title: Change in double product during stepwise incremental exercise.
abstract: The purpose of this study was to observe the change in double product with increases in the intensity of bicycle exercise. Eleven young male adults participated in this study. The subjects performed graded bicycling exercise increasing 20 watts every 2 min from 0 watts until the heart rate (HR) reached 170 beats.min(-1). During exercise systolic blood pressure (SBP) and HR were continuously measured. Initially SBP gradually increased with the increase in workload, but when the intensity of exercise became even higher, the rate of increase slowed. On the other hand, the increase in HR was very small during the initial 5 min of exercise and when the intensity of exercise increased, the rate of increase of HR became higher. The polygonal regression analyses on the relation of double product to elapsed time revealed clear break-points. On average, the break-point of double product was 6.6 min (56 watts). These results clearly showed that the break-point of double product with an increase in workload appeared even though the workload was relatively low.
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Japan. kyutae73@hiroshima-u.ac.jp
authors.forename: Kyu Tae
authors.initials: KT
authors.lastname: Kim
authors.forename: Seung Wook
authors.initials: SW
authors.lastname: Choi
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Takahashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kurokawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamasaki
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D001794:Blood Pressure; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D012016:Reference Values