It’s a common occurrence for anyone who exercises regularly: two people with similar fitness levels can do the same exercise and get completely different results. This is extremely frustrating for the person who can’t seem to improve despite their best efforts.
A group of exercise science researchers at Brigham Young University know the feeling and set out to fix the problem. Good news: they believe they’ve cracked the code.
Newly published research from the team reveals a more efficient way to determine the intensity at which each person should work to achieve the best results. A study published in Journal of Applied Physiology outlines a new system for creating not only personalized workouts, but also “prescribed” workouts that deliver results regardless of an individual’s current health status.
“One day we will be able to prescribe exercise as medicine,” said Jason Gifford, a professor of exercise science at BYU and senior author of the study. “To prescribe a drug, you need to have predictable results for each dose of the drug. We’ve found that the exact same thing applies to exercise.”
The research explains that when exercise is personally prescribed based on what is called “critical strength,” the results show a greater improvement in endurance and greater long-term benefits for the individual. The authors define critical strength as the highest level of our comfort zone. “This is the level at which we can operate for a long period of time before things start to get uncomfortable,” said lead study author Jessica Collins, a former BYU student.
It works like this: Suppose two friends have a similar maximum heart rate. Previous understanding of exercise suggests that if they run together at the same speed, they should have very similar experiences. However, it happens that when these two friends run at a speed of 6 miles per hour, the exercise is easy for one but difficult for the other. These distinct experiences at the same speed and the same percentage of maximum heart rate are because 6 mph is below one friend’s critical power but above the other’s critical power.
When exercise is below a person’s critical power output, their body can compensate for the energy challenge and reach a comfortable and controlled homeostasis. However, when exercise is above critical power, their body cannot fully compensate for the energy demand, resulting in exhaustion.
Traditionally, individualized exercise has been recommended based on a fixed percentage of the maximum rate of oxygen consumption (VO2max) or their maximum heart rate. Collins and Gifford said using “critical strength” is a better way to prescribe exercise because it not only accurately serves athletes and those in great shape, but also serves those who are older or have more sedentary way of life.
“This kind of research helps every person, no matter how active they are right now,” Collins said.
For the study, Collins, Gifford and co-authors recruited 22 participants between the ages of 18-35 who were healthy but showed low levels of fitness. Participants underwent eight weeks of controlled exercise training, where they were randomly assigned to either high-intensity cycling training or moderate-intensity continuous cycling training. Exercise is traditionally prescribed based on an individual’s maximum heart rate, or VO2max.
The researchers found that prescribing exercise based on VO2 Max as a reference point leads to an alarming variability of results. There were participants who benefited greatly from the training period and others who did not, even though the training was customized for them.
They compared this to each individual’s critical strength and found that it accounted for 60% of the variability in their findings. If the exercises were prescribed using critical power as a reference point versus heart rate, the results would vary less, meaning that the workouts would be more effective and beneficial for each participant.
“One of the biggest reasons people don’t exercise as much as they should is because they’ve tried something in the past and it didn’t work out the way they expected it to,” Collins said. “The great thing about basing exercises on critical strength is that we can almost always guarantee the result, allowing us to help people achieve their fitness goals.”
To calculate a person’s critical strength, researchers had participants complete multiple exercise distances (ie, running, cycling) as fast as possible. They then took the average speed and plugged that data into a proprietary formula that determines the relationship between exercise distance and exercise time to arrive at a critical power number. They found that a person’s critical strength can be greatly increased with training, making things that were previously difficult less challenging, less uncomfortable, and less tiring.
“Exercise is so good for you that you’re going to see some benefit no matter what you’re doing,” Gifford said. “This research simply informs people that they can more fully optimize their exercise so that they get more out of it.” We are excited when it becomes more accessible for people to know their personal critical power in the near future.”
Jessica Collins et al, Critical power and work-prime account for variability in endurance training adaptations not captured by V̇O2max, Journal of Applied Physiology (2022). DOI: 10.1152/japplphysiol.00344.2022
Provided by Brigham Young University
Quote: Exercise Science Researchers Point to Method to ‘Prescribe’ Aerobic Exercise as Medicine (2022, Nov. 7), Retrieved Nov. 7, 2022, from https://medicalxpress.com/news/2022-11-science- method-aerobic-medicine.html
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