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Conducting Maximal and Submaximal Endurance Exercise Testing to Measure Physiological and Biological Responses to Acute Exercise in Humans
Published on: October 17, 2018
Delayed leukocytosis after hard strength and endurance exercise: aspects of regulatory mechanisms
Bjørn Audun Risøy1, Truls Raastad, Jostein Hallén
1The Norwegian University of Sport and Physical Education, Oslo, Norway. bjornaudun@hotmail.com
Background:
During infections, polymorphonuclear neutrophilic granulocytes (PMN) are mobilized from their bone marrow stores, travel with blood to the affected tissue, and kill invading microbes there. The signal(s) from the inflammatory site to the marrow are unknown, even though a number of humoral factors that can mobilize PMN, are well known. We have employed a standardized, non-infectious human model to elucidate relevant PMN mobilizers. Well-trained athletes performed a 60-min strenuous strength workout of leg muscles. Blood samples were drawn before, during and just after exercise, and then repeatedly during the following day. Cortisol, GH, ACTH, complement factors, high-sensitive CRP (muCRP), IL-6, G-CSF, IL-8 (CXCL8) and MIP-1beta (CCL4) were measured in blood samples. PMN chemotaxins in test plasma was assessed with a micropore membrane technique.
Results:
About 5 hr after the workout, blood granulocytosis peaked to about 150% of baseline. Plasma levels of GH increased significantly 30 min into and 5 min after the exercise, but no increase was recorded for the other hormones. No significant correlation was found between concentrations of stress hormones and the subjects' later occurring PMN increases above their individual baselines. Plasma G-CSF increased significantly - but within the normal range - 65 min after the workout. IL-6 increased very slightly within the normal range, and the chemokines IL-8 and MIP-1beta did not increase consistently. However, we found a significant increase of hitherto non-identified PMN-chemotactic activity in plasma 35, 50, and 60 min after the exercise. No systemic complement activation was detected, and (mu)CRP was within the reference range at rest, 5 h and 23 h after the exercise. After endurance exercise, similar findings were made, except for a cortisol response, especially from non-elite runners.
Conclusion:
Apparently, a multitude of humoral factors can - directly or indirectly - mobilize PMN from marrow to blood; some of the factors are, others are not known to be, chemotactic. Under different conditions, different selections of these mobilizers may be used. In the late granulocytosis after heavy, long-lasting exercise a number of factors thought capable of mimicking the granulocytosis of infectious diseases were apparently irrelevant.
Insights
Strenuous exercise mobilizes polymorphonuclear neutrophils (PMN) without clear correlation to stress hormones. An unidentified chemotactic factor in plasma appears to drive this late granulocytosis, distinct from infectious responses.
Area of Science:
- Immunology
- Exercise Physiology
Background:
- Polymorphonuclear neutrophils (PMN) are crucial for combating infections by migrating to inflammatory sites.
- The signals that mobilize PMN from bone marrow to blood during inflammation are not fully understood.
- Humoral factors are known to mobilize PMN, but their specific roles in non-infectious contexts require elucidation.
Purpose of the Study:
- To investigate the humoral factors and signals involved in PMN mobilization following strenuous, non-infectious exercise.
- To determine if known stress hormones or inflammatory markers correlate with exercise-induced granulocytosis.
- To identify potential novel PMN mobilizers or chemotactic factors in plasma after intense physical exertion.
Main Methods:
- A standardized strenuous strength workout was performed by well-trained athletes.
- Blood samples were collected pre-exercise, during, immediately post-exercise, and over the following day.
- Plasma levels of hormones (cortisol, GH, ACTH), inflammatory markers (CRP, IL-6), cytokines (G-CSF), and chemokines (IL-8, MIP-1beta) were measured, alongside PMN chemotactic activity.
Main Results:
- Blood granulocytosis peaked approximately 5 hours post-exercise, reaching 150% of baseline.
- Growth hormone (GH) increased significantly with exercise, but other measured hormones did not correlate with PMN increases.
- A significant increase in unidentified PMN-chemotactic activity was observed in plasma 35-60 minutes post-exercise, while G-CSF and IL-6 showed minor, within-normal-range increases.
Conclusions:
- Strenuous exercise induces a late granulocytosis, seemingly independent of major stress hormone fluctuations.
- An unidentified plasma factor with PMN-chemotactic properties appears to play a key role in this exercise-induced mobilization.
- The mechanisms of PMN mobilization during intense exercise differ from those typically associated with infectious processes, suggesting distinct signaling pathways.
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