ply increasing signal strength, e.g., shouting over noise, results in diminishing returns (Crocker, 1997).

Design Interventions to Accommodate Physical Changes

The Canada Fitness Survey (Kozma, Stones, and Hannah, 1991) showed cross-sectional linear decline on most fitness and flexibility variables with age, though sometimes gender interacted with age; men typically showed faster decline than women. A main effect on fitness and flexibility was shown for activity level as well, an effect that did not interact with age. Because of changes in the cohort structure of the workforce, particularly the shifts in minority composition from large influxes of Hispanic workers, current data on anthropometry (e.g., Kroemer, 1997; Peebles and Norris, 2003; Steenbekkers and van Bijsterveldt, 1998) may not predict characteristics of future cohorts of older workers. Such data are useful for designing functional workplaces. Anthropometric data typically encompass size, strength, and flexibility ranges for people’s bodies. An example would be extent of reach from a seated position. If a given worker has a shorter-than-average reach, he or she may become inadvertently handicapped and possibly suffer musculoskeletal disorders (MSDs) in work environments designed for those with a longer reach.

Arthritis, which affects flexibility and dexterity, increases in prevalence with age and affects older women more than men (Verbrugge, Lepkowski, and Konkol, 1991). Arthritis can make many manual tasks difficult to perform. Women tend to be differentially employed in clerical positions that require typing (Chan et al., 2001), implying that some accommodations may be particularly critical for them. Also, arthritis has recently been shown to be a risk factor for occupational injury, for instance, in farmers who are injured by livestock (Sprince et al., 2003).

Changes in the mechanisms supporting balance may be an important factor to consider, given the data on age-related increases in death from falls in construction and manufacturing industries (Agnew and Suruda, 1993; Bailer et al., 2003).

Shephard (1995) reviewed research on physically demanding work and suggested changes to accommodate older workers (women and men). A central concern is the likelihood of fatigue in a physically demanding task that exceeds a threshold for cardiorespiratory capacity of 33 percent maximal oxygen intake. If aerobic capability declines from about 12 to 14 metabolic units (METS) in young adults to 7 METS in the average 65-year-old, many older workers would not be expected to be able to perform other than light physical work. Given that women typically average two-thirds the aerobic power of men at all ages, older women are most at risk for excessive demands from physically demanding jobs.

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