Changes in serum fast and slow skeletal troponin I concentration following maximal eccentric contractions.

OBJECTIVES: We tested the hypothesis that fast skeletal muscle troponin I (fsTnI) concentration in serum would increase more than those of slow skeletal muscle troponin I (ssTnI) after eccentric exercise of the elbow flexors using a sensitive blood marker to track fibre specific muscle damage. DESIGN: Observational comparison of response in a single experimental group. METHODS: Eight young men (26.4±6.2 years) performed 210 (35 sets of 6) eccentric contractions of the elbow flexors on an isokinetic dynamometer with one arm. Changes in serum fsTnI and ssTnI concentrations, serum creatine kinase (CK) activity, and maximal voluntary isometric contraction torque (MVIC) before and 1, 2, 3, 4 and 14 days following exercise were analysed by a Student-Newman-Keuls multiple comparison test. The relationship between serum CK activity and fsTnI or ssTnI concentrations was determined using a Pearson's product moment correlation. RESULTS: Significant (P<0.05) decreases in MVIC and increases in serum CK activity and fsTnI were evident after exercise, but ssTnI did not change. The time course of changes in fsTnI was similar to that of CK, peaking at 4 days post-exercise, and the two were highly correlated (r=0.8). CONCLUSIONS: Increases in serum fsTnI concentrations reflect muscle damage, and it seems likely that only fast twitch fibres were damaged by eccentric contractions.

Warm-up affects diurnal variation in power output.

The purpose of this study was to examine whether time of day variations in power output can be accounted for by the diurnal fluctuations existent in body temperature. 8 recreationally trained males (29.8±5.2 yrs; 178.3±5.2 cm; 80.3±6.5 kg) were assessed on 4 occasions following a: (a) control warm-up at 8.00 am; (b) control warm-up at 4.00 pm; (c) extended warm-up at 8.00 am; and, (d) extended warm-up at 4.00 pm. The control warm-up consisted of dynamic exercises and practice jumps. The extended warm-up incorporated a 20 min general warm-up on a stationary bike prior to completion of the control warm-up, resulting in a whole body temperature increase of 0.3±0.2°C. Kinetic and kinematic variables were measured using a linear optical encoder attached to a barbell during 6 loaded counter-movement jumps. Results were 2-6% higher in the afternoon control condition than morning control condition. No substantial performance differences were observed between the extended morning condition and afternoon control condition where body temperatures were similar. Results indicate that diurnal variation in whole body temperature may explain diurnal performance differences in explosive power output and associated variables. It is suggested that warm-up protocols designed to increase body temperature are beneficial in reducing diurnal differences in jump performance.

Effects of experience in a dynamic environment on postural control.

BACKGROUND: Surfing is a balance-reliant, open skill performed in a dynamic environment rich in visual, somatosensory and vestibular information. OBJECTIVE: To evaluate adaptations to the postural control system by surfing experience. METHODS: Postural control was assessed in an upright bipedal stance in 60 male volunteers (21 elite surfers, 20 intermediate level surfers, and 19 controls) using various closed-stance positions. Six tasks were performed with two trials including a cognitive task, in the following order: eyes open, head in a neutral position (EO1); eyes closed, head in a neutral position (EC); eyes closed, head back (ECHB); eyes open, head in a neutral position, cognitive task 1 (EOC1); eyes open head in a neutral position, cognitive task 2 (EOC2); eyes open head in a neutral position (EO2). Dependent variables were area of 95th centile ellipse (AoE) and sway path length (SPL). RESULTS: All participants showed systematic increases in SPL and AoE in EC and ECHB trials. Expert surfers displayed significantly (p<0.05) increased SPL but not AoE when sharing attention with both concurrent mental tasks compared with controls. Controls showed a slight, non-significant change in postural control (reduced SPL and AoE) when attending to concurrent mental tasks. CONCLUSIONS: The findings indicate that standard postural sway indices are not able to elucidate whether expertise in surfing facilitates adaptations to the postural control system. However, concurrent mental task findings illustrate that systematic differences in balance abilities between expert surfers and controls may exist.

Work and peak torque during eccentric exercise do not predict changes in markers of muscle damage.

OBJECTIVES: Large inter-subject variability in responses to eccentric exercise has been reported. This study investigated the hypothesis that the variability of changes in indirect markers of exercise-induced muscle damage (EIMD) would be explained by work performed and/or torque generated during eccentric exercise. METHODS: Subjects (n = 53) performed 60 maximal eccentric actions of the elbow flexors on an isokinetic dynamometer that forcibly extended the elbow joint from 60 degrees to 180 degrees at a constant velocity (90 degrees s(-1)). Markers of EIMD included maximal voluntary isometric contraction torque at 90 degrees elbow flexion (MVC), range of motion, plasma creatine kinase activity and muscle soreness. Measurements were taken 2 days before, immediately after and 1-4 days post-exercise. Pearson's correlation coefficient was used to examine relationships between exercise parameters (total work, change in total work, torque produced during exercise, change in peak torque) and markers of EIMD. RESULTS: Large inter-subject variability was evident for both work and torque during exercise, and changes in all markers of EIMD. Contrary to the hypothesis, total work (normalised for individual pre-exercise MVC) did not correlate significantly with any markers of EIMD, with the exception of MVC (r = 0.3). Total work performed and changes in total work showed higher correlations with some markers, but no r-values exceeded 0.4. Normalised exercise torque and the changes in peak torque during exercise were not correlated with changes in MVC, or other markers. CONCLUSION: These results suggest the large inter-subject variability in responses to eccentric exercise is not associated with work performed or torque generated during eccentric exercise.

The cumulative risks of prolapsing mitral valve. 40 years of follow-up.

Prolapsing mitral valve is a common cardiac condition, occurring in approximately 16 million people in the United States alone. Primary prolapsing mitral valve may be familial or nonfamilial and may be associated with myxomatous degeneration of the mitral valve leaflets, such as occurs in Marfan syndrome and other connective tissue disorders. Secondary forms may be associated with such entities as rheumatic fever (especially after commissurotomy) and coronary artery disease (in the presence of ruptured chordae tendineae), and with such congenital conditions as interatrial defect and primary cardiomyopathy with outflow tract obstruction. Prolapsing mitral valve is characterized by late systolic murmur, mid-systolic click, or both. Arrhythmias occur in the form of benign premature atrial contraction, premature nodal contraction, and paroxysmal atrial tachycardia. As the patient ages, atrial flutter and atrial fibrillation tend to develop. In some chronic cases, especially those involving atrial fibrillation, systemic emboli may occur. Rare premature ventricular contractions may be largely benign, whereas more frequent premature ventricular contractions may lead to severe arrhythmic complexes such as ventricular tachycardia or ventricular fibrillation. With advancing age, atrioventricular conduction defects of varying degrees or sick sinus syndrome may necessitate a pacemaker installation. About one quarter of prolapsing mitral valve cases progress, with increasing mitral insufficiency and increasing enlargement of the left atrium and left ventricle, which at times leads to congestive heart failure. Coronary artery disease may occur with the severity commensurate with the patient's age group. About three quarters of patients with prolapsing mitral valve syndrome lead normal lives.

College choice among prospective health professions majors: implications for nursing education.

Factors associated with high school students' decisions to pursue health-related fields of study were investigated using the "Survey of Future Plans of High School Seniors." Data from 10,878 seniors were analyzed using regression and discriminant analysis. Results indicated that: The applicant pool for health professions overlapped most with the applicant pool for education, but education majors were characterized by lower academic aptitude; the specific characteristics of a college were less important to those entering health professions than to those entering other majors; and, health profession applicants with higher academic aptitude purport life goals more consistent with professional advancement than do lower aptitude applicants.

Acute myocardial infarction. Decision making in the first critical hours.

Decisions about early management of acute myocardial infarction require great care and astuteness, since the threat of sudden death is the greatest during the first few hours after onset of infarction. General measures of acute care include relief of pain and management of arrhythmia. Drug therapy with beta-adrenergic blocking agents or vasodilators may also be indicated. Other measures that may be considered (some of which are controversial) include hemodynamic monitoring, mechanical circulatory assistance, ambulatory electrocardiographic monitoring, exercise testing, modification of risk factors, and coronary angiography. Intracoronary administration of streptokinase, which is still investigational, has shown marked preservation of myocardial tissue in some cases.

Clinical results of coronary bypass in 500 patients at least 10 years after operation.

We determined the outcome of coronary artery bypass surgery in 500 consecutive patients followed for at least 10 years after operation. There were 446 males (89.2%). Angina pectoris was the major indication for operation. Four hundred six patients (81%) had multivessel coronary artery disease and 348 (69.9%) had good left ventricular function. At 10 years of follow-up, 48% of patients were asymptomatic and 41% were improved. Propranolol was being used by 36% of patients and nitrates by 49%. Of the 355 patients younger than 65 years of age at the time of follow-up, 57% were employed full time and 24% were working part-time. Reoperation was performed in 9% of patients. Analysis of survival by Kaplan-Meier curves indicated that overall 10-year survival rates were 78% for one-vessel disease, 69% for two-vessel disease, 48% for three-vessel disease and 67% for left main coronary artery disease. For patients with good left ventricular function, the 10-year survival rates were 83% for one-vessel disease, 73% for two-vessel disease, 53% for three-vessel disease and 73% for left main disease. For patients with poor left ventricular function, the rates were 56%, 59%, 40% and 54%, respectively. Cox multivariate analysis indicated that preoperative diuretic use, history of heart failure, the number of diseased vessels, and infarct on the preoperative ECG were all good predictors of survival. This study shows that the outcome of coronary artery bypass surgery 10 years operation is highly favorable.

Patterns of patency of 596 vein grafts up to seven years after aorta-coronary bypass.

The long-term behavior of vein grafts and their effect on the native circulation were studied by examining 596 vein grafts in 343 patients at a mean follow-up of 15.4 months, range zero to 84 months. Serial studies were performed on 27 patients with 38 grafts. The over-all graft patency rate was 84 per cent, and the rate after more than 5 years was 89 per cent. The patency rate in asymptomatic patients was 91 per cent compared with 81 per cent in the remainder. The patency of grafts attached distal to total occlusions was 82 per cent (78/82). The angle of origin of the grafts from the aorta did not appear to influence patency or the severity of intimal proliferative changes. In 76 patients with 126 grafts, pre- and postoperative cineangiograms were compared, and changes in the graft and underlying coronary artery classified as Groups 1 to to 6: Group 1, patent graft, bidirectional flow in the grafted vessel, proximal lesion unchanged; Group 2, patent graft, bidirectional flow, proximal lesion progressed to occlusion locally; Group 3; patent graft, distal flow only, occlusion of lesion and segment between graft and lesion; Group 4, graft occluded, native artery unaltered; Group 5, graft occluded, native artery now occluded at lesion and region of anastomosis; Group 6, new distal lesion. Results were as follows; Group 1, 58 per cent; Group 2, 21.2 per cent; Group 3, 5 per cent, Group 4, 12.5 per cent; Group 5, 2.5 per cent; and Group 6, 0.8 per cent. Native coronary arteries undergoing closure (Group 2) had lesions 95 per cent or greater in 93 per cent of patients. The rate of closure of ungrafted lesions was 2 per cent. We believe these results encourage the continued used of vein bypass grafts.