Intra-Individual Variation of HRV during Orthostatic Challenge in Elite Male Field Hockey Players

The purpose of this study was to examine the intra-individual variation of heart rate variability (HRV) and heart rate using an orthostatic challenge in elite male athletes during a training camp. Heart rate (variability) was measured upon waking. Log-transformed HRV metrics were evaluated in three segments (first min discarded for stabilization): 0–3 min supine, 3–6 min supine, and standing. Heart rate was assessed while supine, 15 s after...