Background: The main purpose of this study was to test the effects of a duathlon competition on running economy. METHODS.
Experimental design: A prospective study.
Setting: University.
Participants: nine male and six female physical education students, which mean (SEM) age was 24.0 (1.3) years.
Measures: Subjects participated in two competitive duathlons: D1 and D2 (5 km running + 16 km cycling + 2 km running). Before D1, an incremental exercise test on the treadmill was performed to determine the V O2max, the running speed at exhaustion (vmax), and the V O2, as well as the running speed (u) attained at the first and second ventilatory threshold (V O2V T1, uV T1, V O2V T2, uV T2). Two days later running economy (RE1) was assessed at four different speeds corresponding to 58, 63, 67 and 71% of the umax. During the following six weeks the subjects trained 4 days a week, running all them 210 km in total. At the end of the training program the incremental exercise test and the duathlon competition were repeated (D2). Two and seven days after the second duathlon running economy was measured again (RE2 and RE3, respectively).
Results: Small, but significant improvements were observed in duathlon performance, V O2max, umax, uV T1, V O2V T2 and uV T2, after training. Two days after D2 the oxygen cost of running was approximately 5% higher than seven days after D2 (p < 0.001). The respiratory exchange ratio increased by approximately 0.04 units between RE2 and RE3 (p < 0.001). However, the increase in fat oxidation in RE2 only accounted for approximately 20% of the extra oxygen cost of running (RE2 vs RE3). No significant differences across tests were observed for ventilation (V E), heart rate, V CO2 and V E/V CO2.
Conclusions: This study shows that two days after a duathlon competition running economy is impaired, however, seven days after the competition the oxygen cost of running is restored.