Abstract
Higher preoperative physical activity (PA) strongly predicts higher post-operative PA in bariatric surgery (BS) patients, providing rationale for preoperative PA interventions (PAIs). However, whether PAI-related increases can be maintained post-operatively has not been examined. This study compared PA changes across pre-(baseline, post-intervention) and post-operative (6-month follow up) periods in participants randomized to 6 weeks of preoperative PAI or standard care control (SC). Of 75 participants initially randomized, 36 (PAI n = 22; SC n = 14) underwent BS. Changes in daily bout-related (⩾10-min bouts) moderate-to-vigorous PA (MVPA) and steps were assessed via the SenseWear Armband monitor. PAI received weekly counseling to increase walking exercise. Retention (86%) at post-operative follow up was similar between groups. Intent-to-treat analyses showed that PAI vs SC had greater increases across time (baseline, post-intervention, follow up) in bout-related MVPA minutes/day (4. 3 ± 5.1, 26.3 ± 21.3, 28.7 ± 26.3 vs 10.4 ± 22.9, 11.4 ± 16.0, 18.5 ± 28.2; P = 0.013) and steps/day (5163 ± 2901, 7950 ± 3286, 7870 ± 3936 vs 5163 ± 2901, 5601 ± 3368, 5087 ± 2603; P o0.001). PAI differed from SC on bout-related MVPA at post-intervention (P = 0.016; d = 0.91), but not follow up (P = 0.15; d = 0.41), and steps at post-intervention (P = 0.031; d = 0.78) and follow up (P = 0.024; d = 0.84). PAI participants maintained preoperative PA increases post-operatively. Findings support preoperative PAIs and research to test whether PA changes can be sustained and influence surgical outcomes beyond the initial post-operative period.
INTRODUCTION
Most bariatric surgery (BS) patients rarely engage in structured or purposeful exercise, reflected by little or no accumulation of daily or weekly moderate-to-vigorous physical activity in bouts lasting ⩾ 10 min (that is, bout-related MVPA). 1, 2 While research in both non-surgical and BS populations suggests that engagement in bouts of MVPA as short as 10 min towards a daily total might have important health and/or weight loss benefits for BS patients, [2] [3] [4] [5] [6] roughly two-thirds do not perform any bout-related MVPA and nearly all (95-98%) are inactive according to public health recommendations (that is, performing o150 bout-related MVPA minutes per week 3 ) preoperatively. [7] [8] [9] [10] Furthermore, patients demonstrate only small bout-related MVPA changes post-operatively, thereby continuing their inactive lifestyle. [8] [9] [10] Prospective research shows that higher MVPA preoperatively predicts higher MVPA and improved BS outcomes postoperatively, [9] [10] [11] [12] providing rationale for preoperative PA interventions (PAI). We recently reported findings from the Bari-Active trial, 13 which tested a 6-week PAI vs standard pre-surgical care control (SC) on objectively-measured pre-to post-intervention changes in bout-related MVPA. At post-intervention, PAI (n = 40) on average achieved a near fivefold increase in bout-related MVPA (4.4-21.0 min per day), whereas SC (n = 35) showed no change (7.9-7.6 min per day; PAI vs SC, P = 0.001). Similarly, daily steps increased by an average of 2028 (4908-6935) in PAI compared with only 203 (4629-4832) in SC. Although findings show that patients can achieve marked PA increases preoperatively, it is important to determine whether these higher PA levels are maintained post-operatively.
INTRODUCTION
The current study compared changes in bout-related MVPA and steps across pre-(baseline, post-intervention) and post-operative (6-month post-operative follow up) time points in a sub-sample of Bari-Active trial participants who underwent BS. We hypothesized PAI would demonstrate greater increases in bout-related MVPA and steps across time and higher levels of these types of activity at post-intervention and 6-month post-operative follow up vs SC.
MATERIALS AND METHODS

Participants
Thirty-six participants were both randomized to PAI or SC and underwent BS. Initial eligibility criteria included: aged 18-70 years, body mass index (BMI) ⩾ 35 kg/m 2 , and inactive but able to walk ⩾ 2 blocks (~161 meters) unassisted. Individuals were ineligible if scheduled for BS o10 weeks during screening, participating in another PA/weight loss program, intending to relocate geographically, or had issues (for example, relocation, substance abuse/ severe psychiatric condition, language barriers) that could interfere with protocol adherence.
Participants
Design/Procedures BS-seeking individuals were referred by surgical clinics in Rhode Island, USA between April 2010 and January 2014. During a clinic visit, patients received a study flyer. Those who expressed desire to participate and received surgeon approval to perform walking exercise underwent telephone screening. Eligible patients were invited to an orientation/baseline session where they provided informed consent, had height and weight measured, and were given a SenseWear armband (SWA) monitor to wear for the next 7 days. Participants were then randomly assigned 1:1 to 6 weeks of PAI or SC using a computer-generated random-permuted blocking procedure. Participants wore the activity monitor again at post-intervention and post-operative follow up. Participants received $100 for completing all assessments. The Miriam Hospital IRB approved study procedures (clinicaltrials.gov registration NCT00962325).
Interventions
PAI. Beginning 1 week after baseline and completion of 7 days of activity monitoring, participants received 6 consecutive weekly individual face-to-face counseling sessions, weekly PA monitoring/ planning logs, and a pedometer to increase bout-related, moderate-intensity walking by 30 min/day and steps by 5000 per day. Participants recorded bout-related walking minutes and steps at the end of each day. During week 1, participants maintained usual PA patterns to determine baseline values and tailored weekly goal progression. For week 2, 10 additional boutrelated walking minutes per day and 1000 steps per day above baseline were prescribed. For each subsequent week, 5 daily boutrelated walking minutes and 1000 daily steps were added to the previous week's prescription.
Interventions
Counseling sessions were conducted by the primary author and focused on: reviewing self-monitoring records and progress towards goals, problem-solving barriers, teaching behavior change strategies, and developing action plans to achieve goals (see Bond et al. 13 for a detailed description). At post-operative follow up, participants only received additional monitoring/ planning logs and a copy of the behavioral contract (including post-operative PA goals) created during the final intervention week prior to 7 days of PA monitoring.
Interventions
Standard care control. Like PAI, SC participants attended scheduled clinical visits to receive standard surgical care. They were advised to begin exercising, but received no PA prescription involving specific activities, performance requirements or strategies to adopt this behavior.
Measures
Objectively-measured PA. The SWA monitor (BodyMedia, Inc., Pittsburgh, PA, USA) measured changes in MVPA minutes per day and steps per day. The SWA integrates data from a tri-axial accelerometer and physiologic sensors to estimate energy expenditure (EE) and intensity of activities. The SWA demonstrates acceptable agreement with criterion EE measures and provides MVPA estimates comparable to other objective monitors. [14] [15] [16] Participants received instructions to wear the SWA during waking hours for 7 consecutive days at all assessments. The SenseWear Professional Software (Version 7.0) calculated wear time. Metabolic equivalent (MET) values determined daily minutes spent in boutrelated MVPA (⩾ 3 METs). Allowance of ⩾ 1 min o3 METs was employed in calculating bout-related MVPA (that is, accumulated in bouts ⩾ 10-min). Monitor wear time of ⩾ 6 h/day on ⩾ 4 days for all assessments was required for inclusion in analysis. 13 We have previously shown that this criterion maximizes sample size/data inclusion while providing estimates of bout-related MVPA that are similar to those when more stringent wear time criteria are employed. 13 Other measures. Demographics information (that is, age, sex, race/ethnicity and education) was collected via timothy49@example.net. Weight was measured at each of the assessment points.
Statistical analysis
Analyses were performed using SPSS Statistics for Windows (version 20.0; SPSS, IBM Corp, Armonk, NY, USA). Means and s.d. and frequency counts were calculated to describe participant characteristics. Repeated-measures analysis of variance (ANOVA) compared PAI vs SC on PA across assessments. Planned comparisons of PAI vs SC on MVPA (bout-related) and steps at post-intervention and post-operative follow up were conducted using independent t-tests. Corrected P values were used when variances were not equal. The intent-to-treat (ITT) principle in which missing data at post-intervention follow up were substituted with baseline values (assuming no change) was followed. Cohen's d was calculated to determine effect size between group means at specific assessment points. Significance tests were twotailed, α = .05. This study involves a secondary analysis of postoperative follow up changes collected as part of a randomized controlled trial powered to detect a difference of 11 bout-related MVPA minutes per day in PAI vs SC at post-intervention with n = 75.
RESULTS

Recruitment/retention
Recruitment/retention data have been reported previously. 13 Of 293 patients screened by telephone, 213 were excluded. Eighty Table 1 . Baseline characteristics of participants who were randomized to preoperative physical activity intervention (PAI) or standard surgical care control (SC) and underwent bariatric surgery Average time from post-intervention to surgery and from surgery to post-operative follow up was 84.3 ± 70.9 and 201.3 ± 61.0 days, respectively. Regarding BS procedures, 18 (50%) participants underwent Roux-en-Y gastric bypass, 16 (44%) gastric banding, and 2 (6%) gastric sleeve. Percent weight loss averaged 25.9 ± 9.8% among the 32 (88.9%) participants for whom post-operative weights were available, and did not significantly differ by condition (PAI: 24.5 ± 8.5% vs SC: 30.1 ± 10.7%, P = 0.139). Figures 1a and b shows changes in daily bout MVPA minutes and steps. PAI vs SC had greater increases across the study period in bout-related MVPA minutes/day and steps/day. PAI differed from SC on bout-related MVPA at post-intervention (P = 0.016; d = 0.91), but not follow up (P = 0.15; d = 0.47), and steps at postintervention (corrected P = 0.031; d = 0.78) and follow up (P = 0.024; d = 0.84).
Changes in PA

DISCUSSION
This study is the first to examine whether intervention-related increases in objectively-measured PA preoperatively can be maintained post-operatively. PAI achieved significantly greater increases in preoperative bout-related MVPA and steps from baseline to post-intervention vs SC, which were maintained at 6-month post-operative follow up. These findings correspond with observational research showing positive correlations between pre-and post-operative PA 9-10 and provide support for behavioral strategies aimed at increasing preoperative PA. Interestingly, SC increased bout-related MVPA but not overall ambulatory movement (that is, steps) from post-intervention to post-operative follow-up, whereas PAI maintained postintervention levels of both types of activity. Consequently, the effect size for the group difference decreased from large to medium for bout-related MVPA and remained large for steps. This suggests that SC increased time spent exercising post-operatively but compensated with less overall movement, whereas PAI maintained a high exercise level and also moved more vs SC.
DISCUSSION
While PAI were successful in maintaining levels of bout-related MVPA (~200 min per week) that were markedly higher than baseline (~30 min per week), similar to post-intervention (~184 min per week), and above public health guidelines (⩾150 bout-related MVPA minutes per week 2 ), even greater amounts may be necessary to enhance weight loss and limit subsequent weight regain after BS. 17, 18 Thus, prescription of higher PA goals may be required. 19 Nonetheless, recent data suggest that the volume of bout-related MVPA performed by PAI can yield clinically-relevant improvements in metabolic health parameters post operatively. 17, 20 This study has limitations. Less than half (48%) of participants initially randomized underwent BS, limiting sample size. However, investigators had no influence over participants' BS decisionmaking process. Interestingly, 55% of PAI vs 40% of SC had BS: while not statistically significant (P = 0.107), this difference warrants additional research to determine whether preoperative interventions contribute to higher BS frequency, possibly through enhanced sense of preparation, motivation, and confidence in ability to adhere to post-operative behavioral recommendations. The small sample, variability in surgical procedures, and differences in number of participants between groups limited ability to test differences in weight loss between conditions. It is unclear whether intervention-related preoperative PA increases can be maintained or enhanced beyond 6-months post-operatively.
DISCUSSION
In summary, this study shows that BS patients can not only achieve marked increases in PA preoperatively with behavioral intervention, but can sustain these higher PA levels postoperatively. Preoperative PA intervention studies designed and sufficiently powered to test efficacy for enhancing and maintaining BS-related weight, metabolic, and quality of life outcomes are needed.

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