This study will investigate the influence of increased sedentary time on long-term measures of muscle protein synthesis and metabolic health. The investigators will test the hypothesis that increased time spent in sedentary behaviours will lead to a reduction in long-term measures of muscle protein synthesis and compromised metabolic health.

Sarcopenia, the loss of muscle mass with age, is thought to be accelerated by an inactive, sedentary lifestyle. Increased sedentary time has consistently been associated with lower muscle mass and compromised metabolic health. However, there is currently a lack of direct evidence to support these associations.

Therefore, this study will investigate whether increased sedentary time (reduced step count and exercise cessation) directly influences long-term measures of muscle protein synthesis and metabolic health in young, active adults. Following a 7 day period of normal habitual physical activity, participants will undertake a 7 day period of step reduction and exercise cessation. It is hypothesised that 7 days of increased sedentary time will result in a reduction in long-term rates of muscle protein synthesis and a worsening of metabolic health.

Inclusion Criteria:

• Body mass index (18.5-29.99 kg/m2)
• Active - defined as: ≥ 7000 steps per day (assessed during screening) and taking part in regular exercise (defined as participation in ≥ 3 sessions of aerobic and/or resistance exercise type sessions a week for ≥ 6 months prior to recruitment)
• Good general health

Exclusion Criteria:

• Lidocaine allergy
• Hypertension (≥140/90 mmHg)
• Current participation in another clinical study
• Previous participation in this study
• Bleeding disorder/s
• Current or recent smoker
• Past history of substance abuse and/or taking prescription or non-prescription medication (e.g., beta-blockers, insulin or thyroxine) or supplements that may influence normal metabolic responses.
• Participants who have previously (within 5 years of the present study) had 4 or more muscle biopsies obtained from the thigh quadriceps region will be ineligible.