Chiropractic, Sports Performance, and the Autonomic Nervous System

For the past 4 years I have been merging two my passions in life: Chiropractic and the exciting world of sports performance. Remember the line from "Talladega Nights" where Ricky's dad said: "I am a semi professional race car driver and an amateur tattoo artist?" Well, I am a professional Chiropractor, a semi-mediocre weightlifter, and am amateur research reader.....

In studying Chiropractic and sports performance, I recognized that there is one overlying topic that seems to continually transcend both fields, and that is the role of the autonomic nervous system and adaptability. This blog will serve as a means of me "learning out loud" as I continue to study both of these topics and expand my own knowledge on the topic. I will review articles on here, share some ideas I have for research agenda, and talk about my two favorite things: Chiropractic and training.

In my quest to develop as a coach in the sport of Olympic Weightlifting, I began reading every book I could get my hands on in regards to coaching. I was reading books written by famous American coaches, online articles, even books translated from Russian to English that shared some of the methodology that the former Soviet lifters used to follow. One aspect of training that I hadn't really considered (I should emphasize that I never placed a conscious emphasis on it) was how much recovery was involved in the sport of weightlifting (or any strength/endurance sport for that matter). Nearly every book I got my hands on that talked about strength training dedicated a significant amount of text to the physiology of recovery. The best coaches in the sport viewed training in the context of how it would affect homeostasis in each individual athlete. Simply put, training is a physical stress which causes a departure from homeostasis, and recovery in between training sessions must allow the athlete to return to the previous state of homeostasis.

Chiropractors in practice often view recovery in the context of athletes purely in a musculoskeletal manner. We view biomechanics, range of motion, and subjective measurements of pain as the predominant means of how effective Chiropractic is for athletes. Don't get me wrong, anyone who has ever trained endurance sports or strength sports understands the importance of efficiency of movement and pain free range of motion, and I'm not taking anything away from that aspect of care; but I believe that as Chiropractors, our bread and butter needs to be in our understanding of the role of the autonomic nervous system. Wayne Gretzky was quoted as saying (I'm paraphrasing) that he was so good because "he always knew where the puck was going." Where is the puck going in terms of sports physiology and sports performance? Right where Chiropractors should want it to go, to the autonomic nervous system.

As I stated before, training for performance in any sport is a culmination of effort in the gym or track coupled with rest and recovery. If insufficient time, effort, and energy goes into the gym, it will be reflected in the results in competition. Likewise, if intense training is not matched by adequate recovery, then the athlete will experience maladaptation and performance will suffer and risk of injury, overuse, or overtraining becomes imminent. Match a sufficient training program which adequately stresses the athlete's physiology with recovery, and the athlete performs better in competition.

As much emphasis is being placed on recovery as the training program itself. More than ever, athletes are seeking out different recovery modalities to assist recovery, reduce inflammation, and to promote as much healing as they can in between training efforts. Recovery is JUST AS IMPORTANT as training. PERIOD.

Sort of interesting so far? It gets better. Any Chiropractor who has attended the Adaptability symposium in Chicago in the last few years, or anyone who has been paying attention to adaptability should pay close attention to what exercise physiologists are directing much of their research efforts to.

Athletic performance comes down to how well the athlete is able to adapt to a training load. Adequate adaptation=improved performance, inadequate adaptation=decreased performance. Balancing the two is key. The window to understanding adaptation? HEART RATE VARIABILITY and the AUTONOMIC NERVOUS SYSTEM. Coaches, athletes, and researchers are investigating the autonomic nervous system and it's role in recovery, and they are utilizing heart rate variability as the most accessible means of quantifying the recovery status of individual athletes.

A paper I recently came across was titled: "The Role of Heart Rate Variability in Sports Physiology," which was published in the journal "Experimental and Therapeutic Medicine" in Feb of 2016. The paper was a review of the literature which evaluated the role of HRV in assessing training adaptation/maladaptation of athletes and the relation of the HRV and ANS. Here are a few highlights which (I believe) are very relevant to Chiropractors:

-HRV is "an important method for assessing the cardiovascular autonomic parameters that are partially under the control of innervations from the sympathetic and parasympathetic systems."

HRV should be taught in Chiropractic school as an objective outcome measure. Every Chiropractor in practice has seen improvements in non-musculoskeletal conditions and HRV would be a fantastic way for us to quantify changes in the ANS as a result of a Chiropractic adjustment. There is a growing body of evidence inside and outside of Chiropractic looking at the effects of the adjustment (and spinal manipulation) on HRV. It's time we put more effort and energy into this field of study. Chiropractors recognize that the body is a self healing, self regulating organism, and that the nervous system is the "master control system in charge." HRV may be the best available tool we have to quantify that (which is exciting considering that sports physiology research seems to recognize the nervous system's self regulating capabilities as well). It is philosophically and scientifically congruent.

-"Additionally, in athletes, HRV monitoring is frequently applied to prevent and diagnose overtraining syndrome, which is associated with numerous syndromes such as ANS dysfunction and imbalance."

Note that the authors are looking solely at how the physiology the Autonomic Nervous System responds to training. I have seen a lot of papers which look at the role of the ANS in overtraining. Some have even gone so far as to say that overtraining and non-functional overreach (topics for future posts) are neurological disorders with endocrine repercussions due to the relationship between the ANS and the endocrine system. In endurance type sports like running and triathlon, athletes often exhibit signs of parasympathetic dominance (i.e. low resting HR, chronic fatigue, apathy towards training etc), where as in strength and fitness sports like weightlifting, powerlifting, and CrossFit athletes often exhibit signs of sympathetic dominance (ie. sleeplessness, high resting HR, increased respiration rate etc). Overtraining and non functional overreach are signs of maladaptation. Inability to recover and adapt to training load will decrease performance.

-"Findings resulting from multiple studies suggest that HRV parameters are relevant in the analysis of stress that the body experiences during training and to increase insight into physiological recovery after training."

Once again, the authors are focused on physiological recovery after training. A simple example that I use is a bodybuilder who is trying to increase the size of his or her bicep muscle. He/she will train the biceps incredibly hard on monday. We know that resistance training creates micro tears in the muscle being trained. With that in mind, it would be silly for the athlete to go back into the gym and train the biceps hard again the following day. The muscle must rebuild and recover or else it will not adapt and grow stronger. Obviously, in this example much of the recovery will occur localized to the bicep muscle and will be related to tissue repair, waste reduction, inflammation reduction, and protein synthesis. However, the athlete's physiology at large must recover as well. That is the role of HRV. In a sport such as olympic weightlifting or marathon running, it is the athlete's physiology that must recover in order to reach a point of super compensation and improved performance. We know that the spine and the autonomic nervous system are closely related anatomically and functionally. Some smaller studies have evaluated the effects of the adjustment on HRV and they have been promising thus far. We need studies with populations of athletes looking at how subsequent HRV changes post adjustment affect their recovery. Recovery is the realm that Chiropractic can make a large impact and gain even more inroads into sports and human performance, if we can just back off the pain train for awhile and focus some energy on the ANS and HRV.

In future posts I will explore more of the research related to this topic as well as some of the more exciting studies that we have in Chiropractic which have evaluated the response of HRV to the adjustment as well as other CNS/ANS related outcomes. In this post, I wanted to plant the seed of where I have been directing a lot of my energy over the past three years in studying this topic. Someday I hope to see studies with a large sample size of athletes undergoing intense training measuring HRV to see their responsiveness to Chiropractic and how that affects their recovery efforts. Until that day comes, I will continue to beat this drum and put these pieces together. There is a great deal of overlap in research related to sports performance and adaptability. As a profession, Chiropractic needs to begin to direct more resources to understanding how the adjustment (and subluxation for that matter) affect adaptability as measured through HRV.

1) Dong, Jin‑Guo. "The role of heart rate variability in sports physiology (Review)." Experimental and therapeutic medicine 11.5 (2016): 1531-1536.APA

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