The latest study in the Journal of Strength and Conditioning Research finds that indoor cycling makes your run stronger and longer. Runners who did three weekly HIIT cycling workouts (alternating intense bursts of speed with resistance followed by measured recovery) along with 25 miles of running, improved within two weeks. Those who followed this routine trimmed their 3K time by up to 7 percent as well as boosted their endurance and power. Researchers say that HIIT cycling helps you push harder than you would by just running more. And, added bonus, indoor cycling HIIT classes reduce the pounding on your joints and body.