How much cardio should we be doing in a span of a week? How about a day? Are you undertraining or overtraining? It is tough to give a definite answer because cardiovascular endurance will vary. First off, lets define cardiorespiratory activity as any type of steady-state (or rhythmic) motion that burns calories. The American Heart Association recommends at least 30 minutes of moderate-intensity aerobic activity at least 5 days per week for a total of 150 minutes, OR at least 25 minutes of aerobic activity at least 3 days per week for a total of 75 minutes AND moderate to high-intensity muscle strengthening activity (i.e. weightlifting) at least 2 days per week for additional health benefits. The AHA recommends an average of 40 minutes of moderate aerobic activity 3 or 4 times per week. Bottom line, something is always better than nothing!