Left Soleus Research Articles

Effect of passive stretching on the immobilized soleus muscle fiber morphology

The aim of the present study was to determine the effect of stretching applied every 3 days to the soleus muscle immobilized in the shortened position on muscle fiber morphology. Eighteen 16-week-old Wistar rats were used and divided into three groups of 6 animals each: a) the left soleus muscle was immobilized in the shortened position for 3 weeks; b) during immobilization, the soleus was stretched for 40 min every 3 days; c) the non-immobilized soleus was only stretched. Left and right soleus muscles were examined. One portion of the soleus was frozen for histology and muscle fiber area evaluation, while the other portion was used to identify the number and length of serial sarcomeres. Immobilized muscles (group A) showed a significant decrease in weight (44 +/- 6%), length (19 +/- 7%), serial sarcomere number (23 +/- 15%), and fiber area (37 +/- 31%) compared to the contralateral muscles (P < 0.05, paired Student t-test). The immobilized and stretched soleus (group B) showed a similar reduction but milder muscle fiber atrophy compared to the only immobilized group (22 +/- 40 vs 37 +/- 31%, respectively; P < 0.001, ANOVA test). Muscles submitted only to stretching (group C) significantly increased the length (5 +/- 2%), serial sarcomere number (4 +/- 4%), and fiber area (16 +/- 44%) compared to the contralateral muscles (P < 0.05, paired Student t-test). In conclusion, stretching applied every 3 days to immobilized muscles did not prevent the muscle shortening, but reduced muscle atrophy. Stretching sessions induced hypertrophic effects in the control muscles. These results support the use of muscle stretching in sports and rehabilitation.

Effect of one stretch a week applied to the immobilized soleus muscle on rat muscle fiber morphology.

We determined the effect of stretching applied once a week to the soleus muscle immobilized in the shortened position on muscle fiber morphology. Twenty-six male Wistar rats weighing 269 +/- 26 g were divided into three groups. Group I, the left soleus was immobilized in the shortened position for 3 weeks; group II, the soleus was immobilized in the shortened position and stretched once a week for 3 weeks; group III, the soleus was submitted only to stretching once a week for 3 weeks. The medial part of the soleus muscle was frozen for histology and muscle fiber area evaluation and the lateral part was used for the determination of number and length of serial sarcomeres. Soleus muscle submitted only to immobilization showed a reduction in weight (44 +/- 6%, P = 0.002), in serial sarcomere number (23 +/- 15%) and in cross-sectional area of the fibers (37 +/- 31%, P < 0.001) compared to the contralateral muscles. The muscle that was immobilized and stretched showed less muscle fiber atrophy than the muscles only immobilized (P < 0.05). Surprisingly, in the muscles submitted only to stretching, fiber area was decreased compared to the contralateral muscle (2548 +/- 659 vs 2961 +/- 806 microm(2), respectively, P < 0.05). In conclusion, stretching applied once a week for 40 min to the soleus muscle immobilized in the shortened position was not sufficient to prevent the reduction of muscle weight and of serial sarcomere number, but provided significant protection against muscle fiber atrophy. In contrast, stretching normal muscles once a week caused a reduction in muscle fiber area.

The late response in the soleus muscle evoked by transcranial magnetic stimulation at the foramen magnum level

In healthy subjects, we studied the late electromyographic response elicited by transcranial magnetic stimulation (TMS) applied at the level of the foramen magnum in the left soleus muscle in an upright and supine posture. The late response at the latency of approximately 40 ms was constantly elicited during both postures. It was elicited during planter flexion, but not dorsi flexion. Additionally, no response appeared in the relaxed muscle. Those behaviours are the same as that of the long-loop reflex (LLR). We believe that the late response may be a long-loop reflex.

Recovery of contractile and metabolic phenotypes in regenerating slow muscle after notexin-induced or crush injury.

The recovery of metabolic pathways after muscle damage has been poorly studied. We investigated the myosin heavy chain (MHC) isoform transitions and the recovery of citrate synthase (CS) activity, isoform distribution of lactate dehydrogenase (LDH) and creatine kinase (CK) in slow muscles after two types of injury. Muscle degeneration was induced in left soleus muscles of male Wistar rats by either notexin injection or crushing and the regenerative process was examined from 2 to 56 days after injury. Myosin transition occurred earlier after notexin than after crush injury. Fast-type IIx and more particularly type IIa MHC isoform disappeared by day 28 after notexin inoculation, while they were still detected long after in crushed muscles. A full recovery of both the CS activity and the specific activity of the H-LDH subunit was observed from day 42 in notexin-treated muscles, while values measured in crushed muscles remained significantly lower than in non-injured muscles (P < 0.05). The activity of the mitochondrial isoform of CK (mi-CK) was markedly affected by the type of injury (P < 0.001), and failed to reach normal levels after crush injury (P < 0.05). The results of this study show that the relatively rapid MHC transitions during regeneration contrasts with the slow recovery in the oxidative capacity. The recovery of the oxidative capacity remained incomplete after crush injury, a model of injury known to lead to disruption of the basal lamina and severe interruption of the vascular and nerve supply.

骨格筋再生過程における熱ショックタンパク質72の変化

This study investigated the time course of changes in heat shock protein (HSP) 72, muscle weight and cross-sectional area of muscle fibers after injection of bupivacaine (BPVC) into the soleus muscle. Adult male Wistar rats (n=36) were anesthetized by pentobarvital sodium and 0.5 ml of BPVC was injected into the left soleus muscle, whereas the contralateral right soleus muscle was served as the control. Bilateral soleus muscles were dissected at 1, 2, or 4 days or 1, 2, or 4 weeks after the injection. Muscle fibers were disrupted at days 1-2 after BPVC injection and regenerated fibers that have centrally located nuclei in cytoplasm appeared 4 days after the injection. The cross-sectional area of regenerated fibers gradually increased during 4 days-4 weeks after the injection. The soleus muscle weight decreased until 1 week after the injection, then gradually increased during 1-4 weeks of recovery. The content of HSP 72 was drastically decreased in the soleus muscle 1 day after BPVC injection (p<0.01), then gradually increased during 2 days-4 weeks of recovery, and returned to the control level at 4 weeks of recovery. A similar time course of change was observed for the cross-sectional area of the regenerating fibers and HSP 72 expression. These results suggest that the BPVC injection induces disruption of muscle fibers and degradation of HSP 72, however, regeneration of muscle fibers indicated by increases in cross-sectional area occurs with increases in HSP 72 content during 4 weeks of recovery period.

Differential Modification of Myosin Heavy Chain Expression by Tenotomy in Regenerating Fast and Slow Muscles of the Rat

We have examined the effect of tenotomy on the expression of myosin heavy chains (MyHC) in regenerating fast and slow skeletal muscles. Degeneration/regeneration of the left soleus and plantaris of Wistar male rats was induced by an injection into the muscle belly of a myotoxin (snake venom: Notechis scutatus scutatus). MyHC isoform content of regenerating plantaris and soleus muscles were studied 21 days after muscle injury using an electrophoretic technique. Tenotomy of the regenerating plantaris (mechanical underload) did not alter its MyHC expression (P > 0.05). In contrast, tenotomy of the regenerating soleus increased its relative levels of MyHC-2b (P < 0.05) and MyHC-2x/d (P < 0.01), and decreased its relative level of MyHC-1 (P < 0.01). Tenotomy of the synergistic gastrocnemius (overload) tended to decrease the relative level of MyHC-2b in regenerating plantaris (P < 0.07). The effect of tenotomy of the synergistic gastronecmius on the regenerating soleus was different: a decrease in the relative levels of MyHC-1 (P < 0.05) and an increase in the relative level of MyHC-neonatal (P < 0.01). In conclusion, and in contrast to a regenerating slow muscle, a change of mechanical loading by tenotomy did not seem to markedly alter the expression of mature MyHC phenotype in a fast regenerating muscle.

Respective Effects Of Anabolic/Androgenic Steroids And Physical Exercise On Isometric Contractile Properties Of Regenerating Skeletal Muscles In The Rat

We examined the respective effects of anabolic-androgenic steroids and physical exercise on the contractile properties of regenerating fast and slow hindlimb skeletal muscles. Degeneration/regeneration of the left extensor digitorum longus muscles (EDL) and soleus of young Wistar male rats was induced by a snake venom (Notechis scutatus scutatus) injection. During muscle regeneration, experimental rats were either treated with nandrolone (NAN, nortestosterone, im, 2 mg × kg –1 × week –1), or endurance exercised on a treadmill (EXE, 60 min × day –1, 10–40 m × min –1). Twenty-one days after injury, isometric contractile properties of regenerating muscles were studied in situ. Neither the nandrolone treatment nor the physical exercise program was able to change significantly muscle contraction parameters both in twitch and tetanus in both regenerating EDL and soleus (p > 0.05). However, we observed a greater peak twitch tension in NAN versus grouped control and EXE EDL (p < 0.01). In conclusion, endurance exercise program or anabolic-androgenic steroid (nortestosterone) treatment did not significantly improve isometric contractile properties of regenerating slow and fast muscles in the male young rats.

Nifedipine does not impede clenbuterol-stimulated muscle hypertrophy.

The mechanism(s) responsible for beta2-adrenergic receptor-mediated skeletal muscle and cardiac hypertrophy remains undefined. This study examined whether calcium influx through L-type calcium channels contributed to the development of cardiac and skeletal muscle (plantaris; gastrocnemius; soleus) hypertrophy during an 8-day treatment with the beta2-adrenergic receptor agonist clenbuterol. Concurrent blockade of L-type calcium channels with nifedipine did not reverse the hypertrophic action of clenbuterol. Moreover, nifedipine treatment alone resulted in both cardiac and soleus muscle hypertrophy (6% and 7%, respectively), and this effect was additive to the clenbuterol-mediated hypertrophy in the heart and soleus muscles. The hypertrophic effects of nifedipine were not associated with increases in total beta-adrenergic receptor density, nor did nifedipine reverse clenbuterol-mediated beta-adrenergic receptor downregulation in either the left ventricle or soleus muscle. Both nifedipine and clenbuterol-induced hypertrophy increased total protein content of the soleus and left ventricle, with no change in protein concentration. In conclusion, our results support the hypothesis that beta2-adrenergic receptor agonist-induced muscle hypertrophy is mediated by mechanisms other than calcium influx through L-type calcium channels.

Effects of anabolic/androgenic steroids on regenerating skeletal muscles in the rat.

We have examined the effect of male sexual hormones on the regeneration of skeletal muscles. Degeneration/regeneration of the left soleus and extensor digitorum longus muscles (EDL) of Wistar male rats was induced by an injection of snake venom (2 microg, Notechis scutatus scutatus). During the muscle regeneration (25 days), rats were treated with either oil (CON), nandrolone (NAN), NAN combined with exercise (NAN + EXE) or were castrated (CAS). Muscle growth and myosin heavy chain (MyHC) isoform content of regenerating muscles were studied. Castration altered the concentrations of MyHC in venom-treated EDL (P < 0.01) and soleus (P < 0.05). NAN increased the mass (P < 0.01) of regenerating soleus and decreased the relative amount of fast MyHC protein (% of total, P < 0.05). The effect of NAN + EXE on the fast MyHC proteins of venom-treated soleus was opposite (P < 0.05). NAN and NAN + EXE were without effect on the regenerating EDL (P > 0.05). In conclusion, it is possible that male sexual hormones play a role in the growth (synthesis of contractile proteins) of regenerating muscles in rat. In addition, contrary to NAN + EXE, NAN could be beneficial to soleus regeneration.

Myogenin, MyoD, and myosin expression after pharmacologically and surgically induced hypertrophy.

The relationship between myogenin or MyoD expression and hypertrophy of the rat soleus produced either by clenbuterol and 3,3', 5-triiodo-L-thyronine (CT) treatment or by surgical overload was examined. Mature female rats were subjected to surgical overload of the right soleus with the left soleus serving as a control. Another group received the same surgical treatment but were administered CT. Soleus muscles were harvested 4 wk after surgical overload and weighed. Myosin heavy chain isoforms were separated by using polyacrylamide gel electrophoresis while myogenin and MyoD expression were evaluated by Northern analysis. CT and functional overload increased soleus muscle weight. CT treatment induced the appearance of the fast type IIX myosin heavy chain isoform, depressed myogenin expression, and induced MyoD expression. However, functional overload did not alter myogenin or MyoD expression in CT-treated or non-CT-treated rats. Thus pharmacologically and surgically induced hypertrophy have differing effects on myogenin and MyoD expression, because their levels were associated with changes in myosin heavy chain composition (especially type IIX) rather than changes in muscle mass.

Structural adaptation to ischemia in skeletal muscle: effects of blockers of the renin-angiotensin system.

To investigate the effects of long-term treatment with blockers of the renin-angiotensin system on capillarization and growth of fibers in ischemic hind-limb muscles and in muscles under normal growth conditions. Ischemia was induced by partial ligation of the left common iliac artery. Ischemia resulted in a significant increase in capillary and fiber density in the soleus muscle, a significant decrease in mean fiber size and a decrease in muscle cross-sectional area after 4 weeks compared with the contralateral nonischemic muscle. Ischemia also significantly decreased the muscle: body weight ratio of the left soleus muscle. We observed no significant effect on total number of capillaries and capillary: fiber ratio, suggesting that ischemia did not result in an increase in capillarization in this muscle. Treatments with subhypotensive and with hypotensive doses of the angiotensin converting enzyme (ACE) inhibitor benazeprilat, the angiotensin (Ang) II AT1 antagonist valsartan, or the Ang II AT2 antagonist PD 123 319 for 4 weeks did not influence any of the above-described changes in the normal and ischemic muscles and treatment effects were also independent of the degree of reduction of blood pressure. Treatments with an ACE inhibitor and with Ang II receptor antagonists in dose ranges that moderately lower blood pressure do not influence vessel density and any of the other structural adaptations after hind-limb ischemia. Administrations of ACE inhibitors and Ang II AT1 antagonists may therefore be adequate and beneficial therapies under ischemic conditions, such as in the treatment of hypertension complicated by intermittent claudication, for which treatment must not increase ischemia.

Effect of increased physical activity on growth and differentiation of regenerating rat soleus muscle.

Our purpose was to determine the effect of physical exercise on growth and differentiation during regeneration of a slow-twitch muscle. Degeneration/regeneration of the left soleus muscles of Wistar female rats was induced by injection of a snake venom. Muscular differentiation was studied by monitoring the sequential expression of the various myosin heavy chain isoforms (MHCs). Rats were assigned to one of two groups: cage sedentary (n = 14) or exercised (n = 16). The exercise programme began 1-day post-injection and the rats ran 1 h/day on a motorized treadmill. Then, 9 and 25 days after venom treatment, the soleus MHC phenotype as determined by immunohistology, electrophoresis and immunoblotting, was studied. At 25 days the expression of MHCs by regenerating soleus was not changed by the increased level of physical activity (P > 0.05). Exercised and sedentary regenerating muscles contained similar numbers of type-I fibres (100% of total fibres), levels of MHC-1 (85.4 and 89.5% of total MHCs), MHC-2a and M/HC-2x/d and their fibres expressed MHC-1 (100% of total fibres) and MHC-2 (45-50%) in the same way. Moreover, the masses of regenerating and nonregenerating soleus were significantly increased by physical exercise (P < 0.02). At 9 days no effect of muscular exercise was found. In conclusion, endurance exercise did not alter differentiation of regenerating soleus. Moreover regenerating soleus can respond to increased physical activity by enhancing its mass in the same way as mature muscle.

Influence of simulated microgravity on the sympathetic response to exercise.

Rats exposed to simulated conditions of microgravity exhibit reductions in aerobic exercise capacity that may be due to an impaired ability of the sympathetic nervous system (SNS) to mediate an increase in cardiac output and to redistribute blood flow. The purpose of this study was to quantify the sympathetic response to exercise in rats after exposure to 14 days of simulated microgravity or control conditions. To achieve this aim, rats were exposed to 14 days of head-down suspension (HDS) or cage control (CC) conditions. On day 14, norepinephrine (NE) synthesis was blocked with alpha-methyl-p-tyrosine, and the rate of NE depletion after synthesis blockade was used to estimate SNS activity in the left ventricle, spleen, and soleus muscle during treadmill exercise at 75% of maximal oxygen uptake. When compared with CC rats, the sympathetic response to exercise in HDS rats was characterized by a lower rate of NE depletion in the left ventricle (-82%) and spleen (-42%). The rate of NE depletion in the soleus muscle was 47% higher. These differences could contribute to the decrement in aerobic capacity of HDS rats by impairing their ability to augment cardiac output and to redirect blood flow to actively contracting skeletal muscle during exercise.

Changes in the H-Reflex Amplitude Caused by Fluctuation of Stimulus Frequency.

We investigated the changes in the H-reflex amplitude at various stimulus frequencies, in order to identify the stable index in a relatively short period. 10 subjects volunteered for experiment. The H-reflex was obtained from the left soleus. The H wave was induced by 29 degrees of stimulus frequency: 10 degrees from 0.1 to 1.0 Hz with an increase of 0.1 Hz, and 19 degrees from 1.0 to 20.0 Hz with an increase of 1.0 Hz. The decrease in H wave amplitude tended to become greater with an increase in stimulus frequency. The frequency depression curve at stimulus frequencies from 1.0 to 20.0 Hz indicated a significant frequency depression (p<0.01) with an increase in stimulus frequency. Disinhibition of the H-reflex amplitude at stimulus frequencies from 4.0 to 8.0 Hz is a specific response, and the change rate of the H-reflex amplitude at the stimulus frequency of 6.0 Hz (62.9%) was almost the same as that of 1.0 Hz (62.5%). We found that repetitive evoked EMG using a stimulus frequency of approximately 5 Hz is a great value in examining the change in the H-reflex amplitude and has a good possibility of clinical application.

Changes in the H-Reflex of Soleus Induced by Voluntary Contraction of Grasping.

Abnormal muscle tone with a specific motor pattern is observed in the affected side of a hemiplegic patient, who receives motor stress on the unaffected side of the upper limb during therapeutic exercise. In order to clarify the relation between the intensity of motor stress on upper limbs and changes in muscle tonus of lower limbs, we examined the changes in the H-reflex of the bilateral soleus muscle induced by grasping with the left hand, using repetitive evoked electromyograms at a stimulus frequency of 5 Hz. Eight healthy male subjects volunteered for this experiment. Subjects grasped a sphygmomanometer cuff by the left hand at five degrees of load intensity, 0, 20, 40, 60 and 80% of maximum voluntary contraction, and 10 consecutive H waves were recorded from the bilateral soleus for each intensity. The H-reflex of the right soleus increased significantly (p<0.01) with increasing grasping strength of the left hand, but that of the left soleus showed hardly any change. Right hemisphere dominance in the left upper limbs concentrated on grasping with the left hand resulted in disinhibition of the left cerebral hemisphere. The H-reflex from the right soleus was consequently increased.

Changes in motor activity and biomechanics during balance recovery following cutaneous and muscular deafferentation

The effects of lower limb deafferentation were examined during execution of a balance recovery step following a forward fall induced by release of an initial inclined posture. The subjects were healthy control subjects and patients with a unilateral loss of the Achilles tendon reflex following S1 radiculitis. Deafferentation of healthy subjects was obtained by unilateral leg ischemia (four subjects) and by foot anesthesia (five subjects). The balance recovery step was characterized by the surface electromyographic (EMG) activity of right and left soleus and tibialis anterior muscles and the kinetics of the center of gravity and center of foot pressure. Experimentally induced and pathological deafferentation decreased the EMG activity of the ipsilateral soleus and lowered the vertical ground reaction force. The lower limb motor activity was more affected by loss of muscle proprioceptive afferents than by loss of plantar cutaneous afferents. Patients showed early and bilateral changes in soleus and tibialis activities, whichever side was affected. The step length of patients was also shorter than that of controls, but it remained similar before and after deafferentation in the healthy subjects. The results are discussed in terms of ipsilateral and crossed pathway connections and functional adaptive strategies.

Aging effects in skeletal muscle recovery after reinnervation.

To investigate the influence of age on the process of muscle recovery after nerve repair, the nerves of the right extensor digitorum longus (EDL) and the right soleus muscles of 63 2-month-old and 61 15-month-old rats, respectively, were transsected and resutured. At four, eight, 16, and 24 weeks after nerve repair, functional recovery of the muscle was assessed by electromyographic (EMG) recordings and isometric muscle contraction. Muscle weight, morphological, and morphometric studies were also done. At four and eight weeks after nerve repair the younger age groups showed higher rates of recovery compared with the control side (left EDL and soleus) (recovery rate (%) = operated/control x 100) than the older age groups, and the recovery rates of soleus (slow twitch muscle) in both age groups were higher than EDL (fast twitch muscle). However, the differences between the two age groups decreased at 16 and 24 weeks after nerve repair in both muscles. We therefore conclude that earlier differences were the effects of nerve regeneration on the muscle between different ages and the reason for the reduced differences at later stages was that after reinnervation began, not only the nerve but also the muscle recovered successfully in older age groups, and slow motor units reinnervated faster than the fast units in both age groups. Our present study shows that the older age groups also have a good prognosis for recovery of muscle function after nerve repair.

Effect of retroauricular galvanic stimulation on muscle atrophy in the unweighted rat hindlimb

Hindlimb unweighting in the rat may serve as an experimental model simulating muscle atrophy under weightlessness. As a preventive measure, retroauricular galvanic stimulation was delivered to the unweighted rat hindlimb and the weights of the bilateral soleus and gastrocnemius muscles were compared. Wistar rats, with unweighted hindlimbs, were divided into two groups; the control group which received no galvanic stimulation and a galvanically stimulated group which received galvanic stimulation (bipolar biauricular, 1 mA in intensity, 500 msec in duration, 1 Hz in frequency) for one hour twice a day for 7 days using an electronic stimulator made by NIHON-KODEN (MODEL SEN-1101). The weights of the soleus and gastrocnemius muscles on both sides were measured in each group using a balance (METTLER AT201). The results were as follows: 1. Muscle weights in the galvanically stimulated group were greater than those in the control group. 2. A statistically significant difference between right and left soleus muscle weights was obtained in the galvanically stimulated group (P < 0.01). 3. We found no significant difference between the two sides in the weights of gastrocnemius muscles. It is presumed that retroauricular galvanic stimulation exerts some influence, not only on vestibular organs, but also on hindlimb muscles through the lateral vestibulo-spinal tract and, in addition, through the spinal motor neuron. Therefore, we speculate that galvanic stimulation might prevent atrophy of the unweighted hindlimb muscle.

Tissue-specific noradrenergic activity during acute heat stress in rats

The purpose of this study was to determine whether nonexertional heat stress alters the behavior of internal organ and skeletal muscle sympathetic nervous system (SNS) activity in unrestrained conscious rats. Norepinephrine (NE) synthesis was blocked with alpha-methyl-p-tyrosine, and the rate of decline in tissue NE concentration after synthesis blockade was used to estimate SNS activity in the left ventricle, kidney, liver, adrenal gland, and soleus and extensor digitorum longus muscles of the hindlimb. Male Sprague-Dawley rats (250-320 g) were maintained in thermoneutral control conditions (ambient temperature = 24 degrees C, n = 10) or exposed to an ambient temperature of 42 degrees C until a colonic temperature (Tc) of 39.5 or 41.0 degrees C (n = 10 each) was attained. During heating, as Tc rose from control levels (approximately 38 degrees C) to 41.0 degrees C, mean arterial pressure and heart rate increased from 120 +/- 3 to 141 +/- 3 mmHg and from 381 +/- 4 to 420 +/- 5 beats/min, respectively (P < 0.05). There was a strong trend for increased NE turnover rates in the left ventricle, liver, and adrenal gland in NE synthesis-blocked rats attaining a Tc of 39.5 degrees C compared with the normothermic values, whereas the turnover rate in the kidney was significantly elevated at this level of hyperthermia (126%) vs. the control condition. In animals heated to a Tc of 41.0 degrees C, the NE turnover rate was markedly increased in the left ventricle (590%), kidney (531%), liver (262%), and adrenal gland (602%) compared with normothermic control values.(ABSTRACT TRUNCATED AT 250 WORDS)

Motor compensatory reactions following a forward fall in subjects with unilateral abolition of the triceps-surae H reflex

The electromyograms of the right and left soleus and tibialis anterior muscles of 6 subjects with unilateral abolition of Achilles tendon reflex due to S 1 radiculitis were recorded during a forward fall involving stepping to recover balance. Each subject took part in two series of experiments, one in which the step was performed with the unaffected leg and a second in which the affected leg was used. A unilateral deficiency of peripheral proprioceptive afferents affected ankle muscles EMG activities bilaterally, except for the EMG activity of the soleus of the starting foot. The tibialis anterior of both the affected and the unaffected side, showed either a normal pattern (i.e. a phasic contraction after soleus contraction stopped), or an early contraction. On the stance side, the early contraction was associated with a depressed soleus EMG activity. Some abnormal motor patterns could be due to the ipsilateral deficiency of the Ia inhibitory projection from soleus to tibialis anterior. The presence of abnormal patterns on the unaffected side indicates that the motor activity in one lower limb can be modified by a loss of peripheral afference in the contralateral limb. This suggests that crossed pathways between lower limbs are involved in balance recovery movement.