***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: The purpose of this study was to assess net corticomotor excitability during a painful stimulus before and after exercise . In the first study , 25 subjects participated in three sessions : one familiarization session and two experimental sessions . The two experimental sessions were r and omized and involved measurement of pain perception before and after ( 1 ) a submaximal isometric fatiguing contraction with the left elbow flexor muscles and ( 2 ) 30 min of quiet rest .  Pain perception was assessed using a  pressure device applied to the right index finger for 2 min . Motor evoked potentials ( MEPs ) of the left brachioradialis muscle were measured following transcranial magnetic stimulation ( TMS ) which was delivered before , during , and after the 2 min pain test . In the second study , 12 subjects participated in one session which involved application of TMS to elicit MEPs at the same time points as in study one , before and after a submaximal fatiguing contraction , but in the absence of pain . In the absence of the mechanical noxious stimulus , MEP amplitude was reduced following the fatiguing contraction and unchanged over this time period . In study one , pain threshold increased and pain ratings decreased following the isometric contraction but not after 30 min of quiet rest . During application of the mechanical noxious stimulus to the right index finger , MEP amplitude of the left brachioradialis muscle increased indicating an increase in net corticomotor excitability . The pain-induced increase in MEPs was attenuated following the isometric fatiguing contraction and this occurred in parallel with the decrease in pain The nociceptive flexion reflex ( RIII reflex ) and the concurrent subjective pain score elicited by right sural nerve stimulation at r and om intensities were studied in 10 healthy volunteers . A close relationship was found between the recruitment curves of the reflex and the pain score as a function of stimulus intensity . As a consequence , the threshold of the RIII reflex ( Tr ) and of pain sensation ( Tp ) were found to be almost identical ( mean : 9.8 and 11.3 mA , respectively ) . Similarly , the threshold for obtaining a maximal reflex response ( Tmr ) was found to be very close to that for intolerable pain ( Tip ) : 33.5 and 35.1 mA , respectively . These four parameters were studied before and during the immersion of the left h and into a heated thermoregulated waterbath at various temperatures ( from 40 to 47.5 degrees C ) . While nonnociceptive temperatures ( 40 to 44 degrees C ) were without effect , higher conditioning temperatures induced an increase in the four thresholds . In addition , a highly significant linear relationship was observed between the increase in these thresholds and the intensity of the conditioning stimulus in the 44 to 47.5 degrees C range . These four parameters were also studied before and during three other nociceptive conditioning stimuli : immersion of the left h and into a 6 degrees C waterbath , 10 watts muscular exercise of the left h and performed under ischaemia and a painful ( 5.5 kg/cm2 ) pinch applied on the nasal septum . These three conditioning situations induced a very significant increase of the four thresholds considered in this study with the greatest being observed during nociceptive cold applied to the left h and . During all the conditioning situations , variations in Tr and Tp as well as in Tmr and Tip were found to be linearly related . This indicates a close relationship between the effects of the conditioning nociceptive stimuli on the reflex and the related pain sensation . These results suggest that the modulation of pain by heterotopic nociceptive stimuli can be explained at least in part by a depression in the transmission of nociceptive messages at the spinal level . They are discussed with reference to the counterirritation phenomena and common features with ' diffuse noxious inhibitory controls ' ( DNIC ) are underlined The aim of this present study is to test the hypothesis that nociceptive stimulation of latent myofascial trigger points ( MTrPs ) increases the occurrence of local muscle cramps . Nociceptive muscle stimulation was obtained by a bolus injection of glutamate ( 0.1 ml , 0.5 M ) into a latent MTrP and a control point ( a non-MTrP ) located in the right or left gastrocnemius medialis muscles in 14 healthy subjects . A bolus of isotonic saline ( 0.9 % , 0.1 ml ) injection served as a control . The injections were guided by intramuscular electromyography ( EMG ) showing resting spontaneous electrical activity at a latent MTrP and no such activity at a non-MTrP. Intramuscular and surface EMG activities in the gastrocnemius medialis muscle were recorded pre- , during- , and post-injection for a period of 8 min to monitor the occurrence of muscle cramps , which are characterized by a brief episodic burst of high levels of EMG activity . The results showed that glutamate and isotonic saline injections into the latent MTrPs induced higher peak pain intensity than into the non-MTrPs ( both P < 0.05 ) . Glutamate injection induced higher peak pain intensity than isotonic saline injection into either latent MTrPs or non-MTrPs ( both P < 0.05 ) . Muscle camps were observed in 92.86 % of the subjects following glutamate injection into the latent MTrPs , but not into the non-MTrPs ( P < 0.001 ) . No muscle cramps were recorded following isotonic saline injection into either the latent MTrPs or the non-MTrPs . These results suggest that latent MTrPs could be involved in the genesis of muscle cramps . Focal increase in nociceptive sensitivity at MTrPs constitutes one of the mechanisms underlying muscle cramps UNLABELLED We tested whether cortical activation anticipating painful stimuli is reduced more by integrative processes on somatosensory painful and motor information relative to the same h and than when that information refers to different h and s. In 3 conditions , visual warning stimuli were followed by visual target stimuli associated with an electrical painful stimulation at left index finger . In the Pain ( control ) condition , no task was required after the target stimuli . In the " Pain + ipsilateral movement " condition , the subjects had to perform a movement of the left index finger . In the " Pain + contralateral movement " condition , they had to perform a movement of the right index finger . Meanwhile ,  electroencephalographic data  were recorded  ( n = 18 ) from 128 scalp electrodes . Off line , these data were spatially enhanced by surface Laplacian transformation . Sensorimotor cortical activation before the painful stimulation was probed by the percentage power reduction of alpha rhythms at approximately 8 to 12 Hz ( event-related desynchronization , ERD ) . Results showed that the subjects perceived a lower stimulus intensity in both " Pain + ipsilateral " and " Pain + contralateral " conditions compared with the control " Pain " condition . Furthermore , wide anticipatory alpha ERD ( approximately 10 - 12 Hz ) was lower in amplitude in the " Pain + ipsilateral " than in the " Pain + contralateral " condition . These results suggest that modulation of alpha rhythms is a putative physiological mechanism underlying anticipatory processes preceding the integration of painful and motor information at cortical level . Furthermore , these processes show a marked interference ( " gating " ) when the sensorimotor integration refer to the same h and as opposed to both h and s. PERSPECTIVE We showed that cortical alpha rhythms preceding painful stimulation are influenced by the preparation of contralateral and ipsilateral finger movements . These results motivate further investigation for testing the hypothesis that chronic pain patients might exaggerate the anticipatory activation of sensorimotor cortex to negligible pain stimuli These experiments are concerned with the ability of human subjects to match isometric torque in their elbow flexor muscles when biceps of one arm is made sore . Pain was induced by injection of hypertonic saline . Subjects were asked to generate a level of torque , 30 % of maximum , with one arm , the reference arm . To achieve the required torque , subjects were given visual feedback . Subjects were then asked to match this torque with their other arm , the indicator arm . In control measurements , subjects were consistent in their matching ability and often were quite accurate . However , when biceps of one arm was made sore , subjects consistently and significantly underestimated the level of torque being generated by the sore arm . Painful heat applied to the skin over biceps produced a similar pattern of errors . Heating skin remote from elbow flexors had no significant effect . One interpretation of these findings is that the nociceptive input from the sore region of skin or muscle leads to reduced excitability of the motor cortex . That , in turn , disturbs the relationship between the central ly generated effort and motor output , leading to matching errors Objective : The purpose of this study was to investigate whether the knee joint dynamics during a forward lunge could be modulated by experimentally induced vastus medialis pain in healthy subjects . Design : R and omised cross-over study . Setting : Biomechanical movement laboratory . Participants : 20 healthy subjects were included . One subject was excluded during data collection . Intervention : The subjects performed forward lunges before , during and 20 minutes after induction of experimental quadriceps muscle pain . Muscle pain was induced using hypertonic saline ( 5.8 % ) injected intramuscularly . Isotonic saline ( 0.9 % ) was used as control . Main outcome measurements : Three-dimensional movement analyses were performed and inverse dynamics were used to calculate joint kinematics and kinetics for ankle , knee and hip joints . Electromyographic ( EMG ) signals of the hamstrings and quadriceps muscles were recorded . Results : During and after pain , significant decreases in knee joint dynamics and EMG recordings were observed . Conclusion : The study shows that local pain in the quadriceps is capable of modulating movements with high knee joint dynamics . The results may have implication s in the management of muscle pain and prevention of injuries during activities involving the knee joint The aim of this human study was to investigate the relationship between experimentally induced  muscle pain intensity ( i.e. , amount of nociceptive activity ) and motor unit ( MU ) firing decrease and MU conduction velocity ( CV ) . In 12 healthy subjects , nociceptive afferents were stimulated in the right tibialis anterior muscle by three intramuscular injections of hypertonic saline ( 0.2 , 0.5 , and 0.9 ml ) separated by 140 s. The subjects performed six isometric contractions ( 20 s long ) at 10 % of the maximal voluntary contraction during the experimental muscle pain . The same set of six contractions was performed without any infusion before the painful condition on the right leg . The procedure was repeated for the left leg with infusion of isotonic ( nonpainful ) saline .  Intramuscular and surface electromyographic ( EMG ) signals were collected to assess MU firing rate and CV . The firing rate of the active MUs [ range : 7.4 - 14.8 pulses/s ( pps ) ] did not change significantly in the three control conditions ( without infusion for the right and left leg and with infusion of isotonic saline in the left leg ) . There was , on the contrary , a significant decrease ( on average , mean + /- SE , 1.03 + /- 0.21 pps ) of the firing rates during the painful condition . Moreover , MU firing rates were inversely significantly correlated with the subjective scores of pain intensity . Single MU CV was 3.88 + /- 0.03 m/s ( mean + /- SE , over all the MUs ) with no statistical difference among any condition , i.e. , the injection of hypertonic saline did not alter the muscle fiber membrane properties of the observed MUs . Progressively increased muscle pain intensity causes a gradual decrease of MU firing rates . This decrease is not associated with a change in MU membrane properties , indirectly assessed by CV . This study demonstrates a central inhibitory motor control mechanism with an efficacy correlated to the nociceptive activity In this study we investigated the role of proprioception in the control of  prehension movements  , with particular reference to the grasp component . Grasp and transport kinematics were studied in a peripherally deafferented patient and in five healthy subjects . Two experiments were carried out : the prehension experiment and the grasp perturbation experiment . In the prehension experiment both the patient and the control subjects were required to reach and grasp three objects of different size , located at three different distances , both with and without visual feedback . In the grasp perturbation experiment a mechanical perturbation was applied to the fingers during prehension movements , again executed with and without visual feedback . In the prehension experiment  temporal parameters of the patient 's movements were generally slowed , with greater variability on some measures . However , over the first phase of the movement the pattern of the patient 's h and opening and transport acceleration , scaled to object size and distance , was the same as that of controls , both with and without visual feedback . On the contrary , during the final phase of the movement ( the finger closure phase and deceleration ) the patient 's performance differed significantly from the controls . These phases were abnormally lengthened and frequent movement adjustments were observed . In the grasp perturbation experiment the patient was not able to compensate for the perturbations applied to the fingers , even with visual feedback . The data allowed us to investigate also the respective contribution of proprioception and of vision of the h and in the control of prehension . We compared  prehension kinematics in two conditions : ( a ) with visual but no proprioceptive feedback ( in the patient ) and ( b ) with proprioceptive but no visual feedback ( in the controls ) . In both experiments proprioceptive control was more efficient than visual control . The results of this study are interpreted in favour of the strict dependence of prehension control on proprioception . The first phase of the movement , however , can be appropriately planned and executed without the necessity of either proprioceptive or visual information about the h and The aim of this human study was to investigate the effect of experimentally induced muscle pain on the modifications of motor unit discharge rate during sustained , constant-force contractions . Intramuscular and multichannel surface electromyographic ( EMG ) signals were collected from the right and left tibialis anterior muscle of 11 
    Output:
    
Despite the influence of pain on muscle activation , only subtle alterations were found in movement kinetics and kinematics .
The performance of various motor tasks mostly remained unimpaired , presumably as a result of a redistribution of muscle activity , both within the ( painful ) agonist and among muscles involved in the task .
At the most basic level of motor control , cutaneous pain caused amplification of the nociceptive withdrawal reflex , whereas insufficient evidence was found for systematic modulation of other spinal reflexes .
At higher levels of motor control , pain was associated with decreased corticospinal excitability .
Collectively , the findings show that short-lasting experimentally induced limb pain may induce immediate changes at all levels of motor control , irrespective of the source of pain .