Getting a Good Nights Sleep By Using HRV

Researchers at the University of Salzburg, Austria and the University of California wanted to test the idea that if daytime heart rate variability (HRV) is strongly linked to physical and mental health, would HRV also be a predictor of healthy sleep?

Surprisingly, this has not been tested rigorously before, although HRV during sleep has been assessed in several previous studies.

This is a well-designed and thorough study that controlled the participants’ mental state before bedtime in a sleep lab and compared subjective sleep quality questionnaire results with gold standard polysomnography tests.

What did they do?
29 female subjects took part in the study which spanned over 11 days – one at the start for familiarization/screening and three actual study nights, each separated by a night at home.  A full-length emotionally neutral film about nuns going about their daily tasks was used to normalize the subjects’ mental state before sleep, and thereby minimize the impact of daily stressors. High frequency (i.e. parasympathetic) HRV was measured continuously during the film and used to establish the subjects’ baseline HRV that might predict sleep quality.

During the following nights, the subjects were comprehensively hooked up to ECG, EEG and sleep measuring equipment, from which normal sleep quality measures such as sleep time, delay in falling asleep, sleep efficiency, number of arousals etc. could be calculated. The participants also had to fill in a subjective sleep quality questionnaire. The researchers then looked at correlations between all the sleep indices and the HRV measured during the pre-bedtime movie.

They found significant correlations to daytime HRV for the following variables:

  1. Sleep latency (i.e. time taken to fall asleep)
  2. Number of arousals
  3. HRV during sleep
  4. Sleep questionnaire total score

A higher daytime HRV predicted a shorter time to fall asleep and less arousals during the night, as well as a better sleep questionnaire score. In contrast they found no significant relation to total sleep time or sleep efficiency (time asleep / total time in bed). Interestingly, HRV during sleep which had been studied previously, was only related to the sleep questionnaire score, and less strongly than with daytime HRV.

What does it mean?
Higher daytime HRV was associated with better subjective and objective sleep quality, and the authors go on to suggest that daytime parasympathetic HRV (i.e. HF or RMSSD) is associated with the flexible regulation of arousal.  This makes HRV a key marker once again, of internal processes, this time in the transition from wakefulness to sleep. This makes sense if we think about HRV as an indicator of parasympathetic rest and digest activity, and the counterpoint of the sympathetic ‘fight or flight’ state.  In a natural environment, animals would only fall asleep quickly and sleep soundly when they feel safe and are not stressed.

Practical implications
All of us who have used HRV for even a short while will have figured out that a good night’s sleep is one of the best ways to revive a low HRV score, but we also know that temporarily reducing our HRV through training workouts is a good way to stimulate the adaptations necessary to improve our athletic performance. These findings place more emphasis on recovery techniques that will get HRV as high as possible before bedtime to allow that all important sleep to be fully effective.

Here are some ideas to do this follow, but please also contribute your own thoughts too:

  1. Try to do intensive e.g. HIIT sessions as early in the day as possible so your HRV gets a chance to recover before bed
  2. Good quality nutrition and hydration (dehydration really stresses your system!)
  3. Cold showers / ice baths before bedtime are proven to increase HRV
  4. Deep breathing exercises increase HRV
  5. Avoid bright lights and LED screens before bedtime

Based on this and the previous post I could adapt the following routine to improve overall sleep time & quality:

  1. Aim to get to sleep by 10.30pm, being process of going to sleep at 9pm by turning off TV’s & devices
  2. Keep to set times for sleep, that is time to bed and time to wake. If I wake at 6.20 then to ensure 7 1/2 hours sleep I would need to be asleep by 10.30pm. In addition, if feeling drowsy after lunch then take a nap of between 30-60 minutes
  3. Between 9-9.15pm drink a cup of hot skimmed milk,
  4. Between 9.15-9.45pm take a shower and finish with cold water to raise HRV
  5. Between 9.45-10 do deep breathing exercises
  6. Between 10-10.30 and where needed, read a book before going to sleep
  7. At 10.30pm close eyes and go to sleep
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Review Weeks 1-7 Training Plan

A summary of what I have completed so far (TSS, distance):

  • Week one – 865, 215
  • Week two – 908, 204
  • Week three – 611, 162
  • Week four – 235, 85

In the above block I completed 3 active weeks followed by 1 recovery week

  • Week five – 300, 91 Mallorca
  • Week six – 325, 92 Mallorca
  • Week seven – 456, 94

My overall activity in weeks 5,6, and 7 was significantly reduced compared to weeks 1-4. On the rides in Mallorca I felt strong, especially on the long 70 miler. In week 7, on my return to UK I felt tired and did very few activities. On the last day of week 7, I did a Sunday Club ride and felt mentally and physically tired. How can I explain this fatigue given how fresh and strong I felt in Mallorca?

  1. Perhaps it is a result of heavy training in weeks 1-3 and not giving my body sufficient time to recover. Therefore, I was still carrying over fatigue from this initial period
  2. I was following a controlled diet up until week 3 but then I was unable to maintain it and felt compelled to eat. I followed by body’s response and began to eat more than I’d planned. In weeks 5 and 6 in Mallorca I ate freely. I ate high quality food and I consumed a large number of calories on a daily basis
  3. At about week 3 my weight went below 69kg and on my return from Mallorca my weight was 71kg and body fat 8%
  4. I’ve not been able to take HRV readings since week 4 because the iPad is not working so I’ve not been able to accurately gauge my body’s response to training. I really need to get this working so I can adjust my training plan to speed up recovery and return to more challenging training
  5. I am now in week 8 which includes the Exmoor Beauty sportive on Sunday. I’ll schedule recovery rides and get the iPad working. I’ll also return to controlling my diet

Recovery – How To Recognise & Respond

I’ve been giving rest & recovery some thought over the past few days and it is an essential and key component of my training programme.  I would argue is critical in terms of making performance progress. The main questions relating to recovery are:

  1. Why is it important
  2. How can it be recognised
  3. How often should it be scheduled and how long should it it last
  4. How can the bodies response to R&R be monitored and measured

The importance of R&R 

During training the body is over-stressed and if this continues without giving the body sufficient R&R then the body’s natural response is to invoke an illness or injury that will stop training in order to prevent any further damage. It is the body’s last resort mechanism to mitigate the damage caused by additional training workload. On the other hand, if appropriate R&R is scheduled, then the body will make adaptations to better manage these stresses the next time it encounters them. My own experience backs up the theory. When I have given sufficient time to R&R I have restarted my training feeling stronger and fresher.

Recognising the signs of overtraining

How do we know when we need to take a rest? – this should be pretty simple so why do we overtrain? I think the answer relates to a mistaken belief that the harder we train the stronger and fitter we get. This belief in turn overrides our own capacity to listen to our bodies for signs of overtraining. The signs are often evident but we simply miss them or ignore them. To make steady performance gains it is absolutely critical that we recognise the value of appropriately timed R&R. This belief must replace any pretensions that continual training overload will lead to performance improvements. Once we hold to this belief, then the becomes incorporating R&R as an essential component of our training programmes. Getting the balance right between overloading the body through training and giving the body time to adapt to training is a key skill. How do employ this skill and identify and recognise the signs of overtraining? As previously referenced we need to elevate our natural ability to read signs from our body as to when we start to encroach from overtraining into overreaching our bodies. The main signs of overtraining are

  • Fatigued – pretty obvious but one we often overlook
  • Irritability and bad mood
  • Skin changes – itchiness or lack of palor
  • Increasing mental fatigue
  • Low morale and motivation
  • Disruptive sleep patterns
  • Headaches and feeling sniffly
  • Elevated resting heart rate and depressed heart rate variability
  • Irregular hunger or thirst patterns
  • Irregular toilet patterns

In addition, to the above signs we can also monitor the body’s response to training by taking resting heart rate and heart rate variability measurements. Changes in the trends of either of these can provide invaluable insights into our bodies response to overtraining. The critical element of these measurements is to have recorded them over a sufficient time period to provide a trend or pattern. One-off measurements can not be relied upon.

How often should R&R be scheduled and how long should it last

Most training programmes provisioned by coaches or training web sites include rest and recovery weeks. Typically, a R&R week follows two or three weeks of training. In addition, rest and recovery days are included within the training weeks especially after demanding or ‘breakthrough’ training sessions. Unfortunately, this is not a precise mechanism and the body doesn’t always follow prescribed timescales. My own experience supports the need to schedule R&R but not to strictly adhere to it. Some flexibility is needed and programmes needed to be adjusted to reflect the body’s need for rest or continued training. Therefore, it is advisable to schedule R&R into a training programme and then to make adjustments were required.

I have been scheduling one week recovery weeks following two or three-week training sessions. During recovery weeks I would maintain frequency of activities but at reduced volume and intensity. Essentially, these activities have allowed the body to ‘tick over’ from a training perspective whilst the lower intensity has allowed the body to recover and adapt to the training stresses applied in the previous weeks. Over recent months, I have become more aware and responsive to signs of physical and mental fatigue. This is a skill that can be developed.

I have been using recovery rides between active training sessions and also during R&R as a means of balancing rest without training adaptations. My own theory is that recovery rides provide slow-twitch muscles with a low-level workout whilst fast-twitch muscle fibres get a complete rest, provided of course it is performed correctly, that is, at power or HR less than 50% of FTP or FTHR. Therefore, recovery rides are great for maintaining training of slow-twitch muscles whilst giving fast-twitch muscles a break. During the last R&R period I also used recovery rides to gauge my body’s recovery. On successive recovery rides I would slightly increase intensity or volume or both and measure my response to the increases. If the response was positive then I would increase it again, if negative then I would maintain the same level. HRV was very useful during this period as it allowed a ‘window’ into my body’s parasympathetic system to gauge how it was responding to rest and recovery. This methodical and objective approach minimises the risk inherent in using subjective cues to determine when to get back to full training.

Performance losses occur at three times the rate of performance gains so it is critical that we don’t spend more time resting and recovering than is required. Therefore, it is equally important that we recognise the signs of when we are ready to start training again in order that we can optimise the gains generated from previous training blocks.