Triathlon: What makes the transition from cycling to running difficult?

The “heavy” legs that many triathletes experience when transitioning from cycling to running is a phenomenon that has been described and concerns the sports community in question. Triathletes are required to perform a variety of different movements while maintaining a high level of intensity during the swim, bike and run of the race1. ¹The order of the events can change, but usually swimming comes first and is followed by cycling and running or running and cycling. Success depends on the individual’s ability to perform these movements efficiently and for a sustained period of time. Elite triathletes are usually able to maintain high running capacity after cycling, while young triathletes or athletes of different levels may experience changes in running performance after cycling.This effect is particularly evident during the first minutes of running after cycling2.².

It is clear that running after cycling induces variable biomechanical and physiological responses that lead to reduced performance ^1,2. Although the mechanisms responsible for this phenomenon have not been fully elucidated, a significantly lower mechanical efficiency, but also a higher anaerobic energy expenditure, has been observed.

In studies of the post-cycling decline in running performance, running economy and mechanical performance were tested during simulated race conditions in triathletes. Running economy [running economy (RE)] correlates with running speed and performance in endurance events and is essentially oxygen consumption at a given running pace.

The data suggest that triathletes who switch from cycling to running experience a higher level of anaerobic metabolism, as indicated by increased blood lactate levels.

How is this phenomenon caused?

1. Initially, it is reasonable that the previous exercise causes fatigue in the motor muscle groups and glycogen depletion, which requires a greater energy expenditure to compensate.
2. It is also argued that due to an involuntary interference effect caused by previous exercise, the individual continues to follow a movement pattern after performing a specific rhythmic activity for a long period of time. In other words, the athlete’s neuromuscular system adapts to the cycling motion and is delayed in making the transition to the optimal running motion.
3. In addition, metabolic fatigue and metabolite accumulation caused by both aerobic and anaerobic pathways during strenuous cycling bouts could contribute to the reduced muscle strength observed after cycling.
4. Preceding cycling affects some athletes’ perception of effort levels during the transition to running.

A possible technique to mitigate the decline in running performance after cycling is to reduce the overall cycling intensity slightly until the run transition (last 1–2 km of cycling). This may allow anaerobic metabolism, and thus blood lactate levels, to drop enough to provide a smoother metabolic transition into the running portion of the triathlon.

Based on the available scientific information, the basis for future research is provided to examine different training interventions. With an eye on preventing a decline in mechanical performance during running after prolonged cycling in triathletes, the way is paved for minimizing transition stages and achieving optimal performance in each segment of the triathlon.

1. tewart JA, Merritt EK, Lidstone DE, McBride JM, Zwetsloot KA. Prolonged cycling lowers subsequent running mechanical efficiency in collegiate triathletes. BMC Sports Sci Med Rehabil. 2022 Aug 1;14(1):149. doi: 10.1186/s13102-022-00543-w. PMID: 35915467; PMCID: PMC9344700.
2. du Plessis C, Blazevich AJ, Abbiss C, Wilkie JC. Running economy and effort after cycling: Effect of methodological choices. J Sports Sci. 2020 May;38(10):1105-1114. doi: 10.1080/02640414.2020.1742962. Epub 2020 Mar 21. PMID: 32202206.

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