Rationale: Proteins released from muscle during and shortly after exercise, often referred to as myokines, may be central to our understanding of the cross-talk during and after exercise between skeletal muscles and other organs, in particular the liver. So far only a few myokines are identified (e.g. IL-6, IL-8, IL-15, TNF-alpha). Taking into account the role of these several known myokines in developing insulin resistance, revealing new putative myokines might provide valuable information and a direction for future research on the pathogenesis and treatment of type 2 diabetes mellitus.

Objective: The objective of the present study is to identify novel myokines, expression of which is altered in skeletal muscle after a single bout of exercise.

Study design: experimental study. Study population: Ten healthy, male subjects between 40 and 60 years of age and BMI < 30 kg/m2, will participate in this study.

Intervention: A single exercise bout that consists of one hour one-legged cycling on a adapted recumbent cycle ergometer at a submaximal rate. The non-exercising leg will serve as control for the exercising leg.

Main study outcomes: Main study outcomes include upregulation of genes in skeletal muscle after exercise (with a focus on genes encoding myokines) and changes of blood plasma levels of selected proteins after exercise.

Inclusion Criteria:

• Age 40-60 years
• Male gender
• BMI < 30 kg/m2

Exclusion Criteria:

• Exercising regularly (> 2 times a week, > 3 hour in total per week)
• Unstable body weight (weight gain or loss > 3 kg in the past three months)
• Following, or have recently followed a (weight-loss) diet
• Donated or intended to donate blood 2 months before until two months after the study
• Medical condition that can interfere with the study outcome (i.e. cardiovascular disease, pulmonary disease)
• Systolic blood pressure >160 mmHg and/or diastolic blood pressure >100 mmHg
• Use of medications known to interfere with gene expression in the muscles (i.e. statins, fenofibrate).
• Use of antithrombotic therapy (marcoumar, sintromitis).
• Diagnosed diabetes mellitus type 1 or 2.
• Drugs or alcohol abuse ( > 3 glasses of alcoholic beverages a day).
• (Chronic) injuries of the locomotor system that can interfere with the intervention
• Participated in another study within the last six months