Motor-unit activity in the trapezius muscle during rest, while inputting data, and during fast finger tapping.

The Cinderella hypothesis postulates the continuous activity of specific motor units during low-level muscle contraction and contradicts the concept of motor-unit substitution. Constant trapezius muscle activity has been reported in typical visual-display-unit-related tasks. If it can be shown that constant muscle activity can be caused by the continuous firing of single motor units, this could explain the frequent complaints of muscular neck pain reported by computer users. The present study was undertaken to investigate motor-unit activity in the trapezius muscle during resting with closed eyes, while inputting three-digit numbers with auditory presentation at a rate of 0.5 Hz, and while tapping on a key with the right index finger at a rate of 5 Hz. Electrodes with four fine wires were inserted into the right upper trapezius muscle of six healthy subjects, and three-channel intramuscular electromyography was recorded. The decomposition programme MAPQuest, developed to analyse short-term one-channel signals, was complemented with MAPView, a programme that merges the short-term results of 10 s to a 3-min analysis. The results showed that activity in the trapezius muscle was induced in one subject while resting, in two subjects while inputting data, and in five subjects while finger tapping. Long-lasting single motor-unit firing was observed in two subjects while inputting data and in one subject while finger tapping. Whilst our findings may support the Cinderella hypothesis, the measurement periods are too short to confirm it fully, and for further discussion it is necessary to record and analyse for longer periods.

Co-activity of the trapezius and upper arm muscles with finger tapping at different rates and trunk postures.

In the context of finding a model that describes the pathophysiological mechanisms leading to muscle pain at low-intensity repetitive work, in this study we investigated whether a simplified finger motor task that requires little mental demand can cause increased muscle activity in the upper arms and neck, and examined the impact of the variation of two parameters, finger tapping rate and body posture. Using the 5th and 95th percentiles from the surface electromyogram of six muscles of the fingers, upper arm and neck, we determined the static and dynamic components of the muscle activity. Correlation methods were used to find a component in the muscle activity that originated from the rhythm of the finger tapping. Further investigations included tapping steadiness and finger force. It was found that in many, but not all subjects, low or even high activity was constantly present in the upper arm and trapezius muscles, sometimes even during relaxation. Fast tapping and a forward-leaning body posture caused considerable increases, while a slightly reclined posture helped to reduce co-activity. However, motor control patterns varied strongly between individuals. Since certain subjects showed no co-activity at all we can assume that trapezius and upper-arm activation is not necessarily required for the completion of a task similar to ours. This may explain why some VDU users develop work-related musculoskeletal disorders while others remain healthy.

Build-up maintenance of IgG serum concentrations with intravenous immunoglobulin in patients with primary humoral immunodeficiency.

6 patients with antibody deficiency disease had intravenous immunoglobulin substitution and their serum IgG levels were monitored for at least 6 months. After three IgG infusions of 6-12 g each at intervals of 3 or 4 weeks, the IgG serum concentrations were between 300 and 500 mg/dl in 3 patients. In the 3 other patients, higher serum levels were obtained after considerably more IgG infusions given at intervals of 8 days or less. Maintenance of subnormal levels was achieved by replacement of approximately 10 mg/kg body weight/day. In 1 patient, the serum IgG was kept at about 1,000 mg/dl by replacement of 54 mg/kg/day, i.e. by infusions of 9 g every 3-4 days.

[Prevention and therapy with immunoglobulin SRK]. / Prophylaxe und Therapie mit Immunglobulin SRK.

In a clinical study the tolerance and efficacy of a gamma-globulin, treated at pH 4, has been studied. This preparation manufactured by the "Zentrallaboratorium des Blutspendedienstes SRK" can be given intravenously without any risk of untoward reactions. It has been applied in high dosages up to 99 g per week. In 15 cases with primary humoral immunodeficiency, the frequency and the severity of acute bacterial infections were markedly reduced or completely absent. In 16 patients without antibody deficiency but suffering from severe septic-toxic infections, results with Immunglobulin SRK were encouraging and warrant further controlled studies.