The Effects of Bicycle Geometry on Sprint Triathlon Running Performance

Abstract

Previous research has shown that riding with a steeper (81°) than normal (73°) bicycle seat tube angle (STA) can improve subsequent run performance during Olympic distance triathlon that involve a 1500 m swim, 40 km cycle and 10 km run. However, such races often utilise pacing strategies during the run phase that may have influenced previous findings. Conversely, Sprint distance triathlons (750 m swim, 20 km cycle and 5 km run) are generally performed at a higher intensity, both during the cycle and run legs. Few studies have focused on Sprint triathlons, therefore, the purpose of this study was to investigate the effect cycling with different STA’s had on subsequent sprint triathlon running performance. Ten trained amateur male triathletes (34.8 ± 10.9 years), completed two 20 km time trials on a cycle ergometer, one with a STA of 73° and one with a STA of 81°. Both conditions were followed immediately by a 5 km treadmill based running time trial and were completed as fast as possible. Time (min:s), heart rate (Beats.min-1), oxygen consumption (ml.kg.min-1) and rate of perceived exertion (RPE) were recorded for both run and cycle legs. Additionally, during the cycle leg, mean power output (W), mean cadence (rpm) and mean velocity (km.h-1) were recorded. For the run leg, velocity (m.s-1), stride length (SL, in m) and stride frequency (SF, in Hz) were additionally recorded. Running time improved significantly following cycling with the 81° STA compared to 73° STA (27:10 ± 3:09 vs. 27:59 ± 3:18 min:s respectively; p=.006; ES=0.25), along with running velocity (3.13 ± 0.37 vs. 3.04 ± 0.37 m.s-1 for 81° and 73° respectively; p=.007; ES=0.24). Stride length also increased significantly following the cycle with the 81° STA (2.20 ± 0.26 vs. 2.12 ± 0.27 m for 81° and 73° respectively; p=.007; ES=0.30). Overall cycle+run time was also significantly reduced in the 81° condition (63:31 ± 6:08 vs. 64:23 ± 5:10 min:s for
81° and 73° respectively; p=.042; ES=0.15). These results suggest that cycling on a bicycle with a steeper STA improves subsequent running and overall performance during a simulated sprint triathlon, possibly due to changes in lower limb biomechanics.