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PubMed2006

Age-related loss of associations between acute exercise-induced IL-6 and oxidative stress.

IL-6 mediates many aspects of the exercise-induced acute-phase response, including upregulation of antioxidant defenses. Moreover, IL-6 synthesis is regulated in part by oxidative stress. This investigation tested the hypothesis that an IL-6-mediated acute-phase response after exercise provides negative-feedback protection against exercise-induced oxidative stress. Healthy young (n = 16, 26.4 +/- 1.8 yr) and older men (n = 16, 71.1 +/- 2.0 yr) ran downhill for 45 min at 75% maximal oxygen consumption before and after a 12-wk period of supplementation with vitamin E (1,000 IU/day) or placebo. Circulating IL-6 and soluble IL-6 receptors, peripheral mononuclear cell production of IL-6, and IL-6 transcripts in muscle were measured before and within a 72-h time window after each acute exercise bout. At all time points plasma IL-6, IL-6 bioavailability, and C-reactive protein were higher in the older men; yet in response to exercise, young and older subjects experienced similar increases in these factors. Although the magnitude of postexercise changes in acute-phase variables was independent of age, correlations among plasma, mononuclear cell, and muscle IL-6 and oxidative stress were evident only in young men (R2 = 0.64, 0.35, and 0.33, respectively). These changes in circulating IL-6 were closely associated with a prooxidant state (R2 = 0.47), whereas muscle IL-6 mRNA correlated with an antioxidant state (R2 = 0.65). Supplementation with vitamin E did not affect exercise-induced responses or differences between the young and old men in a consistent manner. Therefore, oxidative stress is linked to the acute-phase response after exercise in young men, but not in older men who had elevated acute-phase reactants, suggesting that further research is warranted to determine the basis for these differences.

Acute-Phase Reaction↗
PubMed2005

Relationship among diastolic intraventricular pressure gradients, relaxation, and preload: impact of age and fitness.

Diastolic intraventricular pressure gradients (IVPGs) are a measure of the ability of the ventricle to facilitate its filling using diastolic suction. We assessed 15 healthy young but sedentary subjects, aged <50 yr (young subjects; age, 35 +/- 9 yr); 13 healthy but sedentary seniors, aged >65 yr with known reductions in ventricular compliance (elderly sedentary subjects; age, 70 +/- 4 yr); and 12 master athletes, aged >65 yr, previously shown to have preserved ventricular compliance (elderly fit subjects; age, 68 +/- 3 yr). Pulmonary capillary wedge pressure (PCWP) and echocardiography measurements were performed at baseline, during load manipulation by lower body negative pressure at -15 and -30 mmHg, and after saline infusion of 10 and 20 ml/kg (elderly) or 15 and 30 ml/kg (young). IVPGs were obtained from color M-mode Doppler echocardiograms. Baseline IVPGs were lower (1.2 +/- 0.4 vs. 2.4 +/- 0.7 mmHg, P < 0.0001), and the time constant of pressure decay (tau(0)) was longer (60 +/- 10 vs. 46 +/- 6 ms, P < 0.0001) in elderly sedentary than in young subjects, with no difference in PCWP. Although PCWP changes during load manipulations were similar (P = 0.70), IVPG changes were less prominent in elderly sedentary than in young subjects (P = 0.02). Changes in stroke volume and IVPGs during loading manipulations correlated (r = 0.96, P = 0.0002). PCWP and tau(0) were strong multivariate correlates of IVPGs (P < 0.001, for both). IVPG response to loading interventions in elderly sedentary and elderly fit subjects was similar (P = 0.33), despite known large differences in ventricular compliance. The ability to regulate IVPGs during changes in preload is impaired with aging. Preserving ventricular compliance during aging by lifelong exercise training does not prevent this impairment.

Adult↗
PubMed1981

Muscular endurance and surface electromyogram in isometric and dynamic exercise.

In nine male volunteers, the endurance time for sustained isometric exercise (right-angle elbow flexion) and dynamic exercise (continuous concentric and eccentric elbow flexions) was measured at different contraction levels. Intermittent isometric exercises were also performed by four of the subjects in whom surface electromyographic elbow flexor recordings were obtained during the three types of exercise. A rapid decrease of the endurance time was seen at contraction levels above 15-20% of the maximum voluntary contraction for both the sustained isometric and dynamic exercise. There were no significant difference between the regression of the endurance time vs. the contraction level for the sustained isometric exercise and that of the dynamic exercise. However, the endurance time was enhanced in the intermittent isometric exercise compared with the sustained isometric exercise. The development of muscle fatigue was well correlated to change of the myoelectric rootmean-square amplitude and the mean power frequency. Differences in exercise did not significantly affect the relation between the time constant of the mean power frequency decrease and the endurance time.

Adult↗
PubMed1996

Effect of past gymnastics participation on adult bone mass.

The purposes of this study were to determine bone mineral density (BMD) of former female college gymnasts (FG; n = 18) and controls (FC; n = 15) by using dual-energy X-ray absorptiometry (Hologic QDR 1000W) and to examine the relationships between current and former activity levels, diet, menstrual history and BMD. Current physical activity, dietary intake, and menstrual irregularity were assessed with the use of standardized questionnaires. A study-designed questionnaire was used to assess past physical activity. The BMDs of the FG were significantly higher (P < 0.001) than the BMDs of FC for the lumbar spine, femoral neck, Ward's triangle, and whole body, even when the influences of current and past physical activity levels were statistically controlled via analysis of covariance. FG and FC did not differ in nutrient intakes, and there were no BMD differences between FG who always had regular menstrual cycles vs. those who had an interruption (> or = 3 mo) of their menstrual cycle in the past. The higher BMD in FG compared with FC suggests that past participation in college gymnastics may provide a residual effect on adult BMD.

Adult↗
PubMed2004

Inflection points of cardiovascular responses and oxygenation are correlated in the distal but not the proximal portions of muscle during incremental exercise.

To test whether there is a regional difference in the exercise pressor reflex within a given muscle, we investigated the relationship between the inflection points of cardiovascular responses and muscle oxygenation during exercise. Seven subjects performed incremental exercise, which consisted of incremental 30-s static knee extensions, each separated by 30 s of recovery. The workload started at 5% maximal voluntary contraction (MVC) and increased by 5% MVC for each increment until exhaustion. Changes (Delta) in the concentrations (denoted by brackets) of oxygenated Hb (O2Hb) and deoxygenated Hb (HHb) were monitored in proximal and distal portions of the vastus lateralis by near-infrared spectroscopy. The inflection points of mean arterial pressure (MAP), calf vascular resistance (CVR), and muscle deoxygenation index (Delta[O2Hb-HHb]) were calculated as the intersection point of two regression equations obtained at lower and higher workloads. The inflection point of Delta[O2Hb-HHb] differed significantly between proximal and distal portions (28.5 +/- 3.0 vs. 39.5 +/- 3.0%MVC, P < 0.05). Linear regression analysis showed significant correlations between the inflection point of Delta[O2Hb-HHb] in the distal portion and MAP (r = 0.89; P < 0.01) and CVR (r = 0.89; P < 0.05), but no significant relationship between the inflection point in the proximal portion and MAP or CVR. These data show that the inflection point of muscle deoxygenation differs between proximal and distal portions within the vastus lateralis during incremental exercise and suggest that the distal portion of the vastus lateralis contributes more to the pressor response than does the proximal portion.

Adaptation, Physiological↗
PubMed2004

Muscle contraction-blood flow interactions during upright knee extension exercise in humans.

To test for evidence of a muscle pump effect during steady-state upright submaximal knee extension exercise, seven male subjects performed seven discontinuous, incremental exercise stages (3 min/stage) at 40 contractions/min, at work rates ranging to 60-75% peak aerobic work rate. Cardiac cycle-averaged muscle blood flow (MBF) responses and contraction-averaged blood flow responses were calculated from continuous Doppler sonography of the femoral artery. Net contribution of the muscle pump was estimated by the difference between mean exercise blood flow (MBFM) and early recovery blood flow (MBFR). MBFM rose in proportion with increases in power output with no significant difference between the two methods of calculating MBF. For stages 1 and 5, MBFM was greater than MBFR; for all others, MBFM was similar to MBFR. For the lighter work rates (stages 1-4), there was no significant difference between exercise and early recovery mean arterial pressure (MAP). During stages 5-7, MAP was significantly higher during exercise and fell significantly early in recovery. From these results we conclude that 1) at the lightest work rate, the muscle pump had a net positive effect on MBFM, 2) during steady-state moderate exercise (stages 2-4) the net effect of rhythmic muscle contraction was neutral (i.e., the impedance due to muscle contraction was exactly offset by the potential enhancement during relaxation), and 3) at the three higher work rates tested (stages 5-7), any enhancement to flow during relaxation was insufficient to fully compensate for the contraction-induced impedance to muscle perfusion. This necessitated a higher MAP to achieve the MBFM.

Adaptation, Physiological↗
PubMed2006

Elevated peak exercise systolic blood pressure is not associated with reduced exercise capacity in subjects with Type 2 diabetes.

Subjects with Type 2 diabetes without cardiovascular disease have a reduced exercise capacity compared with nondiabetic subjects. However, the mechanisms responsible for this phenomenon are unknown. The purpose of this study was to evaluate the impact of exercise systolic blood pressure (SBP) response on diverse exercise tolerance parameters in Type 2 diabetic subjects. Twenty-eight sedentary men with Type 2 diabetes were recruited for this study. Subjects were treated with oral hypoglycemic agents and/or diet. Evaluation of glycemic control and peak exercise capacity were performed for each subject. The subjects were divided into two groups according to the median value of peak SBP (210 mmHg) measured in each subject. We observed a 13, 13, and 16% reduction in the relative peak oxygen uptake (V(O2 peak)), absolute V(O2 peak), and peak work rate in the low- compared with the high-peak SBP group [26.95 (SD 5.35) vs. 30.96 (SD 3.61) ml.kg(-1).min(-1), 2.5 (SD 0.4) vs. 2.8 (SD 0.6) l/min, and 169 (SD 34) vs. 202 (SD 32) W; all P < 0.05]. After adjusting for age, relative V(O2 peak) was still significantly different (P < 0.05). There were similar peak respiratory exchange ratio (RER) [1.20 (SD 0.08) vs. 1.16 (SD 0.07); P = 0.24] and peak heart rate [160 (SD 20) vs. 169 (SD 15) beats/min; P = 0.18] between the low- compared with the high-SBP group. No difference in glycemic control was observed between the two groups. The results reported in this study suggest that in subjects with Type 2 diabetes without cardiovascular disease, an elevated exercise SBP is not associated with reduced exercise capacity and its modulation is probably not related to glycemic control.

Blood Pressure↗
PubMed2003

Physical exercise can influence local levels of matrix metalloproteinases and their inhibitors in tendon-related connective tissue.

Microdialysis studies indicate that mechanical loading of human tendon tissue during exercise or training can affect local synthesis and degradation of type I collagen. Degradation of collagen and other extracellular matrix proteins is controlled by an interplay between matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). However, it is unknown whether local levels of MMPs and TIMPs are affected by tendon loading in humans in vivo. In the present experiment, six healthy young men performed 1 h of uphill (3%) treadmill running. Dialysate was collected from microdialysis probes (placed in the peritendinous tissue immediately anterior to the Achilles tendon) before, immediately after, 1 day after, and 3 days after an exercise bout. MMP-2 and MMP-9 were measured in dialysate by gelatin zymography, and amounts were quantified by densitometry in relation to total protein in the dialysate. TIMP-1 and TIMP-2 were analyzed by reverse gelatin zymography and semiquantitated visually. Pro-MMP-9 increased markedly after exercise and remained high for 3 days after exercise. Pro-MMP-2 dropped from the basal level immediately after exercise and remained low 1 day after exercise but was slightly elevated 3 days after exercise. The MMP-2 inhibitory activity of TIMP-1 was clearly elevated 1 and 3 days after exercise, and the MMP-2 inhibitory activity of TIMP-2 rose 1 day after loading. The present findings demonstrate enhanced interstitial amounts of MMPs and TIMPs after exercise in the human peritendinous tissue in vivo, and the magnitude and time pattern of these changes may well indicate that MMPs and TIMPs are playing a role in extracellular matrix adaptation to exercise in tendon tissue.

Achilles Tendon↗
PubMed2005

Elastic properties of human Achilles tendon are correlated to muscle strength.

The purpose of this study was to investigate whether the mechanical properties of the Achilles tendon were correlated to muscle strength in the triceps surae in humans. Twenty-four men and twelve women exerted maximal voluntary isometric plantar flexion (MVIP) torque. The elongation (DeltaX) and strain of the Achilles tendon (epsilon), the proximal part of which is the composite of the gastrocnemius tendon and the soleus aponeurosis, at MVIP were determined from the displacement of the distal myotendinous junction of the medial gastrocnemius using ultrasonography. The Achilles tendon force at MVIP (F) was calculated from the MVIP torque and the Achilles tendon moment arm. There were no significant differences in either the F-DeltaX or F-epsilon relationships between men and women. DeltaX and epsilon were 9.8 +/- 2.6 mm and 5.3 +/- 1.6%, respectively, and were positively correlated to F (r = 0.39, P < 0.05; r = 0.39, P < 0.05), which meant that subjects with greater muscle strength could store more elastic energy in the tendon. The regression y-intercepts for the F-DeltaX (P < 0.01) and F-epsilon (P < 0.05) relationship were significantly positive. These results might indicate that the Achilles tendon was stiffer in subjects with greater muscle strength, which may play a role in reducing the probability of tendon strain injuries. It was suggested that the Achilles tendon of subjects with greater muscle strength did not impair the potential for storing elastic energy in tendons and may be able to deliver the greater force supplied from a stronger muscle more efficiently. Furthermore, the difference in the Achilles tendon mechanical properties between men and women seemed to be correlated to the difference in muscle strength rather than gender.

Adult↗
PubMed2004

Sympathetic neural regulation in endurance-trained humans: fitness vs. fatness.

We tested the hypothesis that muscle sympathetic nerve activity (MSNA) would be higher in endurance-trained (ET) compared with sedentary (Sed) men with similar levels of total body and abdominal adiposity. We further hypothesized that sympathetic baroreflex gain would be augmented in ET compared with Sed men independent of the level of adiposity. To address this, we measured MSNA (via microneurography), sympathetic and vagal baroreflex responses (the modified Oxford technique), body composition (dual-energy X-ray absorptiometry), and waist circumference (Gulick tape) in Sed (n = 22) and ET men (n = 8). The ET men were also compared with a subgroup of Sed men (n = 6) with similar levels of total body and abdominal adiposity. Basal MSNA was greater in the ET compared with Sed men with similar levels of total body and abdominal adiposity (28 +/- 2.0 vs. 21 +/- 2.0 bursts/min; P < 0.05) but similar to the larger group of Sed men (n = 22) with higher total body and abdominal adiposity (vs. 26 +/- 3 bursts/min; P > 0.05). In contrast to our hypothesis, sympathetic baroreflex gain was lower in the ET compared with Sed men (-6.4 +/- 0.8 vs. -8.4 +/- 0.4 arbitrary integrative units x beat(-1) x mmHg(-1); P < 0.05) regardless of the level of adiposity. Taken together, the results of the present study suggest that MSNA is higher in ET compared with Sed men with similar levels of total body and abdominal adiposity. In addition, sympathetic baroreflex gain is lower in ET compared with Sed men. That sympathetic baroreflex gain was lower in ET compared with Sed men regardless of the level of adiposity suggests an influence of the ET state per se.

Adipose Tissue↗
PubMed2006

Markers of inflammation are inversely associated with VO2 max in asymptomatic men.

We investigated whether markers of inflammation, including a cytokine (IL-6), acute-phase reactants [C-reactive protein (CRP) and fibrinogen], and white blood cell (WBC) count are associated with maximal O(2) consumption (Vo(2 max)) in men without coronary heart disease (CHD). In asymptomatic men (n = 172, 51 +/- 9.3 yr old), Vo(2 max) was measured during a symptom-limited graded treadmill exercise test. Physical activity level was assessed by a standardized questionnaire. IL-6 and CRP were measured by immunoassays, fibrinogen by the Clauss method, and WBC count with a Coulter counter. IL-6 and CRP were logarithmically transformed to reduce skewness. Multivariable regression was used to assess whether markers of inflammation were associated with Vo(2 max) after adjustment for age, body mass index, CHD risk factors, and lifestyle variables (physical activity level, percent body fat, and alcohol intake). Vo(2 max) was 34.5 ml.kg(-1).min(-1) (SD 6.1). Log IL-6 (r = -0.38, P < 0.001), log CRP (r = -0.40, P < 0.001), fibrinogen (r = -0.42, P < 0.001), and WBC count (r = -0.22, P = 0.004) were each correlated with Vo(2 max). In separate multivariable linear regression models that adjusted for age, body mass index, CHD risk factors, and lifestyle variables, log IL-6 [beta-coeff = -1.66 +/- 0.63 (SE), P = 0.010], log CRP [beta-coeff = -0.99 +/- 0.33 (SE), P = 0.003], fibrinogen [beta-coeff = -1.51 +/- 0.44 (SE), P = 0.001], and WBC count [beta-coeff = -0.52 +/- 0.30 (SE), P = 0.088] were each inversely associated with Vo(2 max). In conclusion, higher circulating levels of IL-6, CRP, and fibrinogen are independently associated with lower Vo(2 max) in asymptomatic men.

Acute-Phase Proteins↗
PubMed1999

Clinical research databases and clinical decision making in chronic diseases.

Chronic diseases are the major source of morbidity, mortality, and resource utilization. Large-scale longitudinal databases are rapidly proliferating in both single- and multi-institutional settings, providing clinical data on a broad range of patients who receive 'real world' management. Although bias and changing medical management may limit the types of questions that can be addressed using the data contained in longitudinal clinical databases, many initial hypotheses can be generated from the data. Because chronic diseases persist over long periods of time, understanding the impact of temporal relationships, and of concurrent clinical events and contexts is critical to meaningful interpretation of clinical data. Adapting techniques initially developed for the physical sciences and for statistical process control can produce visual displays of clinical data that capture complex temporal and contextual information. With these tools, investigators can quickly explore vast quantities of clinical data, and discover new temporal relationships and emerging trends.

Case-Control Studies↗
PubMedDate not supplied

Relationships between a clinical-visual scoring system and two histological techniques: a laboratory study on occlusal and approximal carious lesions.

One aim of the present laboratory study was to determine whether a visual scoring system (ERK) developed for occlusal caries could be applied to approximal lesions. A new histological technique (autofluorescence, AF) recognises dentine that is soft and would be removed with an excavator during operative treatment. A second aim was to investigate the relationship between the visual scoring system (ERK) and AF of dentine both occlusally and approximally. The sample comprised 93 extracted teeth chosen to represent the range of visual scores on approximal and occlusal surfaces. After sectioning through the investigation site, the cut faces were examined in a stereomicroscope and the depth of demineralization was scored. Autofluorescence was viewed with a confocal laser scanning microscope. Results showed reasonable correlation between the visual scores and the stereomicroscope histological evaluations for occlusal surfaces and non-cavitated approximal surfaces. However, cavitated approximal surface lesions were less advanced histologically than cavitated occlusal carious lesions. The AF technique indicated that several lesions with intact surfaces would have had soft, excavatable dentine, whereas several with microcavities would not.

Dental Caries↗