Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation

Mediating effects of carbon monoxide on the development of hypertension in China

OBJECTIVES

Understanding the relationship between ambient carbon monoxide (CO) exposure and hypertension is crucial for advancing public health research. We investigated the association between air pollution CO exposure and hypertension and determined whether various health indicators played a mediating role.

STUDY DESIGN

Cross-sectional population-based study.

METHODS

Our study examined the data of 13,240 participants in the China Health and Aging Longitudinal Study (CHARLS) conducted in 2015. A logistic regression approach was used to investigate the association between CO concentration and hypertension. The mediating effects (MEs) of health indicators on the association between carbon monoxide and hypertension prevalence were explored using mediation models.

RESULTS

Hypertension was diagnosed in 2953 of the participants. A significantly increased prevalence of hypertension was associated with higher concentrations of air pollutant CO after adjusting for all covariates (OR: 1.19, 95% CI: 1.04-1.37) in the matched group (OR: 1.21, 95% CI: 1.03-1.42). The study also showed that proportional mediation was 3.7% by TG, -5.3% by TC, -2.9% by LDL-C and 19.0% by HDL-C for blood lipid; 4.6% by FPG and 12.2% by HbA1c for blood glucose; -2.0% by grip strength and 16.2% by chair rising time for muscle strength; 59.6% by WC and 1.8% by BMI for obesity indicator and -2.3% by nighttime sleep and 7.8% by daytime nap for sleep duration.

CONCLUSIONS

A significant positive association has been found between environmental CO exposure and hypertension, and obesity, muscle strength, sleep duration, and metabolic factors may play a significant role in mediating this association.

Advances in the Role of Endothelial Cells in Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) poses a serious socio-economic burden due to its high prevalence and severe impact on the quality of life of elderly patients. Pathological changes in CSVD mainly influence small cerebral arteries, microarteries, capillaries, and small veins, which are usually caused by multiple vascular risk factors. CSVD is often identified on brain magnetic resonance imaging (MRI) by recent small subcortical infarcts, white matter hyperintensities, lacune, cerebral microbleeds (CMBs), enlarged perivascular spaces (ePVSs), and brain atrophy. Endothelial cell (EC) dysfunction is earlier than clinical symptoms. Immune activation, inflammation, and oxidative stress may be potential mechanisms of EC injury. ECs of the blood–brain–barrier (BBB) are the most important part of the neurovascular unit (NVU) that ensures constant blood flow to the brain. Impaired cerebral vascular autoregulation and disrupted BBB cause cumulative brain damage. This review will focus on the role of EC injury in CSVD. Furthermore, several specific biomarkers will be discussed, which may be useful for us to assess the endothelial dysfunction and explore new therapeutic directions.

The Acute Effects of Exercising in Air Pollution: A Systematic Review of Randomized Controlled Trials

BACKGROUND

The acute effects of air pollution (AP) exposure during physical activity have been studied. However, comprehensive systematic reviews are lacking, particularly regarding moderate-to-vigorous physical activity (MVPA).

OBJECTIVE

Our objective was to determine the acute health- and exercise-related effects of AP exposure during a bout of MVPA in healthy individuals.

METHODS

We searched for randomized controlled trials in MEDLINE, Embase, Cochrane CENTRAL, SPORTDiscus, Agricultural and Environmental Science Database, ClinicalTrials.gov, International Standard Randomised Controlled Trial Number Registry, and the World Health Organization (WHO) International Clinical Trials Registry Platform up to July 2020 without language or date restrictions. Studies including healthy subjects engaging in a bout of MVPA while exposed to one or more of the following air pollutants were eligible: particulate matter, black carbon, carbon monoxide, nitrogen dioxide, ozone, diesel exhaust, and traffic-related air pollution (TRAP). Main outcome measures were markers of pulmonary function, symptoms, cardiovascular function, cognitive function, systemic inflammation, and exercise response. The evidence was synthesized by vote counting based on direction of effect.

RESULTS

In total, 53 studies were included in the systematic review. Studies employed a heterogeneous mix of exercise protocols, AP interventions, and measured outcomes. Pooled results suggest ozone exposure during MVPA has an adverse effect on pulmonary function (100% [95% confidence interval (CI) 88-100], p < 0.001; high-certainty evidence) and reported symptoms (88% [95% CI 69-96], p < 0.001; low-certainty evidence). The effect of exposure to carbon monoxide, nitrogen dioxide, small engine exhaust, or diesel exhaust during MVPA on health- and exercise-related outcomes is uncertain because of insufficient evidence and the low to very low certainty of available evidence.

DISCUSSION

The evidence is strongest for ozone, exposure to which generally induced a reduction in pulmonary function and increased symptoms during MVPA. The research related to other outcome domains remains inconclusive. Although long-term exposure to AP is proven to be hazardous, the evidence for healthy individuals to forgo MVPA during periods of high (non-ozone) pollution remains weak.

TRIAL REGISTRATION

Retrospectively registered in PROSPERO (CRD42020188280) on 10 July 2020.

Exercise temperature regulation following a 35-day horizontal bedrest

NEW FINDINGS

What is the central question of this study? Does a 35-day horizontal bedrest impair thermoeffector responses during whole-body submaximal exercise performed in temperate conditions? What is the main finding and its importance? Cardiovascular and muscular deconditioning ensuing from prolonged recumbency seems to augment, at least to a degree, exercise-induced increase in body core temperature, most likely due to an impairment in non-evaporative heat loss. The response is a function of the absolute exercise intensity imposed.

ABSTRACT

We examined the effects of a 35-day horizontal bedrest on thermoregulation during whole-body exercise. Fifteen healthy men were randomly assigned to either a bedrest (BR; n = 10) or a control (CON; n = 5) group. Prior to bedrest, both groups performed 40-min constant-load upright cycling at 30% of their peak workload (W_peak ; PRE). One and 2 days after bedrest, the BR group performed, in a randomised counterbalanced order, two 40-min trials at 30% of (i) the pre-bedrest W_peak (i.e., at a fixed absolute intensity; POST-A) and (ii) the post-bedrest W_peak (i.e., at a fixed relative intensity; POST-R). The CON group conducted only the POST-A trial, at the same time intervals. During the trials, rectal (T_rec ) and skin ( T ¯ _sk ) temperatures, and the forehead sweating rate (SwR) were monitored. In the CON group, no differences were observed between the trials. Bedrest potentiated moderately the T_rec elevation during the latter part of POST-A (∼0.10°C; P ≤ 0.05), but not of POST-R (∼0.04°C; P = 0.11). In both post-bedrest trials, T ¯ _sk was attenuated by ∼1.5-2.0°C throughout (P < 0.01), whereas the forehead SwR was not modulated. T_rec and T ¯ _sk were similar in POST-A and POST-R, yet the forehead SwR was more dependent on the relative workload imposed (P = 0.04). The present findings therefore suggest that the cardiovascular and muscular deconditioning ensuing from a 35-day bedrest may aggravate the exercise-induced increase in body core temperature when working at a given absolute intensity, most likely due to an impairment in non-evaporative heat loss.

Match Performance of Soccer Teams in the Chinese Super League-Effects of Situational and Environmental Factors

To investigate the effects of situational factors (match location, strength of team and opponent) and environmental factors (relative air humidity, temperature and air quality index) on the technical and physical match performance of Chinese Soccer Super League teams (CSL). The generalized mixed modelling was employed to determine the effects by using the data of all 240 matches in the season 2015 collected by Amisco Pro^®. Increase in the rank difference would increase the number of goal-scoring related, passing and organizing related actions to a small-to-moderate extent (Effect size [ES]: 0.37–0.99). Match location had small positive effects on goal-scoring related, passing and organizing related variables (ES: 0.27–0.51), while a small negative effect on yellow card (ES = −0.35). Increment in relative air humidity and air quality index would only bring trivial or small effects on all the technical performance (ES: −0.06–0.23). Increase in humidity would decrease the physical performance at a small magnitude (ES: −0.55–−0.38). Teams achieved the highest number in the physical performance-related parameters at the temperature between 11.6 and 15.1 °C. In the CSL, situational variables had major effects on the technical performance but trivial effects on the physical performance, on the contrary, environmental factors affected mainly the physical performance but had only trivial or small impact on the technical performance.

Influence of air pollution exposure on adolescents' objectively-measured physical activity and sedentary behavior

Although regular physical activity is recommended for health, highly contaminated air exposure acts to the detriment of the benefits produced in individuals. The purpose of the present study was to compare the accelerometer-measured physical activity and sedentary behavior during the whole day, in-school time, out-of-school time, and school breaks between highly contaminated air days and non-highly contaminated air days in Chilean adolescents. Nineteen adolescents from Santiago of Chile were assessed by a GT3X accelerometer. The vertical axis and steps per minute for the whole day, and both of these variables together with the percentage of time of moderate-to-vigorous physical activity level in the out-of-school time period were higher in highly contaminated air days than in non-highly contaminated air days (p < 0.05; with effect sizes from r = 0.36 to r = 0.46). Results for sedentary behavior were similar in both conditions for every period of time analyzed. These results allow us to conclude the lack of awareness of the participants in this research regarding the health repercussions in relation to the physical activity performed during air pollution exposure. Some strategies in order to improve the Chilean adolescents' physical activity and sedentary behavior are suggested and discussed.

Cardiopulmonary and Muscular Interactions: Potential Implications for Exercise (In)tolerance in Symptomatic Smokers Without Chronic Obstructive Pulmonary Disease

Smoking and physical inactivity are important preventable causes of disability and early death worldwide. Reduced exercise tolerance has been described in smokers, even in those who do not fulfill the extant physiological criteria for chronic obstructive pulmonary disease (COPD) and are not particularly sedentary. In this context, it is widely accepted that exercise capacity depends on complex cardio-pulmonary interactions which support oxygen (O₂) delivery to muscle mitochondria. Although peripheral muscular factors, O₂ transport disturbances (including the effects of increased carboxyhemoglobin) and autonomic nervous system unbalance have been emphasized, other derangements have been more recently described, including early microscopic emphysema, pulmonary microvascular disease, ventilatory and gas exchange inefficiency, and left ventricular diastolic dysfunction. Using an integrative physiological approach, the present review summarizes the recent advances in knowledge on the effects of smoking on the lung-heart-muscle axis under the stress of exercise. Special attention is given to the mechanisms connecting physiological abnormalities such as early cardio-pulmonary derangements, inadequate oxygen delivery and utilization, and generalized bioenergetic disturbances at the muscular level with the negative sensations (sense of heightened muscle effort and breathlessness) that may decrease the tolerance of smokers to physical exercise. A deeper understanding of the systemic effects of smoking in subjects who did not (yet) show evidences of COPD and ischemic heart disease - two devastating smoking related diseases - might prove instrumental to fight their ever-growing burden.

The effect of air pollution on diurnal variation of performance in anaerobic tests, cardiovascular and hematological parameters, and blood gases on soccer players following the Yo-Yo Intermittent Recovery Test Level-1

This study aimed to investigate the effect of air pollution on diurnal variation of performance in anaerobic tests, cardiovascular and hematological parameters, and blood gases on soccer players following the Yo-Yo Intermittent Recovery Test Level-1 (YYIRT1). In a randomized order, 11 healthy soccer players (mean age: 21.8 [range: 20-24] years; height: 178.00 [range: 1.64-1.83] cm; body mass index [BMI]: 23.57 [range: 20.45-28.03] kg.m^-2) performed a YYIRT1 at two different times of day (TOD) (08:00 h and 18:00 h) in two areas (i.e. polluted (PA) and non-polluted (NPA)) with a recovery period of ≥ 72 h in between, to determine the maximal oxygen uptake (VO2max). In each test session: resting oral temperature is measured, anaerobic performances (pre- and post-YYIRT1) were performed, cardiovascular parameters and blood samples were collected at: rest, 3 min and 60 min after the YYIRT1, to assess blood gases and hematological parameters. Our results showed that, agility performance, VO2max, red blood cells (RBC), hemoglobin (Hb), pH, and bicarbonate levels (HCO3^-) decrease significantly (p < 0.001) following the YYIRT1 in PA compared to NPA. Likewise, the heart rate (HR), systolic blood pressure (SBP), platelets (PLT), white blood cells (WBC), neutrophiles (NEUT), lymphocytes (LYM), and partial pressure of CO2 levels (P_vCO2) were significantly higher (p < 0.001) in PA. This effect was slightly accentuated at 18:00 h for some parameters (i.e. Agility, HCO3^-, HR, P_vCO2, RBC, SBP). However, performances of sprint and Sargent jump test (SJT), oral temperature, rate of perceived exertion scales (RPE), partial pressure of O2 (P_vO2), diastolic blood pressure (DBP), and monocytes (MON) were not affected by pollution (p > 0.05). In conclusion, pollution seems to be critical for health stability and performance in response to YYIRT1 especially in the evening and the winter season. Therefore, coaches and athletes should draw attention to the potential importance of land use planning in their training sessions and competitions in the morning in polluted area to minimize the risk of pollution exposure.

The health effects of exercising in air pollution

The health benefits of exercise are well known. Many of the most accessible forms of exercise, such as walking, cycling, and running often occur outdoors. This means that exercising outdoors may increase exposure to urban air pollution. Regular exercise plays a key role in improving some of the physiologic mechanisms and health outcomes that air pollution exposure may exacerbate. This problem presents an interesting challenge of balancing the beneficial effects of exercise along with the detrimental effects of air pollution upon health. This article summarizes the pulmonary, cardiovascular, cognitive, and systemic health effects of exposure to particulate matter, ozone, and carbon monoxide during exercise. It also summarizes how air pollution exposure affects maximal oxygen consumption and exercise performance. This article highlights ways in which exercisers could mitigate the adverse health effects of air pollution exposure during exercise and draws attention to the potential importance of land use planning in selecting exercise facilities.

The neurovascular unit - concept review

The cerebral hyperaemia is one of the fundamental mechanisms for the central nervous system homeostasis. Due also to this mechanism, oxygen and nutrients are maintained in satisfactory levels, through vasodilation and vasoconstriction. The brain hyperaemia, or coupling, is accomplished by a group of cells, closely related to each other; called neurovascular unit (NVU). The neurovascular unit is composed by neurones, astrocytes, endothelial cells of blood-brain barrier (BBB), myocytes, pericytes and extracellular matrix components. These cells, through their intimate anatomical and chemical relationship, detect the needs of neuronal supply and trigger necessary responses (vasodilation or vasoconstriction) for such demands. Here, we review the concepts of NVU, the coupling mechanisms and research strategies.