Abstract
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.
Highlights
Cigarette smoking, the most important preventable cause of death worldwide, is strongly associated with the poor quality of life and health-care resources utilization. (World Health Organization, 2011) Physical inactivity, a common finding in smokers, has been mechanistically linked to a plethora of nontransmissible diseases (World Health Organization, 2010; Lee et al, 2012)
The present review aims to succinctly summarize the recent advances in our knowledge on the effects of smoking on the muscle-lung-heart axis under the stress of exercise
The deleterious consequences of high (HbCO) might be important in the presence of comorbidities: low-dose inhaled CO (Aronow, 1976) and nicotine patch in substitution to smoking (Mahmarian et al, 1997) have been implicated in lower exercise capacity seen in smokers with ischemic heart disease
Summary
The most important preventable cause of death worldwide, is strongly associated with the poor quality of life and health-care resources utilization. (World Health Organization, 2011) Physical inactivity, a common finding in smokers, has been mechanistically linked to a plethora of nontransmissible diseases (World Health Organization, 2010; Lee et al, 2012). There is, increasing awareness of the link between exercise intolerance and smoking (Clini et al, 2016); the last decades witnessed a growing debate on the consequences of preclinical chronic obstructive pulmonary disease (COPD) – the prototype of a smoking-related disease – on clinical outcomes, including exercise intolerance (Caram et al, 2016; Chen et al, 2016; Rhee et al, 2017; Soriano et al, 2018) In this context, reduced maximal and submaximal exercise tolerance and breathlessness on daily life (modified Medical Research Council dyspnea score, ≥2) have been described in a subgroup of smokers, even when they do not fulfill the extant physiological criteria for COPD (Klein et al, 1992; Misigoj-Durakovic et al, 2012; Liu et al, 2015; Regan et al, 2015; Elbehairy et al, 2016, 2017a; Woodruff et al, 2016; Di Marco et al, 2017; Martinez et al, 2017; Walter Barbosa et al, 2017; Fuertes et al, 2018) and they are not sedentary (Misigoj-Durakovic et al, 2012; Fuertes et al, 2018). We will focus on the chronic consequences of smoking on exercise intolerance from an integrative physiological perspective, giving special attention to the ancillary effects of aging, and physical inactivity
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