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

VO2 Max, What is it Good For?

I’ve been doing some VO2 Max Hill Repeats over the past couple of weeks and I have noticed an improvement in my cycling, especially my climbing. Last week I went to watch the Tour of Britain up on Haytor. On the way back there was a big group of competent cyclists heading back to Exeter along the Teign Valley and Longdown. When we got to the start of the Longdown climb I was up the front with a Uni Exeter rider (Jack Holman) who is quite high up on quite a few of Strava’s KOM’s. Anyway, I paced myself up the climb keeping to about 320w. As we approached the 3/4 mark there were just two riders ahead of me, Jack Holman and a chinese looking bloke from the ‘Bad Lodgers’ club. I could see that they were slowing down and I was gaining on them. Just before the last corner near the top I went passed them both. I then got out of the saddle and sprinted a little bit before sitting down and completing the climb first!! Wey hey, monumental, well that is how I felt. My average power for the climb was 337w and this resulted in my best ever CP50 moving me into Cat 3 territory. Well chuffed.

Anyway, it struck me that the VO2 Max hill repeats I’d done a couple of days back had already returned an improvement in performance. The hill repeats I’d done were 3 x 5min @ 320w although I didn’t manage to complete the last of the three intervals and the average power for my final interval had only been 295w. I’d actually felt disappointed after that session because I believed that I could have given more if my glycogen stores were at 100% which I believed they weren’t because I’d been on a calorie reduction diet for about a week and had therefore depleted my glycogen stores. So, this got me thinking more about VO2 Max and I did a little research and this is what I have revealed so far:

  • VO2 Max is trainable but is also partly genetic
  • VO2 MAX is all about our capacity to deliver oxygen to the muscles
  • At VO2 Max we breathe heavily because of the heavy demand for oxygen being made by the body’s muscles
  • Muscles can process at least double the amount of oxygen they receive at VO2 Max. Therefore, it follows that if more oxygen can be delivered then the muscles can work harder and performance will subsequently improve
  • Improved breathing can increase the amount of oxygen being taken into the body. I already have a breathing tool which I can start to use to improve my capacity to take in more oxygen

The main physiological adaptations connected to VO2 Max are:

  1. Increased stroke volume/maximal cardiac output
  2. Increased muscle mitochondrial enzymes
  3. Increased lactate threshold
  4. Increased plasma volume
  5. Increased muscle glycogen storage
  6. Interconversion of fast-twitch muscle fibres (type IIx to type IIa)
  7. Hypertrophy of slow-twitch muscle fibres
  8. Increased muscle capillarisation
  9. Increased anaerobic capacity (lactate tolerance)

There appear to be a lot of benefits accruing from training VO2 Max and my own personal evidence is that it has a had a positive impact, primarily

  1. Delaying the onset of muscle fatigue and allowing me to push out more power for longer periods
  2. I am generating more power at a lower HR which means my speed at recovery, endurance and tempo is increasing but my HR is going down

So, how can I build on what I have learnt to optimise my training?

Need to do more research on the 9 physiological adaptations noted above. Which of these has a greater influence on performance and how can they be developed to increase performance gains?

I would make the following observations from my own training sessions:

  • It is taking longer for my muscles to fatigue – this could be due to increased numbers of mitochondria which are responsible for clearing lactate. The increase in mitochondria is probably related to the long period of endurance riding from January through to August, especially the once-a-week 70 or 80 mile rides. Mitochondria are developed in the slow-twich (ST) muscle fibres so it is plausible that the long base period was responsible for the increase in mitochondria and an increase in mitochondria improves the muscles ability to clear lactate.
  • My muscles are receiving more oxygen than previously so given my lower HR this is probably because my heart is pumping out a higher volume of blood per beat, ie., increased stroke volume
  • Anything blood related needs to take account of hydration – the more hydrated I am the more optimised the blood will be to carry oxygen to the muscles. If the blood becomes more viscous then the heart has to work harder to pump it around the body. My body water % has risen from about 64% a few months ago to around its current level of 67%. Water % may also have risen because muscle mass has increased but it is difficult to extrapolate any definitive conclusions regarding muscle mass as the data taken from the Body Mass Machine is up and down. Also, does body hydration increase with a decrease in body fat? This requires further investigation.
  • The higher water % may also suggest that glycogen storage has improved. The normal storage is 500g glycogen which carries with it 1.5kg of water. Therefore, as glycogen storage increases water % also increases. Each gramme of glycogen needs 3 grammes of water.
  • I am now not suffering from hunger pangs during the night which may suggest my body is less dependent on a constant supply of carbohydrate. How this specifically relates to VO2 Max I am not entirely sure but it may have some bearing following additional research so it is worth noting.

Next Goal for April & May 2013

I have successfully completed my last two goals so I now need to decide what is next? My main focus at the moment is completing my base training period which consists primarily of endurance riding, weight training and losing body fat. Base 2 (3 weeks) and base 3 (6 weeks) will complete my base training mesocycle – the end date for this is 26th May – therefore my next goal should cover April and May.

My base 1 training has been successful in improving my fitness and gettting me to focus on endurance riding, fat loss and weight training although the number of hours I originally planned to fit into each week was far in excess of what I could reasonably achieve based on my ability to recover from the training. Therefore, total hours needs to be revised down. I have completed between 60-75% of my training hours – therefore, I need to adjust down my total annual training hours. What I will do is aim for 75% of my weekly riding hours and 100% of my gym work (ie., 3 hours per week).

Base 2 – total riding 27.5 hours, total gym 9 hours

Week 1 – 19 hours; 16 (10 hrs) hours riding, 3 hours gym

Week 2 – 21 hours; 18 hours (11.5 hrs), 3 hours gym

Week 3 recovery – 10.5 hours; 7.5 hours (6 hrs), 3 hours gym

Base 3 – total riding 58 hours, total gym 18 hours

Week 1 – 20 hours; 17 hours (11.5 hrs), 3 hours gym

Week 2 – 22 hours; 19 hours (11.5 hrs), 3 hours gym

Week 3 recovery – 10.5 hours; 7.5 hours (6 hrs), 3 hours gym

Weeks 4-6 – repeat Base 3 weeks 1-3

Base 2 & Base 3; total riding hours 85.5, total gym hours 27 = total training hours 112.5 hours

Even on the reduced riding hours the total number of training hours I am committing to is double what I did in the last 2 months. This is a big increase and I will therefore need to pay close attention to how quickly I am recovering. it is also absolutely critical that I complete my endurance rides well within my endurance upper HR. If I go too high I could risk blowing my training. The challenge is to do the extra hours on the bike and also do the gym work too.

The other key goal is to reduce my body fat – according to current readings my body fat % is about 11.5-12%. This seems quite low already – having said that I still see fat deposits around my abdomen and my face is still a bit chubby. My overall weight is reducing but not my a massive amount so I can only assume I continue to build muscle mass although this has clearly been on my legs and not my upper body. My gym work will focus on building muscle mass on my chest, arms, lower back, shoulders, abdominals and lower back. How do I translate my fat loss and weight goals into figures. Lets look a the body composition figures:

Weight – approx 76.8kg at beginning of March and end of March approx. 75.5, a loss of 1.3kg. With training volume doubling I can expect a weight loss of around 2kg – my weight at the of base training should be approx 73.5kg (11st 8lb or 162 lbs). I need to pay close attention to my diet and stick to low fat and high protein. I also need to work out my diet precisely each week. After my base training is finished I will not be focussed on weight loss so it is now or never.

Fat loss – according to my readings my body fat has reduced from 14% to 11.7% over the course of March whilst muscle mass has increased from 62.2kg to 63.4kg. If I assume a muscle mass gain of 1kg per month, then I will gain 2kg in 2 months – muscle mass total will be approx 65.5 to 66kg. I’ll assume a 2% body fat reduction in the same period reducing total body fat % to under 10%. There has been no marked increase in muscle size but I now expect to record gains over the next two months as I increase muscle resistance in the gym.

Summary of Goal

For April and May I aim to complete my Base Training period by riding a total of 85.5 hours, by doing 27 hours of gym work. Over this period I aim to reduce my weight by 2kg to 73.5kg and reduce my body fat by 2 points to under 10% of my body mass. I will also commence breathing training using the Powerbreathe for the month of April. I’ll monitor progress using my Garmin, Body Composition Scales, and Measuring Tape. I won’t be using RunKeeper to analyse miles ridden – it is now about endurance hours. I will do a FTHR test at the end of April and May.

Better Breathing To Improve Performance

I have been thinking recently about how athletes from different sports who have very different physiques exhibit high performance. What is the common denominator of high performance of these elite athletes and how can a slim build athlete beat a more muscular and bigger competitor? I came to the conclusion that it must have a great deal to do with the cardio-vascular system. Elite athletes train their cardio-vascular system to outperform competitors and they build strength in this area over many years of endurance training. So, what are they actually training apart from the obvious one, which is the heart?

The heart is a muscle and with continued training it can be made stronger and therefore improve performance. What about the lungs, can they be made more efficient. Having started this train of thought I went online and did some research. I quickly came across the relatively new sports science of breathing for improved performance and Professor Alison McConnell. Having done a lot of research on the link between breathing and performance she concluded that the inspiratory breathing muscles (intercostal muscles found between the ribs) could be trained to improve performance. Having had my appetite whetted I bought her book, Breathe Strong Perform Better.

In her book she explains the benefits of training the inspiratory breathing muscles (the ones responsible for inhaling, taking the breath in). We cannot improve the amount of oxygen exchanged between the alveoli (little sacs that make up the lungs) and the blood capillaries – the main benefits arise because we delay the onset of a reflex that starts to send ‘tired’ messages to different parts of the body. This reflex is initiated by the brain when the brain receives messages from the intercostal muscles that they are getting tired. Therefore, Professor McConnell argues that if we strengthen these muscles then we delay the time it takes for the ‘tired’ messages to get to the brain. Sounds feasible and numerous studies reveal improvements in sports performance following a programme increasing strength of inspiratory muscles.

Having being sold on the theory I learnt of a simple inexpensive product developed by Professor McConnell that can be used to build strength of the inspiratory muscles. I bought the ‘Powerbreathe Plus’ product from Amazon and I have been using it for a a couple of days. I will now use it in conjunction with my cycling training programme and will monitor/assess its benefits.