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Trial registered on ANZCTR

Registration number

ACTRN12612001003864

Ethics application status

Approved

Date submitted

18/09/2012

Date registered

18/09/2012

Date last updated

18/09/2012

Type of registration

Retrospectively registered

Titles & IDs

Public title

Interval sprinting and cardiovascular function

Scientific title

The effect of high-intensity intermittent exercise on fat loss, autonomic, and vascular function of overweight men.

Secondary ID [1]

N/A

Universal Trial Number (UTN)

N/A

Trial acronym

N/A

Linked study record

Health condition

Health condition(s) or problem(s) studied:

Overweight/obesity

insulin resistance

Condition category

Condition code

Metabolic and Endocrine

Diabetes

Cardiovascular

Normal development and function of the cardiovascular system

Diet and Nutrition

Obesity

Intervention/exposure

Study type

Interventional

Description of intervention(s) / exposure

The training regime will involve high-intensity, intermittent work periods separated by low intensity rest periods with a work to rest ratio of 8s:12s. The total exercise time per session will start at 10 min. and progress over the training period to a total of 20 min. These time allocations include a 5 minute warm-up. After subjects have completed the session they will complete five minutes of cool down followed by stretching to reduce the likelihood of post exercise soreness. All training sessions will be supervised. Thus, the exercise group will complete three 20-minute cycling sessions per week, for 12 weeks. Subjects allocated to the control group will be asked to maintain their normal daily activity patterns until after the study is complete, at which time they will be given an exercise program if they so desire.

Intervention code [1]

Lifestyle

Intervention code [2]

Treatment: Other

Intervention code [3]

Prevention

Comparator / control treatment

No treatment

Control group

Active

Outcomes

Primary outcome [1]

Body and visceral fat assessed by DEXA and computed tomography.

Timepoint [1]

Before the start and after the 12-week intervention.

Secondary outcome [1]

Maximal aerobic fitness assessed by a metabolic cart using a stationary electronic bicycle. Subjects cycle at 30 watts for 3 minutes which is then increased by 30 watts every minute until exhaustion.

Timepoint [1]

Before the start and after the 12-week intervention.

Secondary outcome [2]

Cardiovascular function assessment: resting heart rate, stroke volume, cardiac output, systolic time intervals (indicants of myocardial contractility), basal thoracic impedance, systolic and diastolic BP, mean arterial pressure, and total peripheral resistance will be continuously assessed through impedance cardiography. BP will be assessed beat-by-beat (Jentow). Arterial baroreceptor sensitivity will be assessed through spectral analysis of systolic BP variability. Heart period variability (an indirect assessment of vagal influence on the heart) will also be assessed through spectral analysis. Forearm blood flow will be measured through strain gauge plethysmography. Whole body arterial compliance, aortic impedance, regional aortic stiffness, and pulse wave velocity will be assessed non-invasively in large and medium sized arteries using applanation tonometry.

Timepoint [2]

Before the start and after the 12-week intervention.

Secondary outcome [3]

Vasodilatory capacity will be determined through maximal hyperaemia measurement by occluding the venous cuff to 50 mmHg above subject's systolic pressure for 10 min. Hyperaemia blood flow will be measured immediately (at least 5 seconds) after the arterial cuff is deflated. Hyperaemia blood flow will be obtained every 5 seconds for 1 min then every 15 seconds thereafter for 3 minute.
Forearm blood flow will be determined by measuring the rate of increase in volume, and the flow rate will be expressed as a volume change per unit time such as cc's of blood flow per 100 cc's of tissue per minute. Limb blood flow will be assessed using a venous occlusion technique. This technique is based on the principle that during venous occlusion the compression of the veins results in arterial swelling, which results in changes in arterial volume. At this time the rate of the arterial inflow is measured. The increase in circumference when the venous cuff is inflated is recorded as a change in electrical resistance of the strain gauge. Forearm vascular resistance will be determined by dividing mean arterial pressure by forearm blood flow. The silastic strain-gauge plethysmograph will be attached to the widest part of the forearm, venous cuff will be applied to the upper arm, and the arterial cuff will be attached to the wrist to exclude the blood flow from the hand. Forearm blood flow will be obtained by inflating the venous cuff to 50 mmHg for 5 seconds then deflated for 15 seconds. Forearm blood flow will be measured during baseline, during and after the Stroop and isometric tasks. The average of six blood flow measurements will be used to determine forearm blood flow during the above conditions.

Timepoint [3]

Before the start and after the 12-week intervention.

Eligibility

Key inclusion criteria

Overweight sedentary men aged 18-35 years will be recruited for this study. Men have greater abdominal fat
stores than women and are more likely to have significant changes in fat deposition patterns with exercise. The
overweight males will require fasting levels of insulin above 12.00 ulU/ml. Subjects will possess a BMI between 25 and 35 kg/m2.

Minimum age

18 Years

Maximum age

35 Years

Sex

Males

Can healthy volunteers participate?

Key exclusion criteria

Subjects will be excluded if they have symptoms of current infection, known diabetes, a chronic inflammatory condition, treated dyslipideamia, and liver disease or malignancy. Smokers, subjects with excessive alcohol consumption, (>25 U/week), and those taking NSAIDS, steroids will also be excluded.

Study design

Purpose of the study

Treatment

Allocation to intervention

Randomised controlled trial

Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)

Sealed envelopes by a researcher not involved with the carrying out of the intervention

Methods used to generate the sequence in which subjects will be randomised (sequence generation)

Coin tossing to determine either the exercise or control group

Masking / blinding

Blinded (masking used)

Who is / are masked / blinded?

Intervention assignment

Parallel

Other design features

N/A

Phase

Not Applicable

Type of endpoint/s

Efficacy

Statistical methods / analysis

Recruitment

Recruitment status

Completed

Date of first participant enrolment

Anticipated

1/06/2009

Actual

Date of last participant enrolment

Anticipated

Actual

Date of last data collection

Anticipated

Actual

Sample size

Target

Accrual to date

Final

Recruitment in Australia

Recruitment state(s)

Funding & Sponsors

Funding source category [1]

Government body

Name [1]

Diabetes Australia

Address [1]

Diabetes Australia
145 Macquarie Street
Sydney, NSW 2000

Country [1]

Australia

Primary sponsor type

University

Name

University of New South Wales

Address

University of New South Wales
High Street
Randwick
Sydney NSW 2052

Country

Australia

Secondary sponsor category [1]

None

Name [1]

Address [1]

Country [1]

Ethics approval

Ethics application status

Approved

Ethics committee name [1]

UNSW Ethics Committee

Ethics committee address [1]

Ethics Secretariat
UNSW Grants Management Office
UNSW 
High Street, Randwick, NSW 2052

Ethics committee country [1]

Australia

Date submitted for ethics approval [1]

Approval date [1]

15/12/2008

Ethics approval number [1]

HREC 08365

Summary

Brief summary

Obesity is becoming pandemic in the Australian population. Successful attempts to lose weight and maintain weight loss are dependent on regular physical activity. This training study will establish if high-intensity intermittent exercise will induce fat loss in overweight men. The current wisdom is that one should exercise at relatively low intensity because at this level fat is the dominant substrate used as a fuel.  We are proposing that there is still significant fat utilization at higher exercise intensities and exercising at this higher intensity will lead to greater fat loss over time, as well as greater gains in health related fitness parameters. The opportunity to achieve greater benefits from a reduced time commitment may act as an inducement for reluctant exercisers to commence a fitness program.  To our knowledge, the effects of training at higher intensities on regional and total fat deposits of overweight men has not been measured before.   Pre- and posttraining testing will include body composition measures of anthropometry, bioimpedance, DEXA, CT, and vascular assessment. We hypothesize that 12 weeks of interval sprinting will result in significant fat loss and significant increase in aerobic fitness.

Sixty subjects will be recruited and randomly assigned to one of two groups: Group 1 (n=30) interval training with work:rest ratio of 8 s: 12 s and Group 2 (n=30) a non-exercising control group.  Testing protocols will also include a VO2max cycle ergometer test that will allow determination of maximum oxygen carrying capacity.  Blood sampling will be used to determine blood lactate, fasting glucose, catecholamines, insulin, adiponectin, leptin and glycerol concentrations. Subjects will be given food diaries to complete to ensure that total energy intake, as well as macronutrient balance, is maintained over the study period. Subjects will also perform three tasks (see below) before and after the intervention so that vascular response can be assessed.

 Subjects will also be asked to complete a food intake diary in which they record the quantity and type of food they eat during each day.  Random days will be selected for this purpose.  

Tasks 
The Stroop task involves verbally responding to coloured words displayed every second on a computer  (5 minutes). An isometric handgrip task will involve subjects contracting a handgrip dynamomanometer at 30% of their maximal voluntary contraction for 5 min.  Blood flow will be measured in the non-exercising arm. The leg cycle exercise task will involve subjects cycling at a low-moderate level of their maximal oxygen uptake (40%) on a stationary ergometer 8 minutes). Blood flow will also be assessed in the non-exercising arm. Each subject will be involved in a familiarity session involving exposure to the different tasks.

Trial website

Trial related presentations / publications

Public notes

Contacts

Principal investigator

Name

Address

Country

Phone

Fax

Contact person for public queries

Name

Steve Boutcher

Address

Department of Pharmacology
Faculty of Medicine
University of New South Wales
High Street, Randwick
Sydney, NSW 2052

Country

Australia

Phone

+61 2 9385 2877

Fax

+61 2 9385 1511

s.boutcher@unsw.edu.au

Contact person for scientific queries

Name

Steve Boutcher

Address

Department of Pharmacology
Faculty of Medicine
University of New South Wales
High Street, Randwick
Sydney, NSW 2052

Country

Australia

Phone

+61 2 9385 2877

Fax

+61 2 9385 1511

s.boutcher@unsw.edu.au

No information has been provided regarding IPD availability

What supporting documents are/will be available?

No Supporting Document Provided

Results publications and other study-related documents

Documents added manually

No documents have been uploaded by study researchers.

Documents added automatically

No additional documents have been identified.

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