Influence of exercise-induced fatigue on cardiovascular responses to repeated muscle stretching

The aim of this study was to assess the dynamic interaction between cardiac cycle duration and pulse wave amplitude during repeated stretching exercises performed before training, after warm-up, and after a 60-minute strength training session. Ten healthy physically active male participants completed a repeated-measures experimental protocol. Cardiovascular signals were recorded in a seated position at three experimental stages: before training, after warm-up, and after training. At each stage, participants first remained seated at rest, after which they performed four bilateral static stretching repetitions, each consisting of 30 s of stretching for each lower limb and separated by 30 s recovery intervals. The interaction between cardiac cycle duration and pulse wave amplitude was evaluated using algebraic data cointegration. The discriminant index D s k was calculated at 10 s intervals, where lower D s k values indicated stronger interaction between the analysed cardiovascular signals. Before training, D s k values demonstrated a phase-dependent decrease-increase pattern, with reductions during stretching repetitions and increases during recovery periods. After warm-up, a similar response was observed during the first two repetitions, but D s k values remained lower during the latter part of the protocol. After the 60-minute strength training session, D s k values decreased at the beginning of the first stretching repetition and remained low throughout most of the remaining protocol. These findings indicate that repeated stretching exercises strengthen the interaction between cardiac cycle duration and pulse wave amplitude, and that this enhanced interaction persists after stretching, particularly under fatigue conditions. This response suggests cumulative effects of exercise and stretching on vago-sympathetic regulation and ventricular–vascular interaction.