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The upper limit of the cardiorespiratory training zone (40-84%HRR) is overestimated for postmenopausal women

Journal of science and medicine in sport / Sports Medicine Australia | 22 Jan 2013

F Arag√£o, MH Moreira, RE Gabriel and CG Abrantes
Objective The purpose of this study was to examine the heart rate reserve (HRR) at first and second ventilatory thresholds (VT’s) in postmenopausal women and compare it with optimal intensity range recommended by the ACSM (40-84%HRR). An additional aim was to evaluate whether a higher aerobic power level corresponded to a higher HRR at VT’s. Methods Fifty-eight postmenopausal women participated in this study (aged 48-69). A graded 25Wmin(-2) cycle ergometer (Monark E839) exercise protocol was performed in order to assess aerobic power. The heart rate and gas-exchange variables were measured continuously using a portable gas analyzer system (Cosmed K4b). The first (VT(1)) and the second (VT(2)) VT’s were determined by the time course curves of ventilation and O(2) and CO(2) ventilatory equivalents. A K-means clustering analysis was used in order to identify VO(2max) groups (cut-off of 30.5mlkg(-1)min(-1)) and differences were evaluated by an independent sample t-test. Bland-Altman plots were performed to illustrate the agreement between methods. Results The women’s HRR values at VT(1) were similar to 40%HRR in both VO(2max) groups. At VT(2) both VO(2max) groups exhibited negative differences (P<0.01) for the predicted 84%HRR intensity (-14.46% in the lower VO(2max) group and -16.32% in the higher VO(2max) group). Conclusions An upper limit of 84% overestimates the %HRR value for the second ventilatory threshold, suggesting that the cardiorespiratory target zone for this population should be lower and narrower (40-70%HRR).
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Threshold, Heart rate, Thresholds, K-means clustering, Limit superior and limit inferior, The Higher, Pulse, Student's t-test
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