Does frequency or duration of standing breaks drive changes in glycemic response? A randomized crossover trial.

Intervention strategies to break up sitting have mostly focused on the modality (i.e., comparing different intensities and/or type of activities) and less on how frequency and duration of breaks affect health outcomes. This study compared the efficacy of different strategies to break up sitting time [i.e., high frequency, low duration standing breaks (HFLD) and low frequency, high duration standing breaks (LFHD)] in reducing postprandial glucose. Eleven sedentary and prediabetic adults (mean ± SD age = 46.8 ± 10.6 years; 73% female) participated in a cross-over trial. There were six blocks that represented all potential combinations (ordering) of the study conditions and participants were randomly assigned to a block. Each participant underwent three 7.5-h laboratory visits (1 week apart) where they engaged in either continuous sitting, HFLD, or LFHD condition while performing their usual office-related tasks. Standardized breakfast and lunch meals were provided. Postprandial mean glucose, area under the curve (AUC), and incremental area under the curve (iAUC) were evaluated using mixed models. Compared with LFHD condition, the HFLD standing breaks condition significantly lowered mean glucose by -9.94 (-14.13, -5.74) mg/dL·h after lunch, and by -6.23 (-9.93, -2.52) mg/dL·h, for the total lab visit time. Overall, the results favor frequently interrupting sitting with standing breaks to improve glycemic control in individuals with prediabetes. Further studies are needed with larger sample sizes to confirm the results.

Daily sampling frequency and sampling duration affect reliability of person-level estimates of physical activity outcomes: Optimizing Ecological Momentary Assessment studies of physical activities.

Studies on the interrelationship between physical activity (PA) behaviors and EMA-assessed constructs should use measures with high reliability of both the EMA-assessed constructs and the time-matched accelerometry-assessed PA behavior. The aim of this paper is to evaluate how the reliability of accelerometry-assessed PA outcomes is affected by different EMA sampling schemes. Emulating relevant sampling schemes in EMA studies, multiple random samples of real-world accelerometer data (measured via activPAL worn for ∼7 days) were drawn that varied in the number of daily samples (3, 5, and 7 daily samples) and in the duration of each sample (5 min, 60 min, and 120 min), totaling 9 sampling schemes. The reliability of the resulting PA outcomes was estimated by correlating weekly aggregates of the sampled data with the true parameter values (weekly aggregates of all data). A total of 4231 days were analyzed from 619 participants (mean age 45 ± 16 years; 73.3 % female; 72.7 % Non-Hispanic White). At the lowest sampling duration (5 min), none of the sampling schemes reached the threshold for acceptable reliability (reliabilities ranged from 0.20 to 0.67). Using 120 min sample duration resulted in reliable person-level PA estimates (ranges 0.77 to 0.97) except for the time spent in sedentary behavior (rel = 0.68), and for minimum (rel = 0.66), and maximum (rel = 0.63) PA intensity. These three PA outcomes consistently yielded lower levels of reliability across all sampling schemes. Holding constant the total time covered in a day, sampling schemes that used more frequent samples with shorter duration resulted in greater reliability compared to sampling schemes that used less frequent samples with longer duration. Overall, the results are consistent with sampling theory - reliability increased as more time was covered. However, our results also suggested interactive effects of reliability based on sampling frequency, duration, and PA outcome. Researchers should be aware that the reliability of accelerometer-derived PA outcomes can vary depending on the sampling design of EMA studies.

Stand and Move at Work sedentary behavior questionnaire: validity and sensitivity to change.

PURPOSE: We evaluated the validity and sensitivity to change of a workplace questionnaire to assess sedentary behavior (SB) during and outside work. METHODS: Participants wore an activPAL and completed an SB questionnaire at two time points (baseline and 3-month follow-up). Ecological momentary assessments were used to assess workplace location (at desk vs. away from desk). Intraclass correlation coefficients, mean difference, root of mean square error, kappa agreement, and Bland-Altman plots assessed validity. Sensitivity to change after 3 months of intervention was assessed using the standardized effect size. RESULTS: Data from 546 participants (age = 45.1 ± 16.4 years, 24.9% males, 72.7% white) were analyzed. Intraclass correlation coefficients ranged from 0.08 to 0.23. SB was overestimated d¯(95%CI)[] by 47.9 (39.2, 56.6) min during work hours but underestimated for both non-work hours and nonworkdays by -38.3 (-47.4, 29.1) and -106.7 (124.0, -89.5) min, respectively. Participants slightly underestimated SB by -3.4 (-12.6, 5.7)% when at their desk but overestimated SB by 2.8 (-2.4, 8.0)% when not at their desk. The questionnaire demonstrated similar standardized effect size (>0.6) to the activPAL for sedentary and standing time. CONCLUSIONS: Agreement between the questionnaire and activPAL was on par with other self-report measures. The questionnaire yielded valid estimates of at/away from desk SB and was sensitive to change.

Enrollment Strategies, Barriers to Participation, and Reach of a Workplace Intervention Targeting Sedentary Behavior.

PURPOSE: To review enrollment strategies, participation barriers, and program reach of a large, 2-year workplace intervention targeting sedentary behavior. APPROACH: Cross-sectional, retrospective review. SETTING: Twenty-four worksites balanced across academic, industry, and government sectors in Minneapolis/Saint Paul (Minnesota) and Phoenix (Arizona) regions. PARTICIPANTS: Full-time (≥30+ h/wk), sedentary office workers. METHODS: Reach was calculated as the proportion of eligible employees who enrolled in the intervention ([N enrolled/(proportion of eligible employees × N total employees)] × 100). Mean (1 standard deviation) and median worksite sizes were calculated at each enrollment step. Participation barriers and modifications were recorded by the research team. A survey was sent to a subset of nonparticipants (N = 57), and thematic analyses were conducted to examine reasons for nonparticipation, positive impacts, and negative experiences. RESULTS: Employer reach was 65% (56 worksites invited to participate; 66% eligible of 56 responses; 24 enrolled). Employee reach was 58% (1317 invited to participate, 83% eligible of 906 responses; 632 enrolled). Postrandomization, on average, 59% (15%) of the worksites participated. Eighteen modifications were developed to overcome participant-, context-, and research-related participation barriers. CONCLUSION: A high proportion of worksites and employees approached to participate in a sedentary behavior reduction intervention engaged in the study. Interventions that provide flexible enrollment, graded participant engagement options, and adopt a participant-centered approach may facilitate workplace intervention success.

Using Point-of-Choice Prompts to Reduce Sedentary Behavior in Sit-Stand Workstation Users.

Introduction: Desk-based office workers are at occupational risk for poor health outcomes from excessive time spent sitting. Sit-stand workstations are used to mitigate sitting, but lack of workstation usage has been observed. Point-of-choice (PoC) prompts offer a complementary strategy for office workers to break up their sitting time. Study purpose: The purpose of this study was to examine the preliminary efficacy, preference, and acceptability of a theory-driven (i.e., 40 unique prompts encompassing social cognitive theory; TD-PoC) and an atheoretical basic reminder PoC prompt intervention (R-PoC) on reducing sedentary behavior in office workers with self-reported low sit-stand workstation usage (≤4 h per day). Methods: In a cross-over design, participants (N = 19, 78.9% female, 39.4 ± 10.7 years of age) completed a 5-days no-prompt control condition followed by a random and counterbalanced assignment to one of the TD-PoC and R-PoC active conditions with a 1-week washout period between. Preliminary efficacy was assessed during work hours with the activPAL micro accelerometer. Preference was assessed prior to each active condition and acceptability was assessed following each active condition via questionnaire. Results: The R-PoC prompt condition significantly decreased sitting time (b[se] = -49.0 [20.8], p = 0.03) and increased standing time (b[se] = 49.8 [19.7], p = 0.02) and displayed a significant increase in sit-stand transitions (b[se] = 2.3 [1.1], p = 0.04), relative to no-prompt control. Both the R-PoC and TD-PoC prompt conditions significantly decreased time spent in prolonged sitting bouts at b[se] = -68.1 [27.8], (p = 0.02), (b[se] = -76.7 [27.1], p = 0.008) relative to no-prompt control. Overall, the TD-PoC prompt condition displayed higher preference and acceptability ratings; however, these differences were not significant (p's > 0.05). Conclusion: While the R-PoC prompt condition was slightly more efficacious than the TD-PoC prompt condition, the TD-PoC prompt condition was rated with higher preference and acceptability scores. Large variations between participants in preference, acceptability, and intervention feedback may indicate need for tailored messaging which may facilitate sustained use in the long-term.