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At least 811 records · Page 45Linked to original sources

PubMed1994

Immune responses to nervous system decentralization and exercise in quadriplegia.

Interactions among the nervous, neuroendocrine, and immune systems render host defenses highly sensitive to autonomic over- or understimulation. Persons with quadriplegia experience decentralization of directly innervated immune tissues and neuroendocrine axis dysregulation, immobilization deconditioning, heightened exposure to immune suppressing xerobiologicals, and psychic and nonpsychic stressors differing from those of nondisabled cohorts. When compared with matched nondisabled controls, young survivors of quadriplegia have reduced CD4:CD8 ratios, suppressed proliferative responses to mitogen challenge, reduced number and cytotoxicity of CD3-CD56+ (NK) cells, and elevation of the soluble IL-2 receptor. Deviations from control values are typically observed in persons with injuries higher than sympathetic outflow, suggesting a cause related to autonomic dysfunction. Cycling exercise performed by persons with quadriplegia using computer-sequenced electrically stimulated contraction of the quadriceps, hamstring, and gluteus muscle groups fails to provoke an archetypical leukocytosis, but transitionally elevates NK cell number and cytotoxicity lasting one-half hour after exercise. These findings show that the immune system of persons with quadriplegia is selectively responsive to exercise challenge. As opportunistic infections of the urinary tract, lungs, and skin are major causes of morbidity in survivors of quadriplegia, these observations may identify a treatment through which their host defenses can be fortified.

Autonomic Nervous System↗

PubMed1994

Common rugby league injuries. Recommendations for treatment and preventative measures.

Rugby league is the main professional team sport played in Eastern Australia. It is also very popular at a junior and amateur level. However, injuries are common because of the amount of body contact that occurs and the amount of running that is required to participate in the game. Injuries to the lower limbs account for over 50% of all injuries. The most common specific injuries are ankle lateral ligament tears, knee medial collateral and anterior cruciate ligament tears, groin musculotendinous tears, hamstring and calf muscle tears, and quadriceps muscle contusions. Head injuries are common and consist of varying degrees of concussion as well as lacerations and facial fractures. Serious head injury is rare. Some of the more common upper limb injuries are to the acromioclavicular and glenohumeral joints. Accurate diagnosis of these common injuries using appropriate history, examination and investigations is critical in organising a treatment and rehabilitation plan that will return the player to competition as soon as possible. An understanding of the mechanism of injury is also important in order to develop preventative strategies.

Athletic Injuries↗

PubMedDate not supplied

New quantitative and qualitative measures on functional mobility prediction for stroke patients.

The purpose of this study was to explore whether we could provide supportive laboratory evidence for clinical observations that a stroke patient has lost functional mobility/locomotion capability based on dynamic balance responses (centre of pressure, COP sway patterns) and motor control activities (EMG patterns) during the motor task of sit-to-stand. A computerized controlled dynamic postural control assessment system was developed and used in this study. Various dynamic balance indices were introduced and derived from COP sway patterns expressed in four domains (i.e. space, time, force, and frequency). Motor control was assessed by multi-channel surface electromyography of each side of the lower limb during the same motor task. The functional mobility capability was evaluated using a traditional FIM method. Fourteen stroke patients with right hemiplegia and nine healthy elderly were recruited as the experimental and control groups respectively. Muscle activity was recorded for quadriceps, hamstrings, anterior tibialis, and triceps surae muscles and used for analysis. Centre of pressure sway patterns and ground reaction forces were registered. All signals were synchronized at 'seat-off'. Surface electromyographic patterns of activities recorded during sit-to-stand and dynamic balance indices computed from centre of pressure sway patterns were categorized and compared with the functional mobility scores. The results show that both the motor control patterns and dynamic balance indices correlated well to the extent of mobility impairment evaluated using the traditional FIM method. An important conclusion for rehabilitation medicine is that the functional mobility capability of stroke patients may be quantified analytically using dynamic balance indices and visualized graphically through EMG motor patterns.

Activities of Daily Living↗

PubMed1990

Rationale and protocol for postoperative anterior cruciate ligament rehabilitation.

A rehabilitation program for postoperative anterior cruciate ligament (ACL) reconstruction permits adequate tissue healing time and allows early protected muscular conditioning. The program is based on kinematic, biomechanical, and kinesiologic factors as they pertain to ACL function. The program is divided into five phases. The early phases, zero to 12 weeks, are intended to control translational forces across the ACL and to allow necessary time for ligament revascularization and soft-tissue healing. During this period, isometric and isotonic training of the hamstrings and quadriceps muscle groups in a restricted active arc of motion is permitted. Passive motion is encouraged, and progressive weight bearing is allowed. Conditioning of the upper body as well as the nonsurgical lower limb is stressed. During the advanced phases, 12-31 weeks, isotonic muscle training continues throughout a full range of motion. Greater strength, coordination, and endurance to achieve dynamic stability of the knee, preparing the patient for unrestricted activity, are stressed. Approximately 52 weeks of active rehabilitation after ACL reconstruction surgery are usually required to return to a preinjury level of function.

Biomechanical Phenomena↗

PubMed1989

Rehabilitation of the knee.

Rehabilitation of the knee following injury or operative reconstruction and repair is vitally important to realizing optimal results, return to athletics, labor, and activities of daily living. Outlined in detail is a regimen of continuous passive motion, protected early weight bearing, co-contraction (EMS) of hamstring and quadriceps muscles for conditioning and analgesia (TENS), and functional concentric--eccentric loading of the knee musculature. A rationale based on an understanding of biologic rates of healing, fixation strength, ligament isometricity, and stress-induced healing is discussed.

Athletic Injuries↗

PubMed1995

Gas exchange kinetics during functional electrical stimulation in subjects with spinal cord injury.

We examined the kinetics of VO2, VCO2, and VE following the onset of unloaded leg cycling, and in recovery, in six patients with spinal cord injury (SCI). Exercise was produced by functional electrical stimulation (FES) of the quadriceps, hamstrings, and gluteal muscles. End-exercise VO2 (1.03 +/- 0.16 l.min-1), VCO2 (1.20 +/- 0.22 l.min-1) and VE (41 +/- 10 l.min-1) were elevated compared to values typically seen in healthy ambulatory subjects performing similar unloaded cycling. Mean response times for the on transients (MRTon) were both long and variable across subjects for VO2 (165 +/- 62 s), VCO2 (173 +/- 58 s), and VE (202 +/- 61 s). Recovery kinetics showed much less intersubject variability, and for five of six subjects were faster than the equivalent exercise MRT for all three variables (MRToff for VO2 of 103 +/- 28 s, VCO2 136 +/- 20 s, and VE 144 +/- 34 s), but P > 0.05 for all three. Size of the O2 deficit (1.96 +/- 0.90 l) and end-exercise lactate (7.05 +/- 1.65 mmol.l-1) were similar to values reported for healthy sedentary subjects performing maximal voluntary exercise, but the end-exercise heart rate (102 +/- 16 bpm) was lower than expected for this intensity of exercise. In conclusion, FES-induced unloaded cycling leads to exaggerated responses of pulmonary gas exchange and long time constants in patients with SCI. The delayed kinetics may be due in part to a blunted increase in heart rate in addition to severe deconditioning.

Adult↗

PubMed2006

Biomechanical characterization and clinical implications of artificially induced crouch walking: Differences between pure iliopsoas, pure hamstrings and combination of iliopsoas and hamstrings contractures.

The purpose of this study was to characterize biomechanically three different crouch walking patterns, artificially induced in eight neurologically intact subjects and to compare them to selected cases of pathological crouch walking. The subjects were equipped with a lightweight mechanical exoskeleton with artificial muscles that acted in parallel with hamstrings and iliopsoas muscles. They walked at a speed of approximately 1m/s along the walkway under four experimental conditions: normal walking (NW), hamstrings contracture emulation (HAM), iliopsoas contracture emulation (IPS) and emulation of both hamstrings and iliopsoas contractures (IPSHAM). Reflective markers and force platform data were collected and ankle, knee and hip-joint angles, moments and powers were calculated. HAM and IPSHAM shifted ankle-angle rotation profiles into dorsiflexion during midstance compared to IPS and NW where ankle-angle trajectories were similar. HAM, IPS and IPSHAM shifted the knee angle of rotation profiles into flexion during stance, compared to NW. IPS and IPSHAM shifted hip angle of rotation profiles toward pronounced flexion while HAM shifted hip angle of rotation profile toward extension, compared to NW. HAM and IPSHAM significantly increased ankle moment during midstance, compared to IPS and NW where ankle moment profiles were similar. All experimental conditions exhibited similar behavior in the knee-moment profiles during midstance while IPS and IPSHAM knee-moment profiles exhibited significantly higher knee-extension moment during terminal stance and pre-swing. In the hip joint all experimental conditions exhibited similar shape of hip moment profiles throughout the gait cycle. HAM and IPS kinematic and kinetic patterns were qualitatively compared to two selected clinical cases, showing considerable similarity. This implies that distinct differences in kinematics and kinetics between HAM, IPS and IPSHAM may be clinically relevant in helping determine the relative contribution of hamstrings and iliopsoas muscles contractures to particular crouch walking.

Adult↗

PubMed1998

Weight cycling alters muscular strength and endurance, ratings of perceived exertion, and total body water in college wrestlers.

Weight cycling is the continued loss of body weight practiced by wrestlers to compete in a lower weight class. Effects of weight cycling on muscular strength, muscular endurance, total body water, and ratings of perceived exertion of the dominant hamstring-quadricep and shoulder girdle were examined in 19 wrestlers during a collegiate season. Over a 4.5-mo, period, total body water changes occurred only during acute dehydration. A decrease of > or = 3% of body weight over a 24-hr. period was classified as acute dehydration. Large muscle groups changed little in muscular strength and endurance whereas the smaller shoulder abductors and adductors and hamstring muscles were differentially affected at times of testing. Ratings of perceived exertion declined after the 4.5-mo. wrestling season of weight cycling but not at times of acute dehydration.

Acute Disease↗

PubMed2025

Genome-Wide Association Study on Muscle Stiffness Identified Novel Locus for Predisposition to Muscle Strain Injury.

PURPOSE: We aimed to screen the entire genome for genetic variants associated with passive muscle stiffness, which has been suggested as a risk factor for muscle strain injury. METHODS: This genome-wide association study (GWAS) on passive muscle stiffness included 350 physically active young Japanese individuals. Three hamstring constituents were measured using ultrasound shear wave elastography. Skeletal muscle transcriptomes were compared across the genotypes of GWAS-identified variants in 48 healthy Japanese individuals. Association between GWAS-identified variants and history of muscle strain injury was examined in 1428 Japanese athletes. RESULTS: Two loci on chromosome 11 demonstrated a genome-wide significant association with passive muscle stiffness of the biceps femoris long head (rs12807854 T/C: P = 5.19 × 10 -10 , rs78405694 T/C: P = 2.09 × 10 -8 ; linear regression analysis adjusted for sex, age, and stretching exercise habits). Skeletal muscle RNA sequencing revealed significantly elevated expression of extracellular matrix-related genes in muscles carrying stiffness-increasing alleles of these variants. Among athletes, rs12807854 T/C was significantly associated with a history of muscle strain injury ( P = 0.0254; logistic regression analysis adjusted for age, sex, competitive level, and main sport). Carriers of the C allele, associated with increased muscle stiffness, exhibited a heightened risk of muscle strain injury (odds ratio = 1.62; 95% confidence interval = 1.06-2.47 per C allele increase). By contrast, rs78405694 did not show a significant association with muscle strain injury in this population. CONCLUSIONS: A novel locus associated with passive muscle stiffness and muscle strain injury was identified. Elucidating the detailed mechanisms linking the identified locus to passive muscle stiffness may lead to the development of new strategies to prevent muscle strain injuries.

Humans↗

PubMed1996

Muscle strength after successful total knee replacement: a 6- to 13-year followup.

This study investigated the long term results of muscle strength of the knee joint after total knee replacement. Isokinetic testings of 120 degrees and 180 degrees per second and isometric testings at 30 degrees and 60 degrees knee flexion were studied on 1 healthy group and 3 groups of patients 6 to 13 years after total knee arthroplasty with prosthesis designs of total condylar, low contact stress meniscal bearing, or low contact stress rotating platform. The total condylar and low contact stress rotating platform prostheses were designed for use with a cut posterior cruciate ligament, whereas the low contact stress with meniscal bearing type was designed for use with a retained posterior cruciate ligament The muscle strength ratios of hamstring to quadriceps were compared among the prosthetic designs and there were no statistical differences among patient groups. Whether the posterior cruciate ligament was cut or retained did not affect the relative muscle strength of the quadriceps and hamstring. All hamstring to quadriceps ratios from the isokinetic testings of these 3 prostheses design groups were greater than those of the healthy group, but were quite close to those of patients with cut anterior cruciate ligaments or with lower levels of daily activity. The hamstring to quadriceps ratios after successful total knee replacement were not the same as those of the healthy group even after long term (6-13 years) functional adaptation.

Aged↗

PubMed1988

Influence of stimulus parameters on human postural responses.

1. The role of sensory information in shaping muscle activation patterns to postural perturbations in humans was investigated by varying velocity, amplitude, or duration of the perturbing stimulus. Ten normal subjects were exposed to 120 backward translations of the support surface under conditions of varying velocities (10-35 cm/s, constant amplitude), varying amplitudes (1.2-12 cm, constant velocity), or varying durations (40-800 ms). The effects of perturbation parameters on movement kinematics and EMG latencies, patterns, and integrated areas in six trunk and leg muscles were examined. Integrated EMG activity was normalized across subjects and the early (first 75 ms), middle (second 75 ms), and late (last 350 ms) components were analyzed separately. 2. Ankle, knee, and hip angle trajectories and surface reactive forces suggest that a relatively consistent movement strategy was scaled to the perturbation velocities and amplitudes applied. 3. Short-duration perturbations (75 ms) evoked a single burst of muscle activity (75-100 ms duration) in gastrocnemius, hamstrings, paraspinal, and rectus abdominis muscles at latencies too long to be explained by simple stretch reflexes. EMG latencies, patterns, and integrated areas were independent of the velocity and amplitude of the short-duration perturbations, suggesting a minimal time to incorporate peripheral velocity information into the triggered response. 4. For translations lasting longer than 75 ms, the integrated areas of the early agonist EMG bursts were positively correlated with stimulus velocity. The integrated area of later, more tonic EMG components were best correlated with stimulus amplitude. These relationships were found in both distal (stretched) muscles and in proximal muscles. Absolute latencies (94-145 ms), intersegmental latencies (18-29 ms), and burst durations (75-100 ms) were not influenced by the velocity or amplitude of the stimulus. 5. These results suggest that the spatial and temporal organization of automatic postural responses may be organized independently of response intensity. Within a particular spatial-temporal pattern, the amount of muscle activation appears to be adjusted by sensory information, which specifies velocity and amplitude of the perturbation.

Adult↗

PubMedDate not supplied

Neuromuscular adaptations in isokinetic, isotonic, and agility training programs.

Weight training is an integral part of most athletic conditioning programs; yet, the effect of these programs on neuromuscular function remains unclear. To examine the neuromuscular effects of training and conditioning at the knee joint, 32 volunteers (16 men and 16 women; average age, 25.4 years) were placed into one of four groups: isokinetic, isotonic, agility, or control. Each group trained 3 days per week for 6 weeks. The knee function of all participants was evaluated just before and after the 6-week training period. The agility-trained group significantly improved the spinal reflex times of the lateral and medial quadriceps muscles in response to anterior tibial translation. The cortical response time of the agility group also significantly improved in the gastrocnemius, medial hamstring, and the lateral quadriceps muscles. Interestingly, the cortical response time of the medial hamstring and the medial quadriceps muscles in the isokinetic group slowed significantly, by 39.1 and 32.4 msec, respectively, after 6 weeks of training. Isotonic and isokinetic strength training of the lower extremities do not appear to improve muscle reaction time to anterior tibial translation, whereas agility exercises potentially improve this parameter.

Adaptation, Physiological↗

PubMed2001

Dynamic stability in the anterior cruciate ligament deficient knee.

Some individuals can stabilize their knees following anterior cruciate ligament rupture even during activities involving cutting and pivoting (copers), others have instability with daily activities (non-copers). Movement and muscle activation patterns of 11 copers, ten non-copers and ten uninjured subjects were studied during walking and jogging. Results indicate that distinct gait adaptations appeared primarily in the non-copers. Copers used joint ranges of motion, moments and muscle activation patterns similar to uninjured subjects. Non-copers reduced their knee motion, and external knee flexion moments that correlated well with quadriceps strength. Non-copers also achieved peak hamstring activity later in the weight acceptance phase and used a strategy involving more generalized co-contraction. Both copers and non-copers had high levels of quadriceps femoris muscle activity. The reduced knee moment in the involved limbs of the non-copers did not represent "quadriceps avoidance" but rather represented a strategy of general co-contraction with a greater relative contribution from the hamstring muscles.

Adult↗

PubMed2004

Control of support limb muscles in recovery after tripping in young and older subjects.

Older people fall more often after tripping than young people due to a slower development of mechanical responses. This might be due to age-related changes in muscle properties, but also to changes in motor control. The purpose of the present study was to determine whether (a) timing and sequencing of muscle activation and (b) the magnitude and rate of development of muscle activation in recovery after a trip differs between young and older subjects. We focused on the support limb, as it contributes to recovery after tripping by counteracting the forward angular momentum. Ten young (25 years) and seven older (68 years) men and women walked over a platform and were tripped several times at different points in the gait cycle. Kinematics and EMG of the support limb muscles were measured. After tripping, rapid EMG responses (60-80 ms) were observed in hamstring and triceps surae muscles in both young and older subjects. A slightly increased delay (11 ms) was found only in the soleus muscle of the older subjects. The muscle activity patterns (timing and sequencing) were similar in young and older subjects, but the magnitude and rate of development of muscle activity were significantly lower in older subjects. Especially the lower rate of development of muscle activation in the support limb of older subjects is likely to reduce the rate of force generation, which can contribute to inadequate recovery responses and falls.

Adult↗

PubMed2004

Predicting hamstring strain injury in elite athletes.

INTRODUCTION: Eccentric exercise, where the contracting muscle is lengthened, produces microscopic damage in muscle fibers, and sensations of stiffness and soreness, the next day. These normally resolve within a week. A more major sports injury is the muscle strain. Because strain injuries are known to occur during eccentric contractions, it is hypothesized that the microscopic damage from eccentric exercise can, at times, progress to a muscle strain. As the amount of microscopic damage depends on the muscle's optimum length for active tension, it is further proposed that optimum length is a measure of susceptibility for muscle strains. The athletes most at risk of a hamstring strain are those with a previous history of such injuries. Here the prediction is tested that optimum lengths of previously injured hamstrings are shorter and therefore more prone to eccentric damage than uninjured muscles. METHODS: Mean optimum angle for peak torque in a previously injured muscle of nine athletes with a history of unilateral hamstring strains was compared with the uninjured muscle of the other leg and with muscles of 18 uninjured athletes. Optimum angle was determined with isokinetic dynamometry. RESULTS: In previously injured muscles, torque peaked at significantly shorter lengths than for uninjured muscles. Peak torque and quadriceps:hamstrings torque ratios were not significantly different. CONCLUSIONS: The shorter optimum of previously injured muscles makes them more prone to damage from eccentric exercise than uninjured muscles and this may account for the high reinjury rate. The shorter optimum may reflect the muscle's preinjury state or be a consequence of the healing process. To reduce the incidence of strain injuries, it is recommended that a combined program of eccentric exercise and muscle testing be carried out.

Adult↗

PubMed2005

Physiological and anthropometric characteristics of starters and non-starters and playing positions in elite Australian Rules Football: a case study.

A purpose of this study was to determine if pre-season anthropometric and physiological measures were significantly different for the players from one Australian Football League (AFL) club selected to play in the first game of the season compared to the players not selected. Another purpose was to compare fitness test results for defenders, forwards and mid-fielders in the same AFL club. Thirty-four players were tested for isolated quadriceps and hamstrings strength, leg extensor muscle strength and power, upper body strength, sprinting speed, vertical jump (VJ), endurance, skinfolds and hamstring flexibility. The starters who were selected to play the first game were a significantly older and more experienced playing group, and were significantly better (p < 0.05) in measures of leg power, sprinting speed and the distance covered in the Yo Yo intermittent recovery test compared to the non-starters. Although there were trends for the superiority of the starters, the differences in lower and upper body strength, VJ and predicted VO2max were non-significant. The forwards generally produced the worst fitness scores of the playing positions with the midfielders having significantly lower skinfolds and the defenders possessing better hamstring strength and VJ compared to the forwards. It was concluded that some fitness qualities can differentiate between starters and non-starters, at least in one AFL club. Comparisons of playing positions and the development of fitness norms for AFL players require further research.

Adult↗

PubMed1987

[Current status of the therapy of anterior cruciate ligament injuries].

This review presents the current concepts in the treatment of anterior cruciate ligament (ACL) injuries. Conservative treatment emphasising strengthening of the muscles to stabilise an unstable knee is discussed. The agonistic and antagonistic functions of the hamstrings and the quadriceps muscle in relation to the ACL are described. The possible mechanisms of muscular stabilisation of the knee are discussed on a neurophysiological basis. The existence of joint specific receptors is pointed out and their reflex and perceptive functions are demonstrated. Taking this into account one can deduce a two-step mechanism of joint protection: 1) via the mechanical strength of the joint capsule and ligaments and 2) via reflex muscle contractions. It follows therefrom that in an unstable knee with a lax capsule and disturbed reflex mechanisms, strengthening of muscles alone is insufficient and cannot protect the joint from progressive deterioration. Therefore, surgical treatment is necessary for an ACL deficient knee. Our indications for ACL reconstruction are described. In addition, the existing methods of surgical replacement of the ACL are critically elucidated. In our opinion, an extraarticular repair tendon transfer as the only surgical procedure to regain stability is of only historical interest. However, extraarticular repair of the medial or lateral capsule is often a necessary additional step to restore stability of the knee. The replacement of the ACL is the crucial step. Using autogenous grafts one must consider the doubtful outcome of biological response leading to necrosis and revascularization in the transplant.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗

PubMed2002

Cruciate ligament reflexes.

The idea of muscular reflexes elicited from sensory nerves of the cruciate ligaments is more than 100 years old, but the existence of such reflexes has not been proven until the recent two decades. First in animal experiments, a muscular excitation could be elicited in the hamstrings when the anterior cruciate ligament (ACL) was pulled, and tension in the ligament caused activity of the gamma motor neurones of the muscles around the knee. Impulses from the sensory nerves in ACL were activated during motion of the knee, in particular overstretching and combined extension and rotation. In humans, proprioception in the knee is decreased after ACL rupture. By mechanical or electrical stimulation of the ACL, an excitation in the hamstrings muscles can be elicited. During muscular activity, stimulation of the ACL or PCL results in a clear inhibition of the ongoing activity, both during static isometric and isokinetic muscle work, and also during dynamic activity (gait). This inhibitory reflex subjectively resembled giving way. The latency of the reflex was short in animals (about 3 ms) and long in humans (60-120 ms), probably caused by differences in the experimental setup and between species. The long latency in humans makes it unlikely that it is a directly protective reflex. Instead it may be involved in the updating of motor programs. Further research may characterize the reflex in details and map its pathways. The existence of this reflex indicate that the cruciate ligaments have an afferent function, which influences knee dynamics.

Animals↗