Impaired force-frequency relations in patients with hypertensive left ventricular hypertrophy. A possible physiological marker of the transition from physiological to pathological hypertrophy.
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BACKGROUND: The extent to which force-frequency and relaxation-frequency relations (FFR and RFR, respectively) and exercise-induced adrenergic stimulation affect myocardial inotropic and lusitropic reserves has not been established in patients with left ventricular (LV) hypertrophy (LVH). METHODS AND RESULTS: We calculated the maximum first derivative of LV pressure (LV dP/dtmax) and the LV pressure half-time (T1/2) during pacing, exercise, and isoproterenol infusion in 17 patients with hypertensive LVH and 9 control subjects to investigate the influence of increases in heart rate (HR) and adrenergic stimulation on inotropic and lusitropic reserves. Group A consisted of 10 LVH patients who showed a progressive increase in the HR-LV dP/dtmax relation. Group B consisted of 7 LVH patients in whom the HR-dP/dtmax relation at physiological pacing rates was biphasic. The LV mass index was larger and the LV ejection fraction was smaller in group B than in group A (244+/-72 g/m2 versus 172+/-22 g/m2 and 55+/-18% versus 72+/-6%, respectively; both P<0.05). The increase in LV dP/dtmax was greater during exercise than pacing alone for similar increases in HR in all groups (P<0.05) (group A, 111+/-22% versus 25+/-14%; group B, 105+/-35% versus 14+/-10%; control, 111+/-24% versus 25+/-12%). T1/2 was shorter (P<0.05) during exercise than with pacing alone in all groups (group A, 41+/-6% versus 11+/-3%; group B, 38+/-9% versus 14+/-4%; control, 44+/-6% versus 12+/-5%). Isoproterenol infusion caused similar increases in LV dP/dtmax and similar decreases in T1/2 in all groups. CONCLUSIONS: The FFR was biphasic in patients with severe LVH irrespective of LV function but was preserved in patients with less severe LVH and control subjects. Importantly, the RFR and adrenergic control of both inotropic and lusitropic reserves were well preserved in all LVH patients. A biphasic FFR at physiological pacing rates may be one of the earliest markers of the transition from physiological adaptation to the pathological process in LVH patients. (+info)
Human skeletal muscle cytosols are refractory to cytochrome c-dependent activation of type-II caspases and lack APAF-1.
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Apoptotic regulatory mechanisms in skeletal muscle have not been revealed. This is despite indications that remnant apoptotic events are detected following exercise, muscle injury and the progression of dystrophinopathies. The recent elicitation of a cytochrome c-mediated induction of caspases has led to speculation regarding a cytochrome c mechanism in muscle. We demonstrate that cytosols from skeletal muscle biopsies from healthy human volunteers lack the ability to activate type-II caspases by a cytochrome c-mediated pathway despite the confirmed presence of both procaspase-3 and -9. This was not due to the presence of an endogenous inhibitor, as the muscle cytosols enhanced caspase activity when added to a control cytosol, subsequently activated by cytochrome c and dATP. In addition, we demonstrate that muscle cytosols lack the apoptosis protease activator protein-1 (APAF-1), both at the protein and mRNA levels. These data indicate that human skeletal muscle cells will be refractory to mitochondrial-mediated events leading to apoptosis and thus can escape a major pro-apoptotic regulatory mechanism. This may reflect an evolutionary adaptation of cell survival in the presence of the profusion of mitochondria required for energy generation in motility. (+info)
Hip moments during level walking, stair climbing, and exercise in individuals aged 55 years or older.
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BACKGROUND AND PURPOSE: Low bone mass of the proximal femur is a risk factor for hip fractures. Exercise has been shown to reduce bone loss in older individuals; however, the exercises most likely to influence bone mass of the proximal femur have not been identified. Net moments of force at the hip provide an indication of the mechanical load on the proximal femur. The purpose of this study was to examine various exercises to determine which exercises result in the greatest magnitude and rate of change in moments of force at the hip in older individuals. SUBJECTS AND METHODS: Walking and exercise patterns were analyzed for 30 subjects (17 men, 13 women) who were 55 years of age or older (X = 65.4, SD = 6.02, range = 55-75) and who had no identified musculoskeletal or neurological impairment. Kinematic and kinetic data were obtained with an optoelectronic system and a force platform. Results. Of the exercises investigated, only ascending stairs generated peak moments higher than those obtained during level walking and only in the transverse plane. Most of the exercises generated moments and rate of change in moments with magnitudes similar to or lower than those obtained during gait. CONCLUSION AND DISCUSSION: Level walking and exercises that generated moments with magnitudes comparable to or higher than those obtained during gait could be combined in an exercise program designed to maintain or increase bone mass at the hip. (+info)
Favorable life-style modification and attenuation of cardiovascular risk factors.
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In order to develop an effective counseling system for prevention of cardiovascular diseases, the association of a favorably changed life-style with improved risk factors was examined. Participants were 7,321 office workers aged 30-69 years from in and around Nagoya city. The age-adjusted odds ratio (OR) and its 95% confidence interval (CI) were calculated to assess the likelihood of risk factor improvement by favorable life-style modifications during a 3-year period. Those who began to eat breakfast and increased their vegetable intake normalized their previously abnormal diastolic blood pressure with more than twice the likelihood (adjusted OR [95% CI] 2.89 [1.29-6.46] and 2.60 [1.18-5.75], respectively). 'Began to eat breakfast' was also significantly associated with normalized total cholesterol (TC) (1.84, [1.05-3.21]). 'Stopped eating till full' significantly normalized the body mass index (2.03; [1.25-3.28]), uric acid (1.65; [1.07-2.52]) and TC (1.43; [1.04-1.97]). Those who started regular exercise significantly normalized their high-density lipoprotein-cholesterol (HDL-C) abnormality with 1.69-times the likelihood (1.69; [1.24-2.29]) and those who began to walk briskly also improved their TC abnormality (1.85; [1.19-2.89]). HDL-C was normalized with 2.55-times the likelihood in those who quit smoking (2.55; [1.68-3.86]). Because favorable life-style modifications can attenuate abnormal cardiovascular risk factors, then proper advice on specific risk factors should be routinely given at each health check-up in order to prevent the onset of cardiovascular diseases in subsequent years. (+info)
A chest wall restrictor to study effects on pulmonary function and exercise. 1. Development and validation.
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Chest wall-restrictive loading reduces a person's ability to expand the chest wall during inhalation and results in decrements in lung capacities, resting pulmonary function, and ultimately, exercise performance. Chest wall restriction is observed in some forms of skeletal and pulmonary diseases (e.g., scoliosis) as well as in occupational situations (e.g., bulletproof vests). We have designed a constant-pressure chest wall-restrictive device that provides a quantifiable and reproducible load on the chest. This paper describes the device and the initial pulmonary function tests conducted. Ten subjects participated in this study. Subjects wore the restrictive device while performing pulmonary function tests at four externally added restrictive loads on three separate occasions. A two-way repeated-measures multivariate analysis of variance revealed significant decreases in forced expiratory vital capacity (FVC) and forced expiratory volume in 1 s (FEV1.0) at each load while the ratio of FEV1.0 to FVC (FEV1.0%) was maintained. No significant differences in any variable were found across time or between the seated and standing position. These results indicate that this chest wall-restrictive device provides a quantifiable added inspiratory load in the breathing cycle that results in reproducible decrements in pulmonary function representative of those seen in some restrictive pulmonary disease and occupational situations. (+info)
A chest wall restrictor to study effects on pulmonary function and exercise. 2. The energetics of restrictive breathing.
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Chest wall restriction, whether caused by disease or mechanical constraints such as protective outerwear, can cause decrements in pulmonary function and exercise capacity. However, the study of the oxygen cost associated with mechanical chest restriction has so far been purely qualitative. The previous paper in this series described a device to impose external chest wall restriction, its effects on forced spirometric volumes, and its test-retest reliability. The purpose of this experiment was to measure the oxygen cost associated with varied levels of external chest wall restriction. Oxygen uptake and electromyogram (EMG) of the external intercostals were recorded during chest restriction in 10 healthy males. Subjects rested for 9 min before undergoing volitional isocapnic hyperpnea for 6 min. Subjects breathed at minute ventilations (V.I) of 30, 60, and 90 liters/min with chest wall loads of 0, 25, 50 and 75 mm Hg applied. Frequency of breathing was set at 15, 30, and 45 breaths per minute with a constant tidal volume (VT) of 2 liters. Oxygen uptake was measured continuously at rest and throughout the hyperventilation bouts, while controlling V.I and VT. Integrated EMG (IEMG) from the 3rd intercostal space was recorded during each minute of rest and hyperventilation. Two-way ANOVA with repeated measures revealed that chest wall loading and hyperpnea significantly increased V.O2 values (p < 0.01). External intercostal IEMG levels were significantly increased (p < 0.05) at higher restrictive load (50 and 75 mm Hg) and at the highest minute ventilation (90 liters/min). These data suggest that there is a significant and quantifiable increase in the oxygen cost associated with external chest wall restriction which is directly related to the level of chest wall restriction. (+info)
Management of obesity in low-income African Americans.
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The Bariatrics Clinic at Howard University Hospital was initiated to help low-income African-American adults with low literacy skills in obesity control. Fourteen African-American women and two men participated in the study. Essential components of the treatment included nutrition education, exercise, and behavior modification related to food intake. The nutrition education component involved teaching nutritional needs, taking into account low literacy skills, low economic status, and individual food preferences. A realistic diet plan was based on individual needs, economic status, availability of food, likes and dislikes, lifestyle, and family dynamics. On average, patients lost 2 lb a week on this program. On average, a 14-lb weight loss occurred in seven weeks. There has been a 10% dropout from this program as opposed to drop out rates of 40% to 50% with other treatments. The main reasons for the success of this program is that it is individualized and is sensitive to food preferences. (+info)
Reduction of exercise-induced asthma in children by short, repeated warm ups.
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AIM: To study the effect of a warm up schedule on exercise-induced asthma in asthmatic children to enable them to engage in asthmogenic activities. METHOD: In the first study, peak flows during and after three short, repeated warm up schedules (SRWU 1, 2, and 3), identical in form but differing in intensity, were compared in 16 asthmatic children. In the second study the efficiency of the best of these SRWU schedules was tested on 30 young asthmatic children. Children performed on different days a 7 minute run alone (EX1) or the same run after an SRWU (EX2). RESULTS: The second study showed that for most children (24/30) the fall in peak flow after EX2 was less than that after EX1. The percentage fall in peak flow after EX2 was significantly correlated with the percentage change in peak flow induced by SRWU2 (r = 0.68). The children were divided into three subgroups according to the change in peak flow after SRWU2: (G1: increase in peak flow; G2: < 15% fall in peak flow; G3: > 15% fall in peak flow). Only the children in the G3 subgroup did not show any gain in peak flow after EX2 compared with EX1. CONCLUSION: The alteration in peak flow at the end of the SRWU period was a good predictor of the occurrence of bronchoconstriction after EX2. An SRWU reduced the decrease in peak flow for most of the children (24/30) in this series, thus reducing subsequent post-exercise deep bronchoconstriction. (+info)