Relationship Between Exercise-induced Oxidative Stress Changes and Parasympathetic Activity in CFS - (2018) Polli et al

[Sly Saint]

Relationship Between Exercise-induced Oxidative Stress Changes and Parasympathetic Activity in Chronic Fatigue Syndrome: An Observational Study and in Patients and Healthy Subjects

Email the author MSc Andrea Polli,Jessica Van Oosterwijck, PhD,Jo Nijs, PhD,
Uros Marusic, PhD,Inge De Wandele, PhD,Lorna Paul, PhD,Mira Meeus, PhD,Greta Moorkens, PhD
,Luc Lambrecht, MD,Kelly Ickmans, PhD

Abstract
Purpose
Oxidative stress has been proposed as a contributor to pain in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). During incremental exercise in patients with ME/CFS, oxidative stress enhances sooner and antioxidant response is delayed. We explored whether oxidative stress is associated with pain symptoms or pain changes following exercise, and the possible relationships between oxidative stress and parasympathetic vagal nerve activity in patients with ME/CFS versus healthy, inactive controls.

Methods
The present study reports secondary outcomes from a previous work. Data from 36 participants were studied (women with ME/CFS and healthy controls). Subjects performed a submaximal exercise test with continuous cardiorespiratory monitoring. Levels of thiobarbituric acid–reactive substances (TBARSs) were used as a measure of oxidative stress, and heart rate variability was used to assess vagal activity. Before and after the exercise, subjects were asked to rate their pain using a visual analogic scale.

Findings
Significant between-group differences in pain at both baseline and following exercise were found (both, P < 0.007). In healthy controls, pain was significantly improved following exercise (P = 0.002). No change in oxidative stress level after exercise was found. Significant correlation between TBARS levels and pain was found at baseline (r = 0.540; P = 0.021) and after exercise (r = 0.524; P = 0.024) in patients only. No significant correlation between TBARS and heart rate variability at baseline or following exercise was found in either group. However, a significant correlation was found between exercise-induced changes in HRV and TBARS in healthy controls (r = −0.720; P = 0.001).

Implications
Oxidative stress showed an association with pain symptoms in people with ME/CFS, but no exercise-induced changes in oxidative stress were found. In addition, the change in parasympathetic activity following exercise partially accounted for the change in oxidative stress in healthy controls. More research is required to further explore this link.

https://www.clinicaltherapeutics.com/article/S0149-2918(18)30611-8/fulltext

 

[Snow Leopard]

HRV is generally a poor choice for the measurement of vagal activity or parasympathetic/sympathetic balance, since it is affected by both...

However the fact that TBARS did not change after exercise is notable. Previous studies found elevated TBARS after maximal exercise...

 

[Amw66]

When was the sampling done?

Would it not have been useful to have testing done 24/48/72 hours later and compared?

Or have i simply lost the plot? .....

 

[ME/CFS Skeptic]

This is a Belgian study, so I had a quick look.

Like their previous publication (https://www.s4me.info/threads/exerc...s-a-secondary-analysis-2018-polli-et-al.6243/) this is a secondary aalysis, an additional analysis of a subset of participants from a study that has allready been published. (https://www.ncbi.nlm.nih.gov/pubmed/28339438) They only had data for 18 ME/CFS patients in this analysis, so all results should be taken with a grain of salt.

This research team focuses on pain. Here they wanted to study how pain in ME/CFS relates to oxidative stress (measured by the proxy Levels of thiobarbituric acid–reactive substances or TBARSs) and whether things changes after an (submaximal) exercise test.

The authors found that pain in ME/CFS patients was indeed related to oxidative stress while this was not the case in healthy controls. But oxidative stress was not higher in ME/CFS patients than in controls and exercise had no effect on oxidative stress in either group.

What did they did find is that in healthy people pain decreases after exercise while this was not the case in ME/CFS patients. There was no hypoalgesic effect in ME/CFS patients, a finding that has been reported previously (by this research group).

Oxidative stress was unable to explain this, but there were some interesting results for Heart Rate Variability (HRV), a measure of parasympathetic (vagal) activity. It decreased in ME/CFS patients after exercise but not in healthy controls.

Finally in healthy controls they found a relationship between HRV and oxidative stress. The higher the increase in parasympathetic activity during exercise, the more reduction in oxidative stress levels. So it seems that vagal activity normally exerts regulatory actions on oxidative stress during exercise, and that this was lacking in the ME/CFS group.

 

[Snow Leopard]

So it seems that vagal activity normally exerts regulatory actions on oxidative stress during exercise, and that this was lacking in the ME/CFS group.

The problem is that vagal activity cannot be directly inferred from HRV or HRV-High Frequency band, as both sympathetic and parasympathetic activity have an effect on the HF component.

Differences between patients and controls could simply be due to poor matching between patients and controls. Self-reported "sedentary" lifestyle of a healthy person doesn't necessarily mean they are matched.

There is much debate about this and simply avoiding reporting the commonly used LF/
HF ratio doesn't solve the problem.
https://www.ncbi.nlm.nih.gov/pubmed/12154170
https://www.physiology.org/doi/full/10.1152/ajpheart.2001.280.6.H2804

It's like measuring cortisol - just because it's easy, doesn't mean it's a good idea to rely on it in these sorts of studies.

Oh, and during exercise, parameters such as breathing/respiratory rate, heart rate and HRV changes tend to lag, rather than lead performance/effort perception, thus any increased sympathetic activity or altered parasympathetic activity is likely a response to the physiological challenge, rather than a cause of any difference in performance.