As a coach, one of the most popular questions I get asked is whether High-Intensity Interval Training (HIIT) workouts really work to get fit. My answer is simply “YES”, HIIT workouts can be highly effective for improving fitness levels. But, like any exercise program, there are important considerations to keep in mind.
Let’s get down to business and learn more about how this type of training can be beneficial for you.
What is HIIT?
HIIT involves alternating short bursts of intense exercise with recovery periods of low-intensity exercise or rest. These workouts typically last 15-30 minutes and can be done using a variety of exercises, including running, cycling, rowing, or bodyweight exercises.
The Science Behind HIIT
One of the key benefits of HIIT is its ability to stimulate the body’s metabolic processes in a way that traditional steady-state cardio workouts don’t. During HIIT workouts, the body experiences a rapid change in intensity that requires the body to quickly switch between aerobic and anaerobic energy systems. This results in an increased demand for oxygen and energy, leading to a greater calorie burn during and after the workout.
Numerous studies have investigated the effects of HIIT on various aspects of health and fitness. For example, a study published in the journal PLoS ONE in 2016 found that 12 weeks of HIIT improved cardiovascular health and metabolic markers to a similar extent as traditional endurance training, despite a five-fold lower exercise volume and time commitment (1). Another systematic review and meta-analysis published in the British Journal of Sports Medicine in 2014 found that HIIT was effective in improving various markers of cardiometabolic health in patients with lifestyle-induced diseases
Research has shown that HIIT can be an effective way to improve cardiovascular fitness, increase muscular strength, and reduce body fat. A 2019 study published in the Journal of Sports Medicine and Physical Fitness found that HIIT was more effective at improving VO2 max (a measure of cardiovascular fitness) compared to traditional continuous exercise.
Additionally, a 2018 study published in the Journal of Strength and Conditioning Research found that HIIT was more effective at improving muscular strength compared to moderate-intensity continuous exercise.
HIIT can also be an effective way to burn calories and reduce body fat. A 2017 study published in the Journal of Obesity found that HIIT was more effective at reducing body fat compared to moderate-intensity continuous exercise.
It’s important to note that the effectiveness of HIIT workouts can vary depending on factors such as age, gender, fitness level, and overall health. People who are new to exercise or have pre-existing health conditions should start with low-impact exercises and gradually increase the intensity and duration of their workouts.
Benefits of HIIT
Aside from improving fitness levels, HIIT workouts have other benefits, including:
- Improves cardiovascular health: HIIT has been shown to improve cardiovascular health by increasing the heart’s ability to pump blood and oxygen to the muscles. Studies have found that HIIT can increase the efficiency of the cardiovascular system, lower resting heart rate, and improve blood pressure (1).
- Increases fat burning: HIIT can be an effective way to burn fat and lose weight. During HIIT, the body experiences an oxygen deficit, which means that it is working harder than it can take in oxygen. This leads to a state of “oxygen debt” in which the body continues to burn calories at an elevated rate even after the workout has ended (2).
- Improves insulin sensitivity: HIIT has been shown to improve insulin sensitivity, which is the body’s ability to use insulin effectively to transport glucose from the bloodstream into cells for energy. Improving insulin sensitivity can help reduce the risk of developing type 2 diabetes (3).
- Increases muscle strength and endurance: HIIT can be an effective way to build muscle strength and endurance. During HIIT, the body works at a high level of intensity, which can lead to muscle fatigue and damage. This damage triggers the body’s repair mechanisms, leading to increased muscle strength and endurance over time (4).
- Saves time: HIIT workouts can be completed in a shorter amount of time compared to traditional cardio workouts. A typical HIIT workout can be completed in 20-30 minutes, making it a convenient option for people with busy schedules who may not have time for longer workouts (5).
- Reduces boredom: HIIT workouts can be varied and challenging, making them a more interesting and engaging form of exercise compared to traditional steady-state cardio workouts (6).
- Increases metabolism: HIIT can increase metabolism by increasing the body’s energy expenditure during and after exercise. This can lead to a greater calorie burn throughout the day, even when not exercising (7).
HIIT Workout Examples
Here are a few examples of HIIT workouts that you can try:
- Sprint Intervals: Warm-up for 5-10 minutes, then alternate between 30 seconds of all-out sprinting and 30 seconds of rest. Repeat for 10-20 minutes.
- Tabata Protocol: Warm-up for 5-10 minutes, then do 20 seconds of all-out effort followed by 10 seconds of rest, repeating for a total of 8 rounds (4 minutes).
- Bodyweight Circuit: Perform a circuit of bodyweight exercises, such as push-ups, squats, lunges, and burpees, for 30 seconds each with 10 seconds of rest between exercises. Repeat for 4-5 rounds.
Who should avoid HIIT workouts?
While HIIT can be highly effective, it may not be suitable for everyone. Here are some groups of people who should avoid HIIT workouts:
- People with pre-existing health conditions: Individuals with conditions such as heart disease, high blood pressure, or joint pain should consult with their healthcare provider before starting HIIT workouts.
- Pregnant women: Pregnant women should avoid HIIT workouts that involve jumping, sudden changes in direction, or rapid changes in intensity.
- Individuals with mobility issues: HIIT workouts often involve high-impact movements, which can be challenging for individuals with mobility issues or injuries.
- Older adults: Older adults should start with low-intensity exercises and gradually increase the intensity and duration of their workouts to avoid injury.
In summary, while HIIT workouts can be highly effective for improving fitness levels, burning calories, and reducing body fat, it’s important to approach them with caution and gradually increase intensity and duration over time. Individuals with pre-existing health conditions, pregnant women, individuals with mobility issues, and older adults should consult with their healthcare provider before starting HIIT workouts or consider alternative exercise options. It’s also important to listen to your body and rest when needed. With consistent effort, HIIT workouts can help you achieve your fitness goals.
Sources and references:
- Gillen JB, Martin BJ, MacInnis MJ, et al. Twelve Weeks of Sprint Interval Training Improves Indices of Cardiometabolic Health Similar to Traditional Endurance Training despite a Five-Fold Lower Exercise Volume and Time Commitment. PLoS ONE. 2016;11(4):e0154075. doi:10.1371/journal.pone.0154075.
- Boutcher SH. High-intensity intermittent exercise and fat loss. J Obes. 2011;2011:868305. doi:10.1155/2011/868305.
- Tjønna AE, Lee SJ, Rognmo Ø, et al. Aerobic Interval Training versus Continuous Moderate Exercise as a Treatment for the Metabolic Syndrome: A Pilot Study. Circulation. 2008;118(4):346-354. doi:10.1161/CIRCULATIONAHA.108.772822.
- Gibala MJ, Little JP, van Essen M, Wilkin GP, Burgomaster KA, Safdar A, et al. Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. J Physiol. 2006;575:901–11.
- Laursen PB, Jenkins DG. The scientific basis for high