A maximal multistage 20 m shuttle run test was designed to determine the maximal aerobic power of schoolchildren, healthy adults attending fitness class and athletes performing in sports with frequent stops and starts (e.g. basketball, fencing and so on). Subjects run back and forth on a 20 m course and must touch the 20 m line; at the same time a sound signal is emitted from a prerecorded tape. Frequency of the sound signals is increased 0.5 km h-1 each minute from a starting speed of 8.5 km h-1. When the subject can no longer follow the pace, the last stage number announced is used to predict maximal oxygen uptake (VO2max) (Y, ml kg-1 min-1) from the speed (X, km h-1) corresponding to that stage (speed = 8 + 0.5 stage no.) and age (A, year): Y = 31.025 + 3.238 X - 3.248A + 0.1536AX, r = 0.71 with 188 boys and girls aged 8-19 years. To obtain this regression, the test was performed individually. Right upon termination VO2 was measured with four 20 s samples and VO2max was estimated by retroextrapolating the O2 recovery curve at time zero of recovery. For adults, similar measurements indicated that the same equation could be used keeping age constant at 18 (r = 0.90, n = 77 men and women 18-50 years old). Test-retest reliability coefficients were 0.89 for children (139 boys and girls 6-16 years old) and 0.95 for adults (81 men and women, 20-45 years old).(ABSTRACT TRUNCATED AT 250 WORDS)

In patients with atrial fibrillation and congestive heart failure, a routine strategy of rhythm control does not reduce the rate of death from cardiovascular causes, as compared with a rate-control strategy. (ClinicalTrials.gov number, NCT00597077.)

In order to validate a maximal multistage 20-m shuttle run test for the prediction of VO2 max, 91 adults (32 females and 59 males, aged 27.3 +/- 9.2 and 24.8 +/- 5.5 year respectively and with mean VO2 max (+/- SD) of 39.3 +/- 8.3 and 51.6 +/- 7.8 ml . kg-1 . min-1 respectively) performed the test and had VO2 max estimated by the retroextrapolation method (extrapolation to time zero of recovery of the exponential least squares regression of the first four 20-s recovery VO2 values). Starting at 8 km . h-1 and increasing by 0.5 km . h-1 every 2 min, the 20-m shuttle run test enabled prediction of the VO2 max (y, ml . kg-1 . min-1) from the maximal speed (x, km . h-1) by means of the following regression equation: y = 5.857x - 19.458; r = 0.84 and SEE = 5.4. Later, the multistage protocol was slightly modified to its final version, in which the test started at stage 7 Met and continued with a 1 Met (3.5 ml O2 . kg-1 . min-1) increment every 2 min. Twenty-five of the 91 subjects performed the 20-m shuttle test twice, once on a hard, low-friction surface (vinyl-asbestos tiles) and another time on a rubber floor, as well as a walking maximal multistage test on an inclined treadmill. There was no difference between the means of these tests or between the slopes of the VO2max - maximal speed regressions for the two types of surfaces. The 20-m shuttle run test and another maximal multistage field test involving continuous track running gave comparable results (r = 0.92, SEE = 2.6 ml O2 . kg-1 . min-1, n = 70). Finally, test and retest of the 20-m shuttle run test also yielded comparable results (r = 0.975, SEE = 2.0 ml O2 . kg-1 . min-1, n = 50). It is concluded that the 20-m shuttle run test is valid and reliable test for the prediction of the VO2 max of male and female adults, individually or in groups, on most gymnasium surfaces.

Background-Radiofrequency (RF) catheter ablation is limited by thromboembolic complications. The objective of this study was to compare the incidence and characteristics of thrombi complicating RF and cryoenergy ablation, a novel technology for the catheter-based treatment of arrhythmias. Methods and Results-Ablation lesions (nϭ197) were performed in 22 mongrel dogs at right atrial, right ventricular, and left ventricular sites preselected by a randomized factorial design devised to compare RF ablation with cryocatheter configurations of varying sizes (7F and 9F), cooling rates (Ϫ1°C/s, Ϫ5°C/s, and Ϫ20°C/s) and target temperatures (Ϫ55°C and Ϫ75°C). Animals were pretreated with acetylsalicylic acid and received intraprocedural intravenous unfractionated heparin. Seven days after ablation, the incidence of thrombus formation was significantly higher with RF than with cryoablation (75.8% versus 30.1%, Pϭ0.0005). In a multiple regression model, RF energy remained an independent predictor of thrombus formation compared with cryoenergy (OR, 5.6; 95% CI, 1.7, 18.1; Pϭ0.0042).Thrombus volume was also significantly greater with RF than with cryoablation (median, 2.8 versus 0.0 mm 3 ; PϽ0.0001). More voluminous thrombi were associated with larger RF lesions, but cryolesion dimensions were not predictive of thrombus size. Conclusions-RF energy is significantly more thrombogenic than cryoenergy, with a higher incidence of thrombus formation and larger thrombus volumes. The extent of hyperthermic tissue injury is positively correlated with thrombus bulk, whereas cryoenergy lesion size does not predict thrombus volume, most likely reflecting intact tissue ultrastructure with endothelial cell preservation.

The antioxidant probucol is effective in reducing the rate of restenosis after balloon coronary angioplasty.

Changes in muscle strength, vastus lateralis fibre characteristics and myosin heavy‐chain (MyoHC) gene expression were examined in 48 men and women following 3 weeks of knee immobilization and after 12 weeks of retraining with 1866 eccentric, concentric or mixed contractions. Immobilization reduced eccentric, concentric and isometric strength by 47 %. After 2 weeks of spontaneous recovery there still was an average strength deficit of 11 %. With eccentric and mixed compared with concentric retraining the rate of strength recovery was faster and the eccentric and isometric strength gains greater. Immobilization reduced type I, IIa and IIx muscle fibre areas by 13, 10 and 10 %, respectively and after 2 weeks of spontaneous recovery from immobilization these fibres were 5 % smaller than at baseline. Hypertrophy of type I, IIa and IIx fibres relative to baseline was 10, 16 and 16 % after eccentric and 11, 9 and 10 % after mixed training (all P < 0.05), exceeding the 4, 5 and 5 % gains after concentric training. Type IIa and IIx fibre enlargements were greatest after eccentric training. Total RNA/wet muscle weight and type I, IIa and IIx MyoHC mRNA levels did not change differently after immobilization and retraining. Immobilization downregulated the expression of type I MyoHC mRNA to 0.72‐fold of baseline and exercise training upregulated it to 0.95 of baseline. No changes occurred in type IIa MyoHC mRNA. Immobilization and exercise training upregulated type IIx MyoHC mRNA 2.9‐fold and 1.2‐fold, respectively. For the immobilization segment, type I, IIa and IIx fibre area and type I, IIa and IIx MyoHC mRNA correlated (r= 0.66, r= 0.07 and r=−0.71, respectively). The present data underscore the role muscle lengthening plays in human neuromuscular function and adaptation.

Background-Studies

Amiodarone is more effective than sotalol or propafenone for the prevention of recurrences of atrial fibrillation.