Article Text
Abstract
Objective To establish the time-course recovery of autonomic function following acute exercise through heart rate variability (HRV) and cardiac baroreceptor sensitivity (BRS) metrics.
Design Randomized crossover study design.
Setting Controlled lab environment with university students.
Participants A convenience sample of seven male and two female participants (age: 26 ± 5 years, BMI: 25 ± 4 kg/cm2).
Interventions Three conditions were conducted: 45-minutes of moderate-intensity continuous training (MICT) at ~50–60% heart-rate reserve; 25-minutes high-intensity intervals (HIIT) at ~85–90% heart-rate reserve (ten, one-minute intervals); 30-minute controlled rest condition.
Outcome Measures Short-term (5-minutes) HRV and cardiac BRS were collected while participants stood in an upright orthostatic position. Spontaneous HRV metrics were indexed within time, frequency, and non-linearity domains; whereas, cardiac BRS was quantified through the low frequency (LF) gain metric. These indices of autonomic function were quantified at baseline, and zero, one, two, four, six, and eight hours following the three aforementioned conditions.
Main Results Spontaneous HRV metrics and cardiac BRS LF gain were only altered immediately (hour zero) following both exercise conditions within the time domain (all p<0.05). In contrast frequency domain metrics were unaffected following exercise (all p>0.10). Lastly, all HRV and cardiac BRS parameters were comparable across the control condition (p>0.280).
Conclusions These findings demonstrate several key markers of autonomic function are altered for a one hour period following an acute bout of exercise. Therefore future field-based sport-related concussion investigations examining these metrics will need to be aware of this time course when quantifying alterations immediately following a concussion.