For the Runners: Three Types of Interval Training

Want to see the pounds melt off? If you're sick of running for long distances, try quick and effective interval training.

-Kim Jones, BettyConfidential.com

We've all heard that interval training is a great from of cardio. But, do you know why? Well, when you run intervals you can decrease the duration of your workout and still burn more calories. For some people, cardio entails running continuously at a particular target heart rate for specific distances or for a particular unit of time. Interval training is an alternative that will enhance your fitness level through the manipulation of training intensities.

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By alternating between high and low intensity periods, the heart rate continuously increases and decreases. Working at higher intensities also stimulates weight loss, and is effective for people who want to decrease body fat percentage, according to Jason R. Karp's study "Interval Training for the Fitness Professional" in theStrength and Conditioning Journal. Other positive benefits include increasing strength and power, lactic acid tolerance, and improved endurance.

Here are three types of interval training and how to do each:

Interval Training Type 1
Repeatedly raising and lowering the heart rate during training increases the amount of blood pumped during each heartbeat, which means more oxygen is delivered to your working muscles, according to Karp. Short, high intensity sprints lasting 5 to 10 seconds heavily recruit fast twitch muscles fibers. Developing these muscle fibers increases strength, power, and speed. Those who play in sports consisting of short bursts of activity followed by jogging or walking will benefit greatly from this type of training.

Repetitions: Depending on your fitness level perform 5 to 10 repetitions 
Work to Rest Ratio: 1:6 for beginners and 1:3 for advanced individuals. For example, 6 seconds of rest for every 1-second of sprinting equals 60 seconds of recovery for a 10-second sprint. 3 seconds of rest for every 1-second of sprinting equals 30 seconds recovery for a 10-second interval
Recovery: No active recovery should be used. Perform sprint then walk back to starting line, or simply stand for the prescribed rest time. Jogging, or active rest, will only deplete the energy system that needs to be replenished and available for the next sprint interval.

Interval Training Type 2
Running sprint intervals at a longer duration, from 30 seconds to 2 minutes, will target the second energy system. When you run for this amount of time, high levels of lactic acid will build up in the blood and muscles. This indicates that you are targeting the anerobic, or lactic acid, energy system. This may cause muscle fatigue and some discomfort, but training within this system allows the body to be able to withstand the effects of lactic acid buildup. This can also carry over into everyday activities like carrying heavy bags of groceries or dragging heavy moving boxes from one place to another. The biggest benefits you will gain from this type of training are fast twitch muscle development and improving your resistance to muscle fatigue.

Repetitions: Beginners should perform a minimum of 3 repetitions, advanced persons should perform 6 to 8 repetitions
Work to Rest Ratio: 1:2 for all individuals. For example, 2 seconds of rest for every 1 second of sprinting equals 60 seconds recovery for a 30 second sprint
Recovery: Use active recovery to help remove lactic acid more quickly. For example, sprint for a specific duration of time and jog at a lower intensity during the rest period.

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Interval Training Type 3
The final type of interval training incorporates longer work periods and targets the Aerobic, or oxidative, energy system. This energy system utilizes carbohydrates and fats to fuel the body. During high intensity aerobic exercise, the majority of the energy comes from carbohydrates. Steady, low intensity work mainly uses fats and protein. Continuous running for longer than 2 minutes increases your endurance and also improves the body's ability to transport and use oxygen. Some cardiovascular benefits of aerobic training are decreased risk for heart disease, high blood pressure and cholesterol, and it increases the heart's ability to pump blood and oxygen throughout the body, according to Karp. The focus of this type of training is to run at a pace that is a specific percentage of your maximum heart rate. Depending on your fitness level, any range from 140 to 180 beats per minute should be an appropriate training stimulus.

Repetitions: 3 to 5 for beginners or 8 to 12 for advanced individuals
Work to Rest Ratio: 1:1 for all levels. Recovery time should be equal to the work period. For example, if you sprint for 3 minutes 30 seconds, then the rest should be the same at 3:30
Recovery: Low range intervals (2 minutes) should incorporate inactive recovery. Longer work intervals (4-6 minutes) require active recovery such as walking or jogging.

Kim Jones is a Certified Strength and Conditioning Specialist. She has experience training male and female athletes at Division I Universities, High School sports programs, and within the general population. Follow Kim on Twitter @JonesStrength.