The team’s research has revealed a more effective way to determine each person’s workout intensity for best results.
The team hopes to develop exercise regimens using what is known as “critical force.”
Anyone who exercises frequently is familiar with the phenomenon of two individuals with the same level of fitness performing the same exercise with vastly different results. It’s very frustrating for individuals who seem to be making no progress despite their best efforts.
Exercise science researchers at Brigham Young University have been trying to address this question because they are familiar with this feeling. Good news. They think they understand the code.
The team’s recently published research reveals a more practical way to figure out what level of intensity each individual should exercise for best results.Research published in Journal of Applied Physiology Describes a new system for creating “prescribed” workouts that deliver results regardless of an individual’s current health status.
“Someday we will be able to prescribe exercise-like drugs,” said Jayson Gifford, a professor of exercise science at BYU and lead author of the study. “Prescribing drugs requires predictable results with each dose of the drug.
According to this study, personally prescribed exercise based on what is known as “critical power” significantly improves endurance and provides longer lasting personal gains. is defined as the highest level of comfort zone. “This is the level at which we can perform for an extended period of time before things start to feel uncomfortable,” said Jessica Collins, lead author of the study and former BYU graduate student.
It works like this: Suppose two friends have the same maximum heart rate. Prior knowledge of exercise means that if they ran at the same pace together they should have very similar experiences. If so, one exercise is simple, but the other can be difficult. These discrepancies in experiences at the same speed and percentage of maximum heart rate are due to the fact that 6 mph is below one friend’s critical power and above the other.
When exercise falls below a person’s power limit, the body is able to compensate for the lack of energy and reach a comfortable and controlled homeostasis. However, when exercise exceeds critical power, the body cannot fully meet its energy needs, leading to fatigue.
Traditionally, personalized exercise recommendations have been based on a fixed percentage of maximum oxygen consumption (VO2 Max) or maximum heart rate. Collins and Gifford said that using “critical power” is a better way to prescribe exercise. Because this is not only exactly useful for athletes and people in good physical condition, but also for the elderly and those with a sedentary lifestyle.
“This kind of research is useful for all kinds of people, regardless of how active they are right now,” Collins said.
For this study, Collins, Gifford, and co-authors recruited 22 participants aged 18-35 who were in good health but had low fitness levels. subjects underwent 8 weeks of supervised exercise training, randomly assigned to one of the continuous bicycle trainings. Traditionally, exercise was prescribed based on an individual’s maximum heart rate or VO2 Max.
Researchers have found that prescribing exercises using VO2 max as a reference point produces surprising variability in results. Although the training was personalized, some participants benefited greatly from the training period and others did not. They compared this to each individual’s critical power and found that he accounted for 60% of the variability in the findings. When exercises were prescribed using critical power as a reference point for heart rate, results were less variable, meaning the training session was 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 as expected,” says Collins. “The great thing about critical power-based exercises is that they almost always deliver guaranteed results, which can help people reach their fitness goals.”
To calculate a person’s critical power, researchers had participants complete multiple distances of exercise (i.e., running, cycling) as quickly as possible. We then took the average velocity and inserted that data into our own formula to determine the relationship between exercise distance and exercise time, and to calculate the critical power number. They found that a person’s critical force was greatly increased by exercise training, making things that were previously difficult less difficult, causing less discomfort, and reducing fatigue.
“Exercise is so good for your body that whatever you do will do you some good,” Gifford said. “There is much more to be gained from this research just by letting people know that their exercises can be more fully optimized. I look forward to
See: “Critical power and work prime explain variability in endurance training adaptations not captured by V̇.o2 maxJessica Collins, Olivia Leach, Abigail Dorff, Jessica Linde, Jason Coffide, Megan Sherman, Megan Profitt, Jason R. Gifford, October 6, 2022 Journal of Applied Physiology.
DOI: 10.1152/japplphysiol.00344.2022
