Less time-consuming and more challenging than steady state cardio, a High Intensity Interval Training (HIIT) cardio workout is a great way to get ripped and ready for summer, especially when you’re pressed for time. Its changing speeds and intensity levels can also help increase your athletic performance and keep your body in a calorie-burning state after the session is over.

For this article, I’ve put together three 15-minute HIIT workouts that anyone can do. Rotate the workouts so you’re doing each one twice a week (six sessions per week total), and you should see results in a couple of months, as long as you’re also following a sound nutrition program. Check out the video player above for a 7-minute HIIT warm-up to do before your workout.

1. Walking/Running

Take this to a track or to an area with no traffic lights and few pedestrians, where you can keep going without having to stop. Walk for three minutes. At the four-minute mark, sprint as fast as you can for one minute. After a minute, slow down and resume walking. Repeat this pattern three times and finish with a three-minute walk that will double as a cooldown. If you want to make this more intense, wear a weighted vest.

2. Boxing

For this one, you need a heavy bag and boxing gloves. Shadow box for two minutes at a normal pace to warm up. After two minutes, hit the heavy bag as fast and hard as you can for one minute. After this “round,” step away from the heavy bag and resume shadow boxing. Complete six rounds and finish with a two-minute shadow boxing cooldown.

3. Biking

Ride your own bicycle or hit a stationary bike at the gym. Pedal for a minute at a normal pace. Next, either increase the resistance of your stationary bike or go all out on your regular bike for a minute. Decrease the resistance or slow down for another minute. Repeat this until you’ve completed seven rounds. End the workout moving at your slower pace.