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PubMed2002

Development of dynamic knee stability after acute ACL injury.

Recently, a training program that includes perturbation of support surfaces has been shown to allow most active individuals with ACL injury who pass a screening examination to successfully return to high level activities. The purpose of this study was to identify the effect of this rehabilitation program on involved side muscle activation during walking in subjects with acute ACL rupture and to determine if the activation changes were coincident with improved function. Nine subjects with an acute, unilateral ACL injury or rupture of an ACL graft, who met the screening examination criteria, received ten sessions of rehabilitation that included perturbation training. Motion analysis of five self-paced walking trials were performed before and after training. Electromyographic (EMG) data were collected during stance. After training during walking, the vastus lateralis (VL) integral of activity increased, and relationships between muscles were significantly altered. During walking, VL activation variables were dependent on lateral hamstrings (LH) and/or the soleus (SOL) activation, while no relationships were found before training. Function improved after training, and all subjects returned to their pre-injury activities without experiencing instability. The relationships formed between muscles post-training suggests that perturbation training enhances dynamic knee stability by inducing a well-coordinated strategy among muscles that affect tibial translation.

Activities of Daily Living↗
PubMed2003

Changes in muscle strength and pain in response to surgical repair of posterior abdominal wall disruption followed by rehabilitation.

BACKGROUND: Posterior abdominal wall deficiency (PAWD) is a tear in the external oblique aponeurosis or the conjoint tendon causing a posterior wall defect at the medial end of the inguinal canal. It is often known as sportsman's hernia and is believed to be caused by repetitive stress. OBJECTIVE: To assess lower limb and abdominal muscle strength of patients with PAWD before intervention compared with matched controls; to evaluate any changes following surgical repair and rehabilitation. METHODS: Sixteen subjects were assessed using a questionnaire, isokinetic testing of the lower limb strength, and pressure biofeedback testing of the abdominals. After surgery and a six week rehabilitation programme, the subjects were re-evaluated. A control group were assessed using the same procedure. RESULTS: Quadriceps and hamstrings strength was not affected by this condition. A deficit hip muscle strength was found on the affected limb before surgery, which was significant for the hip flexors (p = 0.05). Before surgery, 87% of the patients compared with 20% of the controls failed the abdominal obliques test. Both the injured and non-injured sides had improved significantly in strength after surgery and rehabilitation. The strength of the abdominal obliques showed the most significant improvement over the course of the rehabilitation programme. CONCLUSIONS: Lower limb muscle strength may have been reduced as the result of disuse atrophy or pain inhibition. Abdominal oblique strength was deficient in the injured patients and this compromises rotational control of the pelvis. More sensitive investigations (such as electromyography) are needed to assess the link between abdominal oblique function and groin injury.

Abdominal Muscles↗
PubMed2002

Effect of a rigid ankle-foot orthosis on hamstring length in children with hemiplegia.

Eighteen children with hemiplegia, mean age 8 years 5 months, underwent gait analysis and musculoskeletal modelling using specially designed software. The maximum lengths of the hamstrings were determined for each child walking in and out of an ankle-foot orthosis (AFO). The muscles were deemed to be short if shorter than the normal average -1SD. In bare feet 8 participants had short medial hamstrings with a higher proportion of these in the less involved individuals. All participants showed an increase in maximum hamstring length when wearing an AFO. In all but one child this was sufficient to restore hamstring length to within normal limits. These finding suggest that hamstring pathology in hemiplegic gait is usually secondary to more distal lower limb pathology.

Ankle Joint↗
PubMed1998

Electromyographic analysis of grand-plié in ballet and modern dancers.

PURPOSE: The purpose of this report is to describe lower extremity muscle activity in grand-plié, as determined by EMG analysis; to compare and contrast muscle function in grand-plié and demi-plié to support the hypothesis that grand-plié is not simply a deeper demi-plié, but rather a fundamentally different movement in terms of muscle use; and to present further evidence in support of the hypothesis that ballet dancers use muscles differently than modern dancers in dance movement. METHODS: Surface electromyography was used to analyze lower extremity muscle activity during grand-plié in first position with lower extremities turned out in five ballet and seven modern female professional dancers. RESULTS: Electromyographic (EMG) activity of tibialis anterior included continuous activity from heel-off during the lowering phase, through midcycle, and ending at heel-on during the rising phase in all grand-pliés; the majority of tibialis anterior EMG tracings in ballet dancers had additional activity at the end of the rising phase. All EMG tracings for vastus lateralis and medialis included a peak of activity during the lowering phase, a decrease (valley) at midcycle, followed by another peak during the rising phase; increased activity at the end of the rising phase was observed in most grand-plié in ballet, and not modern, dancers. Adductor EMG activity was also observed in all tracings with a peak during the lowering phase from heel-off to midcycle, a valley at midcycle, followed by a peak of activity in early rising phase; the midcycle valley was of lower, and the rising phase peak of higher, activity in ballet compared with modern dancers. Variation of EMG patterns was observed for lateral and medial gastrocnemius, gluteus maximus, and hamstrings. CONCLUSIONS: The data support the concept that lower extremity muscle activity in dance movement is comprised of three major types: (a) unique, characteristic activity required for the execution of the movement; (b) varied activity which is characteristic of dancers of different dance idioms; and (c) varied activity which may depend on factors such as balance, personal habit, and individual training background. Furthermore, EMG activity of vastus lateralis and medialis at the midcycle valley in grand-plié was significantly less in ballet dancers than in modern dancers despite similar degree of knee flexion, suggesting that ballet dancers may have lower patellofemoral joint reaction force at midcycle than modern dancers.

Analysis of Variance↗
PubMed2003

Androgen therapy improves muscle mass and strength but not muscle quality: results from two studies.

The relationship of strength to muscle area was used to assess change in muscle quality after anabolic interventions. Study 1: asymptomatic human immunodeficiency virus-positive men (39 +/- 9 yr) were randomized to nandrolone (600 mg/wk) +/- resistance training (RT). Study 2: older healthy men (72 +/- 5 yr) were randomized to oxandrolone (20 mg/day) or placebo. Maximum voluntary strength was determined by the 1-repetition maximum (1-RM) method for leg press, flexion and extension, and cross-sectional area of leg muscles by MRI. From study week 0 to study week 12, muscle quality was unchanged with nandrolone, oxandrolone, or oxandrolone placebo, respectively, for total thigh muscles (1.23 +/- 0.012 vs. 1.27 +/- 0.29 kg/cm2; 9.0 +/- 1.1 vs. 8.9 +/- 1.2 N/cm2; 8.9 +/- 1.2 vs. 8.9 +/- 1.9 N/cm2) and hamstrings (0.41 +/- 0.08 vs. 0.43 +/- 0.07 kg/cm2; 0.90 +/- 0.14 vs. 0.95 +/- 0.016 N/cm2; 0.94 +/- 0.23 vs. 0.93 +/- 0.21 N/cm2). Lower-extremity 1-RM strength increased several times greater with RT+nandrolone (51-63% increases) than with nandrolone alone (4.7-16%), despite similar increases in muscle area; therefore, muscle quality increased from 1.13 +/- 0.17 to 1.51 +/- 0.18 kg/cm2 (+36 +/- 19%; P < 0.001) for total thigh muscle, 0.37 +/- 0.10 to 0.53 +/- 0.08 kg/cm2 (+49 +/- 39%; P < 0.001) for hamstrings, and 0.73 +/- 0.19 to 1.07 +/- 0.16 kg/cm2 (+55 +/- 36%; P < 0.001) for quadriceps. Thus androgen therapy alone did not improve muscle quality, but the addition of RT to nandrolone produced substantive improvements.

Aged↗
PubMed1995

Hamstring injuries: radiographic, conventional tomographic, CT, and MR imaging characteristics.

PURPOSE: To review experience with the imaging features of hamstring injuries. MATERIALS AND METHODS: Imaging findings in 18 male and four female patients with clinically proved hamstring injuries were reviewed. The patients' ages ranged from 13 to 61 years (mean, 26 years). Radiography, conventional tomography, computed tomography (CT), and magnetic resonance (MR) imaging were performed. RESULTS: Plain radiographs obtained less than 1 week after injury were normal or showed avulsion of an ischial apophysis. Plain radiographs and conventional tomograms obtained more than 1 week but less than 3 months after injury were confusing, because callus and osteolysis were present. CT helped identify a healing avulsion of an ischial apophysis. MR imaging was helpful no matter how long after the injury it was performed. It provided a means to evaluate muscle, tendon, and bone. CONCLUSION: Familiarity with the variable appearance of hamstring injuries over time and with different modalities facilitates accurate characterization.

Adolescent↗
PubMedDate not supplied

Intramuscular corticosteroid injection for hamstring injuries. A 13-year experience in the National Football League.

The purpose of this study was to assess the safety of intramuscular corticosteroid injection in selected, severe hamstring injuries in professional football players. Clinicians have been reluctant to use corticosteroid injections in or around muscle-tendon units because of concern of incomplete healing or rupture. We retrospectively reviewed the computer database of one National Football League team for all hamstring injuries requiring treatment between January 1985 and January 1998. We found that 431 players had suffered such injury. We developed a clinical grading system to identify hamstring injury severity and to stratify players for treatment. Fifty-eight players (13%) sustained severe, discrete injuries with a palpable defect within the substance of the muscle and were treated with intramuscular injection of corticosteroid and anesthetic. There were no complications related to the injection of corticosteroid. Only nine players (16%) missed any games as a result of their injury. Final examination revealed no strength deficits, normal muscle bulk and tone, and the ability to generate normal power. We believe that the grading system we developed can assist in selection of injury type for injection. Although lack of a control group limits statements of efficacy of injection, our impression is that intramuscular corticosteroid injection hastens players' return to full play and lessens the game and practice time they miss.

Adult↗
PubMed1999

In vivo determination of the patella tendon and hamstrings moment arms in adult males using videofluoroscopy during submaximal knee extension and flexion.

OBJECTIVE: The determination of patella tendon and hamstrings moment arms. DESIGN: The moment-arms were determined using a videofluoroscopy imaging method. BACKGROUND: The determination of hamstrings and quadriceps moment arms is important for the examination of muscle and joint forces in biomechanical applications. METHODS: Ten males performed one knee extension-flexion movement at a very slow (non-constant) angular velocity in front of the image intensifier screen of a videofluoroscopic system. The image of a calibration phantom with 2 cm squares was also recorded. Thirty five calibration points with known coordinates were digitized for the establishment of the polynomial equations that determined the coordinates of any point in the calibration phantom from its corresponding video coordinates. Fourteen control points were digitized and the difference between the actual and predicted coordinates was measured. The patella tendon and hamstrings (biceps femoris) moment arms to the tibiofemoral contract point were calculated. RESULTS: The mean error in the digitizing of the control points using the image deformation method ranged from 0.182 mm to 0.267 mm. The mean patella tendon moment arm ranged from 36.91 (SD 3.2) mm to 42.63 (SD 4.5) mm. The hamstrings moment arm ranged from 23.93 (SD 2.59) to 28.25 (SD 3.04) mm. CONCLUSION: The patellar tendon and hamstring moment-arms were determined using a videofluoroscopy method with acceptable accuracy. These parameters can be used for the biomechanical analysis of knee joint movements in two dimensional applications.

Adult↗
PubMed2005

Central somatosensory changes and altered muscle synergies in subjects with anterior cruciate ligament deficiency.

To clarify the mechanisms of compensation in subjects with anterior cruciate ligament deficiency (ACL-D), we examined proprioception, quadriceps strength, somatosensory evoked potentials (SEPs) and muscle responses during gait in varied combinations of speed and incline. Seventeen subjects with ACL-D were grouped by functional level and report of giving way. Seven subjects without ACL-D served as a control sample for muscle response measures. ACL-D subjects with quadriceps weakness experienced giving way and could not resume sport activities. Those without weakness fell into one of two groups: (1) copers, who had full return to previous activity and no giving way despite proprioceptive loss and altered SEPs, and (2) adapters, who were unable to return to previous activity level and experienced giving way despite neither proprioceptive loss or altered SEPs. The unique muscle pattern in copers during inclined fast walking included larger and earlier hamstring activation. These results suggest that in individuals with ACL-D without a strength deficit, altered SEPs and altered neuromuscular patterns are the factors that enable resumption of pre-injury functional levels. Loss of proprioception may drive the central changes, which in turn drives the development of altered muscle patterns.

Adaptation, Physiological↗
PubMed1991

Thigh muscle function after partial tear of the medial ligament compartment of the knee.

The purpose of the study was to assess the isokinetic and isometric strength and power profile of the knees of 48 patients who had a previous second-degree sprain (partial tear) of the medial ligament compartment, the most common knee ligament injury in sports. The CYBEX II isokinetic dynamometer was used in the measurements. On an average of 8 yr after the injury, the mean strength deficit of the injured knees was minimal: 4 +/- 5% (range 0-28%) in extension and 2 +/- 4% (0-20%) in flexion. The average strength score (max. 100 points) was 90 +/- 11 (56-100), representing an excellent classification. In hamstrings, the relative strength deficit increased significantly with a higher speed of isokinetic movement (P less than 0.05). Compared with the strength parameters (peak torques), the other functional parameters of the injured knees (total work, average power, and peak torque acceleration energy) showed some but not significantly greater deficits (hamstrings 9-11%, quadriceps 6-8%). In conclusion, the general thigh muscle function in knees with old second-degree sprain of the medial ligament compartment appears good and acceptable, but the strength deficits are systematically greater in higher speeds of isokinetic movement. Therefore, rehabilitation utilizing high speed extension and flexion exercises is recommended.

Adolescent↗
PubMed1997

The effects of antagonist moment on the resultant knee joint moment during isokinetic testing of the knee extensors.

The purpose of this study was to examine the effects of moment of antagonistic muscle on the resultant joint moment during isokinetic eccentric and concentric efforts of the knee extensors. Ten males performed maximum eccentric and concentric knee extension and flexion efforts on a Biodex dynamometer at 0.52 rad.s-1 (30 degrees.s-1). Electromyographic (EMG) activity of vastus medialis and biceps femoris (hamstrings) was also recorded. The antagonistic moment of the hamstrings was determined by recording the integrated EMG (iEMG)/ moment relationship at different levels of muscle effort. The iEMG/moment curves were fitted using second-degree polynomials. The polynomials were then used to predict the antagonistic moment exerted by the hamstrings from the antagonist iEMG. The antagonistic moment had a maximum of 42.92 Nm and 28.97 Nm under concentric and eccentric conditions respectively; paired t-tests indicated that this was a significant difference (P < 0.05). These results indicate that the resultant joint moment of knee extensors is the result of both agonist and antagonist muscle activation. The greater antagonist muscle activity under concentric activation conditions may be partly responsible for the lower resultant joint concentric moment of knee extensors compared with the corresponding eccentric activation. The antagonist moment significantly affects comparisons between the isokinetic moments and agonist EMG and in vitro force measurements under different testing (muscle action and angular velocity) conditions.

Adult↗
PubMed2006

Duration of stretch does not influence the degree of force loss following static stretching.

AIM: There is an emerging body of knowledge indicating static stretching (SS) acutely and adversely affects muscle performance. The practical value of this research is limited considering the lengthy stretch durations under investigation. It is unclear if stretch durations typical of those used pre-exercise similarly affect muscle performance. The purpose of this study was to determine if SS using more representative stretch durations affects muscle performance and to establish if changes in muscle performance were influenced by the duration of stretch. METHODS: Following 2 familiarization sessions, 16 recreationally trained males and females participated in 2 randomly ordered experimental sessions. In each session maximal effort hamstring performance was assessed prior to and immediately after 1 of 2 stretching protocols. During one of the protocols participants were required to hold each stretch for 15 s while stretch duration in the second protocol was 30 s. Both protocols consisted of 3 repetitions of 2 stretching exercises. A Kincom isokinetic dynamometer was used to assess hamstring performance during isometric, concentric, and eccentric actions. RESULTS: For each of the three muscle actions a repeated measures ANOVA revealed a significant main effect of time (pre- vs poststretch, P<0.05) but no interaction effect (time x SS protocol). Furthermore, the stretch-induced deficits in muscle performance were consistent across muscle action type. CONCLUSIONS: SS incorporating stretch durations typical of those employed pre-exercise were sufficient to impair muscle performance and the duration of stretch did not influence the degree of force loss. Inclusion of SS, even with short stretch durations, in preparation for strength activities is not appropriate.

Adult↗
PubMed1993

[Skeletal and respiratory muscle strength in chronic heart failure].

BACKGROUND: The aim of this study was to investigate limb and respiratory muscle strength in chronic heart failure (CHF). METHODS: Our study population consisted of 45 male CHF patients, 25 in NYHA Class II and 20 in NYHA Class III, and 22 male post-MI patients without left ventricular dysfunction (LVEF > 50%). All patients underwent assessment of respiratory muscle strength by maximal inspiratory (MIP) and expiratory (MEP) pressures, of handgrip force and peak torque developed during isokinetic Knee extension (EX) (quadriceps) and flexion (hamstring) at 120 degrees/sec. RESULTS: CHF patients showed a significant decrease in all limb and respiratory muscle strength compared to control patients. Moreover, NYHA Class III patients showed significantly reduced values of MIP, handgrip, and EX forces, as well as significantly reduced exercise tolerance in terms of METS (2.8 +/- 0.9 vs 4.4 +/- 1.2, p < .05) and anaerobic threshold level (9.4 +/- 3 vs 12.8 +/- 1.7 mlO2/Kg, p < .05), as compared to those patients in NYHA Class II, while no significant differences were observed in LVEF, cardiac index and pulmonary capillary wedge pressures. Weak, but significant (p < .05) were the correlations between limb muscle and respiratory muscle strength. No correlations were found between muscle force and hemodynamic parameters. Significant correlations (from p < .05 to p < .0001) were found among exercise tolerance and limb muscle strength, but not between exercise tolerance and respiratory muscle strength. In summary: 1) respiratory and skeletal muscle strength is impaired in CHF; 2) respiratory and limb muscle strength reductions are partially related to each other; 3) the degree of central hemodynamic impairment is not correlated with muscle force. Deconditioning could be a major determinant of skeletal but not respiratory muscle weakness. Other factors link limb and respiratory weakness in CHF.

Adult↗
PubMed2002

The effects of ACL injury on quadriceps and hamstring torque, work and power.

The aim of this study was to assess isokinetic torque, work and power between non-injured, ACL (anterior cruciate ligament)-deficient and ACL-reconstructed individuals. Ten healthy, non-injured individuals, seven unilateral ACL-deficient individuals and six unilateral ACL-reconstructed individuals were assessed for isokinetic quadriceps and hamstring strength at 1.05 and 3.14 rad.s-1. Peak torque, total work, average power and the ratio of peak torque to body mass were computed for both velocities. Peak torque was also corrected for body mass, using allometric modelling. The non-injured individuals showed significantly greater quadriceps peak torque to body mass ratios than the ACL-deficient and ACL-reconstructed individuals at both velocities, and greater hamstring peak torque to body mass ratios than the ACL-deficient group at 3.14 rad.s-1 (P < 0.05). The ACL-deficient individuals displayed greater quadriceps and hamstring peak torque, total work and average power than the non-injured individuals at 1.05 rad.s-1 (P < 0.05). The ACL-deficient individuals also displayed significantly greater peak torque, total work and average power than the ACL-reconstructed individuals for the quadriceps at both velocities (P < 0.05). The ACL-deficient individuals demonstrated greater hamstring peak torque and total work than the non-injured individuals at both velocities (P < 0.05). The allometrically modelled peak torques at both isokinetic velocities demonstrated that the quadriceps muscle values were significantly higher in the non-involved than the involved limb. The hamstring peak torques corrected for body mass were significantly higher in the non-involved than the involved limb only at 1.05 rad.s-1. The main finding from the present study is that isokinetic measures in ratio-scaled or absolute units yield a different outcome and, hence, interpretation compared with the allometric approach.

Adult↗
PubMed1983

Knee load and muscle activity during exercises in rising.

Knee joint loading and the level of knee muscle activation during rising exercises have been evaluated and methods have been developed for such studies. Floor-to-foot forces were recorded using a force-measuring platform. The loading moment of force representing the resistance for the knee joint was calculated. It was shown that the initial knee loading moment with much flexed knees was high at large knee angles. The loading moment showed a marked decrease with decreasing knee angles. For small knee angles there was no resistance to knee extension. Muscular activity level was studied using EMG. The levels of activity in the quadriceps muscles were high at large knee angles and low at small angles. The hamstrings and gastrocnemius showed only low activity. The magnitude of change in knee extension resistance due to adaptive adjustment of the exercise device was mapped. These rising exercises will increase strength mainly for large knee angles and only for quadriceps muscles.

Adult↗
PubMed1995

[Electromyographic findings in muscles around the osteoarthritic knee: integrated electromyography and frequency analysis].

An evaluation of the muscular functions of the vastus medialis, vastus lateralis, rectus femoris, medial hamstring, and of the lateral hamstring was performed using electromyography in 33 knees of 26 female patients with osteoarthritis (OA group) and in 25 knees of 19 healthy female volunteers (control group). During standing on both feet, all muscles in the OA group showed higher IEMG (integrated electromyography) and higher LMR (IEMG of vastus lateralis/IEMG of vastus medialis ratio in the quadriceps; and lateral hamstring/medial hamstring ratio in the hamstrings) than the control group. These augmentary muscular activities ameliorated the varus deformity caused by the osteoarthritis. During maximum isometric voluntary contraction, the OA group showed lower extension and flexion torque of the knees and also lower IEMG than to the control group, while the IEMG of vastus lateralis was not lower. These findings indicated decreased muscular activities in the osteoarthritic knee, and that the activity of the quadriceps was maintained mainly by the vastus lateralis under such conditions. Frequency analysis of the myoelectric signal during maximum isometric voluntary contraction revealed a single peak of low frequency in the power spectrum density function of the quadriceps and double peaks of low and of high frequency in the hamstring. In the OA group, the peak height of the low frequency component was increased in the quadriceps and decreased in the hamstring. We concluded that the duration of the motor unit action potentials was affected in the osteoarthritic knee.

Aged↗
PubMed1985

[Muscle exercise after the anterior cruciate ligament reconstruction of the knee--Part I: The force given to the anterior cruciate ligament by separate isometric contraction of the quadriceps or the hamstrings].

UNLABELLED: An attempt was made to investigate the force of the anterior cruciate ligament (ACL) in separate isometric contraction (IMC) of the quadriceps and the hamstrings by means of the analysis of two-dimensional models. In IMC of the quadriceps, the average value of the anterior drawer force (ADF) was equal to 14% of the quadriceps tension at the knee flexion of 5 degrees. The ADF decreased as the flexion angle increased. The average value of the angles, where the ADF became zero, was 45.3 degrees, and the standard deviation was 12.5 degrees. In IMC of the hamstrings, the posterior drawer force was given at the every flexion angle. CLINICAL RELEVANCE: In the early stage of the rehabilitation after the ACL reconstruction, the quadriceps exercise by IMC should be performed at the knee flexion of more than 70 degrees (average + 1.96 X S.D.). The hamstrings exercise by IMC can be carried out regardless of flexion angle.

Adult↗