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Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation
Open accessAbstract
Aim: To investigate the effect of carbon monoxide (CO) in the inspired air as anticipated during peak hours of traffic in polluted megalopolises on cerebral, respiratory and leg muscle oxygenation during a constant‐power test (CPT). In addition, since O 2 breathing is used to hasten elimination of CO from the blood, we examined the effect of breathing O 2 following exposure to CO on cerebral and muscle oxygenation during a subsequent exercise test under CO conditions. Methods: Nine men participated in three trials: (i) 3‐h air exposure followed by a control CPT, (ii) 1‐h air and 2‐h CO (18.9 ppm) exposure succeeded by a CPT under CO conditions (CPT COA), and (iii) 2‐h CO and 1‐h 100% normobaric O 2 exposure followed by a CPT under CO conditions (CPT COB). All exercise tests were performed at 85% of peak power output to exhaustion. Oxygenated (Δ[O 2 Hb]), deoxygenated (Δ[HHb]) and total (Δ[tHb]) haemoglobin in cerebral, intercostal and vastus lateralis muscles were monitored with near‐infrared spectroscopy throughout the CPTs. Results: Performance time did not vary between trials. However, the vastus lateralis and intercostal Δ[O 2 Hb] and Δ[tHb] were lower in CPT COA than in CPT. During the CPT COB, the intercostal Δ[O 2 Hb] and Δ[tHb] were higher than in the CPT COA. There were no differences in cerebral oxygenation between the trials. Conclusion: Inspiration of 18.9 ppm CO decreases oxygenation in the vastus lateralis and serratus anterior muscles, but does not affect performance. Breathing normobaric O 2 moderates the CO‐induced reductions in muscle oxygenation, mainly in the intercostals, but does not affect endurance.
Overview
CoChat Summary
TL;DR
In nine healthy men, breathing 18.9 ppm CO during constant-power cycling reduced vastus lateralis and serratus anterior oxygenation but did not change exercise performance time. Pre-exposure to normobaric O₂ moderated the CO-induced muscle deoxygenation, mainly in the intercostals, without improving endurance.
Key findings
- Performance time did not differ between control CPT (6:51 ± 1:28 min), CPT under CO (6:41 ± 1:39 min), and CPT under CO preceded by O₂ (6:52 ± 2:05 min; P > 0.05).
- Vastus lateralis Δ[O₂Hb] was lower in CPT CO_B (~25%) and CPT CO_A (~30%) than in CPT from 20% and 40% of performance time, respectively, until the end (P ≤ 0.05).
- Serratus anterior Δ[O₂Hb] fell more in CPT CO_A than in CPT and CPT CO_B at 60, 80, and 100% of performance time (P ≤ 0.05); Δ[tHb] was reduced in CPT CO_A vs CPT at 60 and 100%, and vs CPT CO_B at 100%.
- Cerebral oxygenation did not differ between trials, although cerebral Δ[HHb] was lower in both CO trials than in CPT (~42%) at peak exercise intensity (P ≤ 0.05). Blood lactate at termination was higher in CPT CO_A (13.5 ± 1.6 mM) than in CPT (12.8 ± 1.3 mM) and CPT CO_B (12.2 ± 1.3 mM; P < 0.001).
Methods
- Nine healthy, recreationally active non-smoking men (age 23.6 ± 3.0 years; VO₂max 51.3 ± 2.2 mL kg⁻¹ min⁻¹; PPO 357 ± 29 W) completed three counter-balanced trials separated by ≥48 h: 3-h air + control CPT; 1-h air + 2-h CO (18.9 ppm) + CPT under CO; and 2-h CO + 1-h 100% normobaric O₂ + CPT under CO.
- Exercise tests were constant-power cycle-ergometry at 85% PPO (mean 303 ± 24 W) to exhaustion. Near-infrared spectroscopy monitored Δ[O₂Hb], Δ[HHb], and Δ[tHb] in left prefrontal cortex, serratus anterior/intercostal region, and vastus lateralis.
- Analyses used one-way and two-way repeated-measures ANOVA with Tukey post hoc tests, plus Friedman and Wilcoxon tests for perceptual ratings; alpha was 0.05.
Limitations
- The paper states that NIRS cannot separate Hb and myoglobin contributions, subcutaneous adipose thickness may influence the signal, and NIRS reflects regional rather than global oxygenation.
- The paper notes that COHb was not recorded, so the presumed COHb threshold explanation is inferential.
- Evident from the text: the sample was small (nine men), participants were recreationally active but not formally trained, and the study examined a single pollutant rather than the pollutant mixture encountered in real urban environments.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“However, PETCO 2 and HR were significantly lower, and SpO 2 was significantly higher during the 1-h O 2 breathing period compared to baseline and CO exposure in EXP CO + O 2 (P < 0.001).”
§ Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation > Pre-exercise exposures
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“In the current CO trials, the respiratory muscle oxygenation showed a similar course to that of the leg muscle, as has also been noted in previous studies”
§ Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation > Muscle and cerebral oxygenation
plainstates an association- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The pre-exposure to normobaric hyperoxia did not change the pattern of the cerebral oxygenation during exercise.”
§ Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation > Cerebral oxygenation.
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“However, during the resting period, PETO 2 was significantly higher in the CPT CO B than in the CPT and CPT CO A , and PETCO 2 was significantly lower in the CPT CO B than in the CPT.”
§ Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation > Constant-power tests
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“However, [La] at the termination of exercise was significantly higher in the CPT CO A than in the CPT and CPT CO B (CPT: 12.8 Æ 1.3 mm, CPT CO A : 13.5 Æ 1.6 mm, CPT CO B : 12.2 Æ 1.3 mm; P < 0.001).”
§ Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation > Constant-power tests
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
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In the paper
§ Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation > Abstract
“There were no differences in cerebral oxygenation between the trials.”
§ Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation > Cerebral oxygenation.
“D[HHb] was significantly lower in the CPT CO A and CPT CO B than in the CPT ($42%) at peak exercise intensity (P £ 0.05) (Fig. 4b).”
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Metadata
- Authors
- Keramidas, M. E., Kounalakis, S. N., Eiken, O., & Mekjavic, I. B.
- Affiliations
- Jožef Stefan Institute (SI)
- Hellenic Military Academy (GR)
- KTH Royal Institute of Technology (SE)
- Corresponding author
- Keramidas, M. E.
- Venue
- Acta Physiologica
- Publisher
- Wiley
- Published
- 2011-10-31
- Volume
- 204
- Issue
- 4
- Pages
- 544-554
- ISSN
- 1748-1708 (ISSN-L)
- 1748-1716
- OpenAlex
- W1858286946
- Semantic Scholar
- 1be4f47cb402517832317120e26572044ec6fc1e
- Cited by
- 19
- References
- 44
- Citations by year
- 2026: 1 · 2025: 2 · 2024: 1 · 2022: 1 · 2021: 2 · 2020: 1 · 2019: 4 · 2017: 3 · 2015: 1 · 2014: 2 · 2013: 1
- FWCI
- 0.65
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Acta Physiologica (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Physiology (medical) › Cardiovascular and exercise physiology
- Health Sciences › Medicine › Physiology (medical) › Exercise and Physiological Responses
- Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Air Quality and Health Impacts
- Keywords
- carbon monoxide exposure, exercise performance, muscle oxygenation, cerebral oxygenation, hemoglobin oxygenation, vastus lateralis, intercostal muscles, endurance, air pollution, traffic-related air pollution
- MeSH terms
- Air Pollutants, Air Pollution, Brain, Carbon Monoxide, Humans, Male, Oxygen, Respiratory Physiological Phenomena, Exercise, Muscle, Skeletal, Young Adult
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