Kohti omannäköistä akateemista asiantuntijuutta

Acute (0-2h) and delayed (2-8D) effects of exercise-induced muscle damage and soreness on elbow target movements.

The aim was to examine the acute and delayed effects of exercise-induced muscle damage and soreness on elbow target movements (TM) performance and control. Ten males performed an exercise of 50 maximal eccentric elbow actions. TMs were performed at three movement ranges. Maximal forces, active stretch reflex and TM were tested, and muscle soreness, creatine kinase and elbow joint stiffness were determined acute (after and 2 h) and delayed (2, 4, 6, 8d) postexercise. Both the long lasting muscle soreness and force drop were observed after the exercise. Joint stiffness was increased at 2 h postexercise. The highest deterioration in flexion-TM performance was found at the time (2 h) and at the…

Disturbed motor control of rhythmic movement at 2 h and delayed after maximal eccentric actions.

The aim of this study was to examine the influence of exercise-induced muscle damage on elbow rhythmic movement (RM) performance and neural activity pattern and to investigate whether this influence is joint angle specific. Ten males performed an exercise of 50 maximal eccentric elbow flexions in isokinetic machine with duty cycle of 1:15. Maximal dynamic and isometric force tests (90 degrees , 110 degrees and 130 degrees elbow angle) and both active and passive stretch reflex tests of elbow flexors were applied to the elbow joint. The intentional RM was performed in the horizontal plane at elbow angles; 60-120 degrees (SA-RM), 80-140 degrees (MA-RM) and 100-160 degrees (LA-RM). All measure…

Force and EMG power spectrum during and after eccentric and concentric fatigue.

Eccentric and concentric force and median frequency of the EMG power spectrum were measured during and immediately after maximal eccentric (EE) and concentric (CE) exercise and during the recovery period of 1 week. Eight male subjects performed EE and CE consisting of 100 maximal eccentric and concentric actions with elbow flexors during two separate exercise sessions. When comparing maximal eccentric and concentric actions before the exercises, the average force was higher (P<0.001) in eccentric than in concentric but the average rectified EMG (aEMG) values were the same with the two types of action. The average eccentric force decreased 53.3% after EE and 30.6% after CE, while the average…

Effect of electrode location on surface electromyography changes due to eccentric elbow flexor exercise.

Experiments were carried out to determine whether the location of electrodes has an effect on eccentric exercise–induced changes in surface electromyography (sEMG) variables in the biceps brachii muscle. sEMG signals were recorded with a grid of 64 electrodes before and up to 4 days post-exercise. Root mean square (RMS) and mean power frequency (MNF) were calculated for: (1) each channel; (2) as an average of all channels; and (3) as an average of individual channel rows and columns. Mean muscle-fiber conduction velocity (CV) was estimated similarly but was based on double-differential channels. Maximal isometric voluntary torque decreased 21.3 ± 5.6% post-exercise. The average sEMG variabl…

Adaptive changes in motor control of rhythmic movement after maximal eccentric actions.

Effects of an exhaustive eccentric exercise (EE) on the motor control of maximal velocity rhythmic elbow extension/flexion movement (RM) were examined in eight male students. The exhaustive EE consisted of 100 maximal eccentric actions of the elbow flexor muscles. Movement range was 40-170 degrees in EE at an angular velocity of 2rads(-1). A directive scaled RM of 60 degrees with visual feedback was performed in a sitting position, with the right forearm fixed to the lever arm in horizontal plane above protractor. Surface electromyographic activity (EMG) was recorded from the biceps brachii (BB) and triceps brachii (TB) muscles. Maximal isokinetic eccentric and concentric tests and RM test …

Instructions for External Focus of Attention Improved Taekwondo Kicking Performance Only Among Less Skilled Youth

External focus of attention (EFA) studies among children have yielded more equivocal results than have those among adults. Some investigators have found an internal focus of attention (IFA) advantage in children and have explained their results by children’s generally lower skill levels, compared to adults. According to the constrained action hypothesis, children’s lower skill levels are not yet associated with over-learned automatic movement patterns, so their motor performance is not disrupted by IFA instructions. In this study, our objective was to examine a possible interaction effect between children’s skill levels and their exposure to either IFA or EFA instructions on motor performa…

Motor control of fast voluntary elbow movements : exercise-induced muscle damage and soreness and learning interventions

Impaired action potential conduction at high force levels after eccentric exercise

High-density surface electromyography was used to examine whether gross sarcolemmal function is impaired in m. biceps brachii after intensive eccentric elbow flexor exercise, when measured at wide range of isometric contraction levels. Root mean square (RMS), mean power frequency (MNF) and mean muscle fibre conduction velocity (CV) were calculated before and up to four days post-exercise. Maximal isometric voluntary (MVC) force decreased by 21.3+/-5.6% two hours after exercise, and by 12.6+/-11.1% two days post-exercise. CV and MNF decreased both during MVC (CV from 4.1+/-0.3m/s to 3.8+/-0.4m/s and MNF from 92.6+/-10 Hz to 85.2+/-11 Hz) and during electrically evoked maximal M-wave (CV from…