Bioenergetics and biomechanics of front crawl swimming.

"Underwater torque" (T') is one of the main factors determining the energy cost of front crawl swimming per unit distance (Cs). In turn, T' is defined as the product of the force with which the swimmer's feet tend to sink times the distance between the feet and the center of volume of the lungs. The dependency of Cs on T' was further investigated by determining Cs in a group of 10 recreational swimmers (G1: 4 women and 6 men) and in a group of 8 male elite swimmers (G2) after T' was experimentally modified. This was achieved by securing around the swimmers' waist a plastic tube filled, on different occasions, with air, water, or 1 or 2 kg of lead. Thus, T' was either decreased, unchanged, or increased compared with the natural condition (tube filled with water). Cs was determined, for each T' configuration, at 0.7 m/s for G1 and at 1.0 and 1.2 m/s for G2. For T' equal to the natural value, Cs (in kJ.m-1.m body surface area-2) was 0.36 +/- 0.09 and 0.53 +/- 0.13 for G1 in women and men, respectively, and 0.45 +/- 0.05 and 0.53 +/- 0.06 for G2 at 1.0 and 1.2 m/s, respectively. In a given subject at a given speed, Cs and T' were linearly correlated. To compare different subjects and different speeds, the single values of Cs and T' were normalized by dividing them by the corresponding individual averages. These were calculated from all single values (of Cs or T') obtained from that subject at that speed.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic findings in myocarditis.

This study analyzes morphologic and functional alterations detected by M-mode and 2-dimensional echocardiography in 41 patients with histologically proven myocarditis and different clinical presentations: congestive heart failure (63%), atrioventricular block (17%), chest pain (15%) and supraventricular arrhythmias (5%). Left ventricular dysfunction was common (69%), particularly in patients with congestive heart failure (88%), often without or with minor cavity dilatation. Patients with atrioventricular block or chest pain had usually preserved ventricular function. Right ventricular dysfunction was present in 23%. Additional findings included asynergic ventricular areas (64%), left ventricular "hypertrophy" sometimes reversible (20%), hyperrefractile myocardial areas (23%), ventricular thrombi (15%) and "restrictive" ventricular filling (7%). It is concluded that echocardiographic features of myocarditis are polymorphous and nonspecific. The echocardiographic pattern can simulate alternatively dilated, hypertrophic, restrictive or "right" ventricular cardiomyopathy, as well as coronary artery disease. In an appropriate clinical context, echocardiography can be helpful in the diagnosis of myocarditis and in the selection of patients for endomyocardial biopsy.