*2.4. Physical Fitness*

Physical fitness was measured in peak mechanical power (PMP (W)) and peak oxygen consumption (VO2max (mL/min), data not shown) using a bicycle ergometer (Ergoline Ergometrics 900) on which the children and adolescents exercised until exhaustion. Prior to testing, participants were familiarized with the test procedure and the bicycle ergometer was adjusted individually (height of seat and handlebar position). Testing began with a workload of 25 W and increased by 25 W every 2 min [25]. Throughout the testing session, the participant was verbally encouraged by staff to achieve maximal effort. Due to the comparably larger sample size, peak mechanical power (*n* = 238) was used as a proxy for physical fitness instead of VO2max (*n* = 228). Test results were related to body weight as W/kg.
