***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: INTRODUCTION We used transcranial magnetic stimulation ( TMS ) to investigate 3 weeks of unilateral leg strength training on ipsilateral motor cortex ( iM1 ) excitability , and short-latency intracortical inhibition ( SICI ) . METHODS Right leg dominant participants ( n = 14 ) were r and omly divided into either a  strength training ( ST )  or  control group . The ST group completed 9 training sessions ( 4 sets of 6 to 8 repetitions of single right leg squats ) . RESULTS We observed a 41 % increase in right leg strength , and a 35 % increase in strength of the untrained left leg ( P < 0.01 ) . There was a significant increase in motor evoked potential ( MEP ) amplitude recruitment curve for the untrained left leg ( P < 0.01 ) . SICI of the iM1 decreased by 21 % for the untrained left leg ( P < 0.01 ) . CONCLUSIONS The findings provide evidence for corticomotor adaptation for unilateral leg strength training within the iM1 that is modulated by changes in interhemispheric inhibition Trapezius muscle Hoffman ( H ) reflexes were obtained to investigate the neural adaptations induced by a 5-wk strength training regimen , based solely on eccentric contractions of the shoulder muscles . Twenty-nine healthy subjects were r and omized into an eccentric training group ( n = 15 ) and a reference group ( n = 14 ) . The eccentric training program consisted of nine training sessions of eccentric exercise performed over a 5-wk period . H-reflex recruitment curves , the maximal M wave ( Mmax ) , maximal voluntary contraction ( MVC ) force , rate of force development ( RFD ) , and electromyographic ( EMG ) voluntary activity were recorded before and after training . H reflexes were recorded from the middle part of the trapezius muscle by electrical stimulation of the C3/4 cervical nerves ; Mmax was measured by electrical stimulation of the accessory nerve . Eccentric strength training result ed in significant increases in the maximal trapezius muscle H reflex ( Hmax ) ( 21.4 % [ 5.5 - 37.3 ] ; P = 0.01 ) , MVC force ( 26.4 % [ 15.0 - 37.7 ] ; P < 0.01 ) , and RFD ( 24.6 % [ 3.2 - 46.0 ] ; P = 0.025 ) , while no significant changes were observed in the reference group . Mmax remained unchanged in both groups . A significant positive correlation was found between the change in MVC force and the change in EMG voluntary activity in the training group ( r = 0.57 ; P = 0.03 ) . These results indicate that the net excitability of the trapezius muscle H-reflex pathway increased after 5 wk of eccentric training . This is the first study to investigate and document changes in the trapezius muscle H reflex following eccentric strength training Purpose To test whether long-term cortical adaptations occur bilaterally following  chronic unilateral training  with a simple motor task . Methods Participants ( n = 34 ) were r and omly allocated to a training or control groups . Only the former completed a 4-week maximal-intensity isometric training of the right first dorsal interosseus muscle through key pinching . Maximal strength was assessed bilaterally in four different movements progressively less similar to the training task : key , tip and tripod pinches , and h and grip . Transcranial magnetic stimulation was used to probe , in the left and right primary h and motor cortices , a number of st and ard tests of cortical excitability , including thresholds , intra-cortical inhibition and facilitation , transcallosal inhibition , and sensory-motor integration . Results Training increased strength in the trained h and , but only for the tasks specifically involving the trained muscle ( key + 8.5 % ; p < 0.0005 ; tip + 7.2 % ; p = 0.02 ) . However , the effect size was small and below the cutoff for meaningful change . H and grip and tripod pinch were instead unaffected . There was a similar improvement in strength in the untrained h and , i.e. , a cross-education effect ( key + 6.4 % ; p = 0.02 ; tip + 4.7 % ; p = 0.007 ) . Despite these changes in strength , no significant variation was observed in any of the neurophysiological parameters describing cortico-spinal and intra-cortical excitability , inter-hemispheric inhibition , and cortical sensory-motor integration . Conclusions A 4-week maximal-intensity unilateral training induced bilaterally spatial- and task-specific strength gains , which were not associated to direct or crossed cortical adaptations . The observed long-term stability of neurophysiological parameters might result from homeostatic plasticity phenomena , aim ed at restoring the physiological inter-hemispheric balance of neural activity levels perturbed by the exercise . Trial registration number Clinical Trials.gov identifier NCT02010398 This study employed longitudinal measures of evoked spinal reflex responses ( Hoffman reflex , V wave ) to investigate changes in the activation of muscle and to determine if there are " linked " neural adaptations in the motor pathway following isometric resistance training .  Twenty healthy , sedentary males were r and omly assigned to either the trained ( n = 10 ) or control group ( n = 10 ) . The training protocol consisted of 12 sessions of isometric resistance training of the plantar flexor muscles over a 4-wk period . All subjects were tested prior to and after the 4-wk period . To estimate changes in spinal excitability , soleus Hoffman ( H ) reflex and M wave recruitment curves were produced at rest and during submaximal contractions . Recruitment curves were analyzed using the slope method ( Hslp/Mslp ) . Modulation of efferent neural drive was assessed through evoked V wave responses ( V/Mmax ) at 50 , 75 , and 100 % maximal voluntary contraction ( MVC ) . After 4 weeks , MVC torque increased 20.0 + /- 13.9 % ( mean + /- SD ) in the trained group . The increase in MVC was accompanied by significant increases in the rate of torque development ( 42.5 + /- 13.3 % ) , the soleus surface electromyogram ( 60.7 + /- 30.8 % ) , voluntary activation ( 2.8 + /- 0.1 % ) , and the rate of activation ( 48.7 + /- 24.3 % ) . Hslp/Mslp was not altered by training ; however , V/Mmax increased 57.3 + /- 34.2 % during MVC . These results suggest that increases in MVC observed in the first few days of isometric resistance training can be accounted for by an increase in the rate of activation at the onset of muscle contraction . Augmentation of muscle activation may be due to increased volitional drive from supraspinal centers The purpose of this study was to examine the effects of a 5-wk unilateral , isometric strength-training program on plasticity in the spinal Hoffmann ( H- ) reflex in both the trained and untrained legs . Sixteen participants , 22 - 42 yr old , were assigned to either a control ( n = 6 ) or an exercise group ( n = 10 ) . Both groups were tested for plantar flexion maximal voluntary isometric contractions ( MVIC ) and soleus H-reflex amplitude in both limbs , at the beginning and at the end of a 5-wk interval . Participants in the exercise group showed significantly increased MVIC in both legs after training ( P < 0.05 ) , whereas strength was unchanged in the control group for either leg . Subjects in the exercise group displayed increased ( P < 0.05 ) H-reflex amplitudes on the ascending limb of the recruitment curve ( at an equivalent M wave of 5 % of the maximal M wave , H(A ) ) only in the trained leg . Maximal H-reflex and M-wave remained unchanged with training . Increased amplitude of H(A ) in the trained limb concurrent with increased strength suggests that spinal mechanisms may underlie the changes in strength , possibly because of increased alpha-motoneuronal excitability or reduced presynaptic inhibition . Despite a similar increase in strength in the contralateral limb of the exercise group , H(A ) amplitude was unchanged . We conclude that the cross-education effect of strength training may be due to supraspinal to a greater extent than spinal mechanisms The purpose of this study was to investigate whether neural adaptations following functional multiple-joint leg press training can induce neural adaptations to the plantar flexor muscles in a single-joint contraction task . Subjects were r and omised to a maximal strength training ( MST ) ( n = 10 ) or a control group ( n = 9 ) . MST consisted of 24 sessions ( 8 weeks ) of 4 × 4 repetitions of horizontal leg press using maximal intended velocity in the concentric phase with the movement ending in a plantar flexion . Neural adaptations in the soleus and gastrocnemius medialis ( GM ) were assessed by surface electromyographic activity and V-waves during maximum voluntary isometric contraction ( MVIC ) , and also by H-reflexes in the soleus during rest and 20 % MVIC .  One repetition maximum leg press increased by 44 ± 14 % ( mean ± SD ; P < 0.01 ) . Plantar flexion MVIC increased by 20 ± 14 % ( P < 0.01 ) , accompanied by 13 ± 19 % ( P < 0.05 ) increase in soleus , but not GM surface electromyography . Soleus V/MSUP increased by 53 ± 66 % and in GM by 59 ± 64 % ( P < 0.05 ) . Normalised soleus H-reflexes remained unchanged by training . No changes occurred in the control group . These results suggest that leg press MST can induce neural adaptations in a single-joint plantar flexion MVIC task Effects of 6 mo of heavy-resistance training combined with explosive exercises on neural activation of the agonist and antagonist leg extensors , muscle cross-sectional area ( CSA ) of the quadriceps femoris , as well as maximal and explosive strength were examined in 10 middle-aged men ( M40 ; 42 + /- 2 yr ) , 11 middle-aged women ( W40 ; 39 + /- 3 yr ) , 11 elderly men ( M70 ; 72 + /- 3 yr ) and 10 elderly women ( W70 ; 67 + /- 3 yr ) .  Maximal and explosive strength remained unaltered during a 1-mo control period with no strength training . After the 6 mo of training , maximal isometric and dynamic leg-extension strength increased by 36 + /- 4 and 22 + /- 2 % ( P < 0 . 001 ) in M40 , by 36 + /- 3 and 21 + /- 3 % ( P < 0.001 ) in M70 , by 66 + /- 9 and 34 + /- 4 % ( P < 0.001 ) in W40 , and by 57 + /- 10 and 30 + /- 3 % ( P < 0.001 ) in W70 , respectively . All groups showed large increases ( P < 0.05 - 0.001 ) in the maximum integrated EMGs ( iEMGs ) of the agonist vastus lateralis and medialis . Significant ( P < 0.05 - 0.001 ) increases occurred in the maximal rate of isometric force production and in a squat jump that were accompanied with increased ( P < 0.05 - 0 . 01 ) iEMGs of the leg extensors . The iEMG of the antagonist biceps femoris muscle during the maximal isometric leg extension decreased in both M70 ( from 24 + /- 6 to 21 + /- 6 % ; P < 0.05 ) and in W70 ( from 31 + /- 9 to 24 + /- 4 % ; P < 0.05 ) to the same level as recorded for M40 and W40 . The CSA of the quadriceps femoris increased in M40 by 5 % ( P < 0.05 ) , in W40 by 9 % ( P < 0.01 ) , in W70 by 6 % ( P < 0.05 ) , and in M70 by 2 % ( not significant ) . Great training-induced gains in maximal and explosive strength in both middle-aged and elderly subjects were accompanied by large increases in the voluntary activation of the agonists , with significant reductions in the antagonist coactivation in the elderly subjects . Because the enlargements in the muscle CSAs in both middle-aged and elderly subjects were much smaller in magnitude , neural adaptations seem to play a greater role in explaining strength and power gains during the present strength-training protocol Voluntary activation of muscle is commonly quantified by comparison of the extra force added by motor nerve stimulation during a contraction [ superimposed twitch ( SIT ) ] with that produced at rest by the same stimulus ( resting twitch ) . An inability to achieve 100 % voluntary activation implies that failure to produce maximal force output from the muscle must have occurred at a site at or above the level of the motoneurons . We have used cortical stimulation to quantify voluntary activation . Here , incomplete activation implies a failure at or above the level of motor cortical output . With cortical stimulation , it is inappropriate to compare extra force evoked during a contraction with the twitch evoked in resting muscle because motor cortical and spinal cord excitability both increase with activity . However , an appropriate " resting twitch " can be estimated . We previously estimated its amplitude by extrapolation of the linear relation between SIT amplitude and voluntary torque calculated from 35 contractions of > 50 
    Output:
    
There are subtle neural adaptations following resistance-training involving both cortical and subcortical adaptations that act to increase motoneurone activation and likely contribute to the training-related increase in muscle strength