The effects of high-intesity interval training on autonomic function in elderly people with increased cardiovascular risk

Objectives
Heart rate variability (HRV) is reduced in elderly, overweight patients and is an independent risk factor for cardiovascular diseases (CVD) and mortality. In contrast, High Intensity Interval Training (HIIT) has positive effects on HRV and reduces the risk of CVD. The aim of this study was to investigate the relationship between the benefits of HIIT and its effects on HRV in overweight, sedentary subjects aged 50-80 years with a current CVD risk factor.
Methods
Short-term HRV was measured through a 12-point electrocardiograph for 20 minutes, divided into 4 segments. The intervention group (INT) performed the HIIT over 3 months, 3 trainings each week at 80-90% of their HFMAX. The control group (CON) was asked to refrain from any major lifestyle changes, i.e. diet, smoking habits or regular exercise. Both groups were tested in a two-week span on three non-consecutive days prior and after the intervention.
Results
No significant improvement in HRV could be found for the INT (n=38), compared to the CON (n=33). VO2MAX significantly improved (26.25 ± 3.84 to 28.41 ± 3.99 ml/kg/min) in the INT, while it slightly decreased (26.01 ± 4.99 to 25.07 ± 4.11 ml/kg/min) in CON (p<0.01). Both groups lowered their BMI scores and HR at rest.
Conclusions
The present study reveals that a three month HIIT intervention may not be suitable to improved short-term HRV parameters but can be useful to improve fitness parameters such as VO2MAX for elderly sedentary subjects with present cardiovascular risk factors.