|It may sound like the invention of the heart rate monitor industry, but it's a matter of scientific "fact" that HRV analyses are a great tool to monitor and manage training and recovery.|
In the highly competitive world of the average iron-willed gymrat, it's however pretty rare that the gains ain't coming, 'cause he or she is under-training. I would guesstimate that the exact opposite is the case for at least 75% of the self-proclaimed hard-gainers. Overtraining, undereating and/or a lack of consistency are the stumbling blocks of 99% of the trainees.
I know that you know all that, ...
... so I'll cut this short and get right to the point. Within the past two weeks I hit upon two interesting papers that describe very different, but - in both cases - effective methods to determine whether you are overtraining, or not. While I originally wanted to tackle both in one article, I had to realize that the day has only 24h for my to write and you to read SuppVersity articles. Therefore, I decided to tackle heart rate variability monitoring today and postpone writing about the other to next week's follow up (stay tuned!).
I guess you may have heard about the usefulness of the latter on my buddy Carl Lanore's Super Human Radio, already and are thus familiar with the idea that your heart’s ability to produce fluctuations in the beat-to-beat interval in response to different situations. According to José Morales and his colleagues from the Laboratory of Sport Sciences a the Ramon Llull University in Spain,
The relationship between autonomic modulation and HRV is different during exercise and immediate recovery compared to rest periods. This makes the HRV a viable tool for the non-invasive assessment of the autonomic cardiovascular control and a comparatively objective measure of your training status (Camm. 1996; Seiler. 2007; Bosquet. 2008) .
"the use of heart rate variability (HRV) as a training tool has progressively increased and deserves attention as a tool to monitor the possible states of overtraining and recovery after a training process. [...] Several studies suggest that the quantification of HRV can be used as a non-invasive method for assessing autonomic cardiovascular control via the impact of HRV on beat-to-beat heart rate modifications." (Morales. 2013)
Don't turn into the guy on the left, don't overtrain & undereat | learn more
Hold on: What exactly is my HRV? Actually it's much less complicated than terms like fourier-transforms and frequency domain suggest. If you say "my heart rate is 60 beats per minute", this is an average you measured over a certain timespan. If you counted every beat for 60s, for example, the iterval between the beats probably was not exactly 1s. One beat may have been "premature", another took a little more than one second to finally come. The HRV is a measure for the variation in the time interval between heartbeats. In other words, if your heart beats 60 times per minute 24/7, your HRV would be zero and you're probably a cyborg ;-)The HRV responds particularly to heavy loads / intense workouts. The magnitude of the workout-induced stress is thought to be proportional to the activation of the sympathetic arm of the autonomic nervous system and thus the variations in autonomic balance, which can be indirectly assessed using HRV analysis (Seiler. 2007). A significantly lowered HRV days after a heavy workout is thus a signal that your central nervous system is still recovering. It tells you that you'd better insert a light cardio day or spend the time with friends instead of getting back onto the grind for another torturous 5x5 session.
Technology vs. psyche - HRV vs. RESTQ-Sport
Compared to psychological tests like the Recovery Questionnaire for Athletes (RESTQ-Sport), which is frequently used in research to observe the balance between stress and recovery during training processes, the physiological data you evaluate with the HRV method is obviously more objective. It is yet still debated whether it is also reliable and can / should replace or complement the classic psychological testing procedures.
|Table 1: Overview of the training weeks of the two groups (Morales. 2013)|
- high training load (HTL - 8 sessions per week ➙ short recovery periods)
- moderate training load (MTL - 4 sessions per week ➙ long recovery periods)
|Figure 1: A wide spread (green ellipse) of the poincare plot indicates full recovery.|
- the mean inter-beat (RR) interval,
- the standard deviation of the inter-beat (RR) interval ,
- the heart rate & its standard deviation
- the square root of the mean squared difference of successive RR intervals,
- the number of consecutive RRs that differed by more than 5 ms each, and
- the percentage of consecutive RRs that differed by more than 5 ms each
HRV + RESTQ-SPORT + HTL vs. MTL = reliable training analysis
The next thing they did was to to simply plot pairs of inter-beat intervals, e.g. 1/60 vs. 1/64, 1/64 vs. 1/76, etc. the resulting graph is a so-called poincare plot (see Figure 1) and the spread of the point in this graph can tell you whether you are well-rested (wide ellipse) or overtrained / need rest (narrow ellipse)
|Figure 2: Changes in selected HRV variables, left; performance, as well as stress + recovery values in the RESTQ-Sport, right; all differences expressed relative to values at the beginning to study (Morales. 2013)|
"The multivariate test indicated that there was an interaction effect between the testing time and group on HRV variables. [...] the HTL group showed lower square root of the mean squared difference for successive RR intervals, very low frequency, high frequency, short-term variability and short-range scaling exponent in the post-test than in the pre-test (p < 0.05). The HTL group showed higher low/high frequency ratio in the post-test than in the pre-test. Finally, there were no differences between the pre-test and post-test in the MTL group." (Morales. 2013)In other words: While the HTL group showed the expected increase in HRV, the judo players in the MTL group did not experience any significant changes in heart rate variability.
The question that remains - at least until you take a look at the data in Figure 2 (right) - is: Do these abstract figures really tell me that I am overtraining? The answer the comparison to the data from the RESTQ-Sport questionnaire gives us is YES, it does!
- Bosquet, L, et al. "Is heart rate a convenient tool to monitor over-reaching? A systematic review of the literature." British journal of sports medicine 42.9 (2008): 709-714.
- Camm, A. J., et al. "Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology." Circulation 93.5 (1996): 1043-1065.
- Morales, J., Álamo, J. M., García-Massó, X., López, J. L., Serra-Añó, P., & González, L. M. (2013). The Use Of Heart Rate Variability In Monitoring Stress And Recovery In Judo Athletes. Journal of strength and conditioning research/National Strength & Conditioning Association.
- Seiler, Stephen, Olav Haugen, and Erin Kuffel. "Autonomic recovery after exercise in trained athletes: intensity and duration effects." Medicine and Science in Sports and Exercise 39.8 (2007): 1366.