Daily Heart Rate Variability before and after Concussion in an American College Football Player

Our latest paper is a case report demonstrating substantial changes in HRV following concussion in a college football player. The full text can be accessed here. The main findings were:

1: The post-concussion HRV trend appeared similar to trends commonly associated with training fatigue. Therefore, staff should investigate the possibility of an unreported concussion when similar trends are observed in athletes. 

2. Alterations in HRV persisted well beyond return to play clearance. This may have implications for clinical treatment and return to play considerations.

3. Since HRV demonstrated greater daily fluctuation post-concussion, isolated (i.e., single time-point) HRV recordings are likely inadequate for assessing persisting effects on the autonomic nervous system. Thus, near-daily HRV assessment may be required.

4. The convenient methodology used to monitor HRV (60-second finger-pulse plethysmography on a mobile application) can feasibly be implemented with an entire roster of athletes.

Abstract

This case report demonstrates the effects of sport-related concussion (SRC) on heart rate variability (HRV) in an American college football player. Daily measures of resting, ultra-short natural logarithm of the root mean square of successive differences (LnRMSSD), subjective wellbeing, and Player Load were obtained each training day throughout a 4-week spring camp and 4 weeks of preseason training. SRC occurred within the first 2 weeks of the preseason. During spring camp and preseason pre-SRC, the athlete demonstrated minimal day-to-day fluctuations in LnRMSSD, which increased post-SRC (LnRMSSD coefficient of variation pre-SRC ≤ 3.1%, post-SRC = 5.8%). Moderate decrements in daily-averaged LnRMSSD were observed post-SRC relative to pre-SRC (Effect Size ± 90% Confidence Interval = −1.12 ± 0.80), and the 7-day rolling average fell below the smallest worthwhile change for the remainder of the preseason. LnRMSSD responses to SRC appeared similar to trends associated with stress and training fatigue. Therefore, performance and sports medicine staff should maintain regular communication regarding player injury and fatigue status so that HRV can be interpreted in the appropriate context. Detection and monitoring of autonomic dysregulation post-SRC may require near-daily assessment, as LnRMSSD showed greater daily fluctuations rather than chronic suppression following the head injury.

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How to increase HRV: Part 2 – Nutrition

In Part 1 of this series I discussed inflammation and its relationship with HRV. Through monitoring my HRV daily I’ve learned that nutrition plays an important role in improving or reducing your adaptive capacity. Eating foods that promote inflammation in the body creates stress that your body must deal with. In dealing with this stress we reduce our ability to adapt and recover from training. Below is a screen shot of my HRV trend over a week of eating large amounts of foods commonly known to promote inflammation. You can see my scores drop each day and only return once I resumed eating better foods. This experience inspired this article series. To discuss the details of nutrition and inflammation I’ve recruited the help of my friend and PhD candidate Marc Morris.

Hi

My name is Marc Morris and I am a PhD student in Nutrition at the University of Saskatchewan. First, I’d like to thank Andrew for the invitation to participate in the discussion surrounding the use of heart rate variability and strength training. The utility of HRV in strength training is very interesting to me. Being a competitive powerlifter, I am always actively seeking ways to improve my training cycles. Truthfully, I don’t know a great deal about this measurement. What I do understand, however, is the potential that exists in a real-time measurement of the autonomic nervous system. Monitored on a daily basis, HRV may provide a tool from which we can objectively auto-regulate our training.

The goal of a dedicated athlete should be to maximize his or her adaptability to training. This is done in part by minimizing unnecessary stress on the body outside of training. From a nutritional standpoint, what you eat (or don’t) can play a significant role in your recovery and adaptability. This is what drew me to nutrition in the first place. Is it possible to improve my performance and body composition through what I consume? Your lifestyle plays a very big role in your training status and may very well be the difference in the transition from mediocre to elite.

We’ve always been told what you eat can effect performance (I’ve also learned that it’s a good idea to learn why you’ve always been told something on your own terms – usually these beliefs fall into the class of dogma). But, outside of eating complete junk and feeling like garbage, this is a tough concept to see and feel. It may not noticeably affect your body composition, it may not affect your energy, but it may be hindering your recovery. Chronic inflammation is not easy to “feel”. At least not until you’ve over done it.

My job today, and hopefully in future occasions, is to discuss how nutrition may influence inflammation, and what you can do to position yourself to be more adaptable in a training cycle. Andrew noticed a decreasing trend in his HRV over a week of entirely uncharacteristic eating (discussed here). This included plenty of processed foods, trans fats, refined carbohydrates and so on. These foods are common culprits of inflammation in the gut. Andrew felt well rested and rated his overall stress levels as low however his diet that week was creating an apparent stress that he couldn’t feel.

In Part 1, Andrew did a great job distinguishing what we know as acute inflammation, our body’s immediate response to injury and infection, and chronic systemic inflammation. As of late, “inflammation” has been a buzzword in most health circles. It has fallen victim to the black and white, all is bad classification. Chronic inflammation is a lingering, low-grade condition that has been linked to just about every health condition in the modern world, from heart disease to cancer. Managing this type of inflammation will help you not only avoid chronic disease in the latter half of your life, but could improve your performance now.

Health professionals may use biomarkers such as C-Reactive Protein (CRP, an acute inflammatory protein) and interleukin-6 (IL-6, a cytokine involved in the inflammatory response) to assess chronic inflammation (despite having a half life of 19-hours, CRP seems to correspond to the chronic condition pretty well). This may be suitable for someone that regularly visits the doctor. But, if you’re a healthy individual these tests will be costly and invasive (blood drawn). Additionally, this type of test won’t allow for an ideal frequency.

The most pronounced effect of diet on inflammation involves the essential fatty acids (EFA). Without going into too much of the physiology about this, the omega-3 and omega-6 fatty acids act as substrates in cascades that control inflammatory products (De Caterina and Basta, 2001 [free review]). Neither are bad, per se, however, the typical North American diet contains larger amounts of omega-6 that largely affect the pro-inflammatory pathway. This topic is so vast it deserves an entire blog post itself. The take home message would be: increase omega-3 intake to balance fats by eating fatty fish (or at least supplement with fish oil).

The ingestion of trans-fats have been shown to increase inflammatory markers, such as the aforementioned markers, CRP and IL-6 (Baer et al. 2004). To minimize low-grade chronic inflammation this would be a fatty acid to avoid (Calder et al. 2011). Foods such as pastries, doughnuts, margarine, and other snack foods commonly have high amounts of this unhealthy fat. So, apart from minimizing excess calorie intake, the high trans fat content of “junk” foods and its effect on inflammation is another reason to avoid these.

The last dietary factor I would like to address today would be alcohol. In small doses (1-2 drinks/day), alcohol has consistently shown to have an anti-inflammatory effect. Above this moderate dose, this effect changes to pro-inflammatory. So a glass of red wine every once in a while isn’t such a bad thing. However, going out and having 10 drinks will have some unwanted effects on your recovery (inflammation being only one of many negative effects).

It is important to acknowledge that not everyone is the same. Dietary choices may have a differing inflammatory response in each person. Having said that, below this article there is a chart of foods that are typically anti-inflammatory verses foods that are typically pro-inflammatory.

That’s it for today. In future posts, I’d like to address the macronutrient composition of the diet and the hypothesized mechanisms for dietary related inflammation.

Note: We are reluctant to categorize foods as in many cases it’s effect on the body is conditional. For example, lactose intolerant individuals will have a more adverse reaction to dairy than one who isn’t lactose intolerant. People with gluten sensitivity should obviously avoid gluten. So take this chart with a grain of salt as they are just intended to be generalizations.

Foods That Promote Inflammation

Foods That Reduce Inflammation

Pastries/Doughnuts Ginger
Margarine Tumeric
Dairy Onions
Gluten Garlic
Refined Wheat Products (breads, pastas) Citurs Peel
Peanuts Olive Oil
Hydrogenated Oils Organic, Grass Fed Meats
Vegetable Oil Wild Caught Fish
Grain/Corn Fed Meat and Fish Green Tea
Processed/Deli Meats Green Veggies (Broccoli, Kale)
Sugar Berries

Practical Applications:

  • Try and stick to grass fed meats and wild caught fish
  • Eat plenty of fruits and vegetables
  • Drink tea
  • Use spices and herbs when cooking
  • Use olive oil
  • Try to minimize refined carbohydrate sources

Note: We understand that eating this way isn’t entirely practical for students and busy folks. The key is simply to eat less of the foods you know may be hurting your progress and eat more of the ones you know will help.

References

De Caterina, R., Basta. G. (2001). European Heart Journal Supplements, 3 (Supplement D), D42–D49

Calder, P.C., Ahluwalia, N., Brouns F. et al. (2011). British Journal of Nutrition, 106, S3, 1-78.

Baer, D.J., Judd. J.T., Clevidence, B.A., et al. (2004). American Journal of Clinical Nutrition, 79, 969–973