OK folks, this is a long one, so get comfy. I tried to keep it brief, but this topic is important because it’s something that has the potential to completely overhaul the way we train and you’ll likely hear more on this in the future…
How many times have you gone out for a run or a workout to realize that you just “don’t have it” on that particular day? How many times have you wondered if you’re overtraining because your times aren’t improving, you’re tired or moody? Alternatively, have you ever felt great and wondered if you can train even more than your training plan calls for?
Finding the right intensity, frequency and duration of training is really a bit of a crap-shoot for most of us, but there is some new technology which looks very promising for helping us out. It’s called Heart Rate Variability (HRV) and it refers to the varying intervals between heartbeats.
I am certainly no expert, so I enlisted the help of a friend of mine: Laura V. Weatley is a triathlete, professor and the Coordinator for the Exercise Physiology Lab at Illinois State University. She and her team are currently researching HRV in athletes.
Here’s how HRV works The amount of variability between heartbeats is an expression of the status of your nervous system and your overall health. No, I’m not talking about your heart rate. You’re heart rate is how frequently your heart beats. Conversely, HRV is the variability in the time gap between heartbeats which is an indication of the status of your nervous system. You want a high variability between beats
HRV is not only influenced by fatigue due to prior exercise sessions, but also hydration levels, stress, sleep (or lack of), nervousness, state of mood, hormonal status, drugs and many other factors.
Laura and her team explain:
” HIGH heart rate variability at rest is a GOOD THING. It indicates that there is a large time interval between heart beats, specifically in-between the R’s in the QRS wave. Most of us are aware that a LOW resting heart rate (beats per minute) indicates high cardiorespiratory fitness because the heart can produce a high cardio output (stroke x volume)…and fewer heart beats per minute mean that there is a longer time interval between heart beats. This equates to high heart rate variability!
Ali Lierman, a senior exercise physiology graduate student studying HRV elaborates:
“A low heart rate variability is NOT good. It indicates that the sympathetic nervous system is active. This can indicate stress and less-than optimal recovery.”
The SYMPATHETIC nervous system is great for getting us ready for activity (fight or flight)- it is responsible for increasing our heart rate, blood pressure, sweating, releasing glucose, and secreting hormones such as epinephrine, norepinephrine, and cortisol. HOWEVER, at rest, the autonomic system should be parasympathetic-dominant (resting and digesting).
The parasympathetic system allows our body to rest, rejuvenate and recover. It is responsible for digesting food, optimizing fuel storage and insulin sensitivity, and restoring/rebuilding our bodies and cells. A high heart rate variability at rest is parasympathetic-dominant, which is a good thing!
Mike Slack, exercise physiology graduate student studying HRV states,
“a high correlation of low HRV and overreaching/overtraining may likely be caused by the inability of that individual to “shut off” their stress response/sympathetic nervous system activity.”
So here’s the idea: You have your training plan as outlined by your coach, you follow this training plan, you measure your HRV every morning and adjust the training plan accordingly, along with the guidance of your coach. HRV is high? You can afford to work a little harder (you slacker!). HRV is low? You need to take it easy that day.
“The PROBLEM that we are encountering is that there are no set “standards” for “good” or “bad” HRV values. This is why we are monitoring athletes and looking at relative values…We are asking the athletes and their coach to give us feedback on the physical and mental stress levels and comparing them to their measured HRV values and athletic performance. We don’t know any universal “good” or “bad” numbers, but monitoring your PERSONAL HRV values over time and correlating them to stress and performance may be a strong tool for determining “athlete readiness.””
HRV has been used as a prognostic indicator in diabetes, heart disease, depression and many other conditions. I just did a Medline search on “heart rate variability” and found over 4,000 research papers on it. HRV is really nothing new, but it’s application for exercise training is just getting started. This is in large part because the expense of the equipment that is required just to record the data, add to that all of the calculations that need to be done to analyze and interpret the data and you’ve got a nightmare on your hands. However, this is changing…
Polar has a watch called the rs800CX which (from my understanding) records the data, but it costs $500. Suunto has the t6 which records and interprets the data but it is also $400. I have had difficulty finding info on the web to elaborate further. However, there is a new relatively inexpensive app for the iPhone/iPad called “ithlete” that also does it all for you (yes, there’s an app for that).
I asked Laura about the ithlete app:
“I personally have not used the ithlete app, but Mike Slack has. He says that, “ithlete seems to be a great tool for anyone wanting to measure their HRV. The great thing about ithlete is it’s any easy to use device that measures and TRACKS HRV. I emphasize tracks because if we don’t know our “optimal” HRV then we have to look at averages and daily fluctuations/trends. ithlete does this for you and gives you a daily, weekly, monthly trend and a recommendation of rest or decrease intensity/volume.”
Since HRV is influenced by stress at work or home, diet, sleep etc., you need to pay attention to these things. If your HRV is low, indicating you need to back off your training a bit, you need to account for all of these external training factors.
If you have any questions, please let me know. If I can’t answer them, I will forward them on to Laura and her team.