Cigarette and cardio: what tobacco costs your breath

Smoking lowers your cardio, and not just in the long term: three cigarettes before an effort are enough to cause a loss of about 7% of VO2max. In smokers, the heart climbs less high during exertion and drops back down less quickly afterwards, and physical fitness declines more quickly with the years. The good news: quitting restores part of the ground in a few weeks. Here is what twenty studies in people with no declared disease measure.

This article is about breath and the heart. What tobacco does to the muscle itself — protein synthesis, strength, fatigue — has its own article: Cigarette and muscle. And to know what makes VO2max climb, there is Improving your cardio.

The main culprit: carbon monoxide

Cigarette smoke contains carbon monoxide, which binds to hemoglobin instead of oxygen. A review on the subject explains that this rise in carbon monoxide in the blood, whether it comes from long-standing smoking or the last cigarette, reduces exercise tolerance and VO2max. The smoker also depends more on the glycolytic pathway during exercise, which contributes to earlier fatigue.

In 16 men tested on a bike, researchers compared the smoke of three cigarettes to an inhalation of carbon monoxide alone, adjusted to give the same blood saturation. In both cases, VO2max dropped by about 7%. But the exertion time held at VO2max dropped by 20% after the cigarettes, against 10% after carbon monoxide alone: the authors attribute the gap to the respiratory cost increased by the particles in the smoke. The cigarette also made the resting heart rate climb and the maximum heart rate drop, which carbon monoxide alone did not do.

A heart that climbs less high and drops back down less quickly

In 298 young adults aged 20 to 29 without disease, smokers had a higher resting heart rate, a slower rise during exertion, and a lower maximum frequency: 191 versus 198 beats per minute in women, 193.2 versus 199.3 in men. Recovery after exertion was poorer, but only in women. In 93 healthy young men (42 smokers, 51 non-smokers), smokers had a heart that beat faster at rest and at submaximal exertion, higher cardiac work, and held out significantly less long on the maximal exertion test.

In 112 heavy smokers apparently in good health, compared to 67 non-smokers, the heart rate dropped back down less quickly after a maximal exertion, at 1, 2, 3, and 5 minutes: at one minute, a drop of 26.8 beats against 32.8. In the Framingham study (1,468 men and 1,642 women), smokers were more numerous in failing to reach the target heart rate planned for their age: 25% against 15% in men, 32% against 18% in women. In male smokers, this heart that does not climb enough went with a higher risk of death and coronary events.

Less in shape, and a shape that wears out faster

In 6,592 young conscripts, all aged 19, the distance covered in 12 minutes of running dropped with the number of cigarettes per day and the number of years of tobacco, even in light smokers. In 4,358 joggers from the same study, the link remained after taking their physical activity into account. Other armies find the same thing: in 1,629 Finnish conscripts, cardiorespiratory fitness was poorer in smokers, and worse still when tobacco was added to overweight; in 3,669 Taiwanese military personnel, smokers took an average of 15.7 seconds longer over 3,000 meters.

In 2,749 adults whose VO2max was measured, the gap grew with the dose: −0.83, −0.85 and −2.56 mL of oxygen per kilo per minute for light, moderate and heavy smoking (more than 20 pack-years). In 2,830 Korean adults and 629 seniors, the difference on the 20-meter shuttle run was clear in men under 65, less visible in women and older individuals.

The most telling is follow-up over time. In 1,393 healthy Norwegians aged 40 to 59, followed for seven years, smokers started out already lower (1,349 versus 1,618 joules per kilo on the bike test), and their physical condition dropped by 217 J/kg, against 86 in non-smokers — two and a half times faster, even taking age and physical activity into account. Those who had stopped smoking evolved like non-smokers.

Passive smoking too

In 43 adults without symptoms, the VO2max of non-smokers was significantly higher than that of smokers, but also than that of people exposed to the smoke of others — whose VO2max did not differ significantly from that of smokers. The study is small. In 104 children aged 9 to 11, exposure to the smoke of others was associated with a lower cardiorespiratory capacity.

Training works anyway, quitting on top works better

Smoking does not prevent progress. After 12 weeks of intermittent training, VO2max rose by 4.7% in 12 cigarette smokers, as much as the 4.4% of the 11 non-smokers, and their resting heart rate dropped. But in 109 middle-aged female smokers followed for 12 weeks, trained three times a week at about 83% of their maximum frequency, those who quit smoking along the way gained even more duration on the stress test and more oxygen consumption than those who continued.

What quitting restores, and in how much time

Quickly, according to a 12-week randomized trial in healthy smokers: those who completely stopped smoking gained 2.4 mL/kg/min of VO2max as early as the 4th week, and 2.7 at the 12th. Those who had only reduced gained 1.3 then 1.9 mL, and those who continued to smoke, nothing.

In 17,115 middle-aged adults followed with an annual exercise stress test, those who had quit two years ago at most improved their test duration 2.4 times more than smokers (+24 seconds versus +10), and had 26% more chances of making progress. The benefit was less marked in those who had quit for a longer time: the main effect happens in the first two years.

In summary

Quitting and training at the same time is what yields the most: the workout generator builds you a program at your own pace, and Improving your cardio explains which sessions increase VO2max.

Every figure in this article comes from a study you can open: the underlined mentions lead to the summary of the work it is taken from, written from the abstract alone. Informative content, which does not replace the advice of a healthcare professional — to quit smoking, your doctor or pharmacist can support you.