Evaluating the Acute Glycemic Response to Different Strategies of Breaking Up Sedentary Time
Condition: Pre Diabetes; Postprandial Hyperglycemia
MeSH terms: Hyperglycemia; Prediabetic State
Study type: Interventional

Summary: 
      This study aims to determine the most effective strategy of reducing sedentary behavior to
      improve health. Specifically, we aim to answer the following questions: (a) To determine if
      there is a significant difference in acute post-prandial glucose response between continuous
      sitting and two intermittent standing regimes (high frequency, low duration breaks (HFLD) and
      low frequency, high duration breaks (LFHD)). We hypothesize that intermittent standing
      (combined HFLD breaks and LFHD breaks regimes) will result in lower overall acute
      post-prandial glucose compared to continuous sitting. (b) To determine if there is a
      significant difference in acute post-prandial glucose response between two strategies to
      reduce sitting with standing (HFLD standing breaks vs. LFHD standing breaks). We hypothesize
      that the HFLD breaks condition will elicit lower acute post-prandial glucose level compared
      to the LFHD breaks condition. All eligible participants will be consented and subjected to
      all three study conditions: (i) Uninterrupted sitting, (ii) HFLD breaks, and (iii) LFHD
      breaks. The order at which participants were subjected to these conditions will be randomly
      determined and each condition were performed a week apart. Standardized meals (breakfast and
      lunch) will be provided during each lab visit and participants will be then be asked to
      perform their usual work activity using a sit-stand workstation in the lab. Depending on
      their assigned condition, the participants will be prompted to stand or sit for a given
      period of time. A continuous glucose monitor will be used to measure glucose response to the
      intervention while an activPAL device will be used to make sure that participants are
      compliant with the study protocol.
    

Detailed description: 
      Most studies that explored the health benefits of interrupting sitting time focused on using
      different modalities (i.e., comparing walking vs standing breaks). However, experimental
      studies that directly compare patterns of interrupting sitting time through standing only are
      needed to advance the field. This study aimed to (i) determine if there is a difference in
      glucose response between continuous sitting (CS) and two intermittent standing regimes (high
      frequency, low duration breaks (HFLD) and low frequency, high duration breaks (LFHD)) and
      (ii) to determine if there is a difference in glucose response between the two strategies
      (HFLD vs. LFHD).

      A. Study Participants and Recruitment The target participants were sedentary office employees
      with impaired fasting glucose level. Participants were recruited through a study flyer via
      various recruitment channels (i.e., ASU faculty website, social media, word of mouth). The
      study flyer contains a link to a Qualtrics survey to pre-screen interested participants. All
      eligible participants will be scheduled for a 30-minute screening visit to assess fasting
      glucose level. A total of 12 sedentary and inactive employees (indicated by >6 hrs of
      workplace sedentary time assessed by the activPAL device during a one-week screening period)
      will be enrolled to participate in a fully randomized crossover trial.

      B. Study Design The study design is a crossover randomized trial with three conditions: (i)
      uninterrupted sitting, (ii) high-frequency and low duration (HFLD) standing breaks, and (iii)
      low-frequency and high duration (LFHD) standing breaks. In the interrupted sitting conditions
      (i.e., HFLD and LFHD), total sitting and standing time were designed to be equal in both
      groups. The only difference between the two conditions was on the pattern to accumulate
      sitting time. A common threshold for prolonged sitting time in epidemiological studies of
      sedentary behavior is 30 minutes of continuous sitting. In the HFLD condition, we will use
      half of this threshold and ask participants to interrupt their sitting time every 15 minutes
      using a 2.5-minute standing break. In contrast, participants will perform twice this
      threshold in the LFHD standing breaks where they will complete a 10-minute standing break
      every hour of sitting.

      All possible sequence of condition were determined and organized into blocks (a total of six
      blocks). Each eligible participant will be randomly assigned to a block to determine the
      sequence that they would perform the conditions. The randomization process will involve a
      separate research staff preparing 40 sealed envelope that contains a block number randomly
      determined using a computer-generated random sequence. These envelopes will be kept in a
      secure cabinet by another research staff not directly involved in the project. Each
      participant will be blinded to the condition that they are going to perform during the visit
      until after their first standardized meal.

      Participants will be invited to three 450-minute (7.5-hour) laboratory visits where they will
      be provided with a private room, a sit-stand workstation, and a desktop computer. During each
      laboratory visit, participants will perform their usual desk-based work activities. All
      visits will be scheduled one week apart. Participants will be instructed to fast overnight,
      and standardized breakfast and lunch meals will also be provided to control for any dietary
      effects on glucose level. In addition, each participant will be instructed to avoid any
      moderate-vigorous physical activities for at least two days and smoking cigarettes and
      consuming alcoholic beverages at least three days prior to each visit. Upon arrival to the
      lab for their first visit, participants will complete a dietary log of their last meal the
      previous day. They will then be instructed to replicate this meal the night prior to each
      visit.

      C. Outcome Measures Continuous Glucose Monitors. A day prior to the first visit, participants
      will be fitted with a Freestyle Libre Pro (Abbott Laboratories, Chicago, IL) continuous
      glucose monitor by a trained researcher. The sensor will be attached to the back part of the
      participant's non-dominant arm and programmed to measure interstitial glucose at 15-minute
      intervals. The device is designed to be worn continuously for 14 days and is waterproof,
      lightweight (roughly the size of a quarter) and minimally obtrusive. The sensors will be
      attached using proper aseptic procedures and in accordance with the manufacturer's
      instructions. Lastly, each participant will be given instructions on how to care for the
      device.

      At the end of the last visit, data from each sensor will be acquired using the Libre Pro
      reader and uploaded to an online patient repository (LibreView). Data will then be processed,
      and 15-minute epoch data will be downloaded into a local secure drive for further processing.
      Continuous glucose data corresponding to each visit date and time will be isolated using the
      paper logs and inspected for completeness and quality of data. Files with less than 80% of
      valid observation will be excluded from the succeeding analyses. Glucose incremental area
      under the curve (iAUC) will be calculated using the trapezoidal method along with other
      metrics for variability (i.e., MAGE: mean amplitude of glycemic excursions).

      activPAL Device. Objective measures of sitting, standing and moving time will derived from
      the activPAL micro accelerometer worn on the midline of the right thigh. Participants will
      wear the device on two occasions: (i) for 7 consecutive days during the baseline period and
      (ii) for 14 consecutive days during the study. The validity and reliability of the activPAL
      in measuring sedentary and physical activity behaviors has been previously reported.
      Collected data will be processed into events of sitting, standing, or moving (i.e., stepping)
      using the activPAL software version 7.2.32 (PAL Technologies Ltd, Scotland, UK).

      Standard Meals. Standardized meals (breakfast and lunch) will be provided in each lab visit
      to control for any dietary influence. Each meal are designed to provide 33% of the
      participant's total daily caloric needs following a typical American diet (50-60%
      carbohydrates, 25-35% fat, and 10-20% protein). Basal metabolic rate will be calculated for
      each particiapnt using Schofield's equation using a 1.5 activity factor. After calculating
      the required caloric content of each meal, a meal with the closest caloric value will be
      chosen from a list of pre-determined meal plan. A typical breakfast will be composed of a
      croissant, ham, cheddar cheese, cereals with milk, fruit cup, and orange juice while lunch
      items consisted of a ciabatta ham and cheese sandwich and orange juice. The same meal will be
      provided during all follow-up visits.
    

Intervention name(s): CS: Continuous sitting; HFLD: HIgh frequency, low duration standing breaks; LFHD: Low frequency, high duration standing breaks
Intervention type(s): Behavioral; Behavioral; Behavioral
Intervention description(s): Participants were asked to sit continuously throughout the duration of the lab visit.; Participants were asked to interrupt their sitting time every 15 minutes using 2.5-minute standing breaks.; Participants were asked to interrupt their sitting time every 60 minutes using 10-minute standing breaks.
Intervention MeSH terms: Oxymetazoline
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: The study design is a crossover randomized trial with three conditions: (i) uninterrupted sitting, (ii) high-frequency and low duration (HFLD) standing breaks, and (iii) low-frequency and high duration (LFHD) standing breaks. We utilized a balanced and uniform with 6 randomization blocks (ABC, ACB, BAC,BCA, CAB, CBA) design.
Masking: Single (Participant)
Primary purpose: Prevention
Keywords: Interrupting sitting; Continuous glucose monitroing; Pattern of sitting breaks