Self-efficacy and the maintenance of exercise participation in older adults

The role played by exercise self-efficacy in the maintenance of exercise participation of previously sedentary middle-aged adults 4 months after the termination of a formal exercise program is reported. Correlational and multiple regression analyses examined the influence of self-efficacy, physiological (aerobic capacity, sex, body composition), and behavioral (past exercise frequency and intensity) parameters in the maintenance of exercise participation. Self-efficacy significantly predicted exercise behavior at follow-up when controlling for biological and behavioral influences. Aerobic capacity, exercise efficacy, and exercise behavior in combination were significantly related to current energy expenditure in aerobic physical activity. The discussion focuses on the need to examine the impact of different correlates of exercise behavior at different stages of the exercise process.This project was funded by Grant AG07907 from the National Institute on Aging.     

Rate-responsive pacing with a pacemaker that detects respiratory rate (Biorate): clinical advantages and complications

The respiratory-dependent pacemaker (RDP3 or MB-1, Biorate, Biotec International, S.p.A., Bologna, Italy) detects the respiratory rate by measuring thoracic impedance using a subcutaneous auxiliary lead. The sensed respiratory rate is used to determine the pacing rate response. This pacemaker had been implanted in 9 patients with a mean age of 58 (range 42-69) years. During symptom-limited treadmill exercise, rate-modulated pacing resulted in a significant increase in pacing rate (mean +/- SD, 124 +/- 10 vs. 71 +/- 3 beats/min p less than 0.001) and exercise capacity (343 +/- 147 vs. 463 +/- 120 s, p less than 0.05) compared to those achieved with constant rate ventricular pacing. Brief treadmill exercise tests showed appropriate rate response to increased walking speed and gradient. However, rate response was modified by arm swinging-induced motion artefact which affected the measured "impedance." Complications observed on follow-up included perforation of the auxiliary lead in 2 patients and symptomatic myopotential interference in 3 patients with the RDP3 pacemaker, all of whom required unit replacement. It is concluded that although the respiratory-dependent pacemaker can confer physiological benefit in patients with bradycardia, myopotential interference (largely overcome by the new version MB-1 with programmable sensitivity) and the auxiliary lead can be problematic in some patients.     

基于贝叶斯多变量联合模型的体检人群脑卒中发病风险因素的纵向研究

背景 脑卒中是目前影响人类健康的主要公共卫生问题之一;健康体检纵向数据累积了大量的健康信息,由于缺失数据多、样本量小等诸多问题,导致其利用率低、重要信息未能得到充分挖掘,进而对常见慢性病的有效防控等工作带来一定困难。目的 基于贝叶斯多变量联合模型,探讨体检人群脑卒中发病风险因素,为慢性病风险因素分析提供新的方法。方法 本研究使用空军军医大学西京医院健康医学中心2008—2015年的体检资料。随访情况：以首次发生脑卒中为结局事件,发生结局事件立即停止随访;若未发生,到2015年体检信息收集完成后结束随访;体检间隔时间为1年。依据随访过程中是否发生脑卒中分为脑卒中组和非脑卒中组。纵向观察变量包括总胆固醇（TC）、三酰甘油（TG）、低密度脂蛋白胆固醇（LDL-C）、高密度脂蛋白胆固醇（HDL-C）、体质指数（BMI）和收缩压（SBP）。采用多因素Cox回归模型分析基线情况对脑卒中结局事件的影响;采用贝叶斯多变量联合模型,分析随访过程中TC、TG、LDL-C、HDL-C、BMI和SBP的纵向变化轨迹对脑卒中发病的影响。结果 本研究共纳入234例研究对象,1 581条纵向随访记录,平均随访时间为...     

肠鸣音的建模与模拟研究

本文对肠道运动进行分析，从结构上研究肠鸣音的产生机理和肠鸣音的时域、频域特点，从而得到其物理模型，并用等效电路来模拟肠鸣音的产生，为研究肠鸣音的数学模型，以及临床医学研究提供了方便。     

Role of nitric oxide in skeletal muscle: synthesis,distribution and functional importance

Over the last two decades, nitric oxide (NO) has been established as a novel mediator of biological processes, ranging from vascular control to long-term memory, from tissue inflammation to penile erection. This paper reviews recent research which shows that NO and its derivatives also are synthesized within skeletal muscle and that NO derivatives influence various aspects of muscle function. Individual muscle fibres express one or both of the constitutive NO synthase (NOS) isoforms. Type I (neuronal) NOS is localized to the sarcolemma of fast fibres; type III (endothelial) NOS is associated with mitochondria. Isolated skeletal muscle produces NO at low rates under resting conditions and at higher rates during repetitive contraction. NO appears to mediate cell–cell interactions in muscle, including vasodilation and inhibition of leucocyte adhesion. NO also acts directly on muscle fibres to alter cell function. Muscle metabolism appears to be NO-sensitive at several sites, including glucose uptake, glycolysis, mitochondrial oxygen consumption and creatine kinase activity. NO also modulates muscle contraction, inhibiting force output by altering excitation–contraction coupling. The mechanisms of NO action are likely to include direct effects on redox-sensitive regulatory proteins, interaction with endogenous reactive oxygen species, and activation of second messengers such as cyclic guanosine monophosphate (cGMP). In conclusion, research published over the past few years makes it clear that skeletal muscle produces NO and that endogenous NO modulates muscle function. Much remains to be learned, however, about the physiological importance of NO actions and about their underlying mechanisms.     

Physical loading and performance as predictors of back pain in healthy adults A 5-year prospective study

We investigated muscle strength, aerobic power, and occupational and leisure-time physical loading as predictors of back pain in a 5-year follow-up study. A cohort of 456 adults aged 25, 35, 45 and 55 years, free of back pain, participated in measurements of anthropometric characteristics, aerobic power and muscle strength characteristics at baseline. The subjects' levels and types of physical activity and occupational physical loading were also determined. At 5 years after the baseline examinations 356 of these subjects (78.1 %) were reached by mail, and 262 of them (73.6%) properly completed and returned a questionnaire including a detailed back pain history for the 5 years following the baseline measurements. Of this number 56 subjects (21 %) who reported back pain ( > 30 on a scale from 0 to 100) and functional impairment during the 5-year follow-up composed the marked back pain group. Other subjects (n = 71, 27%) noting lesser symptoms were included in the mild back pain group; 135 subjects (52%) reported having had no back pain. The subjects with marked back pain were on average taller than the subjects without back pain, while no such difference was found in body mass. Heavy occupational musculoskeletal loading (P = 0.005) and high general occupational physical demands (P = 0.036) predicted future back pain. Leisuretime physical activity, aerobic power or muscle strength characteristics were not predictive of future back pain.     

Low plasma glutamine in combination with high glutamate levels indicate risk for loss of body cell mass in healthy individuals: the effect of N-acetyl-cysteine

Skeletal muscle catabolism, low plasma glutamine, and high venous glutamate levels are common among patients with cancer or human immunodeficiency virus infection. In addition, a high glycolytic activity is commonly found in muscle tissue of cachectic cancer patients, suggesting insufficient mitochondrial energy metabolism. We therefore investigated (a) whether an anaerobic physical exercise program causes similar changes in plasma amino acid levels, and (b) whether low plasma glutamine or high glutamate levels are risk factors for loss of body cell mass (BCM) in healthy human subjects, i.e., in the absence of a tumor or virus infection. Longitudinal measurements from healthy subjects over longer periods suggest that the age-related loss of BCM occur mainly during episodes with high venous glutamate levels, indicative of decreased muscular transport activity for glutamate. A significant increase in venous glutamate levels from 25 to about 40 M was seen after a program of anaerobic physical exercise. This was associated with changes in T lymphocyte numbers. Under these conditions persons with low baseline levels of plasma glutamine, arginine, and cystine levels also showed a loss of BCM. This loss of BCM was correlated not only with the amino acid levels at baseline examination, but also with an increase in plasma glutamine, arginine, and cystine levels during the observation period, suggesting that a loss of BCM in healthy individuals terminates itself by adjusting these amino acids to higher levels that stabilize BCM. To test a possible regulatory role of cysteine in this context we determined the effect of N-acetyl-cysteine on BCM in a group of subjects with relatively low glutamine levels. The placebo group of this study showed a loss of BCM and an increase in body fat, suggesting that body protein had been converted into other forms of chemical energy. The decrease in mean BCM/body fat ratios was prevented by N-acetyl-cysteine, indicating that cysteine indeed plays a regulatory role in the physiological control of BCM.Abbreviations BCM Body cell mass - HIV Human immunodeficiency virus type 1 - NAC N-Acetyl-cysteine     

Effect of different types of high carbohydrate diets on glycogen metabolism in liver and skeletal muscle of endurance-trained rats

Male Wistar rats were fed ad libitum four different diets containing fructose, sucrose, maltodextrins or starch as the source of carbohydrate (CH). One group was subjected to moderate physical training on a motor-driven treadmill for 10 weeks (trained rats). A second group received no training and acted as a control (sedentary rats). Glycogen metabolism was studied in the liver and skeletal muscle of these animals. In the sedentary rats, liver glycogen concentrations increased by 60%–90% with the administration of simple CH diets compared with complex CH diets, whereas skeletal muscle glycogen stores were not significantly affected by the diet. Physical training induced a marked decrease in the glycogen content in liver (20%–30% of the sedentary rats) and skeletal muscle (50%–80% of the sedentary rats) in animals fed simple (but not complex) CH diets. In liver this was accompanied by a two-fold increase of triacylglycerol concentrations. Compared with simple CH diets, complex CH feeding increased by 50%–150% glycogen synthase (GS) activity in liver, whereas only a slight increase in GS activity was observed in skeletal muscle. In all the animal groups, a direct relationship existed between tissue glucose 6-phosphate concentration and glycogen content (r = 0.9911 in liver, r = 0.7177 in skeletal muscle). In contrast, no relationship was evident between glycogen concentrations and either glycogen phosphorylase activity or adenosine 5-monophosphate tissue concentration. The results from this study thus suggest that for trained rats diets containing complex CH (compared with diets containing simple CH) improve the glycogenic capacity of liver and skeletal muscle, thus enabling the adequate regeneration of glycogen stores in these two tissues.     

Effect of previous supramaximal work on lacticaemia during supra-anaerobic threshold exercise

Summary Twelve male and female subjects (eight trained, four untrained) exercised for 30 min on a treadmill at an intensity of maximal O₂ consumption (% O_2max) 90.0%, SD 4.7 greater than the anaerobic threshold of 4 mmol ·1^–1 (Th_an =83.6% O_2max, SD 8.9). Time-dependent changes in blood lactate concentration ([la_b]) during exercise occurred in two phases: the oxygen uptake ( O₂) transient phase (from 0 to 4 min) and the O₂ steady-state phase (4–30 min). During the transient phase, [la_b] increased markedly (l.30 mmol · l ^–1 · min ^–1, SD 0.13). During the steady-state phase, [la_b] increased slightly (0.02 mmol · 1^–1 · min^–1, SD 0.06) and when individual values were considered, it was seen that there were no time-dependent increases in [la_b] in half of the subjects. Following hyperlacticaemia (8.8 mmol -l^–1, SD 2.0) induced by a previous 2 min of supramaximal exercise (120% O_2max), [la_b] decreased during the O₂ transient (–0.118 mmol · 1^–1 · min^–1, SD 0.209) and steady-state (–0.088 mmol · 1^–1 · min ^–1, SD 0.103) phases of 30 min exercise (91.4% O_2max, SD 4.8). In conclusion, it was not possible from the Th_an to determine the maximal [la_b] steady state for each subject. In addition, lactate accumulated during previous supramaximal exercise was eliminated during the O₂ transient phase of exercise performed at an intensity above the Th_an. This effect is probably largely explained by the reduction in oxygen deficit during the transient phase. Under these conditions, the time-course of changes in [la_b] during the O₂ steady state was also affected.     

Potentiation and restitution of heart muscle contraction in rats adapted to exercise

The original amplitude of contraction of strips of myocardium determined the inotropic response to paired stimulation. The higher the initial amplitude, the lower the degree of potentiation and the higher the degree of restitution of contraction. For equal amplitude, the degree of potentiation of myocardial contraction of exercise-adapted rats was greater and the degree of restitution smaller than in the control. These changes probably reflect changes in the ion transport system of the myocardial cells.Presented by Academician of the Academy of Medical Sciences of the USSR A. M. Chernukh.Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 7, pp. 780–782, July, 1976.