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Biomedical subjects

U Kobryn

Publications and source records attributed to U Kobryn.

32 records · Page 2Linked to original sources
PubMed1981

Effects of repeated fatiguing rhythmical hand work.

In a model work place (hand-grip dynamometer), eleven subjects performed rhythmical hand-grip contractions to exhaustion (frequency 30/min). In each working cycle the contraction and rest phases were distinguished. The work to exhaustion was repeated four times (four working periods with 156-min rest intervals). The tests were performed at 40, 60, 80, 100% MVC. Analysis of Variance showed no difference in the group means (mean values of each working period and load level) for the duration of the contraction or rest phases, the integrated bioelectrical muscle activity (iEMG) of flexors, extensors, brachioradialis (iEMG referred to working cycle and contraction phase) or iEMG of the thenar muscles (referring to the working cycle), or in the duration of the R-R interval in the ECG during comparable periods of the experiments. The endurance times decreased from working period 1-4, and a similar decrease occurred in the force-time product. It may be concluded from these results that 15 min rest is insufficient for adequate recovery from hand-exhaustion exercise.

Adult↗
PubMed1978

[Muscle activity and heart rate during rhythmical work using a hand ergometer. II. Heart rate, mechanical and bioelectrical activity of muscles during work with different loads and in relation to endurance].

The study has been made to analyse changes in heart rate, in mechanical and bioelectrical muscle activity during thythmical handgrip contractions. Loads of 20% to 100% of the maximal voluntary contraction (MVC) were applied. The working frequency was 30 cpm. With loads of 40%--100% of the maximal voluntary contraction (MVC) the following characteristic changes were obtained: Both the plane of the mechanogram and the duration of the mechanogram increased permanently. The heart rate rose to the end of the experiment and so did the EMGs of the flexor, the extensor, the brachioradial muscle and the muscle of the thenar. The rate of the rise (%/s) of all physiological functions was greatest during maximal load test and decreased with decreasing contraction strength. The endurance as a function of the force showed a parabolic curve. The physical endurance capacity of this rhythmical hand work is between 20% and 40% MVC.

Female↗
PubMed1977

[Muscle activity and heart rate during rhythmical work on the hand ergometer. I. Heart rate, bioelectric muscle activity and mechanogram relative to the strength of contraction].

The experiments were carried out on 11 subjects ranging in the age from 23 to 37 years. Heart rate, integrated electrical activity from 4 muscles of the forearm and the hand and mechanical activity were measured simultaneously during rhythmical work using a hand-ergometer. The strength of the dynamic contractions was 20, 40, 60, 80 and 100% of a maximal voluntary contraction. The mean values of the maximal voluntary contraction obtained on male subjects were 57.3 kp and on female subjects 33.2 kp. The results showed that during dynamic contractions mechanical activity was related to the integrated electrical activity and both integrated electrial activity of 3 muscles and heart rate were linearly related to the load. The correlation coefficients for the EMG/EMG relationships of different muscles and for the EMG/heart rate varied between 0.83 and 0.98.

Adult↗