A Mass General fitness expert shares his advice on how often you should exercise and what types of exercise are important.

In my role as a personal trainer, I often advise people on how to get the most out of the time they set aside for exercise and meet their goals of feeling and looking better.

Cardiovascular health and endurance

Examples: Jogging, aerobic classes, cycling

  • Do 30 minutes per day of moderate intensity aerobic exercise at least 5 days a week (150 minutes total), OR
  • Do 20 minutes per day of vigorous aerobic exercise at least 3 days a week (60 minutes total), OR
  • Do a mix of the two above. You can reach those totals in small doses, with 10 minutes at a time.

Everyone is busy and wants to exercise in a way that is enjoyable and efficient. And so, although I train people of all fitness levels, I am often asked many of the same questions. Here are the most common questions, along with my suggestions.

How often do I need to exercise?
There is no magic answer. But there are recommendations for healthy adults. Your weekly routine should include cardiovascular and endurance activities, muscular strength training and stretching exercises to maintain your flexibility. I’ve detailed the specifics in the boxes in this story.

If you work out at a moderate level, then you should do cardiovascular exercise at least 150 minutes total per week spread over five days. You also need to do strength training and stretching exercises two to three days a week.

Can I just do cardio and not lift weights? Do I really need to stretch?

Everyone needs to do all three — cardio, strength training and flexibility — to be at their best fitness level.

Cardio exercise, like running, is great for your heart and lungs. But it will not help you build much strength because your muscles need progressively increasing resistance to strengthen them. Traditional cardiovascular exercises don’t provide that.

Lifting weights (strength training) increases muscle strength, but it doesn’t increase flexibility like consistent stretching does.

And even though beginners to yoga would gain flexibility and strength during their first couple of months of practice, after a while, strength improvements from yoga decline because, like most cardiovascular exercises, it lacks progressive resistance.

General muscular strength

Examples: Lifting weights or performing exercise like push-ups that use your body weight as resistance

  • Perform strength training 2-3 days a week on non-consecutive days.
  • Use a program that incorporates exercises for all major muscles.
  • Keep challenging your body by adjusting weight or body resistance. You should feel fatigue between 8-12 repetitions of each exercise.

What’s the difference between free weights and weight machines?
Both free weights and weight machines are tools used for strength training. They work by making muscles exert against force. The major difference is that weight machines typically feature a seated position that doesn’t challenge core stability or balance, whereas free weights tend to engage lots of muscles concurrently, and in more natural positions. I recommend free weights or even body weight exercises as a better choice over weight machines in almost all cases.


Examples: Yoga, stretching

  • Do stretching exercises at least 2-3 days a week.
  • Stretching exercises should target the muscles of both the upper and lower body. Focus on areas that are tight. If you sit or stand a lot you may need to frequently stretch your chest, upper back and hips.
  • Do static stretching, which is holding a stretch at the point of mild discomfort for 10-30 seconds and repeat 2-3 times, OR
  • Do dynamic cyclical stretching – holding a stretch for 5-6 seconds at the point of mild discomfort and repeating 10-12 times.

What’s the best exercise to get a flat stomach?
There isn’t a single best exercise for a flat stomach. A flat stomach mainly comes from reducing abdominal body fat, which is overwhelmingly about nutrition, not exercise. Core stability exercises can help firm the abdominal muscles, but those muscles don’t own the fat that lies over them and can’t burn it off alone. So, exercise for your health and to support your nutritional efforts, but don’t count on exercise alone to give you a flat stomach.

What if I play softball or chase my children around, does that count?
Recreational activities or chasing kids, can count as activity, but not exercise training. That’s not to say they are not great to do, but they will not substantially increase your fitness. But if you are working on your fitness you will see the benefits when you can run the bases faster or keep up with your child.

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Mike Bento is an advanced trainer at The Clubs at Charles River Park and Massachusetts General Hospital. He holds a master’s degree in human movement and is certified by the National Academy of Sports Medicine as a corrective exercise specialist and performance enhancement specialist.