How do I improve my cardio endurance?

To improve your cardio endurance, do 3 to 4 sessions a week, keep most of them at an easy pace, and add one harder interval session. Increase your total time by about 10 percent a week. Most people feel a clear difference within 4 to 8 weeks.

Go easy more often than you think

Endurance is built by spending time in a comfortable zone where your heart and muscles adapt without much strain. If you can say a full sentence while exercising, you're at the right pace. Many beginners go too hard, get tired early and quit the session short, which builds less fitness than a slower, longer one.

Pick what you enjoy: running, cycling, swimming, rowing or even brisk walking. The type matters less than the regularity.

Add one hard day

One session a week of intervals teaches your body to handle higher effort. A simple version:

1. Warm up for 10 minutes.
2. Go hard for 2 minutes, then easy for 2 minutes. Repeat 4 to 6 times.
3. Cool down for 5 to 10 minutes.

Over several weeks, extend the hard parts to 3 or 4 minutes, or add another round.

Progress in small steps

If you jog 20 minutes now, make it 22 next week, and so on. Raising time too quickly is the way most people get shin splints, sore knees or just burned out. Every fourth week, drop the total by a third and let your body catch up.

Simple things that help

• Sleep. Your fitness gains happen while you recover.
• Fuel. Eat something before long or hard sessions, and drink water.
• Breathing. Breathe through both nose and mouth. Don't try to force a rhythm.
• Strength. Two short lifting sessions a week make you more efficient and less injury-prone.
• A reason to show up. League of Fitness syncs runs, rides and walks from Apple Health and scores them by heart rate zones, so your easy sessions and your weekly interval day both count toward a daily match

What to expect

In the first two weeks, nothing seems to change. Around weeks 3 to 4, the same pace feels easier and your heart rate at that pace drops. By week 8, you can often go twice as long. Resting heart rate also tends to come down over time, which is covered in what your resting heart rate says about your fitness.

If you feel chest pain, dizziness or breathing trouble that seems out of proportion, stop and talk to a doctor.