Effects of Aerobic Exercise on Heart Rate Variability and C-Reactive Protein in Middle-Aged Adults With Normal Weight...

Aerobic exercise (AE) can improve heart rate variability (HRV) and reduce inflammation. Whether body mass index (BMI) affects physiological responses to AE remains unclear. This pilot study aimed to compare the effects of a 16-week AE on HRV and C-reactive protein (CRP) in normal weight (18.5 ≤ BMI < 24) and overweight/obesity (BMI ≥ 24) middle-aged adults. A quasi-experimental design with purposive sampling was employed to recruit middle-aged adults, who were categorized into normal weight (n = 26) and overweight/obesity (n = 25) groups. All participants engaged in at least moderate-intensity AE three times per week for 16 weeks. HRV parameters and CRP were evaluated at baseline and after intervention. The results demonstrated that the overweight/obesity group experienced a significant decrease in resting heart rate (Β = -4.35, p = 0.049) but a significant increase in CRP (Β = 1.22, p = 0.045) compared to the normal weight group. Both groups exhibited similar trajectories in HRV parameters during rest, warm-up, exercise, and cool-down phases over the 16-week period. However, HRV parameters associated with parasympathetic nervous system activity fluctuated more prominently from rest to exercise in the normal weight group than in the overweight/obesity group. Individuals with overweight/obesity appeared to exhibit less favorable parasympathetic adaptation during exercise. Intense physical activity was associated with inflammatory responses in these individuals. Health professionals may monitor HRV and inflammation to ensure safe exercise and guide individuals in developing customized regimens. Trial Registration: NCT05949710.