The cardiovascular system consists of your heart and blood vessels and is responsible for transporting oxygen and nutrients throughout your body. Physical activity strengthens your cardiovascular system — "Some is good; more is better," according to the "Guidelines for Prescribing Exercise" set in 2010 by the American College of Sports Medicine. To improve your cardiovascular fitness, the ACSM recommends increasing your exercise duration, increasing your exercise intensity and incorporating interval training into your workout routine.
Cardiovascular fitness is related to aerobic capacity. Aerobic capacity is the maximum amount of oxygen you can use while engaging in an activity. During exercise, the demands on your cardiovascular system increase as your muscles require more oxygen in order to maintain their output. Your cardiovascular system responds by increasing your heart rate, blood pressure and redirecting blood flow in order to maximize the amount of oxygen delivered to your muscles. The capacity of the cardiovascular system to regulate blood flow and supply oxygen to working tissues is critical to exercise performance.
Healthy adults should engage in a minimum of 150 minutes of moderate- to vigorous-intensity aerobic exercise each week, according to the U.S. Department of Health and Human Services. For additional and more extensive health benefits, the department recommends you increase your aerobic physical activity to 300 minutes or more per week. The accumulation of the total amount of exercise is more critical to improving fitness than the duration of an individual exercise session. The ACSM suggests that you set a daily minimum goal of 30 minutes of exercise, which may be completed in a single exercise session or during shorter sessions of at least 10 minutes each interspersed throughout your day.
The higher the exercise intensity, the greater cardiovascular benefits, according to a study published in the journal "Medicine and Science in Sport and Exercise" in 2010. Participants engaged in either 20 minutes of sprints or an hour of jogging two to three times per week. While both exercise groups showed improved aerobic capacity after 12 weeks in the exercise program, the sprinters showed a two-fold increase in fitness compared with the joggers. Conversely, exercise below a minimum intensity will not challenge your body sufficiently to increase cardiovascular fitness. The ACSM suggests vigorous-intensity activities to optimize cardiovascular fitness. The intensity of any exercise is relative to your level of fitness, but a good example of vigorous-intensity exercise is running at a 10-minute-per-mile pace, or 6 miles an hour, according to the U.S. Department of Health and Human Services.
Interval training consists of alternating short bursts of high-intensity exercise and lower-intensity rest periods. An interval-training routine, for example, would alternate between a 15-second sprint and a 15-second jog and then repeat for a total of 25 to 30 intervals. High-intensity interval training is significantly more effective at increasing aerobic capacity than prolonged continuous exercise, although both can improve cardiovascular fitness, according to a study published in 2006 in the "Medicine and Science in Sports and Exercise." Researchers found that sprint training three times per week for eight weeks increased participants' aerobic capacity to a greater degree than 45 minutes of slow running over the same time period. A combination of prolonged, low-intensity and short, high-intensity training is optimal to improve cardiovascular fitness and overall exercise performance.