Allen W. Jackson

Association between muscular strength and mortality in men: prospective cohort study

Objective To examine prospectively the association between muscular strength and mortality from all causes, cardiovascular disease, and cancer in men. Design Prospective cohort study. Setting Aerobics centre longitudinal study. Participants 8762 men aged 20-80. Main outcome measures All cause mortality up to 31 December 2003; muscular strength, quantified by combining one repetition maximal measures for leg and bench presses and further categorised as age specific thirds of the combined strength variable; and cardiorespiratory fitness assessed by a maximal exercise test on a treadmill. Results During an average follow-up of 18.9 years, 503 deaths occurred (145 cardiovascular disease, 199 cancer). Age adjusted death rates per 10 000 person years across incremental thirds of muscular strength were 38.9, 25.9, and 26.6 for all causes; 12.1, 7.6, and 6.6 for cardiovascular disease; and 6.1, 4.9, and 4.2 for cancer (all P<0.01 for linear trend). After adjusting for age, physical activity, smoking, alcohol intake, body mass index, baseline medical conditions, and family history of cardiovascular disease, hazard ratios across incremental thirds of muscular strength for all cause mortality were 1.0 (referent), 0.72 (95% confidence interval 0.58 to 0.90), and 0.77 (0.62 to 0.96); for death from cardiovascular disease were 1.0 (referent), 0.74 (0.50 to 1.10), and 0.71 (0.47 to 1.07); and for death from cancer were 1.0 (referent), 0.72 (0.51 to 1.00), and 0.68 (0.48 to 0.97). The pattern of the association between muscular strength and death from all causes and cancer persisted after further adjustment for cardiorespiratory fitness; however, the association between muscular strength and death from cardiovascular disease was attenuated after further adjustment for cardiorespiratory fitness. Conclusion Muscular strength is inversely and independently associated with death from all causes and cancer in men, even after adjusting for cardiorespiratory fitness and other potential confounders.

Effects of exercise training on men seropositive for the human immunodeficiency virus-1

We examined the effects of chronic exercise on fitness and immune status in Caucasian males (34.9 +/- 5.6 yr) diagnosed by Western blot as seropositive for the HIV-1 virus. The exercise regimen involved 12 wk of 1 h sessions 3 d.wk: 20 min of cycle exercise at 60-80% HRreserve was followed by 35 min of strength and flexibility training. After matching subjects on health status (modified Walter Reed criteria), subjects (N = 37) were randomly assigned to exercise or a counseling control condition. Changes in strength, responses to the YMCA cycle test, and serum lymphocytes were tested by MANOVA in a condition (exercise or counseling)-by-time (pretest, posttest) design with repeated measures on time. Results indicated significant (P less than 0.001) group-by-time interactions for strength (N.m) (chest press and leg extension) and for HR (beats.min-1) and total time (TT) on the cycle test at 150 W. Strength and TT increased and HR decreased in the exercise condition, while control subjects did not change. Total leukocyte, lymphocyte, CD4+, and CD8+ cell counts, and the CD4+/CD8+ ratio were statistically unchanged for each condition. We conclude that HIV-1+ men, including those symptomatic for AIDS-related complex, can experience significant increases in neuromuscular strength and cardiorespiratory fitness without changes in lymphocyte phenotypes or clinical diagnosis when the exercise regimen is prescribed and monitored in accordance with ACSM guidelines for healthy adults.

The Relationship of the Sit and Reach Test to Criterion Measures of Hamstring and Back Flexibility in Young Females

Abstract The purpose of the present investigation was to determine the relationships of the sit and reach test, a component of the American Alliance for Health, Physical Education, Recreation and Dance Health Related Fitness Test, 1980, with criterion measures of back and hamstring flexibility. Young females (N = 100) with a mean age of 14.08 years ± .825 were administered two trials of three tests. The measurements included the sit and reach test, passive hamstring flexibility using a Leighton Flexometer, and a test of back flexibility using a protocol suggested by Macrae and Wright in 1969. Test-retest reliability estimates exceeded .90 for all measurements. Results indicated that the sit and reach test had a moderate relationship (r = .64) with passive hamstring flexibility. The correlations between the sit and reach test and total back flexibility (r = .07), upper back flexibility (r = −.16), and lower back flexibility (r = .28) were low. These findings indicate the sit and reach test has moderate cri...

The relationship of body mass index, medical costs, and job absenteeism.

OBJECTIVES To assess the relationship between body mass index, as categorized by the recently released guidelines of the NHLBI, and health care costs and absenteeism in a sample of municipal workers. METHODS A cross-sectional study was employed that compared the obesity-related health care costs and absences of normal and overweight/obese city workers. RESULTS While accounting for age, gender, race, smoking behavior, and educational attainment, BMI predicted both average annual health-care costs and work absence hours. CONCLUSIONS The NHLBI guidelines for overweight and obesity effectively predicted absences and health care costs.

The Association of Health-Related Fitness with Indicators of Academic Performance in Texas Schools

This study examined the associations between indicators of health-related physical fitness (cardiovascular fitness and body mass index) and academic performance (Texas Assessment of Knowledge and Skills). Partial correlations were generally stronger for cardiovascular fitness than body mass index and consistently stronger in the middle school grades. Mixed-model regression analyses revealed modest associations between fitness and academic achievement after controlling for potentially confounding variables. The effects of fitness on academic achievement were positive but small. A separate logistic regression analysis indicated that higher fitness rates increased the odds of schools achieving exemplary/recognized school status within the state. School fitness attainment is an indicator of higher performing schools. Direction of causality cannot be inferred due to the cross-sectional nature of the data.

Genucom, KT-1000, and Stryker knee laxity measuring device comparisons Device reproducibility and interdevice comparison in asymptomatic subjects

Generally, three devices (the Genucom Knee Analysis System, the MEDmetric KT-1000 Arthrometer, and the Stryker Knee Laxity Tester), which have been pre sented in the literature, may be used to assess clinically the amount of knee laxity in an objective manner. This study compared the reproducibility of the anterior and posterior knee laxity values for each and made direct comparisons of the results obtained. Thirty asympto matic subjects were given a test-retest protocol on both legs with all three devices. Devices were tested in a counterbalanced order. Repeatability of test values within devices was variable, but all were acceptable, the lowest being r = 0.74. Analysis of variance (AN- OVA), and correlational analysis revealed that device- specific anterior and posterior laxity values were pro duced. We concluded that each commercially available knee laxity testing device can provide reproducible quantitative measurements of knee laxity; however, due to differences in device sensitivities and functional design, numerical results from one device cannot be generalized to another device.

Reliability and Validity Issues concerning Large-Scale Surveillance of Physical Activity

The BRFSS is our major source of population-based information on physical activity in the United States. The top priority for the immediate future should be to make sure that the information obtained from the BRFSS in its current form is both reliable and valid. As outlined in this report, this task could be completed in relatively short time frame and at reasonable cost in terms of both financial and human resources. The development of an additional module to assess light-to-moderate activity and strength is currently underway with support from the CDC. As suggested in this report, this task may prove to be extremely difficult, or it may be difficult to develop an instrument of this type given the constraints of a population based telephone survey. The current focus on the health benefits of moderate activity and the interest in tracking this type of activity behavior on a population basis as it relates to national physical activity objectives both argue in favor of developing a physical activity assessment instrument that provides a valid and reliable measurement of moderate activity. Given the complexity and uncertainty of this task it is important to develop a procedure that will allow for periodic evaluation of progress and the potential for success to minimize the risk of making a considerable financial investment in an instrument that may be of limited utility.

Muscular Strength and Adiposity as Predictors of Adulthood Cancer Mortality in Men

Background: We examined the associations between muscular strength, markers of overall and central adiposity, and cancer mortality in men. Methods: A prospective cohort study including 8,677 men ages 20 to 82 years followed from 1980 to 2003. Participants were enrolled in The Aerobics Centre Longitudinal Study, the Cooper Institute in Dallas, Texas. Muscular strength was quantified by combining 1-repetition maximal measures for leg and bench presses. Adiposity was assessed by body mass index (BMI), percent body fat, and waist circumference. Results: Cancer death rates per 10,000 person-years adjusted for age and examination year were 17.5, 11.0, and 10.3 across incremental thirds of muscular strength (P = 0.001); 10.9, 13.4, and 20.1 across BMI groups of 18.5-24.9, 25.0-29.9, and ≥30 kg/m2, respectively (P = 0.008); 11.6 and 17.5 for normal (<25%) and high percent body fat (≥25%), respectively (P = 0.006); and 12.2 and 16.7 for normal (≤102 cm) and high waist circumference (>102 cm), respectively (P = 0.06). After adjusting for additional potential confounders, hazard ratios (95% confidence intervals) were 1.00 (reference), 0.65 (0.47-0.90), and 0.61 (0.44-0.85) across incremental thirds of muscular strength, respectively (P = 0.003 for linear trend). Further adjustment for BMI, percent body fat, waist circumference, or cardiorespiratory fitness had little effect on the association. The associations of BMI, percent body fat, or waist circumference with cancer mortality did not persist after further adjusting for muscular strength (all P ≥ 0.1). Conclusions: Higher levels of muscular strength are associated with lower cancer mortality risk in men, independent of clinically established measures of overall and central adiposity, and other potential confounders. (Cancer Epidemiol Biomarkers Prev 2009;18(5):1468–76)

American Adults' Knowledge of Exercise Recommendations

Abstract Physical inactivity is a major risk factor for cardiovascular disease, stroke, hypertension, diabetes, obesity, osteoporosis, and some cancers. Approximately 950,000 Americans die annually from cardiovascular diseases. The purpose of this study was to determine whether American adults know which traditional and lifestyle physical activities affect health and how they should be physically active to achieve a health benefit. Secondary purposes were to determine whether this knowledge is a function of gender, ethnicity, education, or age and if those who are sufficiently active for a health benefit possess different knowledge levels than those not sufficiently active for a health benefit. Items based on the Centers for Disease Control and Prevention/American College of Sports Medicine principles included knowledge of exercise guidelines and traditional and lifestyle physical activities. This information was obtained from 20 questions that were part of a national random telephone survey of 2,002 American households in the 48 contiguous states and the District of Columbia. Respondents were most aware of traditional physical activities (M = 94%) that provide a health benefit and less aware of specific exercise guidelines (M = 68%) and lifestyle physical activities (M = 71%) that can result in a health benefit. Knowledge was not related to physical activity behavior sufficient for a health benefit and only slightly related to ethnicity, education, and age. These data suggest that physical activity knowledge alone is not sufficient to elicit a behavior; however, it provides educators with an understanding of the publics physical activity knowledge that could be helpful in developing health promotion and physical activity interventions.

KT-1000 arthrometer: Conscious and unconscious test results using 15, 20, and 30 pounds of force

A recent published report indicated that the reliability and validity of anterior laxity measurements obtained by using the KT-1000 arthrometer were questionable. The purpose of our study was to examine the diagnos tic validity of anterior laxity measurements testing pa tients in conscious and unconscious states using the KT-1000 arthrometer at 15, 20, and 30 pounds of force. The sample included 68 patients with confirmed ante rior cruciate ligament disruption. They were given an terior-posterior drawer tests at 20° in both unconscious and conscious states; measurements were recorded at 15, 20, and 30 pounds of force. The results indicated that the measurements in the unconscious state were significantly higher (P < 0.01) than the values obtained in the conscious state. The anterior cruciate ligament- disrupted knees produced significantly higher (P < 0.01) anterior laxity. The difference between anterior cruciate ligament-disrupted knees and normal knees grew sig nificantly larger (P < 0.01) as force increased. More patients demonstrated a difference >2 mm between anterior cruciate ligament-disrupted knees and normal knees at 30 pounds (81 % to 83%) than at 20 pounds (64% to 72%) of force. Seventy-nine percent of the patients demonstrated a compliance index difference >1 mm using 15 and 30 pounds between the normal and anterior cruciate ligament-disrupted knee. These data provide statistical validity for the compliance index and support for the use of anterior laxity measurements at 30 pounds of force. However, approximately 20% of these patients did not demonstrate an anterior cruciate ligament-disrupted-normal knee difference >2 mm or a compliance index difference of >1 mm.