In my last blog entry on stress, Carson Boddicker asked about some ways to quantify stress without getting to extreme. I offered a few “low-tech” methods which work very well and at the end of the article mentioned some of the more ”high-tech” methods that people can use when sufficient funds allow.
In the comments section of the blog article, track coach Carl Valle mentioned an app available for the iPhone or iPad to evaluate HRV called ithlete. I heard that they may be making one compatible with the Droid, however nothing for the Blackberry at this moment (which is unfortunate for me). This seems to be a reasonably priced product and cheaper than some of the Polar watches which can be used to measure HRV.
What is HRV and how can it be used?
Heart Rate Variability (HRV) is one method being used to evaluate the stress of the athlete and determine if they are in a more sympathetic or parasympathetic state, which would then guide the training program for that day.
HRV assess the interval of time between heart beats by measuring the time between R’s in a QRS wave. Having a high HRV corresponds with a high Vo2max, while having a low HRV can be an indicator of increased mortality and possible cardiac events. Additionally, when R-R intervals are plotted the frequency at which the length of time between them is measured – very low frequency power (VLFP), low frequency power (LFP), high frequency power (HFP) and finally a ratio of LFP to HFP. Different frequencies have different influences on both the parasympathetic and sympathetic nervous system.
In a nutshell, when HRV is high, this can be taken as an indicator of a parasympathetic state and being well rested. When HRV is low it suggest sympathetic domminance, high stress, and a potentially overtrained state. Additionally, it should be noted that parasympathetic activity is a major contributor to HFP, while LFP is often accepted as a marketer of sympathetic modulation (however, LFP has been debated in the literature with some suggesting that LFP is a paramater of both sympathetic and parasympathetic influences). Finally, when the ratio of LFP to HFP is high, this reflects sympathetic dominance.
If HRV is low, back off that day, lower the intensity and volume, or take an off-day and recover. If HRV is high, then training today is business as usual. Another interesting thing to evaluate is how well the athlete recovers following a high stress situation like competition. Athletes who are better conditioned will return to a parasympathetic state faster than those with poor conditioning. This information can be used to plan training the day after competition for individual athletes.
Trained athletes have higher HRV, HFP, and increased R-R interval times compared to untraied individuals. Additionally, as noted above, athletes who are in better condition are often able to recover at a faster rate following intense bouts of training and competition.
One thing that I would like to investigate in future articles is the influence that soft tissue therapy and manual therapy can have on HRV and promoting a more sympathetic state, as this has important implications to both recovery from training/competition and rehabilitation from injury.