Objectives: This study examined the influences of the volume of all-out sprint-interval exercise (SIE) on acute post-exercise heart rate variability (HRV) recovery. Methods: HRV recovery following a session of (i) 2 × 30-s SIE (SIE2). (ii) 4 × 30-s SIE (SIE4). and (iii) non-exercising control (CON) were compared in 15 untrained young males. https://balboasurfandsstylers.shop/product-category/big-girls-rashguard/