High-intensity sprint fatigue does not alter constant-submaximal velocity running mechanics and spring-mass behavior

We investigated the changes in constant velocity spring-mass behavior after high intensity sprint fatigue in order to better interpret the results recently reported after ultra-long distance (ULD) exercises. Our hypothesis was that after repeated sprints (RS), subjects may likely experience losses of force such as after ULD, but the necessity to modify their running pattern to attenuate the overall impact at each step (such as after ULD) may not be present. Eleven male subjects performed four sets of five 6-s sprints with 24-s recovery between sprints and 3 min between sets, on a sprint treadmill and on a bicycle ergometer. For each session, their running mechanics and spring-mass characteristics were measured at 10 and 20 km h⁻¹ on an instrumented treadmill before and after RS. Two-way (period and velocity) ANOVAs showed that high-intensity fatigue did not induce any change in the constant velocity running pattern at low or high velocity, after both running and cycling RS, despite significant decreases (P < 0.001) in maximal power (−27.1 ± 8.2% after running RS and −15.4 ± 11.5 % after cycling RS) and knee extensors maximal voluntary force (−18.8 ± 6.7 % after running RS and −15.0 ± 7.6 % after cycling RS). These results bring indirect support to the hypothesis put forward in recent ULD studies that the changes in running mechanics observed after ULD are likely not related to the decrease in strength capabilities, but rather to the necessity for subjects to adopt a protective running pattern.     

Static and dynamic assessment of the Biodex dynamometer

Summary The validity and accuracy of the Biodex dynamometer was investigated under static and dynamic conditions. Static torque and angular position output correlated well with externally derived data (r=0.998 andr>0.999, respectively). Three subjects performed maximal voluntary knee extensions and flexions at angular velocities from 60 to 450° · s^–1. Using linear accelerometry, high speed filming and Biodex software, data were collected for lever arm angular velocity and linear accelerations, and subject generated torque. Analysis of synchronized angular position and velocity changes revealed the dynamometer controlled angular velocity of the lever arm to within 3.5% of the preset value. Small transient velocity overshoots were apparent on reaching the set velocity. High frequency torque artefacts were observed at all test velocities, but most noticeably at the faster speeds, and were associated with lever arm accelerations accompanying directional changes, application of resistive torques by the dynamometer, and limb instability. Isokinematic torques collected from ten subjects (240, 300 and 400° · s^–1) identified possible errors associated with reporting knee extension torques at 30° of flexion. As a result of tissue and padding compliance, leg extension angular velocity exceeded lever arm angular velocity over most of the range of motion, while during flexion this compliance meant that knee and lever arm angles were not always identical, particularly at the start of motion. Nevertheless, the Biodex dynamometer was found to be both a valid and an accurate research tool; however, caution must be expercised when interpreting and ascribing torques and angular velocities to the limb producing motion.     

Effects of a single habituation session on neuromuscular isokinetic profile at different movement velocities

Single training session (STS) may increase the power output (i.e., maximal torque) in different contraction types; however, little is known about the neuromuscular adaptations to reach this enhancement. In this way, the present study examined the differences between knee extensors EMG, kinematics, and dynamometry at 60 and 180° s⁻¹ before (PRE) and after (POST) a STS. Seventeen healthy males completed three different tasks: (1) 5-maximal isokinetic knee extensions, without previous habituation (PRE) at 60 and 180° s⁻¹; (2) in the same day and after a proper rest, two bouts of 5-maximal isokinetic contractions (STS) at 60 and 180° s⁻¹; and (3) in a new visit, POST consisted in new 5-maximal isokinetic contractions at 60 and 180° s⁻¹. The main parameters examined were: knee extensors peak torque (PT), total work (TW), EMG (prior to the movement onset, agonist and antagonist activation), rate of force (RFD), and velocity development (RVD). There was significant increase in PT [12% (60° s⁻¹) and 8.7% (180° s⁻¹)] and TW [13.5% (60° s⁻¹) and 10.7% (180° s⁻¹)] from PRE to POST sessions. Increases in RFD were found for both velocities (p < 0.05); however, RVD and vastus lateralis EMG prior to the movement onset were significantly higher for POST only at 60° s⁻¹. The RFD percentage of change (%change) was significantly correlated to %change for PT at 60° s⁻¹ (r ² = 0.53) and 180° s⁻¹ (r ² = 0.45). In conclusion, STS improves neural strategies to contract muscles stronger and faster at the slowest velocity, while higher velocities present different adaptations and might need more practice to further adaptations.     

Acute and 2?days delayed effects of exhaustive stretch-shortening cycle exercise on barefoot walking and running patterns

This study investigated the acute and 2?days delayed influences of exhaustive stretch-shortening cycle exercise (SSC) on barefoot walking and running gait patterns. The SSC exercise was performed on a sledge apparatus, on which the subjects (N?=?10) repeated until exhaustion intermittent series of 25 bilateral submaximal rebounds. Maximal drop-jumps and submaximal barefoot treadmill walking and running were performed before (PRE) and after (POST) the exhaustive exercise and repeated 48?h (D2) later. Electromyographic activity and 3D kinematics of the right lower limb and foot were recorded for 15?s at gait initiation (BEG) and at the end (END: at 3?min of walk and 5?min of run). The exhaustive SSC exercise resulted in 6% reductions in maximal drop jump performance at POST and D2, and affected mostly both gait patterns at D2. The walking pattern presented compensatory neural adjustments within the triceps surae muscle group. This expected pain-induced protective strategy of the soleus muscle was sufficient to preserve the kinematics pattern. The running condition revealed a major knee strategy, which might support the concept of pain protective strategy of knee extensor muscles at the expense of impact cushioning. Regardless the testing session, most parameters showed fatigue-induced changes at gait initiation (BEG), which were opposite to subsequent BEG to END adjustments. This is likely to support anticipatory strategies rather than progressive adjustments during the exercise.     

Differences in the electromyographic activity of the hamstring muscles during maximal eccentric knee flexion

This study investigated the effects of the knee joint angle and angular velocity on hamstring muscles’ activation patterns during maximum eccentric knee flexion contractions. Ten healthy young males (23.4 ± 1.3 years) performed eccentric knee flexion at constant velocities of 10, 60, 180, and 300 deg/s in random order. The eccentric knee flexion torque and the surface electromyographic (EMG) activity of the biceps femoris (BF), semitendinosus (ST), and semimembranosus (SM) muscles were measured. The results of torque during 10 deg/s were lower than the faster velocities. No significant change was found in eccentric torque output and the EMG amplitude with change in the faster test velocities, although those values showed a decreasing tendency as the knee approached extension. Furthermore, the EMG amplitude of the BF decreased significantly as the knee approached extension, although the EMG activity of the ST and SM remained constant. These results suggest that the neural inhibitory mechanism might be involved in decreasing in maximal voluntary force and hamstring muscles activation toward the knee extension during high-velocity eccentric movement and therefore subjects have difficulties to maintain high eccentric force level throughout the motion. Moreover, the possible mechanism reducing the BF muscle activation as the knee approaches extension was architectural differences in the hamstring muscles, which might reflect each muscle’s function.     

Effects of different strength training regimes on moment and power generation during dynamic knee extensions

This study examined the effect of different training regimes on moment and power generation during maximal knee extensions at low to very high extension velocities (0–1000°·s^–1 individual range). A group of 24 soccer players performed 12 weeks of progressively adjusted strength training of the knee extensors at either high resistance (HR,n=7), low resistance (LR,n=6), loaded kicking movements (FU,n=6), while one group served as controls (n=5). Moment and power generation of the knee extensors were determined before and after the training period with a nonisokinetic measuring method recently described. Following HR training, knee extension moment increased 9%–10% at knee angular velocities 0 (isometric) and 30° · s^–1 (P<0.05), peak moment increased 20% at 240–300°·s^–1 (P<0.05), while power generation increased 5%–29% at 240–480° · s^–1 (P<0.01). In addition, in the HR group maximal recorded power increased 45% (P<0.01). After FU training a 7%–13% increase in moment and power was observed at 30–180° · s^–1 (P<0.05). Following LR training, peak moment increased 9% at 120° · s^–1 (P<0.05). Improvements in knee extension moment and power were generally related to the angular velocities employed during training. However, as evaluated using the present measuring method, moment and power increased not only at very low but also at high knee angular velocities following the high-resistance strength training.     

Sagittal knee joint kinematics and energetics in response to different landing heights and techniques

Single-leg and double-leg landing techniques are common athletic maneuvers typically performed from various landing heights during intensive sports activities. However, it is still unclear how the knee joint responds in terms of kinematics and energetics to the combined effects of different landing heights and techniques. We hypothesized that the knee displays greater flexion angles and angular velocities, joint power and work in response to the larger peak ground reaction force from 0.6-m height, compared to 0.3-m height. We further hypothesized that the knee exhibits elevated flexion angles and angular velocities, joint power and work during double-leg landing, relative to single-leg landing. Ground reaction force, knee joint kinematics and energetics data were obtained from 10 subjects performing single-leg and double-leg landing from 0.3-m to 0.6-m heights, using motion-capture system and force-plates. Higher peak ground reaction force (p < 0.05) was observed during single-leg landing and/or at greater landing height. We found greater knee flexion angles and angular velocities (p < 0.05) during double-leg landing and/or at greater landing height. Elevated knee joint power and work were noted (p < 0.05) during double-leg landing and/or at greater landing height. The knee joint is able to respond more effectively in terms of kinematics and energetics to a larger landing impact from an elevated height during double-leg landing, compared to single-leg landing. This allows better shock absorption and thus minimizes the risk of sustaining lower extremity injuries.     

Moment and power generation during maximal knee extensions performed at low and high speeds

In the present study a method was developed to determine knee joint moment and power generated at low to very high velocities of knee extension. A group of 21 male subjects performed maximal knee extensions at four levels of external loading provided by a flywheel system. Knee extension was performed with no restrictions on joint angular velocity and acceleration. An interpolation procedure was employed to obtain moment and power at standard velocities. During each single knee extension peak velocity, peak moment, peak power and moment and power at 50° knee flexion were determined (0°=full extension). While maximal recorded angular velocity averaged 693°· s^–1 (range 479–1030), maximal recorded moment and power were 226 N · m (157–278) and 1140 W (573–1688), respectively, which were generated at velocities of 55° · s^–1 (12–148) and 523° · s^–1 (327–846). Isokinetic moment and power were obtained for comparison. The velocity range applied was larger using the flywheel method (21–1030° · s^–1 individual range) than that achieved isokinetically (30–240° · s^–1). Significant differences were observed between flywheel and isokinetic measurements. These discrepancies may be ascribed to differences in the time course of muscle length change and contractile force generation imposed by the two measuring methods. However, by the nonisokinetic measuring method presently employed, knee extension moment and power could be determined from low to very high angular extension velocity, at loading and contraction conditions comparable to those encountered during sport and exercise.     

Effects of knee and ankle muscle fatigue on postural control in the unipedal stance

The aim of this study was to compare the effects of acute muscle fatigue of the ankle and knee musculature on postural control by immediate measures after performing fatiguing tasks (POST condition). One group of subjects (n = 8) performed a fatiguing task by voluntary contractions of the triceps surae (group TRI) and the other (n = 9) performed a fatiguing task by voluntary contractions of the quadriceps femoris (group QUA). Each muscle group was exercised until the loss of maximal voluntary contraction torque reached 50% (isokinetic dynamometer). Posture was assessed by measuring the centre of foot pressure (COP) with a force platform during a test of unipedal quiet standing posture with eyes closed. Initially (in PRE condition), the mean COP velocity was not significantly different between group TRI and group QUA. In POST condition, the mean COP velocity increased more in group QUA than in group TRI. The postural control was more impaired by knee muscle fatigue than by ankle muscle fatigue.     

Association Between Knee- and Hip-Extensor Strength and Running-Related Injury Biomechanics in Collegiate Distance Runners

ContextRunning-related injuries are common in distance runners. Strength training is used for performance enhancement and injury prevention. However, the association between maximal strength and distance-running biomechanics is unclear.ObjectiveTo determine the relationship between maximal knee- and hip-extensor strength and running biomechanics previously associated with injury risk.DesignCross-sectional study.SettingResearch laboratory.Patients or Other ParticipantsA total of 36 collegiate distance runners (26 men, 10 women; age = 20.0 ± 1.5 years, height = 1.74 ± 0.09 m, mass = 61.97 ± 8.26 kg).Main Outcome Measure(s)Strength was assessed using the 1-repetition maximum (1RM) back squat and maximal voluntary isometric contractions of the knee extensors and hip extensors. Three-dimensional running biomechanics were assessed overground at a self-selected speed. Running variables were the peak instantaneous vertical loading rate; peak forward trunk-lean angle; knee-flexion, internal-rotation, and -abduction angles and internal moments; and hip-extension, internal-rotation, and -adduction angles and internal moments. Separate stepwise linear regression models were used to examine the associations between strength and biomechanical outcomes (ΔR²) after accounting for sex, running speed, and foot-strike index.ResultsGreater 1RM back-squat strength was associated with a larger peak knee-flexion angle (ΔR² = 0.110, ΔP = .045) and smaller peak knee internal-rotation angle (ΔR² = 0.127, ΔP = .03) and internal-rotation moment (ΔR² = 0.129, ΔP = .03) after accounting for sex, speed, and foot-strike index. No associations were found between 1RM back-squat strength and vertical loading rate, trunk lean, or hip kinematics and kinetics. Hip- and knee-extensor maximal voluntary isometric contractions were also not associated with any biomechanical variables.ConclusionsGreater 1RM back-squat strength was weakly associated with a larger peak knee-flexion angle and smaller knee internal-rotation angle and moment in collegiate distance runners. Runners who are weaker in the back-squat exercise may exhibit running biomechanics associated with the development of knee-related injuries.     

Stimulated and voluntary fatiguing contractions of quadriceps femoris similarly disturb postural control in the bipedal stance

The aim of this work was to compare the effects of fatigue of the quadriceps femoris after fatiguing voluntary contractions (VOL) and fatiguing neuromuscular electrical stimulation (ES) on bipedal postural control. Nineteen active male subjects (22.2 ± 1.7 years) completed these two fatiguing exercises. Isometric maximal voluntary contraction (MVC) and postural control were recorded using an ergometer and a force platform that registered the center of foot pressure (COP). We analyzed the COP surface, the mean COP velocity and the spectral power density given by the wavelet transform. Recordings were performed before (PRE condition) and after the completion of each fatiguing task (immediately POST condition, after a 5 min recovery POST 5 condition). In POST condition, the ES exercise affected MVC more than the VOL exercise. However, bipedal postural control was similarly deteriorated for both exercises. In POST 5 condition, for both fatiguing exercises, muscle strength and postural control did not recover their initial level. These results suggest that the postural control disturbance could not be distinguished for the two fatiguing exercises in the bipedal stance. In addition, the recovery speeds of postural control and muscle strength abilities did not differ for the ES exercise and the VOL exercise.     

Lower extremity mechanical work during stance phase of running partially explains interindividual variability of metabolic power

Recent attention given to the mechanical work of the lower extremity joints, the emerging importance of the stance phase of running, and the lack of consensus regarding the biomechanical correlates to economical running were primary justifications for this study. The purpose of this experiment was to identify the correlations between metabolic power and the positive and negative mechanical work at lower extremity joints during stance. Recreational runners (n = 16) ran on a treadmill at 3.35 m s⁻¹ for physiological measures and overground for biomechanical measures. Inverse dynamics were used to calculate net joint moments and powers at the ankle, knee, and hip. Joint powers were then integrated over the stance phase so that positive and negative joint mechanical work were correlated with metabolic power (r = 0.60–0.69). Positive work at the hip and ankle during stance was positively correlated to metabolic power. In addition to these results, more economical runners (lower metabolic power) exhibited greater negative work at the hip, greater positive work at the knee, and less negative work at the ankle. Between the most and least economical runners, different mechanical strategies were present at the hip and knee, whereas the kinetics of the ankle joint differed only in magnitude.     

Reproducibility of isokinetic leg strength and endurance characteristics of adult men and women

Summary Day-to-day variability and single-measurement reliability of selected isokinetic knee extension-flexion strength and endurance indices were assessed in 10 adult men and 8 adult women. On three occasions separated by at least 5 days, the subjects completed 4 reciprocal maximal voluntary contractions (MVC) at different angular velocities (1.05 rad · s^–1 and 3.14 rad · s^–1). The men also completed a muscular endurance test consisting of 30 reciprocal, MVC at 3.14 rad ·^–1. Coefficient of variation, intra-class correlation coefficient and standard error of single-measurement scores support the continued use of gravity corrected peak torque (PT) and average peak torque (APT) as indices of isokinetic leg strength. Similarly, gravity corrected APT and total work should be the recommended indices of isokinetic leg muscular endurance in men. The results suggest that these isokinetic indices must be assessed using multiple day-to-day trial protocols adequately to describe performance capacity. Composite indices such as the ratio of Knee flexion to extension PT and fatigue measurements offer considerably reduced reliability and a greater potential for misinterpretation. The reliability of knee extension indices generally exceeds that of flexion indices. Similar variability and reproducibility of responses were observed between men and women and between reciprocal contractions performed at angular velocities of 1.05 rad · s^–1 and 3.14 rad · s^–1.     

Phase-dependent inhibition of H-reflexes during walking in humans is independent of reduction in knee angular velocity.

The purpose of this investigation was to investigate whether reduction in impulses arising from stretch of the quadriceps by restricting rapid knee flexion in early swing would affect inhibition of the H-reflex during swing. The contribution of afferent input arising from knee angular velocity to phase-dependent modulation of short-latency responses in the soleus was studied by simultaneously measuring joint velocity and soleus H-reflex responses at midstance and midswing phases of treadmill walking in 15 normal subjects. Stimulus strength was varied so that both maximal M and H waves were identified in each subject at midswing and midstance with the knee unrestricted (UK) and with knee movement restricted (RK), using a full leg bivalved cast to immobilize the knee joint. All subjects exhibited short-latency reflex responses in the soleus muscle. The H/M ratio at midswing was significantly reduced compared with midstance under both UK and RK walking conditions (P < 0.0001). When compared with UK walking, knee joint angular velocity during RK walking was significantly reduced at midswing (P < 0.001) and midstance (P < 0.005) compared with UK. There were, however, no significant differences in H/M ratios at midswing and midstance between UK and RK walking tests. Inhibition of the H-reflex in the soleus muscle during swing was not affected by significant reduction in knee angular velocity. These results indicate that the sensory input from changes in angular velocity at the knee does not lay the inhibitory foundation of phase-related reflex modulation in the ankle extensors during walking as suggested by Brooke and colleagues.     

Mean power frequency and amplitude of the mechanomyographic signal during maximal eccentric isokinetic muscle actions

The purpose of the present investigation was to examine the effects of knee angular velocity on the mean power frequency (MPF) and amplitude of the mechanomyographic (MMG) signal during maximal eccentric (ECC) isokinetic muscle actions. Eleven adult subjects performed maximal ECC muscle actions of the leg extensors on a calibrated Cybex 6000 dynamometer at knee angular velocities of 60, 120, and 180 degrees.s-1. MMG was detected by a piezoelectric crystal contact sensor placed over the vastus lateralis muscle. There were no significant (p > 0.05) velocity-related changes in ECC peak torque (PT) or MMG MPF, however, the mean MMG amplitude value at 60 degrees.s-1 was significantly less (p < 0.05) than that at 180 degrees.s-1. These results did not support our previous hypothesis that the velocity-related increase in MMG amplitude for maximal ECC isokinetic muscle actions was due to selective recruitment of fast twitch fibers and derecruitment of slow twitch fibers with increasing velocity.     

Energy cost of running during a specific transition in duathlon]

The aim of the present study was to investigate the variability of the energy cost of running (Cr) during a simulated duathlon performed in outdoor conditions by elite duathletes. This duathlon consisted of 5 km of running, 30 km of cycling, and 5 km of running. The main result was the lack of significant difference in Cr between the two running bouts (210 +/- 10 mL d'O2.km-1.kg-1 vs. 217 +/- 10 mL d'O2.km-1.kg-1). This result is different from those observed during a triathlon, where an increase of energy cost of running bout has been reported. Furthermore, during a short-distance duathlon performed by well-trained subjects, none of the physiological (ventilation alteration, metabolic changes, or dehydration) or biomechanical factors that are classically evoked in triathlon research to explain Cr variability seem to be affected by the run-cycle-run transition. These results seem to minimize the negative effect of the cycle-to-run transition during a short-duration event in well-trained subjects.     

Electromyogram patterns during plantarflexions at various angular velocities and knee angles in human triceps surae muscles

To investigate the influence of the various knee angles and ankle angular velocities on synergistic muscle activities, the surface electromyograms (EMG) were recorded from the triceps surae muscles, i.e. lateral gastrocnemius (LG), medial gastrocnemius (MG) and soleus (SOL) muscles. Six healthy young men performed ankle plantarflexions at three ankle angular velocities of 6, 30 and 60°?·?s^?1 and three knee angles of 0, 30 and 60° (0° equalling full extension) under constant load (5% and 10% maximal voluntary contraction). At the fully-extended knee angle (0°), peak values of integrated EMG (peak iEMG) during ankle plantarflexions were significantly increased (P?P??1) the peak iEMG were significantly increased (P?P?相似文献   

Differences in physical fitness among indoor and outdoor elite male soccer players

This study compared anthropometric (body height, body mass, percent body fat, fat-free body mass) and physical fitness characteristics (vertical jump height, power-load curve of the leg, 5 and 15 m sprint running time and blood lactate concentrations ([La]_b) at submaximal running velocities) among 15 elite male indoor soccer (IS) and 25 elite male outdoor soccer (OS) players. IS players had similar values in body height, body mass, fat-free body mass and endurance running than OS players. However, the IS group showed higher (P < 0.05–0.01) values in percent body fat (28%) and sprint running time (2%) but lower values in vertical jump (15%) and half-squat power (20%) than the OS group. Significant negative correlations (P < 0.05–0.01) were observed between maximal sprint running time, power production during half-squat actions, as well as [La]_b at submaximal running velocities. Percent body fat correlated positively with maximal sprint time and [La]_b, but correlated negatively with vertical jump height. The present results show that compared to elite OS players, elite IS players present clearly lower physical fitness (lower maximal leg extension power production) characteristics associated with higher values of percent body fat. This should give IS players a disadvantage during soccer game actions.     

Neuromuscular control adaptations in elite athletes: the case of top level karateka

This paper aimed at investigating the neuromuscular response of knee flexor and extensor muscles in elite karateka and karate amateurs (Amateurs) during isokinetic knee flexion/extensions and during the execution of a front kick (FK). Surface electromyograms (sEMG) were recorded from the right vastus lateralis (VL) and biceps femoris (BF) muscles with a four-array electrode during maximal isometric knee flexion and extension (maximal voluntary contraction), during isokinetic contractions (30°, 90°, 180°, 270°, 340°, 400°/s), and during the FK. The level of VL and BF agonist (ago) and antagonist (ant) activation during the isokinetic and FK protocols was quantified through normalized sEMG root mean square value (%RMS_{ago/ant-ISOK/FK}). VL and BF average muscle fiber conduction velocity (CV) was computed for isokinetic and FK. Isokinetic flexion and extension torques and knee angular velocity during FK were also assessed. Analysis of variance was used to test the effect of group, angular velocity, and task on the assessed variables (P < 0.05). Elite karateka showed higher isokinetic knee flexion torque when compared with Amateurs. For all angular velocities, VL and BF %RMS_{ant-isokinetic} were lower in elite karateka, while their BF-CV_isokinetic BF-CV_{front kick} and BF %RMS_{ant-front kick} values were higher. For VL and BF, %RMS_{ago-front kick} was lower than %RMS_{ago-isokinetic} in both groups. Elite karateka demonstrated a typical neuromuscular activation strategy that seems task and skill level dependent. Knee flexion torque and CV results suggest the presence of an improved ability of elite karateka to recruit fast MUs as a part of training induced neuromuscular adaptation.     

Motor performance changes induced by muscle vibration

The possibility that mechanical stimulation of selected muscles can act directly on the nervous system inducing persistent changes of motor performances was explored. On the basis of literature, stimulating parameters were chosen to stimulate the central nervous system and to avoid muscle fibre injuries. A sinusoidal mechanical vibration was applied, for three consecutive days, on the quadriceps muscle in seven subjects that performed a muscular contraction (VC). The same stimulation paradigm was applied on seven subjects in relaxed muscle condition (VR) and seven subjects were not treated at all (NV). Two sessions (PRE and POST) of isometric and isotonic tests were performed separated for 21 days, in all studied groups 7 days before and 15 days after stimulation, whilst an isokinetic test was performed on VC only. In the isometric test, the time of force development showed a significant decrease only in VC (POST vs PRE mean 27.8%, P < 0.05). In the isotonic test, the subjects’ had to perform a fatiguing leg extension against a load. In this condition, the fatigue resistance increased greatly in VC (mean 40.3%, P < 0.001), increased slightly in VR and there was no difference in NV. In Isokinetic test, at several angular velocities, significantly less time was required to reach the force peak (mean 20.2% P < 0.05). The findings could be ascribed to plastic changes in proprioceptive processing, leading to an improvement in knee joint control. Such action delineates a new tool in sports training and in motor rehabilitation.