Effects of heat and cold application on turns and amplitude in surface EMG.

The purpose of this study was to investigate the effects of cooling and heating of muscles on parameters of surface EMG (SEMG) under various well defined grades of isometric muscle contraction. In 32 healthy volunteers, aged 20-30 years, turns and amplitude (RMS) analysis was done in SEMG from the hand extensors. Muscle strength was defined by a new developed hand dynamometer. Values for RMS and turns in case of maximal voluntary contraction (MVC) over periods of 20 sec were determined for each volunteer and subsequently RMS and turns were measured during isometric contractions of 10%, 30%, 50% and 80% of MVC, interrupted each by rest periods. This procedure was repeated after cooling and warming the forearm with thermo packs. For control purposes the same investigations with three measurement periods of SEMG were done following the same time schedule without thermic stimuli. With increasing isometric contractions turns increased after heat application and decreased after ice application, compared to the values achieved without thermic stimuli. The differences were significant from a level of 30% of MVC (p < 0.05). No corresponding changes were seen for RMS. In the control experiment values of turns and RMS did not differ in the three measurement periods. It is concluded, that the amplitude in SEMG tracings seems to be a reliable parameter of muscle force, whereas turns are sensitive to temperature. They might be useful markers for therapeutic approaches targeted at the muscle.

[Muscle training by electrostimulation]. / Muskeltraining durch Elektrostimulation.

Repeated electrical stimulation of skeletal muscles with intact innervation can lead to increased muscular performance. This form of treatment is employed, for example, in atrophy prophylaxis, re-establishment of lost muscular power, and selective strengthening of isolated muscles or muscle groups, and has also been recommended for sport-related performance training. For the most part, it represents an adjuvant measure to active exercise. The selected current forms and stimulation parameters must be oriented to the laws of stimulation physiology. Suitable selection and positioning of electrodes, together with dosage are decisive for the success of treatment. Recent aspects of electrostimulation are so-called fiberspecific electrotraining and the question as to whether the use of certain stimulation frequencies can preferentially be used for phasic or tonic muscle fibers. Electrostimulation of denervated muscles is controversial.

Dose-effect relationship between smoking and blood rheology.

Five groups of male blood donors were investigated. The first group had never smoked, the second were ex-smokers, the third smoked between 10 and 20 cigarettes per day, the fourth between 21 and 40, and the fifth more than that. Haematocrit, white cell count, plasma and native blood viscosity, blood cell filterability and aggregation, plasma colloid oncotic pressure as well as fibrinogen were measured. Results show that smoking is associated with a progressive significant deterioration of the above haemorheologic variables. These changes are interpreted as an absolute and a relative polycythaemia possibly in conjunction with a chronic inflammatory process. It is concluded that smoking induces a dose-related increase in viscosity of blood among young men which is reversible by abstention.

Sauna effects on hemorheology and other variables.

Acute sauna induces decreased blood fluidity as quantified by measurements of blood and plasma viscosity, hematocrit, red cell filterability, and aggregation. The effect is far less prominent when sauna treatment is continued regularly for eight weeks. In this case there are only minor changes in native blood viscosity and hematocrit together with slight variations in hematologic measurements, calcium, and serum protein pattern. Thus, from the hemorheology point of view, sauna leads to adverse effects predominantly acutely, while long-term effects seem negligible. Such aspects are worth considering in patients with high cardiovascular risks, and marked hypoperfusion.

A new simple method for measuring red cell aggregation.

A viscometric technique is outlined for the measurement of red cell aggregation (RCA). Samples are submitted to a constant shear rate of 2,4 s-1. The resulting time dependent torque signal reaches a peak soon after starting the rotation and falls within seconds to a constant baseline, thereby describing an area "F" with the baseline. The shear history of the sample being strictly controlled, "F" is reproducible and shows a direct, positive correlation with RCA as determined for instance in the "aggregometer".