James S. Skinner

Exercise and Physical Activity for Older Adults

The purpose of this Position Stand is to provide an overview of issues critical to understanding the importance of exercise and physical activity in older adult populations. The Position Stand is divided into three sections: Section 1 briefly reviews the structural and functional changes that characterize normal human aging, Section 2 considers the extent to which exercise and physical activity can influence the aging process, and Section 3 summarizes the benefits of both long-term exercise and physical activity and shorter-duration exercise programs on health and functional capacity. Although no amount of physical activity can stop the biological aging process, there is evidence that regular exercise can minimize the physiological effects of an otherwise sedentary lifestyle and increase active life expectancy by limiting the development and progression of chronic disease and disabling conditions. There is also emerging evidence for significant psychological and cognitive benefits accruing from regular exercise participation by older adults. Ideally, exercise prescription for older adults should include aerobic exercise, muscle strengthening exercises, and flexibility exercises. The evidence reviewed in this Position Stand is generally consistent with prior American College of Sports Medicine statements on the types and amounts of physical activity recommended for older adults as well as the recently published 2008 Physical Activity Guidelines for Americans. All older adults should engage in regular physical activity and avoid an inactive lifestyle.

PROGRESSIVE VS SINGLE-STAGE TREADMILL TESTS FOR EVALUATION OF CLAUDICATION

The reliability of claudication pain and the metabolic and hemodynamic measurements of the lower limbs of patients with stable peripheral vascular occlusive disease (PVOD) were compared during and following single-stage (S) and progressive (P) treadmill tests. Ten patients (69.8 +/- 1.8 yr; X +/- SE) walked to maximal claudication pain twice a month for 4 months. Patients walked at 1.5 mph up a 7.5% grade (S test) and at 2 mph on a 0% grade, increasing by 2% every 2 min (P test). Distance walked to the onset of claudication pain (CPD) and maximal walking distance (MWD) were recorded. Foot transcutaneous oxygen tension (TcPO2) was measured before, during, and after exercise, while ankle systolic blood pressure (SBP) and the ankle-to-brachial SBP index (ABI) were measured before and after exercise. Intraclass correlation coefficients (R) of CPD and MWD during S tests were R = 0.53 and R = 0.55, respectively. In contrast, the respective R values during P tests were R = 0.89 and R = 0.93. Higher R values of foot TcPO2 were also obtained during and following P tests, while ankle SBP and ABI were highly reliable following both tests. It is concluded that the severity of PVOD is better assessed by P treadmill tests because clinical measurements are more reliable during exercise and recovery.

The effect of sex, age and race on estimating percentage body fat from body mass index: The Heritage Family Study.

Objective: To study the effects of sex, age and race on the relation between body mass index (BMI) and measured percent body fat (%fat).Design: Cross-sectional validation study of sedentary individuals.Subjects: The Heritage Family Study cohort of 665 black and white men and women who ranged in age from 17 to 65 y.Measurements: Body density determined from hydrostatic weighing. Percentage body fat determined with gender and race-specific, two-compartment models. BMI determined from height and weight, and sex and race in dummy coded form.Results: Polynomial regression showed that the relationship between %fat and BMI was quadratic for both men and women. A natural log transformation of BMI adjusted for the non-linearity. Test for homogeneity of log transformed BMI and gender showed that the male–female slopes were within random variance, but the intercepts differed. For the same BMI, the %fat of females was 10.4% higher than that of males. General linear models analysis of the womens data showed that age, race and race-by-BMI interaction were independently related to %fat. The same analysis applied to the mens data showed that %fat was not just a function of BMI, but also age and age-by-BMI interaction. Multiple regression analyses provided models that defined the bias.Conclusions: These data and results published in the literature show that BMI and %fat relationship are not independent of age and gender. These data showed a race effect for women, but not men. The failure to adjust for these sources of bias resulted in substantial differences in the proportion of subjects defined as obese by measured %fat.

Familial resemblance for VO2max in the sedentary state: the HERITAGE family study

This study investigates the familial resemblance of maximal oxygen uptake (VO2max) based on data from 86 nuclear families of Caucasian descent participating in the HERITAGE Family Study. In the current study, VO2max was measured twice on a cycle ergometer in 429 sedentary individuals (170 parents and 259 of their offspring), aged between 16 and 65 yr. The VO2max was adjusted by regression procedures for the effects of 1) age and sex; 2) age, sex, and body mass; and 3) age, sex, body mass, fat mass, and fat-free mass, as determined by underwater weighing. Evidence for significant familial resemblance was observed for each of the three VO2max phenotypes. Spouse, sibling, and parent-offspring correlations were significant, suggesting that both genetic and environmental factors contribute to the familial resemblance for VO2max. Maximal heritability estimates were at least 50%, a value inflated to an undetermined degree by nongenetic factors. The hypothesis of maternal inheritance, with the fathers contribution being environmental, was also found to fit the data with estimates of maternal heritability, potentially associated in part with mitochondrial inheritance, reaching about 30%. These results suggest that genetic and nongenetic factors as well as maternal influences contribute to the familial aggregation of VO2max in sedentary individuals.

Targeting the Metabolic Syndrome with Exercise: Evidence from the Heritage Family Study

PURPOSE To determine the efficacy of exercise training in treating the metabolic syndrome. METHODS The sample included 621 black and white participants from the HERITAGE Family Study, identified as sedentary and apparently healthy (no chronic disease or injury). The metabolic syndrome was defined as having three or more risk factors according to the guidelines of the National Cholesterol Education Program, including elevated waist circumference, blood pressure, triglycerides, blood glucose, and low HDL cholesterol. The presence of the metabolic syndrome and component risk factors were determined before and after 20 wk of supervised aerobic exercise training. RESULTS The prevalence of the metabolic syndrome was 16.9% in this sample (105/621) of apparently healthy participants. Of the 105 participants with the metabolic syndrome at baseline, 30.5% (32 participants) were no longer classified as having the metabolic syndrome after the exercise training. Among the 32 participants who improved their metabolic profile, 43% decreased triglycerides, 16% improved HDL cholesterol, 38% decreased blood pressure, 9% improved fasting plasma glucose, and 28% decreased their waist circumference. There were no sex or race differences in the efficacy of exercise in treating the metabolic syndrome: 32.7% of men, 28.0% of women, 29.7% of black, and 30.9% of white participants with the metabolic syndrome were no longer classified as having the syndrome after training. CONCLUSION Aerobic exercise training in patients with the metabolic syndrome can be useful as a treatment strategy and provides support for a role for physical activity in the prevention of chronic disease.

Race, Visceral Adipose Tissue, Plasma Lipids, and Lipoprotein Lipase Activity in Men and Women: The Health, Risk Factors, Exercise Training, and Genetics (HERITAGE) Family Study

Abdominal obesity is associated with numerous metabolic alterations, such as hypertriglyceridemia and low levels of high density lipoprotein (HDL) cholesterol. However, compared with abdominally obese white individuals, abdominally obese black individuals have been characterized by higher plasma HDL cholesterol levels, suggesting that the impact of abdominal fat accumulation on the lipoprotein-lipid profile may differ among ethnic groups. Therefore, we have compared the associations between body fatness, visceral adipose tissue (AT) accumulation, and metabolic risk variables in a sample of 247 white men and 240 white women versus a sample of 93 black men and 143 black women. Although no difference in mean total body fatness was found between the 2 race groups, white men had higher levels of visceral AT than did black men (P<0.001). Despite the fact that black women had a greater body fat content than did white women, black women had levels of visceral AT that were similar to those of white women, suggesting a lower susceptibility to visceral obesity in black women. This lower accumulation of visceral AT in blacks was accompanied by significantly reduced apolipoprotein B concentrations and ratios of total cholesterol to HDL cholesterol as well as higher plasma HDL cholesterol levels (P<0.05) compared with those values in whites. Irrespective of sex, higher postheparin plasma hepatic lipase (HL) and lower lipoprotein lipase (LPL) activities were found in whites, resulting in an HL/LPL ratio that was twice as high in whites as in blacks (P<0.005). Although differences in lipoprotein-lipid levels were noted between whites and blacks, results from multiple regression analyses revealed that after control for morphometric and metabolic variables of the study (body fat mass, visceral AT, LPL, HL, and age), ethnicity had, per se, only a minor contribution to the variance in plasma lipoprotein levels. Thus, our results suggest that the higher plasma HDL cholesterol levels and the generally more cardioprotective plasma lipoprotein profile found in abdominally obese black versus white individuals are explained, at least to a certain extent, by a lower visceral AT deposition and a higher plasma LPL activity in black individuals.

Aims, design, and measurement protocol

The HERITAGE family study (HEalth, RIsk factors, exercise Training And GEnetics) will document the role of the genotype in the cardiovascular, metabolic, and hormonal responses to aerobic exercise training. A consortium of five universities in the United States and Canada are involved in carrying out the study. A total of 90 Caucasian families and 40 African-American families with both parents and three or more biological adult offspring are being recruited, tested, exercise-trained in the laboratory with the same program for 20 wk, and re-tested. Oxygen uptake, respiratory exchange ratio, blood pressure, heart rate, cardiac output, blood lactate, glucose, and free-fatty acids are measured during exercise, and maximal oxygen uptake is determined before and after training. Plasma lipids, lipoproteins and apoproteins, glucose and insulin response to an intravenous glucose load, plasma sex steroids and glucocorticoids, and body fat and fat distribution are assessed. Dietary and activity habits and other life style components are assessed by questionnaires, prior to, during, and after training. A variety of genetic analyses will be undertaken, including heritability studies and major gene effects, for each phenotype and its response to regular exercise. Cell lines are established, and DNA sequence variation at a variety of molecular markers will be determined for association and linkage studies.

Adverse Metabolic Response to Regular Exercise: Is It a Rare or Common Occurrence?

Background Individuals differ in the response to regular exercise. Whether there are people who experience adverse changes in cardiovascular and diabetes risk factors has never been addressed. Methodology/Principal Findings An adverse response is defined as an exercise-induced change that worsens a risk factor beyond measurement error and expected day-to-day variation. Sixty subjects were measured three times over a period of three weeks, and variation in resting systolic blood pressure (SBP) and in fasting plasma HDL-cholesterol (HDL-C), triglycerides (TG), and insulin (FI) was quantified. The technical error (TE) defined as the within-subject standard deviation derived from these measurements was computed. An adverse response for a given risk factor was defined as a change that was at least two TEs away from no change but in an adverse direction. Thus an adverse response was recorded if an increase reached 10 mm Hg or more for SBP, 0.42 mmol/L or more for TG, or 24 pmol/L or more for FI or if a decrease reached 0.12 mmol/L or more for HDL-C. Completers from six exercise studies were used in the present analysis: Whites (N = 473) and Blacks (N = 250) from the HERITAGE Family Study; Whites and Blacks from DREW (N = 326), from INFLAME (N = 70), and from STRRIDE (N = 303); and Whites from a University of Maryland cohort (N = 160) and from a University of Jyvaskyla study (N = 105), for a total of 1,687 men and women. Using the above definitions, 126 subjects (8.4%) had an adverse change in FI. Numbers of adverse responders reached 12.2% for SBP, 10.4% for TG, and 13.3% for HDL-C. About 7% of participants experienced adverse responses in two or more risk factors. Conclusions/Significance Adverse responses to regular exercise in cardiovascular and diabetes risk factors occur. Identifying the predictors of such unwarranted responses and how to prevent them will provide the foundation for personalized exercise prescription.

Blood lipid response to 20 weeks of supervised exercise in a large biracial population: The HERITAGE family study

We studied the effects of 20 weeks of supervised cycle-ergometer exercise on plasma lipids in 675 healthy, sedentary, normolipidemic white and black men and women aged 17 to 65 years, participating in the HERITAGE Family Study. Fasting plasma lipids were assessed twice at baseline and 24 and 72 hours after the last exercise session and adjusted for plasma volume changes. No significant differences from the mean baseline levels were observed for total, low-density lipoprotein (LDL), and very-low-density lipoprotein (VLDL) cholesterol and apolipoprotein B (Apo B). A significant reduction (P < .01) from baseline levels in plasma total and VLDL triglycerides was observed only in the 24-hour posttraining specimens, reflecting a response to the last bout of exercise. High-density lipoprotein (HDL) cholesterol increased 3.6% for the combined group, primarily due to an increase in HDL2, with an associated increase in Apo A-1 (P < .001). No significant differences were noted in the HDL response by sex, race, or age. An inverse correlation (r = -.241) was observed between the increase in HDL cholesterol and change in body fat only in men, and the increase in HDL cholesterol was unrelated to the change in maximal oxygen uptake (VO2max).

Familial resemblance for abdominal visceral fat : the HERITAGE family study

OBJECTIVES: Abdominal visceral fat (AVF) is considered a risk factor for diabetes, atherogenic lipid profiles and hypertension. However, little is known about the genetic contribution to AVF as compared to total body fat. DESIGN: AVF was assessed by computerized tomography, and total body fat (fat mass) was assessed by underwater weighing in 86 families participating in the Heritage Family Study. All family members were sedentary at baseline examination. The familial factors underlying the variability in age-adjusted AVF, age-fat mass-adjusted AVF and age-adjusted fat mass, were assessed using a familial correlation model. RESULTS: The maximal heritability (including genetic and familial environmental effects) for AVF was comparable before (47%) and after (48%) adjusting for fat mass, and was 55% for fat mass itself in these sedentary families. Spouse correlations were significant for fat mass and for AVF prior to, but not after, adjustment for fat mass. CONCLUSIONS: These results confirm the only previous study which investigated the familial aggregation of AVF (both in pattern and magnitude), suggesting that the factors underlying AVF in these sedentary families may be similar to those in the population at large. Although both genetic and familial environmental factors probably influence each of fat mass and AVF, there appears to be a predominantly genetic etiology for the visceral component which is independent of total body fat. These findings imply that some individuals are more at risk than others because of an inherited tendency to store abdominal fat viscerally rather than subcutaneously.