Background and Aims: Kidney transplant recipients (KTR) have reduced arterial compliance and aerobic endurance. A limitation of prior studies examining cardiovascular fitness and function in KTR was the primary focus on male KTR. Furthermore, the effect that kidney transplantation has on pulmonary oxygen (VO₂p) and heart rate (HR) ON- and OFF-kinetics during the 6-minute walk test (6-MWT) has not been examined. The aim of this study was to examine arterial compliance, Vo₂p and HR ON- and OFF-kinetics during the 6-MWT in female KTR.

Methods and Materials: Ten female KTR (mean +/- SD age: 44 +/- 8 years) recruited from the 2006 Canadian Transplant Games and 10 healthy age and activity matched controls (CT) participated in this study. Large (LAC) and small (SAC) arterial compliance was assessed using applanation tonometry. Heart rate and expired gas analysis were measured during the 6-MWT with an ambulatory metabolic gas measurement system. The greatest HR and VO₂ achieved during the 6-MWT was used to define the peak score. Further, HR and VO_2p ON- and OFF-kinetics were quantified using nonlinear regression. Comparison between groups was performed using analysis of variance, significance was determined at P < .05.

Results:Figure to the right illustrates group mean VO_2p responses. KTR had a significantly shorter 6-MWT distance (CT: 655 +/- 100 m vs KTR: 574 +/- 61 m), slower HR ON-kinetics (CT: 33 +/- 14 s vs KTR: 51 +/- 17 s), VO_2p ON-kinetics (CT: 27 +/- 8 s vs KTR: 46 +/- 21 s), and VO_2p OFF-kinetics (CT: 47 +/- 9 s vs 63 +/- 13 s) compared to CT. No significant difference was found between groups for SAC (CT: 6.7 +/- 2.2 mL/mmHg x 100 vs KTR: 6.9 +/- 3.5 mL/mmHg x 100), LAC (CT: 14.4 +/- 2.6 mL/mmHg x 10 vs KTR: 16.5 +/- 4.7 mL/mmHg x 10), HR OFF-kinetics (CT: 41 +/- 20 s vs KTR: 47 +/- 18 s), peak HR (CT: 130 +/- 18 bpm vs KTR: 115 +/- 12 bpm) and peak VO_2p (CT: 22 +/- 8 mL kg min vs KTR: 18 +/- 4 mL kg min) during the 6-MWT.

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Conclusions. Active female KTR have normal resting small and large arterial compliance, and can achieve a normal peak VO_2p and HR during the 6-MWT. However, the time to reach a steady state VO_2p and HR remains 41% and 35% slower, respectively, in female KTR compared to CT. Moreover, the prolonged metabolic recovery period that occurs in female KTR is not associated with an elevated postexercise HR. A functional consequence of the impaired VO_2p and HR kinetics in female KTR is that it results in a lower (12%) distance walked in 6 minutes.