摘要:

SLAWTA, J. N., J. A. MCCUBBIN, A. R. WILCOX, S. D. FOX, D. J. NALLE, and G. ANDERSON. Coronary heart disease risk between active and inactive women with multiple sclerosis.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 905–912, 2002.PurposePhysical activity is strongly recommended as a principal component of coronary heart disease (CHD) risk factor management aimed at favorably lowering abdominal fat accumulation, lowering levels of triglyceride (TG), raising levels of high-density lipoprotein-cholesterol (HDL-C), and improving insulin sensitivity. Although physical activity practices are reported to be low in women with multiple sclerosis (MS), some women with MS remain physically active despite their disability. Thus, the primary aim of the study was to determine whether abdominal fat accumulation and levels of TG, HDL-C, and glucose differ between active and inactive women with MS.MethodsThe study sample consisted of 123 women with MS, aged 23–72 yr. Venous blood was collected for measurement of lipids, lipoprotein-cholesterol, and glucose. Skin-fold thicknesses and girth circumferences were obtained for estimation of total and abdominal body fat. Leisure-time physical activity (LTPA) during the last 12 months was assessed by the physical activity questionnaire used in the Postmenopausal Estrogens/Progestins Intervention (PEPI) Study. Eating habits were assessed by the Block Food Frequency Questionnaire.ResultsLTPA was significantly associated with lower waist circumference (P= 0.0001), lower TG levels (P= 0.0005), and lower glucose levels (0.002). After adjusting for several covariates, women participating in low- to moderate-intensity LTPA had significantly lower waist circumferences, TG levels, and glucose levels relative to inactive women.ConclusionLow- to moderate-intensity LTPA was significantly associated with less abdominal fat accumulation, lower levels of TG, and lower levels of glucose in the present sample of women with MS. These findings suggest that exercise levels attainable by women with MS may improve CHD risk and contribute to important health-related benefits.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

SLATTERY, M. L., and J. D. POTTER. Physical activity and colon cancer: confounding or interaction?Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 913–919, 2002.PurposeAlthough physical activity has been consistently inversely associated with colon cancer incidence, the association of physical activity with other diet and lifestyle factors that may influence this association is less well understood. Confounding and effect modification are examined to better understand the physical activity and colon cancer association.MethodsBased on hypothesized biological mechanisms whereby physical activity may alter risk of colon cancer, we evaluated confounding and effect modification using data collected as part of a case-control study of colon cancer (N= 1993 cases and 2410 controls). We examined associations between total energy intake, fiber, calcium, fruit and vegetables, red meat, whole grains as well as dietary patterns along with cigarette smoking, alcohol consumption, BMI, and use of aspirin and/or NSAIDs and physical activity.ResultsNo confounding was observed for the physical activity and colon cancer association. However, differences in effects of diet and lifestyle factors were identified depending on level of physical activity. Most striking were statistically significant interactions between physical activity and high-risk dietary pattern and vegetable intake, in that the relative importance of diet was dependent on level of physical activity. The predictive model of colon cancer risk was improved by using an interaction term for physical activity and other variables, including BMI, cigarette smoking, energy intake, dietary fiber, dietary calcium, glycemic index, lutein, folate, vegetable intake, and high-risk diet rather than using models that included these variables as independent predictors with physical activity. In populations where activity levels are high, the estimate of risk associated with high vegetable intake was 0.9 (95% CI 0.6–1.3), whereas in more sedentary populations the estimate of risk associated with high vegetable intake was 0.6 (95% CI 0.5–0.9).ConclusionsPhysical activity plays an important role in the etiology of colon cancer. Its significance is seen by its consistent association as an independent predictor of colon cancer as well as by its impact on the odds ratios associated with other factors. Given these observations, it is most probable that physical activity operates through multiple biological mechanisms that influence the carcinogenic process.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

NOSAKA, K., M. NEWTON, and P. SACCO. Muscle damage and soreness after endurance exercise of the elbow flexors.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 920–927, 2002.PurposeThis study investigated changes in indirect markers of muscle damage after endurance exercise of the elbow flexors and compared the changes with those after maximal eccentric actions (Max-ECC) of the elbow flexors.MethodsEighteen male students rhythmically lifted (1 s) and lowered (1 s) a light dumbbell (1.1–1.8 kg: 9% of MIF) in 60–180° of elbow joint angle for 2 h (2-h Ex). Maximal isometric force (MIF), relaxed (RANG) and flexed elbow joint angles (FANG), upper-arm circumference (CIR), muscle soreness (SOR), B-mode ultrasound (US), and plasma creatine kinase (CK) activity were assessed before and immediately after, and up to 96 h after exercise.ResultsAll measures were altered significantly (P< 0.05) after 2-h Ex in a similar time course to Max-ECC; however, changes in RANG, FANG, CIR, US, and CK (peak: 356 ± 121 IU·L−1) were significantly (P< 0.05) smaller compared with those after Max-ECC. SOR developed immediately after 2-h Ex and peaked 24–48 h after exercise. MIF dropped to 44.1% of the preexercise level, which was significantly (P< 0.05) lower than that after Max-ECC (58.1%), immediately postexercise. MIF recovered to 79.8% at 24 h, and 97.8% at 96 h postexercise, which was a significantly (P< 0.05) faster recovery compared with that of Max-ECC (73.1% at 96 h).ConclusionThese results showed low-intensity continuous muscle contractions (3600 times) resulted in muscle damage; however, the magnitude of the muscle damage was less severe, and the recovery was faster compared with 12 maximal eccentric muscle actions.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

W. H. COOKE, B. V. REYNOLDS, M. G. YANDL, J. R. CARTER, K. U. O. TAHVANAINEN, and T. A. KUUSELA. Effects of exercise training on cardiovagal and sympathetic responses to Valsalva’s maneuver.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 928–935, 2002.PurposeWe tested the hypothesis that a strictly-controlled program of aerobic conditioning would increase vagal and decrease sympathetic responses to Valsalva straining.MethodsEleven young men performed a maximal aerobic capacity test, controlled frequency breathing (0.25 Hz), and three Valsalva maneuvers before and after 4 wk of exercise training on a cycle ergometer (30 min at ≥ 70% max heart rate, 3 sessions · week−1). During controlled breathing and Valsalva straining, we recorded the electrocardiogram, noninvasive beat-by-beat arterial pressure, and peroneal nerve muscle sympathetic traffic at the popliteal fossa (pre- and postexercise sympathetic recordings were obtainable in 7 of 11 subjects). Vagal-cardiac tone was estimated from R-R interval standard deviations during controlled frequency breathing. Cardiovagal baroreflex sensitivity was derived from increases of R-R intervals as functions of increases in systolic pressures with linear regression analysis during phase IV pressure increases, and sympathetic sensitivity was derived from the quotient of total muscle sympathetic nerve activity and diastolic pressure changes during phase II pressure reductions.ResultsExercise training increased &OV0312;O2 max(3.38 ± 0.10 pre-, and 3.64 ± 0.11 L · min−1postexercise; mean ± SE;P= 0.04), R-R interval standard deviations (75 ± 0.12 pre- and 94 ± 0.14 ms postexercise; mean ± SE;P= 0.03), and cardiovagal baroreflex sensitivity (15.0 ± 1.1 pre-, and 25.0 ms · mm Hg−1± 4.0 postexercise; mean ± SE;P= 0.03). Exercise training did not change baseline sympathetic traffic (P= 0.31) or sympathetic nerve responses to diastolic pressure reductions (P= 0.12).ConclusionsExercise training affects vagal and sympathetic mechanisms differently: cardiovagal baroreflex sensitivity is increased, but sympathetic responses to arterial pressure decreases are unchanged.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

CHAPMAN, J., A. W. GARVIN, A. WARD, and G. D. CARTEE. Unaltered insulin sensitivity after resistance exercise bout by postmenopausal women.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 936–941, 2002.PurposeThe major aims of this study were to determine whether a single session of resistance exercise would alter insulin sensitivity, glucose effectiveness, and C-peptide response to glucose challenge in a group of previously sedentary, postmenopausal women.MethodsTen postmenopausal women (aged 57.5 ± 1.6 yr) were studied. Each participant underwent two frequently sampled intravenous glucose tolerance tests (FSIVGTT): without prior exercise (no exercise), and postexercise (15 h after a session of resistance exercise: three sets of 10 repetitions performed at 50%, 75%, and 100% of 10-repetition maximum for 7 exercises). Insulin sensitivity and glucose effectiveness were determined according to Bergman’s minimal model procedure. In addition, C-peptide concentration and glucose disappearance were measured.ResultsThere was no significant difference between trials for insulin sensitivity, glucose effectiveness, glucose disappearance, or area under the curve (AUC) for glucose or insulin during the glucose challenge. AUC for C-peptide tended (P= 0.059) to be 10% higher in the postexercise versus no exercise trial, and C-peptide values were significantly (P≤ 0.02) higher at several time points (60, 70, 140, and 180 min) during the postexercise compared with no exercise trial.ConclusionsIn contrast to previously reported results with young men and women after a single bout of endurance exercise, insulin sensitivity was unaltered by a single session of resistance exercise in postmenopausal women. Higher plasma C-peptide values concomitant with unchanged insulin values provide evidence that resistance exercise may have induced a slightly higher insulin secretion and a proportional increase in insulin clearance.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

N. K. CUMMINS and I. R. SPEARS. The effect of mouthguard design on stresses in the tooth-bone complex.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 942–947, 2002.PurposeMouthguards protect the tooth-bone complex from impact loads that occur during sporting activity. The aim of this study is to investigate the effects of varying mouthguard thickness and stiffness on the magnitude of tensile stresses in the tooth-bone-complex.MethodsA two-dimensional, plane stress, finite element representation of a central maxillary incisor (CMI) is created. For validation purposes, displacements of the incisal edge of the unprotected tooth model are compared within vivodisplacements under similar loads. A protective mouthguard is then superimposed over the model with varied labial thickness (1–6 mm) and stiffness (9–900MPa) representing a range of designs available. A large horizontal static load of 500N is then applied to the anterior surface of the mouthguard and the resulting stresses in the tooth-bone complex are presented. It is suggested that this loading condition most accurately represent the situation occurring when a guarded tooth collides with a soft object (e.g. boxing glove).ResultsIt is generally found that mouthguard thickness and stiffness are both desirable in terms of reducing stresses. However, the protection offered by the low-stiffness guards, regardless of thickness, is minimal. Since this low-stiffness (9MPa) is representative of the most common choice of material in mouthguard fabrication, such findings may cast doubt on the ability of popular mouthguards to redistribute stress.ConclusionWhile few would disagree that these low-stiffness guards absorb shock during hard-object collisions (e.g. baseballs), they may not protect the tooth-bone during soft-object collisions (e.g. boxing gloves). In order to optimize their protective capabilities for a range of loads, the range of materials used in mouthguard construction may have to be reconsidered.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

K. K. KALLIOKOSKI, P. NUUTILA, H. LAINE, M. LUOTOLAHTI, T. JANATUINEN, O. T. RAITAKARI, T. O. TAKALA, and J. KNUUTI. Myocardial perfusion and perfusion reserve in endurance-trained men.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 948–953, 2002.PurposeThis study was undertaken to determine whether endurance training is associated with changes in myocardial perfusion in humans.MethodsMyocardial perfusion was measured in eleven trained and nine sedentary men at rest and during adenosine-stimulated hyperemia using positron emission tomography (PET). Left ventricular (LV) dimensions and mass were measured using echocardiography. Myocardial work per gram of tissue was calculated as (cardiac output · mean arterial blood pressure)/LV mass.ResultsLV mass was significantly higher and myocardial work per gram of tissue lower in the trained than in the untrained subjects. Basal (0.78 ± 0.10 and 0.76 ± 0.15 mL · min−1· g−1,P= NS) and adenosine-stimulated perfusion (3.46 ± 0.91 and 3.14 ± 0.70 mL · min−1· g−1,P= NS) were similar between trained and untrained men, respectively. Consequently, myocardial perfusion reserve was similar in both groups (4.4 ± 1.2 and 4.1 ± 0.7,P= NS). In addition, coronary resistance at baseline (115 ± 17 vs 119 ± 22, mm Hg · mL · min−1· g−1,P= NS) and during adenosine infusion (28 ± 8 vs 30 ± 8, mm Hg · mL · min−1· g−1,P= NS) were similar in both groups. Resting myocardial work correlated with resting myocardial perfusion in both groups, but the relationship between perfusion and work was different between the groups so that perfusion for a given myocardial work was significantly higher in trained subjects (0.56 ± 0.04 and 0.34 ± 0.05 mL · (mm Hg · L)−1,P< 0.001).ConclusionsThese findings suggest that endurance trained subjects do not have different resting or adenosine-stimulated myocardial perfusion. However, the relationship between myocardial perfusion and work appears altered in the athletes.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

ZAVORSKY, G. S., S. F. VAN EEDEN, K. R. WALLEY, and J. A. RUSSELL. Circulating white blood cells affect red cell pulmonary transit times in endurance athletes during intense exercise.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 954–959, 2002.PurposeThe aim of this study was to determine the relationship between the right-to-left ventricular red cell pulmonary transit times (PTT) during intense exercise and circulating white blood cell (WBC) counts in highly trained endurance athletes. We postulated that high levels of WBCs preexercise would slow PTT. Eleven endurance-trained athletes (&OV0312;O2max= 69.6 ± 7.7 mL·kg−1·min−1; weight = 75.0 ± 6.2 kg; height = 181.0 ± 7.1 cm) performed 6.5 min constant-load, near-maximal cycling exercise (∼92% &OV0312;O2max) on two different days. Preexercise WBC counts were measured in arterial blood drawn from the radial artery 30 min before exercise. PTT was measured during the 3rd min of exercise by first-pass radionuclide cardiography using centroid and deconvolution analysis, whereas cardiac output (&OV0422;) was measured during the last 2.5 min of exercise via a count-based ratio method from the MUGA technique.ResultsCombined mean PTT from both deconvolution and centroid analysis at minute three of exercise was 2.45 ± 0.21 s, whereas the preexercise WBC count was 5.3 ± 1.6 × 109·L−1. Cardiopulmonary blood volume at minute three of exercise was 1.22 ± 0.13 L, &OV0312;O2was 4.58 ± 0.44 L·min−1, and &OV0422; was 30.2 ± 4.2 L·min−1. We found that PTT was negatively correlated with circulating WBC (r = −0.61; adjusted r2= 0.30;P= 0.04;N= 11) but not with the dispersion (spread) of transit times around the mean (r = 0.19;P= 0.57).ConclusionThis suggests that athletes with higher circulating numbers of WBCs preexercise have faster (shorter) red cell transit times through the lung during intense exercise.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

WELSCH, M. A., J. D. ALLEN, and J. P. GEAGHAN. Stability and reproducibility of brachial artery flow-mediated dilation.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 960–965, 2002.PurposeBrachial artery flow-mediated dilation (BAFMD) is a noninvasive technique, which has been suggested as a potential means of identifying patients with early atherosclerosis and therefore has enormous clinical appeal. Despite this, the stability and reproducibility of this technique are not yet clear. Therefore, the purpose of this study was to establish the stability and reproducibility of BAFMD after 5 min of forearm occlusion and to produce power calculations to aid in clinical trial design.MethodsTwenty-six healthy volunteers underwent high-resolution ultrasonographic brachial artery assessments before, during, and after 5 min of forearm occlusion. The study design involved three scans on 2 d, performed by two ultrasonographers and analyzed by two readers. All subjects were tested between 7 and 11 a.m. after refraining from food and exercise. The nondominant arms were scanned, in longitudinal view, approximately 4 cm proximal to the olecranon process, in the anterior/medial plane. Blood draws were performed on each visit. The SAS MIXED restricted maximum likelihood (REML) procedure for an unbalanced design was used to calculate variance components and provide power calculations.ResultsAverage baseline artery diameter for all studies was 3.48 ± 0.53 mm. This increased to 3.71 ± 0.57 mm (6.58 ± 4.15%) at peak dilation. Intraclass correlation coefficients (ICCC) for days, testers, and readers were 0.92, 0.94, and 0.90, respectively. To detect a difference in vasoreactivity of 60% (two-tailed), e.g., 5% vasodilation versus 8% vasodilation, at 90% power, 23 and 10 subjects would be required for cross-sectional and pre-post designs, respectively.ConclusionsThese data indicate adequate stability and reproducibility of the BAFMD technique under controlled conditions. Additionally, BAFMD appears useful to differentiate between groups, although its prognostic value for the examination of individuals is unclear.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

MARTINO, M., N. GLEDHILL, and V. JAMNIK. High &OV0312;O2maxwith no history of training is primarily due to high blood volume.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 966–971, 2002.PurposeTo investigate the high &OV0312;O2maxobserved occasionally in young men who have no history of training.Methods&OV0312;O2max, blood volume (BV), maximal stroke volume (SVmax), maximal cardiac output (&OV0422;max), and related measurements (reported as mean ± SEM) were studied in six men (mean age 20.0 ± 0.5 yr) with no history of training, who all had a &OV0312;O2maxbelow 49 mL·kg−1·min−1(LO group) and six age- and weight-matched men (mean age 19.5 ± 0.5 yr) with no history of training, who all had a &OV0312;O2maxabove 62.5 mL·kg−1·min−1(HI group).ResultsCompared with the LO group, the HI group had a higher SVmax(149 ± 5 vs 102 ± 5 mL), higher &OV0422;max(28.9 ± 0.9 vs 20.0 ± 1.0 L·min−1) and higher BV (88.1 ± 3.8 vs 76.7 ± 0.9 mL·kg−1). The BV of four participants in the HI group (mean = 92.3 ± 4.3 mL·kg−1) was substantially higher than the BV of all participants in the LO group, but two participants in the HI group had a BV (mean = 79.7 ± 0.8 mL·kg−1) that was similar to the mean BV of the LO group.ConclusionThe primary explanation for the high &OV0312;O2maxobserved occasionally in young men who have no history of training is a naturally occurring (perhaps genetically determined) high BV that brings about a high SVmaxand &OV0422;max. However, some young men with no history of training have a high &OV0312;O2max, SVmax, and &OV0422;maxpossibly because a greater portion of their BV is hemodynamically active.

ISSN:0195-9131    

出版商:OVID    

年代:2002

数据来源: OVID