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.

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)