Effects of exercise intensity at and around peak stroke volume on cardiovascular drift

The purpose of this study was to evaluate the effects of workloads corresponding to peak stroke volume (P@SVpeak), it's 10% above and 10% below (P@SVpeak%90 and P@SVpeak%110) on cardiyovascular drift (CV-Drift). 6 moderate to well-trained cyclists were participated in this study (VO2max: 63.2±5.21ml/min-1/kg-1; age: 21.7±2.42 year; height: 176.8±5.3 cm, body mass: 69.1±5.8 kg; BMI: 22.1±1.3; body fat percentage: 8.9±1.9%). Individual peak SV levels (SVpeak) of participants were determined at cycling workloads ranged from 40% to 100% of VO2max by using nitrous-oxide rebreathing (N2ORB) method. 30-min constant-load and continuous bouts of exercises were performed by P@SVpeak90%, P@SVpeak, and P@SVpeak110%. CV-Drift was analyzed by cardiac output (Qc) measurements taken at 6th, 9th, 12th, 15th, 20th, 25th and 30th minutes of exercise bouts. Significant differences in heart rate (HR) increase and stroke volume (SV) decrease between 6th and 9-30th minutes accepted as time of inception for CV-Drift. CV-Drift observed during all cycling intensities. Drops in SVs were significant in P@SVpeak%90 (from 143.5 ml at 6th minute to 136.7 ml at 9th; p<0.05) in P@SVpeak (from 148.4 ml at 6th minute to 142.7 ml at 15th; p<0.05) and in P@SVpeak%110 (from 143.6 ml at 6th minute to 138 ml at 30th; p<0.05). At time of CV-Drift inception, HR was significantly increased (p˂0.05), while Qc was remained stabile during all exercise interventions (p>0.05). Mean SV response to cycling with P@SVpeak was higher than P@SVpeak%90 (p<0.05) and P@SVpeak%110 (p<0.05). In conclusion, CV-Drift pattern was changed as long as exercise intensity deviated from the workload corresponding to SVpeak. Keywords: Cardiac output, cardiovascular drift, stroke volume, heart rate