That’s a simple question, and you’d think the answer would be simple, too. But, alas, it is not. How much exercise you need each day depends on several factors: how much exercise you normally get each day right now, what your fitness goals are and what your health and body conditioning are like. So, the answer is, “It depends.” For most of us, the answer is also, “More than you are getting.”

If you are healthy and in fairly good shape, most people agree that you can probably squeak by with thirty minutes of moderately intense aerobic exercise at least three times a week. Aerobic activity is any activity that increases your breathing and heart rate, such as walking, bicycling or skiing. During moderately intense exercise, you should feel slightly breathless, but be able to carry on a conversation. If exercising for thirty minutes at a time is difficult for you, you can break it up into chunks of ten to fifteen minutes each; as long as it adds up to thirty minutes.

That’s probably the minimum amount of exercise you need to maintain your current weight and fitness level. If you want to become more fit or to lose weight, you need to up the ante. You can increase the frequency, length and/or intensity of exercise, but do it gradually. Your goal is to reach the point where you are exercising at or above a moderately intense level for sixty minutes five or six times a week.

If you have any health issues, haven’t exercised in a while or are on the far side of 35, it’s wise to see a doctor before you start. Exercise is supposed to stress your heart, lungs, muscles, bones and joints, so you want to make sure they are healthy enough to handle it. After you get the okay from your physician, start slowly and increase your exercise level gradually. Increase the frequency (number of times you exercise per week), then the length (minutes you exercise each day) and lastly the intensity (how hard you exercise) of exercise until you reach your desired fitness level.

It’s also important to ask what kinds of exercise you need every day. In addition to aerobic exercise, you need resistance exercise and stretching. Aerobic exercise increases your cardiovascular health; resistance exercise makes you stronger and improves bone and joint health, and stretching improves your flexibility.

Resistance exercises are usually done two or three times a week; muscles need a day or two between each session to repair and build new tissue. Once again, begin slowly and increase gradually. With resistance exercises, you’ll increase the number of reps (repetitions of each exercise) and then the amount of resistance (weight). Consult with a trainer to learn specific exercises that work all the muscle groups and to make sure you are doing them correctly.

A trainer can also show you how to stretch effectively. Stretching every day keeps you from “stiffening up” as you grow older and improves your overall fitness level.

How much exercise do you need every day? Some. Your body needs to move. In order to keep it healthy, you need aerobic, resistance and stretching exercise at least several times a week.