In the 1960s, a man name Kenneth H. Cooper came up with the concept of aerobics. Originally, aerobics, via the aerobics point system, measured the effectiveness of different exercises and activities for improving cardiovascular health. This lead to the coining of the term today known as cardio. Over time, however, the main focus of these aerobic-based exercises began shifting from improving cardiovascular health to helping people lose weight and burn fat. And it makes a lot sense since cardio exercises do indeed help people lose weight by burning excess calories and also help people burn fat by activating the fat-burning aerobic energy pathway in the body.
This aerobic energy pathway is the energy system in your body that uses stored fat- after being converted into fatty acids- in conjunction with oxygen and other chemicals to produce the body’s sole source of energy known as ATP. As long as this pathway is utilized, more and more fat will be burned. Early science believed that the best way to activate this pathway is by performing long-duration, low intensity exercises such as long-distance jogging, cycling, or swimming. This ultimately lead to the creation of other forms of cardio exercises today such as aerobic dance classes, step aerobics, and the extremely popular Zumba.
Although low intensity cardio is still the exercise king of weight loss and fat burning today, newcomers have arrived to challenge for the crown. The biggest gripe with low intensity cardio exercises is the duration, which often takes more than an hour. Cardio might seem to be fun and exciting the first time it’s done, but over time, it begins to feel way too repetitive and long. As more and more people become bored and lose interest, more and more people will quit. And for some people, they simply do not have the time. But are low intensity cardio exercises really the best option to burn fat and calories?
This is where the most prominent challenger to low intensity cardio steps in. This challenger is known as High Intensity Interval Training. High Intensity Interval Training, as the name suggests, is any “training” program that are performed in “intervals” at a “high intensity.” High intensity interval training, also called HIIT for short, are alternating periods of short high intensity activity with periods of low intensity recovery. The most popular exercise for HIIT is alternating sprinting with walking. Each sprint interval lasts between 5-30 seconds and each walk interval will also last between 5-30 seconds. The more fit you are, the higher the work to rest ratio will become. For example, if you’re really fit, you might be sprinting for 30 seconds and walking for 10. Someone that is less fit might be sprinting for 10 seconds and walking for 30. The total session length varies between 5-20 minutes, and because of the intensity, should only be done 3 days a week. When added together, that’s a maximum of only 60 minutes of exercise per week!
So what’s the science behind this? When the body goes through intense activity, it needs to be able to keep up with the energy demand. One way of doing so is by secreting high levels of fat-releasing hormones known as catecholamines into the bloodstream. The more catecholamines, the more quickly fat is broken down into free fatty acids. Free fatty acids are then used to replenish energy stores. Studies have also shown that HIIT creates a strong EPOC effect. EPOC, short for excess post-exercise oxygen consumption, is the extra oxygen your body needs in order to recover after an intense activity. The more oxygen you take in also means more calories are being burned. This effect can last up to an amazing 24 hours after the workout. However, other studies have shown that the amount of calories being burned during EPOC isn’t all that much, where at most an extra 60 calories being burned.
There are also a few drawbacks. High intensity interval training is extremely strenuous. People might drop out of low intensity cardio because it’s long and boring, but people can just as easily drop out of HIIT because it’s just too hard. High intensity interval training might also cause joint pain due to the high impact, and over time, might lead to serious injuries if performed incorrectly. Also, low intensity cardio can actually be done every day. HIIT, however, requires ample recovery time, which can interfere other exercise routines. Although HIIT might challenge low intensity cardio for the crown, it doesn’t come without its drawbacks!