A Simple Approach to Assess VT During a Field Walk Test

Abstract

We aimed to examine whether the ventilatory threshold (VT) during an incremental shuttle walk test (ISWT) could be determined using heart rate variability (HRV) analysis. Further aims were to assess variables capable of predicting performance in the ISWT and the intensity of this test. Beat-to-beat RR intervals and gas exchange values in 10 healthy subjects (31-83 years; 7 men) were collected during the ISWT. The ventilatory equivalent was used to assess VT from respiratory components. To determine the HRV threshold (HRVT), the instantaneous beat-to-beat variability values of the RR intervals at each stage of exercise were graphically plotted against walking speed (WS). The oxygen consumption at HRVT was calculated (VO2HRVT). No significant differences were found between walking speed (WS) at VT and WS at HRVT (5.04±1.00 vs. 5.10±1.04 km/h; p=0.89). Linear regression analysis revealed a strong correlation between VO2VT and VO2HRVT (r(2)=0.896). The Bland and Altman plot analysis revealed an agreement between VO2VT and VO2HRVT (-0.05; 95%CI: -0.30-0.20 L/min). Thus, the VT can be assessed during the ISWT using a simple heart monitor. The ISWT may be a useful tool to assess exercise capacity and prescribe walking programs.

Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds

“…The present data are consistent with previous studies that found a significant, strong correlation between GET and HRVT within maximal CPET (11,14-16). In fact, our data showed that SD1 stabilization occurred at intensities corresponding to ∼52, 53, and 56% ${\dot{\text{V}}\text{O}}_{2\text{\hspace{0.17em}peak}}$ for cycling, walking, and running CPETs, which in turn are in agreement with the findings of previous studies that verified a progressive decrease followed by a stabilization of SD1 until ∼50-66% ${\dot{\text{V}}\text{O}}_{2\text{\hspace{0.17em}peak}}$ (11,17,19).…”

“…Furthermore, this method of analysis was chosen because it uses the same type of visual technique that was applied to determine GET (see Figure 1), being relatively simple to use and understand (32). Previous studies have adopted the SD1 as a criterion for determining the HRVT (14-17), because this index seems to be related to parasympathetic activity and the HRVT assessment has been mainly attributed to vagal withdrawal (11). …”

“…Previous maximal CPET studies have found a significant, strong correlation between GET and HRVT using cycle ergometry (11,16,18,19), treadmill running (20), walking (14), and track running (13). However, no study has directly investigated the extent to which the exercise modality affects the relationship between GET and HRVT.…”

Equações de referência para os testes de caminhada de campo em adultos saudáveis

“…(24) However, on the 6MWT, the pace is controlled by the subject and an aerobic steady state is achieved. (25) This suggests that the exercise intensity is at or below the lactate threshold in most cases, which results in a lower demand for glycolytic muscle fiber recruitment.…”

Determination of Lactate Thresholds in Maximal Running Test by Heart Rate Variability Data Set

“…The significant vagal withdrawal during incremental exercises has been well documented in the literature using time domain HRV analysis (4,18,23 (4) which used similar visual analysis to identify the vagal withdrawal, that is the point at which the HRV showed no further decrease. However, it is important to note that in contrast to the present study which used a treadmill running incremental test, Karapetian et al (4) used a cycle ergometer, thus limiting deeper comparisons as the values were expressed as power output (watts) instead of speed (km.h -1 ).…”