The purpose of this study was to examine the properties of the venous vascular system in the lower extremities of individuals with long-standing paraplegia (PP). The venous volume variations (VVV) , the venous capacity (VC), the venous emptying rate (VER) and the venous flow resistance (VFR) were measured in the left calf of 14 male PP and 12 male able-bodied subjects (ABS) by means of strain-gauge occlusion plethysmography. VVV and VC were significantly lower in PP compared to ABS, -45% and -50% respectively. Both groups showed a similar resting venous pressure in the calf (PP = 24.4 mmHg; ABS = 19.6 mmHg). VER was significantly lower (-60%) and hence VFR was significantly higher (+75%) in PP compared to ABS. This study demonstrates that the venous vascular properties in the legs of individuals with paraplegia have changed, i. e. a decrease in venous distensibility and capacity and an increase in venous flow resistance. This is most probably the result of vascular adaptations to inactivity and muscle atrophy rather than the effect of a non-working leg-muscle pump and sympathetic denervation.

Vasovagal syncope is usually described as a sudden and transient loss of consciousness that resolves spontaneously. Cardiocirculatory changes are well described during and before syncope. However, changes in the cerebral oxygenation are not well defined. In this study, near-infrared spectroscopy (NIRS) was used to assess the cerebral oxygenation directly during 80 degree head-up (HU) tilt. To simulate central hypovolaemia, 500 ml of blood was drawn from each of 10 healthy subjects. Oxygenation index (OI) was defined as the difference between oxy- and deoxyhaemoglobin concentration. Blood pressure, heart rate and cardiac output were monitored using a finger plethysmographic device. The protocol was divided into two stages, each consisting of a 15-min stabilization period in the supine (SUP) position, 15 min in HU position and another 10 min in SUP position. Between both stages, blood was drawn from the subject. Haemoglobin concentration and haematocrit were measured before and 30 min after withdrawal of blood. No compensatory haemodilution was observed. During HU position in the second stage, six subjects showed signs of presyncope (F) and four did not (NF). A significant difference between F and NF was found in the observation that, before fainting, the OI of F showed a steady and significant (P = 0.02) decrease (-1.4 +/- 0.5 microM min-1) compared with NF (-0.18 +/- 0.16 microM min-1). This indicates that the onset of (pre)syncope is preceded by a mismatch between oxygen demand and oxygen supply in the cerebrum. Using NIRS enabled us to monitor this mismatch and to predict the onset of a syncope before clear signs in cardiocirculatory variables were visible.

The force-velocity relationship of maximal contractions with the handgrip muscles is established in a group of subjects. The effect of different muscle temperatures is studied. The parameters vo (maximal velocity), Fo (maximal force), Pmax (maximal power), a/Fo and H (both parameters describing the shape of the curve), and Ft/Fo (the value of the force at which power is maximal) are established. It is shown that 1) in repeated measurements the coefficient of variation in general is less than 10% for all the parameters except a/Fo; 2) the parameter a/Fo should be discarded in comparative measurements since it is not linearly related to the course of the curve. A parameter called H should be used instead to describe the curvature; 3) an increase in muscle temperature is accompanied by an increase in magnitude of all parameters except Fo. The temperature effect expressed as Q10 in the range 22-38 degrees C is in the order of 1.2.

The inter- and intraindividual variability of the frequency power density spectral and surface EMG amplitude parameters and of the muscle fiber conduction velocity (MFCV) is studied in 26 healthy volunteers during fatiguing isometric ischemic intermittent exercise of the m. biceps brachii at 80% of the maximal voluntary contraction level, with a contraction rate of 30/min. No significant age effects were found. Males were significantly stronger compared with females. The higher initial SEMG amplitude and the stronger shift of the frequency power density spectrum (PDS) to lower frequencies appear to be significantly correlated with males. Fatigue induces an almost proportional compression of the SEMG frequency content. The muscle fiber conduction velocity has the highest intraindividual reproducibility (r = 0.81). Despite the definite and strong influence of the MFCV on the PDS, the shift of the PDS can not be explained by a change of MFCV alone.

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