engleski

Morphohistochemical and emg observations of musculus biceps brachii in humans of various levels of physical activity

Skeletal muscles are the generators of active force and therefore the actuators in the locomotor system. Muscle tissue, namely, is characterized by properties like excitability, conductivity, elasticity and above all contractility, enabling the muscle the role of actuator. When researching muscle and muscular system it is important to explore the relation between the muscle's structure and function. We have pursued a study along these lines by providing morphohistochemical analysis of human muscle biceps brachii and electromyography (EMG) and dynamometry measurements of actively contracting muscle. Plotting the histograms of occurence of fiber diameters, at the scale of 3 micro meters (um) resolution, reveals that in younger persons the biceps brachii specimen for ATP-ase activity at pH 4.3 show a greater frequency of type II fibers with a diameter from 91 to 106 um, while type I fibers have the highest frequency of occurence at diameters ranging from 22 to 28 um. In older individuals the type II fibers are smaller with the highest frequency of fibers with diameters ranging from 61 to 79 um ; the type I fibers are larger, with the highest frequency of fibers with diameters ranging from 58 to 76 um. Despite significantly different levels of maximum isometric force developed by our subjects - corresponding to their physical abilities - in all cases analyzed a proportionality between measured force and smoothed EMG values may be observed. The current level of scientific knowledge suggests with high probability, the existence, in subjects manifesting higher isometric force gradients, of a higher proportion of type II fibers characterized by higher contraction strength.

Human m. biceps brachii ; myosin ATP-ase ; EMG ; dynamometry

nije evidentirano