The Stanford Leisure-Time Activity Categorical Item (L-Cat): a single categorical item sensitive to physical activity changes in overweight/obese women.

BACKGROUND: Physical activity is essential for chronic disease prevention, yet <40% of overweight/obese adults meet the national activity recommendations. For time-efficient counseling, clinicians need a brief, easy-to-use tool that reliably and validly assesses a full range of activity levels, and, most importantly, is sensitive to clinically meaningful changes in activity. The Stanford Leisure-Time Activity Categorical Item (L-Cat) is a single item comprising six descriptive categories ranging from inactive to very active. This novel methodological approach assesses national activity recommendations as well as multiple clinically relevant categories below and above the recommendations, and incorporates critical methodological principles that enhance psychometrics (reliability, validity and sensitivity to change). METHODS: We evaluated the L-Cat's psychometrics among 267 overweight/obese women who were asked to meet the national activity recommendations in a randomized behavioral weight-loss trial. RESULTS: The L-Cat had excellent test-retest reliability (κ=0.64, P<0.001) and adequate concurrent criterion validity; each L-Cat category at 6 months was associated with 1059 more daily pedometer steps (95% CI 712-1407, ß=0.38, P<0.001) and 1.9% greater initial weight loss at 6 months (95% CI -2.4 to -1.3, ß=-0.38, P<0.001). Of interest, L-Cat categories differentiated from each other in a dose-response gradient for steps and weight loss (Ps<0.05) with excellent face validity. The L-Cat was sensitive to change in response to the trial's activity component. Women increased one L-Cat category at 6 months (M=1.0±1.4, P<0.001); 55.8% met the recommendations at 6 months whereas 20.6% did at baseline (P<0.001). Even among women not meeting the recommendations at both baseline and 6 months (n=106), women who moved 1 L-Cat categories at 6 months lost more weight than those who did not (M=-4.6%, 95% CI -6.7 to -2.5, P<0.001). CONCLUSIONS: Given strong psychometrics, the L-Cat has timely potential for clinical use such as tracking activity changes via electronic medical records, especially among overweight/obese populations who are unable or unlikely to reach national recommendations.

Predicting Adult Pulmonary Ventilation Volume and Wearing Compliance by On-Board Accelerometry During Personal Level Exposure Assessments.

BACKGROUND: Metabolic functions typically increase with human activity, but optimal methods to characterize activity levels for real-time predictions of ventilation volume (l/min) during exposure assessments have not been available. Could tiny, triaxial accelerometers be incorporated into personal level monitors to define periods of acceptable wearing compliance, and allow the exposures (µg/m3) to be extended to potential doses in µg/min/kg of body weight? OBJECTIVES: In a pilot effort, we tested: 1) whether appropriately-processed accelerometer data could be utilized to predict compliance and in linear regressions to predict ventilation volumes in real time as an on-board component of personal level exposure sensor systems, and 2) whether locating the exposure monitors on the chest in the breathing zone, provided comparable accelerometric data to other locations more typically utilized (waist, thigh, wrist, etc.). METHODS: Prototype exposure monitors from RTI International and Columbia University were worn on the chest by a pilot cohort of adults while conducting an array of scripted activities (all <10 METS), spanning common recumbent, sedentary, and ambulatory activity categories. Referee Wocket accelerometers that were placed at various body locations allowed comparison with the chest-located exposure sensor accelerometers. An Oxycon Mobile mask was used to measure oral-nasal ventilation volumes in-situ. For the subset of participants with complete data (n= 22), linear regressions were constructed (processed accelerometric variable versus ventilation rate) for each participant and exposure monitor type, and Pearson correlations computed to compare across scenarios. RESULTS: Triaxial accelerometer data were demonstrated to be adequately sensitive indicators for predicting exposure monitor wearing compliance. Strong linear correlations (R values from 0.77 to 0.99) were observed for all participants for both exposure sensor accelerometer variables against ventilation volume for recumbent, sedentary, and ambulatory activities with MET values ~<6. The RTI monitors mean R value of 0.91 was slightly higher than the Columbia monitors mean of 0.86 due to utilizing a 20 Hz data rate instead of a slower 1 Hz rate. A nominal mean regression slope was computed for the RTI system across participants and showed a modest RSD of +/-36.6%. Comparison of the correlation values of the exposure monitors with the Wocket accelerometers at various body locations showed statistically identical regressions for all sensors at alternate hip, ankle, upper arm, thigh, and pocket locations, but not for the Wocket accelerometer located at the dominant-side wrist location (R=0.57; p=0.016). CONCLUSIONS: Even with a modest number of adult volunteers, the consistency and linearity of regression slopes for all subjects were very good with excellent within-person Pearson correlations for the accelerometer versus ventilation volume data. Computing accelerometric standard deviations allowed good sensitivity for compliance assessments even for sedentary activities. These pilot findings supported the hypothesis that a common linear regression is likely to be usable for a wider range of adults to predict ventilation volumes from accelerometry data over a range of low to moderate energy level activities. The predicted volumes would then allow real-time estimates of potential dose, enabling more robust panel studies. The poorer correlation in predicting ventilation rate for an accelerometer located on the wrist suggested that this location should not be considered for predictions of ventilation volume.

Demonstration of a relationship between level of physical training and insulin-stimulated glucose utilization in normal humans.

The relationship between level of physical training and in vivo insulin-stimulated glucose utilization was investigated in 33 healthy nonobese subjects. Status of physical training was estimated by maximal oxygen consumption (VO2 max) during graded bicycle ergometry, and insulin action by the insulin clamp technique. Within the study population we defined a significant (r = 0.63, P less than 0.001) correlation between these two variables. This relationship was independent of age and obesity and accounted for over 40% of the variance in insulin-stimulated glucose utilization among these subjects. In addition, significant correlations existed between VO2 max and the plasma glucose (r = -0.35, P less than 0.05) and insulin (r = -0.37, P less than 0.05) responses to an oral glucose load. These results suggest that differences in level of physical training play a regulatory role in control of in vivo insulin action.

Ultrasonic tissue characterization with a real time integrated backscatter imaging system in normal and aging human hearts.

Experimental studies have shown that variation in the magnitude of integrated ultrasonic backscatter during the cardiac cycle represents acoustic properties of myocardium that are affected by pathologic processes; however, there are few clinical studies using integrated backscatter. Forty subjects without cardiovascular disease (aged 22 to 71 years, mean 41) were studied with use of a new M-mode format integrated backscatter imaging system to characterize the range of cyclic variation of integrated backscatter in normal subjects. Cyclic variation in integrated backscatter was noted in both the septum and the posterior wall in all subjects. The magnitude of the cyclic variation of integrated backscatter and the interval from the onset of the QRS wave of the electrocardiogram to the minimal integrated backscatter value were measured using an area of interest of variable size for integrated backscatter sampling and a software resident in the ultrasound scanner. The magnitude of cyclic variation was larger for the posterior wall than for the septum (6.3 +/- 0.8 versus 4.9 +/- 1.3 dB, p less than 0.01). The interval to the minimal integrated backscatter value was 328 +/- 58 ms for the septum and 348 +/- 42 ms for the posterior wall (p = NS). There was a weak correlation between the magnitude of cyclic variation of integrated backscatter and subject age for the posterior wall (r = -0.47, p less than 0.01), but this was not significant for the septum (r = -0.21) (partially because of inability to exclude specular septal echoes) and septal endocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Smoking in older women. Is being female a 'risk factor' for continued cigarette use?

Current national data indicate that a greater percentage of women entering their fifth and sixth decades of life are current, as opposed to former, smokers, while for men the opposite pattern is present. A representative sample of 1876 men and women aged 50 to 65 years living in a northern California community were interviewed to examine factors related to gender differences in quit rates in this age group. In this well-educated community, a significantly greater percentage of women (25.6%) continued to smoke relative to men (18.6%), with a greater percentage of men reporting being former smokers. Multivariate analysis revealed educational level and marital status, rather than gender, to be significant, Independent factors associated both with current cigarette use and with successful quitting. Our data indicate that it is not being female per se, but rather the disparities in educational level and marital status that are linked with being an older woman, that are associated with continued smoking in this age group. In light of this, delivery of relevant information and support on the part of physicians and other health professionals may be of particular use to this population segment.

A review of the incorporation of complementary and alternative medicine by mainstream physicians.

BACKGROUND: Studies suggest that between 30% and 50% of the adult population in industrialized nations use some form of complementary and/or alternative medicine (CAM) to prevent or treat a variety of health-related problems. METHOD: A comprehensive literature search identified 25 surveys conducted between 1982 and 1995 that examined the practices and beliefs of conventional physicians with regard to 5 of the more prominent CAM therapies: acupuncture, chiropractic, homeopathy, herbal medicine, and massage. Six studies were excluded owing to their methodological limitations. RESULTS: Across surveys, acupuncture had the highest rate of physician referral (43%) among the 5 CAM therapies, followed by chiropractic (40%) and massage (21%). Rates of CAM practice by conventional physicians varied from a low of 9% for homeopathy to a high of 19% for chiropractic and massage therapy. Approximately half of the surveyed physicians believed in the efficacy of acupuncture (51%), chiropractic (53%), and massage (48%), while fewer believed in the value of homeopathy (26%) and herbal approaches (13%). CONCLUSIONS: This review suggests that large numbers of physicians are either referring to or practicing some of the more prominent and well-known forms of CAM and that many physicians believe that these therapies are useful or efficacious. These data vary considerably across surveys, most likely because of regional differences and sampling methods, suggesting the need for more rigorous surveys using national, representative samples. Finally, outcomes studies are needed so that physicians can make decisions about the use of CAM based on scientific evidence of efficacy rather than on regional economics and cultural norms.

Relationship between habitual physical activity and insulin levels among nondiabetic men and women. San Luis Valley Diabetes Study.

OBJECTIVE: To determine whether higher levels of physical activity would be associated with lower fasting insulin and C-peptide levels in a free-living nondiabetic population. RESEARCH DESIGN AND METHODS: A cross-sectional study was conducted with a Hispanic and non-Hispanic white population of 442 men and 489 women with normal glucose tolerance (by World Health Organization criteria) in two rural Colorado counties. Total physical activity was assessed by a 7-day physical activity recall from which metabolic equivalents were estimated. Relationships between metabolic equivalents and fasting insulin and C-peptide were assessed while considering obesity, age, and other risk factors known to influence fasting insulin levels. RESULTS: Among all subjects, univariate analyses showed that higher activity levels were associated with lower mean fasting insulin and C-peptide levels (P less than or equal to 0.05). Multiple linear regression showed that higher activity was significantly associated with lower values of log fasting insulin and C-peptide levels in men only (P less than 0.001) independent of obesity, fat distribution, and age. Men in the highest tertile of activity had an adjusted mean fasting insulin level of 59.2 pM and fasting C-peptide level of 0.5 nM compared with a fasting insulin level of 72.7 pM and fasting C-peptide level of 0.6 mM for men in the lowest tertile of activity. The magnitude of the inverse association between activity and insulin was greatest in older rather than younger men. Physical activity was not associated with fasting insulin or C-peptide levels in women in the multivariate analyses. CONCLUSIONS: Based on cross-sectional data, we conclude that higher levels of habitual physical activity are associated with lower fasting insulin and C-peptide levels in Hispanic and non-Hispanic white men.

Relationship between habitual physical activity and insulin area among individuals with impaired glucose tolerance. The San Luis Valley Diabetes Study.

OBJECTIVE: To determine whether higher levels of physical activity are associated with lower fasting insulin levels and lower insulin areas under the oral glucose tolerance curve in individuals with impaired glucose tolerance (IGT) in a community setting. RESEARCH DESIGN AND METHODS: Data from a cross-sectional study of a population consisting of 219 Hispanic and non-Hispanic white men and women with IGT (by World Health Organization criteria) in two rural Colorado counties were analyzed. Total physical activity was assessed by a 7-day physical activity recall, from which metabolic equivalents (METs) were estimated (expressed as MET h/week). Relationships of MET h/week with fasting insulin levels and insulin areas were assessed while considering obesity, age, and other risk factors known to influence fasting insulin level and insulin area. RESULTS: Among all subjects, univariate analyses showed that higher physical activity levels were associated with lower mean insulin areas and fasting insulin levels (both P < 0.05). Multiple linear regression showed that higher levels of physical activity were significantly associated with lower values of of the insulin area (P < 0.001) but not with fasting insulin levels. The relationship between insulin area and habitual physical activity was independent of obesity, fat distribution, and age. CONCLUSIONS: On the basis of cross-sectional data, we conclude that higher levels of habitual physical activity are associated with lower insulin areas in a population of individuals with IGT. Understanding the impact of physical activity on markers of insulin action in individuals with IGT is important because of the greatly enhanced risk of non-insulin-dependent diabetes mellitus and, hence, cardiovascular disease in this population.

Clinical review 97: Potential health benefits of dietary phytoestrogens: a review of the clinical, epidemiological, and mechanistic evidence.

Phytoestrogens represent a family of plant compounds that have been shown to have both estrogenic and antiestrogenic properties. A variety of these plant compounds and their mammalian metabolic products have been identified in various human body fluids and fall under two main categories: isoflavones and lignans. A wide range of commonly consumed foods contain appreciable amounts of these different phytoestrogens. For example, soy and flax products are particularly good sources of isoflavones and lignans, respectively. Accumulating evidence from molecular and cellular biology experiments, animal studies, and, to a limited extent, human clinical trials suggests that phytoestrogens may potentially confer health benefits related to cardiovascular diseases, cancer, osteoporosis, and menopausal symptoms. These potential health benefits are consistent with the epidemiological evidence that rates of heart disease, various cancers, osteoporotic fractures, and menopausal symptoms are more favorable among populations that consume plant-based diets, particularly among cultures with diets that are traditionally high in soy products. The evidence reviewed here will facilitate the identification of what is known in this area, the gaps that exist, and the future research that holds the most potential and promise.

Regional adiposity patterns in relation to lipids, lipoprotein cholesterol, and lipoprotein subfraction mass in men.

Anatomical adipose tissue distribution patterns are reported to relate to plasma lipids and risk of cardiovascular disease. Waist to hip girth ratios (WHR) and subscapular 10 triceps skinfold thickness ratios (STR) were compared with percent body fat and body mass index values as correlates of plasma lipids and lipoprotein cholesterol and serum lipoprotein subfraction mass by analytic ultracentrifugation in 81 sedentary middle-aged men in a typical range of adiposity. WHR was significantly and positively correlated with plasma concentrations of triglycerides, cholesterol, and low and very low density lipoprotein (LDL and VLDL) cholesterol and inversely correlated with high density lipoprotein (HDL) cholesterol. STR followed these trends, though less strongly, in relation to plasma triglycerides, VLDL cholesterol, and HDL cholesterol. Pronounced differences were found between regional adiposity patterns in their relationships to lipoprotein subfractions, as determined by analytic ultracentrifugation. WHR was negatively correlated with HDL2 (flotation rate F(1.2) 3.5-9), positively with small LDL (S.f 0-7), intermediate density lipoprotein (S.f 12-20), and VLDL (S.f 20-400), while STR correlated with larger LDL (S.f 7-12) and larger VLDL (S.f 60-400). Overall adiposity was not significantly associated with plasma lipoprotein levels after adjusting for regional adiposity patterns. Plasma sex hormone-binding globulin and percent free testosterone were associated with regional adiposity, but did not account for the correlations between WHR and lipoproteins. WHR and STR are measures of fat distribution that correlate with plasma lipoprotein profiles consistent with cardiovascular disease risk and have different relationships to lipoprotein mass subfractions.

Methodologic issues in measuring physical activity and physical fitness when evaluating the role of dietary supplements for physically active people.

Physical activity and physical fitness are complex entities comprising numerous diverse components that present a challenge in terms of accurate, reliable measurement. Physical activity can be classified by its mechanical (static or dynamic) or metabolic (aerobic or anaerobic) characteristics and its intensity (absolute or relative to the person's capacity). Habitual physical activity can be assessed by using a variety of questionnaires, diaries, or logs and by monitoring body movement or physiologic responses. Selection of a measurement method depends on the purpose of the evaluation, the nature of the study population, and the resources available. The various components of physical fitness can be assessed accurately in the laboratory and, in many cases, in the field by using a composite of performance tests. Most coaches and high-level athletes would accept as very beneficial a dietary supplement that would increase performance in a competitive event by even 3%; for example, lowering a runner's time of 3 min, 43 s in the 1500 m by 6.7 s. To establish that such small changes are caused by the dietary supplement requires carefully conducted research that involves randomized, placebo-controlled, double-blind studies designed to maximize statistical power. Statistical power can be increased by enlarging sample size, selecting tests with high reliability, selecting a potent but safe supplement, and maximizing adherence. Failure to design studies with adequate statistical power will produce results that are unreliable and will increase the likelihood that a true effect will be missed.

The effect of soy protein with or without isoflavones relative to milk protein on plasma lipids in hypercholesterolemic postmenopausal women.

BACKGROUND: Clinical trial data and the results of a meta-analysis suggest a hypocholesterolemic effect of soy protein. The effect may be partially attributable to the isoflavones in soy. Few studies have examined the separate effects of soy protein and isoflavones. OBJECTIVE: The objective of this study was to determine the effect of soy protein and isoflavones on plasma lipid concentrations in postmenopausal, moderately hypercholesterolemic women. DESIGN: This was a randomized, double-blind, placebo-controlled clinical trial with 3 treatment groups. After a 4-wk run-in phase during which the women consumed a milk protein supplement, the subjects were randomly assigned to 12 wk of dietary protein supplementation (42 g/d) with either a milk protein (Milk group) or 1 of 2 soy proteins containing either trace amounts of isoflavones (Soy- group) or 80 mg aglycone isoflavones (Soy+ group). RESULTS: LDL-cholesterol concentrations decreased more in the Soy+ group (n = 31) than in the Soy- group (n = 33) (0.38 compared with 0.09 mmol/L; P = 0.005), but neither of these changes was significantly different from the 0.26-mmol/L decrease observed in the Milk group (n = 30). The results for total cholesterol were similar to those for LDL cholesterol. There were no significant differences in HDL-cholesterol or triacylglycerol concentrations between the 3 groups. CONCLUSIONS: The difference in total- and LDL-cholesterol lowering between the 2 soy-protein supplements suggests an effect attributable to the isoflavone-containing fraction. However, the unexpected LDL-cholesterol lowering observed in the Milk group, and the fact that there was no significant difference between either soy group and the Milk group, suggests that changes may have been due to other factors related to participation in the study.

Effect of health education on dietary behavior: the Stanford Three Community Study.

A 2-yr mass media cardiovascular health education program in two communities was followed by a 3rd, maintenance yr of reduced effort. In each community, a representative cohort reported its dietary behavior annually to an interviewer using a questionnaire which estimated daily consumption of cholesterol and fat. Relative weight and plasma cholesterol were also measured annually. Both men and women in the treatment towns reported reductions in dietary cholesterol (23 to 34%) and saturated fat (25 to 30%) which were significantly larger than those reported in a 3rd, control community. Relative weight was increased in the control community when compared to the treatment towns, perhaps as a result of the aging of the cohorts. Similar patterns were observed for plasma cholesterol changes. The 2-yr changes were maintained or increased during the 3rd, maintenance yr. The changes in individual values for plasma cholesterol showed low level correlations with dietary cholesterol and saturated fat, but the association with weight change was more important. These results suggest that mass media health education can achieve lasting changes in diet, obesity, and plasma cholesterol on a community level.

Effects of physical activity on weight reduction in obese middle-aged women.

Increased physical activity consisting of jog-walking 2.5 miles and 1 hr of calisthenics/week was the primary focus of a 17-week weight reduction program in 22 obese (X = 40% body fat) women ages 30 to 52, many of whom had failed at previous attempts to lose weight by dieting alone. Regular exercise was also increased substantially on an individual basis. Caloric restriction was self-determined and was generally moderate, accounting for about 60% of the total mean energy deficit. Initial and final evaluations included body composition by hydrostatic weighing, progressive multistage exercise testing, and plasma lipid and lipoprotein analyses. A mean relative body fat reduction of 5% (P less than or equal to 0.001) was achieved by a drop in fat body weight (X = 5.4 kg; P less than or equal to 0.001) which closely paralleled that of total body weight (X = 4.2 kg; P less than or equal to 0.001). Mean heart rates and systolic blood pressures at identical submaximal exercise intensities were significantly lower at the time of reevaluation. Mean plasma triglyceride and total cholesterol concentrations did not change significantly (P greater than 0.05). However, the high-density lipoprotein cholesterol/low-density lipoprotein cholesterol ratio increased significantly (P less than or equal to 0.05). Increased physical activity combined with moderate dieting is a feasible approach to weight reduction in middle-aged women.

Physical-activity-assessment measures compared in a biethnic rural population: the San Luis Valley Diabetes Study.

We evaluated the consistency of three questionnaire methods of assessing work and leisure activity in the rural biethnic population of the San Luis Valley Diabetes Study. A 7-d physical activity recall (PAR), a ranking of usual activity, and a history of usual participation in vigorous activity were used. Energy expenditure (kJ.kg-1.wk-1) (EE) was estimated from PAR. Subjects were 503 adults [49% non-Hispanic white (NHW), 51% Hispanic]. Physical activity at work rather than leisure-time activity largely determined total energy expenditure. Average EE at work increased with work rank for all subjects combined [mean EE (SEE) for rank 1 (low) = 324.2 (24.4), rank 4 (high) = 874.0 (102.1)] and within sex, ethnic, and occupational subgroups. Leisure EE increased with leisure rank only for NHW men and employed women. Similar patterns were observed in comparisons of PAR data with history of vigorous activity. Further development and validation of instruments appropriate for use across population subgroups are needed.

Association of lipoprotein subclass distribution with use of selective and non-selective beta-blocker medications in patients with coronary heart disease.

The relationship of beta-blocker drug use to plasma low density lipoprotein-cholesterol (LDL-C), lipoprotein mass distribution, (LDL, Sf0-12), intermediate density lipoproteins (IDL, Sf12-20), very low density lipoproteins (VLDL, Sf20-400), and high density lipoproteins (HDL, F(1.2)0-9) were examined in 206 men with coronary heart disease. Thirty-three used non-selective (NSEL), 49 used selective (SEL), and were compared to 124 who used no beta-blockade (NoBB). No significant between group differences were seen for potentially confounding variables. LDL and IDL mass, total cholesterol and LDL-cholesterol were not significantly different between groups. HDL-C was significantly lower in both NSEL (P < 0.005) and SEL (P < 0.01). NSEL and SEL had significantly lower HDL mass (P < 0.005 and P < 0.005) and SEL (P < 0.01 and P = 0.06), and HDL3 mass (P < 0.01 and P < 0.05). VLDL mass was significantly higher (P < 0.02) only in NSEL. Small LDL (Sf0-7) was not significantly different between groups and large LDL (Sf7-12) was significantly lower in NSEL (P < 0.05) and SEL (P < 0.05). LDL peak Sf was significantly lower in both NSEL (P < 0.005) and SEL (P < 0.02) compared to NoBB. Despite the lack of differences in levels of LDL-cholesterol, beta-blocker use is associated with a significant difference in the distribution of larger, more buoyant to smaller, more dense LDL particles. Reduced HDL levels in subjects on beta-blockade therapy are associated with reductions in both HDL2 and HDL3 subclasses.(ABSTRACT TRUNCATED AT 250 WORDS)

Does weight loss cause the exercise-induced increase in plasma high density lipoproteins?

Studies showing an increase in plasma concentration of high density lipoprotein cholesterol (HDL-C) with moderate exercise have usually rejected the role of body weight change in the HDL-C raising process, ostensibly because the amount of weight lost has been negligible. To investigate HDL-C changes more thoroughly, we followed initially sedentary middle-aged men randomly assigned to either a moderate running (n = 36) or a sedentary control (n = 28) group for one year. Among runners, one-year changes in plasma HDL-C concentrations correlated strongly with their body weight changes (r = - 0.53, P less than 0.001). Curve-fitting procedures and regression analysis suggested that processes associated with weight change produce much of the plasma HDL-C changes induced by moderate exercise and that changes in HDL-C concentration predominantly reflect changes in the reputedly anti-atherogenic HDL2 sub-component. Further, the interaction between weight change and plasma HDL-C concentration was significantly different (P less than 0.001) in exercisers and controls suggesting that the metabolic consequences of exercise-induced weight change are different from the consequences of weight change in the sedentary state.

Coronary heart disease and risk factor modification. Is there a threshold?

Modification of coronary heart disease risk factors may play an important role in the control and alteration of the atherosclerotic process. The amount of modification necessary to obtain beneficial results is a controversial issue. Review of epidemiologic studies and recent arteriographic investigations allows for the approach to the issue of threshold levels of modification that may be required prior to obtaining some benefit. Serum lipoproteins appear to play a central role in the atherosclerotic risk factor relationship. On the basis of current evidence, clinical aims are suggested for coronary heart disease risk factor modification in order to assist in obtaining optimal health goals.

Relationship of exercise, oral contraceptive use, and body fat to concentrations of plasma lipids and lipoprotein cholesterol in young women.

To investigate the relationship of exercise and oral contraceptive use to plasma lipids and lipoproteins, a cross-sectional study was designed to compare lipid levels in 96 exercising and non-exercising women who used or did not use oral contraceptives. Exercisers had significantly lower plasma triglyceride concentrations and low-density/high-density lipoprotein ratios than non-exercisers after adjustment for differences in pill type distribution between groups. Women using progestin-dominant pills had significantly lower plasma triglyceride and high-density lipoprotein concentrations and significantly higher low-density/high-density lipoprotein ratios compared with women using estrogen/progestin-balanced pills. As body fat was significantly associated with both pill type and physical activity, it is unclear how much of these lipoprotein differences were due to body fat, exercise, or pill use. Regular physical activity together with reduced body fat partially compensated for plasma lipoprotein differences associated with oral contraceptive use.

Physical activity and health: need to define the required stimulus.

Exercise is frequently recommended as part of a comprehensive program of prevention, treatment or rehabilitation of chronic degenerative disease. General guidelines on prescribing exercise are based more on the characteristics of exercise required to improve physical performance than on preventing disease. Most exercise regimens are evaluated according to their effect on aerobic power or endurance. Health benefits of exercise may occur in conjunction with an improvement in physical performance capacity, but some benefits appear to be achieved by exercise that normally does not lead to improved physical fitness. Health benefits may occur as a result of repeated acute responses to exercise (but without producing a training effect) and by frequent performance of low intensity exercise (inadequate for increasing fitness). Psychological benefits may also be derived by the process of exercising. The persons who benefit most from an increase in exercise are the very inactive because the detrimental health-related consequences of extreme inactivity are rapidly reversed. There is less evidence that an increase in exercise by the already active person results in significant health benefits.