HIIT (high-intensity interval training) workouts have become popular in recent years for a number of reasons. They don’t take as much time as a normal workout (some can take as little as 10 minutes), and research shows they improve fitness, lower blood pressure, and help people better control their blood sugar levels – which can help with weight loss and weight loss Prevent diseases like type 2 diabetes.
And recently, a review found that a form of HIIT exercise called low volume HIIT had cardiometabolic health benefits. This means that low-volume HIIT can produce similar or greater improvements in cardiorespiratory fitness, blood sugar control, blood pressure, and heart function compared to continuous aerobic exercise (e.g., a five-mile run).
HIIT is characterized by alternating between low and high intensity training intervals. For example, this may include cycling at an easy pace for a few minutes before increasing the effort to a high or even maximum level for a short period of time before returning to an easy pace. This is then repeated throughout the training session, with the total time spent at high intensity typically being small. There are different categories of HIIT depending on the intensity of the training required.
The researchers on this study conducted an updated review of the current evidence on low volume HIIT and its heart health benefits. Up-to-date overviews provide an up-to-date overview of the latest information in a particular area or research area that is rapidly evolving.
They looked at a total of 11 studies. They defined low volume HIIT as an exercise in which the total time in active intervals (excluding rest periods) was less than 15 minutes. Overall, they found that low-volume HIIT improved a person’s ability to burn fuel (like carbohydrates and fat), which is directly related to blood sugar control – and can be important in preventing diseases like type 2 diabetes . They also found that supervised HIIT is safe for healthy people and people with obesity and type 2 diabetes.
It has also been shown that low volume HIIT improves the structure of the heart – for example, chamber enlargement. This increases the volume of blood that the heart can pump to the rest of the body with each heartbeat. These benefits applied to both people with no underlying health conditions and people with heart failure (in whom the heart is unable to pump blood around the body properly because it has become too weak or stiff).
The fact that this review showed that low volume HIIT also improves cardiorespiratory fitness is significant. Even moderate improvements in heart health have been shown to reduce adverse cardiovascular events such as heart attack and stroke by up to 30 percent.
It might be helpful to focus on the quality of the exercise rather than the duration, and find ways to incorporate higher intensity movements into everyday activities
These results show that even a short exercise can improve health. Current guidelines from the World Health Organization recommend that adults do 150 to 300 minutes of moderately intense exercise or 75 to 150 minutes of vigorous exercise per week. However, lack of time is often cited as the main obstacle for many people to exercise. Low volume HIIT has the potential to be more time efficient and provide similar or greater improvements in health outcomes than longer workouts.
My own research suggests that low volume exercise interventions can be used without feeling overly difficult or uncomfortable, which is important in motivating people to continue an exercise program. It can also be good for people who are inactive or have long-term health problems.
How does HIIT work?
Regardless of the type of HIIT you are doing, the health improvements are believed to be caused by the rate rather than the amount at which skeletal muscle glycogen (carbohydrates that are stored by the body for energy) is used. Muscle glycogen is an important fuel reserve – so our body tries to replenish it as a priority.
HIIT workouts use muscle glycogen at such a rate that the body increases the number and activity of mitochondria (powerhouses of cells) in our muscles so that we can meet the energy needs of the workout. This in turn leads to improvements in fitness, metabolic function and health.
There are some limitations in researching HIIT. Most of the studies were carried out in laboratory settings. This makes it difficult to know how effective HIIT would actually work as an exercise strategy in the real world.
This review also has its own limitations. Typically, experts use a systematic review or meta-analysis when analyzing the results of a wide variety of research papers. These are considered to be the highest level of evidence within research designs. They systematically evaluate the quality of studies and use methods that limit the bias. This allows us to draw reliable and accurate conclusions. Current reviews don’t do this, however – meaning this particular paper doesn’t offer the most objective view of the effectiveness of low volume HIIT.
With the time taken to warm up and cool down, in addition to the time spent recovering between high-intensity intervals, not all HIIT workouts can be assumed to be more time-efficient than traditional exercises. In this review, the average total time per workout was approximately 40 minutes – no more than 15 minutes of which were active.
This does not mean, however, that HIIT cannot be an alternative to longer workouts – especially given the growing body of evidence showing that it has a number of similar benefits as other types of workouts. Current considerations also suggest that every move counts. Therefore, it can be helpful to focus on the quality (intensity) of the exercise rather than the duration, and find ways to incorporate higher intensity movements into everyday activities to improve our health and fitness.
Matthew Haines is Director of Exercise, Exercise, and Nutrition Science at the University of Huddersfield. This article first appeared on The Conversation