Breaking-up Sedentary Time and 2 Weeks Detraining
Condition: Old Age
Study type: Interventional

Summary: 
      Regularly interrupting sedentary behavior (SB) with activity breaks may attenuate
      postprandial glucose (PPG) excursions and improve glycemic control. The investigators aimed
      to determine the effect of interrupting 7 hours of prolonged sitting with brief bouts of
      moderate physical activity (PA) (alternating between up/down stairs and sit/stand up from the
      chair) on postprandial glucose (PPG) responses in comparison with uninterrupted sitting. In
      addition, the investigators aimed to examine the effects of 2 weeks of detraining (DT) on PPG
      on both protocols. Non-diabetic, trained older adults (n = 15) will be recruited for a
      randomized crossover trial with two treatments performed in two different training
      conditions: 1) uninterrupted sitting protocol (CON); 2) seated with 2-minutes bouts of
      moderate PA every 30 minutes (INT). Both protocols will be performed in a trained condition
      and after 2 weeks of DT. In the early morning of each trial, participants will do an oral
      glucose tolerance test (OGTT) and 2 blood samples will be collected (fasting and after 2
      hours); 2.5 hours after, participants will begin the protocol and two standardized meals will
      be provided (0 hours and at 3 hours). An iPro2 continuous glucose monitoring (CGM) system
      will record the average interstitial glucose concentration every 5 minutes. Positive
      incremental area under the curve (iAUC) and total area under the curve (pAUC) for glucose as
      well as mean glucose (MG) will be calculated using Matlab. Differences between both protocols
      and between the two different moments will be examined using generalized estimation equation
      (GEE), adjusting for sex and age (CI 95%).
    

Detailed description: 
      Participants will be recruited to take part in a randomized crossover trial using media
      advertisements and group events within the Lisbon Metropolitan Area. In order to be part of
      this intervention, the participants will have to be men or women aged between 65 and 90
      years-old, physically active, and engaged in structured exercise at least twice a week for
      the past 6 months. People who have diabetes or any type of physical limitation that would
      prevent them from performing exercise will be excluded. Power and sample size calculations
      (G-Power 3.1.9.2) were based on an effect size of 0.78 for the glucose iAUC, a power of 0.80,
      and a significance of 0.05. The calculation yielded a sample size of 15 participants. This
      study was approved by the Ethics Committee of the Faculty of Human Kinetics (approval number:
      06/2019) and conducted in accordance with the Declaration of Helsinki and with the Convention
      on Human Rights and Biomedicine. Written informed consents were obtained from all
      participants.

      Participants will be followed in a randomized crossover trial undertaken at Faculty of Human
      Kinetics between April and August 2019. Participants will attend the laboratory on twelve
      separate occasions: visit 1 (day 1), baseline assessments for body composition; visit 2 (day
      2), cardiorespiratory fitness assessment; visit 3 (day 3), OGTT and the first randomized
      experimental protocol; visit 4 (day 4), follow-up OGTT; visit 5 (4-6 days after the first
      experimental protocol), OGTT and the remaining experimental protocol; visit 6 (day following
      the previous experimental protocol), follow-up OGTT. An additional 6 visits will be performed
      following the same rational, after a 2-week period of detraining, where participants will be
      instructed to refrain from structured exercise and reduce their physical activity. The
      follow-up assessments for body composition and cardiorespiratory fitness will be accomplished
      after the protocols. Experimental protocol order will be randomized at baseline and on the
      follow-up period after the detraining process by a third party using a computer-generated
      list of random numbers (block randomization with balanced block sizes).

      On the morning of each intervention day, participants will arrive at the laboratory at 8:00
      a.m., after a 10h fast. For 48h prior to intervention day, participants will be asked to
      refrain from structured moderate-to-vigorous physical activity (MVPA), caffeine and alcohol
      consumption. Each intervention day will have a total duration of 9.5h and will start with an
      oral glucose tolerance test. After a baseline blood collection, participants will be
      instructed to drink an oral glucose drink of 75g dissolved in water (200 ml). Two hours
      after, another blood sample will be drawn.

      At 10:30 a.m., a mixed standard meal (breakfast) will be given to the participants, marking
      the begging of the 7 hour protocol. The same standard meal will be provided at 1:30 p.m.
      (lunch). The 200-ml meal will consist of 303 kcal, 42g carbohydrate, 10g fat and 11.2g
      protein, vitamins and minerals (Nestle Health Science - Resource Energy). The participants
      will be encouraged to consume the entire meal within 5 minutes. The protocols performed will
      be: 1) uninterrupted sitting: participants will remain seated throughout 7 hours (SIT); 2)
      Sitting + moderate intensity breaks: participants will be instructed to sit throughout 7
      hours, while interrupting the sitting position every 30 minutes to perform 2 minutes of
      moderate-intensity physical activity. The breaks will consist of walk up and down the stairs
      and squats. Each person will perform these exercises alternately. During the protocol,
      participants will be allowed to go to the bathroom in a wheelchair and al-libitum water will
      be granted. The following morning after the protocol, the OGTT will be repeated.
    

Intervention name(s): Sitting + moderate intensity breaks
Intervention type(s): Behavioral
Intervention description(s): Participants will be followed in a randomized crossover trial undertaken at Faculty of Human Kinetics between April and August 2019. Participants will attend to the laboratory on twelve separate occasions: visit 1 (day 1), baseline assessments for body composition; visit 2 (day 2), cardiorespiratory fitness assessment; visit 3 (day 3), OGTT and the first randomized experimental protocol; visit 4 (day 4), follow-up OGTT; visit 5 (4-6 days after the first experimental protocol), OGTT and the remaining experimental protocol; visit 6 (day following the previous experimental protocol), follow-up OGTT. An additional 6 visits will be performed following the same rational, after a 2-week period of detraining, where participants will be instructed to refrain from structured exercise. The follow-up assessments for body composition and cardiorespiratory fitness will be accomplished after the protocols.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: sitting time; physical inactivity; breaks; glycemic control; continuous glucose monitoring; older adults