Cigarettes and muscles: how smoking affects your training

By Kalorya · July 29, 2026 · 8 min read

Cendrier métallique rempli de mégots de cigarettes

We tend to associate cigarettes with the lungs and the heart. Much less so with muscle. Yet when researchers took muscle samples directly from smokers and non-smokers to assess what was happening inside, the difference was clear — and it cannot be explained by breathing. Here’s what smoking costs an athlete, and above all, what giving up smoking restores — more quickly than you might think.

The most direct measure

In 2007, a study compared the rate at which muscle synthesises protein in smokers and non-smokers. No questionnaire, no estimate: a direct measurement taken from the muscle.

Rate of muscle protein synthesis(%/h of muscle protein synthesis)

2007 study in humans (P = 0.004). The range shown on each bar corresponds to the standard error.

Muscle production is reduced by about a third. And the same study investigated why: in smokers’ muscles, myostatin expression was approximately 33 per cent higher, and MAFbx expression approximately 45 per cent higher. These two are, respectively, the brake on muscle growth and a marker of the muscle-degradation machinery. Tobacco therefore acts on both fronts simultaneously: less building, more breaking down.

Less strength — and, above all, less stamina

A 2008 study of 40 smokers and 45 non-smokers produced a nuanced result, which is worth quoting verbatim: there was no significant difference in maximum force or contraction speed. What did differ, however, was fatigue — which was significantly greater among smokers.

The proposed explanation lies not in the muscle itself but in its oxygen supply: the carbon monoxide in smoke impairs oxygen delivery and mitochondrial function. Your muscle isn’t any weaker during a single repetition; it simply doesn’t last as long during a set. A 2015 review on the subject reaches the same conclusion: the muscles of asymptomatic smokers are weaker and less resistant to fatigue.

As regards efficacy, the large-scale studies do, however, find a dose-dependent signal:

Study	What was measured	Result
2012 — longitudinal study, healthy adults	Knee muscle strength	−2.9% for men and −5.0% for women for every 100 g of tobacco per week
2012 — 4,249 Japanese men	Grip strength and leg strength	Significant differences beyond a high cumulative exposure, after adjustment for age
2007 — 487 women aged between 65 and 77	Chair stand test, timed walk, grip strength	Female smokers take longer to complete the tests and have less strength: an effect equivalent to 7 to 11 years of ageing

What that means over a lifetime

A UK cohort study tracking 2,394 people from birth in 1946 has linked smoking history to physical performance in mid-life: each 10-pack-year increment (one packet a day for ten years) was associated with a 0.11 standard deviation decrease in the overall physical performance index, with impaired balance whilst standing and a reduced ability to stand up from a chair.

A 2015 meta-analysis covering 12 studies and 22,515 participants quantified the link with sarcopenia — age-related muscle loss: an odds ratio of 1.12 (1.03–1.21) overall, and 1.20 (1.06–1.35) in men. In women, the association was in the same direction (1.21) but did not reach statistical significance (0.92–1.59).

Correlation or causation?

That’s the right question, because smokers differ from non-smokers in many other ways. A 2023 study circumvented this problem by using Mendelian randomisation — a method that utilises genetic predisposition to smoking, independent of lifestyle — across 337,138 participants. The result: smoking is causally associated with a lower lean body mass index, a slower walking speed and less time spent on physical activity. Grip strength, however, did not reach statistical significance.

The counterintuitive finding: testosterone

Here’s something surprising. A study of 3,427 men found that smokers had 15 per cent higher total testosterone and 13 per cent higher free testosterone than those who had never smoked — and that these levels increased with the number of cigarettes smoked per day.

This is not a measurement anomaly: a 2016 meta-analysis of 22 studies involving 13,317 men found the same trend (mean difference of +1.53 nmol/L). In women, however, no clear association was found.

This is an excellent lesson in methodology. Smokers have higher testosterone levels, yet less muscle mass, less strength and less endurance. A single hormone reading tells us nothing about the end result — what matters is what the muscle does, not what the blood test shows.

What the ruling delivers, and how quickly

This is the most encouraging aspect of this research, and it happens more quickly than one might imagine. A 2021 study followed 48 smokers for 14 days whilst they were abstaining from smoking: skeletal muscle fatigue resistance improved significantly (p < 0.001), and several inflammatory markers (IL-4, IL-6, IL-10) returned to levels seen in non-smokers.

Two weeks. Over the course of a year, the picture is even broader — a longitudinal study of 41 former smokers found that:

After 12 months without tobacco	What has been achieved
Lean body mass	+1.26 kg
Grip strength	+3.6 kg
Bench press (estimated 1RM)	+7.85 kg
Leg press (estimated 1RM)	+17.02 kg
Total body weight	+4.43 kg, of which +3.15 kg is body fat

The weight gain that often accompanies giving up smoking is real — but it is not all fat: more than one kilo of lean body mass is regained. And the 2015 review makes it clear: many of the effects of smoking on skeletal muscle are likely to be reversible after giving up.

In summary

Question	What the studies say
Does smoking slow down muscle growth?	Yes: protein synthesis at 0.037 versus 0.059 per cent per hour, with higher levels of myostatin and MAFbx
Will I be any less strong?	In terms of maximum repetitions, not necessarily. In terms of fatigue resistance, yes, definitely
Why?	Carbon monoxide impairs oxygen supply and mitochondrial function
And in the long term?	Increased risk of sarcopenia (odds ratio 1.12); causal link confirmed in 2023
What about testosterone?	Higher among smokers (+15 per cent) — and it doesn’t make them any more muscular or stronger
What if I stop?	Just 14 days are enough to improve resistance to fatigue; over the course of a year, a gain of 1.26 kg in lean body mass

The key point here isn’t meant to make you feel guilty; it’s practical: if you smoke and work out, it’s not your maximum strength that lets you down first – it’s your ability to keep going. And that’s precisely what comes back the quickest when you stop.

If fatigue resistance is the weak point, it is the training volume that needs to be built up gradually. A programme followed session by session allows you to see this progress in black and white.

View my programmes

On the same theme of habits that affect performance, we also looked at the true cost of alcohol to muscle tissue.

Every figure in this article is taken from the studies listed below, summarised on the basis of their abstracts alone. Several of these studies are observational and compare groups that also differ in other lifestyle factors; the 2023 Mendelian randomisation study is the one that comes closest to establishing a causal link. This is for information purposes only and is not a substitute for medical advice. To help you give up smoking, a doctor, a pharmacist or the Tabac Info Service can support you.