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Results for “Hamstring Muscles”

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At least 991 records · Page 55Linked to original sources

PubMed1991

Reproducibility of nine tests to measure spinal mobility and trunk muscle strength.

The reproducibility of nine back function tests suitable for use in the occupational health service was determined in 30 male employees. The correlation of three tests made with a tape measure--forward bending, modified Schober, and side bending--was high in both intra- and inter-observer comparisons (r = 0.82-0.96). Immediate repetition of the testing procedure improved the performance in the forward and side bending tests. The reproducibility was also good for the tests of dynamic (K = 0.57-0.78) and endurance (r = 0.90-0.96) strength of the abdominal muscles and quite good for the test of endurance strength of the back muscles (r = 0.74-0.80). The differences between the examiners must be taken into account in the modified Schober test, and in testing the flexibility of the hip flexors and hamstrings and the endurance strength of the back muscles.

Adult↗

PubMed1999

The effects of the antagonist muscle force on intersegmental loading during isokinetic efforts of the knee extensors.

Hamstrings activation when acting as antagonists is considered very important for knee joint stability. However, the effect of hamstring antagonist activity on knee joint loading in vivo is not clear. Therefore, the purpose of this study was to examine the differences in antagonistic muscle force and their effect on agonist muscle and intersegmental forces during isokinetic eccentric and concentric efforts of the knee extensors. Ten males performed maximum isokinetic eccentric and concentric efforts of the knee extensors at 30 degrees s(-1). The muscular and tibiofemoral joint forces were then estimated using a two-dimensional model with and without including the antagonist muscle forces. The antagonist moment was predicted using an IEMG-moment model. The predicted antagonist force reached a maximum of 2.55 times body weight (BW) and 1.16 BW under concentric and eccentric conditions respectively. Paired t-tests indicated that these were significantly different (p<0.05). A one-way analysis of variance indicated that when antagonist forces are included in the calculations the patella tendon, compressive and posterior shear joint forces are significantly higher compared to those calculated without including the antagonist forces. The anterior shear force was not affected by antagonist activity. The antagonists produce considerable force throughout the range of motion and affect the joint forces exerted at the knee joint. Further, it appears that the antagonist effect depends on the type of muscle action examined as it is higher during concentric compared to eccentric efforts of the knee extensors.

Adult↗

PubMed2006

The effects on sensorimotor performance and balance with Tai Chi training.

OBJECTIVES: To compare the effects of short-term and long-term Tai Chi training on the sensorimotor and balance performance of able-bodied subjects. DESIGN: A nonrandomized cross-sectional controlled trial. SETTING: Sport laboratory. PARTICIPANTS: Forty-eight healthy subjects, 16 with 3 months of experience in Tai Chi training, 16 with 1 to 3 years of experience in Tai Chi training, and 16 with no experience in Tai Chi training. INTERVENTION: Experimental. MAIN OUTCOME MEASURES: The reflex contraction latencies (reaction time) of medial hamstrings and gastrocnemius after perturbation, the active knee joint angle-repositioning error, and the balance time on a tilt board were measured and analyzed with 1-way analysis of covariance. Significant results were further analyzed with post hoc linear contrasts. RESULTS: Long-term Tai Chi practitioners had a significantly faster reflex reaction time in hamstrings (P<.000) and gastrocnemius (P=.043) muscles and a longer balance time on a tilt board (P<.000) than short-term Tai Chi practitioners and nonpractitioners. Both long- and short-term Tai Chi practitioners had significantly less knee joint angle-repositioning error than nonpractitioners (P=.001 and P=.027, respectively). CONCLUSIONS: Tai Chi training of more than 1 year might have the benefits of faster hamstrings and gastrocnemius reflex reaction and improved knee joint position sense (JPS). These changes might be associated with an improved dynamic standing balance. Better knee JPS was shown in subjects with 3 months of Tai Chi practice, but this had not led to a significant improvement in balance.

Adult↗

PubMed2026

Comparative effects of 12-week resistance training on unstable and stable surfaces on muscle stiffness, muscle co-activation, and balance in older patients with knee osteoarthritis.

OBJECTIVE: This randomized trial compared the effects of unstable resistance training (URT), involving resistance exercises on unstable surfaces, and stable resistance training (SRT), performed on stable surfaces, on muscle stiffness, co-activation, and balance in older adults with knee osteoarthritis (KOA). We hypothesized that URT would yield greater improvements by enhancing neuromuscular adaptability. METHODS: Fifty patients with KOA were randomly assigned to the URT group (n = 25) or the SRT group (n = 25). After attrition, 46 participants (URT: n = 23; SRT: n = 23) completed the intervention and were included in the final analysis. Both groups completed a 12-week supervised lower-limb resistance training program (3 sessions/week) consisting of 10 exercises performed under either unstable or stable support conditions. RESULTS: After 12 weeks of intervention, both groups showed significant reductions in pain intensity (p < 0.001). However, compared with the SRT group, the URT group demonstrated significantly greater reductions in quadriceps stiffness (p < 0.05), selected hamstring stiffness outcomes (p < 0.05), and quadriceps-hamstring co-activation (p < 0.001), alongside superior improvements in both dynamic balance and static balance (all p < 0.05). CONCLUSION: While both training modalities are effective for pain relief, URT elicited greater improvements in balance-related performance and neuromuscular-mechanical outcomes than SRT in older adults with KOA. These findings suggest that incorporating unstable support conditions into resistance training may provide additional rehabilitation benefits for this population.

Humans↗

PubMed1998

A case of streptococcal myositis (misdiagnosed as hamstring injury).

Streptococcal myositis is a very rare bacterial infection of muscle with a high mortality. Diagnosis is difficult because of the paucity of clinical signs and symptoms at the onset. However, presentation of the disease appears to have changed over the last 50 years. A case of streptococcal myositis is presented (misdiagnosed as hamstring injury), which more closely reflects the current presentation of the disease. Some of the features that may help emergency clinicians to recognise the onset of the condition are highlighted.

Adult↗

PubMed2001

Muscle strength and function before and after anterior cruciate ligament reconstruction using semitendonosus and gracilis.

This study assessed the quadriceps and hamstring strength before and 6 months after anterior cruciate ligament (ACL) reconstructive surgery using the hamstrings and related the findings to functional performance. Six months after surgery is a critical time for assessment as this is when players are returning to sport. Maximum isokinetic strength of 31 patients with complete unilateral ACL ruptures was measured at speeds of 60 degrees and 120 degrees per second. Functional assessment included the single hop, the triple hop, the shuttle run, side-step and carioca tests. All patients underwent a controlled quadriceps emphasized home-based physiotherapy program both before and after surgery. Results show that before surgery there was a 7.3% quadriceps strength deficit at 60 degrees per second compared to the uninjured leg but no hamstring strength deficit. After surgery there was a statistically significant but relatively small loss of muscle strength. The quadriceps strength deficit had increased to 12% and there was a 10% hamstring deficit. Post-operatively there was an 11% and 6.3% improvement in the hop tests, a 9% (P < 0.01) improvement in the shuttle run, a 15% (P < 0.001) improvement in the side step and a 24% (P < 0.001) improvement in the carioca tests (P < 0.001) despite the loss of muscle strength.

Adult↗

PubMed1997

Muscle activity in wedge, parallel, and giant slalom skiing.

Muscle activity patterns of six alpine skiers were compared during nine runs each of wedge (W), short radius parallel (P), and giant slalom (GS) turns. Bipolar surface electrodes were placed over 12 muscles on the right side of the body: anterior tibialis, medial gastrocnemius, vastus medialis, vastus lateralis, rectus femoris, medial hamstrings, biceps femoris, gluteus maximus, adductors, rectus abdominis, external obliques, and erector spinae. Repeated measures ANOVA was used to test for differences in average and peak EMG amplitudes between W, P, and GS (P < 0.1). Average amplitude was significantly different between all turning styles (W < P < GS) for four muscles (vastus lateralis, medial hamstrings, biceps femoris, and external obliques) and significantly less for W versus P or GS for four muscles (anterior tibialis, vastus medialis, rectus femoris, and rectus abdominis). The gluteus maximus was the only muscle that had significantly greater activity in W than P. Average amplitude was greater than 50% MVC for the vastus medialis, vastus lateralis, biceps femoris, gluteus maximus, and adductors in all conditions; and for the anterior tibialis, medial hamstrings, and rectus femoris in GS and P; and for the medial gastrocnemius and erector spinae in GS. Peak amplitude was greater than 150% maximal voluntary contraction (MVC) for the vastus medialis, vastus lateralis, biceps femoris, gluteus maximus, and adductors in all conditions, and for the medial gastrocnemius, rectus femoris, and erector spinae in GS. This research indicates that with the exception of the gluteus maximus, greater muscle activity is required in GS followed by P and W turns.

Adult↗

PubMed2006

Lower-extremity muscle cross-sectional area after incomplete spinal cord injury.

OBJECTIVES: (1) To quantify skeletal muscle size in lower-extremity muscles of people after incomplete spinal cord injury (SCI), (2) to assess differences in muscle size between involved lower limbs, (3) to determine the impact of ambulatory status (using wheelchair for community mobility vs not using a wheelchair for community mobility) on muscle size after incomplete SCI, and (4) to determine if differential atrophy occurs among individual muscles after incomplete SCI. DESIGN: Case-control study. SETTING: University research setting. PARTICIPANTS: Seventeen people with incomplete SCI and 17 age-, sex-, weight-, and height-matched noninjured controls. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Maximum cross-sectional area (CSA) of individual lower-extremity muscles (soleus, medial gastrocnemius, lateral gastrocnemius, tibialis anterior, quadriceps femoris, hamstrings) as assessed by magnetic resonance imaging. RESULTS: Overall, subjects with incomplete SCI had significantly smaller (24%-31%) average muscle CSA in affected lower-extremity muscles as compared with control subjects (P<.05). Mean differences were highest in the thigh muscles ( approximately 31%) compared with the lower-leg muscles ( approximately 25%). No differences were noted between the self-reported more- and less-involved limbs within the incomplete SCI group. Dichotomizing the incomplete SCI group showed significantly lower muscle CSA values in both the wheelchair (range, 21%-39%) and nonwheelchair groups (range, 24%-38%). In addition, the wheelchair group exhibited significantly greater plantarflexor muscle atrophy compared with the dorsiflexors, with maximum atrophy in the medial gastrocnemius muscle (39%). CONCLUSIONS: Our results suggest marked and differential atrophic response of the affected lower-extremity muscles that is seemingly affected by ambulatory status in people with incomplete SCI.

Adult↗

PubMedDate not supplied

Minimum muscular fitness of urban Tswana children.

Two hundred and eighty-nine urban school children in Botswana were tested for their ability to perform tests of minimum muscular fitness. Performance was generally poor when compared with usual results obtained in developed countries. Arm strength was found to be low but not surprising when considered in terms of the low arm strength to body weight common in preadolescence. Abdominal muscle groups were also weak, however, and hamstring group flexibility was poor. These results suggest a potential for lower back distress or disability and are perhaps indicative of a general low level of physical fitness in both boys and girls. The results are discussed in terms of the role played by physical education in child development and the planning and implementation of appropriate programmes is strongly recommended.

Botswana↗

PubMedDate not supplied

Musculoskeletal deformities in Behr syndrome.

SUMMARY: Seventeen children with Behr syndrome were investigated, focusing on the musculoskeletal deformities and long-term outcome. Behr syndrome is characterized by optic atrophy beginning in early childhood associated with ataxia, spasticity, mental retardation, and posterior column sensory loss. The ataxia, spasticity, and muscle contractures, mainly of the hip adductors, hamstrings, and soleus, are progressive and become more prominent in the second decade. In 70% of the patients, contractures developed in the lower limbs, requiring surgery mainly for the Achilles tendon, hamstrings, and adductor longus. At last follow-up at an average age of 21.7 years (range, 8-31 years), 13 of the patients are housebound walkers, 2 are nonfunctional walkers, and 2 are nonwalkers.

Achilles Tendon↗

PubMed1992

Adaptations in coactivation after isometric resistance training.

Twenty sedentary male university students were randomly assigned to an experimental or a control group. The experimental group trained the knee extensors of one leg by producing 30 isometric extension maximal voluntary contractions (MVC) per day, three times per week for 8 wk. After 8 wk of training, extensor MVC in the trained leg increased 32.8% (P less than 0.05), but there was no change in vastus lateralis maximal integrated electromyographic activity (IEMGmax). The most important finding was that the degree of hamstring coactivation during extension MVC decreased by approximately 20% (P less than 0.05) after the 1st wk of training. Less pronounced adaptations occurred in the untrained leg: extension MVC force increased 16.2% (P less than 0.05), hamstring coactivity decreased 13% (P less than 0.05) after 2 wk of training, and vastus lateralis IEMGmax was unchanged. The same measures in legs of the control group were not changed during the study. There were no changes in flexion MVC, biceps femoris IEMGmax, or the degree of quadriceps coactivity during flexion MVC in either leg of the control or experimental group. A reduction in hamstring coactivity in the trained and untrained legs indicates that these muscles provide less opposing force to the contracting quadriceps. We conclude that this small but significant decrease in hamstring coactivation that occurs during the early stages of training is a nonhypertrophic adaptation of the neuromuscular system in response to static resistance training of this type.

Adaptation, Physiological↗

PubMed2000

Duration of maintained hamstring flexibility after cessation of an acute static stretching protocol.

OBJECTIVE: Increased muscle flexibility from static stretching is supported by the literature, but limited research has assessed the duration of maintained flexibility gains in knee joint range of motion after same-day static hamstring stretching. The purpose of our study was to determine the duration of hamstring flexibility gains, as measured by an active knee-extension test, after cessation of an acute static stretching protocol. DESIGN AND SETTING: All subjects performed 6 active warm-up knee extensions, with the last repetition serving as the baseline comparison measurement. After warm-up, the experimental group performed 4 30-second static stretches separated by 15-second rests. SUBJECTS: Thirty male subjects (age = 19.8 +/- 5.1 years, ht = 179.4 +/- 18.7 cm, wt = 78.5 +/- 26.9 kg) with limited hamstring flexibility of the right lower extremity were randomly assigned to control and experimental groups. MEASUREMENTS: Postexercise active knee-extension measurements for both groups were recorded at 1, 3, 6, 9, 15, and 30 minutes. RESULTS: Tukey post hoc analysis indicated significant improvement of knee-extension range of motion in the experimental group that lasted 3 minutes after cessation of the static stretching protocol. Subsequent measurements after 3 minutes were not statistically different from baseline. A dependent t test revealed a significant increase in knee-extension range of motion when comparing the first to the sixth active warm-up repetition. CONCLUSIONS: Our results suggest that 4 consecutive 30-second static stretches enhanced hamstring flexibility (as determined by increased knee-extension range of motion), but this effect lasted only 3 minutes after cessation of the stretching protocol. Future research should examine the effect of other stretching techniques in maintaining same-day flexibility gains.

Journal Article↗

PubMed2006

Age-related slip avoidance strategy while walking over a known slippery floor surface.

When confronted with impending slip/fall situations, gait parameters are adjusted accordingly to avoid slipping. This study was conducted to assess age-related slip avoidance strategy by measuring gait parameters and muscle activity characteristics of the lower extremities (hamstrings, calves, and quadriceps) of both young and older participants while ambulating successfully over a known slippery floor surface. Fourteen younger and 14 older adults participated in this study. First, a baseline measure was collected to study normal gait prior to any exposure to slipping. A second measure was collected following a slip from a contaminated floor surface, but before the initiation of a second slip, where the participants were able to view the contaminated surface before traversing it. The results indicated that there were significant gait parameter differences between normal-dry walking conditions and contaminated-slippery walking conditions. In general, participants (young and old) reduced step length, friction utilization, and heel contact velocity from normal gait to adjusted gait conditions. Furthermore, results also indicated that there were differences in gait parameters and muscle activity characteristics between the two age groups for both a normal gait condition and a gait condition requiring adjustment. Findings suggested that older individuals required an additional step to properly adjust gait for a contaminated walking surface.

Accidental Falls↗

PubMed1983

The Girdlestone procedure in spinal cord injured patients: a ten year experience.

The Girdlestone procedure which originally was developed for the treatment of tuberculosis of the hip has found a place in the management of septic hip arthritis and osteomyelitis secondary to pressure sores in spinal cord injury and other myelopathies. Eradication of the septic focus is necessary if amyloid disease is to be prevented. Early diagnosis and aggressive surgery are essential. Surgical treatment entails not only bone removal, but also a thorough joint debridement. This procedure goes hand-in-hand with the appropriate antibiotic treatment given intravenously for an adequate time (4-6 weeks). When available, hyperbaric oxygen therapy is a good treatment. It is important to obliterate a large pseudoarthrosis cavity by muscle transfer from the thigh using a hamstring or a vastus lateralis. Irrigation, suction and drainage are important until the would heals. In summary, 39 patients had 42 Girdlestone procedures without any operative mortality. Seventy percent of the wounds had healed and 30% failed to heal requiring another operation. Recurrences were observed in 10% of the patients, and these cases needed another operation together with hyperbaric oxygen therapy. Eight patients died due to other causes unrelated to the operation. The procedure is rather simple but needs prolonged postoperative care, especially with wound failure or recurrences.

Amyloidosis↗

PubMed1999

The influence of non-paretic leg movement on muscle action in the paretic leg of hemiplegic patients.

The aim of this investigation was to study the effect of non-involved-side exercise on the involved (paretic) leg-muscle of patients with stroke. Each of the ten adults studied attempted to perform, while seated, a predetermined sequence of the following actions : (1) a voluntary knee extension on the involved side; (2) a maximal, isometric knee-flexion on the non-involved side; (3) a maximal, isometric knee-flexion on the non-involved side with counter-resistance (in front of the ankle joint) on the involved side. The root-mean-square voltage was measured across the rectus femoris, the medial hamstring, the tibialis anterior, and the medial gastrocnemius muscles (on the involved side) with surface electrodes. The root-mean-square voltages of the involved-side rectus femoris and the tibialis anterior muscles were found to increase substantially during non-involved-side knee flexion relative to that detected for voluntary knee extension on the involved side. The voltage of the rectus femoris muscle increased substantially also when counter-resistance was present. There was no similar substantial increase of muscular activity, in the medial hamstring and medial gastrocnemius, induced by contralateral isometric knee-flexion. This study suggests that, among patients with severe hemiplegia, isometric knee flexion in the non-involved side may be useful for facilitating the paretic rectus femoris and tibialis anterior muscular activities.

Aged↗

PubMed1996

Amplitude and timing of electromyographic activity during sprinting.

The aim of this study was to make descriptive analyses of the muscle activities in the lower extremity during maximal sprinting. Nine healthy sprinters were examined during maximal sprinting using telemetric electromyography (EMG). Seven muscles of the lower extremities were investigated: biceps femoris, medial hamstrings (semimembranosus and semitendinosus), rectus femoris, gluteus maximus, tibialis anterior, lateral gastrocnemius and medial gastrocnemius. The recorded EMG levels during running were expressed as percentage of maximum voluntary isometric contractions (%max EMG). For each muscle, the normalized EMG was plotted during the whole running stride cycle and is presented for each muscle. The reason for using this method is to show that it is possible to compare different muscle activities in a runner as well as to make comparisons between runners. Lateral and medial hamstrings and gluteus maximus showed similar activities with peak levels of EMG during foot-strike. Rectus femoris had a two-peak activity, with one peak at the middle of the stance phase and the other during the swing phase. The tibialis anterior also showed a two-peak activity, but with the peaks at the beginning of the swing phase and just before foot-strike. The highest activities of the medial and lateral gastrocnemius occurred just before toe-off.

Adolescent↗

PubMed1985

A general method for determining the functional role of a muscle.

This paper presents a general classification method for determining the functional role of any muscle, and a procedure for determining the sensitivity of that role to small changes in system parameters. The classification method is based on the premise that the system model, when acted upon solely by the muscle of interest, will depart from any initial rest configuration in such a way as to decrease the muscle's length. This method is particularly useful for multiple-joint muscles, and is illustrated by examining a slider-crank mechanism and straight line muscle model to determine the functional role of the hamstrings during a constrained leg flexion motion.

Biomechanical Phenomena↗

PubMedDate not supplied

Angle- and velocity-specific alterations in torque and semg activity of the quadriceps and hamstrings during isokinetic extension-flexion movements.

The purpose of this study was to investigate the effect of movement velocity (100 degrees, 200 degrees , 300 degrees s(-1), and 400 degrees s(-1)) and joint position (0 degrees - 15 degrees [L0], 25 degrees - 40 degees [L25], 55 degrees - 70 degrees [L55], and 75 degrees - 90 degrees [L75]) on peak torque (PT) parameters and surface electromyography (SEMG) of the knee-joint muscles during reciprocal isokinetic extension and flexion movements. Thirteen subjects (age = 22.7 +/- 2.1 years, mean height = 161.1 +/- 6.6 cm, mean weight = 63.5 +/- 5.8 kg) participated in the study. Bipolar surface electrodes were placed over the vastus medialis, vastus lateralis, biceps femoris, and medial hamstrings for determination of the root mean square (SEMGrms) and median frequency (SEMGmf) of the SEMG. Peak torque, angle of peak torque (PTang), percentage of peak torque (PTper), SEMGrms, and SEMGmf were analyzed using separate repeated measures analysis of variance (ANOVA). The following main results, significant at p < or = 0.05 or better, were found: The PTang was influenced by movement velocity (in extension there was a decrease in PTang moving from 300 degrees x s(-1) to 400 degrees x s(-1) and inflexion there was an increase in PTang moving from 300 degrees x s(-1) to 400 degrees x s(-1)). Secondly, a greater percentage of peak torque (PTper) was maintained during knee flexion than knee extension. And thirdly, both the quadriceps and hamstrings exhibited changing amplitudes and spectral frequencies based on joint position and movement velocity. There was a trend of decreasing SEMGrms for the quadriceps as the knee moved into extension, and a lower SEMGmf during early (L75) and end stages of knee extension (L0). For the hamstrings, SEMGrms was lowest at the more shortened position (L75) and highest near the mid-position (L25); the lowest SEMGmf occurred at the more lengthened position (L0) and the highest occurred at the more shortened position (L75). Finally, velocity influenced hamstrings and quadriceps muscle amplitude such that SEMGrms was highest at the slower velocities and lowest at the higher velocities. Velocity had no impact on quadriceps spectral properties (p > 0.05), but had a cyclic effect on hamstrings spectral properties. Changes in amplitude and frequency spectrum in tested muscles could be explained, in part, by neural drive to these muscles. Data support the hypothesis of lower activation levels of the quadriceps muscle in the extended position espoused by several authors as a way to protect the knee-joint in the knee-extended position.

Adult↗