Chiropractic: Investigating the Role of the ANS in Training and Recovery

Despite the many complexities of training in the sport of weightlifting (and pretty much every other strength or endurance sport), the main premise is pretty simple. Gradually increase the training stress and training load over a period of time, allow the body adequate means to recover and ADAPT to the stress, introduce taper and de-load periods, and at the end of the program or cycle and the athlete enters competition they should be set up for improved performance. Despite this relative simplicity, there are numerous variables to account for including stress of life, what percentages (intensity) to program, how often the athlete trains (frequency), and how long the individual training sessions are (volume).

Programming for the athlete can be incredibly complex and open to a lot of individual interpretation and application, but one aspect persists, in order for ultimate success in sport the athlete must be allowed to adapt and recover following individual training loads. If the athlete fails to adapt, or maladapts, to training stress performance will suffer as the result.

Several years back when I first began looking into the topic of recovery, my sole interest was related to the role of the nervous system. Physiologic adaptation occurs through the autonomic nervous system, and is at the center of much research in the field of pathology and salutogenesis. Being that I am a Chiropractor first and foremost, I tried to approach this topic through a Chiropractic lens. After numerous searches using keywords like “recovery and nervous system,” I came across a study that examined the role of the autonomic nervous system and recovery geared towards a population of weightlifters.

The study was titled “Parasympathetic Nervous System Activity Mirrors Recovery Status in Weightlifting Performance After Training,” and was published in the “Journal of Strength and Conditioning Research” in 2011.

The researchers put 7 male weightlifters with national or international competition experience through a 2 hour training protocol of back squat, shoulder press, deadlift, and front squats. Athletes then rested under “sedentary conditions” for 72 hours. Heart rate variability measurements and blood marker measurements were taken at 3, 24, 48, and 72 hours post training session. Blood markers measured were creatine kinase levels and DHEA-s. DHEA-s is a hormone produced in the adrenal glands which the body converts into testosterone, and creatine kinase is used as a marker of muscle damage.

CK levels were elevated post workout and didn't return to baseline by the end of the 72 hour period, and DHEA-s levels dropped below baseline and remained low, and subjectively reported levels of muscle pain were elevated 72 hours post training.

HRV high frequency values (generally considered to be indicative of parasympathetic nervous system activity) dropped below baseline within the first 24 hours but returned to baseline by the 48 and 72 hour mark. Weightlifting performance was tested again at regular intervals and was found to return to baseline by the 72 hour mark.

Despite the biochemical markers not returning to baseline, the performance improvements correlated with a plateau in the HRV reading indicating the parasympathetic NS activity marked recovery status and performance.

A few notes of relevance to Chiropractors:

-“In contrast to the endocrine system, the autonomic nervous system is a fast component of signaling system controlling the whole-body metabolic homeostasis by coordinating different organs and tissues, aimed to precisely match oxygen demand and supply in response to external challenges.”

Chiropractic principle 32: The Principle of Coordination: “Coordination is the principle of harmonious action of all the parts of an organism, in fulfilling their offices and purposes.” I’m always thrilled when I come across contemporary science that supports the Chiropractic principles first espoused in Stephenson’s text from the 1920’s. Chiropractors recognized the importance of the nervous system and it’s role in homeostasis dating back to the turn of the last century. Homeostasis is incredibly important to athletes (as well as the general population obviously, but this article is in the context of athletes). Training stress leads to a disruption in homeostasis, recovery from an individual training stress marks a return to a homeostasis. Are you seeing the trend? The authors of this paper note the importance of the ANS and measuring the ANS for determining how the body responds to external challenges……sound familiar?

-“Increasing resting sympathetic nervous activity with reciprocally de- creasing resting parasympathetic nervous activity reflects an elevated oxygen demand for ATP generation in the periphery, which typically occurs during and after external challenge.”

Again, note the importance the authors place on the roles of the sympathetic and parasympathetic nervous system in the context of markers that are important to athletes such as ATP generation and oxygen demand.

-“Furthermore, the strength recovery and parasympathetic nervous activity appear to be unrelated to pain and circulating muscle CK levels.”

This is the first time I’ve seen something like this in a study but I think it can have some very important clinical applications. Often times, health care practitioners in many different fields tell people to listen to their body and soreness levels etc. In this study, they showed that pain and CK levels appeared to be unrelated to subsequent performance. Very interesting, but we should also keep in mind that the 7 people in this study were high level weightlifters.

-“Our data provide evidence that parasympathetic power mirrors recovery status in weightlifting performance after training.”

Very simple: activity of the nervous system mirrored recovery. Sure we can point out that this study was N=7, but keep in mind that this is one study in a sea of many that have come out since. I will expand on more of these papers in future posts.

-“In conclusion, HRV is a noninvasive tool that can be used by coaches to monitor recovery status from fatigue for a weightlifter during the training period and before competition.”

Just like I said in the last post, it’s time that HRV becomes a standard in Chiropractic schools and practice. A paper published in 1999 laid out the rationale for assessing HRV as an objective way to monitor autonomic response to care, and several smaller studies have come out in the past decade substantiating that notion.

This is an incredibly broad topic, and I’ve only just begun to scratch the surface.

1) Chen, Jui-Lien, et al. "Parasympathetic nervous activity mirrors recovery status in weightlifting performance after training." The Journal of Strength & Conditioning Research 25.6 (2011): 1546-1552.APA

2) Eingorn, Alex M., and George J. Muhs. "Rationale for assessing the effects of manipulative therapy on autonomic tone by analysis of heart rate variability." Journal of manipulative and physiological therapeutics 22.3 (1999): 161-165.APA

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