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PubMed1989

The influence of mediolateral deformity, tibial torsion, and foot position on femorotibial load. Prediction of a musculoskeletal computer model.

The influence of mediolateral deformity, tibial torsion, and different centers of foot support was studied with a three-dimensional computer model that incorporates the significant muscles of the lower extremities needed for quasi-static walking. This theoretical method avoids the variability in gait pattern from the pain and discomfort associated with deformity in patients. The study illustrates the possible importance of the muscle force on the load across the knee and ankle. High strains in the medial gastrocnemius and the medial hamstring created particularly high loads in the medial compartment of the knee. Internal torsion and varus deformity were associated with the highest loads in the medial compartment of the knee, although the peak load for each deformity occurred in different phases of the gait cycle. Both external torsion and valgus deformity generally decreased the load in the medial compartment, but early in the gait cycle external torsion increased the loads on the medial side. In addition, when the center of support of the body was in the forefoot, the loads through the knee were lower than when foot support was at the heel. As expected, if the center of support was on the lateral foot line, the lateral compartment was subjected to more load and, conversely, when the center of support was on the medial part of the foot the medial compartment of the knee was more loaded. Although the predicted forces agree well with those found with other methods, we think that the model is best used to measure the direction of influence of specific factors.

Biomechanical Phenomena↗
PubMed1985

The source and distribution of short-term synchrony between gamma-motoneurones in the cat.

The naturally occurring background discharges of gamma-motoneurones to gastrocnemius and soleus in the decerebrated, spinal cat show a degree of short-term synchrony which is absent when the spinal cord is intact. The characteristics of this synchrony and the mechanism producing it have been examined in the preceeding paper (Ellaway & Murthy, 1985). Short-term synchrony in the background discharge is removed by cutting the ipsilateral dorsal root (S1 or L7) at the segment of origin of the gamma-efferents. It persists on cutting other ipsilateral or any contralateral dorsal roots between L6 and S3. The source is not the homonymous or synergist muscle group. Neither is the skin which lies around the insertion of gastrocnemius-soleus on the heel the afferent source of this synchrony. However, stimulation of the heel by light stroking or pressure raises the frequency of gamma-efferent discharge and increases the degree of synchrony. Such stimulation does not produce synchrony in the decerebrated cat with an intact spinal cord. Synchrony between gamma-motoneurones is as strong between different fascicles of a muscle (gastrocnemius medialis), or different heads (gastrocnemius medialis and lateralis), as it is within one fascicle of a muscle. The timing of the peak incidence of correlated discharges always indicated synchrony at the level of the spinal cord irrespective of differences in peripheral conduction time or the destination of the axons. Hamstring and pretibial flexors show a lower incidence or weaker degree of short-term synchrony between homonymous gamma-efferents compared with gastrocnemius. Short-term synchrony is either weak or absent between gamma-motoneurones to heteronymous muscles. gamma-Efferents from homologous muscles on either side of the cord lack synchrony of discharge. The results go some way to establishing the source and connectivity to the motoneurone pool of afferents capable of synchronizing the discharge of gamma-efferents.

Afferent Pathways↗
PubMed1977

Ia afferent activity during a variety of voluntary movements in the cat.

1. Implanted dorsal root electrodes were used to record discharge trains of single spindle primary afferents (Ia's) of the cat's hind limb during different types of movement.2. The length of the ipsilateral ankle extensors was continuously monitored by an implanted length gauge. Length changes occurring during active stepping were subsequently passively reproduced during brief anaesthesia.3. A comparison of the Ia responses in active and simulated step cycles revealed that moderate fusimotor drive to ankle extensor spindles probably occurred mainly, if not exclusively, during the E(1), E(2) and E(3) phases of active stepping.4. A temporal advance in the Ia response to passive stretching in the F-phase was attributed to the after-effects of fusimotor activity in the extension phases.5. Light thrust applied to the animal's back evoked a potent fusimotor response. This load compensation effect may provide an explanation for the apparently higher degree of alpha-gamma co-activation seen in the mesencephalic locomotor preparation.6. Ankle extensor Ia discharge decreased during falls, despite an increase in extensor e.m.g. This is seen as a clear example of independent alpha and gamma control.7. Placing reactions during walking were consistent with the notion that cutaneous inputs dominate over proprioceptive inputs in these movements.8. alpha and Ia discharge during paw-shaking showed many of the characteristics of that in decerebrate and spastic clonus. The present results suggest that movements resembling clonus may be part of the animal's normal repertoire.9. Isometric co-contraction of agonists and antagonists was found to involve alpha-gamma co-activation.10. Hamstring Ia discharge behaviour during stepping further highlighted the increases in firing rate which normally occur during passive muscle stretching in ;pre-programmed' movements.

Action Potentials↗
PubMed1990

Functional changes in the antagonists after lengthening the agonists in cerebral palsy. II. Quadriceps strength before and after distal hamstring lengthening.

In a recent study, 38 patients with spastic cerebral palsy (median age, 5.6 years) were examined before and at a median 13 months after distal lengthening of the hamstrings. Four weeks after operation, the strength of the quadriceps was reduced by a median value of 70%. Seven months after operation, the strength had been regained; by 13 months after operation, it had increased by a median value of 22%. In 20 cases, strength had increased by more than 50%. The present study confirms the theory that quadriceps function is strengthened when the antagonist function is weakened. The study also explains (1) why it often takes six months for gait to become better than before operation and (2) why spasticity of the rectus often increases after the hamstrings are lengthened.

Adolescent↗
PubMed1995

The redundant nature of locomotor optimization laws.

A sagittal-plane model of the lower limb, which considered the possibility of antagonistic and synergistic muscle action and took account of the load-bearing roles of the cruciate ligaments, was applied to a dynamic analysis of level walking. It was hypothesized that: (1) the simple, one-sided constraints that intra-articular contact forces must be compressive and muscle and ligament forces tensile substantially reduce the redundancy of the load-transmitting structures of the lower limb, (2) many previously proposed optimization laws for muscle selection yield equivalent results, when they are applied to a finite set of admissible limiting solutions, and (3) the aforementioned optimization laws, when applied to a finite set of admissible limiting solutions, do not adequately predict the co-contraction of antagonistic muscles during gait. The problem of indeterminacy was resolved by considering all possible limiting solutions of the system unknowns on the dynamic equations. Although 498 limiting solutions of nine unknowns could arise at each sampled point on the gait cycle, the aforementioned one-sided constraints ruled out the large majority of them. It was shown that of the 498 possible, the minimum number of simultaneous admissible solutions for any subject was as few as three and the maximum number was only 18. The Principles of minimal total muscle force, squared muscle force, muscle stress, intra-articular contact force and instantaneous muscle power predicted remarkably similar patterns of muscle activity over the gait cycle. Of the six tested performance criteria, the Principle of minimal total ligament force was the least successful in terms of selecting solutions that closely matched the EMG patterns. This result implied that the muscles do not always act to protect the knee ligaments during gait. Finally, each of the above minimum principles failed to predict any antagonistic quadriceps-hamstrings action at the knee and hip around the event of heelstrike, although such activity was indicated by electromyography.

Adult↗
PubMed1996

Measures of paraspinal muscle performance do not predict initial trunk kinematics after tripping.

The ability to limit the trunk flexion associated with an anteriorly directed trip is a determinant of successful recovery of recovering postural stability and is subservient to rapidly detecting and correcting the imposed trunk flexion in the available time. This experiment tested the hypothesis that subjects demonstrating greater eccentric trunk/hip extension strength, faster voluntary reaction times, shorter automatic response latencies, and larger automatic activation amplitudes of the paraspinal muscles, would demonstrate less trunk flexion following a trip. An isokinetic protocol was used to obtain measures of trunk extension strength, response latencies, and activation amplitudes. Motion analysis methods were used to quantify trunk kinematics during the positioning phase of recovery following an induced trip. Statistically significant and functionally meaningful relationships between eccentric strength of the trunk/hip extensors, voluntary-reaction time, automatic reaction time, activation amplitudes and trunk kinematics failed to emerge. Thus, although automatic and voluntary paraspinal muscle responses have the potential to limit trunk flexion during the positioning phase of recovery, the task may be achieved through intersegmental factors or other muscular sources such as the gluteus maximus and hamstrings.

Accidental Falls↗
PubMed1976

The liver as a privileged site for parathyroid alloimplanation in the rat.

It has been suggested that the liver suppresses the immune response to alloantigen. This hypothesis was tested utilizing parathyroid implantation into the liver and muscles of inbred rats. Recipients were parathyroidectomized and, after significant hypocalcemia, donor parathyroids from minor histoincompatible rats were implanted either in liver or in thigh hamstring. In one experimental group second-set grafting also was tested. Graft survivals were evaluated by (1) duration of functional response (DFR), the period of time during which the serum calcium level remained above the postparathyroidectomy baseline, (2) maximal response (MR), the proximity of the postimplantation calcium peak response to the normal preparathyroidectomy calcium level. Parathyroid implants survived significantly longer in the liver compared to the muscle, only when implanted across minor histocompatible barriers. It is suggested that the liver may contain an inhibitor, capable of suppressing the lymphocytes and thus suppressing immune response, which can be demonstrated when the histocompatibility barrier is weak.

Animals↗
PubMed1999

"Task-oriented" exercise improves hamstring strength and spastic reflexes in chronic stroke patients.

BACKGROUND AND PURPOSE: Despite the belief that after cerebral infarction only limited functional gains are possible beyond the subacute period, we tested the hypothesis that a 12-week program of "task-oriented" treadmill exercise would increase muscle strength and decrease spastic reflexes in chronic hemiparetic patients. METHODS: Fourteen subjects, aged 66+/-3 (mean+/-SEM) years, with residual gait deviations due to remote stroke (>6 months), underwent repeated measures of reflexive and volitional (concentric and eccentric) torque with use of isokinetic dynamometry on the hamstring musculature bilaterally. Torque output was measured at 4 angular velocities (30(o), 60(o), 90(o), and 120(o)/s). RESULTS: After 3 months of 3 times/wk low-intensity aerobic exercise, there were significant main effects (2 legs [P<0.01]x2 times [P<0. 01]x4 angular velocities [P<0.05]) for concentric torque production. Torque/time production in the concentric mode also improved significantly in the paretic (50%, P<0.01) and nonparetic hamstrings (31%, P<0.01). Eccentric torque/time production increased by 21% (P<0.01) and 22% (P<0.01) in the paretic and nonparetic hamstrings, respectively. Passive (reflexive) torque/time generation in the paretic hamstrings decreased by 11% (P<0.027). Reflexive torque/time was unchanged in the nonparetic hamstrings (P=0.45). CONCLUSIONS: These findings provide evidence that progressive treadmill aerobic exercise training improves volitional torque and torque/time generation and reduces reflexive torque/time production in the hemiparetic limb. Strength changes associated with improved functional mobility in chronic hemiparetic stroke survivors after treadmill training will be reported in future articles.

Aged↗
PubMed2005

Return to play following muscle strains.

OBJECTIVE: To assess return to play strategies following muscle strains with the desired outcomes of decreased competition play lost and minimized risk for recurrent injury. METHODS: Literature review of previous studies that examine return to play criteria for the commonly seen muscle strain injuries in sport. RESULTS: There have been no studies directly comparing different return to play approaches. Studies have instead concentrated on recurrence risk factors and prognosis assessment, particularly for hamstring injuries. There is some literature support for risk factors for recurrence such as persisting strength deficits, larger injuries seen on diagnostic imaging, players in high-risk positions or sports, inability to complete functional tasks without pain, and strains of specific high-risk muscles (biceps femoris, central tendon of rectus femoris, medial head of gastrocnemius, adductor longus or magnus). CONCLUSIONS: There are no consensus guidelines or agreed-upon criteria for safe return to sport following muscle strains that completely eliminate the risk for recurrence and maximize performance. At this time, it may be a sensible strategy to allow earlier return to play in team sports and accept a low to moderate injury recurrence rate. Improved prognostic assessment of muscle strains with injury identification (MRI) and injury assessment (isokinetic testing) may be assist practitioners to lower, but not eliminate, recurrent injuries.

Athletic Injuries↗
PubMed1992

Contralateral v ipsilateral cane use. Effects on muscles crossing the knee joint.

Although using a cane contralaterally has been shown to reduce muscular activity across the hip joint, little is known about effects on the knee. We measured muscular activity around the knee in 10 able-bodied subjects. We simultaneously recorded integrated rectified surface electromyographic activity from the right quadriceps, medial and lateral hamstrings, gastrocnemius and hip abductors during various standing maneuvers: two-legged stance, unsupported one-legged stance and one-legged stance putting maximal, moderate (20% body weight) or minimal (10% body weight) force through an ipsilateral or contralateral cane. Electromyographic activity was expressed as the percentage of that recorded during unsupported one-legged stance in each muscle. Hip abductor activity was lowest when maximal weight was placed through a contralateral cane (66%) and highest with maximal weight ipsilaterally (424%). Medial hamstrings activity increased by 404% and 200%, respectively, when maximal and moderate force was applied to a contralateral cane, although there was no change with ipsilateral cane. Lateral hamstrings were also most active during contralateral cane use. Quadriceps activity decreased using a cane in either hand with moderate or minimal force (range 57 to 84%). Gastrocnemius activity decreased during contralateral (60 to 66%) and ipsilateral (75 to 96%) cane use. This data suggests that forces generated by muscular activity around the knee are not uniformly diminished by holding a cane in the contralateral hand and may even be increased.

Adult↗
PubMed2004

Muscle strains in soccer: a five-year survey of an Italian major league team.

We analyzed muscle injuries collected from an Italian major-league soccer team during the period 1995-2000. We considered all the muscle accidents that had required a player to stand down for three or more days. Among the overall injuries, muscle accidents were the most frequent, representing 30% (103 cases), followed by contusions (28%), sprains (17%) and tendinopathies (9%). There was one recurrence involving the hamstring. Lack of training was one of the causes of such injuries; in fact the training/match ratio of those seasons (3.6 to 1) show that there was little time for training compared to the number of matches.

Athletic Injuries↗
PubMedDate not supplied

Torque-velocity relationships of the knee extensor and flexor muscles in individuals sustaining injuries of the anterior cruciate ligament.

Muscle deficits in 58 patients with chronic anterior cruciate ligament (ACL) insufficiency were evaluated after completion of a 6 month rehabilitation program. Quadriceps and hamstring torques were measured on a modified Cybex II isokinetic dynamometer. Twenty-nine of our patients were tested just prior to undergoing ACL reconstruction, and patients who were continuing to tolerate their conditions served as controls. For the surgical group, significant quadriceps deficits (P less than 0.01) were found for all speeds and at both the 30 and 60 degrees positions. The nonsurgical group had significant deficits at the 30 degrees position at 180 degrees/sec, and at 60 degrees for the 0 degree/sec and 30 degrees/sec. However, in comparing the two groups no significant differences were noted. Regarding hamstring deficits in the surgical group, significant deficits were seen only at 30 degrees of flexion at 180 degrees/sec. The nonsurgical group had similar deficits. Of interest was the observation that the hamstring:quadriceps (H:Q) ratio was found to be both speed-position dependent. Overall, no correlation was found between the presence of strength deficits following a rehabilitation program and the need for surgery.

Adolescent↗
PubMed1990

Contralaterally projecting lamina VIII interneurones in middle lumbar segments in the cat.

Peripheral input to lamina VIII interneurones was investigated by using extracellular and/or intracellular records from them. The interneurones were located in the L4-L5 spinal segments and projected to contralateral motor nuclei in the L7 segment. They constituted a non-homogeneous population but their input from muscle afferents (mainly group II afferents of quadriceps, flexor digitorum longus and pretibial flexors and group I afferents of triceps surae and hamstring nerves) and from cutaneous and joint afferents resembled the input to ipsilaterally projecting laminae V-VII interneurones of the same segments rather than the input to more caudally located lamina VIII interneurones. Since the ipsilaterally projecting laminae V-VII interneurones with such an input might be involved in locomotion, it is proposed that this is also the case for the contralaterally projecting lamina VIII midlumbar interneurones, especially those excited by stimuli applied in the cuneiform nucleus (mesencephalic locomotor region).

Animals↗
PubMed1995

Exercise effect of modified contralateral stabilization bar during one-legged isokinetic exercise.

We compared the electrical activities recorded from the muscles of the unexercised leg with changing the position of the contralateral stabilization bar to determine whether the degree of muscle contraction was influenced by the position of the bar during one-legged isokinetic exercise using an isokinetic dynamometer. The root mean square (RMS) values recorded from the medial hamstring sites of the unexercised legs showed a significantly higher value when the bar was located behind and on both in front of and behind the unexercised leg during one-legged extension exercise. Results from the isokinetic knee flexion exercise test indicated that a significantly greater RMS value was recorded from the vastus lateralis sites when the bar was located in front of and on both sides of the unexercised leg. During one-legged isokinetic extension-flexion exercise, the mean values of RMS voltage were greater when the bar was positioned in front of and on both sides of the unexercised leg in the vastus lateralis site. At the medial hamstring site, a greater value was noticed when the bar was located behind or on both sides.

Adult↗
PubMed1989

Prediction of torque acceleration energy and power of thigh muscles from peak torque.

The purpose of this study was to assess the relationship between the isometric and isokinetic peak torque (PT) (speed of movement 0, 60, and 180 degrees.s-1) and the peak torque acceleration energy (PTAE) and average power (AP) of multiple contractions (180 degrees.s-1) of the quadriceps and hamstrings in 38 patients having a chronic, complete anterior cruciate ligament (ACL) insufficiency in the knee. At every test speed the Pearson product moment (r) and the Spearman rank (rs) correlation coefficients between the PT and PTAE were highly significant for both muscle groups in the uninjured (r = 0.79-0.94, rs = 0.78-0.94) as well as in the ACL-insufficient (r = 0.87-0.95, rs = 0.83-0.94) knees. The results were the same between the PT and AP (uninjured: r = 0.70-0.90, rs = 0.68-0.90; ACL insufficient: r = 0.86-0.93, rs = 0.82-0.93). In both knees and in both muscle groups the correlation coefficients increased simultaneously with the speed of movement, obviously since the PTAE and AP were registered at the highest test speed (180 degrees.s-1). In conclusion, concerning ACL-insufficient or uninjured knees, the PTAE or AP analysis may offer little additional information about thigh muscle function to that attained by more simple measurement, the PT analysis.

Acceleration↗
PubMed1989

Torque acceleration energy, power and peak torque in thigh muscles after a previous knee sprain.

This investigation assessed the relationship between the isometric and isokinetic peak torque (PT) (speed of movement 0, 60, and 180 degrees(s) and (I) the peak torque acceleration energy (PTAE), and (2) average power (AP) of multiple contractions (180 degrees/s) of the quadriceps and hamstrings in subjects with a past history of a grade I knee injury. At every test speed the Pearson product moment (r) and the Spearman rank (rs) correlation coefficients between the PT and PTAE were significant (p less than .001) for both muscle groups in the uninjured (r = .83-.97, rs = .84-.97) as well as in the injured (r = .86-.95, rs = .86-.95) Knees. The results were similar in comparison of PT and AP (uninjured: r = .81-.97, rs = .81 -.97; injured: r = .82-.98, rs = .83-.98). The PTAE and AP analyses offer little additional information about thigh muscle function to that obtained through more simple measurements, the PT analysis.

Adult↗
PubMed2002

Computer added locomotion by implanted electrical stimulation in paraplegic patients (SUAW).

Paraplegia means a live long sentence of sensory loss, paralysis and dependence with approximately 1000 new victims in every European country every year and 11.500 new traumatic SCI cases in the US. respectively. Sixty percent are injured before age 30. More than 90% of SCI victims may survive with nearly normal experience of live. Most patients will recover somewhat from SCI over time but no patient who remained plegic for one year regains voluntary motor function after that time period. Despite remarkable efforts and recent achievements in rehabilitation no treatment can be recommended so far to enhance functional recovery and restoring locomotion in paraplegic humans. FES as a technical compensation has become therefore a challenging treatment to restore muscle function and to prevent atrophy and to improve mobility and quality of life at the same time. In paraplegics FES could be the basis to restore locomotion. One of the advantages of an implanted FES version (neuroprosthesis) is that the FES system, electrodes, and cables remain permanently implanted within the body, so that the patient can stay without cables, the programmer attached to the crutches. The SUAW project, supported under BIOMED II Programme by the European Community was aimed to finalize and to put into practice the results of previous research and development. The novel implant with an ASCI-Chip has 16 channels, 8 on each side, 20 mA for monopolar and 2 mA for bipolar stimulation, only one electrode can be stimulated at a given time. Stimulation of 6 muscle groups of both legs are known to be sufficient for locomotion: M. ileopsoas (erector of the body, hip flexor), M. gluteus maximus (hip extensor), M. gluteus medius (lateral hip stabilisator, knee abductor), Mm. hamstrings (knee flexor) stimulated by epimysial electrodes, Mm. sartorius and rectus femoris (knee extensor) stimulated by neural, bipolar electrodes. Patient's selection criteria were: stable spinal cord lesion between T7 and T11, minimum 1 year after the accident without deformity of the spine, the muscle groups for locomotion responding to external FES with the EXOSTIM programmer with the same programme used later for the neuroprosthesis. Two paraplegic male patients, T8, 38 and 31 years old respectively, were operated on by an international group of surgeons according to the protocol in 09/1999, respectively 7/2000. The postop. course was uneventful. Because the threshold of the primary implant was too low regarding scare tissue around the electrodes, this implant was changed in 01/2000 and worked perfectly. Both patients are happy with the success of the novel treatment modalities.

Adult↗