The 60 minute suggestion is based on the National Academy of Sciences recommendation for people who are trying to prevent weight gain, or keep themselves from regaining after weight-loss – not for people who are trying to increase or maintain their cardio-respiratory fitness or health. There’s plenty of research to show that 30 minutes of physical activity a day will help you gain lots of health and fitness benefits.
Remember that you don’t have to do all your exercises in one session. If you already exercise vigorously several times a week, there’s no reason to quit. But if 60 minutes a day seems like too much for you, try 30 minutes a day as a starting goal.