***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 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 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 2.07+/-0.09 s , before and after the 3-wk EMS period , respectively ; P<0.05 ) . CONCLUSION It was demonstrated that an EMS program of the knee extensors significantly enhanced isokinetic strength ( eccentric and for two concentric velocities ) and short skating performance of a group of ice hockey players PURPOSE The purpose of the study was to investigate the effect of 4 and 8 wk of electromyostimulation ( EMS ) training on both muscular and neural adaptations of the knee extensor muscles . METHODS Twenty males were divided into the electrostimulated group ( EG , N = 12 ) and the control group ( CG , N = 8) . The training program consisted of 32 sessions of isometric EMS over an 8-wk period . All subjects were tested at baseline ( B ) and retested after 4 ( WK4 ) and 8 ( WK8 ) wk of EMS training . The EMG activity and muscle activation obtained under maximal voluntary contractions ( MVC ) was used to assess neural adaptations . Torque and EMG responses obtained under electrically evoked contractions , muscle anatomical cross-sectional area ( ACSA ) , and vastus lateralis ( VL ) pennation angle , both measured by ultrasonography imaging , were examined to analyze muscular changes . RESULTS At WK8 , knee extensor MVC significantly increased by 27 % ( P < 0.001 ) and was accompanied by an increase in muscle activation ( + 6 % , P < 0.01 ) , quadriceps muscle ACSA ( + 6 % , P < 0.001 ) , and VL pennation angle ( + 14 % , P < 0.001 ) . A significant increase in normalized EMG activity of both VL and vastus medialis ( VM ) muscles ( + 69 and + 39 % , respectively , P < 0.001 ) but not of rectus femoris ( RF ) muscle was also found at WK8 . The ACSA of the VL , VM , and vastus intermedius muscles significantly increased at WK8 ( 5 - 8 % , P < 0.001 ) but not at WK4 , whereas no changes occurred in the RF muscle . CONCLUSION We concluded that the voluntary torque gains obtained after EMS training could be attributed to both muscular and neural adaptations . Both changes selectively involved the monoarticular vastii muscles The effectiveness of cutaneous electrical stimulation as a muscle-strengthening technique was evaluated by comparison with an isometric regime . Sixteen normal healthy subjects were r and omly assigned to either an electrical group or an isometric group . A pretest was given of maximum voluntary force in the quadriceps ( extensor ) muscles , measured with a cable tensiometer . Subjects then trained ( isometrically or by electrical stimulation ) four days per week for three weeks . Training by electrical stimulation was via a square-wave pulse ( 75 Hz and 0.1 ms ) with the voltage determined by subject tolerance for ten , 10-sec induced contractions ( with 50-sec rest intervals ) . Isometric training consisted of ten , 10-sec maximal contractions ( with 50-sec rest intervals ) at each session . Feedback of the generated force was st and ardised for both groups . Post-training measures were then administered using the same protocol as the pretest . Both groups demonstrated a marked improvement in quadriceps strength of 22 + /- 5.3 % for the electrical group and 25 + /- 6.9 % increase for the isometric group ( p less than 0.02 ) . The change in strength was apparently not dependent on the magnitude of the stimulating voltage ( 5 - 10 V ) nor on the tension induced . There was no significant difference in the strength gains achieved by the two regimes ( p greater than 0.05 ) . No pain , muscle lesions or other ill effects were observed with electrical stimulation . We conclude that cutaneous electrical stimulation is a viable strengthening technique . There are obvious practical applications of this technique to the rehabilitation of patients who are not able to maintain an effective voluntary contraction This study was design ed to determine the effects of pulse frequency ( 20pps , 45pps , 80pps ) on subjects ' voltage tolerance , delayed muscle soreness , and muscle strength gained following 6 weeks of electrical stimulation .  Thirty healthy men ( mean age = 22 years ) were r and omly assigned to three groups . Subjects in group 1 ( n = 10 ) , group 2 ( n = 10 ) , and group 3 ( n = 10 ) had their right quadriceps femoris muscles electrically stimulated with a high-voltage pulsed galvanic stimulator present at pulse frequencies of 20pps , 45pps , and 80pps , respectively . The left limb of each subject served as the control . For all the groups , the duty cycle of the stimulator 
    Output:
    
Untrained athletes were investigated for comparison purpose s. This scientific analysis revealed that EMS is effective for developing physical performance .
With regard to the level of fitness , the analysis shows that trained and elite athletes , despite their already high level of fitness , are able to significantly enhance their level of strength to same extent as is possible with untrained subjects .
The EMS offers a promising alternative to traditional strength training for enhancing the strength parameters and motor abilities described above .
Because of the clear-cut advantages in time management , especially when whole-body EMS is used , we can expect this method to see the increasing use in high-performance sports