With increasing age, there is a gradual loss of muscle mass, and muscles become weaker (McArdle, Vasilaki, and Jackson, 2002). Specific contractile proteins undergo alteration, and contraction itself becomes more disorganized (Larrsson et al., 2001). Age-associated changes in muscle strength occur earlier in women, who also appear to have greater loss of muscle quality (Doherty, 2001). Also, with increasing age, the time it takes to repair damaged tissue increases (Khalil and Merhi, 2000), possibly having implications for high-level physical occupational activities among older persons. Because of age-related loss of muscle strength and cardiac capacity, maximal exercise capacity and oxygen consumption clearly decline with age, even in apparently healthy persons (Fielding and Meydani, 1997). In an excellent review of age and work capacity, de Zwart, Frings-Dresen, and van Dijk (1995) noted that physical work capacity clearly declines with age, but whether physical work demands are different for older versus younger workers has not been well documented. Age-related muscle loss may have an important effect on other organs, such as respiration (Franssen, Wouters, and Schols, 2002), joint function and mobility, and vocal function.
However, while the causes of age-related muscle changes are often uncertain, it is likely that lack of continued physical training (i.e., poor exercise habits or deconditioning) plays an important role (Franssen et al., 2002). Not only may aging decrease the capacity of workers for some exertional tasks, but an increased risk of falls and balance maintenance are possible secondary consequences, suggested to occur among frail elders (Rigler, 1996). However, little research of this issue has been conducted among older workers. Weight-bearing exercise improves muscle glucose and lipid uptake, as well as strength and exercise endurance (Mittendorfer and Klein, 2001), suggesting a possible role for exercise activity in older worker health promotion programs.
Visual functions clearly undergo decrements with increasing age, with important implications for many workplace activities (West and Sommer, 2001). Age-related changes in visual function are often due to a variety of diseases and conditions that have been subject to treatment, such as hyper-tensive retinopathy, diabetic retinopathy, glaucoma, and cataract. Some late-occurring conditions, such as macular degeneration, may be subject to only modest treatment effects. Some of these conditions are related to systemic illnesses or disorders that themselves need detection and treatment in order to help maintain optimal vision. Ocular injuries are a well-recognized occupational hazard, and preventive programs should be part of worker