High-intensity interval training (HIIT) has the advantage of training effect on overall health in a short period due to its time efficiency. However, there is a lack of studies examining the differences of cardiovascular response following HIIT and MI...
High-intensity interval training (HIIT) has the advantage of training effect on overall health in a short period due to its time efficiency. However, there is a lack of studies examining the differences of cardiovascular response following HIIT and MICT. This study was examined to compare the effect of HIIT and MICT on heart rate variability, blood pressure, and vascular compliance. This study is a randomized cross-over design. Twenty young women (Age: 19.9 yrs, Body height: 160.9 cm, Body weight: 57.5 kg, Body mass index: 22.1 kg/m2, Fat mass: 13.9 kg, Lean mass: 40.4 kg, Percent body fat: 24.5%) were randomly assigned either HIIT or MICT in a counterbalance manner. HIIT was performed for 20 min at 115-130% Wmax with 20 sec of exercise and 100 sec of active rest. MICT was performed at 60 W (60-75% HRmax) at 58-63 RPM for 40 min. Heart rate variability, blood pressure, and brachial-ankle pulse wave velocity were measured six times at baseline, immediately post-training, post 15 min, 30 min, 45 min, and 60 min. Two-way repeated measure ANOVA was used to analyze the interaction effects between training mode by time. The statistical significance level (α) was set at .05.
Significant interaction effects were found in heart rate (HR: F = 41.92, p < .001), RRI (R-R interval, RRI: F = 14.69 p < .001), SDNN (standard deviation of the mean of qualified N-N interval, SDNN: F = 13.70, p < .001), and RMSSD (the root mean square successive heartbeat interval difference, RMSSD: F = 12.50, p < .001). Significant increase in heart rate was observed after HIIT compared to MICT (p < .01). RRI, SDNN, and RMSSD were decreased significantly after HIIT compared to MICT (p < .001). Significant interaction effects were found in lnLF (natural logarithm of low frequency spectra, lnLF: F = 11.16, p < .001), lnHF (natural logarithm of high frequency spectra, lnHF: F = 30.46, p < .001), and lnLF/HF (natural logarithm of LF/HF ratio, lnLF/HF: F = 10.20, p < .001). Immediately post-training, lnLF and lnHF were significantly decreased after HIIT compared to MICT (p < .05). After HIIT, lnLF/HF was increased significantly compared to MICT (p < .05). There was no significant interaction effects in RbSBP (right brachial systolic blood pressure), RbDBP (right brachial diastolic blood pressure), and RbMAP (right brachial mean arterial pressure). Significant interaction effects were found in RbaPWV (right brachial-ankle pulse wave velocity, RbaPWV: F = 3.03, p < .05), LbaPWV (left brachial-ankle pulse wave velocity, LbaPWV: F = 3.16, p < .05), RABI (right ankle brachial index, RABI: F = 3.06, p < .05), and LABI (left ankle brachial index, LABI: F = 6.90, p < .001). Immediately post-training, RbaPWV was significantly decreased after HIIT(p < .05). However, there was no significant change in RbaPWV after MICT. Although LbaPWV was not significantly changed following HIIT and MICT, this value was lower in the HIIT compared to MICT at immediately post, post 15 and 30 mins (p < .05).
This study suggests that HIIT affects greater recovery time on heart rate variability than MICT. A greater decrease in baPWV was observed following HIIT compared to MICT. In future studies with HIIT, it is recommended to consider the recovery delay when designing the optimal HIIT programs. Moreover, dose-response studies on the training intensity and training volume of HIIT should proceed to effectively improve cardiovascular function.