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PubMed1985

Injury-induced plasticity of the flexor reflex in chronic decerebrate rats.

The hindlimb-flexor-withdrawal reflex elicited by stimulation of the skin of the hindpaw has been examined in chronic decerebrate rats. This flexor reflex manifests as a typical phasic avoidance response when measured either behaviourally in the decerebrate rat or electrophysiologically in the decerebrate-spinal preparation. Once the threshold of the cutaneous flexor-reflex afferents in the skin have been exceeded a brief burst of activity with only a short afterdischarge occurs in the flexor motoneurones. The response to sustained stimuli adapts rapidly. In the absence of any treatment to the hindlimb the threshold, duration and responsiveness of the reflex remains stable when tested repeatedly. Thermal or chemical stimuli of sufficient intensity to produce tissue injury and prolonged local inflammation in a hindpaw of the chronic decerebrate rat result in marked and long-lasting (several weeks) alterations in the ipsilateral withdrawal reflex. The mechanical threshold necessary to elicit the reflex by stimulation of the hindpaw falls so that light touch or brush can now elicit a response instead of the firm pressure or pinch required pre-injury. Suprathreshold stimuli to the inflamed skin generate a sustained oscillating pattern of flexion in contrast to the brief flicking movement found in control animals. Electromyographic recordings from the hamstring flexor muscles ipsilateral to the inflamed hindpaw show decreased mechanothresholds, increased spontaneous activity, prolonged afterdischarges to brief stimuli and a slowly adapting tonic response to sustained stimulation. Populations of single cutaneous mechanoreceptive C-primary afferents recorded both from untreated decerebrate rats and from rats with an inflamed hindpaw are indistinguishable in terms of their response properties. There is no difference in threshold, spontaneous activity or afterdischarge between the two populations. The possible mechanisms responsible for the conversion of the high threshold phasic flexor reflex into a low threshold tonic reflex are discussed as are the possible implications for sensory disorders that accompany chronic injury in man.

Animals↗

PubMed1994

Evaluation of the gravity-correction feature of a Kin-Com isokinetic dynamometer.

BACKGROUND AND PURPOSE: Torques reflecting muscle performance must be corrected for the effects of gravity if error-free ratio-scaled data are to be obtained. Ratio-scaled data are necessary, for example, to report muscle performance characteristics in terms of ratios or percentages or in the form of ratios with another muscle (eg, ratio of hamstring to quadriceps femoris muscle peak torque). The purpose of this study was to determine the error associated with the gravity-correction procedure of the Kin-Com dynamometer when a weight or limb segment is weighed at different lever arm positions. METHODS: A known weight was suspended from the lever arm of the Kin-Com dynamometer. The rotational component of gravitational forces on the weight was measured at 11 different angular positions. We compared the force measurement obtained from the Kin-Com with the predicted rotational component at each angular position. The gravitational forces on a subject's limb segment (leg) were then measured at 12 different angular positions in each of two trunk positions (sitting and supine). We compared the force measurement obtained from the Kin-Com with the predicted rotational component for each position. Forces measured for the two trunk positions with the lever arm horizontal were compared. Forces measured with the knee extended were compared with forces measured with the lever arm horizontal. RESULTS: The dynamometer accurately recorded the rotational component of gravitational forces for the weight suspended from the lever arm. There was a progressively greater discrepancy between measured forces and predicted forces for the leg as the lever arm was moved from horizontal to 50 degrees below the horizontal. The force recorded with the Kin-Com was greater when the subject's knee was in full extension than when the lever arm was horizontal, which placed the subject's knee in a flexed position. A small difference was noted between the measured forces with the lever arm horizontal when the subject was sitting compared with when the subject was positioned supine. CONCLUSION AND DISCUSSION: When weighing a leg with this dynamometer, we recommend that the lever arm be as close to the horizontal position as possible. Positions of proximal joints should be chosen that do not put two joint muscles in stretched positions.

Adult↗

PubMed1999

Anterior disc protrusion as a cause for abdominal symptoms in childhood discitis. A case report.

STUDY DESIGN: A case report on infectious spondylitis in a child who reported abdominal pain and whose magnetic resonance image revealed anterior herniation of disc space contents. OBJECTIVES: To correlate the direction of disc protrusion in infectious spondylitis with clinical manifestations. SUMMARY OF BACKGROUND DATA: Previous studies have correlated posterior protrusion of disc space contents in infectious spondylitis with a clinical presentation of back pain, paravertebral muscle spasm, hamstrings tightness, and radiculopathy. None has connected anterior herniation of disc phlegmon with abdominal pain. METHODS: In addition to plain radiography and bone scintigraphy, magnetic resonance imaging was used to confirm the diagnosis of infectious spondylitis in a 6-year-old child with abdominal pain. Regular review for 1 year included repeat magnetic resonance imaging at 3 months. RESULTS: Initial magnetic resonance imaging revealed characteristic changes associated with infectious spondylitis throughout the L5-S1 vertebra-disc-vertebra unit and anterior protrusion of the disc material and phlegmon. Magnetic resonance imaging at follow-up examination 3 months later demonstrated complete resolution of the disc herniation. CONCLUSION: Future magnetic resonance imaging studies should correlate direction of disc herniation with age and symptomatology to validate or improve classifications of infectious spondylitis, which presently include only the last two parameters.

Abdominal Pain↗

PubMed1993

Hindlimb flexion withdrawal evoked by noxious heat in conscious rats: magnitude measurement of stimulus-response function, suppression by morphine and habituation.

1. The aim of this study was to develop a quantitative behavioral model of nociception. Electromyographic (EMG) recordings from a hamstring flexor muscle provided a measure of the magnitude of hindlimb withdrawals elicited by brief, graded noxious contact thermal stimuli applied to the hindpaw in conscious rats. 2. The magnitude of limb withdrawals showed a significant, usually linear, increase with stimulus temperature from a threshold of approximately 40 up to 52 degrees C. Stimulus-response functions of withdrawal magnitude versus temperature were reproducible within and across rats. Withdrawal magnitude was much more tightly correlated with stimulus temperature (r2 = 0.76, 0.73) than was withdrawal latency (r2 = 0.57, 0.55). 3. Systemic administration of the opiate analgesic morphine (3.5 mg/kg ip) suppressed withdrawals in a naloxone-reversible manner, such that the slope of the stimulus-response function was significantly reduced without an increase in threshold. 4. Successive withdrawals to repeated, identical noxious heat stimuli decreased in a manner consistent with habituation. The response recovered to the prehabituated level after a 15-min rest period, and subsequently decremented even more quickly. The decrement in withdrawal magnitude was greater at lower stimulus intensities and shorter interstimulus intervals, and transferred to a nearby (7.5 mm) but not distant (2.5 cm) site. Evidence for dishabituation was also obtained. 5. The advantages of this method as an animal model of nociception are presented and discussed in terms of the underlying neural circuitry and its modulation.

Afferent Pathways↗

PubMed1984

Comparative study of static, dynamic, and proprioceptive neuromuscular facilitation stretching techniques on flexibility.

63 college women served as subjects in this 7-wk. study examining the effects of static, dynamic, and proprioceptive neuromuscular facilitating stretching techniques on the flexibility of the hamstring-gastrocnemius muscles. Subjects were assigned to one of the 3 treatment groups and received treatment 3 days a week. A pretest, a midtest (after 11 treatment days), and a posttest (after 21 treatment days) were administered. Analysis of group and test effects was accomplished by using a 3 X 3 factorial design with the group factor nested and the test factor crossed. Post hoc analysis indicated that all scores significantly improved from pretest to posttest. The findings indicated all 3 methods of flexibility training produced significant improvements when pretest and posttest mean scores were compared.

Female↗

PubMed2026

Timing and Dose Matter: Late High-Speed Exposure and Higher High-Intensity Acceleration Volumes Reduce Hamstring Reinjury Risk in Elite Male Football (Soccer).

OBJECTIVES: The aims of this study were to (a) investigate whether the timing and magnitude of exposure to high-speed running (HSR), sprinting, and high-intensity accelerations during on-field rehabilitation after hamstring strain injury were associated with reinjury risk and (b) examine changes in match running performance upon return to play (RTP). DESIGN: Retrospective cohort study. METHODS: Data from 95 elite male football (soccer) players from five professional clubs competing in major European and Middle Eastern leagues were analyzed. Players with complete rehabilitation load profiles were included in the 2-month and 6-month reinjury analysis. Modified Poisson regression assessed associations between rehabilitation load characteristics and reinjury risk. Match running performance (HSR distance, sprint distance, and high-intensity accelerations per minute) during the five matches before injury and the first five matches after RTP was compared using paired t-tests for the entire cohort. RESULTS: Late introduction of HSR, sprinting, and high-intensity accelerations during rehabilitation (ie, ≥ 60% of rehabilitation progression) was associated with a significantly lower reinjury risk at 2 months (relative risk [RR] range = 0.948-0.969; P < .01) and 6 months (RR range = 0.964-0.979; P < .05). Higher daily exposure to high-intensity accelerations once introduced was protective (RR = 0.861 (0.778-0.951)). There were no meaningful associations between total volume of HSR or sprinting and reinjury. Match running performance metrics did not differ between pre-injury and post-RTP matches (all P > .05). Changes in performance were not correlated with rehabilitation load characteristics. CONCLUSION: The timing of high-intensity running exposure during on-field rehabilitation appeared associated with a lower hamstring reinjury risk. Delaying the introduction of HSR, sprinting, and accelerations, followed by a structured and progressive build-up, was associated with lower risk of reinjury without compromising the subsequent match performance of elite male football players. J Orthop Sports Phys Ther 2026;56(9):611-621. Epub 7 Jul 2026. doi:10.2519/jospt.2026.14077.

Humans↗

PubMed1999

Efficacy of aquatic exercises for patients with low-back pain.

We have studied 35 patients (25 female and 10 male) with low-back pain who were managed with aquatic exercises after an appropriate period of treatment for their condition in the medical institution. The exercises employed consisted of strengthening exercises for the abdominal, gluteal, and leg muscles, stretching of the back, hip, hamstrings, and calf muscles, walking in water, and swimming. All the patients had been participating in the exercise program for more than 6 months. The frequency of performing exercises was once a week for 7 patients, twice a week for 19, and 3 or more times a week for the remaining patients. The method used in this study was a survey questionnaire which was composed of questions about the patient's physical and psychological condition. Those patients who had performed exercises twice or more in a week showed a more significant improvement in the physical score than those who performed exercises only once a week. More than 90% of the patients felt they had improved after 6 months of participation in the program. The improvement in physical score was independent of the initial ability in swimming. The results obtained suggested that exercises in water may be one of the most useful modes of exercise for a patient with low-back pain.

Adult↗

PubMed1987

The pyriformis syndrome: review and case presentation.

The pyriformis syndrome is a rare entrapment neuropathy in which the sciatic nerve is compromised by the pyriformis muscle or other local structures. It usually presents with sciatic pain and hypoaesthesia and a limp caused by weakness of the gluteus maximus muscle. Peroneal nerve innervated muscles and hamstrings are also usually affected. The diagnosis relies on the clinical presentation and the EMG findings. Other causes of symptoms should be excluded by careful examination, detailed x-ray studies of the lumbosacral spine (including myelogram), sacro-iliac and hip joints. A case of this syndrome occurring in a previously healthy 42 year old woman and her follow-up investigations are reported.

Adult↗

PubMed1985

Copper-induced myopathy in rabbits: ultrastructural observations.

Mature rabbits were injected intra-muscularly into the hamstring (HS) muscles with doses of 1.66 mg Cu/kg/day, as cupric acetate, in aqueous solution. Similar doses of Na acetate were injected into control rabbits. Skeletal (HS) and cardiac (MYO) muscles were examined by scanning electron microscopy, transmission electron microscopy and a microanalyzer and energy dispersive X-ray (MEDX). Na-injected rabbits showed slight myofibrillar lesions in HS after four injections, and mitochondrial inclusions in MYO were noted after two or seven injections. No Cu was found with MEDX. Cu-injected rabbits showed that the severity of lesions of myofibrillar degeneration and mitochondrial inclusions in HS increased with the number of injections and days the rabbits had been on experiment. After seven days on experiment signs of muscle regeneration were seen. Cu was found first to localize in the nucleus of HS after one day, thereafter it localized in the mitochondria after three and seven days. MYO lesions were found in the mitochondria after six or seven days after Cu-injection. With MEDX less Cu was found than had been found in HS. This Cu first localized in the nucleus of MYO after one day and then disappeared from the tissue altogether.

Animals↗

PubMed1997

Human trunk extensor muscles physiology and ergonomics.

The paravertebral muscles (PM) act together with the hamstrings and calf muscles as important postural muscles. Both the histochemistry, biochemistry, strength and endurance of the PM were studied. Moreover attention was drawn to the exposure of PM, in particular the internal exposure level but to a certain degree repetitiveness and duration, in various job elements, and their various physiological acute responses. The thesis also deal with possible relations between the function of the PM and the magnitude of low-back trouble (LBP), and if PM muscle fatigue may play a role as a mediating factor for the occurrence of work related LBP. The lumbar PM is dominated by relatively small ST fibers with a well-developed network of capillaries, especially distinct in the central sections of PM (lumbar longissimus muscle) in females. It is remarkable that ST fibers are of the same size or larger compared to the FT fibers even in well-trained subjects. Further on PM is characterized by high activity levels of enzymes, oxidative as well as non-oxidative, important for the resynthesis of ATP and CrP. Also the level of muscles glycogen concentration is high. Altogether the PM have seemingly a potential for different metabolic pathways which may be selectively activated for a given activity. The average trunk extensor MVC varies in the different studies from 194-342 Nm and 252-450 Nm in females and males respectively. This is in accordance with predictions based specific strength, muscle cross sections and lever arms from the literature. The large range in strength due to dimension, age and training have to be considered when such data are used for e.g. ergonomic standardization and biomechanical modelling. The sex difference is smaller (female:male trunk extensor strength ratio = 0.7-0.8) than reported earlier. The small age reduction (25-60 year) of the trunk extensor strength, 0.5% per year, is probably caused by the fact that the ST dominated musculature is less sensitive to atrophy. The results indicate that a secular reduction of the trunk extensor strength has occurred during the last 2-3 decades possibly caused by a more sedentary lifestyle, both in working life due to mechanization introduced gradually during that period, and in leisure time activity. An important finding is that the static endurance time is significantly larger in the trunk extensors compared to other muscles, and larger in females than males. Possible explanations for the findings include 1) the reported histo- and biochemical results, 2) favorable blood flow conditions and 3) specific activation strategies of the muscles constituting the PM. In the vocational studies manifest signs of fatigue in the lumbar paravertebral muscles, are seen, including changes in both the energy spectra of the surface EMG towards lower frequencies and increases in the RMS amplitude, reduction of the static endurance time, and increase in the rate of perceived exertion during a working day in bricklayers performing highly repetitive work with their trunk extensors (1000:1200 bricks per day). Similar events do also occur during standing letter sorting with a very low close to static exposure of PM. Ergonomic arrangements may have a marked reducing effect on the internal exposure of PM especially if the job include manual handling operations (e.g. forest work, aircraft loading), but it is not possible to compensate for repetitiveness, and long task duration by so-called "good" ergonomics (e.g. introducing mats or shoes in upright working operations). The chronic effects (i.e.LBP) are also studied. It is found that trunk extensor static endurance time in 77 postmen was related to the degree of LPB, but this was not the case for strength of the trunk-extensors and flexors. Thus, it is shown that a broad variety of work related exposures may cause muscle fatigue in PM. The possible aetiological role of muscle fatigue is however not explained. (ABSTRACT TRUNCATED)

Adolescent↗

PubMed2005

The role of estimating muscle-tendon lengths and velocities of the hamstrings in the evaluation and treatment of crouch gait.

Persons with cerebral palsy frequently walk with excessive knee flexion during terminal swing and stance. This gait abnormality is often attributed to "short" or "spastic" hamstrings that restrict knee extension, and is often treated by hamstrings lengthening surgery. At present, the outcomes of these procedures are inconsistent. This study examined whether analyses of the muscle-tendon lengths and lengthening velocities of patients' hamstrings during walking may be helpful when deciding whether a candidate is likely to benefit from hamstrings surgery. One hundred and fifty-two subjects were cross-classified in a series of multi-way contingency tables based on their pre- and postoperative gait kinematics, muscle-tendon lengths, muscle-tendon velocities, and hamstrings surgeries. The lengths and velocities of the subjects' semimembranosus muscles were estimated by combining kinematic data from gait analysis with a three-dimensional computer model of the lower extremity. Log-linear analysis revealed that the subjects who walked with abnormally "short" or "slow" hamstrings preoperatively, and whose hamstrings did not operate at longer lengths or faster velocities postoperatively, were unlikely to walk with improved knee extension after treatment (p < 0.05). Subjects who did not walk with abnormally short or slow hamstrings preoperatively, and whose hamstrings did operate at longer lengths or faster velocities postoperatively, tended to exhibit unimproved or worsened anterior pelvic tilt after treatment (p < 0.05). Examination of the muscle-tendon lengths and velocities allows individuals who walk with abnormally short or slow hamstrings to be distinguished from those who do not, and thus may help to identify patients who are at risk for unsatisfactory postsurgical changes in knee extension or anterior pelvic tilt.

Adolescent↗

PubMed1992

Thigh composition in young and elderly men determined by computed tomography.

Computed tomography (CT) was used to quantify components of the thigh in young (n = 13) and elderly (n = 11) men. Cross-sectional areas (CSA) of the total limb, total muscle plus bone, quadriceps compartment, hamstring compartment and bone were measured at each of five scan sites along the length of the thigh. Non-muscle tissue (NMT) areas within the muscle compartments were measured using changes in density based on Hounsfield units. Skin plus subcutaneous fat areas and quadriceps and hamstring lean muscle areas were calculated by subtraction. Geometric formulae were used to calculate related volumes for each thigh component. Volumes were also predicted from regression equations employing thigh length and component CSA from single mid-limb CT scans. The results showed that while total thigh CSA was not different in elderly men, they had significantly smaller total muscle plus bone (13.0%), and quadriceps (26.4%), and hamstring (17.9%) muscle areas. The elderly men also had significantly greater CSA for skin plus subcutaneous fat (37.6%), and for NMT in the quadriceps (59.4%) and hamstring (127.3%) muscle compartments. These results suggest that comparisons of relative leg muscle strength between young and elderly men may be misleading due to the decrease in actual muscle tissue associated with ageing. Appropriate quantification of muscle size and CSA must be carried out before such comparisons can be meaningful.

Aging↗

PubMed2004

[Isokinetic evaluation of the knee flexor muscles after anterior cruciate ligament reconstruction using gracilis and semitendinous tendon grafts].

PURPOSE OF THE STUDY: The purpose of this study was to evaluate recovery of hamstring force after anterior cruciate ligament reconstruction using gracilis and semitendinous tendon grafts. MATERIAL AND METHODS: Isokinetic evaluation of the knee flexor muscles was performed with the system 3 Biodex isokinetic dynameter in twelve patients (mean age 26 years) 12 to 24 months after ligamentoplasty. Concentric (60 degrees /s, 180 degrees /s, 300 degrees /s) and excentric forces were measured. We retained for analysis: 1) moment of maximal force, 2) moment of force at 75 degrees knee flexion, and 3) work. RESULTS: The knee flexor muscles of the operated limb exhibited greater deficit when considering force at 75 degrees knee flexion (24%, 15%, and 18% concentric deficit at 60 degrees /s, 180 degrees /s, and 300 degrees /s respectively, and 20% excentric deficit) than when considering maximal force (14%, 7%, 5% concentric deficit at 60 degrees /s, 180 degrees /s, and 300 degrees /s respectively and 9% excentric deficit). DISCUSSION: This study demonstrates persistent deficit of knee flexor muscle force 12 to 24 months after anterior cruciate ligament repair with hamstring muscle tendons. The deficit reaches 15% to 24% at 75 degrees of knee flexion. The protective role of the hamstring muscles for the cruciate graft submitted to important stress may be compromised by the lack of recovery of knee flexor force more than one year after ligamentoplasty.

Adult↗

PubMed1998

Concentric versus enhanced eccentric hamstring strength training: clinical implications.

OBJECTIVE: Hamstring injuries can be quite debilitating and often result in chronic problems. Eccentric muscle actions are often the last line of defense against muscle injury and ligament disruption. Traditionally, the focus of hamstring strength rehabilitation has been on concentric muscle actions. The purpose of our study was to compare hamstring muscle strength gains in concentric and eccentric hamstring strength training. DESIGN AND SETTING: A randomized-group design was used to examine differences in 1-repetition maximum (1 RM) and isokinetic strength values among 3 groups of subjects. Subjects were tested in a biomechanics laboratory using an isokinetic dynamometer, while training was carried out in a physical therapy outpatient clinic. SUBJECTS: Twenty-seven healthy male subjects (age = 22.9 +/- 3.1 years, wt = 81.8 +/- 12.9 kg, ht = 178.6 +/- 7.2 cm) participated in this study. Subjects were randomly assigned to 1 of 3 treatment groups: eccentric training, concentric training, or control. MEASUREMENTS: Subjects performed hamstring curls using an isotonic weight training device. Pretest 1 RM weight values were determined for all subjects using a standardized 1 RM protocol. In addition, maximum concentric and eccentric isokinetic strength values for knee-flexion strength were determined. Control group subjects refrained from weight training for 6 weeks. Subjects in the training groups trained 2 days per week for 6 weeks (12 sessions). After 6 weeks of training, all subjects returned for 1RM and isokinetic posttesting. RESULTS: The concentric group improved 19%, while the eccentric group improved 29%. The control group subjects did not show any significant change over the 6 weeks. In addition, there were improvements in eccentric isokinetic peak torque/ body weight ratios at both 60 degrees s and 180 degrees from pretesting to posttesting in the eccentric training group only. CONCLUSIONS: Our results demonstrate the effectiveness of isotonic strength training on the development of hamstring muscle strength. More important is the dramatic effect of eccentric strength training on overall hamstring muscle strength, both isotonic and isokinetic. Clinicians should consider using eccentric hamstring strengthening as part of their rehabilitation protocols for hamstring and knee injuries.

Journal Article↗

PubMed2000

Quadriceps-hamstring EMG activity during functional, closed kinetic chain exercise to fatigue.

It has been hypothesized that the ability of the neuromuscular system to co-contract muscles for joint stabilization may be impaired during the development of fatigue. The purpose of this study was to examine muscle activation of the quadriceps and hamstring muscles during a prolonged closed kinetic chain exercise, the forward lunge. Eight males and two females [mean (SD) age 26.0 (2.3) years, height 177.2 (13.6) cm, body mass 82.8 (17.1) kg] with no prior knee pathology volunteered for this study. Subjects performed repeated forward lunges onto their dominant leg at the cadence of one full lunge cycle every 2 s, until the point of volitional failure. Digital switches were positioned to record foot-strike and knee-strike of the lunge leg at the midpoint of the lunge, as well as heel-strike upon return to stance. During the lunge performance, surface electromyographic (EMG) signals of the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) muscles of the supporting leg were measured. Heart rate was also monitored every 30 s during the performance. All EMG data were full-wave rectified, partitioned into up and down phases, and integrated over the entire exercise period. The results demonstrated a significant increase in activation of the VL, VM, and BF during performance of the forward lunge to volitional failure (P < 0.05). No significant increase was shown for the ST. Heart rate increased significantly over the course of the lunge. These findings suggest that activation of the VL, VM, and BF muscles occurs as a unit during performance of the forward lunge during both concentric and eccentric lunge phases.

Adult↗

PubMed2005

Estrogen replacement, muscle composition, and physical function: The Health ABC Study.

PURPOSE: Although the beneficial effects of estrogen use on cardiovascular and cognitive function in postmenopausal women have been recently discredited, controversy remains regarding its usefulness for maintaining skeletal muscle mass or strength. Therefore, the purpose of this study was to determine whether estrogen use is associated with enhanced muscle composition and, if so, whether this translates into improved strength and physical function. METHODS: Cross-sectional analysis of 840 well-functioning community-dwelling white women (current estrogen replacement therapy (ERT) users = 259, nonusers = 581) aged 70-79 yr participating in the Health, Aging and Body Composition Study. Muscle composition of the midthigh by computed tomography included cross-sectional area (CSA) of the quadriceps, hamstrings, intermuscular fat and subcutaneous fat, and muscle attenuation in Hounsfield units (HU) as a measure of muscle density. Isometric hand grip and isokinetic knee extensor strength were assessed by dynamometry. Physical function was assessed using a summary scale that included usual 6-m walk and narrow walk speed, repeated chair stands, and standing balance. RESULTS: In analyses of covariance adjusted for relevant confounders, quadriceps muscle CSA and HU were greater in current ERT than non-ERT women (P < 0.05). Grip strength was also greater (P < 0.05) in women taking ERT while knee extensor strength approached significance (P < 0.10). However, differences in muscle composition and strength were modest at < or =3.3%. There was no difference by ERT status for the hamstring muscles, fat CSA, or for physical function. CONCLUSION: The associations between ERT and muscle composition and strength were minor and did not translate into improved physical function. Initiation of ERT for preservation of muscle composition and function may not be indicated.

Aged↗

PubMed2002

Landing adaptations after ACL reconstruction.

PURPOSE: The purpose of this study was to determine whether fully rehabilitated ACL reconstructed (ACLr) recreational athletes utilize adapted lower-extremity joint kinematics and kinetics during a high-demand functional task. METHODS: The kinematic and kinetic performance of 11 healthy and 11 hamstring ACLr recreational athletes were compared during a 60-cm vertical drop landing. RESULTS: At initial ground contact, the ACLr group demonstrated greater hip extension and ankle plantarflexion compared with the healthy group. The peak vertical ground-reaction force was not different between groups, but the ACLr group delayed the time to its occurrence. The knee extensors provided the major energy absorption function for both groups; however, the ACLr group performed 37% more ankle plantarflexor work and 39% less hip extensor work compared with the healthy group. CONCLUSIONS: The hamstring ACLr recreational athletes utilized an adapted landing strategy that employed the hip extensor muscles less and the ankle plantarflexor muscles more. The harvesting of the medial hamstring muscles for ACL reconstruction may contribute to the utilization of this protective landing strategy.

Adaptation, Physiological↗

PubMed2006

Factors associated with decreased muscle strength after anterior cruciate ligament reconstruction with hamstring tendon grafts.

PURPOSE: To identify factors associated with decreased muscle strength and activity after anterior cruciate ligament (ACL) reconstruction with semitendinosus-gracilis tendon (ST-G) grafts. TYPE OF STUDY: Retrospective review. METHODS: Eighty-five patients who underwent ACL reconstruction with ST-G grafts were evaluated at a mean of 44.4 months after surgery. Patients underwent isokinetic testing, physical examination, radiographs, instrumented laxity testing, and Lysholm, Cincinnati, and International Knee Documentation Committee (IKDC) ratings. Cartilage and meniscal pathology at surgery was reviewed. Strength group 1 (n = 30) showed greater than 20% deficits in strength; strength group 2 (n = 55) had less than 20% strength deficits. Activity group 1 (n = 60) maintained their IKDC activity level at final follow-up relative to preinjury level; activity group 2 (n = 25) decreased activity by 1 or more levels. RESULTS: With all patients combined, there was less than a 4% difference in mean hamstring and quadriceps strength between the reconstructed and contralateral legs at follow-up. Knee flexion deficits were associated with decreased hamstring strength. Subjective giving way and squatting/kneeling discomfort were associated with decreased quadriceps strength. Patients in strength group 1 were more likely to have squatting/kneeling discomfort and lower Cincinnati Function scores. Activity group 2 had a longer interval from injury to surgery and more chondromalacia at surgery. At follow-up, activity group 2 had lower subjective scores and was more likely to have pain, swelling, giving way, and flexion deficits. Activity group 2 also had greater deficits in quadriceps strength. CONCLUSIONS: Articular cartilage injury and meniscal pathology were not associated with decreased muscle strength. ACL reconstruction with ST-G grafts has a 38% incidence of squatting/kneeling pain that occurs secondary to patellofemoral crepitus, harvest site symptoms, and tibial hardware sensitivity. LEVEL OF EVIDENCE: Level IV, therapeutic, case series, no control group.

Anterior Cruciate Ligament↗