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Hand-grip strength has been identified as one limiting factor for manual lifting and carrying loads. To obtain epidemiologically relevant hand-grip strength data for pre-employment screening, we determined maximal isometric hand-grip strength in 1,654 healthy men and 533 healthy women aged 20-25 years. Moreover, to assess the potential margins for improvement in hand-grip strength of women by training, we studied 60 highly trained elite female athletes from sports known to require high hand-grip forces (judo, handball). Maximal isometric hand-grip force was recorded over 15 s using a handheld hand-grip ergometer. Biometric parameters included lean body mass (LBM) and hand dimensions. Mean maximal hand-grip strength showed the expected clear difference between men (541 N) and women (329 N). Less expected was the gender related distribution of hand-grip strength: 90% of females produced less force than 95% of males. Though female athletes were significantly stronger (444 N) than their untrained female counterparts, this value corresponded to only the 25th percentile of the male subjects. Hand-grip strength was linearly correlated with LBM. Furthermore, both relative hand-grip strength parameters (F (max)/body weight and F (max)/LBM) did not show any correlation to hand dimensions. The present findings show that the differences in hand-grip strength of men and women are larger than previously reported. An appreciable difference still remains when using lean body mass as reference. The results of female national elite athletes even indicate that the strength level attainable by extremely high training will rarely surpass the 50th percentile of untrained or not specifically trained men.

Recent theoretical studies have shown that spatial redistribution of surface water may explain the occurrence of patterns of alternating vegetated and degraded patches in semiarid grasslands. These results implied, however, that spatial redistribution processes cannot explain the collapse of production on coarser scales observed in these systems. We present a spatially explicit vegetation model to investigate possible mechanisms explaining irreversible vegetation collapse on coarse spatial scales. The model results indicate that the dynamics of vegetation on coarse scales are determined by the interaction of two spatial feedback processes. Loss of plant cover in a certain area results in increased availability of water in remaining vegetated patches through run-on of surface water, promoting within-patch plant production. Hence, spatial redistribution of surface water creates negative feedback between reduced plant cover and increased plant growth in remaining vegetation. Reduced plant cover, however, results in focusing of herbivore grazing in the remaining vegetation. Hence, redistribution of herbivores creates positive feedback between reduced plant cover and increased losses due to grazing in remaining vegetated patches, leading to collapse of the entire vegetation. This may explain irreversible vegetation shifts in semiarid grasslands on coarse spatial scales.

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The objective of the present study was to determine the characteristics of Doppler flow velocity wave forms in branch pulmonary arteries in relation to gestational age. A total of 111 singleton normal pregnancies were studied during the second half of pregnancy using a combined color-coded Doppler and two-dimensional real-time ultrasound system. Pulsed Doppler measurements of the most proximal branch of the right or left pulmonary artery were attempted during fetal apnea from a transverse cross-section of the fetal chest at the level of the cardiac four-chamber view after visualization with color Doppler. The success rate in obtaining the pulmonary arterial wave form was 85%. The wave form displayed a rapid systolic velocity acceleration, followed by an initially rapid but then more gradual velocity deceleration which was interrupted in most cases by a short reversed flow interval at the beginning of the diastolic phase of the cardiac cycle. The diastolic phase was characterized by forward flow. Peak systolic, end-diastolic and time-averaged velocity, pulsatility index, and systolic integral remained constant during gestation. Changes in vessel diameter or compliance may play a role in this. A gestational age-dependent rise was established for peak diastolic velocity, diastolic integral, and early peak diastolic reverse flow, whereas a gestational age-determined decline was found for the peak systolic/peak diastolic ratio. Fetal heart rate demonstrated a statistically significant increase relative to gestational age. However, the observed relation between the flow velocity wave form parameters, pulsatility index calculations, and gestational age was independent of fetal heart rate. It is speculated that peak diastolic velocity, diastolic integral, and peak systolic/peak diastolic ratio rather than the pulsatility index are useful in detecting gestational age-related changes in human fetal pulmonary vascular resistance.