Neuromuscular performance in a Kansas Mennonite community: age and sex effects in performance.

Abstract

The effects of age and sex on six neuromuscular performance traits are studied in a cross-sectional sample of 559 members of the Goessel, Kansas Mennonite community. Age and sex effects are assessed by stepwise polynomial regression which includes non-linear age terms up to the fourth power. Of the six traits studied only one, Hand Steadiness, fails to show a significant sex difference and only one, Trunk Flexibility, fails to show a significant non-linear trend with age. A general pattern, seen in these traits of accelerating performance decline after age 45 of up to 60%, is found to be consistent with that reported in other studies of the same traits. The consistency of this non-linear aging pattern suggests the presence of a general neuromuscular aging process. Moreover, this process appears likely to be related to a two-stage mechanism inferred from both animal and human studies involving a decline in protein synthesis and a loss of cell mass in nerve and muscle tissue. Diminished ability with regard to muscular strength and neuromuscular performance associated with advancing age is an observation which seemingly has been well documented. Pioneering investigations by Quetelet (1835) revealed declines of 35 to 40% in the strength of various muscle groups in men between the ages of 25 and 60. Later in the 19th century, large studies guided by Galton showed a pattern of decline with age that was similar for several aspects of human physiology and neuromotor performance including grip strength (Ruger and Stoessiger, 1927; Elderton and Moul, 1928) and reaction time (Koga and Morant, 1923). Subsequent analyses of these phenomena have, however, been sporadic and have usually focused on only one or two aspects of human neuromuscular performance. The most extensively studied traits are muscular strength and stimulus-response characters such as reaction time. Rarely has a broad range of performance traits been investigated in a single population. department of Psychiatry, Washington University School of Medicine and the Jewish Hospital of St. Louis, St. Louis, MO 63178. 2Laboratory of Biological Anthropology, University of Kansas, Lawrence, KS 66045. 3Department of Anthropology, University of Kansas, Lawrence, KS 66045. 4Department of Health, Physical Education and Recreation, University of Kansas, Lawrence, KS 66045. Human Biology, May 1985, Vol. 57, No. 2, pp. 197-211. © Wayne State University Press, 1985 This content downloaded from 157.55.39.170 on Tue, 26 Jul 2016 05:11:42 UTC All use subject to http://about.jstor.org/terms 198 E. J. Devor , M. H. Crawford and W. Osress In this paper we present the results from a study on the effects of age and sex on six neuromuscular performance traits. These traits represent a range of performance including strength, flexibility, neuromotor control, and response to external stimuli. Our results indicate that significant sex differences exist in five of the six traits and that significant age effects are present in all six. Moreover, the pattern of decline in performance with age is similar in all traits studied, regardless of sex. This result suggests that the process of aging impinges on the human neuromuscular system in a uniform manner. Materials and Methods Cross-sectional data on at least one of six neuromuscular performance traits were collected in the field from 559 members of the Alexanderwohl Mennonite congregation living in and around Goessel, Kansas (see Crawford and Rogers, 1982). The total sample was composed of 264 men, aged 15 to 96 years, and 295 women, aged 13 to 95 years. All subjects were voluntary participants in a University of Kansas study of aging and longevity. The age and sex distribution of these subjects, as well as basic physical characteristics, are presented in Table 1. As may be seen in this