Participants will perform three endurance training sessions weekly for 12 weeks. All participants will be randomly assigned to the protein supplementation group or the placebo (iso-caloric carbohydrate) group. During the 12 weeks endurance training program participants allocated to the protein group (30 g protein per beverage) will receive a protein drink after exercise and prior to sleep at night on training days. On non-training days participants will only receive a protein drink before sleep. Participants allocated to the carbohydrate group (30 g carbohydrates) will receive a carbohydrate drink instead of a protein drink.

In the proposed study, the effects of protein supplementation after training and before sleep on VO2max and performance will be assessed during 12 weeks endurance exercise training in untrained healthy young men. The ready to drink carbohydrate beverage consists of 30g carbohydrate or 30g protein. Previous studies show that the supplementation of 30g protein is in the optimal range to stimulate the muscle protein synthetic response following resistance type exercise. The protein supplementation group in the present study will be compared with an iso-caloric carbohydrate group. In addition, to the pre- and post-intervention biopsies 1 additional muscle biopsies will be taken (in week 6) during the 12 week intervention period. This will create a unique opportunity to establish the timeline of the skeletal muscle adaptive response at functional and mechanistic level following prolonged endurance exercise training, including potential differences between both groups.

Inclusion Criteria:

• Male
• Age between 18 and 30 years of age
• BMI between 18.5 - 25 kg/m2
• Recreationally active, performing sports on a non-competitive basis
• Maximal wattage of > 5 watt per kg bodyweight (screening measurement)
• Willing to give muscle biopsies
• Willing to give blood samples
• Having a general-practitioner
• Consumption of alcohol beverages is less than 21 per week
• Able to perform three exercise sessions weekly for 10 weeks

Exclusion Criteria:

• Medical condition that can interfere with the study outcome (i.e. cardiovascular disease, pulmonary disease, liver or renal disease, diabetes mellitus type 1 or 2)
• Having a lactose and/or gluten intolerance
• Use of systemic medication (with the exception of antihistaminic medication and the use of occasional painkillers)
• (Chronic) injuries of the locomotor system (e.g. musculoskeletal/orthopedic disorders) that can interfere with the intervention
• Participants who are enrolled in an interventional biomedical research project or have received an investigational new drug or product with the last 30 days prior to screening.
• Smokers and use of illicit drugs
• Blood donor during the study and in the three months before start of the study
• Employed, or intern, or working on a thesis at the department of Human Nutrition at Wageningen University & Research
• Participating in another scientific study (except EetMeetWeet)

Young healthy men