For decades, it has been known that post-meal blood glucose concentrations were associated with the risk of T2D, which was reflected in early diagnostic guidelines. The oral glucose tolerance test (OGTT) has been used since at least 1923 and has remained the most common test for assessing glucose tolerance. Arterial blood (or arterialised blood using heated hand technique) is most appropriate for determining glucose tolerance and insulin sensitivity since this best represents the concentrations of metabolites and hormones that peripheral tissues are exposed to. It is essential to investigate whether venous blood (sometimes used during an OGTT) is representative of arterialised blood during an OGTT, and under different metabolic conditions.

The investigators want to understand whether OGTT-derived insulin sensitivity indices differ from venous and arterialised blood; and 2) investigate whether metabolic status (i.e. rest vs lower-limb exercise) influences the difference between forearm venous and arterialised concentrations of glucose and insulin during an OGTT.

Inclusion Criteria:

• Aged 18-49 years
• Able and willing to safely comply with all study procedures
• Able to provide written informed consent for participation

Exclusion Criteria:

• Diagnosis of any bleeding disorder or taking medication which impacts blood coagulation
• The presence of any contraindications to maximal exercise testing, as determined using a physical activity readiness questionnaire (PAR-Q).
• Any diagnosis of metabolic disease (i.e. cardiovascular disease or type 2 diabetes).