FRIDAY, Sept. 20, 2019 (HealthDay News) -- Tired of taking the same old cardio class? It's time to explore some of the combination classes being offered at both large gyms and small, more personalized fitness centers. One of the most popular options is the multi-discipline class -- two or more activities woven into the same workout session, designed to keep fitness fun as well as challenge participants and avoid workout ruts. And there are many variations. A very rigorous combination takes the high-calorie burning technique of high-intensity interval training and applies it to strength training moves using only your body weight. By focusing on exercises like lunges and squats and not worrying about grabbing equipment, you can work through the moves quickly. Some creative combo...