Gender, Physical Activity, and Aging

“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.”

I’ve read books dealing with related stuff before, but from different angles not involving much stuff about gender differences.

The book spends a lot of time on gender-differences related to the aging process and how this stuff relates to stuff like physical activity and other environmental factors as well as genetics. Some of the chapters are quite easy to read, others are significantly more technical – chapter four occasionally contained stuff which was at least borderline beyond me (unless you’ve learned by heart stuff like what’s covered here and here you’ll either be at least somewhat lost or you’ll need to look up some stuff along the way), but I read on anyway (occasionally rewatching a Khan video…) and even if some of the finer details sometimes elude you you’ll probably learn some stuff. I thought the first parts of chapter 3 were quite weak compared to the stuff on those topics I’ve read elsewhere (can’t remember where – Whitbourne perhaps? Razib Khan?). On a general note I believe I’m leaning towards a 3 star goodreads rating at this point – I’ve read roughly half the book. There’s a lot of stuff and it’s a well documented book (aside from the intro chapter and chapter 5, all chapters so far have had more than 100 references – chapter 3 e.g. has more than 250 references), but some of the topics covered I don’t find to be very interesting, and e.g. the stuff on motivation in chapter 2 is way too theoretical to be of any use in an applied setting (so why are they wasting time writing about it?). I added a ‘pure speculation’ note in the margin at one point. But again, there’s a lot of good stuff – some stuff from the first half of the book:

“On average, a larger fraction of total body mass is fat and bone structure is lighter in women than in men; likewise, most older individuals accumulate body fat […] Gender differences in muscle strength and maximal aerobic power become much smaller if values are expressed per unit of lean body mass. A lean mass adjustment may be appropriate when comparing specific aspects of muscle and cardiac function between women and men, young and old, or indigenous and modern populations. But during most activities of normal daily life a person must displace the entire body mass rather than just lean tissue; if the type of activity to be performed requires a size adjustment, then total body mass is the most appropriate unit of reference.25 […] Fat is a poor conductor of heat, and if the layer of subcutaneous fat is increased […] then the person concerned must direct an increased fraction of total cardiac output to skin rather than working muscles when carrying out heavy physical work in a warm environment.27 This reduces the external power output for a given maximal oxygen intake […]

From a physiological point of view, there is an important gender difference in average blood hemoglobin concentration. […] The lower average figure in females reflects mainly physiologic influences […] Given the predominantly biological basis of the hemoglobin
differential, the gender gap seems likely to be small after menopause;37 at this stage, values remain relatively constant in women, but tend to decrease in men. […] The maximal oxygen content of unit volume of blood is stoichiometrically related to the hemoglobin concentration.20 Thus, for each liter of blood pumped by the heart, a woman necessarily transports approximately 10% less oxygen than a man, at least prior to menopause. […]

Over a 3-month period, even a moderate training program can augment muscle strength and maximal aerobic power by 20% or more, 25,26 — equivalent to a reversal of approximately 20 years of normal aging.26 It is thus important that any gender comparisons of the aging process be based on individuals who begin with a similar initial training status and are pursuing similar patterns of habitual physical activity. […] laboratory-measured indices of physical fitness (such as treadmill endurance time) bear a closer relationship to health outcomes than do questionnaire assessments [my emphasis, US] […]

One U.S. study attributed as much as a half of variance in the age-linked decrease in relative aerobic power to a combination of a decrease in habitual physical activity and an increase in body mass.12 In order to see the true influences of gender and aging upon the primary variable, it is thus desirable to focus attention on a population sample where habitual physical activity and body fat content have remained constant over the individual’s life span. […]

it has […] been recognized for many years that the aging process actually shows some curvilinearity. […] For example, women show a sharp acceleration in the rate of bone mineral loss during the five years around the age of menopause;18 in men, there is an accelerating loss of lean tissue after retirement […] In women, functional losses accelerate with the distinct end point of menopause, but in men the process begins at a later age, and develops more gradually […]

Two robust findings from population-based surveys are that older adults are less active than younger adults, and older women are less active than older men. […] Physical activity is associated with physical function, even in those living with chronic disease52 and is inversely related to disability in women.53 A low level of physical activity is considered a risk factor for functional decline in older adults.54,55 […]

Older adults have an average of 11.4 contacts per year with a physician or health care provider,1 […]

randomized controlled exercise trials with older adults have shown that exercise adherence is comparable or superior for home-based compared to group-based exercise.122-124 […] older adults are more likely to cite the health benefits of physical activity as a motivation for exercise than are younger adults. […] perceived exercise benefits or outcome expectations are positively associated with physical activity participation in older women.82,96,98,109,128 […]

Official statistics show that women have had a substantially longer average survival than men in all countries of the world throughout the past century […] Lifestyle and other environmental factors plainly modulate any underlying effect of constitution, since gender discrepancy increased very substantially in almost all countries during the first two thirds of the 20th century (Table 3.1). In the U.S., for example, the gender differential increased from 5.8% in 1900 to 9.6% in 1990. […] Gains in life expectancy during the present century have been much larger in women than in men.206,236 Thus, a large fraction of the elderly population and an even larger fraction of those who are very old are now women. […] Although women currently have a much longer average survival than men, many aspects of function such as aerobic power and muscular strength deteriorate at a similar absolute rate in the two sexes […] Thus, women face a substantially longer period than men when their level of function is insufficient to undertake instrumental and other activities of daily living43,210,224 […] Indeed, their active life expectancy112 may be no greater than that of their male counterparts. […] In the U.S., the total number of disabled life years averages 10.8 years for men and 14.0 years for women,223 and in some countries the gender discrepancy in chronic disability is even larger.” […]

“the major effect of genotype is probably in terms of increasing an individual’s susceptibility to various causes of disability and
premature death. […] In general, women have fewer material resources than men during old age.132 They are much more likely to be living on their own,16 and thus tend to receive less psychological support than men.42,149,167 They are also more likely to be disabled. In general, disability increases social isolation […] Growing evidence suggests that physical activity helps to maintain social contacts, enhances mental health, and sustains cognitive ability in the very old.210 […]

Gender differences in the prevalence of cigarette smoking have in the past explained much of the shorter average life span of the male. Indeed, after allowing for a somewhat greater incidence of traumatic deaths among men, there is almost no gender difference in life expectancy among nonsmokers.155 Now that the prevalence of smoking also shows little sex difference, a progressive equalization of average life span between men and women can be anticipated.173 [my emphasis, US] […]

Particularly in the final years of life, the greatest dividend from regular physical activity may be an increase in the individual’s functional capacity and thus quality of life […] rather than an extension of life span.209 […] Because women generally have a smaller functional margin than men, they are likely to show a larger gain in quality of life as a result of participating in a regular physical activity program […]

Specific genes can now be identified that increase the risk of various chronic diseases, affecting an individual’s quality of life and survival prospects. Furthermore, the frequency of occurrence of such genes in some instances differs between the two sexes. Nevertheless, various environmental challenges exert a powerful influence, both in their own right and as the reason why adverse genetic characteristics become manifest. The gender difference in survival thus seems determined almost entirely by environmental factors, with cigarette smoking playing a dominant role. […]

there is typically a ten-year delay in the onset of coronary symptoms for women compared to men […]

Here’s a quote from chapter 4 I picked because I figured it’d convey part of why this chapter may be hard to understand for some readers:

“With advancing age, strategies used to augment cardiac output during exercise shift from codependence on catecholamine-mediated inotropic, chronotropic, and volumetric means, to greater dependence on changes in ventricular end-diastolic volume via the Frank–Starling mechanism. […] The key signaling proteins involved in both the amplification and integration of extracellular signals in the myocyte (from the sarcoplasmic reticulum to the intracellular effectors) include β-adrenergic receptors, G proteins, and adenyl cyclase. […] Variability in the R-R interval, used as an index of parasympathetic tone, is augmented with aerobic training …”

Back to the ‘not-that-hard-to-understand-stuff’:

Exercise training which increases and augments the ventilation threshold by 10 to 15% may increase the time to fatigue by as much as 180% when exercising at a fixed intensity. Improvement in submaximal aerobic exercise performance is believed to result in part from change in skeletal muscle metabolism. These changes in submaximal performance have a profound effect on the ability of older people to function in daily life.99 [my emphasis, US] […] Aging of the cardiorespiratory system is not due to breakdown in a single step of oxygen conductance from the atmosphere to exercising muscles. Rather, there are physiological changes in each of the series of resistors. […] it is apparent that aging affects each step in the delivery of oxygen, often with differing effects across genders. Many of these changes are slowed or reversed by exercise training […]

It has been widely demonstrated that greater physical activity is associated with a reduced all-cause mortality in men. However, this relationship has been studied less frequently in women. […] Physical activity and longevity were investigated by Paffenbarger et al.1 in 17,000 male Harvard alumni aged 35 to 74 years. With physical activity assessed by questionnaire in the follow up, it was estimated that those expending greater than 8.4 megajoules per week in exercise (walking, stair climbing, sports play) had a 25 to 30% lower mortality rate than those with lower weekly energy expenditures. Paffenbarger and colleagues2,3 also showed that physical activity participation (in the form of moderately vigorous sports play) initiated in middle-age was independently associated with a 23% lower all-cause death rate …”


August 1, 2013 Posted by | Biology, Books, Data, Demographics, Medicine | Leave a comment