Effects of Five Days of Physical Inactivity on Endothelial Function in Healthy Humans

Study Overview
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Brief Summary
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Physical inactivity is a significant predictor of major non-communicable diseases such as type 2 diabetes (7%), cardiovascular disease (6%), musculoskeletal disorders and some types of cancer, and has been proposed to be the 4th leading cause of death worldwide. The investigators aim is to assess the vascular (endothelial) function before and after a 5-day period of reduced activity of upper and lower limbs via an arm sling and daily step counts reduction, respectively, in healthy participants. Twelve young (ages of 18 - 35 years), healthy, males and females, recreationally active with a body mass index between 18 and 27 kg/m2 will be recruited. The participants will then randomly undergo two 5-day interventions: (A) 5 consecutive days of habitual daily levels of physical activity and matched food intake (Control trial). (B) 5 consecutive days of reduced step count by 80% compared to the Control trial combined with their non-dominant arm placed in a sling and a reduction in food (energy) intake ( 20%) to match the reduction in energy expenditure induced by inactivity (Inactivity trial). On days 1 and 6 of each experimental trial, the endothelial function of the brachial and popliteal arteries, and hand grip strength will be measured.

Official Title
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Effects of Five Days of Physical Inactivity on Endothelial Function in Healthy Humans

Conditions
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FMD

Intervention / Treatment
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* Behavioral: Inactivity


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Non-smoking Males Age (18-35 years old) Body mass index (BMI) of 18-27 kg/m2 Recreationally active Ability to give informed consent Exclusion Criteria: Smoking Any metabolic (e.g. diabetes), endocrine (e.g. hyperthyroidism) or cardiovascular (e.g. heart or blood) abnormalities including hypertension or heart failure Clinically significant abnormalities on screening including ECG abnormalities Taking routine medication that may alter cardiovascular function and blood flow (e.g. blood pressure-lowering drugs or drugs that cause hypertension) Well-trained individuals On an energy-restricted diet or seeking to lose weight High alcohol consumption (<3-4 units/day)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Control<br>5 consecutive days of normal daily levels of physical activity and matched food intake | |
| Experimental: Inactivity<br>5 consecutive days of reduced step count by 80% compared to the Control trial, whilst placing the non-dominant arm in a sling, and reduced food intake (  20%) to match the reduction in energy expenditure induced by inactivity | Behavioral: Inactivity<br>* On days 1 and 6 of each main trial, the participants will be asked to attend the laboratory after an overnight fast of at least 8 to 12h to undergo brachial and popliteal arteries FMD measurements (30 min apart) using duplex-Doppler ultrasound, followed by assessment of the hand grip strength of their non-dominant hand using a hand dynamometer.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from baseline of flow-mediated vasodilatation (FMD) of the brachial artery | The FMD of the brachial artery will be measured using an ultrasound collected at baseline and continuously for 80 seconds post-arm occlusion for 5 minutes | Over 6 minutes and 20 seconds on day 1 and day 6 of each study arm | 
| Change from baseline of flow-mediated vasodilatation (FMD) of the popliteal artery | The FMD of the popliteal artery will be measured using an ultrasound collected at baseline and continuously for 80 seconds post-arm occlusion for 5 minutes | Over 6 minutes and 20 seconds on day 1 and day 6 of each study arm | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Hand grip strength | The hand grip strength will be measured using a hand dynamometer. Three maximum hand grips separated by one minute rest at the end of each visit. | 3 minutes |