A Guide to Interval Training

If your free time is limited, but you’re seeking an effective way to exercise, then you may want to consider interval training — a complete, time-efficient workout that helps increase your aerobic capacity and build strength without extra fuss or equipment. Whether you’re an experienced athlete or someone looking to start improving your fitness, interval training can fit into the lifestyles of people at all fitness levels.

Simply stated, interval training is a type of workout that alternates between periods of vigorous activity and recovery in a single session. You typically engage in a short burst of intense activity, followed by a longer period of less intense activity or recovery, and then cycle through it again. A basic example of interval training is trading off between walking and jogging; adding in short bursts of jogging during your walk will elevate your heart rate and deepen your workout. Other exercises you can use for your high-intensity burst include high knees, mountain climbers, jump roping, and pull-ups; the possibilities are endless.

Interval training uses both your aerobic (with oxygen) and anaerobic (without oxygen) systems. When you push into a high-intensity interval, your body uses its anaerobic system by relying on energy stored in your muscles; lactic acid builds up as a byproduct.1 Then, as you enter into a recovery phase, the aerobic system steps in, and your body works to break down the lactic acid while using oxygen as it converts carbohydrates into energy. There are different styles of interval training, each with its own work-to-rest ratio. Check out the following overview to see if interval training might be a good fit for you.

As you look into interval training styles and their target heart rate zones, you may wonder what that means and how to calculate it. Most adults have an average resting heart rate of 60 to 100 beats per minute (bpm). Heart rate zones are calculated based on your estimated maximum heart rate.4 Your max heart rate equals 220 minus your age. For example, a 40-year-old’s max heart rate would be 180 bpm.

Once you’ve figured out your max heart rate, it’s easy to calculate what rate to target for the different training zones. The American Heart Association breaks heart rate zones down into two simple categories:5

• Moderate intensity activities: 50-70% max heart rate
• Vigorous activities: 70-85% max heart rate

For example, if a 40-year-old workout enthusiast is seeking a moderate, endurance-focused training session, they will target a heart rate of 50-70% of their 180 bpm max — this comes to a heart rate goal of 90-126 bpm. You can use a fitness tracker to help you monitor your pulse during your workout. If this isn’t available to you, you can simply take your pulse on the thumb side of your wrist. Count the number of heartbeats you feel in 30 seconds and multiply by 2 to find your heart rate in beats per minute.

Interval training can benefit just about anyone looking to improve their fitness. You may be looking to shake up your exercise routine, and interval training can be a fun way to design an engaging workout. If you are a more seasoned athlete, you may seek training geared toward your specialty or even target specific movements with a more thoughtful approach. Personal trainers are a great resource to help you determine what will work best for you based on your strength and endurance goals, target heart rate, and cardiorespiratory health.

Below, we’ve broken down some of the benefits you might find from adding interval training to your exercise routine.

Interval training is effective but intense. But don’t be deterred if you are older or have overweight. Interval training is adaptable and can be suited to your fitness level. However, it’s critical that you speak with your doctor if you have any medical conditions prior to jumping into a vigorous new exercise routine. There is evidence that interval training can be useful, even if you have a serious condition (and your doctor approves). A 2023 clinical trial demonstrated that HIIT was safe, well tolerated, and effective for study participants with coronary artery disease that were in cardiac rehabilitation.11 Research has also shown that participation in HIIT workouts can help type 2 diabetes patients with their glucose control.12

As you start an interval training regimen, watch out for overuse injuries and be careful to use proper form. Remember that your workout doesn’t have to include high-impact movements or heavy weights (activities like squats or swimming are just as, if not more, effective). And you may be anxious to get started, but your body will thank you if you start slowly. Going too hard too soon can result in a case of delayed onset muscle soreness (DOMS), which takes days to recover from. Try one or two high-intensity rounds to start and see how you feel afterward. As your endurance improves, you can begin to ramp up the intensity and play with the length of your intervals.