Any exercise that you sustain over a period of time without rest counts as continuous exercise. Because high-intensity intervals and resistance training are higher impact, steady-state cardio represents one of the most common forms of continuous exercise. Overall, continuous cardio exercises can help you burn calories and improve your health without pushing your body to its limits.
Although a long bout of aerobic exercise, such as jogging a few miles, constitutes a continuous workout, there is no specific time requirement for a continuous exercise workout. You can run at 50 percent of your maximum heart rate for an extended period of time, or you can run above 90 percent of your maximum heart rate for a few minutes. Generally, a longer bout of exercise where oxygen comprises your main energy source qualifies as continuous. (Ref. 1)
The specific benefits you get out of a continuous workout depend on the exercise you do, but with most continuous workouts including aerobic exercises, the benefits will be similar across the board. Steady-state cardio exercise improves endurance, burns calories and helps to manage chronic conditions such as high blood pressure and cholesterol. Ancillary benefits from continuous exercise include stress relief and mood improvement. (Ref. 2)
Continuous vs. Accumulated
A 2009 review published in the "Journal of Sports Medicine" comparing continuous versus accumulated bouts of exercise found no significant difference between the two in terms of overall health benefits. The review compiled reports from 16 different fitness studies, most of which reported no difference in cardiovascular improvement between continues and accumulated exercises. Essentially, the frequency of exercise per day isn't as important as the total duration of exercise. (Ref. 3)
You can measure you rate of exertion during exercise by keeping an eye on your heart rate. To find your heart rate, take your pulse on the inside of your wrist for six seconds and then multiply that number by 10. You can estimate your maximum heart rate by subtracting your age from 220. According to the Centers for Disease Control and Prevention, most people are fairly accurate when it comes to assessing their own rates of exertion. If you feel like you're overdoing it, you probably are. (Ref. 4-5)