Cardiac output and performance during a marathon race in middle-aged recreational runners.

PURPOSE: Despite the increasing popularity of marathon running, there are no data on the responses of stroke volume (SV) and cardiac output (CO) to exercise in this context. We sought to establish whether marathon performance is associated with the ability to sustain high fractional use of maximal SV and CO (i.e, cardiac endurance) and/or CO, per meter (i.e., cardiac cost). METHODS: We measured the SV, heart rate (HR), CO, and running speed of 14 recreational runners in an incremental, maximal laboratory test and then during a real marathon race (mean performance: 3 hr 30 min ± 45 min). RESULTS: Our data revealed that HR, SV and CO were all in a high but submaximal steady state during the marathon (87.0 ± 1.6%, 77.2 ± 2.6%, and 68.7 ± 2.8% of maximal values, respectively). Marathon performance was inversely correlated with an upward drift in the CO/speed ratio (mL of CO × m(-1)) (r = -0.65, P < 0.01) and positively correlated with the runner's ability to complete the race at a high percentage of the speed at maximal SV (r = 0.83, P < 0.0002). CONCLUSION: Our results showed that marathon performance is inversely correlated with cardiac cost and positively correlated with cardiac endurance. The CO response could be a benchmark for race performance in recreational marathon runners.

A new incremental test for VO2max accurate measurement by increasing VO2max plateau duration, allowing the investigation of its limiting factors.

The purpose of this study was to (1) validate a new exercise protocol for accurate measurement of VO(2max) by obtention of a VO(2max) plateau for all subjects fit and unfit (2) test the hypothesis that VO(2max) plateau duration is not correlated with VO(2max) and (3) verify that limiting factors of VO(2max) plateau duration are different from those of VO(2max) amplitude. Therefore, 14 subjects performed two incremental cycling tests: (1) a classical incremental test (CIT) to determine VO(2max), the power at VO(2max) (PVO(2max)) and at the lactate threshold (PLT) (2) a new incremental test (NIT) in which the power was decreased just after the subject reached VO(2max). During both protocols, heart rate, stroke volume, cardiac output, the arterio-venous difference and the oxygen blood saturation were recorded. The results showed that, with the NIT, subject could maintain a long VO(2max) plateau (6 ± 3 min), even those who could not reach VO(2max) plateau at the end of CIT (n = 5). The VO(2max) plateau duration was not correlated with VO(2max) amplitude which was correlated with the power at SV(max) (r = 0.888, p < 0.001). The VO(2max) plateau duration was correlated with the power decrease (W/s) during the VO(2max) plateau (r = -0.72, p = 0.003) but not with cardiac-related factors nor with PVO(2max). In conclusion, these experiments showed that it was possible to get a long VO(2max) plateau at the end of NIT whatever the individual VO(2max) amplitude was. The limiting factor of VO(2max) duration was the power output.