Intra-individual variation and estimates of usual physical activity

PURPOSE

The magnitude of intra-individual variation, as determined by three methods of physical activity (PA) assessment, was estimated to determine the optimal number of repeated measures needed to reliably measure an individual's usual PA habits.

METHODS

Data were obtained from 77 healthy adults enrolled in the Survey of Activity, Fitness, and Exercise (SAFE). PA was measured by: 1) Caltrac accelerometers worn 48-hours every 26 days for one year; 2) concurrent 48-hour PA records (PARs); and 3) a corresponding series of four-week PA histories (FWH). Repeated measures regression analyses were used to analyze the data.

RESULTS

PA tended to be slightly higher in the summer months as compared with the winter months, but this seasonality explained little of the intra-individual variation. The intra-individual standard deviation (SD) estimated for the FWH (180 MET-min(d(-1))) was 39% of the mean annual MET-min(d(-1)), as compared with the Caltrac (163 MET-mind(d(-1)) or 9%) and PAR (259 MET-min(d(-1)) or 11%). Given the intra-individual variation, three repeated observations of the FWH, six Caltrac, or nine PAR over the course of the year were needed to achieve 80% reliability in estimation of mean annual PA.

CONCLUSIONS

Intra-individual variation in PA is substantial and must be accounted for in estimates of usual PA.

Validation of Aerosport KB1-C portable metabolic system

The purpose of this study was to test the validity of the Aerosport KB1-C portable metabolic measurement system against the criterion Douglas bag method. During cycle ergometry, simultaneous measurements of minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) were made at rest and at power outputs of 50, 100, 150, 200, and 250 W. No significant differences (P > 0.05) were observed for VE, VO2, and VCO2 between the KB1-C and Douglas bag at 100, 150, and 250 W, while the KB1-C was significantly different (P < 0.05) from Douglas bag values at rest, 50, and 200 W. R values were found to be significantly different (P < 0.05) at 100, 150, and 200 W, while no significant differences were observed at rest, 50, and 250 W. The fractional concentrations of oxygen (FEO2) and carbon dioxide (FECO2) were not significantly different at 50, 100, 200, and 250 W while values at rest and 150 W were significantly different (P < 0.05). These findings show that the Aerosport KB1-C portable metabolic system is acceptable for measuring oxygen uptake in the range of 1.5 and 3.5 L x min(-1), using the medium flow pneumotach setting. At lower intensities, the low-flow pneumotach setting provides acceptable results.

Moderate physical activity patterns of minority women: the Cross-Cultural Activity Participation Study

Using data from 12 days of detailed physical activity records (PA records), we analyzed the physical activity patterns of 141 African American and Native American women, ages 40 and older, enrolled in the Cross-Cultural Activity Participation Study. PA records were completed every other month for three consecutive 4-day periods. The proportion of women who met the 1993 Centers for Disease Control and Prevention and the American College of Sports Medicine recommendation to accumulate at least 30 minutes of moderate intensity activity during most days of the week (at least 3 days of the 4-day periods) ranged from 63% to 70%. Nearly one third of women met the recommendation for more than one 4-day period. On days when subjects accumulated at least 30 minutes of moderate activity, time spent in moderate activity was 112 minutes/day. Most women performed household chores (95%, median = 24 minutes/day), walking for exercise (87%, median = 30 minutes/day), occupational (65%, median = 37 minutes/day), child care (53%, median = 32 minutes/day), and lawn and garden activities (51%, median = 43 minutes/day). Fewer than 25% reported conditioning and sports activities. In general, more Native Americans than African Americans were active in moderate activities. In conclusion, definitions used to characterize regular physical activity should be consistent among studies, and physical activity surveys among women should include occupation-related and home-related activities.

Knowledge, attitudes and behaviors related to physical activity among Native Americans with diabetes

OBJECTIVE

Native Americans (NA) have higher diabetes morbidity and mortality compared to other ethnic groups. Although exercise plays an important role in diabetes management, little is known about exercise among Native Americans with diabetes. Our goal was to describe knowledge, attitudes and behaviors related to exercise in Native American participants in New Mexico.

DESIGN

Bilingual community members administered a questionnaire to assess knowledge, stage of change (a measure of exercise readiness), and physical activity behavior. Hemoglobin A1c (HbA1c) was measured by DCA 2000 analyzer. Height and weight were measured to calculate body mass index (BMI). Average random blood glucose (RBS) levels and diabetes duration were assessed through chart audit.

SETTING

Questionnaires were completed in offices in or near the communities.

PARTICIPANTS

514 Native Americans with diabetes were identified as potential participants, 40% (142 women, 64 men) participated.

RESULTS

37% of participants knew exercise lowers blood sugar. 82% reported they were in the preparation, action, or maintenance stage of change for exercise behavior. Seventy seven percent of this population did not meet the Surgeon General's recommendation for accumulating 30 minutes of leisure time endurance exercise on most days of the week. However, 67% of participants fell within the "high activity" category for all moderate and vigorous activities. Average age, BMI and HbA1c were 58.5 yrs., 30.5 kg/m2, 8.6%, respectively.

CONCLUSIONS

Interventions to increase physical activity awareness and participation could improve diabetes management and overall health for Native Americans. When evaluating physical activity, researchers need to consider usual activities of daily living and leisure time activities specific to that population. Failure to do so would be ethnocentric and could lead to inappropriate conclusions.

Accuracy of recall of occupational physical activity by questionnaire

The validity of the Tecumseh Occupational Activity Questionnaire (TOQ) and a modified Seven Day Recall (SDR) was measured in 46 healthy women, ages 20-60 years (mean +/- SD, 39.4 +/- 11.8). Occupational data were compared with direct (7-day occupational activity records and Caltrac accelerometer) and indirect (maximal oxygen uptake and percent body fat) measures of physical activity status. Physical activity survey and occupational record data were log transformed to normalize skewed distributions. Intraclass correlations ranged from r = 0.26 to 0.73 (P < 0.05) between similar activities on the TOQ and activity records for light intensity sitting, light-to-moderate intensity standing, and walking. Correlations between similar activities from the SDR and activity records ranged from r = 0.32 to 0.35 (P < 0.05) for light and moderate intensity activities. Correlations for total occupational activity between the surveys and activity records were r = 0.46 (P < 0.001) for the TOQ and r = 0.45 (P < 0.01) for the SDR. A modest correlation (r = 0.34, P < 0.10) was observed between the Caltrac scores and TOQ moderate intensity standing. Only the TOQ light-to-moderate intensity standing was related to maximal oxygen uptake (r = 0.32, P < 0.05). None of the measures were related to percent body fat (P > 0.05). These results suggest that the TOQ and SDR both provide reasonably accurate measurements of light and moderate intensity occupational physical activity.

Physical activity patterns in a diverse population of women

BACKGROUND

Demographic and psychosocial correlates of activity in domains other than recreational activity have not been well characterized and may be particularly relevant for health promotion efforts aimed at women.

METHODS

Cross-sectional relationships between recreational, occupational, and household/caregiving physical activity and demographic and psychosocial factors were assessed with a mail survey in a random sample of 2,636 ethnically diverse women members of a large health maintenance organization, ages 20-65. Activity was assessed with a modified Baecke questionnaire that uses categorical responses regarding frequency of domain-specific activities to create four semicontinuous activity indices (sports/exercise, active living, occupational, household/caregiving).

RESULTS

Multivariable logistic regression analysis showed that the likelihood of being in the highest quartile of the sports/exercise and active-living indices, compared with the other three quartiles, was decreased among older, nonwhite, less well educated, heavier women who had young children at home, lacked motivation to exercise, and perceived external obstacles to exercise behavior. The odds ratios (ORs) ranged from 0.38, 95% confidence interval (CI) 0.33-0.45, associated with low motivation, to 0.95, 95% CI 0.93-0.98, associated with increasing body mass index. Social support and confidence in one's ability to continue to exercise, even when faced with other pressures and demands (termed self-efficacy), were associated with increased likelihood of high levels of sports/exercise and active living (OR = 2.34, 95% CI 1. 83-2.98 and OR = 3.96, 95% CI 2.92-5.38, respectively). In contrast, the highest quartile of household/caregiving activity was positively associated with increasing age (OR = 1.28, 95% CI 1.16-1.42), Hispanic ethnicity (OR = 1.58, 95% CI 0.55-1.01), being married (OR = 1.70, 95% CI 1.33-2.18), having young children at home (OR = 6.99, 95% CI 4.33-11), and greater time constraints as a barrier to exercise (OR = 1.55, 95% CI 1.38-1.74) and was negatively associated with employment (OR = 0.38, 95% CI 0.30-0.47). Increased likelihood of the highest quartile of occupational activity was associated with high school education or less (OR = 2.26, 95% CI 1.74-2.94) and current smoking (OR = 1.66, 95% CI 1.23-2.23), while self-efficacy regarding exercise was associated with decreased likelihood (OR = 0. 77, 95% CI 0.61-0.96).

CONCLUSIONS

These findings suggest that demographic and psychosocial correlates of physical activity vary by domain and that initiatives to promote physical activity in the population need to take these differences into account.

Predictive accuracy of skinfold equations for estimating body density of African-American women

PURPOSE

The purpose of this study was to compare the predictive accuracy of previously published skinfold (SKF) equations for estimating body density of 134 premenopausal African-American women (18 to 40 yr).

METHODS

The equations cross-validated were: the sum of seven skinfolds equation (JPW7) and the sum of three skinfolds equation (JPW3), both of Jackson et al. (1980); the generalized equation (DWgen) and the age-specific equation (DWage) of Durnin and Womersley (1974); and the equation of Wang et al. (1994). Total body density was determined by hydrodensitometry (BDuww) at residual lung volume and converted to %BFuww using the Siri (1991) formula. The predictive accuracy of the SKF equations tested in this study was evaluated using the cross-validation procedures outlined by Lohman (1992).

RESULTS

The validity coefficients (ry,y') ranged from 0.83 (DWgen) to 0.87 (JPW7). The SEEs ranged from 0.0076 g.cc-1 (DWage) to 0.0122 g.cc-1 (Wang), and the total errors ranged from 0.0103 g.cc-1 (JPW7) to 0.0478 g.cc-1 (Wang). The percentage of individual residual scores falling within +/- 3.5% BF for this sample ranged from 31% (DWage) to 58% for the JPW7 equation. Comparison of the predictive accuracy of the five equations indicated that the JPW7 equation was the most valid equation, explaining 75% of the variance in reference body density with no significant difference between average reference BDuww (1.03035 g.cc-1) and average predicted BDJPW7 (1.03152 g.cc-1).

CONCLUSIONS

We recommend using the JPW7 equation to assess body composition and %BF of premenopausal African-American women.

Is physical activity or aerobic power more influential on reducing cardiovascular disease risk factors?

PURPOSE

This study determined the relationship between aerobic power (VO2max), physical activity (PA), and cardiovascular disease (CVD) risk factors. The study also determined how increased VO2max and increased PA levels influence CVD risk factors of 576 low-fit adults (VO2max < 30 mL.kg-1.min-1).

METHODS

PA (Baeke questionnaire) and VO2max (submaximal cycle test) of 1664 law enforcement trainees were evaluated with respect to the CVD risk factors of total cholesterol, blood pressure (BP) [BP], smoking, and obesity using separate logistic regression, adjusting for age, gender, and the other major CVD risk factors.

RESULTS

Compared with the lowest tertile of VO2max, the highest tertile had a reduced relative risk (RR) for elevated cholesterol (RR, 0.56; CI, 0.36-0.43), BP (RR, 0.32; CI, 0.15-0.62) and obesity (RR, 0.09; CI, 0.06-0.12). The middle tertile of VO2max compared with the lowest had reduced RR for elevated diastolic BP (RR, 0.44; CI, 0.23-0.66) and obesity (RR: 0.38; CI 0.28-0.50). High PA tertile, compared with low PA tertile, only had lower RR for high systolic BP (RR, 0.48; CI, 0.23-0.95). Compared with the low PA tertile, moderate or high PA had no reduction in any of the RR (P > 0.05). Participation in a 9-wk exercise program by low-fit individuals resulted in a 9% increase in PA levels (P < 0.02); however, only those subjects who increased VO2max (> 3 mL.kg-1.min-1; N = 345) had a reduction in RR for high cholesterol (RR: 0.62; CI 0.42-0.92) and systolic BP (RR: 0.57; CI 0.40-0.80). No reduction in RR were noted for diastolic BP or obesity.

CONCLUSIONS

Aerobic power appears to have more of an influence on CVD risk factors than PA levels. Further, in low-fit persons, it appears that PA resulting in an increased aerobic power is associated with a reduction in CVD risk factors of cholesterol and BP in as little as 9 wk.

Predicting aerobic power in children. A comparison of two methods

OBJECTIVE

To compare the accuracy of two equations for predicting VO2max of children using submaximal cycle ergometry.

EXPERIMENTAL DESIGN

Repeated measures comparing treadmill measured maximal aerobic power (VO2max) with two methods of predicting VO2max using cycle ergometry testing.

PARTICIPANTS

Thirty-three children (15 boys and 18 girls) aged 7-13 years served as subjects.

MEASURES

Each child completed a treadmill graded exercise test (GXT) to volitional fatigue to assess VO2max. Each child also completed a progressive 9-min, three-stage, submaximal cycle ergometer test. Heart rates obtained during the last minute of each stage of the ergometer test were used to predict VO2max. Predictions were based on a gender-specific modification of the PWC170 (PWCGS) and a modification of the PWC195 using a 1.17 correction factor and an age and gender-adjusted estimate of resting metabolic rate.

RESULTS

The correlations between both submaximal tests and the GXT were significant (p < 0.001); however, the correlation between the GXT and the PWC195 equation (r = 0.807) was higher than the correlation between the GXT and the PWCGS equation (r = 0.658). Analysis indicated that the PWCGS equation significantly underestimated the VO2max compared to either the GXT or PWC195 (GXT = 45.0 +/- 7.1, PWC195 = 44.7 +/- 6.2, PWCGS = 42.7 +/- 5.8 ml/kg/min; p < 0.01).

CONCLUSIONS

These results suggest that although the gender-specific PWCGS method is easier to compute and may be acceptable, the modified PWC195 method is a more accurate estimate of VO2max in children.

Physical activity and breast cancer: evaluation of physical activity assessment methods

Studies of the association between physical activity and breast cancer have yielded inconsistent findings. These findings may be related to a true null association or an inability to measure physical activity with enough precision to measure a protective relation. The authors reviewed and critiqued physical activity measurement methods used in published studies of the association between physical activity and breast cancer. The authors examined the quality of physical activity measures in 20 published studies. A summary score was created to rank the quality of the activity score. Studies with higher scores had a more precise measure of physical activity. Physical activity measurement methods were different in each study. Activity was measured by job classification, occupational tasks, participation in competitive athletics, and recreational and leisure-time pursuits. The recall period for physical activity ranged from a lifetime to the past year. Comparison of quality scores showed no associations between the precision of activity measures and the study results. Future studies of physical activity and breast cancer should utilize standardized methods to measure physical activity. Researchers should be encouraged to choose a measure based on hypotheses regarding physical activity and breast cancer mechanisms. Studies also should extend to subgroups of women with differences in other breast cancer risk factors, such as body mass, menopausal status, and hormone replacement status.

Moderate leisure-time physical activity: who is meeting the public health recommendations? A national cross-sectional study

We identified the prevalence of adults who met the 1993 Centers for Disease Control and Prevention and the American College of Sports Medicine moderate physical activity recommendation and the 1996 Surgeon General's Report on Physical Activity and Health energy expenditure guideline for leading a moderately active lifestyle. Participants were 16,890 women and 12,272 men at least 18 years old who were asked in the 1990 National Health Interview Survey about their leisure-time physical activities. About one third of US adults met either recommendation for moderate activity; 32% met the Centers for Disease Control and Prevention and the American Association of Sports Medicine recommendation and 38% met the surgeon general's guideline. Women, ethnic minorities, adults with lower educational attainment, and older adults were least active. Public health efforts are needed to address the issues related to physical inactivity and to provide organized programs to increase moderate physical activity levels in US adults.

Measuring physical activity in midlife, older, and minority women: issues from an expert panel

This article summarizes the findings of an exploratory meeting of 53 experts brought together under the aegis of the Women's Health Initiative to identify important issues related to measuring physical activity in minority women, women in midlife (aged 40-75), and older women (aged > 75). The findings address five areas, three dealing with measurement and two concerning the design of surveys: (1) population characteristics to consider when measuring the physical activity of women and minority populations, (2) activity dimensions relevant to physical activity surveys, (3) measuring moderate and intermittent activities, (4) designing and administering physical activity surveys for older and minority women, and (5) establishing the reliability and validity of such physical activity surveys. Although the focus of the expert panel meeting was on identifying issues related to the measurement of physical activity in women, many issues summarized here can be generalized to children and men. The panel's findings concerning measuring physical activity are timely, as they directly bear on the challenges associated with the physical activity guidelines jointly issued by the Centers for Disease Control and Prevention and the American College of Sports Medicine and the recommendations made in the Surgeon General's 1996 report, Physical Activity and Health.

Predictive accuracy of bioimpedance in estimating fat-free mass of African-American women

The purpose of this study was to identify the BIA (bioimpedance analysis) equation that yields the best estimate of body composition for 122 premenopausal African-American women (18-40 yr). Total body density (Db) was determined by hydrodensitometry at residual lung volume and converted to %BFHD using the Siri (31) formula, %BFHD was used to calculate reference fat-free mass (FFM). Resistance and reactance were measured using a Valhalla bioimpedance analyzer. The predictive accuracy of generalized, age-gender, race-specific, fatness-specific, and the Valhalla manufacturer's BIA equations was compared. There were significant correlations between FFMHD and FFMBIA for all BIA equations (r = 0.85 to 0.92). Except for the modified Segal fatness-specific equations, the prediction errors (SEE and E) exceeded 2.8 kg. For individuals, the %BF derived from FFMBIA predicted by the modified Segal equations was within +/- 3.5% BF for 69% of the subjects. This percentage was less (34-53%) for other equations. These results suggest that the predictive accuracy of BIA for estimating body composition of African-American women is improved when fatness-specific equations are used. We recommend using the modified Segal fatness-specific equations to assess FFM and %BF of premenopausal African-American women.

The recall of physical activity: using a cognitive model of the question-answering process

Issues related to the validity and reliability of self-reports of physical activity are an important consideration in assessing the relation between physical activity and various health outcomes that are of interest to epidemiologists. This paper examines the case for incorporating survey methods procedures into the development, refinement, and administration of instruments designed to obtain self-report information on physical activity. In doing so, we present a method of question analysis that enables researchers to identify potential cognitive difficulties with a question and then identify possible methods for improving data quality that have successfully improved the validity of survey instruments in other areas. In doing this, we review portions of the literature in cognitive psychology devoted to autobiographical memory and discuss methods that have emerged from this research that enhance the overall validity and reliability of the data obtained in a variety of health-related areas. We also illustrate ways in which these methods can be incorporated into existing physical activity surveys.

Accuracy of five electronic pedometers for measuring distance walked

This is a three-part study that examined the accuracy of five brands of electronic pedometers (Freestyle Pacer, Eddie Bauer, L.L. Bean, Yamax, and Accusplit) under a variety of different conditions. In Part I, 20 subjects walked a 4.88-km sidewalk course while wearing two devices of the same brand (on the left and right side of the body) for each of five different trials. There were significant differences among pedometers (P < 0.05), with the Yamax, Pacer, and Accusplit approximating the actual distance more closely than the other models. The Yamax pedometers showed close agreement, but the left and right Pacer pedometers differed significantly (P = 0.0003) and the Accusplit displayed a similar trend (P = 0.0657). In Part II, the effects of walking surface on pedometer accuracy were examined. Ten of the original subjects completed an additional five trials around a 400-m rubberized outdoor track. The devices showed similar values for sidewalk and track surfaces. In Part III, the effects of walking speed on pedometer accuracy were examined. Ten different subjects walked on a treadmill at various speeds (54, 67, 80, 94, and 107 m.min-1). Pedometers that displayed both distance and number of steps were examined. The Yamax was more accurate than the Pacer and Eddie Bauer at slow-to-moderate speeds (P < 0.05), though no significant differences were seen at the fastest speed. While there are variations among brands in terms of accuracy, electronic pedometers may prove useful in recording walking activities in free-living populations.

Ability of the Atherosclerosis Risk in Communities (ARIC)/Baecke Questionnaire to assess leisure-time physical activity

BACKGROUND

The Atherosclerosis Risk in Communities (ARIC)/Baecke Questionnaire is a general survey of both occupational and leisure (sport and exercise related and non-sport and exercise related) physical activity.

METHODS

Its ability to assess leisure physical activity was studied in 78 men and women, age 20-59 years, by comparison to: six 48-hour physical activity records; 14 48-hour Caltrac accelerometer readings (Caltrac); three peak oxygen consumption (VO2 peak) determinations; and per cent body fat. These criteria measures were obtained over a year's duration.

RESULTS

The following associations were evident in men and women respectively, between sport and exercise physical activity and: physical activity record heavy intensity activity (r = 0.73 and r = 0.63); VO2 peak (r = 0.67 and r = 0.45); and per cent body fat (r = -0.37, P = 0.08 and r = -0.44). Less concordance was evident (r = 0.39 for men and r = 0.23, NS, for women) between non-sport and exercise physical activity and physical activity record light intensity activity. Questionnaire and physical activity record indices of total leisure activity tended to be more closely related in men (r = 0.59) than women (r = 0.33). For both men and women, survey results were not closely associated with Caltrac readings.

CONCLUSIONS

Although there are weaknesses, questionnaire strengths consistent for both men and women include: ease of administration, high reliability, and accurate assessment of heavy intensity activity as well as light intensity activities such as walking and bicycling.

Ability of the Caltrac accelerometer to assess daily physical activity levels

PURPOSE

The purpose of this study was to determine the ability of the Caltrac accelerometer to assess habitual daily physical activity levels.

METHODS

The ability of the Caltrac accelerometer to assess 24-hour physical activity (PA) levels was studied in 28 men and 50 women, age 20 to 59 years, with varying levels of self-reported PA. Twelve days of Caltrac readings obtained over 1 year's duration were compared to simultaneously recorded 48-hour PA records. Additionally, 28 days of Caltrac readings obtained over 1 year's duration were compared to mean values of the following validation measures assessed repeatedly over a 1-year period: a 4-week version of the Minnesota Leisure Time Physical Activity Questionnaire (FWH); VO2peak; and percent body fat.

RESULTS

The Caltrac measurements of movement (in MET minutes per day-1) were significantly associated with the following: PA record indices of total (r = .51) and heavy (r = .34) and PA; FWH indices of total (r = .30), heavy R = .36) and moderate (r = .23) PA;, and VO2peak (r = .24). However, the Caltrac measurements of caloric PA record and FWH indices of PA, although there were directly associated with percent body fat (r = .50) and inversely associated with VO2peak (r = -.26).

CONCLUSIONS

Caltrac measurements of movement exhibited a moderate associated with several criterion measures related to habitual PA, whereas Caltrac measurements of total energy expenditure, were not reflective of varying levels of PA.

Nutritional status of nationally ranked elite bodybuilders

The nutritional status of 11 female and 13 male elite bodybuilders at the first drug-tested USA Championship was examined through food records kept by subjects. Diets were repetitive and monotonous, and average daily energy and protein contents were relatively similar for men and women. Percent calories from protein, fat, and carbohydrate were 39%, 12%, and 48% for females, and 40%, 11%, and 49% for males, respectively. Females consumed 0% vitamin D, 52% calcium, 76% zinc (as percents of RDA) and below the Estimated Safe and Adequate Dietary Allowance amounts for copper and chromium. Males consumed 46% of vitamin D RDA. Although dietary magnesium intakes were above the RDA, serum magnesium levels in females were below reference values, which should be investigated. Serum zinc levels were high in men and women. Eighty-one percent of females reported recurrent contest-related amenorrhea for 2 +/- 1 months precontest. Dietary intakes of men were adequate but the restrictive intakes of women may place them at risk for calcium, copper, and chromium deficiencies.

Comprehensive evaluation of the Minnesota Leisure Time Physical Activity Questionnaire

The accuracy of the Minnesota Leisure Time Physical Activity (LTPA) Questionnaire (a 1-year survey of non-occupational activity used in MRFIT) was studied in 78 men and women, age 20-59 years, by comparing survey results to the following measures obtained over a year's duration: six 48-hour physical activity records; fourteen 48-hour Caltrac accelerometer readings (Caltrac); 14 administrations of a 4-week version of the LTPA Questionnaire (FWH); 3 VO2peak determinations and percent body fat (% BF). The LTPA Questionnaire demonstrated: weak to moderate associations with % BF (r = -0.24) and with VO2peak (r = 0.47); a weak association with Caltrac readings expressed as MET.minutes.day-1 (r = 0.23); strong associations with corresponding activities reported on the FWH; and moderate associations with total and heavy activities reported in the physical activity record, but no associations with moderate and light activities. Furthermore, several types of LTPA were found to be either under-represented or not currently included in the Minnesota LTPA Questionnaire. It is concluded that although validation results were found to be quite good, several possible refinements were identified, which should improve the accuracy of the Minnesota LTPA Questionnaire in assessing habitual physical activity.

Accuracy of the College Alumnus Physical Activity Questionnaire

The validity and reproducibility of the Physical Activity Index from the College Alumnus Questionnaire (PAI-CAQ) were determined in 78 men and women (21-59 yr) with a broad range of physical activity habits. The PAI-CAQ was computed as the sum of energy expended in stair climbing, walking, and sports and recreational physical activity recalled from the past week. Data were validated against measures of cardiorespiratory fitness, body fatness, motion detection, and physical activity records. All physical activity was recorded by participants for six 48-hour periods. Each day of the week, including weekends, were represented at least twice in the physical activity records. Age-adjusted correlation coefficients between like activities on the College Alumnus Questionnaire and physical activity records ranged from 0.25 to 0.65 in men and 0.28 to 0.86 in women. Correlations between the PAI-CAQ and validation criteria that reflected total and heavy-intensity physical activities were higher (r = 0.34-0.69, p < 0.05) than for lighter-intensity physical activities and motion detection expressed in MET-min.d-1 and kcal.d-1 (r < 0.35, p > 0.05). Test-retest reproducibility was higher over 1 month (r = 0.72) than over 8 and 9 months (r = 0.34 and 0.43) (p < 0.05). Energy expended in walking and stair climbing was underestimated on the College Alumnus Questionnaire, resulting in lower PAI-CAQ scores, as compared to the physical activity records.

Assessment of the accuracy of physical activity questionnaire occupational data

The validity and reliability of occupational physical activity data from survey instruments were determined in 75 men and women (age 23 to 59 years) in white-collar jobs. Data were validated against measures of cardiorespiratory fitness, body fatness, motion detection, pulmonary function, and 12 days of occupational physical activity records. More than 90% of occupational physical activity was spent in light-intensity sitting, standing, and walking. Test-retest reliability was high for most occupational questions (r > or = .63, P < .05). Correlation coefficients between questionnaire data and validation criteria that reflect heavy-intensity physical activity were low (r < .17, P > .05). The modified Tecumseh Occupational Questionnaire and Seven-Day Recall, which classified occupational physical activity in hours per week worked and average level of ratio of associated metabolic rate for a specific activity divided by the resting metabolic rate, on the job, correlated best with physical activity records (r = .11 to .47). Validation of these self-administered questionnaires in populations with a greater diversity of jobs and occupational energy requirements is needed.

Effects of recovery duration and blood lactate level on power output during cycling

This study identifies the quickest recovery between consecutive anaerobic tests to maintain power output (PO) on the repeated test. Sixteen male cyclists finished three sessions of max rpm initial and repeated 45-s cycling tests at 53.9 N. Tests were separated by 6, 9, or 12 min of recovery cycling (80 rpm, 9.8 N). Results showed no significant differences in PO between initial tests (M = 578.5 +/- 50 watts). PO was significantly less on the 6-min repeated test (M = 551.2 +/- 51) compared to the 9- (M = 575.1 +/- 53) and 12-min tests (M = 581.7 +/- 49.9) (p > 0.05). Net blood lactate [HLa] (repeated test-recovery) was significantly related to net PO (repeated test-initial test) on the 9- (r = 0.60, p < 0.05) and 12-min (r = 0.64, p < 0.001) trials, but not on the 6-min trial (r = 0.35, p = 0.19). In summary, at least 9 min of recovery cycling maintains PO on a repeated 45-s cycling test. Elevated [HLa] at the onset of high-intensity sprint exercise is moderately associated with PO on repeated cycle ergometer tests.

Approaches to physical activity in women

It is well known that regular, moderate-intensity exercise is beneficial in promoting good health and preventing disease and disability in women; however, high levels of sedentary behavior are observed in women of all races, incomes, and age groups. The determinants of exercise participation in women are poorly understood. Exercise intervention programs should be designed to increase women's general physical activity habits and enhance physical fitness. Exercise programs should include physical activities that are safe and increase gradually in the frequency, intensity, and duration of effort expended over time.

Validity and reliability of self-reported physical activity status: the Lipid Research Clinics questionnaire

We assessed the validity and reliability of the Lipid Research Clinics (LRC) physical activity (PA) questionnaire against measures of PA and physical fitness, and compared a new scoring system (four-point) with the method used in the LRC studies (two-point) in 28 men and 50 women. The two-point method classified participants as inactive or active based one question about regular, strenuous exercise habits. The four-point method classified participants as very low, low, moderate, and high active based on two questions; regular, strenuous exercise and self-rating of PA relative to peers. After adjusting for age and gender, the four-point method explained 17-29% of the variation in VO2max, percent body fat, and heavy-and light-intensity kcal.d-1 measured by the 4 wk history questionnaire (FWH). No association was found between the LRC ratings and Caltrac kcal and activity units and FWH total, moderate-intensity, and household PA kcal.d-1. Test-retest reliability was high (two-point, r = 0.85; four-point, r = 0.88). The LRC PA questionnaire is a relatively valid and reliable indicator of heavy PA in adults. The four-point method increases the ability to show graded associations between measures of cardiorespiratory fitness, body fatness, and leisure time PA.

Compendium of physical activities: classification of energy costs of human physical activities

A coding scheme is presented for classifying physical activity by rate of energy expenditure, i.e., by intensity. Energy cost was established by a review of published and unpublished data. This coding scheme employs five digits that classify activity by purpose (i.e., sports, occupation, self-care), the specific type of activity, and its intensity as the ratio of work metabolic rate to resting metabolic rate (METs). Energy expenditure in kilocalories or kilocalories per kilogram body weight can be estimated for all activities, specific activities, or activity types. General use of this coding system would enhance the comparability of results across studies using self reports of physical activity.

A simultaneous evaluation of 10 commonly used physical activity questionnaires

Ten commonly used physical activity questionnaires were evaluated for reliability and validity in 78 men and women aged 20-59, with varying physical activity habits. One month reliability was found to be high for all questionnaires except those pertaining only to the last week or month. Longer term test-retest reliability tended to be lower. Validity was studied in relation to treadmill exercise performance, vital capacity, body fatness, the average of 14 4-wk physical activity histories and the average of 14 2-d accelerometer readings. No questionnaire measure was correlated with the accelerometer reading, and correlations with vital capacity were generally low. Only the Minnesota Leisure Time Physical Activity Questionnaire household chores measure was correlated with habitual performance of household chores. Most questionnaires, even very simple ones, were related to performance of heavy intensity physical activity and treadmill performance; these same questionnaires tended to be related to percent body fat. Fewer questionnaires related to performance of light or moderate activity. Occupational activity was unrelated to any of the validation measures. It is concluded that there are multiple, nonoverlapping dimensions of physical activity, reflected in multiple nonoverlapping validation realms. More important than the length or attention to detail of a questionnaire seems to be the logic of its questions. Important areas of physical activity that should be addressed in future questionnaires include sleep, light, moderate and heavy intensity leisure activities, household chores, and occupational activity. Recent versus habitual activity should also be considered.

Computerized mental health risk appraisal for college students: user acceptability and correlation with standard pencil-and-paper questionnaires

Due to an interaction of age, birth cohort, genetics, and the lifestyle factors inherent in the "college experience," some college students are at increased risk for mental health problems such as alcohol, tobacco, and other drug abuse; depression; stress and anxiety; and eating disorders. A program to promote self-monitoring of students' health behaviors could prove beneficial to their future well-being and potentially reduce overall medical costs for this group. Computerized mental health risk appraisals, if valid, reliable, and acceptable to students and administrators, could facilitate implementation and minimize the costs of such a program. This pilot study was designed to determine whether a confidential computer-based risk appraisal is a valid and acceptable measure of current mental health status in a university student sample. Two basic questions were addressed. First, do computerized questionnaires yield results similar to their pencil-and-paper counterparts? Second, how do students rate and compare the two formats?

Leisure-time physical activity and aerobic fitness in African-American young adults

This cross-sectional study identified the leisure-time physical activity (LTPA) and aerobic fitness levels of 189 African-American young adult college freshmen. LTPA was measured with the Lipid Research Clinics (LRC), Godin Leisure-Time Exercise, and the College Alumnus physical activity questionnaires. The Physical Activity Index (PAI), an index of walking, stair climbing, and recreational sports participation, was obtained from the College Alumnus questionnaire. Aerobic fitness was measured indirectly with the Cooper 12-Minute Walking/Running Test. More women (82%) than men (53%) were classified as inactive (strenuous exercise or labor < 3 days/week and much less active than peers) or low active (strenuous exercise or labor < 3 days/week and as active or more active than peers) on the LRC Questionnaire. The PAI scores were moderately low in men (1,521 +/- 1,634 kcal.week-1) and very low in women (706 +/- 868 kcal.week-1). The majority of men (71%) and women (82%) were classified as 'very poor' in aerobic fitness levels. Body mass index (BMI), a measure of body fatness, was classified as 'overweight' or 'obese' for 39% of men and 37% of women (BMI = 25.9 +/- 5.7 kg/m2), reflecting inactive LTPA habits. These findings are consistent with studies showing low LTPA in middle-age African-American adults. School and community-level interventions are recommended to increase LTPA and aerobic fitness in adolescent and young adult African-Americans.

Vitamin C intake and lipid profiles of competitive male and female bodybuilders

This research compared nutrient intake data with blood lipids and anthropometric data. Height, weight, and seven skinfolds were collected 3 days prior to competition at the official weigh-in. The lipids measured were total cholesterol (TC), HDL-cholesterol (HDL-C), and the HDL2 and HDL3 cholesterol subfractions. The subjects were 17 males and 17 females. Descriptive data are presented as means and standard deviations of the means. Protein, fat, and carbohydrate provided about 40, 12, and 48%, respectively, of total energy intake; vitamin C was > 200 mg/day. Only dietary fat was significantly (p < 0.05) associated with TC for females. Fiber was significantly associated with HDL-C and HDL2-C for males and with HDL-C for females. Vitamin C was significantly associated with HDL-C,HDL2-C, and HDL3-C for males, and with HDL-C and HDL3-C for females. These findings are consistent with those reported by Bazzarre et al. in farmers and suggest that vitamin C may favorably influence HDL-C metabolism.

Physical activity and hypertension in black adults: the Pitt County Study

The relation of physical activity to hypertension was examined in 1751 Black adults in Pitt County, NC. More women (65%) than men (44%) were classified as sedentary. Sedentary behavior was not associated with the prevalence of hypertension in men, but was associated with a 31% increase in prevalence for women (sedentary-26.2%; active-20.0%; P less than .01). The association in women was independent of other risk factors for hypertension.