health status. Therefore, coaches should use caution when using perceived stress to predict ANS status and thus an objective measure (like HRV) is still recommended.

In elite female wrestlers, perceived stress (in the form of; excessive competition schedule, social, education, occupational, economical, travel, nutritional, etc) contributed to NFOR when HRV parameters were significantly increased (Tian et al. 2012). There was no mention of perceived stress/recovery in the NFOR group with significant decreases in HRV parameters. Regardless, subjective measures of stress including non-training related events require consideration when planning training. Monitoring the global stress of an athlete is more meaningful then simply training load.

Plews et al. (2012) monitored HRV and perceived measures of recovery (sleep, soreness, etc.) in two elite triathletes over a 77 day period leading up to competition. One athlete was considered NFOR. Perceived levels of recovery were not associated with HRV. However, the NFOR athlete admitted that she felt deterred from  reporting  low scores as anything below a certain score would be automatically sent to the coach. Therefore, when relying on perceptual measures from athletes, coaches must be prudent in ensuring honest reports. HRV was a better indicator of fatigue in this study.

The last study I’d like to mention only appears to be available in German at the moment. I translated the paper with google, however it was very rough to say the least. Therefore I will simply quote the pertinent information from the abstract:

“6 endurance athletes measured morning heart rate, heart rate variability (HRV) and mood state during a normal training period, a 17 day ultrarace (Deutschlandlauf) and following a recovery period. 4 out of 6 runners could not finish the race due to injury or exhaustion. 3 of them showed diagnostically relevant criteria of overreaching. All runners who quit the race showed increased morning heart rate, decreased HRV and a decreased mood state during competition. The studied parameters showed individually different adaptations but there were early changes that preceded the abortion of the run that gave diagnostically relevant information.” (Bossmann 2012)

Thoughts

Though there appears to be a strong tendency for HRV to reflect perceived training load and subjective fatigue, an objective measure of ANS status should still be considered. Subjective measures from athletes are only meaningful if honestly reported.

I’ve personally seen a strong correlation between morning HRV score and session rating of perceived exertion (sRPE) of the previous day’s workout. However, I’ve learned that this relationship isn’t perfect. I’ve experienced situations where;

–          Perceived exertion may be high but HRV response may be minimal if the workout is familiar (exercise selection, order, intensity, etc.).

–          In direct contrast to the above, perceived exertion may be moderate but HRV response may be significant if the workout is unfamiliar.

–          Non-training related factors affect HRV. Sleep, aerobic fitness, mental stress, nutrition, etc. can all impact ANS activity, possibly obscuring the relationship between training load and HRV.

–          Stress from travel, illness, occupation, etc. may have a larger impact on ANS than is perceived and reported.

–          More on other factors effecting HRV here.

In conclusion, obtaining both objective and subjective measures of fatigue along with performance indicators will provide a more accurate indication of training status. Monitoring of these variables regularly should enable the coach to better manipulate training loads to ensure progression and avoid unintentional overreaching.

References

Bossman, T. (2012) Effects of ultra-long-distance running on selected physiological and psychological parameters as a possible marker of overloading. Swiss Journal of Sports Medicine, 60(1): 21-5. Full Text

Cipryan, L., Stejskal, P., Bartakova, O., Botek, M., Cipryanova, H., Jakubec, A., Petr, M., & Řehova, I. (2007)  Autonomic nervous system observation through the use of spectral analysis of heart rate variability in ice hockey players.  Acta Universitatis Palackianae Olomucensis. Gymnica, 37(4): 17-21. Free Full-Text

Edmonds, RC., Sinclair, WH., and Leicht, AS. (2012) The effect of weekly training and a game on heart rate variability in elite youth Rugby League players. Proceedings of the 5th Exercise & Sports Science Australia Conference and 7th Sports Dietitians Australia Update. Research to Practice  Abstract

Ke-Tien, Y.(2012) Effects of Cardiovascular Endurance Training Periodization on Aerobic performance and Stress Modulation in Rugby Athletes. Life Science Journal, 9(2): 1218-25. Full-Text

Mateo, M. et al. (2012) Heart rate variability and pre-competitive anxiety in BMX discipline. European Journal of Applied Physiology, 112(1): 113-23.

Murray, N. P. et al. (2008) Heart rate variability as an indicator of pre-competitive arousal. International Journal of Sport Psychology, 39: 346-355.

Plews, DJ., Laursen, PB., Kilding & Buchheit, M. (2012) Heart rate variability in elite triathletes, is variation in variability the key to effective training? A case comparison. European Journal of Applied Physiology, 112(11): 3729-41.

Parrado, E.  et al. (2010)Perceived tiredness and HRV in relation to overload during a field hockey world cup. Perceptual and Motor Skills, 110(3): 699-713 Abstract

Sartor, F. et al. (2013) Heart rate variability reflects training load and psychophysiological status in young elite gymnasts. Journal of Strength & Conditioning Research, Published ahead of print.

Smith, T.B., & Hopkins, WG. (2011) Heart rate variability and psychological stress in an elite female rower who developed over-training syndrome. New Zealand Journal of Sports Medicine, 38(1): 18-20.

Thiel, C. et al. (2012) Functional overreaching in preparation training of elite tennis professionals. Journal of Human Kinetics, DOI: 10.2478/v10078-011-0025-x

Tian, Y., He, ZH., Zhao, JX., Tao, DL., Xu, KY., Earnest, CP. & McNaughton, LR. (2012) Heart rate variability threshold values for early-warning non-functional overreaching in elite women wrestlers. Journal of Strength & Conditioning Research, Published ahead of print

 

Psychological Considerations With HRV Monitoring

When I first started recording HRV measurements in August of 2011 I didn’t really know what to expect. I had no strategy for how I was going to interpret the data or put it to use practically. Other than reading Q&A posts from Landon Evans on elitefts, I didn’t know too much about HRV. All I knew was that it sounded interesting, logical and it was something cool to buy. I didn’t even own a compatible device to operate the app on so I bought an iPod touch.

Up until that point I was training religiously. Three weeks on followed by a one week deload. I didn’t miss workouts. I would try to hit my planned numbers at all costs. This method of training worked very well. I got big and strong training like this. Upon purchasing my ithlete device I kept my training structure the same and simply recorded HRV every morning. I decided to analyze the data later and see what I learned. Was I stronger when HRV was high? Was I weaker when HRV was low? What was HRV when I got hurt or sick? Etc. I ended up with 6 months of data of pre-planned training. I discussed my observations in this article.

Basically, I learned that with some simple modifications to my daily training plan, I might be able to see some benefits. I’d say the biggest benefit has been being able to back off the training when my body needs it rather than trying to assume. Pre-planned training failed to account for real life incidences that effect training. HRV monitoring also allowed me to better adjust training in response to illness, allowing me to maintain strength better upon return.

A common topic that arises when discussing the applications of HRV among colleagues is the potential psychological effects. What are they? How does this effect performance?

Here are some example scenarios with some brief thoughts;

  • HRV score is low and therefore you expect to feel weaker

–          In my experience I’m definitely weaker when HRV is well below baseline. But this is often because a well below baseline score happens; after an intense workout day; when I’m ill; when I perform a very different workout than I’m used to. I’ve found that moderately below baseline scores don’t typically affect my strength.  This may be different for you or your athletes. The simple solution would be to keep yourself or athlete blind from the HRV score for an observation period and see what you learn. However, the idea that HRV score can impact how you will perceive training is very real.

  • HRV score is high and therefore you expect to feel stronger

–          I can’t say that I’m stronger than normal when HRV is above baseline. But I’m certainly not weaker. This again should be tested during an observation period where the trainee is uninformed of HRV score. I must admit that upon seeing a good HRV score I immediately get excited. As if I have permission to train hard. Obviously my perceptions are influenced by my HRV score (based on my previous observations). We probably don’t want this happening with athletes. A good test for me might be to do another observation period. With what I know now about HRV I’m no longer impartial. Perhaps in the future I will test HRV blind for a month or two and see what happens.

  • HRV score doesn’t appear to make sense – something’s wrong with me, or the device

–          Something may be wrong with you or the device. Or, something may be wrong or inconsistent with your measuring procedure (position, you didn’t go to the bathroom first, disturbed measurement, etc). Additionally, you must consider all of the other factors that affect HRV. I wrote a post on many of these factors here. In short, you must factor in daily nutrition, training load, familiarity of training session, travel, caffeine intake, mental stress, etc. It isn’t just training load that can impact your HRV score.

–          Trouble shooting ideas: Check your pulse (on wrist) while recording the measurement to make sure the animated heart is in fact in synch with yours. Make sure the valid pulse indicator is green during the measurement. Make sure that you follow the breathing prompts consistently every measurement (This must be the same every time). Take several measurements in a row. If you do this keep in mind that successive measurements will change slightly (a few bpm and a few points on HRV) but they should be in the same ball park. Be careful when interpreting successive measurements. I find that I get a bit impatient/anxious when recording several in a row which will obviously effect HR.

–          If you measure standing (my preferred position) give yourself a minute to stabilize and let your heart rate adjust. Typically upon standing HR will jump up real high to account for the change in blood distribution requirements followed by a marked drop and then an evening out where it comes back up a bit. It may look something like this;

Lying down HR = 51

Standing HR (immediately after standing) = peaks at 102

Standing HR (after several seconds) =drops to 54

Standing HR (once stabilized) = 60

*These figures were made up based on what I recall from performing these tests

  • HRV score is low and therefore I might get hurt/perform terribly

–          One must keep in mind that come game day, athletes are typically experiencing some form of anxiety. This can be good or bad. Either way it can have a pretty big impact on HRV score that morning which will likely provide a skewed result. Therefore, game day measurements should probably be interpreted with caution. I’d prefer to keep the score from the individual so that it doesn’t mess with their head. Rate performance over time and see how it matches up with HRV. Studies have been done that have looked at this that I’ve discussed in several other posts. See what you find and how it compares. If you do please let me know what you find!

  • HRV score is low and therefore I’m overreaching, overtraining, etc

–          Again, all other factors must be considered when a score is analyzed. Probably the easiest measurement you can do to determine if one is in fact overreaching is to have them perform some performance tests like a vertical jump or grip strength. Additionally, assess their workout cards to see if their numbers are declining. If they are in fact over doing it performance will decrease with HRV.

Closing thoughts:

For the individual trainee: My best advice that I can give individuals who have an HRV device is to put yourself through an observation period. Try and measure your HRV blind and proceed with your normal pre-planned training routine (or whatever you typically do without the guidance of HRV). Try and document important events that may have effects scores in the “comments section” and keep a training log. It’s hard to analyze data based purely on memory. Having background knowledge of HRV before you use is it can be a blessing and a curse. You’ll likely have expectations or may already be impartial.

For monitoring athletes:  In team sport athletes, the less they know about HRV the better (in my opinion). If they can simply take their measurements and forward you the data that is all they need to know and do. If you can somehow manage to have them measure without seeing HRV score then that would probably be best. This will remove the psychological effects that can potentially occur.

In smaller teams and individual sports, this comes down to a judgement call based on your relationship with the athlete and their personalities. By the athlete knowing what their HRV means, how their lifestyle affects it and so forth, you may be able to get more “buy-in” to your program, guidelines, etc. Individual athletes are typically different than team sport athletes. An individual sport athlete typically takes more initiative, holds themselves more accountable, etc. They may respond to it by taking better care of their nutrition, sleep, reducing overall stress, performing active recovery and restoration modalities etc. The alternative would be to keep them vaguely informed and approach them the same way as the team sport athlete.

What’s your take on the psychological issues associated with HRV? What observations have you made? I’d like to hear about them. Let me know in the comments below or via e-mail andrew_flatt@hotmail.com