Interlink Between Physiological and Biomechanical Changes in the Swim-to-Cycle Transition in Triathlon Events: A Narrative Review

Abstract

Triathlon is a multisport composed of swim, cycle, and run segments and two transition periods. The swim-to-cycle transition is considered a critical period for the change in body position and the modifications in physiological (heart rate, VO₂, lactate) and biomechanical parameters (cycling power and cadence, swimming stroke rate). Therefore, the aim of this review was to summarize the current evidence regarding the physiological and biomechanical changes and their interlink during the swim-to-cycle transition hinting at practical recommendations for coaches and athletes. The influence of the swim segment on cycle one is more evident for short-distance events. Greater modifications occur in athletes of lower level. The modulation of intensity during the swim segment affects the changes in the physiological parameters (heart rate, blood lactate, core temperature), with a concomitant influence on cycling gross efficiency. However, gross efficiency could be preserved by wearing a wetsuit or by swimming in a drafting position. A higher swim leg frequency during the last meters of the segment induces a higher cadence during the cycle segment. Training should be directed to the maintenance of a swimming intensity around 80-90% of a previous maximal swim test and with the use of a positive pacing strategy. When athletes are intended to train consecutively only swim and cycle segments, for an optimal muscle activation during cycling, triathletes could adopt a lower cadence (about 60-70% of their typical cadence), although an optimal pedaling cadence depends on the level and type of athlete. Future research should be focused on the combined measurements of physiological and biomechanical parameters using an intervention study design to evaluate training adaptations on swim kick rate and their effects on cycling performance. Coaches and athletes could benefit from the understanding of the physiological and biomechanical changes occurring during the swim-to-cycle transition to optimize the overall triathlon performance.

Keywords: Gross efficiency; Pacing strategy; Pedal cadence; Responses; Swimming intensity.

Fig. 1

Summary of physiological and biomechanical changes according to race distance and athlete level. Swim segment influences the subsequent cycle one eliciting both physiological and biomechanical changes, which may vary according to race distance and athlete level. The ring charts are nonquantitative interpretations of variables (race distance and athlete level) triggering greater or smaller physiological and biomechanical changes. The colors and size of ring sections are qualitative examples to visually explain the physiological and biomechanical changes during different race distances and according to the athlete level. The top ring chart shows that greater modifications (red, orange, and gray sections) occur in short distances (MTR, SD, and OD), whereas longer distances (HD/FD) elicit fewer physiological and biomechanical changes (yellow sections). The bottom ring chart shows that physiological and biomechanical changes are more evident in novice athletes (green segment) compared to professional athletes (blue segment). HD Half distance; FD Full distance; MTR Mixed-team relay; OD Olympic distance; SD Sprint distance

Fig. 2

Influence of swim segment on cycle one concerning physiological and biomechanical changes. RPE rate of perceived exertion; T1 swim-to-cycle transition; VO₂ oxygen uptake kinetics; ↓: reduction; ↑: increase