if u actually READ VJB,itll say exactly
You can do low intensity cardiovascular exercise at around 60% of your maximum heart rate for 20-30 minutes 3-4 days per week.To find 60% of your maximum heart rate subtract your age from 220 and multiply that by 60%.If you're 20 years old you'll get 120. That means you can do any cardiovascular exercise as long as your heart rate stays below 120.

You can also do short interval sprints (10-30 seconds per sprint) at 60-70% of your top speed. For example you could do 3 sets of 5 x 100 yard sprints at 60% of your top speed. Rest 30-45 seconds between sprints and 2-3 minutes between sets. If you really need the extra activity you might to 1-2 days of low intensity cardiovascular exercise and 1-2 days of intervals.

Straight from vjb.