The thesis project for a UND graduate student in kinesiology has been published by Sports Medicine, a top-ranking journal.
Trevor Dufner is the lead author of the study, which brought together one of the largest datasets on handgrip strength ever assembled to estimate trends among adults in 14 high- or upper-middle-income countries. Handgrip strength is significantly associated with current and future health, Dufner said, and that means broad changes in handgrip strength may indicate changes in the health of the adults in those countries.
Along with his co-authors, who include UND Kinesiology faculty members John Fitzgerald and Grant Tomkinson, Dufner analyzed data from 2.5 million adults. The results: In several of the countries, there have been slight but consistent declines in adult handgrip strength since about the year 2000. But in the United States, Dufner and his co-authors didn’t see much of a change.
“So that’s a good-news story for adults in America, because it indicates that the health of Americans probably hasn’t changed a lot in the past 40 or 50 years,” Dufner said. Meanwhile, “in some of the other high-income countries, it looks like it’s very gradually tracking down.”
Dufner, native of Christine, N.D., south of Fargo, graduated with his master’s degree from UND in the spring. Next fall, he’s planning on continuing his graduate studies at the University of Central Florida, where he’ll pursue a kinesiology Ph.D.
The fact that Dufner’s already been published by the No. 2-ranked sports science journal in the world will help, Tomkinson said.
“There are very few faculty – let alone graduate students – who are published in a journal with such prestige,” Tomkinson said.
“Particularly for a journal like Sports Medicine, which has, I believe, a rejection rate of about 98 percent. Their acceptance means Trevor has analyzed an important and topical issue, and in a way that will have reach even overseas.
“In short, this is an outstanding effort by Trevor,” Tomkinson said.
Tracking key measures over time
Dufner’s work is in line with a research specialty that the Kinesiology department has developed in recent years, which is analyzing trends in key muscular-strength and -endurance measures that are associated with overall health. For example, a study last year analyzed data from 2.2 million children and adolescents, and found gains in handgrip strength worldwide. And a study earlier this year looked at trends in standing broad jump performance among U.S. youth, and found a small increase (about 13 centimeters or 5 inches) between 1911 and 1990.
Importantly, these studies often suggest what some countries or populations might learn from others that are doing well, Tomkinson said. “So for example, in older Japanese adults, their fitness measures tend to be tracking up, while most of what we’re seeing elsewhere is tracking down,” he said.
“They’re living longer in Japan, too. They’re living healthier for longer.”
“And so, you try to look at what the Japanese are doing, including factors such as their government-issued Physical Activity Guidelines, which are far stricter than the international guidelines or the ones that we have here in the U.S.” And if research confirms the influence of those factors, “then you think, ‘Maybe there are some lessons that we and others can learn.’”
Back when Dufner was planning this latest study of grip-strength trends, he and his colleagues thought he’d find substantial declines. “You think of prior generations doing so much more with their hands, maybe being more blue-collar oriented,” Dufner said. “So, we thought we’d see at least a moderate decrease in handgrip strength over time.
“And we really didn’t consistently see that. It was a surprise to us,” he said.
Instead, the team typically found slight declines since 2000. In some countries, they also saw slight improvements or no change, the latter being the case in the United States. A slight decline is still a decline, and in the countries where that showed up, it may suggest a corresponding decline in adults’ functional capability and health, Dufner noted.
Perhaps as important, the study confirms the usefulness of handgrip strength as a quick, inexpensive and reliable marker of population health.
Low-income countries should consider tracking handgrip strength and similar measures as a cost-effective health surveillance strategy, the study suggests.
To conduct the study, Dufner and his colleagues searched the literature for studies that measured adults’ grip strength. Then the team extracted the data from those studies, combined the averages by country and analyzed them.
“One thing I want to make clear is that I couldn’t have done this alone,” Dufner said. Tomkinson, Fitzgerald and Justin Lang, the other co-author and a Canadian public-health researcher, “all helped me so much throughout the entire process.”
And now that the work is done and the study has been published, “it’s awesome,” Dufner said with a laugh.
“When it’s all said and done, getting into a journal like Sports Medicine makes me feel really good. I thank my three co-authors over and over for their help and what they’ve taught me.”