Gender, Physical Activity, and Aging PDF

Preface

As in most areas of human biology, traditional texts examining physical activity and aging have drawn largely upon research conducted with male subjects, since almost no experimental data has compared the course of aging, in general, and effort tolerance, in particular, between women and men. There seem to be several reasons for the gender bias in published research information. Until recently, investigators in human biology were usually men; subjects were often recruited from fellow workers, and constraints of modesty made it easier to examine those of the same sex, rather than to recruit, chaperone, and test female volunteers. Thus, little research was conducted on women. The past decade has seen vigorous efforts to redress this imbalance in many areas of human biology, but there is still a need to examine critically the respective contributions of constitution, environment, and sociocultural influences to observed gender differences in human performance at various ages. Vigorous discussion continues between those who regard the gender gap as determined largely by inherent constitutional factors, and those who hold that it is mainly a manifestation of male exploitation of women, and a related lack of opportunities for women to develop and sustain their physical potential over the life course.

Critical evaluation of the extent and causation of gender differences has particular practical importance when considering issues of aging, physical activity, and health. A large proportion of those who reach an advanced age are women, ⁴ and typically, it is frail elderly women who find difficulty in undertaking the activities of daily living during their final years of life. Does ownership of paired X chromosomes confer more prolonged survival on females, or is the gender difference in life expectancy a cumulative consequence of differing life experiences for women and men? Do women have some lifestyle secret that could be adopted by their male peers in quest of a longer life? And is the apparent success of the female in part an illusion, with the benefits of greater longevity currently offset by a much longer period when physical weakness deteriorates into prolonged disability and institutional residence? ³ One study found that, in extreme old age, there were gender differences in 13 of 28 measures of personality, social relationships, habitual activity, and reported well-being. ⁵ Is a poor quality of life during the final ten years of survival an inevitable consequence of the aging process, or could it be averted by genetic manipulation or adoption of a physically more active lifestyle at an earlier age? Are women forever destined to experience several more years of poor quality life than their male counterparts? How far is the greater prevalence of disability among elderly women a consequence of social disadvantages relative to their male peers (for instance, lesser availability of paid work, lower wages, greater contribution to household labor, less leisure, and less sleep ² )? Could the disturbing current economic projections of the prevalence of extended disability and associated social costs soon be invalidated by genetic therapy or changes in current patterns of living? ¹

Sometimes, beliefs concerning these issues are themselves influenced by gender. ⁶ In order to avoid this dilemma, this book seeks objective rather than doctrinaire answers to the important questions just raised through a critical examination of available literature that has explored interactions between the aging process, gender, and physical activity. In the past few years, research on age-related changes in biological function, physical capacity, and the training responses of women has grown. The time is thus opportune to present a succinct summary of these investigations, exploring the interesting issues of potential gender differences in both the course of aging and responses of the elderly to physical activity. This book undertakes this task, drawing upon the knowledge of leading experts in exercise gerontology.

A necessary starting point for the book is a brief review of the technical problems that arise when attempting to equate biological data between men and women in the face of constitutionally determined differences of size and body composition. Gender comparisons between women and men are often confounded by discrepancies of size, body composition, and fitness between the sexes. Aging also leads to a decrease in stature, complicating analyses of the influence of aging upon various body functions. The opening chapter examines the extent of these two problems and their influence upon published data. It also reviews proposed ways of circumventing problems due to interindividual differences in body size and body composition. An optimal approach is suggested that allows gender comparisons of the aging process and its modification by regular physical activity, with minimal effects from differences in body size and composition.

There is substantial evidence that, in general, both women and men become physically less active as they become older. The second chapter thus examines details of these age-related changes, comparing the activity profiles of women and men, and exploring reasons why habitual physical activity diminishes with age. The contribution of diminished physical activity to the overall loss of functional capacity is discussed, and appropriate genderspecific tactics to motivate women and men to higher levels of physical activity are proposed.

The question arises whether gender-related differences in the rate of aging and interactions with physical activity are a consequence of genetically coded sex differences, or whether they are an expression of socioculturally conditioned differences in lifestyle (particularly physical activity) operating from an early age. Likewise, do genes, environment, or sociocultural factors explain apparent differences in the rate of functional loss and overall longevity between ethnic groups? The next chapter explores the extent to which gender and ethnic differences in the aging process and its interaction with physical activity have an immutable genetic basis, and how far these differences are an expression of potentially modifiable differences in physical environment, lifestyle, and sociocultural factors.

The distinguished panel of contributors continues with a systems approach, exploring the impact of gender and habitual physical activity upon specific physiological, biochemical, and pathological features of the aging process important to physical performance, independence, and quality of life for the old and very old. Age-related cardiorespiratory losses are first examined from this perspective. In most cultures, women live several years longer than men, but this apparent advantage is offset by a longer period of chronic disability, so there is little gender difference in the quality-adjusted life span. One chapter explores why women live longer than men, discussing and comparing factors that lead to loss of independence and poor quality of life in the two sexes. Based on these data, an assessment is made of what changes in lifestyle (particularly an increase of physical activity) could contribute to a reduced risk of chronic disability in both sexes.

Attention is then directed to neuromuscular function, the molecular basis of sarcopenia, and the relative risks of overtraining at various ages. A section on deterioration in metabolic regulation looks at such issues as the effects of gender, physical activity, and aging upon obesity, as well as the prevalence of diabetes mellitus, the weakening and deterioration of bone and joint structures, and alterations in immune and humoral responses among older women and men.

A final chapter considers some implications of the existing situation for health policy, and makes recommendations for change. The growing number of old and very old people, particularly women, in most developed societies poses major problems for support services. The personal, social, and economic costs imposed by likely changes in the numbers and physical abilities of elderly men and women are examined, together with the potential for alleviating such costs by encouraging acceptance of the active lifestyle seen in individuals who age most successfully.

This book should be of interest to all who are concerned with the process of human aging, from physiologists and biochemists and their colleagues in gerontology and geriatric departments to inquiring individuals who sense the advancing hand of time reducing their own functional capacity. The primary readership of this volume will be the growing population of investigators concerned with gerontology and geriatric medicine. However, the topic should also appeal to a broader range of applied scientists interested in the interactions between aging and physical activity, and to those interested in whether current gender differences in human performance have a genetic, constitutional basis, or are attributable largely to sociocultural differences that afford men greater opportunities for physical activity and a satisfying life course.