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The aim of this study is to examine the functional changes in different sites of the human neuromuscular system during fatiguing submaximal static contractions in respect to gender and age. Women and men aged 20-59 years are volunteers in the present study. The body of subjects is distributed in 3 age groups: (1) 20-29-year-olds; (2) 35-45-year-olds; (3) 50-59-year-olds. Two muscle groups are planned to be measured: plantarflexor (PF) and back extensor (BE) muscles. Electrical stimulation in combination with electromyography (EMG) and isometric dynamography is used for measuring the twitch contractile properties and H-reflex characteristics of PF muscles. Subjects perform at 2-week interval 2 series of static contractions of PF muscles until exhaustion at two different levels of force: 70% and 30% of maximal voluntary contraction force. Integrated EMG and power spectrum characteristics are recorded following each fatiguing static contraction. BE muscle fatigue during Sorensen back endurance test until exhaustion is assessed using integrated EMG and power spectrum characteristics, and endurance time. Habitual physical activity over the years and health status are assessed by specialized questionnaires. The planned study provides additional scientific information about physiological aspects of neuromuscular fatigue following submaximal static contractions at different levels of force, including coexistence of twitch potentiation and fatigue and post-contractile depression in respect to gender and age. One purpose of this study is to examine the relationship between anthropometric characteristics and fatigability of BE muscles during submaximal static contractions in respect to gender and age. The results of this study can be used by physiologists, specialists of ergonomics, gerontologists and geriatrists, health-related fitness instructors, coaches. These results can be applied for improving the effectivness of recreational physical activity programs. |