Mechanical Efficiency Is Lower After Cycling Compared To After Running In Trained Triathletes

Triathlon involves swimming, cycling, and running. PURPOSE: To examine whether a 40-km cycling bout alters running economy (RE) and mechanical efficiency of running (ME) in trained triathletes. METHODS: Eight competitive triathletes (7 M, 1 F; 21.0±1.5 yrs; VO2max 59.2±7.6 mL?kg-1?min-1) with a minimum of one-year experience competing in triathlons. Subjects reported to the lab for 3 separate visits. At visit 1, subjects completed the informed consent, a VO2max test, anthropometric measures, and baseline performance testing [isometric squat (MVC) and countermovement jump (CMJ)]. During the 2nd visit, RE and ME were measured after subjects completed a 5-km treadmill run (R5K). For visit 3, RE and ME were measured after subjects completed 40-km of cycling (C40K). MVC, CMJ, and muscle glycogen values were measured before and after the exercise bout on visits 2 and 3. RESULTS: ME after C40K was significantly lower than ME after R5K (C40K: 48.4±5.7%, R5K: 53.7±3.5%; p=0.004). RE, blood lactate, respiratory exchange ratio, work, glycogen, CMJ, or MVC were not statistically different between C40K and R5K. CONCLUSION: The lower ME in running observed following cycling might be due to the combined effect of slightly higher blood lactate and RER values, and slightly lower external mechanical work performed.