Heart Rate Variability Threshold Determined from Heart Rate Kinetics and Perceived Exertion in Overweight Young

Abstract

The anaerobic threshold (AT) can be determined through different methods, including the heart rate variability threshold (HRVT), which delimits the withdrawal of parasympathetic nerve activity and is associated to the lactate threshold. Other methods such as the inflection point of the heart rate curve (PIHR) and the fixed value of 13 points of perceived exertion (PE13) are easily obtained, but still poorly investigated, especially in overweight young, which can exhibit exacerbated physiological responses to exercise, affecting the kinetics of HR and PE. PURPOSE:To compare and verify the association between the HRVT,PIHR and PE13 in eutrophic and overweight young. METHODS: Eutrophic (EuT;N=9; 20.4±1.8years; 22.4±2.4kg/m2) and overweight sedentary young men (OW;N=11; 21.7±1.8years; 30.1±2.8kg/m2) underwent a maximal incremental test (15W/min) on a cycle ergometer, with RR intervals continuously recorded (heart rate monitor) to analyze (Kubios program) the SD1 index (standard deviation of instantaneous RR intervals) and to identify the HRVT by 2 criteria: (1) 1st. load with SD1 <3ms (HRVT1); (2) 1st. load with a difference <1ms in SD1 between 2 consecutive stages (HRVT2); HR: PIHR, identifying the maximum distance for exponential and linear adjustment; and PE: At 13 points on the 6-20-point scale (PE13). Shapiro-Wilk, One-Way ANOVA or Kruskal-Wallis test with a post-hoc of Bonferroni or Dunn’s, as well as Pearson or Spearman correlation were used for load (W), %Maximum Load (%ML), HR (bpm), %Maximum HR (%MHR) and PE (p<0.05). RESULTS: There were no differences among the methods for the EuT, and the correlation between HRVT1-2 for the load, %ML, HR, %MHR and PE was: r=0.82, 0.88, 0.75, 0.89 and 0.99, respectively, and for HR between PIHR and HRVT1-2 it was r=0.73 and 0.87, respectively. Differences were found in the loads and HR in OW, overestimated by PE13 (128.2±31W; 153±22bpm) compared with HRVT1 (76.4±43.2W; 132±8bpm) and PIHR (75±48.4W; 107±54bpm). The PE at PIHR was lower than the PE13. There was a correlation in the load and %ML between HRVT1-2 (r=0.76; 0.77);in the %LM between PIHR and HRVT1-2 (r=0.65; 0.63);and in PE between HRVT1-2 and PIHR (r=0.89; 0.62). CONCLUSIONS: The methods of determining the AT can be used interchangeably, especially the PIHR, which is easy to apply, in both groups, except for the PE13 in the OW, which seems to overestimate the AT.Supported by FAPEMAT (151411/2014),CNPq