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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
The interacting effects of breaking up prolonged sitting with a single bout of exercise, plus regular short intervals of exercise, on blood flow to the brain and cognitive function in overweight adults
Scientific title
Taking a break for brain health: Interacting effects of exercise bouts with breaks in sitting time on cognitive and cerebrovascular function in overweight adults
Secondary ID [1] 285664 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Brain Breaks
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Cognitive Function 292099 0
Condition category
Condition code
Mental Health 292435 292435 0 0
Studies of normal psychology, cognitive function and behaviour
Public Health 292436 292436 0 0
Health promotion/education
Metabolic and Endocrine 292437 292437 0 0
Normal metabolism and endocrine development and function

Study type
Description of intervention(s) / exposure
We propose a randomised cross-over trial in 48 sedentary and overweight adults aged between 55-80 years, to be undertaken (using a balanced orthogonal design) in two testing sites. The study will involve three acute experimental conditions (each of one day duration), separated by a minimum 7-day washout period to account for any residual physiological effects of acute exercise that may persist for up to 72 hours. To eliminate bias, the order in which participants undertake the three experimental conditions will be determined from a computer-generated, randomised sequence. Each experimental condition (detailed below) will be conducted in a controlled, laboratory setting to minimise the potential confounding influences and the inherent variability of less-controlled and more-variable ‘real-world’ settings. In all experimental conditions participants will arrive, having fasted for 10 hours, and be seated in a comfortable lounge-chair and instructed to minimise excessive movement and avoid all activities requiring cognitive engagement (eg: cross-words, Sudoku).
1) Uninterrupted Sitting: Participants will sit quietly for eight hours, with breakfast and lunch provided during this period.
2) Continuous Exercise + Uninterrupted Sitting: After sitting quietly for 1 hour (steady state) participants will complete a 30 minute bout of continuous moderate-intensity exercise on a motorised treadmill , at a predetermined power output corresponding to a range of between 65% -75% of maximal heart rate. Following this participants will sit quietly for the remaining 6 1/2 hours.
3) Continuous Exercise + Interrupted Sitting: Identical procedure to condition 2, however, after the continuous exercise bout, participants will remain seated for a further 30 minutes before completing a three-minute bout of light-intensity walking on a motorised treadmill at They will then return to the seated position. This procedure will be repeated on 12 occasions every 30 minutes for a total of 36 minutes of light-intensity activity. The scientific rationale for the utilisation of the proposed protocol has been deliberately guided by our recently published findings (2min every 20min, total 28min) but modified slightly to accommodate the appropriate timing of the proposed testing procedures.
The research group consisting of the coordinator, research nurse and assistant will be responsible for monitoring adherence to the interventions
Intervention code [1] 289521 0
Intervention code [2] 289522 0
Intervention code [3] 289523 0
Comparator / control treatment
One day of prolonged sitting without activity breaks: Participants will sit quietly in a comfortable chair for an 8-hour period.
Control group

Primary outcome [1] 292292 0
Cognitive function: Measured using a computerized battery of tests (CogState - that has been specifically developed for brief repeated testing of cognitive performance in clinical and research trials, with good acceptability, efficiency and stability, and minimisation of practice effects. The test battery will cover multiple cognitive domains with a primary focus on executive function (most likely to be influenced by acute exercise). The battery will comprise: 1) Identification task to assess visual attention and vigilance; 2) N-back to assess attention and working memory; 3) Groton Maze Learning to assess executive function including spatial problem solving; 4) Detection task to assess psychomotor function and speed of processing; and 5) One card learning task to assess visual learning and memory; for a total administration time of approximately 25 minutes.
Timepoint [1] 292292 0
4 times over 8 hours, including baseline during the first hour after arrival, and at +95 mins, +185 mins and + 395 minutes after the start of the exercise bout.
Secondary outcome [1] 308658 0
Blood measurements: Venous blood samples will be collected by a trained nurse via an in-dwelling catheter in the antecubital vein. Between 6mL- 20mL (0.4 - 1.3 tablespoons) will be collected on each occasion, of which a fraction will be sent immediately to Alfred Pathology (for the Baker IDI site) or University of Western Australia (UWA) for that site, for analysis of glucose, triglycerides, full blood evaluation and lipid profile. The remaining blood will be centrifuged and the plasma fraction removed and frozen at at -80°C for later analysis related to this trial. The cannula will be flushed with normal saline following every blood draw to maintain its patency.
Timepoint [1] 308658 0
A total of 13 blood draws will be done across the experimental day. Time points include baseline, +30 mins, +60 mins, +90 mins, +120 mins, +150 mins, +180 mins, +220 mins, +270 mins, +300 mins, +330 mins, +360 mins and +420 minutes after the breakfast meal.
Secondary outcome [2] 309303 0
Blood pressure: Hourly resting brachial arterial blood pressure will be taken after a five minute rest period, three times, at one-minute intervals, using an automated oscillometric blood pressure monitor 10 (Dinamap Vital Signs Monitor 18465X, Criticon, Florida, USA).
Timepoint [2] 309303 0
At baseline , +30 mins, + 90 mins, + 150 mins, + 210 mins, + 270 mins, + 330 mins, +390 mins and + 420 mins after the start of the exercise bout.

Key inclusion criteria
BMI equal or greater than 25 kg/m2 but less than 45 kg/m2 and English-speaking
Minimum age
55 Years
Maximum age
80 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Pregnancy; employment in a non-sedentary occupation; currently watching less than 3 hours of television per day; regularly engaged in moderate-intensity exercise equal or greater than 150 min/week for longer than 3 months; cognitive impairment as evaluated during screening via mini-mental exam; diagnosed diabetes; use of glucose/lipid lowering medication, antidepressant medications, beta blockers; anti anxiety medication, peri-menopausal or menopausal women; excessive alcohol consumption; known physical activity contraindications, major illness/physical problems (acute or chronic) that may limit their ability to perform the exercise or activity bouts.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Interested volunteers will receive written information about the study in lay terms and a full description of the inclusion/exclusion criteria. After obtaining informed consent and background information, the potential participants will be screened to confirm eligibility. Once a potential subject has been deemed eligible, the subject will be randomised to the order of experimental conditions. The method for allocation concealment is closed envelopes. The allocation information will be placed in numbered envelopes (1 allocation per envelope) by an independent researcher. After a subject has been enrolled in the study, the study co-ordinators will contact an independent staff member to ask for the sequence of experimental conditions. The independent staff member will keep a log of the date and time the envelope was opened, the envelope number, the initials and gender of the participant and the order of experimental conditions. The study co-ordinator will also keep a record of this information.

Using the randomization schedule, the independent researcher will, after data collection, create a dataset containing outcome, other relevant variables and the random unique code but will not include overt information on the experimental conditions, subject initials, and date of data collection. Data collected under the experimental conditions will be assigned a code (e.g., 0 and 1) unknown to the data analyst and the research team (they would be blinded to the randomization process and condition). Once the data are analysed, the experimental-condition codes will be revealed and the dataset will be checked for errors.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
The randomisation allocation sequence will be generated using computer-generated random numbers in a Latin-square experimental design.
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
Power calculations have been made in relation to the primary outcome measures of cognitive function and reflect the cross-over design of the study. Based on recent evidence we estimate the effect sizes (Cohen‘s d for repeated measures; ES) of additional exposure to light-intensity breaks (as compared to sole exposure to a moderate-intensity exercise bout) would be ~0.40 for executive function tasks, which is similar to the effect size previously-observed effects sizes for glucose, insulin, systolic blood pressure and diastolic blood pressure. The estimated ES of a moderate-intensity exercise bout as compared to the prolonged sitting is 0.7717. Sample size calculations indicate that 52 subjects would be needed to detect an ES of 0.40 based on one baseline and one post assessment per experimental condition. However, the proposed trial will include three post assessments per experimental condition, which gives 3 x subjects data points per condition. Assuming a within-subject, within-condition correlation between assessments of 0.6, the effective sample size per condition is [3 x subjects]/[1+(3-1)*0.6] = [3 x subjects]/2.2. To achieve an effective sample size of 52, we need 52*(2.2/3) ~ 40 subjects. Thus, the sample size needed to detect an ES of 0.40 with a power of 0.80 and a two-tailed probability of 0.05 is 40 (with three post-assessment measures per person and experimental condition). In a recent trial adopting a similar design, we achieved a 15% attrition rate. However, as a safeguard, assuming a conservative attrition rate of ~20%, we will aim to recruit 48 participants (24 per site).

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 289493 0
Government body
Name [1] 289493 0
National Health and Medical Research Council (NHMRC)
Address [1] 289493 0
National Health and Medical Research Council
GPO Box 1421
ACT 2601
Country [1] 289493 0
Primary sponsor type
Baker IDI Heart and Diabetes Institute
Baker IDI Heart and Diabetes Institute
Physical Activity Laboratory
Level 4
The Alfred Centre
75 Commercial Road
VIC 3004
Secondary sponsor category [1] 288176 0
Name [1] 288176 0
University of Western Australia (UWA)
Address [1] 288176 0
School of Sport Science, Exercise and Health M408
University of Western Australia
35 Stirling Highway
Parkway Entrance 3
WA 6009
Country [1] 288176 0

Ethics approval
Ethics application status
Ethics committee name [1] 291247 0
Alfred Hospital Ethics Committee (EC00315)
Ethics committee address [1] 291247 0
Office of Research Governance
Ground Floor Linay Pavilion
The Alfred
55 Commercial Road
VIC 3004
Ethics committee country [1] 291247 0
Date submitted for ethics approval [1] 291247 0
Approval date [1] 291247 0
Ethics approval number [1] 291247 0

Brief summary
In recent years the, role of physical activity in healthy brain ageing has also been a major topic of investigation. Observational studies have shown that adults who are physically active are more likely to have better performance on several cognitive test tasks, including those involving higher order executive functions. Regular physical activity during midlife has also been associated with a significantly slower rate of cognitive decline and reduced risk of developing dementia in later adulthood. Such evidence has prompted calls to investigate the potential role of regular exercise as a protective factor against cognitive decline and dementia.

Traditionally, the physical activity public health focus has been directed at purposeful exercise for health benefits, at a moderate to vigorous-intensity. Emerging evidence suggests that targeting the adoption of moderate to vigorous exercise in the population should not be the only consideration; a focus on reducing sedentary behaviour may be equally important for health outcomes. Previous work has provided epidemiological and experimental evidence on the independent associations of sedentary behaviour with metabolic health.

Together, with The University of Western Australia, we propose to undertake a randomised cross-over trial in 48 older overweight adults involving three experimental conditions. All participants will complete each of the three (one-day) experimental conditions, separated by a 7-day washout period to account residual physiological effects of the acute exercise. We will examine whether, compared to uninterrupted sitting, there are acute effects of a single bout of moderate-intensity exercise, with or without intermittent (3 min) light-intensity activity breaks from prolonged sitting, on cognitive function and metabolic function in overweight adults aged between 55 and 80 years of age. We hypothesise that (1) a continuous 30 minute bout of moderate-intensity exercise will lead to improvements in cognitive function relative to uninterrupted sitting, and (2) that the magnitude of the improvement in cognitive function resulting from the exercise bout, compared to uninterrupted sitting, will be greater when an exercise bout is combined with a series of brief intermittent light-intensity breaks from prolonged sitting. Furthermore, we aim to examine an exploratory hypothesis that the improvement in cognitive function associated with both the continuous 30 minute bout of exercise and the brief intermittent breaks from prolonged sitting will be associated with mechanisms which increase cerebral blood flow and glucose uptake.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 48962 0
A/Prof David Dunstan
Address 48962 0
Physical Activity Laboratory
Baker IDI Heart and Diabetes Research Institute
Level 4, Alfred Centre
99 Commercial Road
VIC 3004
Country 48962 0
Phone 48962 0
+61 3 8532 1873
Fax 48962 0
+61 3 8532 1150
Email 48962 0
Contact person for public queries
Name 48963 0
A/Prof David Dunstan
Address 48963 0
Physical Activity Laboratory
Baker IDI Heart and Diabetes Research Institute
Level 4, Alfred Centre
99 Commercial Road
VIC 3004
Country 48963 0
Phone 48963 0
+61 3 8532 1873
Fax 48963 0
+61 3 8532 1150
Email 48963 0
Contact person for scientific queries
Name 48964 0
A/Prof David Dunstan
Address 48964 0
Physical Activity Laboratory
Baker IDI Heart and Diabetes Research Institute
Level 4, Alfred Centre
99 Commercial Road
VIC 3004
Country 48964 0
Phone 48964 0
+61 3 8532 1873
Fax 48964 0
+61 3 8532 1150
Email 48964 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary