There was no significant difference between the arms in steps per day or minutes of moderate/vigorous physical activity per week at baseline. We found an increase in physical activity in both arms as measured by accelerometer and blinded pedometer. The difference between arms was not significant for accelerometer measured physical activity (p = 0.34) and was marginally not significant for steps (p = 0.07). Discussion Our pilot intervention yielded a significant increase in physical activity as measured by two different objective measures- accelerometer and blinded pedometer. Despite participants failing to achieve the stated step count intervention target at follow-up for either dose arm, participants did meet the intervention time-based target dose in both arms. While the high (60 min/day) dose arm had a target daily physical activity level that was twice current physical activity recommendation, the higher dose arm did not achieve a significantly higher level of physical activity than the standard (30 min/day) dose arm. Despite walking being the most commonly reported physical activity [39,40], measuring walking presents numerous challenges, including biased recall of occurrences, speed, and/or intensity [41–43]. Thus, objective measurement tools that can detect gradations in walking behavior are useful physical activity measures. The step counts recorded by our population (mean 4549/day at baseline) were comparable to previous reports of sedentary populations [26,27]. Pedometers are effective physical activity promotion tools as they can provide immediate feedback in the form of step counts, thereby facilitating individual-level behavior modification [44–47]. For example, a study by Croteau found that a minimal contact, self-managed, pedometer-based intervention resulted in a signif- icant increase in the average daily steps of participants from 8565 (+/23121) to 10538 (+/23681) at follow-up in 37 men and women, a change of 1973 steps [45]. The impact of our intervention was similar, though we noted that the change was larger among those given a larger intervention target dose. Despite not achieving the intervention step count target, both arms recorded more than 150 minutes of moderate/vigorous physical activity per week on the accelerometer at follow-up and exceeded the intervention target dose for duration. This may suggest that pedometer wear time was not complete during the assessment periods, as the accelerometer physical activity estimates employ an algorithm that accounts for daily wear time, or that the pedometers underestimated the step count [48]. Our study was also subject to other limitations, including our small sample size. While the small sample size was part of the pilot study process, it may have reduced our ability to detect differences in the intervention arms. Our response rate provides useful information for planning recruitment to physical activity promotion programs in popula- tions at increased risk for colon cancer. The response rate was similar to other ‘‘cold contact’’ approaches to health behavior References 1. International Agency for Research on Cancer, World Health Organization (2002) IARC Handbooks of Cancer Prevention: Weight Control and Physical Activity, Volume 6. Lyon, France: International Agency for Research on Cancer. 2. World Cancer Research Fund/American Institute for Cancer Research (2007) Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective. Washington DC: AICR. 3. Wolin KY, Yan Y, Colditz GA, Lee IM (2009) Physical activity and colon cancer prevention: a meta-analysis. Br. J. Cancer 100: 611–616. Author Contributions Conceived and designed the experiments: KW. Performed the experi- ments: KW CF DE. Analyzed the data: KW. Wrote the paper: KW CF AJ DE. 4. Wolin KY, Yan Y, Colditz GA (2011) Physical activity and risk of colon adenoma: a meta-analysis. Br. J. Cancer 104: 882–885. doi:10.1038/ sj.bjc.6606045. 5. Wei EK, Giovannucci E, Wu K, Rosner B, Fuchs CS, et al. (2004) Comparison of risk factors for colon and rectal cancer. Int. J. Cancer 108: 433–442. 6. Haskell WL, Lee I-M, Pate RR, Powell KE, Blair SN, et al. (2007) Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc 39: 1423–1434. doi:10.1249/mss.0b013e3180616b27. PLoS ONE | www.plosone.org 4 July 2012 | Volume 7 | Issue 7 | e39719 Physical Activity in Patients with Colon Adenomas research [49]. The study also has several strengths including our reliance on an evidence-based intervention and objective assess- ment of physical activity change. This pilot intervention provided important information that can be used in larger trials. This 12 week physical activity intervention of minimal supervision can result in significant increases in physical activity, sufficient to meet the US Physical Activity Guidelines [7]. While pedometers are useful tools for self- monitoring and physical activity promotion, their display interface may induce reactivity such that they may not accurately reflect changes in behavior during an intervention. We attempted to minimize this by blinding the pedometer used for assessment purposes, but participants also wore their intervention pedometer at follow-up. Importantly, despite initial concerns that a target of 60 minutes/day would be too aggressive or difficult for this largely sedentary population to achieve, both study arms increased physical activity by more than twice the intervention recommen- dation at follow-up. Some of this time likely reflects usual daily activity, given the physical activity level recorded at baseline, but the increase from baseline to follow-up was significant. Our pilot study indicates that a minimal contact intervention can generate significant changes in physical activity among individuals at elevated risk for colon cancer. However, a more contact-intensive intervention may be necessary to achieve the target intervention dose and this should be evaluated in future studies. Furthermore, because the study did not achieve the target dose, the potential impact of the intervention on colon cancer risk is not clear. Future studies should also evaluate whether this minimal contact intervention results in changes in endpoints more closely tied to colon cancer risk. Supporting Information Table S1 Step Down Colon Cancer Pilot Participants’ Baseline Characteristics. (DOCX) Table S2 Step Down Colon Cancer Pilot Objective Physical Activity. (DOCX) Step Down Colon Cancer CON- Consort Diagram S1 SORT Diagram. (DOCX) Checklist S1 (DOC) Protocol S1 (DOCX) CONSORT 2010 Checklist. Trial Protocol.