Published August 15, 2017
A preclinical study by researchers in the Department of Medicine’s Division of Geriatrics and Palliative Medicine has revealed that brief periods of intense physical activity can be safely administered at advanced age and has the potential to reverse frailty.
Published in June in the Journals of Gerontology, Series A, the study is the first to investigate whether a novel, short-session regimen of high-intensity interval training (HIIT) can be safe and effective in older populations.
The study was conducted on two groups of a dozen mice, each 24 months old, which correlates roughly to 65 years old in human terms. All the mice had been sedentary up until that age. A control group remained sedentary while the other group underwent HIIT.
“Although the work is in mice, it is part of our larger program both to understand the determinants of frailty and the best approaches to delay, prevent and even reverse frailty in older people,” says Bruce R. Troen, MD, professor of medicine and chief of geriatrics and palliative medicine.
“We know that being frail or being at risk for becoming frail puts people at increased risk of dying and comorbidity,” says Troen, senior author on the study with Kenneth L. Seldeen, PhD, research assistant professor of medicine, who is first author.
The results were striking, with mice in the HIIT group exhibiting “dramatic” improvements in numerous measurements, including strength and physical performance.
“These results show that it’s possible that high-intensity interval training can help enhance quality of life and capacity to be healthy,” Troen says.
One of the most significant findings was that by the end of the four-month study, five of six mice in the HIIT group found to be frail or pre-frail at baseline improved, and four were no longer frail.
“Those four mice who had exhibited the kinds of deficits that correlate to frailty in humans improved to a completely robust level,” says Troen. “The HIIT actually reversed frailty in them.”
The researchers developed mouse equivalents for measures that assess human frailty — including ways to evaluate grip strength, endurance and gait speed — so that they could establish baseline levels and then compare those with results once the study was complete.
“Because the performance measures for the mice are directly relevant to clinical parameters, we think this program of exercise is quite applicable to humans,” Troen says. “We’re laying a foundation so we can do this in people and so we can understand how to tailor it to individuals so they can successfully implement this.”
Similar to the way that an athletic trainer might individualize a fitness program for a client, the researchers tailored intensity levels to each mouse.
“While the mice are genetically identical, they aren’t phenotypically identical,” Seldeen explains, “so we individually tailored the program to each mouse, first finding out what each one was capable of at baseline, and then increasing or decreasing the intensity depending on the performance of the mouse during the study.”
The 10-minute exercise program involved a three-minute warmup and four intervals of one minute of high intensity and one minute of recovery time on an inclined treadmill. The exercises were done three times a week over 16 weeks. All exercises were well-tolerated by the mice.
The mice that remained sedentary had less muscle mass, strength and endurance than four months before and moved infrequently.
In contrast, in the HIIT group there were dramatic improvements in grip strength, treadmill endurance and gait speed. The mice showed greater muscle mass and an increase in total mitochondria, the energy factories of cells.
“Increased mitochondrial biomass allows you to utilize oxygen more efficiency,” Troen explains. “With HIIT, we saw both mitochondrial increase and an improvement in muscle quality and fiber size in these mice.”
As to why HIIT results in such significant benefits to those who engage in it, Troen says that it has to do with the stress to which it subjects the body.
“Exercise stresses the system, and the body can respond beneficially,” he says. “We believe that the intensity of individualized HIIT provides a more significant but manageable stress, so the body responds more robustly to these short, vigorous periods of exercise.”
“In other words, you get more bang for your buck,” Troen says, noting studies show that most people over the age of 65 do not engage in regular exercise and cite lack of time as the biggest factor.
“There are important issues here because frailty and pre-frailty are associated with poor long-term outcomes,” Troen notes.
Troen says that doesn’t mean that getting rid of frailty cures the diseases one might have, but the hope is that overall quality of life and healthspan can be enhanced.
“The long-term goal is not just to live as many years as possible, but we want to get the most life in our years,” he says. “If we can prevent or even reverse frailty, then I think we’ll be doing a lot of good for a lot of people.”
Troen and Seldeen caution that anyone considering undergoing HIIT should receive clearance from their physician first.
Additional co-authors on the paper are:
The research was funded by the U.S. Department of Veterans Affairs and by the Indian Trail Charitable Foundation Inc., a private foundation that has funded several of Troen’s projects on aging.