What is the fine-grained topic of the following text: A 2011 study at the University of Calgary showed that cyclists who performed a long and intense warmup lasting 50 minutes with intervals up to 95 percent of maximal heart rate put out 6.5 percent less power than when they stuck to a short, 15-minute routine at a low intensity ending in only a single sprint. Only return the topic.
Effects of warm-up length and intensity on cyclist performance