Optimal Reduction in SB to Reduce Glycemic Variability

2020-04-01 04:26:52 | BioPortfolio


Rationale: Older adults spend the majority of their time in sedentary behaviours (SB). High amounts of SB have been correlated with reduced cognitive performance. Long periods of time spent sitting results in excessive glycemic variability, potentially contributing to cognitive decline. Reducing/replacing SB with short intermittent bouts of light physical activity have shown positive effects on glycemic variability. Thus, interrupting prolonged sitting with bouts of light physical activity may regulate blood glucose and thus mitigate cognitive decline.

Purpose: This study intends to investigate the appropriate interval frequency of post-prandial SB reduction, by light physical activity needed to optimize total and incremental area under the curve for glucose response in overweight older adults at risk for glucose intolerance with mild cognitive impairment in both lab and free-living environments. Second, this study aims to investigate the acute impact of reducing SB on glycemic variability and its relationship with cognition.

Hypothesis: First, there will be a dose-dependent response of more frequent interruptions of SB (more frequent intervals of light physical activity) with better glycemic control. Second, reducing SB will result in less glycemic variability, which will translate into better levels of cognitive performance.

Methods: Generalized linear mixed models with random intercepts will be used to evaluate the differential effects of the experimental conditions on the selected outcomes.


This study will be a randomized crossover trial and reported in accordance with CONSORT guidelines. The study will involve a total of three seven-day conditions (2 experimental and 1 control) with a three-week washout period in-between to minimize practice effects for a total intervention period of nine weeks (see figure 1). Each condition will consist of one day supervised in the laboratory followed by six at-home days, following lab protocol as closely as possible.

Participants will be referred to the study by their physician. Interested participants will be asked to contact the researcher by email or phone call. A phone interview will be used to verbally explain the study protocol and screen for eligibility. The interview will consist of: 1) Age, height, weight; 2) Smoking status; 3) GDS assessment- short form (Yesavage et al., 1983); 4) PA and SB patterns using a modified version of the Physical Activity Scale for the Elderly (PASE) (Washburn, Mcauley, Katula, Mihalko, & Boileau, 1999); 6) Medication use; 7) Alcohol consumption; and lastly 8) Orthopedic concerns or injuries/illness that may limit participation. If participants pass the telephone screening, they will be invited to a local LifeLabs Centre for a fasted blood test (overnight fast ≥10 h) and an oral glucose tolerance test (OGTT).

Once these tests are completed, results will be interpreted for: 1) Fasted blood glucose levels in order to rule out diagnosis of diabetes as well as 2) HbA1C levels, which are the best indicator of blood glucose levels over the course of two to three months (Sherwani, Khan, Ekhzaimy, Masood, & Sakharkar, 2016). OGTT measures the body's ability to use glucose (a type of sugar), that is the body's main source of energy. This test can be used to diagnose prediabetes and diabetes. For the purpose of this study it will be used to indicate glucose intolerant individuals (as per inclusion criteria).

If participants are still deemed eligible after the telephone screening and LifeLab Centre results, they will be invited into the lab for a familiarization session. They will be instructed to avoid caffeine, alcohol and MVPA for 48 hours prior to this session. During this session the following information will be obtained;

- Written informed consent

- Height using a stadiometer and weight using a standard beam scale

- Demographics questionnaire (education, ethnicity, family background, comorbidities)

- Physical Activity Readiness Questionnaire (PARQ+) (Bredin, Gledhill, Jamnik, & Warburton, 2013)

- Resting blood pressure- will be measured once on each arm and then twice on the left arm with an automated BP monitor

- VO2 testing (see protocol for VO2 section) The participants will be educated/familiarized on the following;

- Cognitive assessments - Cambridge Neuropsychological Test Automated Battery (CANTAB)

- Fitting with an inclinometer (activPAL4) (see ActivPal protocol section)

- Fitbit provision (see Fitbit protocol section)

- Meal plan

Participants will be visited at their home ~72hrs prior to each condition to be fitted with the CGM, ActivPal and FitBit. They will also be instructed to avoid caffeine, alcohol and MVPA for 48 hours prior to each of the three conditions. Participants will be asked to only consume the food described in the meal-plan provided for the 48 hours before the first laboratory visit. They will be asked to replicate their diet (quantity and timings) prior to each subsequent visit. Dinner will be consumed between 7:00 and 9:00 pm, allowing for a 10 hour fast prior to the experimental condition the next morning. All participants will be instructed to arrive at the laboratory (with minimal activity during commute) at approximately 7:00 am. Upon arrival, participants will be asked to use the washroom and then rest for 30 minutes preceding a blood pressure measurement and first cognitive assessment. The participants will undergo the CANTAB cognitive assessments (at ~7:30 am) before meal consumption. A standardized breakfast meal will be consumed at 8:00 am, followed by lunch at 12:00 pm and dinner at 5:00 pm. Participants will be allotted 20 minutes for full meal consumption. The CANTAB cognitive assessments will then be re-administered at approximately 8:00 pm. Participants will be supervised throughout the conditions to ensure adherence to the protocols and will be permitted to watch DVDs, read books, magazines, newspapers, talk and/or work on a laptop computer. However, what they do during the first condition will be documented and then replicated for the remaining experimental conditions. Intensity of the bout intervals will be monitored with a heart rate monitor (Polar HR) and kept to 40% of their VO2max along with an RPE of 6-9 using the Borg RPE scale (Borg, 1954). The participants will be wearing their Fitbit wristwatches and will be asked to take note of the feeling and heart rate reading in order to duplicate the intensity of bouts during the at-home portion. The intervention conditions are depicted in figure 2. One of the conditions being a control, while the remaining two being interventions that are equal in total duration of sedentary time and light physical activity.

Trial conditions were as follows:

1. Condition A (CON): This will be the control condition. It will consist of uninterrupted sitting from 8 am until 7 pm, only rising from the chair to void.

2. Condition B (LONG): will consist of completing one 10-minute bout of light intensity walking (RPE 6-9 and 40% VO2max) 30 minutes post-prandial. Participants will rise from their seated position to walk ~10 metres to a treadmill to perform this bout. The participant will repeat this after lunch and dinner, for an accumulated total of 30 minutes of light walking.

3. Condition two (SHORT): will consist of interrupting sitting with four 2.5-minute bouts of light walking at 30 minutes, 60 minutes, 90 minutes and 120 minutes post-prandial. Participants will rise from their seated position to walk ~10 metres to a treadmill to perform these bouts. The participant will repeat this after breakfast, lunch and dinner for an accumulated total of 30 minutes of light walking.

Once the 12- hour laboratory component is complete, participants will be sent home (still wearing the CGM, activPAL and Fitbit) with the intension of replicating the laboratory-based protocol after each meal in their own free-living environment. Participants will track their mealtimes by sending photos to the researcher before consumption during the 6 at home days. The researcher will then go to the participants house on the last day (day 7) of each condition to re-administer the CANTAB cognitive assessments and collect the CGM, activPal and FitBit. There will then be a 3-week washout period, followed by replication of protocol for the remaining two conditions.

Study Design


Sedentary Behavior


interrupting sedentary behaviour with light physical activity


The University of Western Ontario


Not yet recruiting


Western University, Canada

Results (where available)

View Results


Published on BioPortfolio: 2020-04-01T04:26:52-0400

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