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. 2024 Jan 11;21(1):2302383. doi: 10.1080/15502783.2024.2302383

The effects of nicotine withdrawal on exercise-related physical ability and sports performance in nicotine addicts: a systematic review and meta-analysis

Kangzhe Bao a, Kai Zheng a, Xianxian Zhou a, Baichao Chen a, Zerui He a, Danyang Zhu b,✉
PMCID: PMC10791090  PMID: 38213003

ABSTRACT

Background

Previous research has established that nicotine withdrawal can ameliorate cardiovascular and pulmonary function in smokers. Nevertheless, the impact on physical fitness and athletic performance remains under-investigated.

Objective

To evaluating the impacts of nicotine withdrawal on both exercise performance and exercise-associated physical capabilities in nicotine-dependent individuals.

Study design

A comprehensive systematic review and meta-analysis.

Data sources

The data was compiled from databases such as PubMed, Scopus, Web of Science, Cochrane Central, and EBSCO.

Study selection

The selection criteria required studies to elucidate the effects of nicotine withdrawal on exercise performance or exercise-related physical abilities. Moreover, the selected studies needed to provide discernible experimental results.

Data synthesis and analysis

The random effects model was employed in data analysis, utilizing the standardized mean difference (SMD) and the 95% confidence intervals (95% CIs) to estimate participants’ exercise performance and physical abilities, referencing the Mean ±SD during baseline and withdrawal states.

Results

Out of the selected studies, 10 trials were included, encompassing 13,538 participants aged 18 to 65 years. The findings suggest that nicotine withdrawal could potentially enhance sports performance (SMD = 0.45, 95% CI: 0.03 to 0.88; I^2 = 83%), particularly in terms of aerobic capacity. Short-term nicotine withdrawal (spanning 12 to 24 hours) might lead to a decline in participants’ physical abilities in certain aspects like reaction time and sustained attention (SMD = −0.83, 95% CI: −1.91 to 0.25; I^2 = 79%), whereas long-term withdrawal (lasting 48 hours or more) demonstrated an opposing trend (SMD = 0.25, 95% CI: 0.12 to 0.39; I^2 = 81%). Overall, the results show that long-term nicotine withdrawal exhibited some positive impacts on sports performance and exercise-related physical ability, with the withdrawal duration being an indicator of subsequent physical performance.

Conclusions

Mid- to long-term (≥3 months) nicotine withdrawal significantly improved the exercisers’ exercise-related physical ability and sports performance. Conversely, short-term (≤24 hours) nicotine withdrawal considerably hampered exercisers’ performance and physical cognition. It is suggested that exercises avoid abrupt nicotine cessation prior to competitions, as long-term nicotine withdrawal has been shown to significantly enhance exercise-related physiological capacities and athletic performance. By referring to existing literatures we also found that athletes with existing nicotine addiction may could consume nicotine 15–30 minutes before competition to enhance athletic performance and physical function.

PROSPERO registration number CRD42023411381.

KEYWORDS: Nicotine withdrawal, sports performance, exercise physiology, sports training, physical function

1. Introduction

Regarded as one of the most significant public health threats globally, the tobacco epidemic’s profound impact is undeniable. It is widely recognized that nicotine, a primary component of tobacco, contributes to over half of all cancer cases worldwide, resulting in more than 8 million fatalities annually. This includes approximately 1.2 million deaths attributed to secondhand smoke exposure. The harmful nature of all forms of tobacco is well-documented, with no safe exposure levels identified [1–4]. The advertising, marketing, and promotion of electronic nicotine delivery systems are experiencing rapid expansion, primarily through the heavy reliance on Internet and social media channels, leading to an increasingly diverse youth exposure to nicotine [5].

Although research has shown a negative correlation between exercise and nicotine intake [6], with athletes generally consuming less nicotine than the general population, an intriguing contradiction has been observed. An analysis of 60,802 doping tests conducted in Italy revealed that 22.7% of the samples tested positive for nicotine. Furthermore, one out of every five samples taken from a variety of 90 sports also tested positive for nicotine during competition [7], indicating that nicotine intake is surprisingly common amongst athletes.

Nicotine, like caffeine, is a globally consumed psychoactive substance [8]. In the late 1970s and 1980s, the use of nicotine, particularly in the form of chewing tobacco and wet snuff, gained popularity among professional baseball players. More recently, its use has been detected predominantly in winter sports. This led the WADA（World Anti-Doping Agency）to incorporate nicotine into its monitoring program in 2012 [9]. However, the current policy of the WADA does not prohibit the use of nicotine [10].

From a public health perspective, there is global consensus regarding the detrimental effects of smoking on health. Ample evidence attests to the negative impact of tobacco smoking on a range of health conditions, including cardiovascular diseases, pulmonary diseases, and various types of cancer [11]. Yet, the effect of nicotine intake on exercise remains somewhat ambiguous.

Nicotine consumption has been linked to diminished lung function, particularly in athletes involved in skill and strength-based sports. The implications of nicotine intake can be seen in elevated body fat percentages and reduced muscle mass [12]. Conversely, smoking can also augment serum hemoglobin and total lung capacity while promoting weight loss, all of which may potentially enhance endurance sports performance [13]. An earlier study examining a 10 km run among adolescents found a significant reduction in exercise performance among smokers [14]. This finding was further supported by a later study on the cardiorespiratory capacity of taekwondo athletes: nonsmokers exhibited a slower heart rate recovery and took longer to reach the ventilatory threshold than their smoking counterparts. Increased cumulative fatigue time for ventilation and quicker post-exercise recovery appeared to aid sustained exercise and improve overall performance [15].

However, contradicting these findings, another study reported that nicotine does not affect heart rate, cardiac output, and VO2 max（maximal oxygen uptake）at maximal exercise. Nicotine has also been utilized in sports for its perceived benefits, such as reducing anxiety, enhancing concentration and agility, supporting weight control, and boosting aerobic performance [16]. On the other hand, some researchers have found that smoking may intensify exercise fatigue in female smokers and decreases their average performance during a 20 m intermittent sprint test, along with reducing their muscle strength and maximal aerobic capacity [17]. Paradoxically, in gender-specific studies, male athletes demonstrated significantly improved exercise endurance and muscle strength following nicotine intake [18].

Furthermore, nicotine has been found to influence several physical capabilities related to exercise. It is known to decrease body weight, lower BMI（Body Mass Index）, stimulate the sympathetic adrenal system, and increase heart rate, contractility, vasoconstriction, blood pressure, and circulating catecholamine levels during light exercise. Additionally, nicotine can enhance muscle blood flow and elevate cortisol levels [19–22].

Cognitive abilities are an important part of physical abilities related to exercise [23]. In the realm of cognitive performance, particularly those linked with exercise, studies have found that water pipe and cigarette smoking diminish cognitive function when compared to nonsmokers. This is particularly apparent in the areas of attention, speed, and reaction time [24,25]. However, certain scholars have also suggested that nicotine intake can significantly improve cognitive performance [26].

Despite the increasing focus on research investigating the potential impacts of nicotine on exercise, these studies have primarily addressed the potential effects of nicotine consumption, offering little insight for nicotine-dependent individuals regarding the effects on exercise performance post-nicotine withdrawal. Prior systematic reviews have proposed that nicotine withdrawal results in reduced cortisol and carboxyhemoglobin concentrations, triggering withdrawal symptoms such as weight gain, restlessness, irritability, inattentiveness, a decrease in heart rate, and slower reaction time. These effects could have a direct impact on exercise performance [22,27,28].

The influence of nicotine withdrawal on the enhancement of exercise capacity has primarily been observed in aspects such as aerobic endurance, oxygen uptake, BMI, running speed, muscle strength, bone density, heart rate reserve, and systolic and diastolic blood pressure [29–34]. However, when considering exercise-related physical abilities, nicotine withdrawal can lead to a decrease in reaction time, impaired short-term memory and information processing, and reduced sustained attention among individuals engaging in exercise [35–38].

Notably, in the existing body of research on the adverse effects of nicotine withdrawal on cognitive performance, the duration of nicotine withdrawal for the subjects was generally equal to or less than 24 hours. Conversely, the remaining studies appear to indicate that extended periods of nicotine withdrawal can yield numerous benefits to physical functioning.

To date, as per our understanding, no meta-analysis of clinical trials has endeavored to estimate the extent of these effects, an exercise which is of paramount importance to formulate practically applicable recommendations. Thus, the primary aim of this systematic review and meta-analysis is to amalgamate evidence from existing experimental studies to estimate the SMD of nicotine withdrawal on exercise performance and exercise-related physical abilities in physically active individuals. Furthermore, this study aims to quantify the impact of withdrawal duration on these effects.

2. Methods

This research study conducted a comprehensive systematic review and meta-analysis, strictly conforming to the guidelines prescribed by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the PERSIST guidance [39,40]. The PRISMA checklist is available in the online supplementary material Table S1. Additionally, this study’s protocol was registered with PROSPERO (CRD42023411381).

2.1. Equity, diversity, and inclusion statement

Our research incorporates all studies published within the chosen literature base, regardless of gender, race, ethnicity, socioeconomic status, or occurrence in marginalized communities. The research team comprised one woman and five men from varied disciplines (physical education teaching, sports training, sports psychology, education), which included one professor, one PhD, and four authors identified as junior academics. Although we examined public health factors, the data collection method remained consistent across all cases and did not modify the methodology based on regional, educational, or socio-economic factors. In the course of this study, we delineated the potential influence of gender on nicotine withdrawal.

2.2. Eligibility criteria

The eligibility criteria for this study were meticulously devised following the PICOS strategy, predicated on previously established themes and the registration process with PROSPERO.

The inclusion criteria were defined as follows: (1) Participants: Individuals dependent on nicotine, regardless of age or gender, without any other medical conditions that might affect their performance in the experiment, capable of completing the nicotine withdrawal intervention and participating in the functional test; (2) Intervention: Nicotine withdrawal or substitution with a nicotine-free placebo, with no restrictions on the duration of withdrawal; (3) Comparison: Nicotine dependent individuals who do not undergo nicotine withdrawal or have no history of nicotine use, other conditions being essentially identical; (4) Outcome: Indicators reflecting the participant’s physical abilities as demonstrated by exercise (for example, strength, speed of movement, aerobic capacity, reaction speed, etc.) [41]; (5) Study Design: Randomized controlled trials, self-control trials.

The exclusion criteria were defined as follows: (1) Any non-human experiments such as animal studies; (2) Participants with physical health issues that may affect exercise performance; (3) Participants who have not undergone nicotine withdrawal for a certain period; (4) Lack of experimental indicators that can reflect specific exercise abilities; (5) Review papers and meta-analyses.

2.3. Information sources

The researchers performed a comprehensive literature search across five electronic databases, namely PubMed, Scopus, Web of Science, Cochrane Central, and EBSCO, covering the entire duration from their inception to 7 April 2023. The search aimed to identify all published studies examining the relationship between nicotine withdrawal and exercise performance. Only articles published in English were selected for inclusion.

2.4. Search strategy and selection process

The search strategy implemented in this study encompassed the utilization of pertinent search terms, including “nicotine withdrawal,” “stopping smoking,” “sports performance,” and “physical ability,” along with their respective variations. The search was carried out by merging the aforementioned terms with the aid of Boolean operators and tailoring them to the requisite syntax for each database. To enhance the search precision, we employed quotation marks and the wildcard symbol. For an elaborate account of the search syntax, kindly refer to Table S2 available in the online supplemental material.

The articles procured from each database were assembled into a consolidated database using EndNote V. x9 software (Clarivate, The EndNote Team, Pennsylvania, USA), allowing for the elimination of redundancies. To ensure no relevant articles were overlooked, a panel of three reviewers (KZB, XXZ, and ZRH) independently executed the article selection process, and any inconsistencies were collectively discussed and resolved. Initially, all titles and abstracts underwent screening, and studies failing to meet the inclusion criteria were eliminated. Upon completion of this step, articles independently screened by the three researchers were gathered into a shared pool for a second duplicate removal. The remaining studies had their full text retrieved, during which the reference list of each was screened as part of a secondary search. Studies fulfilling the inclusion criteria were eventually included. Reference lists of literature reviews identified were scrutinized for any original studies not found during the initial search.

2.5. Data collection and extraction

Data extraction from the included studies was executed by one reviewer (BCC) and validated by a second reviewer (KZ). In case of discrepancies, a third reviewer (KZB) was consulted for resolution. The following data were extracted: authors, year, country, study design, sample size, participant characteristics (gender, age, quantity of nicotine intake), intervention characteristics (methods and duration of nicotine withdrawal), outcomes (indicators reflecting sports performance, sports performance tests applied, test schedule, and duration from nicotine withdrawal to test), and main findings. The extracted data encompassed performance indicators related to physical abilities, measured through tools and methods, such as cardiopulmonary capacity (systolic, diastolic, heart rate, etc.), and body composition metrics (BMI, body fat percentage, etc.). Moreover, only the data reflecting exercise performance and body-related abilities of nicotine users before and after withdrawal were extracted, leaving out comparison data between smokers and nonsmokers [20]. The data extraction was independently executed by two evaluators (KZ and KZB, respectively), and any discrepancies were reconciled through discussion.

2.6. Study risk of bias assessment

Two researchers (KZB and ZRH) independently evaluated the risk of bias using the Rob 2.0 tool designed by the Cochrane Collaboration [42]. This tool appraises bias across five domains: the randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome, and the selection of reported results. Any discrepancies between the researchers’ assessments were harmonized through discussion. A study was categorized as having a low risk of bias if all domains were judged as low risk. If at least one domain was identified with some concerns, the study was categorized as having some concerns. Lastly, a study was deemed to have a high risk of bias if at least one domain was assessed as high risk. In the analysis of the 10 studies included in this review, one study presented a high risk of bias owing to significant baseline differences in subject age, while two others demonstrated some level of bias. The remaining studies were assessed to have a low risk of bias. Following collective deliberation and thorough examination of the full texts, we determined that the high-risk study remained appropriate for inclusion and subsequent analysis in our research. Details concerning the risk assessment will be provided in the supplementary material.

Given the complex and diverse nature of sports performance parameters, a comprehensive analysis of all relevant measures is not feasible. Therefore, we have segregated the pertinent indicators into two primary categories. The first category (1) encompasses physical abilities relevant to exercise, including cognitive abilities like reaction speed and attention, and physical fitness measures related to anthropometric parameters such as height, weight, and BMI, along with relevant physiological and biochemical indices. The second category (2) refers to sports performance indicators reflecting physical prowess, including assessments of strength, speed, endurance, among other metrics.

In 10 studies with varied duration data on abstinence [29–38], the physical performance and exercise capacity of smokers before and after cessation were analyzed. These studies categorized participants into three groups: nonsmokers, nicotine-free individuals, and those abstinent from nicotine. In one study [29], the impact of the non-exercise and exercise groups on exercise performance before and after nicotine cessation was considered. However, in alignment with the aim of this study, the exercise group aligned better with the research direction, thus, only the exercise data from the exercise group before and after nicotine cessation was analyzed. In another study [30], several participants relapsed and continued smoking because the duration of the entire abstinence study lasted for 3 years, but a subset of participants remained committed and completed the abstinence study task. Therefore, data analysis was conducted solely for this group of successful abstainers. Due to a lack of data availability for the Study [38], Plot-Digitizer (version 1.3 Department of Physics University of South Alabama) was utilized to extract data from the images in the article. If multiple parameters of the same dimension as sports performance and physical ability are available, the combined estimator is calculated using the random effects model.

In the study [31], the data lacked Mean/SD calculation, but given the study’s large sample size and the high credibility of the experiment conducted on the Marine Corps population, the study was included in the main analysis. However, its influence on the results was omitted from the sensitivity analysis.

Using the random effects model, SMD and the 95% confidence intervals (95% CIs) were used to estimate participants’ exercise performance and physical abilities based on Mean ± SD at baseline and withdrawal states [43]. SMD was used to estimate the effect size since different measures were used in the studies to analyze the exercise performance and physical abilities of participants, such as heart rate [32,33,35], body composition [29,30], and reaction time [35–38], among others. The heterogeneity of the studies was estimated by I^2 statistics [44], which were categorized into low heterogeneity (0%-40%), moderate heterogeneity (30%-60%), substantial heterogeneity (50%-90%), and considerable heterogeneity (75%-100%).

Heterogeneity was investigated through subgroup analyses by nicotine withdrawal duration (≤12 hours, 12 to 48 hours, and 48 hours or more) [45]. Gender differences in nicotine withdrawal were analyzed [46] in subgroups of study populations (Female, Male, Mixed Gender). Additionally, the size of the sample and the frequency of nicotine intake in different studies were also important factors. To identify the potential for publication bias in each study, funnel plots were constructed for five or more studies [47]. As there were fewer than 10 studies on the effects of withdrawal on nicotine-dependent subjects in this study, meta-regression analysis was not performed on covariables such as withdrawal duration and gender characteristics, as suggested by the Cochrane Handbook [48]. In general, when SMD is less than 0.2, it can be considered negligible; when SMD is larger than 0.2 and less than 0.5, it is considered small; when SMD is larger than 0.5 and less than 0.8, it is considered medium; when SMD is at least 0.8, it is considered large [49]. R studio software was employed for the statistical procedures [50]. When p < 0.05, it indicated that there were differences in exercise performance and physical abilities of participants before and after withdrawal; when p < 0.001, it indicated significant differences, which validated that the results of the meta-analysis were statistically significant.

To assess the robustness of the pooled estimates and detect whether any single study accounted for a significant proportion of heterogeneity, the “meta info” command in the Meta package was used to analyze the sensitivity of individual studies [51]. After excluding one study at a time, the remaining studies were combined to generate a new SMD (95%CI) to analyze the influence of individual studies on the combined results.

3. Results

3.1. Study selection

As illustrated in Figure 1, an initial pool of 10,315 studies was reduced to a mere 19 after thorough scrutiny, deemed appropriate for further in-depth evaluation. However, nine of these did not satisfy the predefined inclusion criteria, resulting in their exclusion. A detailed list of the excluded studies and their reasons for exclusion is provided in Table S3 and Table S4, available in the online Supplementary Material. The final meta-analysis incorporated a total of 10 studies.

Figure 1.

Figure 1.

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Screening flowchart.

3.2. Characteristics of the included studies

The current meta-analysis comprised ten research articles, seven of which originated from the United States [29–32,36–38] while the rest were published in Greece [35], Brazil [33], and Israel [34]. Among these ten studies, six were randomized controlled trials [29–31,33,35,38], and the remaining four were self-controlled trials [32,34,36,37]. The individual trial sample sizes spanned a wide range, from 6 to 155 participants, with one study setting itself apart by comparing data from over 10,000 Marine recruits [31] rather than conducting its own trial. Four studies included a mix of male and female subjects [29,30,33,34], whereas the other six studies exclusively recruited male participants [31,32,35–38].

Nicotine withdrawal duration differed across studies: five studies focused on short-term withdrawal periods of no more than 24 hours [33,35–38], three investigated withdrawal periods of up to three months [29,31,32], and the final two studies evaluated withdrawal periods exceeding one year [30,34]. A total of 13,520 nicotine-dependent subjects were incorporated in the analyses, with all studies offering insights into exercise-related physical ability or performance, facilitating definitive conclusions.

The analysis of exercise-related physical capacity considered several indicators, such as BMI, blood pressure, oxygen uptake, heart rate, and reaction time. The primary outcome indicators for exercise performance included exercise duration until exhaustion, movement speed, and grip strength. For additional details regarding the characteristics of the studies, please refer to Table 1.

Table 1.

Characteristics of the included studies.

Authors，year Country Experimentaldesign Study population Sample size Mean age (year) ±SD Nicotine duration Nicotine frequency cigarettes/per day) Withdrawal
duration		 Measurementmethods Outcome indicator Analysis of the main results
For Sports-related physical abilities For Sports
Performance
Anna E.Albrecht et al. 1998 [29] US RCT Middle-aged Females 58 42±9 ≥3 (year) 22±9 12 weeks Calibratedmedical scale、Bicycleergometer、Exercise electrocardiographic recorder Total duration of exercise(S) 、Body mass index、Percent body fat 、Blood Pressure、Peak oxygen consumption + +
Asha Asthana et al. 2011 [30] US RCT (prospective,double-blind,randomized,placebo-controlledtrial) Males and Females 155 43.4± 11.5 26.8±20.6 (pack- years) 20.7±8.4 3 years Treadmill Stress Testing (TST) TST (treadmill stress testing)
Parameters、heart rate (HR)
、Peak METs 、HR reserve
and 60-second HR recovery		 + +
CDR Jeffrey H. Feinberg et al. 2015 [31] US RCT Males Marine Corps recruit 13248 18–19(n=8073);
20–28(n=5175)		 NR NR 3 months Military recruit training (1.5miles running and 3.0milesrunning) Run-speed + +
GeorgeGiannakoulas et al. 2003 [35] Greece RCT Males Pilots 10 33.7± 1.4 14.9±2.8
(pack-years)		 20.6±3.08 12 hours Questionnaire、Measurement of BP Heartrate and the execution ofcertain computerized
performance assessment tests		 Reaction Time(S) 、Heart rate、Blood pressure - -
Kazuo Hashizume et al. 2000 [32] US Self-controlled experiments Young Males 11 20.5±0.3 3.5± 1.0 (year) 20.5±6.9 6–7 days Mercury Sphygmomanometer、 Electronic spirometer 、Bloodtests 、Heart rate monitor 、 Bicycle ergometer 、Treadmill Oxygendebt 、Hrrest 、blood
pressure 、Venous blood
parameters Oxygenp take and Heart rate during submaximal and Maximal exertion		 ± +
Thomas S. Marzilli et al. 2000 [36] US Self-controlled experiments Young Males 6 20.5±0.6 NR ≥20 12 hours Reciprocal-Tapping Task Reaction time(S) 、 Movement(S) - -
Thomas S. Marzilli et al. 2002 [37] US Self-controlled Experiments(counterbalanced,placebo-controlled double-blind) Young Males 7 20.5±0.5 NR ≥20 12 hours Reciprocal-Tapping Task、Electromyograpy Reaction time(S) - -
Demilto Yamaguchi da Pureza et al. 2007 [33] Brasil RCT Young Females 7 21±0.3 7± 1.4(years) 10–20 24 hours Submaximal test in ergometric bicycle and at recovery Systolic blood pressure(SBP) and Diastolic blood pressure (DBP) and Heart rate (HR) 、The double product (DP) was calculated through the product
between the HR and SBP		 + +
John R.Hughes et al. 1989 [38] US RCT (prospective tests) Young Males 8 21.8±5.4 11.4±6. 1(years) 23.2±6.7 24 hours Sustained attention task Slow reaction time (RT)、 Reaction time (SDRT) - -
Oren Rom et al. 2014 [34] Israel Self-controlled experiments
single-blind)		 Male and Female 10 39.56±22 17.77±24(years) ＞15 12 months Dual-energy X-ray
Absorptiometry and
Handgrip dynamometry		 Body composition (BMI,lean mass, appendicular skeletal muscle index,fat mass, bone mineral content, bone mineral density) 、Muscle strength
(handgrip strength)		 + +
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“NR” means not reported; “+” means there is a positive impact; “-” means there was a negative impact; “±” means both positive and negative impact.

3.3. Main results from the meta-analysis

Four studies (n = 303) compared sports performance before and after nicotine withdrawal. Given the considerable heterogeneity among these four studies (I^2 = 83%, p < 0.01), a random effects model was employed. The results highlighted a statistically significant enhancement in sports performance following nicotine withdrawal (SMD = 0.45, 95% CI:0.03 to 0.88) (Figure 2). Subgroup analysis revealed that females (SMD = 0.79, 95% CI:0.52 to 1.05) experienced a more significant improvement in sports performance compared to males (SMD = 0.46, 95% CI: −0.87 to 1.79) (Figure S1). Subgroup analyses based on nicotine intake frequency and sample size echoed these gender-based findings (Figure S2, Figure S3). Since the duration of nicotine withdrawal exceeded 48 hours in all four studies, a subgroup analysis was conducted based on outcome indicators. The results of this analysis showed significant improvements in Movement duration (SMD = 0.84,95% CI:0.49 to 1.19) and Peak oxygen consumption (SMD = 0.79,95% CI:0.41 to 1.17), but not for other indicators such as Hand strength (Figure S4).

Figure 2.

Figure 2.

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Forest map of nicotine withdrawal’s effects on sports performance.

In contrast, nine studies (n = 561) explored the differences in exercise-related physical abilities before and after nicotine withdrawal. Notwithstanding the substantial heterogeneity among these studies (I^2 = 72%, p < 0.01), a random effects model was again used. These studies presented a negligible SMD, indicating no statistical significance (SMD = 0.03, 95% CI: −0.33 to 0.39) (Figure 3). However, gender subgroup analysis revealed that nicotine withdrawal in the mixed-gender group led to a significant improvement (SMD = 0.33, 95% CI:0.17 to 0.49), a result that was statistically significant (Figure S5). This outcome might be attributed to the larger sample size in this study, positively affecting the combined results (Figure S6). Subsequent subgroup analysis of nicotine intake frequency and withdrawal duration indicated that a lower intake frequency and short-term withdrawal resulted in a slight decline in physical ability. On the other hand, a higher frequency of nicotine intake (SMD = 0.58, 95% CI:0.06 to 1.09) and long-term withdrawal (SMD = 0.25, 95% CI:0.12 to 0.39) significantly improved the participants’ physical abilities, yielding statistically significant results (Figures 4 and 5).

Figure 3.

Figure 3.

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Forest map of nicotine withdrawal’s effects on exercise-related physical ability.

Figure 4.

Figure 4.

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Forest map of nicotine withdrawal’s effects on the exercise-related physical ability by nicotine frequency subgroup.

Figure 5.

Figure 5.

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Forest map of nicotine withdrawal’s effects on the exercise-related physical ability by nicotine duration subgroup.

3.4. Risk of bias

Our comprehensive risk of bias assessment indicated that 40% of the studies presented certain issues, 20% were evaluated as moderate risk, and 10% were considered high risk. An exhaustive bias assessment report can be found in Figure S7 in the online supplement.

3.5. Publication bias

A funnel plot was created to ascertain potential publication bias across studies. The symmetry observed in the distribution of the studies on both sides of the plot suggests a low incidence of bias among the included studies (Figure S8).

3.6. Sensitivity analysis

Sensitivity analyses were executed among the four studies on sports performance, sequentially removing one study at a time to assess the influence on the combined results. The results revealed a significant improvement in the study’s heterogeneity following the removal of Asha et al. [30]. This improvement could be attributed to the large sample size and unique outcome index value in their study. The remaining studies demonstrated reliability and stability following the removal (Figure S9). Sensitivity analyses were similarly conducted among the nine studies on physical abilities, revealing that the combined results remained robust and reliable, with no significant change observed.

4. Discussion

4.1. Main findings

The results of this meta-analysis affirm the notion of an enhanced sports performance in individuals undergoing nicotine withdrawal. Furthermore, the analysis underscores that nicotine withdrawal can cause a decrease in physical ability, albeit primarily in instances of short-term withdrawal spanning 12 to 24 hours. However, our subgroup analysis of protracted nicotine abstinence trials (48 hours or more) showcases an overall enhancement in physical capabilities among the participants.

The elucidation that moderate to long-term nicotine withdrawal significantly amplifies exercise performance and associated physical abilities in nicotine-dependent individuals is buttressed by a plethora of factors. These include an augmentation in body weight via increased muscle mass, improvement in endurance courtesy of elevated aerobic levels, amplification of muscle strength evidenced by superior grip strength, acceleration in movement speed, and the enhancement of bone density. Nonetheless, it is of paramount importance to note that brief periods of nicotine withdrawal can have a profound negative impact on cognitive performance. In instances of withdrawal extending no longer than 24 hours, all studies unambiguously indicate a deterioration in cognitive abilities, with a slowing of reaction speed, diminished attention, and an increase in anxiety levels being the most prevalent. This negative impact might indirectly cause a dip in sports performance.

Consequently, it can be logically inferred that while long-term nicotine withdrawal offers significant benefits for exercise performance and physical fitness in nicotine-dependent individuals, short-term withdrawal can adversely impact exercise-related abilities such as cognitive speed. Therefore, we strongly endorse cessation of smoking, particularly among athletes. Nonetheless, we do not recommend abrupt cessation prior to a major sporting event due to our discovery that nicotine intake can enhance performance in athletes accustomed to using nicotine 15–30 minutes prior to a competition. This enhancement may be attributed to the mitigation of withdrawal response. Interestingly, we also found that placebos can reduce the desire to smoke. Nevertheless, placebos appear to have no discernible effect on the cognitive impairment induced by short-term nicotine withdrawal.

4.2. Interpretation of the findings

The results of our study resonate with some aspects of earlier reviews published on the subject of smoking cessation. The decline in cognitive performance during nicotine withdrawal, as outlined by John R. Hughes et al. [27], is corroborated by our findings. Henri-Jean Aubin et al. [22] observed in their collective analysis of 62 studies that the majority of individuals experienced weight gain subsequent to nicotine withdrawal, a finding that aligns with our results. Similarly, Sommese, T et al. [28] confirmed the diminished responsiveness, hindered information processing, and heightened anxiety related to withdrawal symptoms in pilots after brief nicotine withdrawal. A study by Thomas S. Marzilli et al. [37] established that a non-nicotine placebo could also alleviate withdrawal response through a placebo effect. Consequently, we posit that the craving for smoking during withdrawal does not directly impact exercise performance. However, there are no systematic reviews and meta-analyses of the interplay between nicotine withdrawal and exercise performance among the studies published thus far. Although the effects of nicotine withdrawal on humans have been examined extensively, studies focusing on its impact on exercise performance are notably sparse.

Given the scarcity of relevant research literature and the absence of standardized outcome measurement indicators, our meta-analysis is subject to considerable heterogeneity. The conclusions drawn are significantly influenced by individual studies. For instance, our gender subgroup analysis of sports performance found that females outperformed males in terms of the difference in nicotine withdrawal. However, only one study, that of Anna et al. [29], was included as representative of the female subgroup. Therefore, future research on nicotine withdrawal should focus more on females to better promote the health and safety of the female nicotine-consuming population. Additionally, this analysis intended to explore the impact of nicotine addicts’ pre-withdrawal nicotine intake frequency on post-withdrawal physical ability and performance. However, as the mean value of nicotine intake frequency remained relatively constant while the variance showed significant fluctuation, the analytical results were somewhat constrained. Consequently, future meta-analyses should consider the duration of nicotine intake as a subgroup variable to achieve superior differentiation.

4.3. Nicotine withdrawal and exercise-related physical ability

In every meta-analysis of sports-related physical ability alterations attributable to nicotine withdrawal, we observed a significant Standard Mean Deviation (SMD). Sensitivity analysis results did not illustrate significant heterogeneity improvement after the sequential removal of each study, indicating the included literature exhibits a degree of reliability and stability. It is widely accepted that physical abilities experience an enhancement following nicotine withdrawal. However, our meta-analysis reveals that short-term nicotine withdrawal incites a certain deterioration in the physical capacity of subjects, while long-term withdrawal elicits an improvement. This conclusion is reinforced by the studies conducted by Kazhuo et al. [32] and Francisca et al. [52]. Moreover, Valer et al. [53] reported that participants’ task execution capabilities did not demonstrate improvement until six months post-nicotine withdrawal. Consequently, it is rational to assert that nicotine withdrawal is a protracted and challenging process, not a short-term result. Therefore, in vocations necessitating executive focus, such as pilots and drivers, short-term nicotine withdrawal during active duty is discouraged, as it could precipitate impairments in cognitive and executive functioning. This perspective aligns with Lawrence et al. [54]‘s research findings.

Additionally, in our gender-based subgroup analysis, only the mixed-gender group indicated some enhancement in physical abilities, while the male and female groups demonstrated no statistical significance, likely attributable to discrepancies in measurement methodologies and outcome indicators. Regarding literature review, only Andrew et al. [55] conducted a study on the differential effects of nicotine withdrawal on males and females through the administration of Progesterone. The remaining studies were predominantly animal-based. Consequently, the gender-specific differences in physical abilities resulting from nicotine withdrawal remain nebulous, highlighting the need for future studies to delve into the comparison of gender-based differences in nicotine withdrawal and to place greater emphasis on women’s cardiopulmonary health.

4.4. Nicotine withdrawal and sports performance

When assessing nicotine withdrawal in relation to sports performance, we derived even more optimistic results. Our meta-analysis results indicated a small SMD with substantial heterogeneity, demonstrating that nicotine withdrawal significantly enhances human sports performance, with statistically significant results. Such robust findings may be associated with the small number of included studies.

In the gender-based subgroup analysis for heterogeneity, we noted a more pronounced improvement in the female group of a single study [29] compared to the male group in the remaining study. As the duration of nicotine withdrawal was identical, subgroup analysis could not be conducted. Instead, the outcome index was chosen for analysis. Our results indicated that parameters akin to aerobic energy, such as movement duration and peak oxygen consumption, exhibited some improvement, whereas indicators resembling anaerobic capacities, like hand strength, displayed no significant improvement. Other factors such as sample size and nicotine intake frequency did not significantly impact the meta-analysis results. The enhancement in sports performance following nicotine withdrawal, as described above, is corroborated by the studies of Zandonai et al. [56] and Saul et al. [57]. The improvement in aerobic capacity following nicotine withdrawal is primarily attributable to the enhancement in cardiopulmonary function precipitated by nicotine withdrawal, which effectively thwarts the onset of conditions like coronary heart disease and cardiac blockage [58]. Therefore, it is reasonable to posit that cessation of smoking serves as the initial step in bolstering cardiopulmonary function.

4.5. Strengths and limitations

We employed diverse researchers to individually assess over 10,000 papers, with the aim of broadening the screening scope and minimizing the likelihood of omissions. As far as we are aware, this is the inaugural systematic review and meta-analysis on nicotine withdrawal and exercise performance. This landmark study paves the way for guiding exercisers on scientifically and rationally quitting smoking to enhance their sports performance.

However, our study has some limitations. 1) Language barriers posed challenges as we exclusively searched and included studies published in English, potentially omitting relevant studies published in other languages and subsequently increasing the risk of bias. 2) The quantity of available literature in this area is limited, yielding less comprehensive evidence. 3) Due to the dearth of literature, we did not refine the categorization of exercise types or standardize the outcome indicators. 4) Moreover, the vast chronological and geographical span of the included literature, coupled with the absence of a uniform standard for the research methods and measurement indicators, resulted in high heterogeneity among the studies. 5）Given that participants were trial controllers, it remains uncertain whether they can maintain sustained abstinence, particularly over extended durations. Furthermore, the carryover effect in the cross-over trials should not be disregarded as it could influence subsequent stages of withdrawal treatment [59].

It is imperative to highlight that the independent selection of two variables for analysis – namely, “sports performance” and “exercise-related physical abilities” – presents a methodological concern. Specifically, the absence of standardized metrics for these variables in the existing literature amplifies the risk of heterogeneity within our meta-analysis. To address this, cognitive abilities were employed as a surrogate measure for exercise-related physical capabilities. Additionally, the current body of research exhibits a lack of diversity with respect to abstinence duration. Most studies focus on short-term abstinence in relation to cognitive sports abilities, thereby neglecting the implications of long-term abstinence. Conversely, studies investigating sports performance primarily utilize medium- to long-term abstinence durations. This dichotomy further complicates meta-analytical efforts and compromises the objectivity of the resultant conclusions.

In light of these limitations, we proposed several recommendations (Table S5 in the online supplementary material) intended to bolster the quality and generalizability of future investigations into the impact of nicotine withdrawal on exercise performance. These recommendations principally address methodological elements such as study population, intervention (including nicotine withdrawal), outcome measures, and study design. Briefly, these recommendations are informed by the existing body of evidence and aim to enhance the rigor and reproducibility of subsequent research in this field.

5. Conclusions

In the absence of comparable preceding studies, we derived the following conclusions through an exhaustive review of the existing literature and a quantitative analysis of pertinent outcome indicators.

Medium to long-term nicotine withdrawal (≥3 months) significantly boosts exercisers’ exercise-related physical ability and sports performance; short-term nicotine withdrawal (≤24 hours) notably impairs exercisers’ sports performance and exercise-related physical ability. Athletes already dependent on nicotine may ingest nicotine 15–30 minutes prior to competitions to improve sports performance and physical function. As such, we advocate for exercisers to completely and permanently quit smoking to enhance sports performance, yet we do not advise sudden cessation before competitions. Owing to the scarcity of relevant articles, future research should strive to improve the quantity and quality of investigations in this domain. Although we found no clear definition of quantitative comparative criteria for sports performance, we could only analyze pre- and post-intervention outcomes. However, the underlying mechanisms through which nicotine withdrawal affects sports performance and exercise-related physical ability remain unclear, emphasizing the need for interdisciplinary collaboration between medical and sports research fields for comprehensive exploration.

6. Perspective

Owing to the limited existing research on the impact of nicotine withdrawal on exercise performance, the number of nicotine-dependent athletes who might opt for smoking cessation prior to competition to improve performance remains indeterminate. This uncertainty may arise from misinformation regarding the effects of smoking cessation. Through this study, we do not recommend that nicotine addicted athletes suddenly quit smoking before a competition as this can lead to a drastic reduction in sports performance. In addition, after analysis of large amount of existing literature we believe that athletes who are nicotine-dependent could potentially enhance their sports performance and physical function by consuming nicotine 15–30 minutes before the competition. However, we recommend that exercisers quit smoking for a long time and forever, as quitting for 3 months can significantly improve sports performance.

Acknowledgments

We thank all the authors of the literature included in the meta-analysis for providing data that can be used for reference in this field of research. We thank the School of Physical Education and Health of Zhejiang Normal University for supporting this article by providing a writing office environment. Thanks to all authors for their hard work.

Funding Statement

The author(s) reported there is no funding associated with the work featured in this article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Authors’ contributions

KZ B conceived and designed the study.KZ B, KZ, ZR H, BC C and XX Z performed the screening, study selection, data extraction, and analyzed and interpreted the data. KZ B drafted the manuscript with input from QD L, KZ, DY Z, QZ. All authors have read and approved the final version.

Data availability statement

All data and materials are from free and open databases, and no data have been modified or commercialized.

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