Time is an issue “preventing” people from working out and being in better shape. The funny thing is, time isn't really the issue at all. When a workout is planned and executed properly, you can achieve great results in very little time. What is really preventing people from working out then, is knowledge to plan the workout properly, and the will-power to workout at the necessary intensity.
An effective workout can be accomplished in 20-30 minutes, including a light warmup. The key is moving quickly, with little rest. Exercises that require multiple muscle groups will be priorities, while exercises specifically for biceps, triceps, calves will take a back seat.
Here are a few ways you can map out your workout to be quick and efficient, while giving you the flexibility to decide what exercises are used, and how often you will workout.
The timed circuit: Choose three or four exercises. Give yourself between 10-15 minutes, and complete as many sets of 10 for each exercise as possible. It is important to move quickly between exercises with little rest. Changing weights will use away valuable time. If you use barbells, start with a weight that is a bit on the light side, as it will feel heavier as you go. Machines and dumbbells work great here. If you have energy left, or want to hit every muscle group, add a second circuit with an additional three or four exercises.
MMA circuits: Regardless if you enjoy the sport or not, MMA fighters are some the strongest and best conditioned athletes in the world. Training like them has many benefits. MMA fights are typically three rounds of five minutes, with 1 minute rest in between. Championship fights are five rounds. Workouts can model fights. Option one is to choose five exercises, and perform each for 1 minute. Repeat this circuit three to five times. Option two is to choose five different exercises for each five minute round.
Timed exercises: Choose 10-15 different exercises. Perform each exercise for one minute, then rest 30 seconds. This will cause a unique burn in the muscles, and challenge you mentally, since most sets don't last near this long. The number of exercises allows you to work every major muscle group. Larger muscle groups such as legs, back, shoulders and chest can be trained with multiple exercises for better development.