In today’s post I want to provide some research to support my bold claims about the effectiveness of HRV. The following research studies have been summarized to make more reader friendly as to not bore anyone who isn’t too interested in research methods, statistical analyses and so on. I have listed the citations for each study at the end for anyone interested in reading the research themselves. Additionally I have each one as a .pdf so just request a copy and I can send it.

HRV Reflecting Recovery status:

Chen et al (2011) found that HRV drops significantly within 24 hours of recovery from a high intensity strength workout in elite male competitive weightlifters and returns to baseline by 72 hours. Weightlifting performance was recovered exceeding baseline and reaching maximum at 72 hours thus showing a significant correlation between HRV and recovery.

Iellamo et al (2004) studied male rowers from the Italian national team during preparation for the world championships. The researchers found that from 50% to 100% of training load, there was a significant decrease in HRV and increase in sympathetic tone. As training reduced to 50% during the World Championships, HRV returned to base line and a return of autonomic indices to previous levels was seen. They concluded that monitoring of HRV can provide useful information to assess the dynamics of training through a simple non-invasive approach.

Pichot et al (2002) set out to test HRV as a practical and reliable marker of fatigue during training. 6 untrained subjects showed improved HRV during intense training. During overload training an increase in sympathetic activity was seen with a corresponding decrease in HRV. During a recovery week there was a sudden and significant rebound of parasympathetic activity and increase in HRV.

Research demonstrating better adaptation to training when HRV scores are high:

Hedelin et al (2001) found that endurance athletes who improved Vo2 max consistently showed higher HRV scores compared to athletes who showed deterioration in aerobic performance; of which showed lower HRV scores.

Kiviniemi and colleagues (2007) split 26 fit males into an HRV guided training group, a pre-planned training group and a control group. The HRV group was given intense training if HRV was the same as baseline or higher while moderate training or complete rest was given with significant drops in HRV. The pre-planned training group followed a pre-planned program typical of most endurance athletes. The results showed that HRV guided training produced a significantly greater increase in maximum velocity running compared to the pre-planned training group.

Kiviniemi et al (2010) conducted a very similar study to their 2007 work but in this case HRV groups were split in to a female group and a male group. The methodology was the same as the 2007 study where HRV groups performed training based on HRV scores while the pre-planned training group had pre programmed training. The results showed that men in the HRV group had greater maximum velocity than the pre planned group consistent with 2007 results. The HRV female group saw no significant increase in maximum velocity over the pre planned group. What’s interesting is that the HRV female group was able to improve their fitness to the same levels of the pre planned group with a lower weekly training load (fewer high intensity training days).

HRV predicting performance:

Cipryan et al (2007) showed that male hockey players have higher rated performances from their coach when HRV is high and that any drops in HRV correspond with a lower rating of performance. Of the sample players, the one with consistently low HRV was rated the lowest in performance. This demonstrates a strong correlation between HRV score and performance.

Devils Advocate

I should mention some research that shows HRV’s inconclusive ability to monitor training in attempt to be impartial. Bosquet et al (2008) performed a literature review to determine if HRV is effective at monitoring over-reaching. They determined that HRV should be used along with other known indicators and symptoms of overtraining to be meaningful. Additionally, Nigam (2010) concluded that HRV is more accurate than heart rate but not enough research exists to use either as a sole indicator of overtraining.

Edit: For more research on HRV see this post.

My Thoughts

It’s pretty evident that HRV can reflect recovery status. This has been demonstrated in both aerobic and strength athletes several times. This quality alone makes HRV worth monitoring if you are serious about your training. I’d like to see more research showing correlations with HRV and performance. Does having high HRV mean we can perform better on that day? Does low HRV doom us to substandard performance? The study on Hockey players is the only paper I found that would suggest this. I personally am not convinced. More research needs to be conducted on strength athletes in particular as this it is greatly lacking.

Grabbing the bull by the horns

Rather than complain that not enough research exists I thought I’d take matters into my own hands. I have proposed a research study to a researcher here at my university with the support of Bobby (the head strength coach) and Dr. Brian (Director of Athletic Performance) to compare HRV guided training vs. pre-planned training in collegiate football players this offseason. We will test 1 rep maxes in the big lifts before and after and see which group made the greatest improvements. This is basically copying Kiviniemi’s design except we are measuring strength performance in football players as opposed to running velocity in endurance athletes.

I’m happy to say that the department of athletic performance are all on board to conduct this research though there is still much to be done in acquiring valid instruments, getting approval from the IRB and so forth. Fingers are crossed that we can get it done. This is not part of my graduate program as I’m completing a course work based Master’s rather than a thesis based one. This research will be entirely out of personal interest on behalf of myself and the participating staff at the school.

In my next post I will display nearly 7 months worth of data from my own personal HRV scores. It will be much more interesting than this post I promise.

Thanks.

References

Bosquet, L., Merkari, S., Arvisais, D., Aubert, A.E. (2008) Is heart rate a convenient tool to monitor over-reaching? A systematic review of the literature. British Journal of Sports Medicine, 42(9): 709-714.

Chen, J., Yeh, D.,  Lee, J., Chen, C.,  Huang, C.,  Lee, S., Chen, C.,  Kuo, T., Kao, C., & Kuo, C. (2011) Parasympathetic nervous activity mirrors recovery status in weightlifting performance after training. Journal of Strength and Conditioning Research, 25(6):  1546-1552

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.

Hedelin, R., Bjerle, P., & Henriksson-Larsen, K. (2001) Heart Rate Variability in athletes: relationship with central and peripheral performance. Medicine & Science in Sports & Exercise, 33(8), 1394-1398.

Iellamo, F., Pigozzi, F., Spataro, A., Lucini, D., & Pagani, M. (2004) T-wave and heart rate variability changes to assess training in world class athletes. Medicine & Science in Sports and Exercise, 36(8): 1342-1346.

Kiviniemi, A.M., Hautala, A., Kinnumen, H., & Tulppo, M. (2007) Endurance training guided by daily heart rate variability measurements. European Journal of Applied Physiology, 101: 743-751.

Kiviniemi, A.M., Hautala A.J., Kinnunen, H., Nissila, J., Virtanen, P., Karjalainen, J., & Tulppo, M.P. (2010) Daily exercise prescription on the basis of HR variability among men and women. Medicine & Science in Sport & Exercise, 42(7): 1355-1363.

Nigam, A.K. (2010) Resting heart rate and overtraining in athletes. International Referred Research Journal, 2(21): 38-40.

Pichot, V., Busso, T., Roche, F., Gartet, M., Costes, F., Duverney, D., Lacour, J., & Barthelemy, J. (2002) Autonomic adaptations to intensive overload training periods: a laboratory study. Medicine & Science in Sports & Exercise, 34(10), 1660-1666.

Edit 03/25/2014: For a more in depth discussion on HRV click here

To open my discussion on HRV and its potential usefulness in athletes I would like to first highlight some of HRV’s most promising attributes.

1. HRV can help determine if and when one is overtraining
2. HRV can inform you when you are more adaptive to training and when you are less adaptive (telling you when to train hard and when to back off)
3. HRV can potentially predict if you will perform better or worse on a given day (I’m not sold on this yet)
4. HRV pretty accurately reflects recovery status

If you take your sport/training seriously, this information is extremely valuable. Throughout the next few posts I will do my best to fully explain what HRV is, how it works and from there we will discuss how to put it to use practically. I would also like to mention that HRV can be effective in both strength and endurance athletes. In fact, the majority of the research that exists on HRV has been performed on endurance athletes. So if you are a runner, cyclist, rower or all of the above, this blog may still offer useful information.

By now you might be wondering what the heck is HRV exactly? HRV is the measurement of time between each heartbeat. If you thought that the heart beats on a fixed rhythm you are incorrect. The time interval between each heart beat is highly variable. Specifically, we’re talking about the measurement of time between each R-R interval from an electrocardiogram (ECG) measurement. The variability in your heart rate provides critical information about the function of your autonomic nervous system (ANS). Typically HRV is measured on an ECG in a clinical setting. Fortunately, other more affordable and accessible devices exist that will measure your HRV (I will provide more info on these later).

What is the ANS and why is it important?

Here’s where the discussion turns a little more technical but bear with me. The ANS contributes to the body’s homeostasis by exciting or inhibiting cardiac muscle, smooth muscle and glands in response to subconsciously perceived visceral sensations (Tortora & Derrickson 2006). The ANS is comprised of two branches; the sympathetic nervous system (SNS) and the parasympathetic nervous system (PSNS). The easiest way to distinguish the differences between these two branches is to associate “fight or flight” responses with the SNS and “rest and digest” responses with the PSNS.

Sympathetic activity increases heart rate, force of contraction and blood pressure; increases blood flow to your muscles while decreasing blood flow to your gastrointestinal organs and releases sugar into the blood to provide energy to the working muscles. Adrenaline and glucocorticoid hormones are released to enhance these actions. In essence, the SNS responds to stress by providing the body with the resources and ability to move quickly to safety or to fight in response to danger. Think about anytime you’ve felt an adrenaline rush before a big sporting event or when someone scared you. That is your SNS being activated.

In contrasts, the PSNS does the complete opposite. In the absence of stress the body will reduce your heart rate and blood pressure; increase digestive processes and focus on the build up and repair of tissues (such as muscle) and storage of sugar (glycogen). In essence it recovers the body from any damage done during the stress response of the SNS.

Our SNS is activated when we train or compete. This is a good thing as it will enhance our ability to perform. However, intense training is extremely stressful on the body and requires sufficient recovery. It is important to understand that the acute response to a heavy strength training workout is actually weakened and damaged muscle tissue and a fatigued central nervous system. This is why we need to allow for sufficient recovery time to let the parasympathetic nervous system mobilize adaptive reserves and repair our muscle tissue and thus bring us to an increased level of strength.  An imbalance between sympathetic and parasympathetic activity can lead to reductions in performance and in severe cases, overtraining.

Enter HRV. HRV provides a non-invasive look at the function of our autonomic nervous system. If our body is still stressed from training it will be reflected in our HRV. Alternatively, if we are sufficiently recovered from training it will also be reflected in our HRV. Training intensely when HRV scores are poor would be counterproductive. When HRV scores are high, intense training will be well tolerated because adaptive reserves are high.

Keep in mind that it is not just training stress that the body must recover from. Any form of stress, be it mental or physical will use up adaptive reserves and elicit a stress response. Money problems, fighting with your significant other, moving to another city and so forth can all be extremely stressful on the body. HRV will be effected by any stressor making it all the more valuable to monitor. In future posts I will discuss how different non-training related events have significantly affected my HRV scores.

I will wrap this post up here as this can be a lot to swallow for anyone without a background in human physiology. In my next post I will discuss some research that supports the claims I made earlier about HRV.

Reference

Tortora, G. & Derrickson, B. (2006) Principles of Anatomy and Physiology 11^th Edition. Biological Sciences Textbooks Inc.