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PubMed1997

Correlation of bone density to strength and physical activity in young men with a low or moderate level of physical activity.

The objective of this study was to evaluate the relationship among bone mineral density (BMD), physical activity, muscle strength, and body constitution, in young men with a low or moderate level of physical exercise. Another aim was to investigate whether the head is unaffected by physical activity. The subjects consisted of 33 Caucasian healthy men, mean age 24.8 +/- 2.3 years. BMDs of the total body, lumbar spine (L2-L4), femoral neck, Ward's triangle and trochanter, humerus, and head were measured using dual-energy-X-ray absorptiometry (DXA). Bivariate correlations were measured among the different BMD sites and age, weight, height, body mass index (BMI), fat mass, lean body mass, amount of physical activity (hours/week), hamstrings strength, and quadriceps strength. Significant predictors were found for all BMD sites except the head. Using all these variables, only 6% of the variation in BMD of the head could be explained, whereas 46% (total body), 31% (humerus), 17% (lumbar spine), 38% (femoral neck, Ward's), and 41% could be explained for the trochanter. Physical activity and muscle strength were found to be independent significant predictors of BMD of the total body and the sites at the proximal femur. These results suggest that at the time of peak bone mass attainment, physical activity is an important predictor of the clinically relevant proximal femur in young men with a low or moderate level of physical activity. Furthermore, since head BMD was not related to the level of physical activity, we suggest that head BMD may be used as an internal standard, to control for selection bias, in studies investigating the effect of physical activity on bone mass.

Absorptiometry, Photon↗
PubMed2005

Maintenance of upright standing posture during trunk rotation elicited by rapid and asymmetrical movements of the arms.

Nine healthy subjects standing upright, initiated small, medium and large (S, M and L conditions, respectively) forward movements of their right (Rt) arm together with backward movements of their left (Lt) arm. They also performed medium-size movements while holding a 3 kg dumbbell in each hand (D condition). Movements started with the arm hanging alongside the body and ended when the shoulder reached a desired orientation. The arm and trunk movements were videotaped and recorded by accelerometers taped to the wrists, shoulders, and hips bilaterally. The torque around the vertical axis was measured using a force-plate on which the subjects stood. EMGs were recorded with surface electrodes bilaterally from the shoulder, trunk, and thigh muscles. Trajectories of the center of foot pressure were measured in additional experiments. In association with arm movements, there was a small counterclockwise (ccw: the Rt shoulder forward and the Lt backward) rotation of the trunk, followed by large alternate rotations of the trunk, first clockwise (cw) and subsequently ccw. The intervals from the hand acceleration to the shoulder and hip accelerations were, respectively, 0+/-15 ms (mean and S.D. for all subjects) and -17+/-15 ms. The force-plate showed initial cw and later ccw torques 63+/-41 ms after hand acceleration. The EMGs of the Rt hamstrings (Ham) and Lt rectus femoris (RFem) were followed by those of the Lt Ham and Rt RFem which, respectively preceded the alternate trunk rotations. The integrated EMGs and torques increased with increasing amplitude of arm movement and load. The integrated torques increased in the order of S, M, L, and D conditions. The integrated EMGs of the thigh muscles correlated with the integrated torques (medians: r=0.880, 0.696, 0.785, and 0.688, respectively, in the Rt Ham, Lt Ham, Rt RFem, and Lt RFem). The trajectories of the center of foot pressure showed variations, initially toward the Rt side and then the Lt side which, respectively coincided with the initial and later phases of the trunk rotations and the muscle activation. The trunk muscles were generally coactivated between the Rt and Lt muscles, and the integrated EMGs increased with increasing the integrated torques. Our results showed that alternate rotations of the upper trunk, produced by rapid arm movements, were transmitted to the hip in part due to cocontraction of trunk muscles, and each pair of hip joint muscles contributed to the maintenance of the standing posture by stabilizing the hip joints against alternating trunk rotations.

Adaptation, Physiological↗
PubMed1997

Influence of strength training on sprint running performance. Current findings and implications for training.

Today, it is generally accepted that sprint performance, like endurance performance, can improve considerably with training. Strength training, especially, plays a key role in this process. Sprint performance will be viewed multidimensionally as an initial acceleration phase (0 to 10 m), a phase of maximum running speed (36 to 100 m) and a transition phase in between. Immediately following the start action, the powerful extensions of the hip, knee and ankle joints are the main accelerators of body mass. However, the hamstrings, the m. adductor magnus and the m. gluteus maximus are considered to make the most important contribution in producing the highest levels of speed. Different training methods are proposed to improve the power output of these muscles. Some of them aim for hypertrophy and others for specific adaptations of the nervous system. This includes general (hypertrophy and neuronal activation), velocity specific (speed-strength) and movement specific (sprint associated exercises) strength training. In developing training strategies, the coach has to keep in mind that strength, power and speed are inherently related to one another, because they are all the output of the same functional systems. As heavy resistance training results in a fibre type IIb into fibre type IIa conversion, the coach has to aim for an optimal balance between sprint specific and nonspecific training components. To achieve this they must take into consideration the specific strength training demands of each individual, based on performance capacity in each specific phase of the sprint.

Acceleration↗
PubMed2001

Factors affecting force loss with prolonged stretching.

The purpose of this study was to investigate the factors underlying the force loss occurring after prolonged, static, passive stretching. Subjects were tested before and 5-10 min following 20 min of static, passive stretching of the quadriceps (N=12) or a similar period of no stretch (control, N=6). Measurements included isometric maximal voluntary contraction (MVC) force, surface integrated electromyographic (iEMG) activity of the quadriceps and hamstrings, evoked contractile properties (twitch and tetanic force), and quadriceps inactivation as measured by the interpolated twitch technique (ITT). Following stretching, there was a significant 12% decrement in MVC with no significant changes in the control group. Muscle inactivation as measured by the ITT and iEMG increased by 2.8% and 20.2%, respectively. While twitch forces significantly decreased 11.7%, there was no change in tetanic force post-stretch. Although possible increases in muscle compliance affected twitch force, a lack of tetanic force change would suggest that post-stretch force decrements are more affected by muscle inactivation than changes in muscle elasticity.

Adult↗
PubMedDate not supplied

Coactivation patterns of the medial and lateral hamstrings based on joint position and movement velocity during isokinetic movements.

The purpose of this investigation was to determine the effect of movement velocity (100 degrees x s(-1), 200 degrees x s(-1), 300 degees x s(-1), and 400 degrees x s(-1)) and joint position (0 degrees - 20 degrees [L0] 30 degrees - 50 degrees [L30], and 70 degrees - 90 degrees [L70] knee flexion) on reciprocal coactivation patterns of the medial and lateral hamstrings as determined by the amplitude and frequency spectrum of surface electromyography (SEMG). Thirteen female 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 biceps femoris (BF) and medial hamstrings (MH) for determination of the root mean square (SEMGrms) and median frequency (SEMGmf) of the SEMG. Normalized SEMGrms values for the MH and BF were determined as a percentage of agonist SEMGrms activity for the same muscle during its agonist phase. Data were analyzed using separate 2 x 3 x 4 (muscle x position x angular velocity) repeated measures analysis of variance (ANOVA). For SEMGrms, there were significant muscle (p < 0.01) and position (p < or = 0.0001) main effects. Post-hoc analyses indicated the BF displayed greater muscle amplitude than the MH and that there was greater muscle amplitude at the L0 position (as the knee approached terminal extension). No velocity effect was noted (p > 0.05). For SEMGmf there were muscle x position (p < or = 0.05) and muscle x position x velocity (p < or = 0.01) interaction effects. Post-hoc analyses indicated the BF displayed a higher frequency spectrum than the MH at the L0 position. Secondly, velocity affected the BF and MH frequency spectrum such that values for both the MH and BF were lowest at 200 degrees x s(-1) and highest at 300 degrees x s(-1) (BF) and 400 degrees x s(-1) (MH). Velocity had little impact on the frequency spectrum in the midrange of the ROM (L30 position). Higher SEMGrms and SEMGmf values for the BF could be explained by the locking or screw home mechanism of the knee, and a way in which the human motor control system provides the limb with a dynamic braking system to control both extension and lateral rotational forces during the final stage of knee extension. It would appear that the way in which the body performs this function is not only to increase the amplitude of BF muscle firing but also to shift toward the recruitment of more fast-twitch motor units.

Adult↗
PubMed2003

Evaluation of a lower-body compression garment.

The aims of this study were to determine how custom-fit compression shorts affect athletic performance and to examine the mechanical properties of the shorts. Ten male and 10 female track athletes on a university's nationally competitive track team, specializing in sprint or jump events, participated in the study. Testing utilized the compression shorts with loose-fitting gym shorts as the control garment. Several significant effects were revealed for the custom-fit compressive garment. Although 60 m sprint time was not affected, hip flexion angle was reduced. Skin temperature increased more and at a faster rate during a warm-up protocol. Muscle oscillation was decreased during vertical jump landing. Countermovement vertical jump height increased when the participants were wearing the custom-fit compression garment. In materials testing, the elasticity of the compressive garment provides increased flexion and extension torque at the end range of extension and flexion, respectively, and may assist the hamstrings in controlling the leg at the end of the swing phase in sprinting. The compressive garment significantly reduced impact force by 27% compared with American football pants alone. Through various mechanisms, these findings may translate into an effect on athletic performance and a reduction in injuries.

Adult↗
PubMed1997

Isokinetic performance of the thigh muscles after tibial plateau fractures.

The isokinetic performance of thigh muscles was evaluated in 37 patients at an average of 7 years after sustaining a fracture of the tibial plateau. The mean torque deficit in the quadriceps of the injured limb was an average of 15% at a speed of 60 degrees/s and 16% at 180 degrees/s, while the corresponding deficits in the hamstrings were 3% and 8%. The radiological appearance of the injured knee correlated significantly to the quadriceps deficit at both speeds. Limited knee movement and thigh atrophy also correlated with the deficit at the lower speed. The strength deficit tended to decrease during follow-up. A multiple step-wise regression analysis showed that the radiological result, length of follow-up and thigh atrophy accounted for 47% of the variation in loss of quadriceps strength. At the higher speed, the functional result was associated with the deficit in quadriceps strength, and older patients had greater deficits than younger. Regression analysis indicated that the radiological and functional result accounted for 31% of the variation in quadriceps strength. Anatomical restoration of the tibial plateau and good muscle rehabilitation are important in obtaining good long term results after this fracture.

Adolescent↗
PubMed2000

[Mechanical properties of suture materials for anchoring cruciate ligament transplants].

The fixation of hamstring grafts in ACL reconstruction requires a connector device. During the process of ingrowing the graft stability depends entirely on the fixation. The following study focused on the mechanical conditions of no 6 Ethibond, 5 mm Mersilene tape and 5 mm Polylene tape. The material were tested as loops with a length of 30 mm including the knot similar to intraoperative conditions. The ultimate tension load and elongation of the conditioned and unconditioned loops were investigated under cyclic load of 50 N and 100 N using a tension load machine. The ultimate tension load increased significantly only for Mersilene from 416 N to 462 N. However, the highest ultimate tension load showed Polylene with 479 N. The oscillating load up to 100 N revealed for unconditioned loops an elongation of 4.1 mm for Ethibond, 2.9 mm for Polylene and 5.4 mm for Mersilene. The elongation decreased significantly for the conditioned loops to a maximum of 1.4 mm. Concerning the amplitude during the period of oscillating load there was found a significant reduction as well. Based on our results Polylene showed the best mechanical properties. Regardless the intraoperatively used material we advocate the conditioning of the loops before anchoring the hamstring graft in ACL reconstruction.

Anterior Cruciate Ligament↗
PubMed2007

Circumflex femoral vein thrombosis misinterpreted as acute hamstring strain.

The case of a 24-year-old female professional, long-distance runner who presented with acute proximal posterior thigh pain is reported. History and clinical findings were consistent with acute hamstring strain but MRI demonstrated circumflex femoral vein thrombosis. This is the first case of proximal posterior thigh pain caused by circumflex femoral vein thrombosis reported in the literature. Doctors dealing with sports injuries should be aware of this clinical entity that mimics hamstring strain.

Adult↗
PubMed1981

[Resection of the ischium in paraplegics (author's transl)].

A technique of resection of the ischium in paraplegics is described. It aims to avoid pressure sores arising from the development of hygromata in active paraplegics. The resection must be complete, subperiosteal and bilateral when necessary. A muscular plasty must be made by suturing the hamstrings to the pyriformis and gluteus medius.

Humans↗
PubMed2002

Explosive power and asymmetry in leg muscle function in frequent fallers and non-fallers aged over 65.

BACKGROUND: although low strength is a risk factor for falls, lower limb explosive power is more predictive of functional difficulties than strength. Power may be more predictive of a future fall than strength per se. OBJECTIVE: to compare leg muscle strength and explosive power and asymmetry of leg strength and power of women aged 65 or over living at home, with and without a history of falls. DESIGN: a case controlled study of self-reported 'fallers' versus 'non-fallers'. SUBJECTS: twenty women, aged 65 or over, with a history of at least three falls in the previous year were age matched with 15 women with no history of falls in the previous year. METHODS: lower limb explosive power, isometric strength of the quadriceps and hamstrings, isokinetic concentric strength (100 degrees/sec) of the quadriceps, hamstrings, ankle plantar- and dorsi-flexors and quadriceps eccentric strength (100 degrees/sec). Habitual physical activity was assessed using the self-completed Habitual Activity Profile Questionnaire. RESULTS: the women with a history of falls were less active but were not significantly weaker in any of the strength measurements, apart from ankle dorsiflexion adjusted for body weight. Both groups had significant asymmetry in all the leg muscles for both strength and power. Although both groups were asymmetrical in their lower limb power, the fallers demonstrated a significantly greater asymmetry. When the least powerful legs were compared, the women with a history of falls were 24% less powerful for their weight than those who did not fall (P=0.04). CONCLUSIONS: weakness and asymmetry is prevalent in women aged 65 and over, with and without a history of falls. Poor lower limb explosive power combined with asymmetry between limbs may be more predictive of future falls than more traditional measurements of strength in older women who live independently.

Accidental Falls↗
PubMed2003

Relation between isokinetic muscle strength and functional capacity in recreational athletes with chondromalacia patellae.

OBJECTIVES: To investigate the effects of isokinetic exercise on pain and functional test scores of recreational athletes with chondromalacia patellae (CMP) and to examine the correlation between isokinetic parameters and functional tests or pain score. METHODS: The functional ability of 30 recreational athletes with unilateral CMP was evaluated using six different tests. Pain scores were assessed during daily activities before and after the treatment protocol. Isokinetic exercise sessions were carried out at angular velocities of 60 degrees /s (25-90 degrees range of flexion) and 180 degrees /s (full range). These sessions were repeated three times a week for six weeks. RESULTS: Quadriceps and hamstring peak torque, total work, and endurance ratios had improved significantly after the treatment, as did the functional parameters and pain scores. There was a poor correlation between the extensor endurance ratio and one leg standing test. A moderate correlation between the visual analogue scale and the extensor endurance ratio or flexion endurance ratio was also found. CONCLUSIONS: The isokinetic exercise programme used in this study had a positive effect on muscle strength, pain score, and functional ability of knees with CMP. The improvement in the functional capacity did not correlate with the isokinetic parameters.

Adult↗
PubMed2004

Anterior cruciate ligament reconstruction with doubled semitendinosus and gracilis tendon graft in rugby players.

The purpose of this study was to evaluate prospectively the results of anterior cruciate ligament (ACL) reconstruction with doubled hamstring tendon graft in a selected group of 18 rugby players. The graft was fixed with a transcondylar screw (Transfix) on the femur, and with an absorbable interference screw and a metallic staple on the tibia. All the patients followed the same rehabilitation program. Return to sports activities was allowed after 6 months. Follow-up was 2 years in all cases. The athletic level of the patients was rated according to the Tegner scoring system. Clinical results were evaluated using the International Knee Documentation Committee (IKDC) scoring system. Furthermore, an instrumented evaluation of the anterior laxity with a KT-1000 arthrometer, and an isokinetic evaluation were performed 6 and 24 months after surgery. The Tegner mean score at follow-up (8.2) was similar to that prior to injury (8.3). IKDC overall results were normal in ten cases (55.6%), nearly normal in six cases (33.3%), and abnormal in two cases (11.1%). Side-to-side difference of anterior laxity measured with KT-1000 at 6 and 24 months did not show an impairment of knee stability with time. Isokinetic evaluation showed a significant improvement on peak torque both in extension and flexion on comparison between 6- and 24-month measurements. The results reported in this study showed that the use of doubled hamstring tendon graft for ACL reconstruction in athletes that were at risk for high-energy traumas to the knees, such as rugby players, gave normal or nearly normal results in about 90% of the cases. Recovery of muscle strength was almost complete 2 years after surgery, and there was no impairment of knee stability with time.

Adolescent↗
PubMed1992

Knee extensor and knee flexor strength: cross-sectional area ratios in young and elderly men.

The relationships between isometric and isokinetic-concentric knee extensor and knee flexor strength, and quadriceps and hamstring cross-sectional area (CSA) were determined in young (n = 13, M = 24.5y) and elderly (n = 12, M = 70.7y) men. Quadriceps and hamstring CSA was determined by computed tomography. Knee extensor and flexor strength at 0 degree/s and 120 degree/s was determined on a Kin-Com isokinetic dynamometer. Compared to the young men, elderly men had significantly smaller quadriceps muscles and were weaker (22-32%) in knee flexion and knee extension at both angular velocities. Strength:CSA ratios were similar at 0 degree/s, but elderly men had decreased ratios for both extensors and flexors at 120 degree/s. Correlations of knee extensor and flexor strength with muscle CSA were significant at both velocities in elderly men, but not at either velocity for the knee flexors in young men. The decrease in isometric strength in elderly men can be accounted for by their decrease in muscle CSA, but their decrease in isokinetic-concentric strength was greater than their loss of CSA. Further study is required to determine the reason for this nonproportional loss of isokinetic-concentric strength.

Adult↗
PubMed2003

[Post stroke hemiplegia: lower limb benefit from botulinum toxin (review)].

OBJECTIVE: To clarify the conditions governing the use of botulinum toxin (BTX) for post-stroke lower limb spastic disorders: indications, choice of muscles, doses, and duration of efficacy. METHOD: Review of the international literature using the Medline and the Reedoc data banks. RESULTS: Seven controlled studies were reviewed, including in particular 2 studies vs placebo and one vs phenol, 7 open studies or case series closely related to this topic and 4 open studies partly dedicated to it. The usefulness of BTX for the treatment of equinovarus has been demonstrated. The main muscles to be treated are the soleus, gastrocnemius and tibialis posterior. The treatment proposed for toe clawing is BTX injection into the flexor digitorum longus and flexor hallucis longus, and for great toe permanent extension, injection of the extensor hallucis longus. The quadriceps femoris, the tibialis anterior or the hamstrings have only be treated in isolated cases. When the treatment is effective, its benefit may last for more than 6 months. DISCUSSION: A few controlled trials have demonstrated the efficacy of BTX for post stroke lower limb spasticity. The results of all the controlled and open trials argue in favor of its efficacy, but this still requires more thorough analysis. CONCLUSION: Botulinum toxin has a place together with other local treatments for post-stroke spasticity, but a precise guide to its use, especially its dosage, and it's effectiveness compared to that of other treatments, need further study.

Anti-Dyskinesia Agents↗
PubMed2002

Arthroscopic reconstruction of the posterior cruciate ligament with quadruple hamstring tendon graft: a double fixation method.

BACKGROUND: Surgical reconstruction is indicated for posterior cruciate ligament (PCL) reconstruction for a grade III or IV injury, combined ligament or meniscus injuries, and chronic symptomatic posterior instability. Considerable controversy continues over the choice of graft tissues. Hamstring tendon has been popular in recent years. The purpose of this study is to prospectively assess the outcomes of PCL reconstruction using quadruple hamstring tendon autograft with a double-fixation technique at minimal 2-year follow-up. METHODS: Only patients who received PCL reconstruction without combined associated posterolateral injury reconstruction were included in the series. A hamstring tendon graft is composed of a quadruple-stranded semitendinosus tendon and gracilis tendon 10 cm in length. An arthroscopic technique using a two-incision method and a double-fixation technique were used. Clinical assessments were performed for 30 patients, of which 27 were available for final outcome analysis. Clinical review of patients included the Lysholm knee scores, International Knee Documentation Committee (IKDC) scores, thigh muscle assessment, and radiographic evaluation. RESULTS: On the Lysholm knee rating, 89% of the patients demonstrated good or excellent results in the final assessment. In the IKDC rating analyses, 56% of the patients revealed 3- to 5-mm ligament laxity. Four patients (15%) had grade II laxity. For the IKDC final rating, 26% were normal and 55% were nearly normal. Seventy-eight percent of the patients had less than a 10-mm difference in thigh girth between their reconstructed and opposite limbs. CONCLUSION: Arthroscopic PCL reconstruction with quadruple hamstring tendon autograft appears to produce acceptable results at a minimal 2-year follow-up. The four-stranded hamstring tendon graft is adequate in graft size and associated with minimal harvesting morbidity. The double-fixation method for the graft could provide a rigid fixation. We believe that this technique could afford good ligament function after reconstruction and could be a reasonably acceptable choice for PCL injury.

Adult↗
PubMed1997

Isokinetic strength training of the hemiparetic knee: effects on function and spasticity.

PURPOSE: To determine whether isokinetic training can improve the strength of the hemiparetic knee musculature, functional mobility, and physical activity and to evaluate its effect on spasticity in long-term stroke survivors. DESIGN: Nonrandomized self-controlled trial. SUBJECTS: A volunteer sample of 15 community-dwelling stroke survivors of at least 6 months. INTERVENTION: A 6-week (3 days/week, 40 minutes/day) program consisting of warm-up, stretches, reciprocal knee extension and flexion isokinetic strengthening, and cool-down for the paretic limb. MAIN OUTCOME MEASURES: Peak isokinetic hamstring and quadriceps torque, quadriceps spasticity, gait velocity, timed Up and Go, timed stair climb, and the Human Activity Profile (HAP) scores were recorded at baseline, after training, and 4 weeks after training cessation (follow-up). RESULTS: Paretic muscle strength improved after training (p < .05) while tone remained consistent (p > .87). Gait velocity increased after training (p < .05) and at follow-up (p < .05). Changes in stair climbing and timed Up and Go were not significant (p > .37; p > .91), although subjects perceived gains in their physical abilities at follow-up (p < .01). CONCLUSIONS: Gains in strength and gait velocity without concomitant increases in muscle tone are possible after a short-term strengthening program for stroke survivors. The psychological benefit associated with physical activity is significant.

Aged↗