Healthy Japanese subjects aged 20–78 years were enrolled by
stratified randomization based on age group and gender. The randomized
allocation of the subjects was conducted by the data center
of the nonprofit organization, the Japan Heart Club. At least 10 subjects
were enrolled for each decade of age and gender; however, the
higher-incline ramp protocols were excluded for the elder and/or
female subjects, depending on their exercise capacity and anticipated
exercise time. To be included, subjects must (1) have had
no experience of cardiac or pulmonary disease with no symptoms,
(2) measure 145–190 cm in height, and (3) have a body mass index
(BMI) of 17.6–28.6 (−20% and 30% of BMI 22). Excluded were those
who (1) had smoked within the past year, (2) regularly exercised
more than twice a week, (3) showed abnormal blood pressure at
rest, and (4) had an abnormal resting electrocardiogram (ECG).