Fitness for what?
D000328:Adult; D000367:Age Factors; D002302:Cardiac Output; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology; D010101:Oxygen Consumption; D010806:Physical Education and Training; D005082:Physical Exertion; D010809:Physical Fitness; D012737:Sex Factors; D013177:Sports; D013997:Time Factors