Analysis of Fast Fourier Transform Parameters for Heart Rate Variability in Indian Professional Competitive Swimmers During Short-Duration Assessments

Abstract

Background: Heart rate variability (HRV) is a non-invasive marker of autonomic nervous system function and is widely used to assess training adaptation, recovery, and cardiovascular regulation in athletes. Limited data are available regarding frequency-domain HRV parameters among Indian professional competitive swimmers.

Aim: To analyse Fast Fourier Transform (FFT)-derived HRV parameters in Indian professional competitive swimmers during resting and post-workout conditions.

Materials and Methods: This observational study included 45 professional competitive swimmers aged 8–24 years who fulfilled predefined inclusion and exclusion criteria. Five-minute Lead II ECG recordings were obtained at rest and after a one-hour intensive swimming session followed by a 15-minute recovery period. Frequency-domain HRV parameters including Very Low Frequency (VLF), Low Frequency (LF), High Frequency (HF), LF and HF power, and LF/HF ratio were analysed using dedicated HRV analysis software.

Results: VLF and HF frequencies showed minimal reductions following exercise, whereas LF frequency demonstrated a slight increase. LF power increased modestly, while HF power decreased after exercise. The LF/HF ratio increased significantly from 4.44 ± 2.00 at rest to 6.23 ± 2.47 following exercise (p < 0.001), indicating a shift toward sympathetic predominance during the post-workout period.

Conclusion: Frequency-domain HRV analysis demonstrated sympathetic predominance in Indian professional competitive swimmers at rest and after intensive exercise. Elevated LF power and LF/HF ratio may serve as useful indicators of autonomic balance and could assist in identifying inadequate recovery or possible overtraining when interpreted alongside clinical assessment and training history. Larger longitudinal studies are recommended to establish normative values for Indian athletes.