Physical ExertionShort-Wave TherapyExerciseCross-Over StudiesDeath, SuddenDeath, Sudden, CardiacExercise TestOccupational DiseasesConfidence IntervalsRisk FactorsSudden Infant DeathMyocardial InfarctionPhysical FitnessMotor ActivityHeart RatePhysical EndurancePhysical Therapy ModalitiesPhysical Education and TrainingSportsPerceptionOxygen ConsumptionBicyclingDyspneaErgometryQuestionnairesWalking