Cardiac autonomic and hemodynamic responses to two-stage cycling and post-exercise recovery with partial blood flow restriction in young males

PURPOSE: This study compared acute cardiovascular and cardiac autonomic responses during graded (two-stage) aerobic cycling and subsequent recovery performed with and without partial blood flow restriction (BFR). METHODS: Fifteen young males completed two sessions in a crossover design (control vs. bilateral thigh BFR). Each session included rest, 5 min of cycling at 40% maximal power output (Pmax), 5 min at 60% Pmax, and 10 min of recovery; BFR was released immediately at exercise cessation. ECG and arterial blood pressure were recorded. RR interval, mean arterial blood pressure (MBP), HRV (lnRMSSD, lnSDNN, HF, LF, LF/HF), and composite indices of cardiac sympathetic and parasympathetic activity (SNS, PNS) were derived from 3-min segments at rest, exercise, and recovery. Heart rate recovery at 30, 60, and 120 s after exercise cessation (HRR30, HRR60, HRR120) was calculated. Two-way repeated-measures ANOVA tested condition, time, and interaction. RESULTS: Time × condition interactions were observed for RR interval (p=0.015) and MBP (p=0.003), indicating altered hemodynamic kinetics under BFR, primarily during recovery. HRV indices showed no time × condition interactions; however, BFR produced lower lnRMSSD, lnSDNN, HF, and PNS and higher SNS than control (all p<0.05), whereas LF and LF/HF were unchanged. HRR30 (p=0.040), HRR60 (p<0.001), and HRR120 (p=0.010) were attenuated under BFR. CONCLUSIONS: BFR modifies cardiovascular regulation during two-stage cycling and recovery and induces sustained autonomic shifts toward reduced parasympathetic and increased sympathetic modulation, largely independent of exercise intensity. Altered recovery kinetics following cuff release highlight the importance of careful monitoring during the recovery phase when applying BFR.