Expense of Time

It can be challenging to accomplish anything significant in a short amount of time, as you will usually not even begin to burn a significant amount of fat and calories until you have completed at least 10 to 20 minutes of exercise. The Centers for Disease Control and Prevention recommends an average of 150 minutes of moderate-intensity exercise per week with two sessions of resistance training to improve your overall health. You can divide these minutes into small, manageable sessions throughout the week.

Risk of Injury

Long, intense and frequent exercise of the same kind may lead to repetitive use injury. However, as you continue to exercise, you gain increased strength and endurance, which can protect you from injury as well. A longer exercise routine better prepares you to participate in sports, extreme fitness activities and extended events such as a marathon. Although you are less likely to develop repetitive injuries if you work out for shorter sessions, you are more likely to contract an acute injury from a less conditioned body associated with shorter exercise routines.

Effect on Mood

Increased endorphin release accompanies longer, more intense workouts such as heavy weight training or long-distance running. Because of this you may see a smaller improvement in your mood after a short routine than after a lengthy one. Sticking to your exercise routine, whether short or long, can help to build your self-esteem and reduce anxiety related to long-term health concerns. Starting with a shorter routine that you can successfully complete over the long term can help you build your confidence as an athlete and help you transition to a longer daily exercise program.

The Science and Analysis

Almost any amount of exercise is better than no exercise, as the long-term health risks of a sedentary life include increased weight gain, increased risk of heart attack and stroke. And a study in the "PLOS ONE" journal from May 2013 found that overweight men who exercised at a vigorous level for only four minutes at least three times per week showed some of the same cardiovascular improvement as those who exercised for 16 minutes three times per week -- though those who exercised longer reached lower fat and cholesterol levels. Select a workout schedule that realistically fits into your life, and vary your activities and length from day to day to add variety to your workouts.