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PubMed1989

Isokinetic peak torque and work relationship in the laterally unstable knee.

The purpose of this investigation was to assess the relationship between the isometric and isokinetic peak torque (speed of movement 0 degrees, 60 degrees, and 180 degrees/s) and the total work output of multiple contractions (180 degrees/s) of the quadriceps and hamstrings in subjects suffering from a chronic insufficiency of the lateral ligament compartment (LAT) of the knee. At every test speed the Pearson product moment (r) and the Spearman rank (rs) correlation coefficients between the peak torque and total work were highly significant for both muscle groups in the uninjured (r = .87-.97, rs = .86-.93) as well as in the laterally unstable (r = .65-.90, rs = .71-.90) knees. In both knees and in both muscle groups the correlation coefficients increased towards the highest speed of the isokinetic movement, obviously since the total work was registered at that speed. In conclusion, concerning laterally unstable knees the total work analysis may offer little additional information to that attained by more simple measurement, the peak torque analysis.

Adult↗

PubMed1998

Strain on the gastrocnemii and hamstrings affecting standing balance on an inclined plane in spastic cerebral palsy. A study using a geometric model.

The purpose of this study was to use an non-invasive method to determine whether strain on the gastrocnemii and hamstrings influences postural balance in spastic cerebral palsy (CP). Changes in alignment during standing posture with subjects positioned on a platform that was gradually inclined were measured in 10 normal children and 11 children with CP. The changes in postural alignment were plotted and geometric models used to determine the lines where the gastrocnemii and hamstrings were maximally stretched. In this way the relationship between postural alignment and the amount of strain on the gastrocnemii and hamstrings was investigated. On the inclined platform, which caused ankle joints to become dorsiflexed as the inclination angle increased, the gastrocnemii began to be strained and the hip joints began to be flexed (trunk bent forward) at the same time. In the children with CP, the gastrocnemii were more strained by smaller degrees of inclination. Furthermore, there was one child with CP whose hamstrings were also strained on the inclined platform. We confirmed that postural balance was affected by strain on the gastrocnemii and hamstrings.

Accidental Falls↗

PubMed2001

A comparison of outcomes at 2 to 6 years after acute and chronic anterior cruciate ligament reconstructions using hamstring tendon grafts.

PURPOSE: To compare short- to intermediate-term outcomes of patients in whom an acute or chronic anterior cruciate ligament (ACL) reconstruction was performed with a hamstring tendon graft. TYPE OF STUDY: A consecutive case series of patients who had 2-incision, arthroscopically assisted ACL reconstructions with a triple-strand hamstring tendon graft was retrospectively evaluated. METHODS: A total of 120 patients were evaluated at a mean of 44 months. The Tegner Activity Scale, individual components of the Cincinnati Knee Rating System, and the modified Lysholm Score were administered to all patients. A total of 93 patients (78%) returned for examination, instrumented ligament laxity testing, radiographs, isokinetic strength testing, and completion of the IKDC Standard Knee Ligament Evaluation Form. Data from patients undergoing reconstructions for acute and chronic ACL deficiencies were compared. The acute group was defined as reconstruction within 6 weeks of injury without recurrent episodes of instability. RESULTS: At surgery, significantly more (P <.05) cartilage abnormalities and partial medial menisectomies were found in the chronic group. At final follow-up, no significant differences (P >.05) were found between the acute and chronic groups for instrumented laxity, muscle strength, knee motion, or sports activity level. The acute group scored significantly higher (P <.05) on the Lysholm scale, Cincinnati Function scale, IKDC subjective assessment, and IKDC rating for pain at follow-up. The final IKDC grade resulted in significantly more (P =.039) normal knees for the acute group; however, 94.1% of acute and 92.9% of chronic knees were graded normal or nearly normal. CONCLUSIONS: Hamstring tendons are an excellent graft choice for ACL reconstruction in both acute and chronic injuries. According to the strict IKDC rating system, greater than 90% of all patients can be expected to have a normal or nearly normal knee at short- to intermediate-term follow-up; however, the chronic group will have fewer patients with a rating of normal.

Anterior Cruciate Ligament↗

PubMed1994

Effects of stair-stepping exercise direction and cadence on EMG activity of selected lower extremity muscle groups.

Step ergometry has become a popular treatment mode in cardiovascular fitness and knee rehabilitation programs. The following study describes the effects of forward stair stepping at 35 and 95 steps/minute and forward and retrograde stair stepping at 60 steps/minute on the mean electromyographic (EMG) activity of the gluteus maximus, rectus femoris, vastus medialis, semimembranosus/semitendinosus, and gastrocnemius muscles. Thirty-three subjects without prior lower extremity pathology participated in the study. Analysis of variance was used to compare mean EMG activity during the knee extension phase of the different stepping conditions. Significant differences (p < 0.05) in mean EMGs of gluteus maximus, rectus femoris, vastus medialis, and gastrocnemius were noted across all cadences. The semimembranosus/semitendinosus EMG activity displayed a single significant difference between the cadences of 35 and 95. The comparison between forward and retrograde stepping identified only one significant difference in mean EMG (semimembranosus/semitendinosus). The effects of cadence on EMG activity should be considered when developing conditioning or rehabilitation programs for the lower extremity. Faster cadences result in increased peak activity of shorter duration for the gluteus maximus, quadriceps, and gastrocnemius. There is no apparent difference in EMG activity of the hamstrings due to cadence. Also, noting the minimal activation that occurs, stair-stepping exercise would not be recommended for strengthening of the hamstrings musculature.

Adolescent↗

PubMed1989

The role of preseason conditioning in preventing athletic injuries.

The role of preseason conditioning in injury prevention was discussed in this article. Evidence was presented that conditioning involving flexibility, cardiovascular work, and resistance training contributed to the structural integrity of the joint as well as the muscle-tendon unit. The effect these physiologic adaptions had on the prevention of injuries was investigated. Epidemiological studies were reviewed to ascertain this effect and were found to carry methodological problems that made conclusions questionable. Further epidemiological research was recommended with suggested design modifications to produce valid conclusions. Even though there is a lack of empirical evidence relating preseason conditioning to injury prevention, many studies were reviewed that showed a clear connection between many specific training techniques that are used to prevent injury. The role of flexibility and resistance training in the prevention of hamstring strains was particularly emphasized. The application of preseason conditioning toward preventing injury was then discussed. It was recommended that a preseason evaluation precede this conditioning so that the sports medicine evaluator could assess the athlete's level of conditioning. Based on the strengths and weaknesses of this evaluation a preseason conditioning program could be devised. The elements of such a program were then presented with a summary of preseason training techniques. Specificity of testing and training was recommended. The closer that athletes come to testing and training for the muscle function needed in their sport, the greater the chance of increased performance. In addition, a more specific and adequate muscle function was thought to help in the prevention of injuries.

Athletic Injuries↗

PubMed2001

Hamstrings vs. patella tendon for anterior cruciate ligament reconstruction: a randomised controlled trial.

A randomised controlled trial was performed to evaluate early outcome for two types of anterior cruciate ligament reconstruction. Sixty patients undergoing cruciate reconstruction were randomized into two groups. Group PT underwent reconstruction using a patella tendon autograft, whereas Group (SG) had a semitendinosus/gracilis autograft (SG). IKDC, Lysholm, and Tegner scores, KT1000 values and muscle strength were recorded pre-operatively, at 6 months and 1 year follow up. The functional scores, activity level, muscle strength and anterior tibial translation improved in both groups. No significant difference between groups was found for any measurement at 6 months and 1 year despite adequate study power. The study indicates that the 1 year results for either technique are equally favourable.

Analysis of Variance↗

PubMed2001

Facilitation of quadriceps activation following a concentrically controlled knee flexion movement: the influence of transition rate.

STUDY DESIGN: Single group repeated measures design. OBJECTIVE: To determine if the rate of transition between knee flexion and extension influences the subsequent concentric activation of the quadriceps and knee extension torque during reciprocal movements. BACKGROUND: Preloading a muscle by stretching, a prior isometric or eccentric muscle action, or a prior movement controlled concentrically by the antagonist muscle group increases the maximal torque-generating capability of the agonist. We hypothesized that the rate of transition from the prior movement may be the critical factor that influences the degree of muscle facilitation and torque potentiation. Rapid reversal of antagonistic movements has been postulated as a potential facilitatory mechanism. METHODS: Knee extension torque and electromyographic (EMG) amplitude (dependent variables) from 2 of the vasti muscles were recorded while subjects (N = 20; 12 men, 8 women, mean age, 28.5+/-2.68 years) maximally activated their quadriceps at 3 constant angular velocities, 100 degrees/s, 200 degrees/s, and 300 degrees/s, and 2 preload conditions, SLOW and RAPID (independent variables). In the SLOW transition condition, subjects actively flexed their knee to 110 degrees from an extended position, paused in this position for 3 seconds, and then extended to 0 degrees. In the RAPID transition condition, the same movement from knee flexion to extension was performed without a pause. RESULTS: Peak torque, the root-mean-square (RMS) average, peak (peak rectified and smoothed), and initial (100 milliseconds prior to torque onset) EMG amplitudes were all significantly greater during the RAPID transition condition. Peak torque decreased with increasing movement velocity. There were no interactions between the preload conditions and angular velocity on peak torque or the EMG amplitude variables. There was also no influence of velocity on the EMG amplitude variables. CONCLUSIONS: The effect of preloading the quadriceps by prior concentric activation of the hamstrings is dependent on the rate of transition between the flexion and extension movements and is due primarily to neural facilitation.

Adult↗

PubMed1975

The ischium and hip extensor mechanism in human evolution.

Although it is commonly stated that the ischia of the late Pliocence-early Pleistocene hominid fossils are long and ape-like, new interpretations show this view to be falacious. An important new theory proposed by Robinson concludes that the gracile form of early hominid was an efficient biped, but the robust form was a less efficient biped and was adapted for tree climbing. Interpretation of the ischium is crucial to this idea. The present study shows that (1) the gracile and robust australopithecine ischia had similar relative lenths and (2) that the hamstring mechanism was probably very similar in the two forms of South African early hominid.

Acetabulum↗

PubMed2005

Isokinetic and anterior cruciate ligament reconstruction with hamstrings or patella tendon graft: analysis of literature.

We report isokinetic results of anterior cruciate ligament reconstruction with patellar tendon or hamstring graft from the literature analysis. The literature was defined from two search "textwords": Isokinetic and Anterior cruciate ligament reconstruction, and from three databases: Medline, Pascal, and Herasmus. Two independent physicians (Physical Medicine and Rehabilitation) carried out an analysis according to the French National Accreditation and Health Evaluation Agency recommendations. Fifty-three studies were selected: 29 reported isokinetic results after anterior cruciate ligament reconstruction with patellar tendon graft, 15 reported isokinetic results after anterior cruciate ligament reconstruction with hamstring graft, and 9 studies compared the two surgical procedures. After discussing different bias and in reference to prospective randomised and comparative studies, the anterior cruciate ligament reconstruction with patellar tendon graft involves a knee extensors deficit during several months. The hamstring surgical procedure involves a less important knee extensor deficit (from 6 to 19 % against 8 to 21 %). Knee sprain and intra-articular surgery involve a long-lasting knee extensors deficit. Anterior cruciate ligament reconstruction with hamstrings graft involves a knee flexors deficit over several months. The patellar tendon surgical procedure involves a less important knee flexors deficit (from 1 to 15 % against 5 to 17 %). In reference to isokinetic parameters, no difference between the two surgical procedures (patellar tendon graft or hamstring graft) is shown after more than twenty-four post-surgical months.

Anterior Cruciate Ligament↗

PubMed2001

A comparison of knee joint motion patterns between men and women in selected athletic tasks.

BACKGROUND: Women have higher non-contact anterior cruciate ligament injury rate than men do in sport activities. Non-contact anterior cruciate ligament injuries frequently occur in sports requiring cutting tasks. Alternated motor control strategies have identified as a potential risk factor for the non-contact anterior cruciate ligament injuries. The purpose of this study was to compare the patterns of knee kinematics and electromyographic activities in running, side-cutting, and cross-cutting between men and women recreational athletes. METHODS: Three-dimensional kinematic data of the knee and electromyographic data of selected muscles across the knee joint were collected for 11 men and 9 women recreational athletes in running, side-cutting, and cross-cutting. Regression analyses with dummy variables for comparison of knee motion patterns between men and women. RESULTS: Women tend to have less knee flexion angles, more knee valgus angles, greater quadriceps activation, and lower hamstring activation in comparison to men during the stance phase of each of the three athletic tasks. Literatures suggest these alternated knee motion patterns of women tend to increase the load on the anterior cruciate ligament. CONCLUSION: Women on average may have certain motor control strategies that may alter their knee motion patterns. Women's altered knee motion patterns may tend to increase the load on the anterior cruciate ligament in the selected athletic tasks, which may contribute to the increased anterior cruciate ligament injury rate among women. RELEVANCE: Non-contact anterior cruciate ligament injuries frequently occur in sports. Altered motor control strategies and lower extremity motion patterns are likely to play an important role in non-contact anterior cruciate ligament injuries. Non-contact anterior cruciate ligament injuries may be prevented by correcting altered motor control strategies and associated lower extremity motion patterns through certain training programs.

Electromyography↗

PubMed1998

Reduced quadriceps strength relative to body weight: a risk factor for knee osteoarthritis in women?

OBJECTIVE: To determine whether baseline lower extremity muscle weakness is a risk factor for incident radiographic osteoarthritis (OA) of the knee. METHODS: This prospective study involved 342 elderly community-dwelling subjects (178 women, 164 men) from central Indiana, for whom baseline and followup (mean interval 31.3 months) knee radiographs were available. Lower extremity muscle strength was measured by isokinetic dynamometry and lean tissue (i.e., muscle) mass in the lower extremities by dual x-ray absorptiometry. RESULTS: Knee OA was associated with an increase in body weight in women (P = 0.0014), but not in men. In both sexes, lower extremity muscle mass exhibited a strong positive correlation with body weight. In women, after adjustment for body weight, knee extensor strength was 18% lower at baseline among subjects who developed incident knee OA than among the controls (P = 0.053), whereas after adjustment for lower extremity muscle mass, knee extensor strength was 15% lower than in the controls (P not significant). In men, in contrast, adjusted knee extensor strength at baseline was comparable to that in the controls. Among the 13 women who developed incident OA, there was a strong, highly significant negative correlation between body weight and extensor strength (r = -0.740, P = 0.003), that is, the more obese the subject, the greater the reduction of quadriceps strength. In contrast, among the 14 men who developed incident OA, a modest positive correlation existed between weight and quadriceps strength (r = 0.455, P = 0.058). No correlation between knee flexor (hamstring) strength and knee OA was seen in either sex. CONCLUSION: Reduced quadriceps strength relative to body weight may be a risk factor for knee OA in women.

Aged↗

PubMed1997

Muscle selection and walking performance of multichannel FES systems for ambulation in paraplegia.

A minimal set of muscles (8 to 16) were identified as candidates for implantation in a clinical system to provide walking function to individuals with complete paraplegia using functional electrical stimulation (FES). Three subjects with complete motor and sensory paraplegia had percutaneous intramuscular electrodes implanted in all major muscles controlling the trunk, hips, knees, and ankles. Stimulation patterns for walking with FES were generated for different sets of eight and 16 muscles. The quality and repeatability of the resulting gait produced by walking patterns consisting of various combinations of muscles were determined. Most eight-channel stimulation patterns resulted in scissoring or insufficient hip flexion, preventing forward progression. One eight-channel system allowed a maximum speed of 0.1 m/s with a cadence of 22 steps/min and a stride length less than 0.3 m. Improved walking performance was observed with 16 channels of stimulation. This ranged from slow step- to gait at 0.1 m/s to smooth reciprocal gait at 0.5 m/s. In all three subjects, the favored combination of 16 channels included erector spinae for trunk extension; gluteus maximus, posterior portion of adductor magnus and hamstrings for hip extension; tensor fasciae latae and either sartorius or iliopsoas for hip flexion; vastus lateralis/intermedius for knee extension; and tibialis anterior/peroneous longus for ankle dorsiflexion. In one subject the 16-channel FES system provided repeatable day-to-day gait averaging 0.4 m/s, 58 steps/min and a stride length at 0.8 m. A maximum repeatable walking distance with 16 channels was 34 m. Multiple 34-m trials were possible with minimal rests between walks. Fatigue of both the hip extensors and upper body was a limiting factor. The selection of target muscles for implantation is critical to the performance of FES systems. This study provides guidelines to muscle selection for walking with FES based on objective measures of gait performance. The findings indicate that a 16-channel FES system for total implantation is feasible for repeatable short distance, independent, walker-support walking in paraplegia.

Adult↗

PubMed2002

Muscle response while holding an unstable load.

OBJECTIVE: Basic biomechanical measurement was applied to explore the physical risk associated with holding an unstable load. DESIGN: We investigated muscle response, before and after the initiation of the balance-recovery responses from perturbation when handling unstable loads. BACKGROUND: Most studies of muscle response and postural control during load handling focused on stable (fixed) loads. Investigation of muscle response while handling an unstable load deserves similar attention. METHODS: Twelve male subjects experienced time-variant loads (18 kg), with additional sudden 12 kgm/s impact momentum, under three different load-shift conditions (stable, posterior-to-anterior rolling, or anterior-to-posterior rolling load), and in three foot placements (straddle, wide, and narrow stance). Normalized electromyography (expressed as percentage of maximum voluntary contraction) for the brachioradialis, biceps, erector spinae, and hamstrings were measured. RESULTS: The maximal exertions for brachioradialis (91.0%) and biceps (42.5%) were observed approximately 0.1 s after posterior-to-anterior impact, with maximal measured contractions for erector spinae (57.2%) and hamstrings (59.9%) noted approximately 0.2 s after impact. CONCLUSIONS; The central nervous system detects and responds to the need to stabilize the joints close to the location of load-shift perturbation, with these responses determined according to the anatomical and functional limitation of each biomechanical link. RELEVANCE: Handling shifting loads, impact loading and sudden-unexpected loading may be more damaging to the musculoskeletal system than handling stable loads.

Adult↗

PubMed2003

Management of muscle and tendon injuries in footballers.

BACKGROUND: Muscle and tendon injuries are among the commonest football injuries and can be very frustrating to treat because of the high risk of recurrence. OBJECTIVE: This article aims to highlight the optimal management of, and risk factor for re-injury of, the common soft tissue injuries in football players. DISCUSSION: The high risk of recurrence of soft tissue injuries is because most football players return to play before complete healing of the injury. For hamstring and quadriceps strains and thigh haematomas, early return is often a sensible strategy. Calf strains in older players and tendinopathies (Achilles, patellar tendon and chronic groin injuries) generally require a more conservative approach as the risk of prolonged missed playing time is greater. The rupture of tendons that have nearby agonists can often be managed conservatively, but rupture of isolated prime mover tendons, such as the Achilles and patellar tendons, should be managed surgically.

Anterior Cruciate Ligament Injuries↗

PubMed1996

Peak torque, average power, and hamstrings/quadriceps ratios in nondisabled adults and adults with mental retardation.

OBJECTIVE: To compare isokinetic hamstring and quadriceps peak torque (Nm), average power (watts), and corresponding hamstring/quadriceps (HQ) ratios (as percentages) of adult men with Down syndrome(DS), with mental retardation without Down syndrome (NDS), and nondisabled sedentary controls (SC). DESIGN: Repeated measures analysis of variance. SETTING: Subjects were tested at a university exercise science laboratory. SUBJECTS: Volunteer sample of 35 subjects: SC(n=13), DS(n=9), and NDS (n=13). INTERVENTION: Subjects performed isokinetic strength tests at 60 degrees /sec and 90 degrees/sec using gravity effected torque procedures. Subjects with DS and NDS performed the test on two separate days with best results selected for statistical comparisons. Sedentary controls performed the test once. MAIN OUTCOME MEASURES: Isokinetic hamstring and quadriceps peak torque and average power, and corresponding HQ ratios on a Cybex 340 isokinetic dynamometer. RESULTS: In all isokinetic parameters measured, sedentary controls demonstrated significantly higher scores than subjects with DS and NDS. There was no significant difference between subjects with DS and NDS, although mean peak torque and average power scores were greater in subjects with NDS. Finally, there were no significant differences in peak torque and average power HQ ratios across groups (p> .01), although group mean peak torque HQ ratios were greatest for sedentary controls (range=61% to 63%) and approximated accepted HQ ratio norms, and lowest for subjects with DS(range=40% to 46%). CONCLUSIONS: Individuals with mental retardation are in need of progressive resistance exercise programs to improve hamstring and quadriceps strength and normalize HQ strength and power ratios.

Adult↗

PubMed1994

Endoscopic electrode implantation for enhanced stimulation of the hamstring branches of the sciatic nerve in paralyzed subjects.

Seven hamstring branches of the sciatic nerves in eight posterior thighs of four paraplegics were implanted with electrodes endoscopically. Strong initial responses were obtained in each case on continuous electrical stimulation. Three of the implants were removed immediately due to rapid decay in the response to stimulation; two had muscle power reduced to grade IV and two to grade III over 2-week period postoperatively. We believe the reduction in strength was partly due to hematoma surrounding the electrode and partly due to migration of the electrode away from the target nerves. Further work needs to be done to improve the technique and implant designs to improve results. Due to the excellent visual control it offers, this technique has the potential for accurate implantation of electrodes without massive exposures and its attendant morbidity.

Arthroscopy↗

PubMed2004

Effect of submaximal contraction intensity in contract-relax proprioceptive neuromuscular facilitation stretching.

OBJECTIVE: To determine if submaximal contractions used in contract-relax proprioceptive neuromuscular facilitation (CRPNF) stretching of the hamstrings yield comparable gains in hamstring flexibility to maximal voluntary isometric contractions (MVICs). METHOD: Randomised controlled trial. A convenience sample of 72 male subjects aged 18-27 was used. Subjects qualified by demonstrating tight hamstrings, defined as the inability to reach 70 degrees of hip flexion during a straight leg raise. Sixty subjects were randomly assigned to one of three treatment groups: 1, 20% of MVIC; 2, 60% of MVIC; 3, 100% MVIC. Twelve subjects were randomly assigned to a control group (no stretching). Subjects in groups 1-3 performed three separate six second CRPNF stretches at the respective intensity with a 10 second rest between contractions, once a day for five days. Goniometric measurements of hamstring flexibility using a lying passive knee extension test were made before and after the stretching period to determine flexibility changes. RESULTS: Paired t tests showed a significant change in flexibility for all treatment groups. A comparison of least squares means showed that there was no difference in flexibility gains between the treatment groups, but all treatment groups had significantly greater flexibility than the control group. CONCLUSION: CRPNF stretching using submaximal contractions is just as beneficial at improving hamstring flexibility as maximal contractions, and may reduce the risk of injury associated with PNF stretching.

Adolescent↗

PubMedDate not supplied

Four-strand hamstring tendon autograft compared with patellar tendon-bone autograft for anterior cruciate ligament reconstruction. A randomized study with two-year follow-up.

Seventy-two patients with subacute or chronic rupture of the anterior cruciate ligament were randomly assigned to autograft reconstruction with four-strand gracilis and semitendinosus tendon (N = 37) or with patellar tendon-bone (N = 35) from the ipsilateral side. The groups were similar in terms of age, sex, level of activity, degree of laxity, meniscal lesions found surgically, and rehabilitation program. The follow-up was performed at another hospital by independent observers after 6, 12, and 24 months. Sixty-one patients (32 with hamstring tendon grafts and 29 with patellar tendon grafts) complied with the follow-up routine for the full 24 months. No differences were found between the groups with respect to Cincinnati functional score, KT-1000 arthrometer measurements, or stairs hopple test results. The subjective result and the single-legged hop test result were better for the hamstring tendon group after 6 and 12 months, but no differences were found after 24 months. The hamstring tendon group showed better isokinetic knee extension strength than did the patellar tendon group after 6 months, but not after 12 and 24 months. There was a significant weakness in isokinetic knee flexion strength among the hamstring tendon group. Anterior knee pain was not significantly different between the groups, but kneeling pain was significantly less common in the hamstring tendon group after 24 months.

Adolescent↗