Ponto de deflexão da frequência cardíaca como método não invasivo para determinar o limiar anaeróbio no meio aquático em idosas treinadas

Introduction: The anaerobic threshold (AT) determination is important for individualizing the aerobic training prescription. Objective: To compare and verify the agreement between oxygen uptake (VO2), heart rate (HR), and rate of perceived exertion (RPE) at the AT determined by the ventilatory threshold (VT) and heart rate deflection point (HRDP) methods during an aquatic incremental test in trained older women. Methods: Nine elderly women (64.3 ± 4.4 years) engaged in a water-based training program in the last three months performed a maximum incremental test using the water-based stationary running exercise. The test started at a 70 b.min-1 cadence for 2 min, followed by 15 b.min-1 increments every 2 min until exhaustion. VO2, HR and RPE were measured throughout the test and the AT was identified for each method (i.e., VT and HRDP) by three experienced physiologists. Paired t-test and Bland-Altman analysis were used for data analysis (α=0.05). Results: There was no difference between the VT and HRDP methods (p>0.05) and the Bland-Altman analysis showed acceptable agreement between them for all investigated outcomes (VO2: 22.9 ± 5.1 vs. 23.5 ± 4.7 ml.kg-1.min-1, IC95%: -3-+4 ml.kg-1.min-1; HR: 147 ± 11 vs. 147 ± 11 bpm, IC95%: -9-+8 b.min-1; RPE: 16 ± 1 vs. 16 ± 1, IC95%: -2-+3). Conclusion: Based on these findings, both HR and RPE determined by the HRDP can be used as valid parameters and practical tools for field prescription of intensity during water-based exercises in elderly trained women.