The normal effects of exertion on the body

I thought it'd be good to have a thread to post research about exertion's effects on the body in healthy people, since any of these might relate to why exertion is harmful in ME/CFS.

This thread acts as a list. Please go to the individual thread for each article to discuss its contents.
If you want to add a research article to this list, please start a new thread to be used for discussion, and just link it from here.

 

Previously posted as its own thread:
Please go to that thread to discuss this research

Exercise-induced changes in high-γ cortical functional connectivity and short-interval intracortical inhibition

Matteo Conti, Federico Carparelli, Roberta Bovenzi, Valerio Ferrari, Battista Di Gioia, Nicola Biagio Mercuri, Alessandro Stefani, Maria Giuseppina Palmieri

Published: May 2025

Highlights
• Central fatigue is more challenging to study than the peripheral one, requiring more neurophysiological techniques.
• Ten healthy volunteers underwent HD-EEG and pp-TMS before and 24–72 h after a 3 km high-intensity run.
• After 24 h, a significant hyperconnectivity in the high-γ band and a consistent hyperexcitability in left M1 were observed.

Objective
To analyze exercise-induced changes in functional connectivity (FC) using high-density EEG (HD-EEG) and primary motor cortex excitability via paired-pulse TMS (pp-TMS).

Methods
Ten healthy volunteers performed a 3 km high-intensity run. Neurophysiological assessments were conducted at baseline (T0), 24 h (T1), and 72 h (T2) post-exercise. FC was measured using HD-EEG, and primary motor cortex excitability was assessed with pp-TMS to measure short-interval intracortical inhibition (SICI) and facilitation (ICF).

Results
At T1, a significant hyperconnected network in the high-γ band was observed in several brain regions, including sensorimotor, limbic, temporal, and occipital lobes, which normalized by T2. Additionally, pp-TMS revealed disinhibition (reduced SICI) in M1 at ISI 2–3 ms at T1.

Conclusions
The study highlighted specific features of exercise-induced central fatigue. Post-exercise, the primary motor cortex became hyperexcitable, possibly as a compensatory response to peripheral fatigue. A complex network of cortical areas involved in cognition and behavior was hyperactivated, likely reflecting awareness of fatigue and self-protection decision-making processes. These changes were reversible, allowing subjects to return to baseline conditions.

Significance
This research provides insight into the neurophysiological mechanisms of central fatigue, emphasizing the brain’s adaptive responses to intense physical activity and their temporal dynamics.

Link (Clinical Neurophysiology) [Paywall]

 

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Acute high-intensity exercise enhances T cell proliferation compared to moderate-intensity exercise

Jacob A. Siedlik, Jake A. Deckert, Amanda J. Dunbar, Anuja Bhatta, Nicole M. Gigliotti, Marcia A. Chan, Stephen H. Benedict, Matthew Bubak, John P. Vardiman, Philip M. Gallagher

Published: 13 March 2025

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Abstract
Conventional belief is that high-intensity (HI) exercise inhibits immune function; however, recent work challenges this position. The purpose of this was to quantify changes in T cell proliferative capacity following either a HI or moderate-intensity (MI) exercise.

Sixteen males were randomly selected to a HI or MI exercise group. Blood was obtained baseline and immediately, 1, 4, and 6 h post-exercise for analyses of CD3+ T cell proliferation (co-stimulation via phytohaemagglutinin or CD3 + CD28).

The proliferative response increased in T cells in the HI group and remained significantly elevated up to 6 h post-exercise in both co-stimulation conditions. In contrast, the MI group saw no change proliferative ability following exercise.

Analyses of serum stress hormones, and immunomodulatory cytokines failed to reveal any correlated variations that could clarify the T cell findings.

We suggest the increase in proliferative capacity following HI exercise is indicative of an exercise-induced activation that provides for enhanced functional responses to stimuli. Moreover, this study shows that HI exercise increases T cell processes, effectively priming them for activation in response to stimuli.

This study is registered with ClinicalTrials.gov (NCT06638684).

Link (Applied Physiology, Nutrition, and Metabolism) [Paywall]

 

Thanks, here is that study:

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Exercise Intensity and Recovery
Biomarkers of Injury, Inflammation, and Oxidative Stress

Bessa, Artur L.; Oliveira, Vanessa N.; Agostini, Guilherme; Oliveira, Renato J.S.; Oliveira, Ana C.S.; White, Gillian E.; Wells, Greg D.; Teixeira, David N.S.; Espindola, Foued S.

Published: February 2016

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Abstract
Biomarkers of inflammation, muscle damage, and oxidative stress after high-intensity exercise have been described previously; however, further understanding of their role in the postexercise recovery period is necessary. Because these markers have been implicated in cell signaling, they may be specifically related to the training adaptations induced by high-intensity exercise. Thus, a clear model showing their responses to exercise may be useful in characterizing the relative recovery status of an athlete.

The purpose of this study was twofold: (a) to investigate the time course of markers of muscle damage and inflammation in the blood from 3 to 72 hours after combined training exercises and (b) to investigate indicators of oxidative stress and damage associated with increased reactive oxygen species production during high-intensity exercise in elite athletes.

Nineteen male athletes performed a combination of high-intensity aerobic and anaerobic training exercises. Samples were acquired immediately before and at 3, 6, 12, 24, 48, and 72 hours after exercise.

The appearance and clearance of creatine kinase and lactate dehydrogenase in the blood occurred faster than previous studies have reported. The neutrophil/lymphocyte ratio summarizes the mobilization of 2 leukocyte subpopulations in a single marker and may be used to predict the end of the postexercise recovery period.

Further analysis of the immune response using serum cytokines indicated that high-intensity exercise performed by highly trained athletes only generated inflammation that was localized to the skeletal muscle.

Biomarkers are not a replacement for performance tests, but when used in conjunction, they may offer a better indication of metabolic recovery status. Therefore, the use of biomarkers can improve a coach's ability to assess the recovery period after an exercise session and to establish the intensity of subsequent training sessions.

Link (Journal of Strength and Conditioning Research) [Open Access]

 

S4ME thread: The effects of acute and chronic exercise on immune markers of TH1/TH2 cells in older adults: a systematic review (2025, Frontiers in Physiology)