I read a summary of a study that left me feeling both relieved and confused – relieved, because it turned out that a mere 15 minutes exercise daily would extend my lifespan, and confused, because convention always said that you should exercise 30 minutes or more over 5-6 days a week. I’m not trying to get out of working out, but I’d like to know just how much exercise is sufficient.

The reason you’re exercising plays a role in determining how much is enough. Fifteen minutes a day is adequate if you want to gear up or de-stress after a long day at the office, or just to get into slightly better shape. On the other hand, efforts to lose weight, improve blood pressure, or aerobic fitness call for longer and/or more intense bouts of exercise.

Generally, we all require aerobic, strength, and flexibility activities. Considering what is required for fitness is another way of determining how long you should exercise each day/week.

As a guide, the American College of Sports Medicine (ACSM) recommends at least 30 minutes of moderate intensity cardio 5 days weekly, or at least 20 minutes of vigorous intensity cardio 3 days weekly, or a combination of both for cardio fitness.

The ACSM also recommends strength and neuromotor training 2-3 times weekly, and flexibility training at least 2 days weekly. Flexibility exercises ensure that muscle groups and tendons keep range of motion and mobility. Each stretch should be held for 1 minute.

Neuromotor fitness is also known as functional fitness, and combines motor skills for coordination, agility, balance, gait, and proprioceptiion (the awareness of the effort used for a movement and the relative positioning of the limbs). Qi gong, tai chi, and yoga improve neuromotor fitness.

However, since those are “recommendations,” not “stipulations,” we’re back to the original question: how much is enough? In my opinion, you should stick to the daily 15-minute routine if it makes you feel good about yourself. You’ll probably extend the session or add a second 15-minute bout as you become fitter, which eventually adds up to the 150-minute weekly minimum recommended by the ACSM. Unless you’re a professional athlete, exercise should be something that you do because it makes you feel good about yourself.