Search results for "Human leg"
showing 9 items of 9 documents
Neuromuscular function and mechanical efficiency of human leg extensor muscles during jumping exercises
1982
The influence of prestretch amplitude on the mechanical efficiency was examined with 5 subjects, who performed 5 different series of vertical jumps, each of which differed with respect to the mechanics of the knee joint action during the prestretch (eccentric) phase of the contact on the floor. Electromyographic activity was recorded from the major extensor muscles during the entire work period of 1 min per series. In addition, expired air was collected during the test and recovery for determination of energy expenditure. Mechanical work was calculated from the vertical displacement of the body during the jumps. The results indicated that high net efficiency of 38.7% was observed in conditi…
Mechanical characteristics and fiber composition of human leg extensor muscles.
1979
To investigate the influence of skeletal muscle fiber composition on the mechanical performance of human skeletal muscle under dynamic conditions, 34 physical education students with differing muscle fiber composition (M. vastus lateralis) were used as subjects to perform maximal vertical jumps on the force-platform. Two kinds of jumps were performed: one from a static starting position (SJ), the other with a preliminary counter-movement (CMJ). The calculated mechanical parameters included height of rise of center of gravity (h), average force (F), net impulse (NI) and average mechanical power (W). It was observed that the percentage of fast twitch fibers was significantly related (p less t…
Spatial variability of muscle activity during human walking: The effects of different EMG normalization approaches
2015
Human leg muscles are often activated inhomogeneously, e.g. in standing. This may also occur in complex tasks like walking. Thus, bipolar surface electromyography (sEMG) may not accurately represent whole muscle activity. This study used 64-electrode high-density sEMG (HD-sEMG) to examine spatial variability of lateral gastrocnemius (LG) muscle activity during the stance phase of walking, maximal voluntary contractions (MVCs) and maximal M-waves, and determined the effects of different normalization approaches on spatial and inter-participant variability. Plantar flexion MVC, maximal electrically elicited M-waves and walking at self-selected speed were recorded in eight healthy males aged 2…
Cerebral potentials elicited by mechanical stimuli to the human leg: influence of artifacts
1992
Mechanical stimulation with a reflex hammer was applied to the quadriceps muscle tendon of healthy volunteers and patients. The time-locked electrical signals were recorded from the scalp. In all cases, reproducible potentials could be recorded, with latencies in a range of 20 ms to 100 ms. The potentials recorded in patients under complete spinal anesthesia were similar to those derived before the anesthesia. In brain dead patients who showed absence of median nerve or posterior tibial nerve SEP, reproducible potentials after mechanical stimuli could be recorded as well. The results suggest that the hammer taps lead to mechanical shock waves which are propagated along the body producing ti…
Mechanical power test and fiber composition of human leg extensor muscles.
1983
The present study was undertaken to assess the relationship between the mechanical power developed during new anaerobic power test and muscular fiber distribution. Ten track and field male athletes were used as subjects, whose muscle fiber composition (m. vastus lateralis) varied from 25 to 58 fast twitch (FT) fibers. The test consisted of measuring the flight time with a special timer during 60 s continuous jumping. A formula was derived to allow the calculation of mechanical power during a certain period of time (e.g., in the present study every 15 s during 60 s of jumping performance). The relationship between the mechanical power for the first 15 s period correlated best with fast twitc…
Determination of hydrodynamic drag forces and drag coefficients on human leg/foot model during knee exercise.
2000
Objective. The purpose of this laboratory experiment was to measure hydrodynamic drag forces in barefoot/hydro-boot conditions and accordingly, to determine the coefficients of drag on human leg/foot model during simulated knee extension–flexion exercise. Design. The prosthesis of the human lower leg was set in a water tank and connected into an isokinetic force dynamometer to measure resistive forces during knee motion. Background. Quantifying resistance for aquatic exercises has been a challenge in hydrotherapy. The use of models of foot/leg provides a practical method to calculate coefficients of drag and to estimate resistance for rehabilitation purposes in musculoskeletal and amputee p…
Designing a Specialized Devices for Correction of the Axis Deviation at the Human Leg
2013
The presented article is an original contribution which implies the design of a specialized device for high tybial osteotomy (HTO) optimization. In the papers are presented the sources that imply HTO, the axial deviations of the human lower member from the correct position. This sources are the gonarthosys owed to the usage of the knees cartilages or owed to some diseases (such as the Blount disease) and the vicious consolidated fractures. After presenting the needs to realize such a specialized device for HTO, the principal requests the device shall fulfill are underlined. Starting from these , two sub ensembles were projected, one for the tibial positioning and for the execution of the ho…
Force-time characteristics and fiber composition in human leg extensor muscles
1978
Recording of the force-time (f-t) characteristics of muscular contraction expresses the rate at which tension is developed. To further understand the problems involved in force production during voluntary contraction, the f-t curve was registered during maximal voluntary isometric extension of both legs performed in the sitting position with the knee angle at 107 degrees. 38 athletes representing various sport events, five pairs of monozygous, and ten pairs of dizygous twins were used as subjects. The reference group consisted of eight normal men. The data disclosed that the time to produce certain force levels showed good trial-to-trial and satisfactory day-to-day reproducibility below ten…
Experimental modular stand used for studies of the High Tibial Osteotomy
2017
The optimization of the surgery strategies for the correction of the axial deviations of the human lower member presents a great importance both for the affected patients and for surgeons. This article seeks to develop a modular stand used mainly for experimental study of the High Tibial Osteotomy (HTO). In the article it is also shown the relation between the axial deviations of the human leg and their corrections using HTO. The modular devices were designed, executed and used in the experimental research.