Monitoring Training, part 3: HRV

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Last week, we looked at the two branches of the autonomic nervous system (ANS) and how the stress response works. Having that basic understanding, we’ll now look at ways to monitor the state of your ANS to find the optimal amount of training for you.

First, a brief primer on overtraining: There is overreaching, and then there is overtraining. Overreaching is a short term state where you have pushed a little too long or hard. With a short rest or de-loading period, you’ll often be back to normal performance in a few days to a week. This is the most common form, as the body begins to give you all kind of signals that it wants a break at this point. Motivation drops, and many athletes choose to back off or find a reason not to train in this state. However, there are a number of strong-willed individuals that are able to override what their body is telling them and forge forward. This can lead to a full blown case of overtraining – now, it may be months if not years before a full recovery can occur. (and, that’s only with a drastic layoff and recovery protocol) Most won’t get this far down the overtraining path, but it definitely does happen – I’ve worked with quite a few over the years, guiding the long path back to health and performance.

To make it all even more confusing, there is sympathetic overtraining and parasympathetic overtraining. Recall from last week that the sympathetic nervous system (fight or flight) is active when the body is in an alarm state. In this type of overtraining, the stress response remains highly active because of excessive training or life issues. This type of overtraining is more common in strength, power, and speed athletes, but can definitely happen in Crossfitters. Common symptoms are irritability, restlessness, impaired sleep (difficulty falling asleep/frequent waking), weight loss (mostly muscle), poor performance, and loss of libido.

Then, there is parasympathetic system overactivity (rest and digest). In parasympathetic overtraining, the body is chronically trying to repair itself or in a state of exhaustion. Endurance athletes are more prone to this type, but this is common in Crossfitters because of the heavy endurance component. Symptoms are heavy fatigue, insomnia, no libido, chronic tiredness, low motivation, and low resting heart rate/blood pressure.

Basically, you don’t want to get to far to either side of ANS balance – you want both systems healthy and neither overactive or suppressed. We’ll now finally look at how to monitor the ANS to find that balance. With any of these methods, it’s best to get a baseline when you are rested – measure during a week’s rest from training. For the baseline to be valid, this can’t be a week where you substitute the stress of training for a big remodeling project or a tough week at work!

Heart Rate

Resting heart rate, taken first thing in the morning before getting out of bed, has a long history of use in sport. This is best done with a heart rate monitor. Track and record your heart rate daily, rest days too! Generally, the lower your resting heart rate, the more aerobically fit you are. If your resting heart rate lowers over time, it’s a good sign you are getting more fit. There are cases where a low resting heart rate is a sign of parasympathetic overtraining, though. If your resting heart rate is in the low 50s to upper 40s but you do not exercise or do aerobic training, chances are your system is already deeply “overtrained” just from life stress!

Common practice in training is that if you see an increase in your average heart rate of 6-8 beats per minute or more, then you may be headed into sympathetic overtraining. If you see a sudden increase of 6-8 bpm, examine what you did the prior day – you either did not tolerate the training well, or there were lifestyle and/or nutritional factors that interfered.

This method has some drawbacks, though. For one, the resting heart rate can vary quite a bit from day-to-day for many reasons. Secondly, you have to watch for a trend over time before it’s very useful. By the time you notice a definite trend, you are a full week into overtraining when it could have been caught sooner.

Orthostatic Heart Rate

This is a little more accurate and responsive test. With your heart rate monitor, first take your resting heart rate while lying supine. Then, stand and watch your heart rate climb; record the highest number. Your heart rate will then fall. Record where it comes to rest. A difference of greater than 8 bpm between your lying and standing heart rate (the 3rd measurement) suggests you are not recovered. Also, if your your heart rate peaks upon standing more than 15-20bpm above the supine reading, that is another sign of stress. If you use this method, track all three measures on a graph to see trends.

Cold Pressor Test

This isn’t one you’d likely do every day, but maybe periodically during different phases or types of training. This is described by T. Kurz in the “Science of Sports Training”. Place a bowl of water into your refrigerator, cooling it to 35-40 degrees F. Once it has cooled, sit down and relax comfortably with the bowl beside you. Wait 5 minutes for your heart rate to stabilize, then take the reading. Now, plunge one hand up to the wrist in the cold water and keep in there for 45 seconds, then take your new heart rate reading. The sympathetic system is functioning normally if your heart rate increases by up to 6 beats per minute. An increase of 10 or more beats per minute signals excessive sympathetic activity – either from overtraining, life stress, or both.

Heart Rate Variability

This is probably the best way to monitor the ANS. Heart rate variability (HRV) looks beyond the heart rate and instead looks at the intervals between the heartbeats. Contrary to common belief, your heart doesn’t beat regularly like a metronome. The heart rate constantly speeds up and slows down. If the sympathetic nervous system is more active, then there is less variation between the heartbeats – it becomes more metronome-like. HRV is low in this case. If the parasympathetic system is more active, then there will be larger differences between each beat. Here, HRV is high. Unlike resting heart rate, you’ll see an accurate difference in HRV each day depending on what you did the prior day, though trends are important here as well.

HRV technology was first developed by the Soviets in the 1960s to monitor the health of the cosmonauts. It was later used to monitor athletes for recovery. The technology came to the US where high-end units costing $35,000+ were created for use in high end professional or Olympic sport. As such, it wasn’t available to many athletes. In the last couple of years, the technology has evolved to the point where you can now use a smartphone app (along with your heart rate monitor) to track your HRV for a fraction of the cost. I’ve personally been using the Bioforce HRV unit to monitor my own training, plus I have a handful of athletes I coach using them also.

HRV screen

The app creates a graph where you can see day-to-day changes and trends. It gives you a rating of your state of readiness – a green for recovered and good to go; amber for moderately stressed; and red for under-recovered. I like this app not only for seeing how training has stressed the body, but also it lets you know exactly how much life stress is impacting you. It has been eye opening for some athletes – they’ll do a series of tough workouts and be only moderately fatigued on their HRV scores, but then one late night out and they get red-lined. I’ve noticed in my own monitoring that the biggest changes are almost always from life stresses.

You can use the information from HRV monitoring to learn how your body is responding to your training. Rather than having to guess when it’s time to take a de-load or week off, you’ll be able to see by watching the HRV trend. You’ll also be able to see when you are rested. Though I’ve been talking about using monitoring to avoid overtraining, it also can tell you if you aren’t training to your potential. As an example, I’ve found that I can actually train more frequently than I previously thought, and therefore have seen better progress. You can also gauge if certain practices help your recovery. For instance, if you know thru testing that a certain type of workout leaves your system heavily stressed the following day, test and see if doing a relaxed session of yoga later in the evening reduces the effect or not.

Next week, we’ll look at some miscellaneous methods of tracking recovery, then in the final installment I’ll go over some practical ways to use all of this information.

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