Swap stretching for a dynamic warm-up. Compound exercises recruit multiple muscle groups and two or more joints at once. This is opposed to isolation exercises, which focus on a muscle group (such as bicep pushups). Because they help you do more in less time, they're great for increasing overall muscle mass and they also burn more calories because they require more energy production.
Compound exercises can be individual movements in which several groups work at the same time (such as lunges and squats), or they can consist of two movements joined together (such as bicep flexions or shoulder pressures). Remember that these high-intensity workouts aren't for people who are just starting out. You should build a base of resistance before doing high-intensity cardio and start the weights with lighter weights, emphasizing good form. You can easily find dumbbells, TRX bands, kettlebells, weighted medicine balls and sliding discs at every gym (or on the Internet if you like to work out at home), and they increase the intensity of standard movements, such as push-ups, squats and sit-ups.
Trying a new training class, adding more weight or repetitions, or changing the order of the workout can be great ways to change it. Cheer yourself up on your way to the gym and during your workout with songs that make you feel strong, powerful and that you can do anything. Here are eight quick tips I've learned to create an efficient workout and make the most of your time at the gym. Foaming before exercising (and when you have free time) is a good habit to make every gym session more effective.