Effect of Cycling Cadence on Running in a Triathlon
In doing some checking of the research while I was writing a magazine article on triathlon transitions I came across an interesting French study (1). The scientists wanted to see if there was an effect of bike pedal cadence on a subsequent run performance. Eight experienced triathletes completed three bike-run sessions. In each bike portion they rode at 90% of lactate threshold, which is roughly FTP, for 30 minutes. This would have been an effort similar to or slightly harder than what would be done in an Olympic-distance triathlon. They then quickly transitioned to a run to fatigue at 85% of max velocity, about the pace that would be run in a sprint-distance tri. The variable they manipulated was cadence on the bike. In the last 10 minutes of each 30-minute ride the athletes pedaled at 1) a freely chosen cadence, 2) a cadence 20% higher than #1, and 3) a cadence 20% lower than #1. So, for example, if #1 was 90 rpm then #2 was 108 rpm and #3 was 72 rpm.
What they found was that when pedaling at a cadence 20% lower than freely chosen the time to exhaustion on the run increased by 37% on average over the freely-chosen-cadence performance. Running cadence was unchanged by the cycling cadences. They also found that near the end of the low-cadence cycling bout the stress placed on the athletes' as measured by VO2, heart rate, ventilation rate and lactate accumulation were not significantly different compared with the freely chosen cadence bout. The high-cadence bout fared worse than the other two on all measures including time to exhaustion.
The study was interesting for me because it contradicted a study out of the University of Colorado from a few years ago with which I was familiar (2). Thirteen experienced triathletes completed three bike-run sessions on separate days. In each they rode 30 minutes at a high intensity and then ran a 3200-meter time trial. The only thing that changed was the cadence on the bike. As with the French study they rode one at a freely chosen cadence, a second at a cadence 20% higher than freely chosen and a third at a cadence 20% lower than freely chosen--for the entire 30 minutes (this is different than the French study in which only the last 10 minutes on the bike varied). The Buff researchers found that after cycling at a high cadence (100-110 rpm) the run times were nearly one minute faster on average than with the freely chosen bout. And, besides that, the run cadences were also quicker. Stride lengths and observed biomechanics were unchanged.
So there you have it. Take your pick: pedal at a low cadence before entering T2 or pedal at a high cadence before T2. One of them will improve your run performance. Which one? I wish I could say. I have not come across another study on this topic yet. There may be individual differences which affect the results such as your position on the bike, how steady or variable your bike pacing was, how quickly you transition, etc. If you have a personal solution for this dilemma please feel free to post it.
1. Vercruyssen, F et al. 2005. Cadence selection affects metabolic responses during cycling and subsequent running time to fatigue. Br J Sports Med 39(5):267-72.
2. Gottschall JS et al. 2002. The acute effects of prior cycling cadence on running performance and kinematics. Med Sci Sport Exerc (34(9):1518-22.