Mental Health and Physical Activity 7 (2014) 95e103
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Mental Health and Physical Activity
journal homepage: www.elsevier .com/locate/menpa
Efficacy of resistance training as an aid to smoking cessation:Rationale and design of the Strength To Quit study
Joseph T. Ciccolo a, *, David M. Williams b, c, Shira I. Dunsiger b, d, James W. Whitworth a,Aston K. McCullough a, Beth C. Bock c, d, Bess H. Marcus e, Merle Myerson f
a Department of Biobehavioral Sciences, Teachers College, Columbia University, 525 West 120th St., Box 199, New York, NY 10027, USAb Department of Behavioral and Social Sciences, Brown University, School of Public Health, Box G-S121-4, Providence, RI 02912, USAc Department of Psychiatry and Human Behavior, Alpert Medical School of Brown University, Box G-BH, Providence, RI 02912, USAd Centers for Behavioral and Preventive Medicine, The Miriam Hospital, 167 Point Street, Providence, RI 02903, USAe Department of Family and Preventive Medicine, U.C. San Diego Health Sciences, 9500 Gilman Drive, 0628, La Jolla, CA 92093, USAf Center for Cardiovascular Disease Prevention, Mount Sinai St. Luke's and Roosevelt Hospital, 1111 Amsterdam Avenue, New York, NY 10025, USA
a r t i c l e i n f o
Article history:Received 21 March 2014Received in revised form30 May 2014Accepted 30 May 2014Available online 21 June 2014
Background: Despite recent declines, cigarette smoking remains prevalent among individuals with lowerincome, less education, and those with mental illness or HIV. Exercise is promoted as a quitting aid;however, the evidence for this recommendation is equivocal. To date, the majority of studies have onlyexamined aerobic exercise; there is a poor understanding of the mechanisms of action; and there is anunder-representation of male smokers.Methods/Design: 206 male and female smokers will receive a smoking cessation education session priorto being randomized into a 12-week Resistance Training (RT) or Wellness Contact Control group. Bothgroups will have the option of using nicotine replacement therapy (NRT), and both will meet on-sitetwice per week during the intervention (24 total sessions). Follow-up assessments will occur at theend of the 12-weeks (3-month), and at a 6-month and 12-month (post-randomization) visit. Participantswill not receive any additional cessation treatment during follow-up; however, the RT group will receivea 9-month membership to a fitness center to encourage continued resistance training as a way tomaintain cessation. The primary outcome is salivary-cotinine-verified 7-Day Point Prevalence Abstinenceat the 3-month assessment, and at the 6 and 12-month follow-ups. Secondary outcomes include effectsof resistance training on nicotine withdrawal, indicators of mental health, and markers of disease risk.Discussion: This study will produce new data on the efficacy of resistance training for smoking cessation,the potential mechanisms of action that may support its use, and the effects it has on markers of diseaserisk in smokers.
Each year, tobacco use kills nearly 6 million people and costsmore than half a trillion dollars worldwide (WHO, 2013). In theUnited States (US), the primary method of tobacco use is cigarettesmoking, and approximately 19.9% of men and 15.2% of womencurrently smoke (Schiller, Ward, & Freeman, 2013). These rates are
known to differ by other demographic variables such as race,education, and income level (CDC, 2012; Schoenborn, Adams, &Peregoy, 2013) and they differ by current health status. Forexample, the rate of cigarette smoking is estimated to be highestamong persons living with human immunodeficiency virus (HIV;59%e85%; Marshall et al., 2011; Tesoriero, Gieryic, Carrascal, &Lavigne, 2010) and those with a diagnosed mental illness (36.1%;CDC, 2013).
In the US, cigarette smoking and exposure to secondhand smokeis estimated to cause 480,000 deaths annually, or about one out ofevery five deaths (CDC, 2008; USDHHS, 2014). Lung cancer claimsthe most lives, followed by ischemic heart disease, and chronicobstructive pulmonary disease (COPD; CDC, 2008). In total, moredeaths are caused by tobacco use in the US than by all deaths from
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illegal drug and alcohol use, HIV/AIDS, motor vehicle injuries,murders, and suicides combined (USDHHS, 2004). Fortunately,quitting smoking results in a number of short and long-term ben-efits. For example, the risk of developing heart disease drops by 50%within one year after quitting, and the risk for a stroke can fall toabout the same as a nonsmoker's, 2e5 years after quitting(USDHHS, 2010). Other risks, such as cancer of the mouth or throatare cut in half five years after quitting, and the risk of dying fromlung cancer drops by half 10 years after quitting (USDHHS, 2010).Smoking cessation can also improvemental health, as it is known tobe associated with reduced depression, anxiety, and stress andimproved mood and quality of life (Taylor et al., 2014).
Recent estimates indicate that the majority of US smokerswould like to quit, with 45.8% having tried in the past year(Schoenborn et al., 2013). Unfortunately, less than 5% of those whoattempt to quit are able to maintain long-term abstinence (Raffulet al., 2013), particularly greater than six months (Murthy &Subodh, 2010). There are several prescription and over-the-counter medications that have been shown to nearly double thesuccess rate of smoking cessation when compared to a placebo(Herman & Sofuoglu, 2010); however, cost, access, and theperception of medication risk are well known barriers to use(Foulds et al., 2013). In addition, the weight gain associated withquitting can be problematic for both men and women, as currentevidence indicates that post-cessation weight gain can range from4 to 10 kg (Aubin, Farley, Lycett, Lahmek,& Aveyard, 2012). Notably,the increases in body weight following smoking cessation may beattributed to a lower metabolic rate and increased amount of bodyfat (Kleppinger, Litt, Kenny, & Oncken, 2010; Pistelli, Aquilini, &Carrozzi, 2009). Such changes can significantly diminish the posi-tive health effects of smoking cessation via associated reductions inglucose metabolism (Yeh, Duncan, Schmidt, Wang, & Brancati,2010), lung function (Chinn et al., 2005), and increases in the riskof developing type 2 diabetes (Luo et al., 2013) and hypertension(Gratziou, 2009).
The U.S. Department of Health and Human Services currentlyadvocates the use of exercise as an aid to quitting (USDHHS, 2008),as do researchers, tobacco treatment specialists and formersmokers (Everson, Taylor, & Ussher, 2010; Haasova et al., 2014).However, the overall evidence for using exercise as an aid isequivocal. Specifically, a 2012 Cochrane review determined thatlarger, adequately powered, sufficiently intense interventions withequal contact control conditions are needed (Ussher, Taylor, &Faulkner, 2012). The authors identified a number of limitations ofprevious research that included a lack of testing potential mecha-nisms of action (e.g., reduction in nicotine withdrawal symptoms),a female-only sample, and a strict focus on using aerobic exercise.As such, newer, rigorous research is needed to elucidate the roleexercise can play in aiding smoking cessation, particularly for malesmokers and anyone who would prefer to engage in variousdifferent physical activity modalities. This could potentiallyenhance compliance and ultimately prevent relapse.
In a prior pilot study, we explored the feasibility of resistancetraining (i.e., weight training) as an aid to smoking cessation(Ciccolo et al., 2011). Briefly, 12 male and 13 female smokersreceived a 20-min smoking cessation counseling session andNicotine Replacement Therapy (NRT). Participants were then ran-domized into a two-session per week, 12-week resistance trainingor contact control program (i.e., 24 total sessions). At the end oftreatment, carbon-monoxide (CO)-verified 7-day point prevalenceabstinence (PPA) rates were 46% for the resistance training groupand 17% for contact control (OR 4.3, 95% CI ¼ 0.7e27.8). Addition-ally, participants in the resistance training group had more favor-able changes in body weight (Cohen's d ¼ �0.7) and body fat(d ¼ �0.8) when compared to the control.
These pilot results warrant additional research, as the datasuggest that resistance training could (1) be a potential aid forsmoking cessation and (2) provide smokers with a method toreduce other health risks when trying to quit. More specifically, thepotential mechanisms supporting resistance training as an aid forsmoking cessation are that it could beneficially affect some of themost well known predictors of relapse, such as negative affect(Leventhal et al., 2013) and sleep disturbance (Hamidovic& deWit,2009), as well as barriers to quitting, such as weight gain (Pistelliet al., 2009). For example, studies have shown that resistancetraining can reduce many of the same negative affective statesfrequently reported during nicotine withdrawal, such as tension,anxiety, and depression (Arent, Landers, Matt,& Etnier, 2005; Singhet al., 2005). Other research has shown that there is a significantassociation between resistance training and increased quality ofsleep (Yang, Ho, Chen, & Chien, 2012); and the effects of resistancetraining on metabolism and body composition have been rigor-ously tested and are well established (Strasser, Siebert, &Schobersberger, 2010). In addition to these potential positive ef-fects, the health benefits gained from resistance training could alsobe particularly helpful for smokers, as resistance training has beenshown to improve lung function (Singh, Jani, John, Singh, & Joseley,2011), blood lipids (Kelley & Kelley, 2009), and blood glucosecontrol (Strasser et al., 2010). All of these factors are known in-dicators of disease risk that are also significantly associated withsmoking (USDHHS, 2014).
As such, the purpose of this paper is to outline the rationale anddesign of Strength To Quit, a large, laboratory-based, randomizedcontrolled trial (RCT) testing the use of resistance training as an aidto smoking cessation. Strength To Quit was specifically designed toexamine the following three questions: (a) What is the efficacy ofresistance training as an aid to smoking cessation for male andfemale smokers? (b) What are the psychological and physiologicalmechanisms of the effects of resistance training on smokingcessation? and (c) Does resistance training attenuate detrimentalchanges in markers of disease risk associated with quitting (e.g.,body fat gain)?
1.1. Study methods
1.1.1. Study designStrength To Quit uses a 2-group design inwhich 206 participants
will be randomized into 12-week Resistance Training (n ¼ 103) orWellness Contact Control (n ¼ 103) conditions. A stratified blockrandomization procedure is used to achieve balance between thetwo groups on gender and intention to use the nicotine patch. Allparticipants receive a brief smoking cessation education sessionprior to being randomized. Both groups meet on-site twice perweek during the 12-week program (24 total sessions), and follow-up assessments occur at the end of the 12-weeks (3-month) and ata 6-month and 12-month (post-randomization) follow-up (SeeFig.1). The primary outcome is salivary-cotinine-verified 7-Day PPAmeasured at each of the follow-up assessments.
1.1.2. Participants and eligibilityEligible participants aremale and female smokers, age� 18, who
have a desire to quit smoking and have regularly smoked five ormore cigarettes a day for at least the past 12 months. Potentialparticipants are excluded if they currently engage in any combina-tion of aerobic exercise or resistance training for >60 min/week orhave over the past 3 months, currently use smokeless tobacco, aretakingmedication toquit smoking, or areparticipating in anongoingsmoking cessation treatment.Womenwhoarepregnantor planningto become pregnant are excluded. Anyone with cardiovascular orpulmonary disease (e.g., coronary artery disease, emphysema), and
Fig. 1. Study design.
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anyonewith orthopedic limitations that would prevent their abilityto complete a full-body resistance training program are alsoexcluded. Lastly, participantsmust be able to speak and readEnglish,andhavenoplans tomoveout of the areawithin thenext 12months.
1.1.3. Procedures1.1.3.1. Recruitment. Advertisements for this study are posted innewspapers, at subway and bus stops, on the Internet (e.g.,Craigslist), on bulletin boards in the local area (i.e., flyers), and onthe radio. The bulk of advertisements are placed in a free metronewspaper that is circulated throughout the New York City subwaysystem, as it has a large readership that includes significantnumbers of racial and ethnic minorities.
1.1.3.2. Pre-randomization sessions. Individuals who appear to beeligible at the phone screen are asked to attend three sessions priorto randomization. The first session is an orientation to provideadditional information about the study and to obtain informedconsent. The second and third sessions are used to collect surveydata and conduct clinical assessments (See Fig. 1). After completingthe three pre-randomization sessions participants are eligible to berandomized and begin the 12-week program.
1.1.3.3. Baseline smoking education and randomization. At the firstsession of the 12-week program, all participants receive a brief (20-min) smoking cessation education session based on the Centers forDisease Control and Prevention's (CDC) “You Can Quit Smoking”
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consumer guide consisting of a manualized, five-step program (i.e.,get ready, get support, learn new skills and behaviors, get medi-cation and use it correctly, and be prepared for difficult situations).Participants are asked to set their quit day one week from thiseducation session. Immediately following the smoking education(i.e., at the same session), participants are randomized into eitherthe Resistance Training or Wellness Contact Control condition.Specifically, participants open a sequentially numbered envelope,which reveals the group allocation. A blinded, off-site biostatisti-cian previously determined the randomization sequence.
1.1.3.4. Provision of the nicotine patch. All participants are given theoption of using nicotine replacement therapy during the trial. Useof the nicotine patch is in accordance with the current ClinicalPractice Guidelines from the United States Department of Healthand Human Services (Fiore et al., 2008). If a participant chooses touse nicotine patches, s/he is asked to use the patch at the beginningthe first session of week 2 (quit day). Each week thereafter par-ticipants are given a two-week supply of the nicotine patches on anas-needed basis. Participants who smoke more than 10 cigarettesper day are instructed to use a 21 mg patch for six weeks (Weeks2e7), tapered to a 14 mg patch for the next two weeks (Weeks8e9), and a 7 mg patch for the final two weeks (Weeks 10e11).Participants who smoke between 5 and 10 cigarettes per day areinstructed to begin with a 14 mg patch for six weeks (Weeks 2e7),which is tapered to a 7 mg patch for the next four weeks (Weeks8e11). The 10 weeks of nicotine patch use and dose tapering pro-tocol are consistent with clinical recommendations (Fiore et al.,2008). All participants are asked to discontinue patch use after 10weeks (beginning of week 12) in order to obtain valid saliva co-tinine assessment at the post-treatment assessment session.
1.1.4. Experimental conditions1.1.4.1. Resistance training program. Participants in this study armattend two, 45e60-min, progressive resistance training sessions perweek for 12 weeks. The program manipulates the key resistancetraining program variables of volume (repetitions/sets) and in-tensity (% of 1-repetition maximum; 1-RM), while maintaining aformat of a 5-min (aerobic) warm-up, 35e50 min of resistancetraining and a 5-min cool-down (stretching). Specifically, partici-pants are guided through a 10-exercise, full-body routine by studystaff. For the first 2e3weeks, participants complete 1e2 sets of eachexercise at an intensity that elicits muscular fatigue within 10e15repetitions (approximately 65%e75% of 1-RM). From weeks 4e12,participants complete 2e3 sets per exercise, and the weight issystematically increased to elicit muscular fatigue within 8e10repetitions (75%e80% of 1-RM). The rest interval between sets isheld constant across the 12 weeks at 30 se1.5 min. This program isconsistent with the American College of Sports Medicine's PositionStand on ProgressionModels in Resistance Training (Ratamess et al.,2009). Similar programs are known to produce increases in bothmuscular strength and aerobic fitness (Tanaka & Swensen, 1998).
1.1.4.2. Wellness contact control condition. Participants in this studyarm are required to attend the same number of sessions, for thesame amount of time as those in the Resistance Training group.Each session includes a handout on pertinent healthy lifestyletopics for adults (e.g., human anatomy, sex and relationships), aninformational video, and a practical component/demonstration.None of the sessions include information on smoking, smokingcessation or exercise. Participants are asked to not change theircurrent exercise behavior during the 12-week intervention.
1.1.4.3. Exercise maintenance program. At the end of the 12-weekprogram, participants in the Resistance Training group receive a
9-month membership to a local fitness center, and they receive anindividualized, progressive resistance training plan, which is anextension of the routine completed during the intervention. This ismeant to provide the participants with the knowledge and guid-ance needed to facilitate continued training during the follow-upperiod. Study staff arrange initial appointments between researchparticipants and the fitness center, but there is no furtherinvolvement from research staff once the initial appointment isarranged. For equity, participants in the Wellness Contact Controlalso receive a 9-month fitness center membership after their 12-month follow-up visit (i.e., after they have completed the trial).Card swipe data detailing the time and date of each visit to thefitness center are collected in the Resistance Training group at the 6and 12-month follow-ups.
1.1.5. IncentivesCompliance with the resistance training and wellness control
programs is crucial to addressing the primary aims of the study (i.e.,testing the efficacy of resistance training), therefore, monetary in-centives are given to the participants as compensation for theirtime, effort and attendance. In both groups, participants are paid$25 at week 4, $50 at week 8, and $75 at week 12, with a $50 bonusfor completing �22 sessions. In addition, all participants receive$50 for attending each of the three follow-up assessments (3, 6, and12 month), with a $50 bonus for completing all three of the follow-up assessments. Incentives are not dependent on smoking status.
1.1.6. MeasuresParticipants complete a battery of assessments at baseline,
weekly during the intervention, at the end of treatment (3-month),and at the 6 and 12-month follow-ups (see Fig. 2).
1.1.6.1. Primary outcome. The primary outcome is salivary-cotinine-verified 7-Day PPA at the 3-month assessment, and atthe 6 and 12-month follow-ups. In addition, smoking status isassessed via self-report and measured objectively with a handheldbreath carbon monoxide monitor at each of the two weekly ses-sions during the 12-week program, and at the 6 and 12-monthfollow-ups. Specifically, participants are asked whether or not“even a puff”was takenwithin the last 7 days, 24 h, and the date ofthe last puff. This allows for an examination of the number ofsmoking cessation outcomes, including: (a) initial abstinence (24-h abstinence); (b) time to first lapse (first smoking eventfollowing initial abstinence); (c) time to relapse (smoking at least5 cigarettes/day for 3 consecutive days); (c) prolonged abstinence(reaching post-treatment without relapse following a two-weekgrace period after quit day); and (d) 7-day PPA. These outcomemeasures will be determined by self-report and confirmed byobjective smoking assessments.
1.1.6.1.1. Covariate: nicotine replacement. Nicotine patch use isassessed at every session. Participants are asked if they used anicotine patch since their last visit, howmany, and if they have hadany side effects. They are also asked if they have used any othersupplemental nicotine (e.g., gum, lozenge), smoking cessationmedications (e.g., varenicline, bupropion), or an electronic cigarette.
1.1.6.2. Secondary outcomes. Secondary outcomes are divided intotwo major categories: (1) potential mechanisms of action; and (2)markers of disease risk (See Fig. 2).
1.1.6.2.1. Potential mechanisms of action measures. The potentialmechanisms of action are measured at each session during the 12weeks.
1.1.6.2.1.1. Withdrawal symptoms. Nicotine withdrawal symp-toms are regularly reported as the major barrier to successfulsmoking cessation (Piasecki, 2006). To be consistent with other
Assessment Baseline Weekly During Intervention
End of Intervention
(3-Month)
6-MonthFollow-up
12-MonthFollow-up
Smoking-Related VariablesSmoking History √Smoking Status √ √ √ √ √Nicotine Patch Use √ √ √ √Salivary Cotinine √ √ √Carbon Monoxide √ √ √ √ √Potential Mechanisms of Action Measures Mood and Physical Symptoms Scale (MPSS)
√
Strength of Desire to Smoke (SoD)
√
Affect (Feeling Scale, Felt Arousal Scale)
√
Leeds Sleep Evaluation Questionnaire
√
Markers of Disease RiskBody Weight/Composition √ √ √ √Lung Function (FVC, FEV1) √ √ √ √Blood Lipids (total cholesterol, triglycerides, high and low density lipoproteins)
Center for Epidemiologic Studies Depression Scale (CESD)
√ √ √ √
Potential ModeratorsDemographics √Fagerström Test of Nicotine Dependence (FTND)
√ √ √ √
Fig. 2. Schedule of assessments.
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research in this area, the Mood and Physical Symptoms Scale(MPSS; West & Hajek, 2004) is used to measure nicotine with-drawal symptoms. The MPSS is a 7-item survey that shows goodsensitivity to changes in craving and withdrawal symptoms over24 h abstinence, and compares well with other scales of nicotinewithdrawal (West, Ussher, Evans, & Rashid, 2006).
1.1.6.2.1.2. Cravings. Cigarette cravings and urges to smoke arereported by nearly all smokers following abstinence (Ussher,Beard, Abikoye, Hajek, & West, 2013). The Strength of Desire toSmoke (SoD), a single item measure (How strong are yoursmoking urges just now?), is used to assess cigarette craving. TheSoD has been used in a number of previous studies testing theeffects of aerobic exercise on cigarette craving with adequatereliability, validity and internal consistency (Taylor, Ussher, &Faulkner, 2007).
1.1.6.2.1.3. Affect. Negative shift in affective valence is oftenexperienced during nicotine withdrawal and is a consistent, in-dependent predictor of relapse (Leventhal et al., 2013). There iscurrently a substantial amount of evidence detailing the acutebenefits of resistance training on various mood states and well-being (Arent et al., 2005; Bibeau, Moore, Mitchell, Vargas-Tonsing, & Bartholomew, 2010). As such, affective valence isacutely assessed; this is by using the single-item Feeling Scale. Thescale ranges from �5 (very bad) to þ5 (very good) with 0 (neutral)at the mid-point. The Feeling Scale has been used in researchtesting the effects of aerobic exercise on nicotine withdrawal
with adequate reliability, validity and internal consistency (Tayloret al., 2007).
1.1.6.2.1.4. Sleep. Disturbed sleep is a primary symptom ofnicotine withdrawal (Hamidovic & de Wit, 2009), and can interferewith the ability to quit smoking or maintain long-term abstinence(Riemerth, Kunze, & Groman, 2009). Chronic and acute resistancetraining has been shown to result in improved quality of sleep inindividuals with and without sleep problems (Viana et al., 2012;Yang et al., 2012). Thus, participants' quality of sleep on the previ-ous night is measured; this is by using the Leeds Sleep EvaluationQuestionnaire (LSEQ), which has shown adequate consistency,reliability and validity in other research (Tarrasch, Laudon, &Zisapel, 2003).
1.1.6.2.2. Markers of disease risk. The markers of disease risk aremeasured by staff who are blind to the participant's condition. Allassessments are taken at baseline and each follow-up.
1.1.6.2.2.1. Body weight and composition. Unlike the majority ofstudies on exercise and smoking cessation, both body weight andcomposition are monitored in this study. These assessments willidentify any changes in fat mass that occur over the 12-month trial.Body weight is measured using a calibrated electronic scale(Cosmed, Inc., Concord, CA, USA). Body composition is determinedusing whole-body air displacement plethysmography (Bod Pod,Cosmed, Inc., Concord, CA, USA) with estimated thoracic gas vol-ume according to the manufacturer's guidelines. Participants wear
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minimal clothing for each of these tests. The validity of airdisplacement plethysmography for male and female adults hasbeen established (Baracos et al., 2012).
1.1.6.2.2.2. Lung function. Smokers are at high-risk for devel-oping impaired lung function (Nagelmann, Tonnov, Laks, Sepper, &Prikk, 2011). Resistance training can improve lung functioning(Singh et al., 2011) and is therefore monitored in this study. Lungfunction is assessed using a portable spirometer (Spirobank GSpirometer, Medical International Research, Inc., Waukesha, WI,USA). Forcedexpiratory volume in one second (FEV1) and forced vitalcapacity (FVC) isdetermined fromthree trials, and thevalues forFEV1and FVC are selected that fulfill the reproducibility and acceptabilitycriteria in accordance with the American Thoracic Society criteria(Miller et al., 2005). Absolute values and percentages of predictedvalues of the lung function parameters will be used for analysis.
1.1.6.2.2.3. Blood sample. Several studies have reported smokersto be at increased risk for developing insulin resistance (Luo et al.,2013) and dyslipidemia (Gepner et al., 2011). Resistance traininghas been shown to result in statistically significant reductions inglycosylated hemoglobin (HbA1c), a marker of blood glucose con-trol (Strasser et al., 2010), and it may improve blood lipids (e.g., totalcholesterol, triglycerides; Kelley & Kelley, 2009). As such, partici-pants provide a sample of blood that is analyzed for HbA1c, totalcholesterol, triglycerides, and high and low density lipoproteins. Inaddition, C-reactive protein (CRP) ismeasured, as it has been shownto be chronically elevated in smokers (Dietrich, Garcia, de Pablo,Schulze, & Hoffmann, 2007), and long-term elevations are consis-tently associated with an increased risk of coronary heart diseaseand stroke (Kaptoge et al., 2010). While research has shown thatengaging in a resistance training program can lead to significantreductions in CRP concentrations (Donges, Duffield, & Drinkwater,2010), we are unaware of any published study that has investigatedthe relationships among CRP, resistance training and smoking.
1.1.6.2.2.4. Physical fitness. Muscular strength (Ruiz et al., 2008)and aerobic capacity (Barry et al., 2014) are well-known markers ofdisease risk and are predictors of mortality. The resistance trainingprogram used in this study is expected to impact both muscularstrength and aerobic capacity (Tanaka& Swensen,1998), thus, eachis assessed. Muscular strength is measured using upper (chestpress) and lower (leg extension) body exercises using the AmericanCollege of Sports Medicine's (ACSM) protocol for 1-RM testing(ACSM, 2014). Aerobic capacity is assessed six-minute treadmillwalk test (6MWT; Laskin et al., 2007). Both measures are regularlyused to determine physical fitness in diseased and healthy pop-ulations, and both have acceptable validity and reliability (ACSM,2014; Laskin et al., 2007).
1.1.6.2.3. Mental health assessments. Cigarette smokers aresignificantly more likely than non-smokers to report having amental illness (SAMHSA, 2013), and smokers with a mental illnessmay be more likely to make a quit attempt (Morris, Burns,Waxmonsky, & Levinson, 2014). As such, the following assess-ments are taken at baseline and each follow-up.
1.1.6.2.3.1. Anxiety. Smokers are well known to have elevatedlevels of anxiety (Moylan, Jacka, Pasco, & Berk, 2012) and regularresistance training has been shown to reduce anxiety in a variety ofpopulations (Hale & Raglin, 2002; Herring, Jacob, Suveg, Dishman,& O'Connor, 2012). Trait anxiety is measured using the traitcomponent of the State-Trait Anxiety Inventory (STAI; Spielberger,Gorsuch, Lushene, Vagg, & Jacobs, 1983). This 20-item scale mea-sures items (e.g., I worry too much over something that reallydoesn't matter) on a 4-point scale from “Almost Never” to “AlmostAlways.” The scale has shown adequate consistency, reliability andvalidity in a wealth of research (Spielberger, 1989).
1.1.6.2.3.2. Depression. Similar to anxiety, smokers are alsoknown to have elevated levels of depression (Tjora et al., 2014) and
reductions in depression have been reported after resistancetraining in clinical and non-clinical samples (Cooney et al., 2013;Singh et al., 2005). The 10-item Center for Epidemiologic StudiesDepression Scale (CES-D) is used to measure depression symptomsover the past week (Bj€orgvinsson, Kertz, Bigda-Peyton, McCoy, &Aderka, 2013). Items are rated on a 4-point scale from 0 (less thanone day) to 4 (5e7 days). The scale has been validated(Bj€orgvinsson et al., 2013) and used in other smoking cessationtrials (e.g., Hennrikus et al., 2010).
1.1.6.3. Potential moderators. Each of the following measures willbe collected at baseline and tested as a potential moderator of theprimary outcome.
1.1.6.3.1. Demographics. This questionnaire asks for informationon the participant's age, gender, race, ethnicity, relationship status,family size, occupation, total household income and level ofeducation.
1.1.6.3.2. Nicotine dependence. The Fagerstr€om Test for NicotineDependence (FTND) is used to measure nicotine dependence. TheFTND is a 6-item measure with excellent reliability and validity insmoking research. It is considered the standard measure of nicotinedependence (Heatherton, Lozlowski, Frecker, & Fagerstrom, 1991).
1.1.6.4. Manipulation check. The resistance training completed on-site as part of the 12-week program is directly observed byresearch staff. Compliance to the program will be calculated as thenumber of sessions attended over the 12-weeks. Additional trainingoutside of the on-site sessions is discouraged for the ResistanceTraining group, as is any exercise for the Wellness Control group.To monitor this throughout the trial, the past week ModifiableActivity Questionnaire (Pettee Gabriel, McClain, Schmid, Storti, &Ainsworth, 2011) is administered at weeks 4, 8, 12, and at eachfollow-up assessment. In addition, for participants in the ResistanceTraining group, frequency of attendance at the fitness center duringthe follow-up period ismonitored via their card swipe data; and anychanges in fitness will be identified with the physical fitness tests.
2. Analysis
2.1. Sample size and power considerations
The sample size is designed to have 80% power for testing thenull hypothesis that the intention to treat effect is zero, versus thetwo-sided alternative. In the analysis and sample size calculations,all dropouts will be coded as treatment failures (smokers). Thisapproach has empirical justification in studies of smoking cessation(Lichtenstein & Glasgow, 1992). Sample size estimates for this trialwere based on 6-month quit rates of 38% in the Resistance Traininggroup versus 17% in the Contact Control (Ciccolo et al., 2011). Whileit is possible that effectsmay be stronger orweaker at the 12-monthfollowup (compared to those currently estimated from the6-monthfollow-up in the pilot study), we do not anticipate significant dif-ferences from 6-month quit rates. Thus, using a multiplicity-adjusted two-tailed alpha level of 0.05/3 (1 outcome � 3 timepoints), a sample size of 103 participants per armwill be needed tohave at least 80% power to detect between-group differences inobjectively verified 7-day PPA at each of the follow-up times, for atotal sample size of 206.
2.2. Planned analysis for primary outcomes
Using a longitudinal regression model implemented withGeneralized Estimating Equations (GEEs; Zeger& Liang,1986), withrobust standard errors, the effect of treatment assignment on 7-dayPPA will be tested. Specifically, the probability of being quit will be
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regressed on treatment assigned to, as well as any baseline vari-ables that are not equally distributed across the two conditions.Furthermore, we will explore the effect of intention to use NRT andself-reported use on the estimated treatment effect by includingeach as a covariate in the model. Similar analyses will be conductedto examine the effects of treatment on prolonged abstinence.
2.3. Planned analysis for secondary outcomes
The treatment effects of resistance training on potential mech-anisms of action will be tested using a series of longitudinalregression models implemented with GEEs (Zeger & Liang, 1986).The weekly measure of the mechanism (e.g., nicotine withdrawalsymptoms) will be regressed on the treatment assignment, whilecontrolling for baseline values of the mechanism, quit status at thetime the mechanism was assessed, and potential confounders, asdetermined by preliminary analyses.
To examine potential mechanisms as predictors of smokingcessation outcomes, 7 day PPA, time to first lapse, and time to thestart of relapse during the 12-week program will be considered assmoking endpoints. This will allow for a focus on quitting outcomesand on data that is reported before a participant returns to smok-ing. Time to the start of relapse requires first identifying a relapse,as defined by 5 cigarettes per day on 3 consecutive days, and thenusing the first cigarette smoked during the 3-day relapse process asthe start of relapse. When the outcome of interest is time to adefined event (i.e., first lapse, start of relapse), survival analysis(Hosmer & Lemeshow, 1999) will be used to model the risk oflapsing (relapsing) over time. Survival analysis makes use of the fulldata set to inform an estimate of the risk of lapse/relapse. That is,each participant contributes two outcome variables to the model:T*i, time to first lapse/relapse and Ci, censoring time. For partici-pants who lapse/relapse before the end of treatment, T*i < Ci; forthose who do not lapse/relapse before end of treatment or whodiscontinue the study protocol before lapsing/relapsing, T*i > Ci.Thus, the model uses Ti ¼ min {T*i, Ci} as the response for eachparticipant. Using a Cox model (Cox, 1972; Therneau & Grambsch,2000), we can write the hazard function (which can be thoughtof as the number of lapses/relapses per patient-day of follow-uptime) as a function of a baseline hazard rate l0(t) and covariatesX(t). Note that the set X(t) can include both time-variant and time-invariant covariates. Lastly, when the outcome of interest is 7-dayPPA, logistic regression models will be used to regress the logit ofthe probability of 7-day PPA on withdrawal symptoms over time(for example), when controlling for treatment assignment andpotential confounders of the association under consideration.
The effects of treatment onmarkers of disease risk will be testedat each time point (the 3, 6, and 12-month follow-ups) using arepeated measures regression model implemented with GEEs withrobust standard errors. These adjusted standard errors will accountfor repeatedmeasurements. Appropriate link functionswill be used(e.g., identity link for continuous outcomes). If needed, a normal-izing transformation to the continuous response measures (such astaking the logarithm of lung function) before proceeding with theanalysis will be completed. Models will also control for baselinevariables that are not equally distributed across treatment condi-tions. Lastly, the association between smoking outcomes andchanges in markers of disease risk (i.e., from baseline to follow-up,3, 6, and 12 months) will be examined using a longitudinalregression model implemented with GEEs with a logit link (whichwill estimate, for example, the effect of changes from baseline totime t in markers on the logit of 7-day PPA at time t, controlling forpotential confounders).
Finally, using a similar set of analyses to those planned for theprimary outcome, we will examine potential moderators of the
treatment effect on smoking outcomes (7 day PPA and prolongedabstinence). Specifically, models will include the main effect of thepotential moderator (gender for example), the main effect oftreatment and the interaction between the two.
3. Limitations
There are some limitations with the Strength To Quit trial thatneed to be acknowledged. First, the large incentives used toenhance compliance reduce the likelihood that the results from thisstudy would easily translate into the community setting. However,because both conditions receive the same incentives and the in-centives are not contingent on quitting, generalizability will belimited only to the extent that incentives moderate the effects ofresistance training on smoking outcomes (i.e., the extent to whichthe differences between treatment conditions would be different inthe absence of incentives). Moreover, the purpose of the StrengthTo Quit trial is to test the efficacy of resistance training as an aid forsmoking cessation. If initial efficacy can be established, furtherresearchwill bewarranted, particularly studies that offer smokers achoice of different exercise programs that have been shown to beeffective for aiding smoking cessation. Second, the mechanisms ofaction that are hypothesized to support sustained smoking absti-nence during the follow-up period via continued resistancetraining (i.e., consistent reductions in negative affect, sleep distur-bance, weight gain) are not monitored. As such, future studiesshould be designed in a way that would allow this data to becollected (e.g., using ecological momentary assessment) beyond theintervention period.
4. Discussion
To our knowledge, this is the first large-scale randomizedcontrolled trial to test the use of resistance training as an aid tosmoking cessation. This trial was designed to produce new datathat will address some of the limitations of previous work on ex-ercise and smoking cessation. For example, the vast majority ofstudies have used an aerobic-only exercise program, with the use ofa female-only sample (Ussher et al., 2012). Furthermore, the hy-pothesized mechanisms of action (e.g., reduced negative affect,withdrawal symptoms) supporting a reduction in smoking withexercise have largely been studied outside the context of making aquit attempt (Roberts, Maddison, Simpson, Bullen, & Prapavessis,2012; Taylor et al., 2007). As such, the results of this study willadd to the literature base and inform current public health initia-tives that promote the use of exercise as a method to achievesmoking cessation. Lastly, data from this study will reveal any ef-fects resistance training may have on markers of disease risk inmale and female smokers. While the beneficial health effects ofresistance training are well known and accepted, the various effectsresistance training may have on male and female smokers whentrying to quit has not been rigorously examined.
Acknowledgments
The project described in this manuscript is supported by a grantfrom the National Heart, Lung, and Blood Institute (R01 HL117345to J.T.C.).
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