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A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation
Open accessAbstract
Background: Altitude training stimulates erythropoietin hormone (EPO) release and increases blood hemoglobin (Hb) mass, which may result in improved oxygen (O2) transport capacity. It was hypothesized in the present study that periodic inhalation of carbon monoxide (CO) might elicit similar physiological adaptations compared to altitude training. Methods: Twelve male college student athletes, who were well-trained soccer players, participated. They performed a four-week treadmill-training program, 5 times a week. Participants were randomly assigned into an experimental group with inhaling CO (INCO) (1 mL/kg body weight for 2 minutes) in O2 (4 L) before all training sessions and a control group without inhaling CO (NOCO). CO and EPO concentrations in venous blood were first measured acutely at the 1st, 2nd, 4th, 6th, and 8th hour after INCO, and total hemoglobin mass (tHb), running economy and VO2max were measured before and after the four weeks training intervention. Results: HbCO% increased from 0.7 to 4.4% (P<0.05) after 1 h of CO inhalation and EPO increased from 1.9 to 2.7 mIU/mL after 4 h post CO inhalation (P<0.05) acutely before the intervention. After the training, the tHb and VO2max in the INCO group increased significantly by 3.7 and 2.7%, respectively, while no significant differences were observed in the NOCO condition. O2 uptake at given submaximal speeds declined by approximately 4% in the INCO group. Conclusion: Acutely, EPO increased sharply post CO inhalation, peaking at 4 h post inhalation. 4-weeks of training with CO inhalation before exercise sessions improved tHb and VO2max as well as running economy, suggesting that moderate CO inhalation could be a new method to improve the endurance performance in athletes.
Overview
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TL;DR
In 12 well-trained male soccer players, periodic inhalation of a low dose of carbon monoxide before treadmill training increased erythropoietin acutely and improved total hemoglobin, VO2max, and running economy after 4 weeks. The authors propose CO inhalation as a practical sea-level method to mimic some altitude-training adaptations, while emphasizing safety and the need for further research.
Key findings
- Acute CO inhalation increased blood HbCO% from 0.7 to 4.4% after 1 h and raised serum EPO, which peaked at 4 h post inhalation at 2.7 mIU/mL, an increase of 42.1% from baseline.
- After 4 weeks, the INCO group significantly increased tHb by 3.7%, RCV by 5.3%, PV by 6.8%, and BV by 6.2%; the NOCO group showed no significant changes.
- VO2max increased significantly in INCO by 2.4% absolute and 2.7% relative, while NOCO showed no significant change (0.1% relative).
- O2 uptake at submaximal running speeds of 8, 10, and 12 km/h declined significantly in INCO by 3.7, 3.6, and 5.4%, respectively, indicating improved running economy; RBC, Hct, Hb, and MCV did not differ significantly pre- to post-training.
Methods
- Twelve healthy young adult male soccer players from Beijing Sport University, living at low altitude, non-smokers, with more than 10 years of sport training, were randomly assigned to INCO (n = 6) or NOCO (n = 6).
- The study had an acute phase measuring exhaled CO, blood HbCO%, and EPO before and at 1, 2, 4, 6, and 8 h after one CO inhalation (1 mL/kg body weight in 4 L O2 for 2 min), followed by a 4-week treadmill-training program five times per week, 50 min per session, with CO or O2 inhaled 15 min before each session.
- Outcomes included EPO by ELISA, HbCO and exhaled CO, tHb and blood volumes by CO-rebreathing, VO2max by incremental treadmill test, and running economy at 8, 10, and 12 km/h; analyses used repeated-measures and 2-way ANOVA with Student-Newman-Keuls post hoc tests, P < 0.05, and effect sizes.
Limitations
- The paper states that the sample was small and included only football players, so findings should be extended to larger groups and other sport disciplines.
- The paper states that CO breathing can be dangerous and should only be performed in a well-controlled laboratory with close monitoring of exhaled and blood CO and access to first aid.
- The paper also notes that no direct comparison to altitude training was performed, CO clearance during exercise was not determined, and mechanistic explanations for improved running economy remain speculative; the text does not report blinding of participants or assessors.
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0 Valid · 0 Not valid · 1 Not checked · 28 Own results and interpretations
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 VO2max in the INCO group was significantly higher (P < 0.05) post-training when compared to the NOCO group.”
§ A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation > Results > Maximal Aerobic Power After 4 Weeks of Training
plainn = 6 ·- 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
“Post-training, a significant (P < 0.05) increase was observed in tHb (3.7%, ES = 0.76), RCV (5.3%, ES = 2.14), PV (6.8%, ES = 6.34), and BV (6.2%, ES = 39.45) in the INCO group.”
§ A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation > Results > Exercise Training and CO Inhalation
plainstates a causen = 6 ·- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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- 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
“After the training, the tHb and VO2max in the INCO group increased significantly by 3.7 and 2.7%, respectively, while no significant differences were observed in the NOCO condition.”
- Also stated in: § Exercise Training and CO Inhalation · plain
“Post-training, a significant (P < 0.05) increase was observed in tHb (3.7%, ES = 0.76), RCV (5.3%, ES = 2.14), PV (6.8%, ES = 6.34), and BV (6.2%, ES = 39.45) in the INCO group.”
- Also stated in: § Discussion · plain
“increased subjects’ tHb (3.7%), plasma (6.8%), and whole blood volume (6.2%), VO2max (2.7%), and running economy (4%).”
§ A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation > Abstract > Results
plainstates a causen = 6 ·- 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.
- Also stated in: § Exercise Training and CO Inhalation · plain
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
“O2 uptake at given submaximal speeds declined by approximately 4% in the INCO group.”
- Also stated in: § Maximal Aerobic Power After 4 Weeks of Training · plain
“At submaximal running speeds (8, 10, and 12 km/h), absolute/relative O2 uptake of both the INCO and NOCO group appears to be lower post-training, as shown in Table 5. However, the decrease was only significant in the INCO group (3.7, 3.6, and 5.4%, ES = 0.61, 0.48, and 0.63, respectively) (P < 0.05).”
§ A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation > Abstract > Results
plainstates a causen = 6 ·- 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.
- Also stated in: § Maximal Aerobic Power After 4 Weeks of Training · plain
A result the paper states — it cites no source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Inhalation of CO (1 mL/kg BW) in normoxia stimulates EPO secretion in well-trained male soccer players.”
§ A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation > Conclusion
plainstates a cause- Asserted: passes — The authors put it forward as true.
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Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
In the citing paper
“Periodic inhalation of carbon monoxide (CO) at rest has been shown to mimic the effects of hypoxic training (Wang et al., 2019) and living at high altitude (Schmidt et al., 2020), with additive benefits when combined with natural high‐altitude exposure (Urianstad et al., 2024).”
From Effect of live‐high, train‐low strategy induced by chronic low‐dose carbon monoxide exposure on haematological parameters and performance in trained individuals (2026) · cites this paper as Wang et al., 2019
In the citing paper
“For example, the lack of statistical indicators (i.e., lack of information on main- and interaction effects), as in the study by Wang et al. (2019), could call into question the true effect of the application, at least when combined with exercise.”
From Low-dose carbon monoxide inhalation to increase total hemoglobin mass and endurance performance: scientific evidence and implications (2024) · cites this paper as Wang et al., 2019
In the citing paper
“Wang et al. reported that inhaling a CO bolus (1 mL/kg body mass) five times a week prior to treadmill training increased tHb-mass by 3.7% in trained soccer players (VO2max 58 mL/min/kg), although a 2.8% increase was also observed in the control group (Wang et al., 2019).”
From Low-dose carbon monoxide inhalation to increase total hemoglobin mass and endurance performance: scientific evidence and implications (2024) · cites this paper as Wang et al., 2019
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Rated minor: it would not touch a result — a value no result rests on, a p-value that stays on the same side of the significance level, or a conflict that is clerical, resolved elsewhere in the paper, or outside its own findings.
In the paper
“| Hct (%) | 0.41 ± 0.02 | 0.42 ± 0.01 | 0.50 | 0.42 ± 0.02 | 0.42 ± 0.03 | 0 |”
§ A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation > Results > Exercise Training and CO Inhalation
Reported 0.41 · recomputed 41.443773
Rated minor: it would not touch a result — a value no result rests on, a p-value that stays on the same side of the significance level, or a conflict that is clerical, resolved elsewhere in the paper, or outside its own findings.
In the paper
§ A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation > Conclusion
“Inhaling 1 mL/kg CO prior to training sessions (five times/week for 4 weeks) increases PV, BV, RBC, tHb, running economy, and VO2max post-training”
§ A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation > Results > Exercise Training and CO Inhalation
“There were no differences between pretest and posttest in RBC, Hct, Hb, and MCV.”
Cited works that were retracted
Works this paper cites that were later retracted, from the retraction notices publishers deposit. Major when the notice came out before this paper was published.
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In the paper
“Suliman, 2007, A new activating role for CO in cardiac mitochondrial biogenesis., J. Cell Sci., 120, 299, 10.1242/jcs.03318”
Cited work 10.1242/jcs.03318 · retraction date not known · this paper published 2019-06-06
Citations
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1 retracted
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Cited by
Chronic Exposure to Low-Dose Carbon Monoxide Alters Hemoglobin Mass and V˙O2max
SCHMIDT, W. F. J., HOFFMEISTER, T., HAUPT, S., SCHWENKE, D., WACHSMUTH, N. B., & BYRNES, W. C. (2020) · Medicine & Science in Sports & Exercise · doi:10.1249/mss.0000000000002330 · Cited by 39
The relationship between hemoglobin and V˙O2max: A systematic review and meta-analysis
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Compelling Evidence: A Critical Update on the Therapeutic Potential of Carbon Monoxide
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Metadata
- Authors
- Wang, J., Ji, Y., Zhou, L., Xiang, Y., Heinonen, I., & Zhang, P.
- Affiliations
- Beijing Sport University (CN)
- Shanxi Medical University (CN)
- Yan'an University (CN)
- University of Turku (FI)
- East Stroudsburg University (US)
- Corresponding author
- Wang, Jun
- Xiang, Yang
- Venue
- Frontiers in Physiology
- Publisher
- Frontiers Media SA
- Published
- 2019-06-06
- Volume
- 10
- Pages
- 701-701
- ISSN
- 1664-042X (ISSN-L)
- PMC
- PMC6562501
- OpenAlex
- W2960401235
- Cited by
- 22
- References
- 35
- Citations by year
- 2026: 5 · 2025: 6 · 2024: 7 · 2023: 1 · 2021: 2 · 2020: 1
- FWCI
- 0.50
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- Frontiers in Physiology (publishedVersion, cc-by)
- PubMed (publishedVersion)
- PubMed Central (publishedVersion, cc-by)
- UTUPub (University of Turku) (submittedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Topics
- Health Sciences › Medicine › Physiology (medical) › Cardiovascular and exercise physiology
- Health Sciences › Medicine › Physiology (medical) › High Altitude and Hypoxia
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Heme Oxygenase-1 and Carbon Monoxide
- Keywords
- carbon monoxide inhalation, running economy, maximal aerobic capacity, endurance training, erythropoietin, hemoglobin mass, oxygen consumption, altitude training, soccer players, endurance performance
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