***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: OBJECTIVE To investigate whether electrical stimulation is effective in improving quadriceps strength in healthy subjects and to compare interferential and low-frequency current in terms of the effects on quadriceps strength and perceived discomfort . DESIGN R and omized , controlled study . SETTING Physical Medicine and Rehabilitation Department in a university hospital . SUBJECTS Thirty medical faculty students , divided into three groups , participated in the study . INTERVENTIONS Group A received electrical stimulation with bipolar interferential current while group B received electrical stimulation with low-frequency current ( symmetrical biphasic ) . Group C served as the control group . Electrical stimulation was given for 15 minutes , five days a week for three weeks , at a maximally tolerated intensity with the knee fully extended in the sitting position . MAIN OUTCOME MEASURES Before and after the study , quadriceps strength was measured with a Cybex dynamometer isokinetically at the angular velocities of 60 degrees/s and 120 degrees/s . The perceived discomfort experienced with each type of electrical stimulation was quantified by the use of a visual analogue scale ( VAS ) . RESULTS Statistically significant increase in isokinetic strength was observed after training in group A and group B. Increase in strength did not differ between the stimulation groups . No significant change in strength occurred in group C. Perceived discomfort by the stimulation groups was not significantly different . CONCLUSION Both interferential and low-frequency currents can be used in strength training with the parameters used in this study Cross-education enhances the performance of muscles not directly involved in the chronic conditioning of the muscles in a remote limb . Substantial cross-education occurs after training with eccentric contractions or with contractions evoked by electromyostimulation ( EMS ) . Since during EMS and eccentric contractions , skin and muscle afferents are activated that have excitatory effects on contralateral homologous muscles , it was hypothesized that exercise training with stimulated vs. voluntary eccentric contractions would lead to greater cross-education . Thirty-two women were r and omly assigned to a  voluntary ( Vol ) , an EMS , or remote EMS ( rEMS ) exercise group  and performed 840 voluntary or stimulated eccentric contractions over 6 weeks . All subjects , including nonexercising controls ( Con ) , were tested pre- and posttraining for maximal voluntary and stimulated isometric and eccentric quadriceps strength . Ipsilateral voluntary and stimulated forces increased in all groups . Changes in EMG activity paralleled those in voluntary force in each limb . No changes occurred in grip strength . The great contra- and ipsilateral strength gains after EMS training were most likely related to an additive effect of EMS and muscle lengthening INTRODUCTION A variety of techniques have been used with variable success in an attempt to reverse the loss of muscle strength , bulk , and endurance that occurs during spaceflight . This study was design ed to evaluate a new " hybrid " approach that uses the resistance provided by an electrically stimulated antagonist muscle to resist the volitional contraction of its agonist . METHODS There were 20 subjects who were r and omized into 3 groups that received either the new hybrid program ( HYB ) , isotonic weight training ( WT ) , or isometric electrical stimulation ( ES ) . Subjects trained 3 times per week for 8 wk with each session consisting of their non-dominant upper extremity performing 10 sets of 10 reciprocal 2-s elbow flexion and extension contractions separated by 1-min rest intervals . Elbow flexion\extension torques and biceps\triceps cross-sectional areas ( CSA ) were measured at the beginning , midpoint , and end of training as well as at follow-up 4 wk later . RESULTS The HYB group demonstrated statistically significant increases in elbow flexion and extension torques ( 56 % and 31 % , respectively ) at the end of training that were similar to or larger than the gains in the other groups with benefits that persisted at follow-up 4 wk later . Muscle CSA increases in the HYB group ( 10 % ) were comparable or larger than those in WT and ES subjects . CONCLUSIONS These results suggest that HYB training may be an effective way to maintain and increase muscle bulk and strength for patients during bed rest , as well as astronauts in space This study aim ed to compare voluntary and stimulated exercise for changes in muscle strength , growth hormone ( GH ) , blood lactate , and markers of muscle damage .  Nine healthy men had two leg press exercise bouts separated by 2 wk . In the first bout , the quadriceps muscles were stimulated by biphasic rectangular pulses ( 75 Hz , duration 400 mus , on-off ratio 6.25 - 20 s ) with current amplitude being consistently increased throughout 40 contractions at maximal tolerable level . In the second bout , 40 voluntary isometric contractions were performed at the same leg press force output as the first bout . Maximal voluntary isometric strength was measured before and after the bouts , and serum GH and blood lactate concentrations were measured before , during , and after exercise . Serum creatine kinase ( CK ) activity and muscle soreness were assessed before , immediately after , and 24 , 48 , and 72 h after exercise . Maximal voluntary strength decreased significantly ( P < 0.05 ) after both bouts , but the magnitude of the decrease was significantly ( P < 0.05 ) greater for the stimulated contractions ( -22 % ) compared with the voluntary contractions ( -9 % ) . Increases in serum GH and lactate concentrations were significantly ( P < 0.05 ) larger after the stimulation compared with the voluntary exercise . Increases in serum CK activity and muscle soreness were also significantly ( P < 0.05 ) greater for the stimulation than voluntary exercise . It was concluded that a single bout of electrical stimulation exercise result ed in greater GH response and muscle damage than voluntary exercise The effect of different training intensities of electro-motor stimulation ( EMS ) on strength gains produced in the quadriceps femoris muscle group was investigated . Twenty-four subjects were r and omly assigned to one of three groups : Control ( C ) , Low Intensity ( LI ) trained at 25 % of their maximum voluntary isometric contraction ( MVIC ) , and High Intensity ( HI ) trained at 50 % of MVIC . Results indicated a significant strength improvement in both training groups ( p<0.01 ) following a three-week EMS training program . The HI group showed significantly greater strength gains ( 48.5 % ) than the LI group ( 24.2 % ) ( p<0.01 ) . A significant carry-over effect was also demonstrated in a three-week follow-up period , specifically in the HI group . Positive isokinetic strength changes in the concentric mode were observed in both training groups . In addition , a significant cross transfer effect was demonstrated in the contralateral homologous muscle group ( p<0.01 ) for both HI and LI groups The effects of two methods of electrical stimulation on maximum isometric force , calf girth , and skinfold thickness of stimulated and nonstimulated ( contralateral ) legs were studied . Thirty-six male volunteers , divided into three groups , participated in the experiment . Groups I and II were subjected to the procedure of electrical stimulation of m. triceps surae daily for a period of 21 days . Group I was stimulated by an alternating current of low frequency ( 50 Hz ) ; group II was also stimulated by an alternating current but of higher frequency ( 2000 Hz ) . Group III served as control group . In groups I and II significant increases of the maximum isometric force ( as measured on an electronic dynamometer ) of the stimulated ( 50.3 % and 58.8 % ) and also of the nonstimulated ( contralateral ) muscles ( 39.7 % and 32.2 % ) were found . In group III no significant increase of the maximum isometric force was registered . After the period of stimulation , the skinfold thickness was notably reduced by 21.6 % in group II , and calf girth was enlarged in both experimental groups . Relatively large changes were realized in the calf girth and the skin-fold thickness of the nonstimulated legs . The changes in group III were insignificant . It is concluded that electrical stimulation with low as well as high frequencies exerts great effects on muscle force The present study assessed the effects of training using electrostimulation of muscle ( EMS ) on the torque-angular velocity and torque-angle relationships , and the cross-sectional area ( CSA ) of the triceps surae . Twelve physical education students , divided into two groups ( 6 controls , 6 experimental ) , participated in the experiment . The EMS sessions were undertaken using a ' Complex-type ' stimulator . Flexible elastomer electrodes were used . The current used discharged pulses lasting for 200 microseconds at a frequency of 70 Hz . The duration s of contraction and rest were 5 and 15 s , respectively . The session lasted for 10 min for each muscle . The training regimen was three sessions per week for 4 weeks . Biomechanical tests were performed with the Biodex ( Biodex Corporation , Shirley , NY , USA ) isokinetic ergometer . Plantar flexions of the ankle over a concentric range of voluntary contractions were performed at different angular velocities ( 1.05 , 2.10 , 3.14 , 4.20 , 5.23 and 6.28 rad s-1 ) and maximum voluntary isometric contractions were held for 5 s at several ankle flexion angles ( -30 degrees , -15 degrees , 0 degree and 15 degrees ; 0 degree corresponds to foot flexion of 90 degrees relative to the leg axis ) . The peak value of the torque was recorded . Morphological tests consisted of measuring the CSA of the triceps surae on the right leg , 15 cm below the tibial protuberance , by a computerized tomography technique . The torque-velocity relationship was seen to shift significantly upwards after EMS training . The increase in the isometric torque observed after EMS training was greater in dorsiflexion than in plantarflexion . ( ABSTRACT TRUNCATED AT 250 WORDS Neuromuscular electrical stimulation ( NMES ) may be used to prevent strength loss associated with post-surgical immobilization . Most studies testing the effectiveness of NMES have trained the knee extensors . The purpose of this investigation was to test the effectiveness of NMES when training the elbow flexors . Twenty-four students were r and omly assigned to one of three groups : NMES training , isometric training or control . Testing and training were completed using a Biodex ™ dynamometer . After a st and ard warm-up , subjects were positioned on the Biodex ™ with left shoulder in anatomical neutral , elbow flexed to 90(o ) and forearm supinated . Subjects performed three maximum isometric contractions of 5 seconds duration , with 1 min rest between repetitions . Average peak torque during three repetitions was calculated . Subjects trained on three days per week for four weeks . Training included 15 maximum contractions of 15 seconds duration with 45 seconds recovery between repetitions . Russian current was delivered by a Forte ™ 400 Combo via electrodes placed over ends of biceps brachii . A maximum tolerable ramped intensity was delivered with frequency of 90 bps and duty cycle of 15:45 . After training , subjects were post-tested in a manner identical to pretest . Mean normalized strength data were analyzed using a 3 ( Group ) x 2 ( Test ) ANOVA . The Group x Test interaction was significant . Post-hoc analyses revealed that the voluntary training group ( normalized means of 0.49 to 0.71 for the pretest and post-test , respectively ) had a significantly greater increase than the other two groups , which were not significantly different from each other . The lack of significant strength gains  with NMES was likely due to low average training intensity , which was only 20.4 % of MVIC . Based on these results , NMES training may not be an effective alternative to voluntary training in healthy subjects . Key PointsTraining the elbow flexors with voluntary isometric contractions produced significantly greater strength gains than did training with NMES.Strength gains when training with NMES were no greater than with no training . The lack of strength gains with NMES was likely due to a low average training torque of 20.4 % of MVIC PURPOSE The aim of this study was to examine the influence of a short-term electromyostimulation ( EMS ) training program on the strength of knee extensors , skating , and vertical jump performance of a group of ice hockey players . METHODS Seventeen ice hockey players participated in this study , with nine in the electrostimulated group ( ES ) and the remaining height as controls ( C ) . EMS sessions consisted of 30 contractions ( 4-s duration , 85 Hz ) and were carried out 3x wk for 3 wk . Isokinetic strength of the knee extensor muscles was determined with a Biodex dynamometer at different eccentric and concentric angular velocities ( angular velocities ranging from -120 to 300 degrees .s ) . Jumping ability was evaluated during squat jump ( SJ ) , countermovement jump ( CMJ ) , drop jump ( DJ ) , and 15 consecutive CMJ ( 15J ) . Sprint times for 10- and 30-m skates in specific conditions were measured using an infrared photoelectric system . RESULTS After 3 wk of EMS training , isokinetic torque increased significantly ( P<0.05 ) for ES group in eccentric ( -120 and -60 degrees .s ) and concentric conditions ( 60 and 300 degrees .s ) , whereas vertical jump height decreased significantly ( P<0.05 ) for SJ ( -2.9+/-2.4 cm ) , CMJ ( -2.1+/-2.0 cm ) , and DJ ( -1.3+/-1.1 cm ) . The 10-m skating performance was significantly improved ( from 2.18+/-0.20 to 2 
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To generate this level of MVC , it was possible to identify guidelines for effectively combining training regimens ( 4.4 ± 1.5 weeks , 3.2 ± 0.9 sessions per week , 17.7 ± 10.9 minutes per session , 6.0 ± 2.4 seconds per contraction with 20.3 ± 9.0 % duty cycle ) with relevant stimulation parameters ( impulse width 306.9 ± 105.1 microseconds , impulse frequency 76.4 ± 20.9 Hz , impulse intensity 63.7 ± 15.9 mA ) to optimize training for systematic ally developing strength abilities ( maximal strength , speed strength , jumping and sprinting ability , power )