Development of the automated double product break-point determining system

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Catecholamine concentrations are known to sharply increase in the blood at work rates above the blood lactate threshold (LT), and thus we hypothesized that the double product (DP,heart rate-systolic blood pressure product) may also abruptly increase at work rates above the LT.This research was aimed at devising automatic DPBP measurement system and to clarify whether the DPBP could determined during a ramp test on treadmill and cycle ergometer using thsi system. We devised the system which could measure SBP and HR automaticaly and displayd those on the monitor during exercise using a personal computer (NEC PC98). By this modification, we could automatically measure the DP almost every 15 sec. The DPBP was automatically determined using a computer algorithm as follows. The liner regression lines of DP as a function of W were calculated for all possible divisions of the data into two adjustment groups, and then the break-point was determined by the intersection of the two lines which represented the minimum residual sum of the squares. This modified apparatus could be used to determine DPBP in all suqomects including elderly and cardiac patient with a ramp test on treadmill as well as cycle ergometer. The test-retest reliability to determine the DPBP and correlation among the determined DPBP,LT,and VT was fairly good. Based on the above findings we therefore concluded that DPBP determined by this system is easy and a valid for evaluating a physical fitness and prescribing a optimal intensity.