(Blacksburg, Va., Jan. 15, 2001) Among healthy people, muscle strength decreases by only about five percent between the ages of 25 and 40. But between the ages of 50 and 60, muscle strength decreases by about 20 percent.
To many of us this change is noticeable only while we're working out at the gym or rearranging furniture, but it's a matter of critical importance to the millions of aging workers in physically demanding jobs.
It's also important to Maury Nussbaum, assistant professor of industrial and systems engineering (ISE) at Virginia Tech, who has received a $425,000 grant from the National Institute of Occupational Safety and Health (NIOSH) to study the effects of age on work capacity. "Physically demanding work isn't going away," Nussbaum remarks. During the mid-1990s, he notes, about 12 percent of workers were over 55 years of age and that is expected to rise to 15 percent within five years. Many of these workers are doing the same sort of physical work -- from assembly-line jobs to heavy construction -- that they did in their 20s.
"By 2020, about 52 million people in the U.S. will be over 65," he notes. "Many workers are staying on the job longer, and many industries have increased the average age of workers doing physically demanding jobs. We need to learn what older workers are capable of doing during complex exertions."
Nussbaum works in ISE's Human Factors Engineering program. "I try to learn how the workplace affects workers and how to design workstations to maximize work capacity and minimize risk," he says.
There's evidence of an intriguing twist to the fact that muscle strength is diminished with age, Nussbaum notes. As we age, we also develop more endurance. "Despite being weaker, older workers seem to have more resistance to fatigue," he says.
Muscles are composed of two types of fibers -- "fatigue-able" and fatigue-resistant. The fatigue-able fibers provide maximum strength or force, and we experience a selective loss of these fibers as we age. So, Nussbaum explains, we are left with more of the fatigue-resistant fibers.
"If young and older workers are performing the same tasks, the older ones are typically working at a higher proportion of their capacity," he says. "Companies realize that older workers also tend to be more reliable and experienced."
With all of this in mind, Nussbaum and Laura Wojcik, a former member of the engineering science and mechanics faculty at Virginia Tech, developed a proposal for NIOSH funding. "Our central hypothesis is that older, more experienced workers would have greater endurance on the job if we could learn how tasks can be adjusted to their work capacity," Nussbaum says.
To test this hypothesis, Nussbaum will recruit groups of young workers -- 18 to 24 years old -- and older workers -- 55 to 65 -- from the Blacksburg, Va. area and have them perform sets of exercises. As they exercise, they'll be connected to mechanisms that will measure force, torque and muscle activity. The test groups will perform intense exercises for short periods of time and light exercises for prolonged periods.
Wojcik, who left Virginia Tech in December 2000 to take a research position with industry, will act as a consultant on the project.
The project also is aimed at evaluating realistic tasks. "Lots of research has been done using constant force and posture," Nussbaum notes, "but in the real world people are moving around." Another goal is to assess the levels of fatigue that the subjects experience. "We need to see if there are simple measures that can be developed for companies to use in alleviating fatigue so that workers can perform to their maximum capacity," he says.
If the theories behind the project can be proven, Nussbaum believes, companies can learn how to modify the workplace and tasks so that older workers can be more effective and stay in their jobs longer.
"Many companies already are adjusting tasks to accommodate older workers," he says. "We hope this research will help more companies make adjustments and overcome their resistance to hiring and keeping older workers."
Nussbaum is involved in other work-related projects. He is developing guidelines on assembly-line injury and performance for a major auto manufacturer. With funding from the U.S. Army Research Laboratory, he is studying the relationship between the physical and mental demands of certain tasks.
Another project focuses on the effects of work conditions on fatigue. One factor he is studying, for example, is how periods of rest affect both endurance and fatigue.
Fatigue and work-related injuries -- particularly of the spine -- are of special interest to Nussbaum, who has created a computer program that simulates and measures the effects of various motions and stresses on the spine and supporting muscles. "The assumption is that reducing fatigue will reduce injury as well as increasing efficiency," he remarks. "Industry is very receptive to this type of research."