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The purpose of this article was to review the literature on passive extensibility of skeletal muscle with reference to its anatomic and physiologic properties, mechanisms of adaptations and clinical implications. Studies with animal muscles have shown that passive extensibility is influenced by the size (mass) and length of muscle fibers, and the amount and arrangement of the connective tissues of the muscle belly. The resistance to passive lengthening is influenced by the readily adaptable amount of muscle tissue, including the contractile proteins and the non-contractile proteins of the sarcomere cytoskeletons. The relationship of adaptable changes in the muscle tissue and in the extracellular connective tissues remains unclear. Muscle length adaptations result from changes in the number of sarcomeres in series, which depend on the imposed length of muscles, not on the level of muscle activation and tension. This mechanism of muscle length adaptations, termed 'myogenic', has not been demonstrated in human muscles, but it has been intimated by therapeutic lengthening studies showing that both healthy and neurologically impaired human muscles can undergo increased length adaptations in the presence of muscle activations. Studies have suggested that optimal muscle function is probably achieved by increasing muscle length, length extensibility, passive elastic stiffness, mass and strength, but additional studies are needed to investigate these relationships, particularly for aged muscles and for muscles affected by clinical disorders, disease and injury. Such studies could contribute to the development of new intervention strategies designed to promote the passive muscle extensibility that enhances total muscle function, and ultimately improves the ability to complete functional activities and excel in athletic performances.

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Active supination and pronation range of motion of the right forearm by 10 men and 21 women were measured with a goniometer using three methods. For Method One the moveable arm was aligned with a pencil held in the hand; for Method Two the moveable arm was placed over the anterior and posterior surface of the distal forearm for supination and pronation, respectively; and for Method Three the moveable arm was aligned parallel with a visualized line connecting the distal ulna and radius. Supination range of motion was greatest for Method One, followed by Methods Three and Two, respectively. Pronation range for Method One was less than for the two other methods. Intraclass correlation coefficients ranged from .81 to .97 for three trials within the test session and from .86 to .96 between the test and a 1-hr. retest session for both actions using all three methods. Method One was the most reliable but appeared invalid for measuring supination because of movements of the 4th and 5th metacarpal bones. Methods Two and Three appeared appropriate for clinical application but not interchangeable.

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BACKGROUND AND PURPOSE: Therapeutic stretching of the calf muscle-tendon unit is used to increase its length and to ameliorate decreased dorsiflexion range of motion (ROM), but the influence of age on the passive properties of the calf muscle-tendon unit has not been studied adequately The purpose of this study was to examine the influence of age on length and passive elastic stiffness (PES) characteristics of the calf muscle-tendon unit when stretched through the full, available dorsiflexion ROM. SUBJECTS: Twenty-four younger women (aged 20-39 years), 24 middle-aged women (aged 40-59 years), and 33 older women (aged 60-84 years) participated. METHODS: An isokinetic dynamometer was used to passively stretch the right calf muscle-tendon unit from relaxed plantar flexion to the maximal angle of available dorsiflexion at 5(ús-1. The maximal passive resistive torque was measured, and passive angle-torque curves were constructed for a full ROM from an initial angle of passive resistive torque to the maximal dorsiflexion angle. The full ROM represented length extensibility. The average PES was calculated for this full stretch ROM and for the first half and the last half of this stretch ROM. The maximal passive dorsiflexion angle, maximal passive resistive torque, angular change for the full stretch ROM, and average PES for the full stretch ROM and the first half and the last half of the full stretch ROM were examined for group differences and their relationships with age. RESULTS: The maximal passive dorsiflexion angle, maximal passive resistive torque, angular change for the full stretch ROM, and average PES within the last half of the full stretch ROM were less for the older women than for the younger women. Age was negatively associated with these variables. CONCLUSION AND DISCUSSION: Decreased maximal passive dorsiflexion ROM in older women was associated with decreased maximal passive resistive torque, decreased calf muscle-tendon unit length extensibility, and decreased average PES within the last half of their available passive dorsiflexion ROM.

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STUDY DESIGN: Descriptive, comparative, and correlational study of nonimpaired, active women in 3 age groups. OBJECTIVES: We described age-related concentric isokinetic torque of plantar flexion (PF) of active women and examined the proposal that PF torque at slow to rapid velocities would be influenced by age-related slower muscle contractile properties. We also examined the relationship of age to passive and active force characteristics of the calf muscle. BACKGROUND: Aging is associated with decreased calf muscle strength, slower muscle contractile properties, and decreased dorsiflexion (DF) range of motion. Clinical methods of measuring these changes in the calf muscles have not been described adequately. METHODS AND MEASURES: 24 younger women (20 to 39 years), 24 middle-aged women (40 to 59 years), and 33 older women (60 to 84 years) performed maximal concentric PF of the right ankle from maximal passive DF at randomly ordered velocities of 30 degrees.s-1, 60 degrees.s-1, 120 degrees.s-1, and 180 degrees.s-1. The peak and mean torques and "angular delay" (degree) from the onset of movement to peak torque were examined using ANOVA. Age was correlated (Pearson product moment r) with the peak and mean torques, "angular delay," velocity at peak torque for 180 degrees.s-1, and the maximal passive DF angle and torque. RESULTS: The peak and mean torques decreased with increasing age and velocities. The angular delay at 180 degrees.s-1 decreased with increasing age. Age was negatively correlated with the peak and mean torques (range, r = -0.60 to -0.73), the "angular delay" at all velocities (range, r = -0.44 to -0.64), the maximal passive DF angle (r = -0.73) and torque (r = -0.60), and with the peak torque velocity at 180 degrees.s-1 (r = -0.29). CONCLUSIONS: The results indicate age-related changes for the concentric isokinetic torque of the calf muscles of active women. The angular delay at 180 degrees.s-1 may show changes influenced by slower muscle contractile properties. Concurrent age-related declines in passive and active calf muscle force characteristics were demonstrated.

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This study examined the ability to control leg velocities during concentric and eccentric actions of the right quadriceps muscles. Ten healthy women (M age = 25.9 +/- 3.5 yr.) were tested using the Isotonic Program of the KIN-COM II 500H dynamometer. They attempted to match velocity tracings of 10 degrees, 20 degrees, and 40 degrees/sec. through 70 degrees of knee range of motion at a load equal to 10% of their maximal mean concentric force. The actual mean velocities, mean percent deviation from the target velocities, and the coefficient of variation for both actions were calculated for 15 degrees-75 degrees (full range of motion), 15 degrees-45 degrees (shorter range of motion), and 46 degrees-75 degrees (longer range of motion). Separate one-way analyses of variance with two trial factors (action x velocity) showed faster concentric velocities through the full and longer ranges of motion, and faster eccentric velocities through the shorter range of motion. Mean percent deviations indicated that the eccentric velocities were generally more accurate within all ranges of motion. Larger concentric coefficients of variation were found within the full and longer ranges of motion, and the coefficients of variation for both actions decreased as the velocities increased. An exaggerated 'velocity overshoot' at the onset of both actions probably contributed to differences in the velocities and coefficients of variation. The results indicated differences between the concentric and eccentric actions, explained in part by the testing methodology used and by the known mechanical and physiological characteristics of the two muscle actions.

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The purpose of this study was to investigate the influence of age on concentric isokinetic torque (CIT) and passive extensibility (PE) variables of the calf muscles of healthy women. Ten younger women [31.9 (SD 6.1) years] and ten older women [71.1 (SD 6.6) years] were tested using a KIN-COM 500H dynamometer. The PE was tested by stretching the muscles from relaxed plantarflexion to the maximal dorsiflexion (DF) angle at 5 degrees.s-1 without raw electromyogram (EMG) activity exceeding 0.05 mV. The maximal CIT was tested from the maximal DF angle 60 degrees into plantarflexion at four randomly ordered velocities of 30,60, 120, and 180 degrees.s-1. Separate analysis of variance (ANOVA) tests showed that the standardized (% body mass) concentric peak and mean torques were lower for the older women for all isokinetic velocities (p < 0.001). The "angular delay" from the onset of concentric activation to peak torque was smaller for the older women at 120 and 180 degrees.s-1 (p < 0.05). Age showed negative relationships (Pearson r) with all standardized peak torques (p < or = 0.001) and mean torques (p < 0.001), and the "angular delay" at 120 and 180 degrees.s-1 (p < or = 0.05). Independent t-tests showed that the maximal DF angle and the change in the PE angle from an initial angle (defined at 10% of the maximal passive torque) to the maximal DF angle were less for the older women (p < 0.05). Age was negatively related to the maximal DF angle and the change in the PE angle (p < 0.01). The results suggest an age-related decrease in calf muscle CIT, muscle length and PE. The smaller "angular delay" for the older women at 120 and 180 degrees.s-1 indicates that CIT testing at rapid velocities can be used to examine age-related changes in calf muscle contractile properties in relation to rapid velocities of movement.

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Hamstring muscle length may be associated with specific pelvic and trunk postures, but the influence of hamstring length on trunk postures is not well documented. The purposes of this study were to examine the influence of hamstring length on 1) the pelvic angle, lumbar angle, and thoracic angle in standing; and 2) the flexion ranges of motion of the pelvic angle, lumbar angle, and thoracic angle during the toe-touch test. Surface platform pointers over bony landmarks and photography were used to examine the pelvic and trunk angles and ranges of motion of 10 men with short hamstrings, 10 men with medium hamstrings, and 10 men with long hamstrings while standing and after assuming the toe-touch position. Separate one-way analyses of variance detected no significant differences among groups for the three angles in standing. Significant differences were detected among groups for the three angles in the toe-touch position and the flexion ranges of motion during the toe-touch test (p < 0.05). Short hamstrings were associated with decreased flexion range of motion of the pelvic angle and lumbar angle and increased flexion range of motion of the thoracic angle. Therapeutic interventions should be considered in light of the influences of hamstring length on the flexion range of motion of the pelvic angle, lumbar angle, and thoracic. angle.

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The quadriceps femoral angle (Q angle) has been linked with several knee disorders, but Q-angle measurement procedures have not been standardized. The purpose of this study was to examine the effects of isometric quadriceps contraction in the standing and supine positions on the Q angle. The Q angles of the right knees of 30 men and 30 women were measured goniometrically during four test conditions: 1) quadriceps relaxed in standing, 2) quadriceps contracted in standing, 3) quadriceps relaxed in supine, and 4) quadriceps contracted in supine. The pelvic widths were also measured as the distance between the anterior superior iliac spines in standing and supine. A two-way multivariate analysis of variance showed a significant difference between genders (p < 0.001) and among the four test conditions (p < 0.001) (N = 60). Separate one-way analyses of variance (ANOVAs) with two grouping factors (contraction and position) showed significant effects of contraction (p < 0.001) for both men and women, but no significant effect of positions. A dependent t-test showed that the pelvic width differed between standing and supine for both men and women (p < 0.001). The results showed that isometric quadriceps contraction affects the Q angle with the subjects standing or supine, even though the pelvic width differed significantly between the two positions. Clinicians and researchers should consider the results of this study in order to standardize procedures for measuring the Q angle.

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This preliminary study examined the effects of full elbow flexion and full elbow extension on the end-point of active range of motion of shoulder flexion and shoulder extension respectively. The end-points were measured from lateral photographs of the right upper limbs of 30 men after they flexed and extended their shoulders with their elbows held in full flexion and full extension. Angular measurements showed that full elbow flexion limited shoulder flexion range of motion and that full elbow extension limited shoulder extension range of motion. The results indicated that passive muscle insufficiency of active shoulder flexion and extension was probably brought about by lengthening the triceps brachii and the biceps brachii muscles respectively. Clinicians are encouraged to considerthis passive insufficiency when measuring range of motion of shoulderflexion and extension and when implementing therapeutic interventions.

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Several indirect clinical tests for measuring hamstring muscle length are available, but the influence of their test procedures is not well documented. This study examined four of these tests to clarify the results relative to the testing procedures. The right limbs of 30 men were tested for: 1) passive straight leg raise (SLR) with the pelvis and opposite thigh stabilized with straps (SLR-SS); 2) passive SLR with the low back flat and, if needed, the opposite thigh slightly flexed and supported on pillows (SLR-LBF); 3) active knee extension with the hip at 90 degrees (AKE); and 4) passive knee extension with the hip at 90 degrees (PKE). A dependent t-test showed no significant differences between the angles of SLR-SS (61 degrees +/- 6.7 degrees) and SLR-LBF (62 degrees +/- 6.2 degrees). The SLR-SS and SLR-LBF angles for subjects needing pillows under the opposite thigh for the SLR-LBF test (N = 18) also were not significantly different. The knee flexion angles for the AKE (43 degrees +/- 10.2 degrees) and the PKE (31 degrees +/- 7.5 degrees) tests were significantly different (p < 0.001). Significant relationships (Pearson r) were found among the four tests (p < 0.05). The similar angles for SLR-SS and SLR-LBF and their significant relationship (r = 0.70, p < 0.001) indicated that their different testing procedures probably had a minimal influence on test results. The difference between the AKE and PKE tests suggested that the AKE test and the PKE test may represent an "initial length" and a "maximal length," respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

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The ability to measure the stretch-shortening cycle of isolated muscle groups has been limited. The purpose of this study was to measure the stretch-shortening cycle of the quadriceps femoris muscle group. Twenty-four volunteer subjects, 12 men and 12 women, participated in one test session; five men and five women also participated in a retest session; to examine the reliability of the test. A concentric contraction of the left quadriceps was measured for peak torque and time to peak torque on a Biodex isokinetic dynamometer under three conditions: 1) passive stretch before a concentric contraction, 2) isometric preload before a concentric contraction, and 3) eccentric preload before a concentric contraction. Conditions 2 and 3 showed a significant increase in peak torque production compared to condition 1 (p < 0.01). A significant difference was found for all three conditions between the men and women, with the men producing greatest peak torques. Conditions 2 and 3 also showed a significantly decreased time to peak torque compared with condition 1 (p < 0.01). The testing protocol was found to have high reliability. This testing protocol could be used to further study the stretch-shortening cycle in the quadriceps femoris muscle group.

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This study examined the influence of short hamstring muscles of healthy men on: (1) the angles of pelvic inclination and the lumbar curve in standing, and (2) the flexion range of motion of the pelvis and lumbar spine during the toe-touch test. Surface markers over bony landmarks and photography were used to examine ten men without short hamstrings and ten men with short hamstrings while standing and after assuming the toe-touch position for two repeated trials. ANOVAS showed no significant differences between groups for the angles of pelvic inclination and lumbar curve in standing. During the toe-touch test, the mean flexion range of motion of the pelvis on the thigh was less for the men with short hamstrings (52°; SD, 9°) than for the men without short hamstrings (72°; SD, 4°) (P < 0.001), but the lumbar flexion range of motion was not significantly different.

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This project was supported in part by a grant from The Foundation for Physical Therapy, 1111 North Fairfax Street, Alexandria, VA 22314 Foreshortened hamstring muscles have been associated with various clinical disorders. This study examined the effects of three weeks of daily static stretching of short hamstrings on passive straight leg raising (SLR), maximal hamstring length (MHL), and their maximal resistance to passive stretch (MRPS). Twenty-four healthy men (18-37 yrs) with SLR 50 muV) from the hamstrings was observed. The knee angle represented MHL, and MRPS (torque in nm) was calculated. Subjects in the stretching group completed daily static stretching of the hamstrings for three weeks. After three weeks, SIR increased for the stretching group, but not for the control group (< 0.001). The knee angle for the stretching group was less than the control group (p < 0.001), and the MRPS for the stretching group exceeded the control group (p < 0.05). The results indicated that static stretching increased SLR with concomitant increases in the MHL and the MRPS. The results also support using SLR as a valid clinical test for measuring hamstring length changes resulting from therapeutic interventions. J Orthop Sports Phys Ther 1991;14(6):250-255.

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This study examined the passive compliance and length of short hamstring muscles in relation to hamstring muscles not considered short in healthy men (ages 18-37). The right hamstrings of 30 men with straight-leg raising of 73.8° (group I) and 24 men with straight-leg raising of 61.0° (group 11) were compared. Subjects were positioned on their left sides with the pelvis stabilized and the right thigh fixed at 90°. Subjects received three maximal passive knee extension trials for data collection. Muscle activity was monitored with surface electromyography and passive resistance was measured with a dynamometer as the limb was photographed at force-dependent positions. Passive compliance was computed as the ratio of change in the knee angle to change in passive torque. Hamstring lengths were measured simultaneously. Results showed that the passive compliance curves for group II were shifted left compared to group I. Anovas revealed that the initial knee angles for group 11 were greater than for group I (P = 0.001), as were the maximal knee angles (P < 0.001). Passive compliance ratios for group 11 (1.29) were less than for group I (1.45), but not significantly different. Maximal passive torques were not different between groups. The change from initial muscle lengths to maximal lengths was less for group 11 than group I for the: (1) absolute length change (P = 0.027), (2) per cent change beyond initial length (P = 0.005), and (3) length change standardized as a percentage of femur length (P = 0.011).

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This study was designed to determine the extent to which knee flexion torques would differ when submaximal hamstring muscle contractions were evoked by constant levels of electrical stimulation and when the pelvifemoral angle was increased. Nineteen healthy subjects (ten women and nine men) underwent electrical stimulation of the hamstring muscles while randomly positioned either supine, sitting upright, or sitting leaning forward. The pelvifemoral angle for each position was measured from lateral photographs: the knee flexion torque was calculated from the knee flexion force, and lever arms measured directly at a constant knee angle. A repeated measures ANOVA demonstrated significant differences for pelvifemoral angles (F = 485·00, P < 0·001) and knee flexion torques (F = 21·97, P < 0·001) among the positions. The mean torques in the upright and leaning forward positions were 2·2 and 3·7 times greater, respectively, than mean torques in the supine position. The increase between the supine and leaning forward positions exceeded the increase previously reported in the literature for subjects performing maximal voluntary knee flexion efforts.

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This study examined the passive compliance and length of the hamstring muscles of 15 healthy men and 15 healthy women (ages 21-37) with passive straight-leg-raising between 65° and 80°. Subjects were positioned on their left sides with the pelvis stabilized and the right thigh fixed at 90° on a horizontal platform. After three practice trials of maximal passive knee extension, subjects received three trials for data collection. Muscle activity was monitored with surface EMG and passive resistance to knee extension was measured with a dynamometer as the limb was photographed at six force-dependent positions. The passive compliance was computed as the ratio of the change in the knee angle (ΔAngle) to the change in passive torque (ΔTorque), (ΔAngle/ΔTorque). Hamstring muscle lengths were measured simultaneously. An ANovA revealed a difference (P = 0·001) between the passive compliance ratios of the men (1·4 ± 0·-03) and women (2·2 ± 0·08) but not between their initial knee angles or their maximal knee angles. Independent t-tests showed a difference (P < 0·001) between the maximal passive torque of the men (41·4 ± 5·7 Nm) and women (27·4 ± 7·7 Nm). The torques were not different when standardized to body mass. Although ANOVAS showed that the absolute hamstring muscle lengths differed between genders, they were not different when standardized as a percentage of the femur length.

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The purpose of this study was to determine the effects of unilateral posterior mobilization and unilateral anterior mobilization of the sacroiliac joint (SIJ) on the standing position of the pelvis. Noninvasive methods were used to measure the position of the pelvis of 20 healthy men before and after SIJ mobilization. Ten subjects received posterior mobilization and 10 subjects received anterior mobilization. Two test sessions were conducted to check measurement reliability, followed by mobilization and a third test session. Apparent leg lengths were also measured before and after mobilization. Reliability was fair to high for the measurements. ANOVA for repeated measures revealed significant differences (p < 0.05) among the three tests for two measurements; however, post hoc analysis showed no significant differences between the measurements before and after mobilization. Mobilization had no effect on leg lengths. The benefits of SIJ mobilization should be considered in spite of these nonsignificant results because a small sample size of healthy men was examined, and because small changes in SIJ relationships may be sufficient to relieve low back pain.J Orthop Sports Phys Ther 1988;10(3):77-84.