High-Intensity Interval Training (HIIT) and VO2 Max
You may have heard these terms used before, but what do they actually mean? Why is HIIT (high-intensity interval training) so popular? How is a VO2 max score related to longevity? I answer these questions and more in this blog!
In case you missed last week's blog on strength training for women, read it here!
What is HIIT?
HIIT stands for High-Intensity Interval Training. It involves alternating between short bursts of intense effort (like sprinting or fast-paced exercises) and periods of lower-intensity activity or rest. These intervals are repeated for a set duration—typically 10 to 20 minutes max. The primary goal is to elevate your heart rate to max effort and stretch your endurance to enhance cardiovascular fitness and strength. Engaging in regular HIIT-style workouts can have a beneficial cascade effect on other systems of health, including heart health, metabolism, and blood pressure.
Here is an example of a fully customizable workout layout:
Choose an exercise and engage anywhere from 15 seconds to 4 minutes using close to maximum effort (90-95% maximum heart rate) and 1-3 minutes of easy recovery. Repeat 4-6 times.
Examples:
Sprint at maximum effort for 30 seconds, followed by a walk or rest for 1 minute
A timed set of burpees with a rest period between sets
All out on the row machine or a stationary bike for 20 seconds, followed by rest for 30 seconds
Benefits of HIIT
If you’re short on time and looking for a workout that packs a punch, HIIT may be for you! High-intensity interval style of training is not only very efficient, but it is very accessible; you don’t even need a gym membership.
Here are 5 unique benefits to high-intensity interval training:
1.) Efficiently burn calories
A study comparing the different types of exercises (aerobic, resistance, and combined high-intensity interval training) with the same duration found that HIIT burned 25-30% more calories than the other forms of exercise.
2.) Increase in metabolic rate afterwards
A study conducted on the metabolic rate of women after engaging in high-intensity interval training (HIIT), high-intensity interval training (HIRT), and aerobic endurance exercise (AEE) found that the post-exercise resting energy expenditure (REE) was higher while the respiratory exchange rate (RER) was lower in the women who engaged in HIIT.
Resting energy expenditure (REE) refers to the calories your body burns at rest to maintain essential functions such as breathing, circulation, and digestion. Because the women who did HIIT exercises in the study had a higher RER, they were burning more calories at rest even after the training.
Respiratory Exchange Rate (RER) is a measurement that looks at the ratio of carbon dioxide (CO2) produced to oxygen (O2) consumed by our metabolism. The exact mathematical equation is this: RER=VCO2/VO2
RER typically ranges from 0.7 to 1.0, and these numbers refer to what the body is using as fuel. Lower values indicate more fat burning, and higher values indicate more carbohydrate burning. The study measured women's lower RER, which means they were continually burning fat, even after the exercise was complete.
3.) Improves your muscles’ ability to use oxygen
Although endurance training is typically viewed as a way to increase the body’s oxygen consumption, a study found that individuals who engaged in 20-minute HIIT-style workouts 4 days per week for 5 weeks improved their oxygen consumption by 9%. Interestingly, the improved oxygen was almost the same as participants who cycled continuously for 40 minutes, 4 days per week.
4.) Improves Cognition and brain health longevity
A recent study published in Aging and Disease suggested that HIIT may be better for brain health than other exercise routines. They examined 151 healthy adults aged 65-86 in a six-month exercise program. In measuring the hippocampus–the region of the brain involved in learning and memory–the researchers concluded that positive changes in the hippocampus were greater in the HIIT exercisers. Remarkably, there was a follow-up evaluation to the study five years later, and the researchers again found that the people in the HIIT group retained their improved cognitive ability, even if they were no longer doing high-intensity intervals.
What is VO2 Max?
VO2 max refers to your body’s ability to use oxygen. It demonstrates how much oxygen your body absorbs and uses when working out. In other words, VO2 max shows how well your heart pushes blood to your muscles and how well your muscles can extract that oxygen when training. As you breathe, a metabolic reaction within muscle cells gives them energy using adenosine triphosphate (ATP).
Increase in oxygen uptake = more ATP muscles produce = more energy to fuel workouts.
How is it Measured?
VO2 max is measured in milliliters of oxygen consumed in a minute per kilogram of body weight (mL/kg/min). You can test your VO2 max number at the doctor’s office or exercise lab where doctors record your oxygen consumption (breathing in) and carbon dioxide production (breathing out) while running on a treadmill, cycling, or another form of cardio. Some fitness trackers also show you an estimate based on your health trends and correlated activity levels.
Having a higher VO2 max is typically correlated with being in “good” cardiovascular shape, but there is a degree of variation. Factors such as body fat percentage, age, and activity level play a role in VO2 max.
HIIT and VO2 Max
VO2 max and HIIT work hand-in-hand! High-intensity interval training is a great way to improve your VO2 max. It allows your body to improve its cardiovascular fitness while maintaining muscle mass, improve how well your body uses oxygen for energy during exercise, and it supports your overall fitness level.
Above all, increasing overall fitness and being aware of your level of fitness has a cascade of benefits that not only reduces the risk of chronic disease, it improves quality of life and longevity.