Skeletal muscle characteristics of sprint cyclists and nonathletes

Muscle fiber distribution and muscle enzyme activity (m. vastus lat.) were investigated in 10 elite sprint cyclists and 12 nonathletes. The ratio of fast to slow muscle fibers was 2:3 in cyclists and 3:2 in nonathletes. The mean diameter of each muscle fiber type was significantly higher in the athletes. The mean enzyme activity values in mu kat X g-1 w.w. for cyclists and nonathletes, respectively, were as follows: triosephosphate dehydrogenase (TPDH), 6.2 and 3.78; lactate dehydrogenase (LDH), 4.4 and 4.59; citrate synthase (CS), 0.154 and 0.13; hydroxyacyl-CoA dehydrogenase (HAD), 0.041 and 0.07. The mean difference between groups in TPDH and in (TPDH + LDH)/(CS + HAD) ratio were statistically significant. Maximum voluntary isometric strength (knee extension) was about 17% greater in cyclists than the mean value for Czechoslovakian men of the same age. A strong positive correlation (r = 0.72) between the percent of fast glycolytic fibers (type II B) and isometric strength was observed in the cyclists. Furthermore, mean weight-compensated maximal oxygen consumption (VO2 max, ml X kg-1 X min-1) for all subjects (n = 22) was significantly related to percent of slow oxidative fibers (type I) (r = 0.75) and to the mean diameter of type II B (r = 0.58), fast oxidative-glycolytic fibers (type II A) (r = 0.68) and type I fibers (r = 0.59).     

Tracking errors related to cardiac cycle: a new approach

One-dimensional manual tracking was investigated in relation to cardiac activity. The task of the subjects was, by means of a joy-stick, to maintain a spotlight between two vertical lines moving horizontally across an oscilloscope screen. Error incidence was time-locked with respect to the cardiac cycle. Error rate was higher for faster (2-s trial periods) than for slower (3-s trial periods) target movement. Using linear-ramp and sinusoidal movements, it was demonstrated that error incidence is associated with positive and negative cardiac acceleration.     

Hydrochlorothiazide-amiloride causes excessive urinary zinc excretion

Serum zinc levels and urinary zinc excretion were compared in 15 patients with essential hypertension taking chronically a combination of hydrochlorothiazide and amiloride as monotherapy, eight patients maintained with hydrochlorothiazide alone, and eight control subjects. Serum zinc values were statistically comparable in all three groups. However, urinary zinc excretion was abnormally elevated in the two patient groups. In the dosage used, amiloride did not have a zinc-sparing effect.