A 2003 study estimated that nearly 75 per cent of all long-course triathletes will sustain an injury and, according to another 2005 study, up to 73 per cent of those injuries will be related to running. To explore this issue, a group of researchers, recently published in the Journal of Science and Medicine in Sport, analysed how riding in the aerodynamic position affected an ath- lete’s running form.
“When you first start running off the bike, you feel sea-legged, uncoordinated and as if you are not running at your normal pace,” says Nicole Rendos, a Ph.D. candidate at the University of Miami and the lead researcher on the study. Rendos and her team wondered if these feelings were a result of altered biomechanics, and whether or not it affected running performance and the risk of injury.
Subjects: 28 age-group triathletes, 14 with less than two years in triathlon and 14 with greater than two years
Part 1: Subjects ran on a treadmill for 10 minutes at a speed comparable to sprint triathlon pace. They wore 21 reflective markers on specific joints to calculate body angles using 12 cameras.
Part 2: After resting for a few minutes, subjects rode on a spin bike with aerobars for 30 minutes, followed by a 15-minute run (transition time was less than two minutes).
What They Learned: Using three-dimensional cameras, researchers looked at the angles of the hips, knees, pelvis and ankles in the sagittal plane (front to back). “We found that the pelvis is pretty much the main marker–it tilts forward,” Rendos says. “Your hips are continuously flexed on the bike and they never extend past zero degrees, so it causes tightness in the pelvis and hips and results in pelvis tipping. When the pelvis tips forward, you have to extend with your spine to counterbalance the pelvis and stay upright.”
Why This Matters: The increased spine extension and forward pelvic tilt have been shown to lead to slower running speeds as well as lower-back pain and hamstring injuries.
The more experienced triathletes had fewer bio- mechanical implications than the newer triathletes when running off the bike. Studies have shown that 86 per cent of reported in- juries occur in triathletes with two years of experience or less–which could be, in part, related to the lack of experience running off the bike. Experienced triathletes may have the ingrained muscle memory and neuromuscular pat- terns to adapt quicker to normal running form.
In future research, Rendos hopes to do a similar study to investigate muscle activity pat- terns, but have athletes bring in their own bikes, using a CompuTrainer to simulate real riding for 45 minutes.