Finding it hard to fit in fitness? Just getting through a day of school and after-school commitments can leave most of us wondering where to find time.

Experts recommend that teens do 60 minutes or more of physical activity every day. Most of that should be moderate to vigorous activity. Aerobic activity is anything that gets your heart going — like biking, dancing, or running. Then take a few minutes for some strength training. Exercises like the ones below help build muscle and boost metabolism. Flexibility is the third component of well-rounded exercise. Check out yoga as one way to stay flexible.

You can do these three strength-building exercises at home. There's no need for special equipment, expensive gym fees, or lots of time. Just check with your doctor, PE teacher, or coach first to be sure these exercises are OK for you.

Sit Backs: Step 1

• Sit on floor, legs bent
• Arms straight in front

Sit Backs: Step 2

• Lean back gradually
• Keep arms straight and tummy tight
• Take it as far back as comfortable
• Slowly return to sitting position
• Repeat

Chair Squats: Step 1

• Stand tall
• Chair behind you

Chair Squats: Step 2

• Arms straight in front
• Slowly start to sit down
• Stop before your butt hits the chair
• Slowly straighten to standing
• Repeat

Butterfly Breath: Step 1

• Stand tall
• Feet hip width apart
• Arms lifted out to the sides

Butterfly Breath: Step 2

• Exhaling, lift right knee and touch it with left elbow
• Inhaling, return to position one
• Switch sides and repeat

About Sets and Reps

Most fitness instructors recommend repeating a particular strength training exercise several times in a row. These are known as repetitions, or “reps,” and they’re done in “sets.” Each set consists of a specific number of reps, usually between 8 and 15. Fitness instructors often recommend that people rest after one set and then perform another set (or more) of the same number of reps. For the exercises shown above, start with 10 reps, adding sets of 10 as you get comfortable. Rest for 30 seconds between sets.