Passive compliance and length of the hamstring muscles of healthy men anc women

The Relation of Body Mass Index to Muscular Viscoelastic Properties in Normal and Overweight Individuals

Background: The body mass index (BMI) is closely related to fat tissue, which may have direct or indirect effects on muscle function. Previous studies have evaluated BMI and muscle viscoelastic properties in vivo in older people or individual sexes; however, the relationship between BMI and muscular viscoelastic properties is still unknown. Aims: The purpose of this study was to determine the correlation of BMI with muscular viscoelastic properties, and to compare these properties in a young sedentary population with normal and overweight individuals. Methods: A total of 172 healthy sedentary individuals (mean age, 26.00 ± 5.45 years) were categorized by sex (male and female) and BMI classification (normal (BMI, 18.50-24.99 kg/m²), overweight (BMI = 25.00-29.99 kg/m²)). Body weight was evaluated using an electronic scale, while height was measured using a standard stadiometer. BMI was calculated by dividing the weight in kilograms by the square of height in meters. The viscoelastic properties (tone, stiffness, and elasticity) of the biceps brachii (BB) and biceps femoris (BF) muscles were measured bilaterally using the MyotonPRO device at rest. Results: The bilateral BF tone and stiffness, right BB stiffness, and elasticity showed weak correlations with BMI in all participants. Furthermore, the bilateral BF tone and stiffness, right BB stiffness and elasticity, and left BB stiffness were weakly positively correlated with male sex. Only the right BB elasticity was weakly positively correlated with BMI in females (p < 0.05). No correlation with BMI was determined for other viscoelastic properties (p > 0.05). The overweight group showed increased bilateral BF stiffness and tone, right BB stiffness, and reduced bilateral BB elasticity compared to the normal-weight group (p < 0.05), while other viscoelastic properties were similar (p > 0.05). Greater bilateral BB tone, BF tone and stiffness, and lower BF elasticity were observed in males than in females (p < 0.05), but other viscoelastic properties were not significantly different (p < 0.05). No effect of BMI-sex interactions was found on viscoelastic properties (p > 0.05). Conclusions: The BB and BF viscoelastic properties were weakly correlated with BMI. Males showed greater muscle tone and stiffness, and lower elasticity. The overweight individuals showed increased stiffness and tone, particularly in lower extremities, and reduced elasticity in upper extremities. The effect of BMI-sex interactions on the viscoelastic properties was not clear. Higher BMI (increased mechanical load) might cause the human body to develop different muscular viscoelastic adaptations in the extremities.

Assessment of the Maximal Range of Motion from Initial Sensation of Stretching to the Limits of Tolerance

The aim of this study was to determine whether the first sensation of stretching (ROM_FSS) may predict the maximum range of motion (ROM_MAX) in male (N = 37) and female (N = 32) volunteer subjects, and to assess the reliability of the ROM perceived by subjects in relation to a pre-determined ROM (ROM_50%). Subjects attempted three experimental sessions with 48 hours between sessions 1 and 2 and 28 days between sessions 1 and 3. Within each session, five trials were performed with isokinetic equipment to assess posterior thigh muscle flexibility. The results revealed a strong and significant correlation between ROM_MAX and ROM_FSS for both sexes, females (r = 0.96, p < 0.001, R ² = 0.92) and males (r = 0.91, p < 0.001; R ² = 0.82). The accuracy of the model verified by the standard error of estimate (SEE) was high in the equations proposed for both female (SEE = 4.53%) and male (SEE = 5.45%). Our results revealed that ROM_FSS may predict the ROM_MAX for both male and female subjects. The ROM_FSS may contribute to the development of evaluation methods that do not subject the individuals to conditions that may include unnecessary risk of injury and is well suited to monitor the training process of stretching exercises with submaximal loads.

Passive stiffness of the hamstrings and the rectus femoris in persons after an ACL reconstruction

OBJECTIVES

The aim of the article is to investigate the passive stiffness (PS) of rectus femoris and hamstring muscles working for the knee joint in persons after anterior cruciate ligament (ACL) reconstruction surgery.

METHODS

Thirty subjects (8 women and 22 men) aged 19-46 (x = 28.2 ± 7) participated in the investigation; an experimental group comprised 15 persons (4 women and 11 men) who underwent ACL reconstruction surgery. The other persons had no knee injury and described themselves as healthy. All the subjects underwent an investigation of the PS of the hamstrings and the rectus femoris on the injured as well as on the healthy leg.

RESULTS

The data shows vital difference in the PS of the hamstring muscles between the healthy and injured limb (p < 0.05), a significant difference in the PS of the rectus femoris (p < 0.001) was noted. Furthermore, the PS level of the hamstring muscles of the operated limb in the experimental group is significantly different to the both legs in control group (p < 0.001).

CONCLUSIONS

Injury of the ACL results in a considerable increase in passive stiffness of the hamstring and rectus femoris muscles in both the injured leg and the healthy leg.

Association of Gastrocnemius Muscle Stiffness With Passive Ankle Joint Stiffness and Sex-Related Difference in the Joint Stiffness

Passive ankle joint stiffness is affected by all structures located within and over the joint, and is greater in men than in women. Localized muscle stiffness can be assessed by ultrasound shear wave elastography, and muscle architecture such as fascicle length and pennation angle can be measured by B-mode ultrasonography. Thus, the authors assessed localized muscle stiffness of the medial gastrocnemius (MG) with consideration of individual variability in the muscle architecture, and examined the association of the muscle stiffness with passive ankle joint stiffness and the sex-related difference in the joint stiffness. Localized muscle stiffness of the MG in 16 men and 17 women was assessed at 10° and 20° plantar flexion, neutral anatomical position, and 10° and 20° dorsiflexion. Fascicle length and pennation angle of the MG were measured at these joint positions. Passive ankle joint stiffness was determined by the ankle joint angle–torque relationship. Localized MG muscle stiffness was not significantly correlated with passive ankle joint stiffness, and did not show significant sex-related difference, even when considering the muscle architecture. This finding suggests that muscle stiffness of the MG would not be a prominent factor in determining passive ankle joint stiffness and the sex-related difference in the joint stiffness.

Relationship between mechanical factors and pelvic tilt in adults with and without low back pain

BACKGROUND

The assessment of the lumbo-pelvic complex parameters is the basic procedure during the examination of the patients with low back pain syndrome (LBP).

OBJECTIVE

The aim of the study was to define the relationship between pelvic tilt and following factors: age, BMI, ability to activate deep abdominal muscles, iliopsoas and hamstrings muscles length, lumbar lordosis and thoracic kyphosis angle value, in adults with and without low back pain.

METHODS

The study covered a group of 60 female students aged 20-26. Average age was 22 years ± 1.83 (median = 22.5 years). In order to investigate the relationship between the anterior pelvic tilt and the analysed variables, simple linear regression and multiple linear regression were carried out.

RESULTS

Individuals with and without pain differed significantly in terms of age, p < 0.001. There was a statistically significant relationship between the anterior pelvic tilt and the LBP (R2 = 0.07, p = 0.049) and the lumbar lordosis (R2 = 0.13, p = 0.02).

CONCLUSIONS

The position of the pelvis depends on age, angle value of lumbar lordosis and BMI. Individuals with and without pain differed significantly in terms of the anterior pelvic tilt. The risk of LBP incidence increased with age in the study group.

Influence of age on passive stiffness and size, quality, and strength characteristics

INTRODUCTION

We examined the effects of aging on passive stiffness, size, quality, and strength characteristics of the posterior hip and thigh muscles.

METHODS

Fifteen young (25 ± 3 years) and 15 old (72 ± 5 years) men participated in this study. Echo intensity (EI) and cross-sectional area (CSA) were determined from ultrasound scans of the hamstrings. Straight-leg raises were used to assess passive stiffness, which was calculated from the slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curve. Peak torque (PT) and rate of torque development (RTD) were assessed through maximal voluntary contractions.

RESULTS

Phase 2 slope and EI were higher (P ≤ 0.024), and CSA, PT, and RTD were lower (P ≤ 0.011) in the old compared with the young men; however, no difference (P = 0.145) was observed for phase 1 slope.

CONCLUSIONS

Decreases in muscle quality, as indicated by increases in EI, may contribute to the greater passive stiffness observed in older adults. Muscle Nerve 55: 305-315, 2017.

Influence of passive stiffness of hamstrings on postural stability

The aim of the study was to explore whether passive stiffness of the hamstrings influences the strategy of maintaining postural stability. A sample of 50 subjects was selected; the final analyses were based on data of 41 individuals (33 men, 8 women) aged 21 to 29 (mean = 23.3, SD = 1.1) years. A quasi- experimental ex post facto design with repeated measures was used. Categories of independent variables were obtained directly prior to the measurement of the dependent variables. In stage one of the study, passive knee extension was measured in the supine position to assess hamstring stiffness. In stage two, the magnitude of postural sway in antero-posterior direction was measured, while varying the body position on a stabilometric platform, both with and without visual control. The margin of safety was used as a measure of postural control. The magnitude of the margin of safety increased significantly between the open-eye and closed-eye trials. However, although we registered a visible tendency for a larger increase of the margin of safety associated with lower levels of passive hamstrings stiffness, no significant differences were found. Therefore, this study demonstrated that hamstring stiffness did not influence the strategy used to maintain postural stability.

A comparison of muscle stiffness and musculoarticular stiffness of the knee joint in young athletic males and females

The objective of this study was to investigate the gender-specific differences in peak torque (PT), muscle stiffness (MS) and musculoarticular stiffness (MAS) of the knee joints in a young active population. Twenty-two male and twenty-two female recreational athletes participated. PT of the knee joint extensor musculature was assessed on an isokinetic dynamometer, MS of the vastus lateralis (VL) muscle was measured in both relaxed and contracted conditions, and knee joint MAS was quantified using the free oscillation technique. Significant gender differences were observed for all dependent variables. Females demonstrated less normalized PT (mean difference (MD)=0.4Nm/kg, p=0.005, η(2)=0.17), relaxed MS (MD=94.2N/m, p<.001, η(2)=0.53), contracted MS (MD=162.7N/m, p<.001, η(2)=0.53) and MAS (MD=422.1N/m, p<.001, η(2)=0.23) than males. MAS increased linearly with the external load in both genders with males demonstrating a significantly higher slope (p=0.019) than females. The observed differences outlined above may contribute to the higher knee joint injury incidence and prevalence in females when compared to males.

Shear wave elastography of passive skeletal muscle stiffness: influences of sex and age throughout adulthood

BACKGROUND

Numerous structural and compositional changes - related not only to age, but also activity level and sex - may affect skeletal muscle stiffness across the adult age-span. Measurement techniques available thus far have largely limited passive stiffness evaluations to those of entire joints and muscle-tendon units. Shear wave elastography is an increasingly popular ultrasound technique for evaluating the mechanical properties of skeletal muscle tissue. The purpose of this study was to quantify the passive stiffness, or shear modulus, of the biceps brachii throughout adulthood in flexed and extended elbow positions. We hypothesized that shear modulus would be higher in males relative to females, and with advanced age in both sexes.

METHODS

Shear wave elastography quantified biceps brachii stiffness at 90° elbow flexion and full extension in a large sample of adults between 21 and 94 years old (n=133; 47 males).

FINDINGS

Regression analysis found sex and age were significant parameters for older adults (>60 years) in full extension. As expected, shear modulus values increased with advancing age; however, shear modulus values for females tended to be higher than those for males.

INTERPRETATION

This study begins to establish normative trends for skeletal muscle shear modulus throughout adulthood. Specifically, this work establishes for the first time that the higher passive joint torque often found in males relative to females likely relates to parameters other than muscle shear modulus. Indeed, perhaps increases in skeletal muscle passive stiffness, though potentially altering the length-tension curve, serve a protective role - maintaining the tendon-muscle-tendon length-tension curve within a functional range.

Quantitative and temporal differential recovery of articular and muscular limitations of knee joint contractures; results in a rat model

Joint contractures alter the mechanical properties of articular and muscular structures. Reversibility of a contracture depends on the restoration of the elasticity of both structures. We determined the differential contribution of articular and muscular structures to knee flexion contractures during spontaneous recovery. Rats (250, divided into 24 groups) had one knee joint surgically fixed in flexion for six different durations, from 1 to 32 wk, creating joint contractures of various severities. After the fixation was removed, the animals were left to spontaneously recover for 1 to 48 wk. After the recovery periods, animals were killed and the knee extension was measured before and after division of the transarticular posterior muscles using a motorized arthrometer. No articular limitation had developed in contracture of recent onset (≤2 wk of fixation, P > 0.05); muscular limitations were responsible for the majority of the contracture (34 ± 8° and 38 ± 6°, respectively; both P < 0.05). Recovery for 1 and 8 wk reversed the muscular limitation of contractures of recent onset (1 and 2 wk of fixation, respectively). Long-lasting contractures (≥4 wk of fixation) presented articular limitations, irreversible in all 12 durations of recovery compared with controls (all 12 P < 0.05). Knee flexion contractures of recent onset were primarily due to muscular structures, and they were reversible during spontaneous recovery. Long-lasting contractures were primarily due to articular structures and were irreversible. Comprehensive temporal and quantitative data on the differential reversibility of mechanically significant alterations in articular and muscular structures represent novel evidence on which to base clinical practice.

Influence of hamstring muscles extensibility on spinal curvatures and pelvic tilt in highly trained cyclists

The purpose of this study was to determine the influence of hamstring muscles extensibility in standing, maximal trunk flexion with knees extended and on the bicycle in lower handlebar-hands position of highly trained cyclists. Ninety-six cyclists were recruited for the study (mean ± SD, age: 30.36 ± 5.98 years). Sagittal spinal curvatures and pelvic tilt were measured in the standing position, maximal trunk flexion with knees extended (sit-and-reach test) and while sitting on a bicycle in lower handlebar-hand position using a Spinal Mouse system. Hamstring muscles extensibility was determined in both legs by passive straight leg raise test (PSLR). The sample was divided into three groups according to PSLR angle: (1) reduced extensibility (PSLR < 80º; n = 30), (2) moderate hamstring extensibility group (PSLR = 80º - 90º; n = 35), and (3) high hamstring extensibility (PSLR = > 90º; n = 31). ANOVA analysis showed significant differences among groups for thoracic (p < 0.001) and pelvic tilt (p < 0.001) angles in the sit-and-reach test. No differences were found between groups for standing and on the bicycle position. Post hoc analysis showed significant differences in all pairwise comparisons for thoracic angle (p < 0.01) and pelvic angle (p < 0.001) in the sit-and-reach test. No differences were found in lumbar angle in any posture. In conclusion, the hamstring muscles extensibility influence the thoracic and pelvic postures when maximal trunk flexion with knees extended is performed, but not when cyclists are seated on their bicycles.

Selective strength loss and decreased muscle activity in hamstring injury

STUDY DESIGN

Cross-sectional, controlled laboratory study.

OBJECTIVES

To determine whether thigh muscle isokinetic torque patterns and activity, measured by electromyography (EMG), of individuals with hamstring injury differ from control individuals.

BACKGROUND

Neuromuscular control during thigh muscle strength assessment following hamstring injuries has not been reported.

METHODS

Fifteen athletes with prior hamstring injury (hamstring-injured group [HG]) were compared to 15 uninjured athletes (control group [CG]). The injuries were incurred 6 weeks to 12 months prior to participation, and all injured athletes had returned to at least partial training. Participants performed 5 isokinetic concentric extensor, concentric flexor, and eccentric flexor torque tests at 60°/s in the seated position. Peak torque was determined for each contraction type, as well as average torque for each of 4 time-based movement quartiles. EMG root-mean-squares were calculated in these movement quartiles for the biceps femoris and medial hamstrings.

RESULTS

No significant differences were found for peak torque for all contractions, when comparing HG injured and uninjured sides to CG bilateral averages. The HG injured limb eccentric flexor torque was significantly lower in the fourth quartile (approximately 25° to 5° knee flexion, hamstring lengthened range) compared to the CG bilateral average (P = .025). Eccentric flexor biceps femoris and hamstrings EMG root-mean-squares of the HG injured and the uninjured sides were significantly lower in the second to fourth quartiles (towards the lengthened range), compared to the CG bilateral averages (P<.05).

CONCLUSION

Decreased strength and EMG activation in a lengthened hamstrings range for the athletes with prior hamstring injury suggested a change in neuromuscular control. Lengthened range assessment of isokinetic eccentric flexor torque may be useful for the assessment of athletes with a prior injury; however, results should be confirmed with prospective studies.

Gender differences in musculotendinous stiffness and range of motion after an acute bout of stretching

The purpose of the present study was to examine musculotendinous stiffness (MTS) and ankle joint range of motion (ROM) in men and women after an acute bout of passive stretching. Thirteen men (mean ± SD age = 21 ± 2 years; body mass = 79 ± 15 kg; and height = 177 ± 7 cm) and 19 women (21 ± 3 years; 61 ± 9 kg; 165 ± 8 cm) completed stretch tolerance tests to determine MTS and ROM before and after a stretching protocol that consisted of 9 repetitions of passive, constant-torque stretching. The women were all tested during menses. Each repetition was held for 135 seconds. The results indicated that ROM increased after the stretching for the women (means ± SD pre to post: 109.39° ± 10.16° to 116.63° ± 9.63°; p ≤ 0.05) but not for the men (111.79° ± 6.84° to 113.93° ± 8.15°; p > 0.05). There were no stretching-induced changes in MTS (women's pre to postchange in MTS: -0.35 ± 0.38; men's MTS: +0.17 ± 0.40; p > 0.05), but MTS was higher for the men than for the women (MTS: 1.34 ± 0.41 vs. 0.97 ± 0.38; p ≤ 0.05). electromyographic amplitude for the soleus and medial gastrocnemius during the stretching tests was unchanged from pre to poststretching (p > 0.05); however, it increased with joint angle during the passive movements (p ≤ 0.05). Passively stretching the calf muscles increased stretch tolerance in women but not in men. But the stretching may not have affected the viscoelastic properties of the muscles. Practitioners may want to consider the possible gender differences in passive stretching responses and that increases in ROM may not always reflect decreases in MTS.

Biomechanical effects of patellar positioning on intraoperative knee joint gap measurement in total knee arthroplasty

BACKGROUND

Balancing both the lateral/medial and extension/flexion joint gaps is a prerequisite for soft tissue balance in total knee arthroplasty. The purpose of this study was to quantify the effects of patellar positioning and quadriceps load during total knee arthroplasty on knee joint gap measurements.

METHODS

Eight fresh-frozen cadaveric knees ranging in age from 65 to 85 years old were used. Using a medial parapatellar approach, posterior cruciate ligament sacrificing total knee arthroplasty was performed. The specimens were mounted on a custom knee testing system that allowed the femur to be locked in position for knee extension or flexion. Patellar positions of eversion, reduction, and following repair of the arthrotomy were examined. The influence of quadriceps muscle load was investigated by varying the quadriceps load from 0 to 125N. The lateral and medial joint gaps, represented by the distance from the implanted femoral component surface to the cut tibia surface, were measured with 100N tibial distraction force using a 3D digitizer in both extension (0 degrees ) and flexion (90 degrees ).

FINDINGS

Both the medial and lateral joint gaps with patella eversion were significantly smaller than those with patellar reduction and arthrotomy repair (extension: all quadriceps loads, P<0.0002; flexion: quadriceps loads less than 75N, P<0.0002). In patella eversion, quadriceps loading decreased the lateral joint gap more than the medial joint gap in both extension and flexion; however, the effect was greater in knee flexion with significant differences seen at all quadriceps loads, whereas in extension significant differences were only seen for quadriceps loading of 75N and greater. Patella eversion also caused a lateral-posterior shift and external rotation of the tibia compared to the other conditions (P<0.005). With patella reduction and repair of the arthrotomy lower quadriceps loading decreased the extension gap significantly more than the flexion gap (P<0.01). Following repair of the arthrotomy higher quadriceps loading significantly decreased the flexion gap more than the extension gap (P<0.04).

INTERPRETATION

The patellar positioning and quadriceps muscle loading in total knee arthroplasty have a strong influence on intraoperative joint gap measurements.

Passive properties of the muscle-tendon unit: the influence of muscle cross-sectional area

The purpose of the present study was to examine the relationships among the passive properties of the muscle-tendon unit and muscle cross-sectional area (CSA). Our findings indicated significant relationships between muscle CSA and passive stiffness (P < 0.05; r = 0.830) and muscle CSA and passive energy absorption (P < 0.05; r = 0.765). Since passive stiffness and the ability to absorb passive energy decreases with many diseases, these findings may support the need to maintain or increase muscle CSA.

Predicting the loss of knee flexion during limb lengthening using inherent muscle length

Limb lengthening procedures can be associated with loss of range of knee movement, although the amount of knee flexion lost varies markedly between patients. The exact aetiology of this problem is not fully understood. This study investigates whether the amount of joint range that is lost during limb lengthening might be affected by the inherent passive compliance and length of the patients' soft tissues determined preoperatively. A simple mathematical model has been developed to calculate the inherent length and 'spare' length of the hamstring and quadriceps muscle groups in 28 patients undergoing limb lengthening procedures. The range of knee motion was recorded preoperatively and loss of movement recorded during follow-up. The results show a strong correlation between predicted 'spare' length of quadriceps and loss of knee flexion. An association was noted between loss of knee extension and the straight leg raise and correlation of knee extension and the spare length of the hamstrings. The straight leg raise test, and calculation of spare quadriceps length using our formula, as part of the preoperative assessment, can help predict which patient is at risk of a reduced range of motion of the knee.

Gender differences in pattern of hip and lumbopelvic rotation in people with low back pain

BACKGROUND

Findings from previous studies suggest gender may affect the pattern of hip and lumbopelvic motion during a multi-segmental movement. To date, no studies have examined movement patterns and low back pain symptom behavior during hip lateral rotation.

METHODS

Forty-six people (27 males and 19 females) with low back pain were examined. Three-dimensional kinematic data and low back pain symptoms were recorded during active hip lateral rotation. Percent of maximum lumbopelvic rotation was calculated for each 10% increment of maximum active hip lateral rotation.

FINDINGS

Men exhibited a greater percent of maximum lumbopelvic rotation (mean 49.3, SD 13.3) during the first 60% of hip lateral rotation than women (mean 36.2, SD 16.4) (P < 0.01). Nineteen (70.4%) of the men and seven (36.8%) of the women had pain with the hip lateral rotation test (P = 0.02).

INTERPRETATION

Men exhibited more lumbopelvic rotation in the early part of hip lateral rotation than women, and hip lateral rotation was more likely to be associated with symptoms in men than women. Greater lumbopelvic motion, earlier in hip lateral rotation, may make men more vulnerable to low back pain associated with hip lateral rotation. Factors that contribute to these gender differences should be investigated further.

Comparison of triceps surae structural stiffness and material modulus across sex

BACKGROUND

Dynamic joint stability is derived, in part, from active muscle stiffness. Previous research has identified greater structural musculotendinous stiffness in males than in females, suggesting potential sex differences in joint stability. However, structural stiffness is influenced by anthropometrics, and it is currently unclear if sex differences in musculotendinous stiffness are purely functions of anthropometrics or related to additional factors. The purpose of this investigation was to compare structural stiffness and material modulus of the triceps surae between sexes to determine the relative influence of anthropometrics. It was hypothesized that males would demonstrate greater structural stiffness and material modulus.

METHODS

Twenty male and 20 female individuals volunteered for participation. Active triceps surae structural stiffness was estimated from the damped frequency of oscillation of the shank about the ankle. Material modulus was calculated as the ratio of stress to strain, derived from estimates of triceps surae length and physiological cross-sectional area.

FINDINGS

Structural stiffness was significantly greater in males [mean (SD)] [137.41 (26.99) N/cm] than females [91.06 (20.10) N/cm]. Similarly, material modulus was significantly greater in males [2778.51 (549.95) Pa] than females [1968.58 (439.61) Pa].

INTERPRETATION

Greater structural stiffness in males identified in previous literature appears to be a true phenomenon. Identification of greater material modulus in males suggests that these differences are likely attributable to sex differences in tendon stiffness and muscle architecture. These results indicate that male musculature is more effective at resisting changes in its length, a finding which may have implications for joint stability.

Sex comparison of extensibility, passive, and active stiffness of the knee flexors

OBJECTIVE

To compare extensibility, and passive and active stiffness of the knee flexors between males and females.

DESIGN

An experimental design utilized 15 males and 15 females to identify sex differences in active extensibility, and active and passive stiffness of the knee flexors.

BACKGROUND

Muscle stiffness appears to contribute to joint stability from both mechanical and neuromuscular perspectives. Differences in knee flexor stiffness may partially explain higher female anterior cruciate ligament injury rates.

METHODS

Active knee flexor extensibility was assessed as subjects extend the knee from a fixed hip position, measuring the final knee position. Passive knee flexor stiffness was calculated as the slope of the moment-angle curve resulting from controlled passive knee extension. Active knee flexor stiffness was assessed by loading the lower extremity with 10% total body mass, and measuring the damping effect of the knee flexors on imposed vibratory motion about the knee joint.

RESULTS

Females displayed greater active extensibility (P<0.05), while males displayed greater active (P<0.05) and passive (P<0.05) knee flexor stiffness. Sex differences in active and passive knee flexor stiffness were not significant following normalization to anthropometric characteristics.

CONCLUSIONS

The knee flexor musculature in males is less extensible and displays greater active and passive stiffness compared to females. However, these differences may be functions of greater mass and height in males.

The effect of either a pre or post exercise stretch on straight leg raise range of motion (SLR-ROM) in females

This study examined the order effect of a hamstring muscle stretch and resisted hamstring exercises on straight leg raise range of movement (SLR-ROM), in a group of twenty females aged 20-34 years. The stretch was applied either immediately before or Immediately after a resisted hamstring exercise. Exercise significantly decreased SLR-ROM (p < 0.05) and stretching significantly increased SLR-ROM (p < 0.05). The overall change in SLR-ROM for the two groups showed that a significant increase in SLR-ROM was detected (at a low force level) in Group 1 subjects who performed exercise and then stretched. A non-significant increase in SLR-ROM was detected by the higher force level in Group 1 subjects. In contrast, Group 2 subjects (stretch then exercise) showed a non-significant reduction in SLR-ROM at both levels of force.

Relationship between mechanical factors and incidence of low back pain

STUDY DESIGN

A multifactorial cross-sectional nonexperimental design.

OBJECTIVES

To collectively investigate the association among 17 mechanical factors and occurrence of low back pain (LBP).

BACKGROUND

Several physical characteristics, based on assumptions, clinical findings, and scientific experiments, have been associated with the development of LBP Controversy exists regarding the degree of association between some of these physical characteristics and LBP. Information regarding the degree of association of each factor to LBP is needed for effective prevention and appropriate treatment strategies.

METHODS AND MEASURES

A total of 600 subjects participated in this study. Subjects were categorized into 4 groups: asymptomatic men (n = 150, age [mean +/- SD] = 43 +/- 15 years), asymptomatic women (n = 150, age [mean +/- SD] = 43 +/- 13 years), men with LBP (n = 150, age [mean +/- SD] = 43 +/- 14 years), and women with LBP (n = 150, age [mean +/- SD] = 43 +/- 13 years). Seventeen physical characteristics were measured in each group and the relative association of each characteristic with LBP was assessed.

RESULTS

Among all the factors tested, endurance of the back extensor muscles had the highest association with LBP Other factors such as the length of the back extensor muscles, and the strength of the hip flexor, hip adductor, and abdominal muscles also had a significant association with LBP.

CONCLUSION

It appears that muscle endurance and weakness are associated with LBP and that structural factors such as the size of the lumbar lordosis, pelvic tilt, leg length discrepancy, and the length of abdominal, hamstring, and iliopsoas muscles are not associated with the occurrence of LBP.

Sensorimotor deficits contributing to glenohumeral instability

The conventional perspective has been that capsuloligamentous structures act as a mechanical restraint to humeral translation at the shoulder. Although this is true, the capsuloligamentous structures also have a sensorimotor influence on the musculoskeletal system, providing stability at the shoulder. The purpose of the current study was to discuss the sensorimotor role that the capsuloligamentous structures play in providing stability, how these mechanisms are disrupted with glenohumeral instability, and how surgical intervention restores such mechanisms. Proprioceptive information transmitted from the mechanoreceptors embedded within the capsuloligamentous structures influence the coordinated motor patterns, reflex activity, and joint stiffness to provide enhanced joint stability. The capsuloligamentous injury that occurs with shoulder instability not only affects mechanical restraint, but also alters this proprioceptive input to the central nervous system. As a result of these deficits in proprioception, alterations in reflex activity and motor programs as evident by muscle firing pattern alterations manifest. Although the main goal of surgical intervention is to restore the mechanical restraint that is lost with joint dislocation or subluxation, surgical intervention whether through open, arthroscopic, or thermal techniques seem to restore the proprioceptive deficits that exist after joint injury.

The Effect of General Anesthesia on Passive-Knee-Extension Range of Motion

Context:

Flexibility is promoted as essential to physical fitness, but the mechanisms limiting it are not fully understood.

Objective:

To investigate the effects of general anesthesia on hamstring extensibility.

Design:

Repeated measures.

Setting:

Hospital operating room.

Subjects:

Eight volunteers undergoing orthopedic surgeries unrelated to the tested limb.

Measurement:

Three measurements of passive knee extension (PKE) taken before and after administration of general anesthesia. The force applied during the measurements was consistent between trials.

Results:

Mean PKE range of motion (ROM) was significantly greater before anesthesia (75.0° ± 11.8°) than after (53.3° ± 17°;t= 5.6,P< .001). Pearson product correlation revealed a significant correlation between the mean difference in PKE ROM between treatment conditions and subjects’ body weight (r= .91,P< .05).

Conclusions:

The findings might be attributable to diminished neural drive to the antagonist muscle groups and suggest a more complex neural control of flexibility than simply neural drive to an agonist muscle.

The effects of a Feldenkrais program and relaxation procedures on hamstring length

Despite the growing popularity of the Feldenkrais method in Australia (Wildman 1990b), little research is available investigating its efficacy. The current study investigated the effects of the Feldenkrais method on hamstring length. Forty-eight healthy undergraduate participants were randomly allocated into either Feldenkrais, relaxation, or control groups. All subjects had their right hamstring measured using a modified active knee extension test prior to the first session, prior to the fourth (final) session, and after the final session of intervention. Two-way analysis of variance with time of measurement repeated revealed no significant differences between the groups. The findings are discussed in relation to apparent ineffectiveness of the Feldenkrais Awareness Through Movement lessons used on hamstring length, exposure time to the technique, and attitudes towards the Feldenkrais method.

Passive extensibility of skeletal muscle: review of the literature with clinical implications

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.

The role of passive muscle stiffness in symptoms of exercise-induced muscle damage

We examined whether passive stiffness of an eccentrically exercising muscle group affects the subsequent symptoms of muscle damage. Passive hamstring muscle stiffness was measured during an instrumented straight-leg-raise stretch in 20 subjects (11 men and 9 women) who were subsequently classified as "stiff" (N = 7), "normal" (N = 6), or "compliant" (N = 7). Passive stiffness was 78% higher in the stiff subjects (36.2 +/- 3.3 N.m.rad(-1)) compared with the compliant subjects (20.3 +/- 1.8 N.m.rad(-1)). Subjects then performed six sets of 10 isokinetic (2.6 rad.s(-1)) submaximal (60% maximal voluntary contraction) eccentric actions of the hamstring muscle group. Symptoms of muscle damage were documented by changes in isometric hamstring muscle strength, pain, muscle tenderness, and creatine kinase activity on the following 3 days. Strength loss, pain, muscle tenderness, and creatine kinase activity were significantly greater in the stiff compared with the compliant subjects on the days after eccentric exercise. Greater symptoms of muscle damage in subjects with stiffer hamstring muscles are consistent with the sarcomere strain theory of muscle damage. The present study provides experimental evidence of an association between flexibility and muscle injury. Muscle stiffness and its clinical correlate, static flexibility, are risk factors for more severe symptoms of muscle damage after eccentric exercise.

Kinematic characterization of standing reach: comparison of younger vs. older subjects

OBJECTIVE

To characterize typical spinal motions that occur during standing reach and to describe differences in spinal motions and center of pressure displacements during reach between younger and older healthy adults.

DESIGN

Exploratory, cross sectional investigation utilizing video motion and biomechanics force platform analysis.

BACKGROUND

Standing reach provides a means for assessing both arm function and balance control in the context of a common functional activity. The interaction between age-related declines in spinal mobility and the spinal motion occurring during reach is poorly understood. The characterization of spinal motions during task performance for healthy subjects of different age groups is an important first step for understanding the relationship between impairments and physical performance in disabled populations.

METHODS

Thirty-four subjects ages 20-36 and 33 subjects ages 60-76 participated. Video motion and force plate analysis were used to characterize spinal motion and center of pressure displacements during the functional reach test for younger and older subjects.

RESULTS

Spinal motion during standing reach was characterized by forward trunk flexion, lateral trunk flexion, thoracolumbar rotation, and lower body rotation. Younger and older subjects differed (P = 0.05) in the amount of forward trunk flexion and thoracolumbar rotation which occurred but not lower body rotation. Younger subjects displaced their center of pressure further forward (P = 0.0001) and through a greater percentage of their initial base of support (P = 0.0001) than older subjects.

CONCLUSION

This study provides the first multiplanar characterization of spinal motion used during standing reach. Significant differences for a number of variables existed between younger and older subjects.

Effects of ipsilateral anterior thigh soft tissue stretching on passive unilateral straight-leg raise

STUDY DESIGN

Randomized 3-group pretest-posttest with blind assessment of outcome.

OBJECTIVES

The purpose of this study was to examine the effect of sagittal plane hold-relax exercise applied to the ipsilateral anterior thigh, and prone positioning on passive unilateral straight-leg raise measurements.

BACKGROUND

Straight-leg raising has been viewed as a measurement for hamstring muscle length, but literature suggests that other structures may affect this measurement.

METHODS AND MEASURES

Sixty subjects (45 men, 15 women) qualified for inclusion into the study based on a straight-leg raise measurement of < or = 65 degrees. Subjects were randomly assigned to one of three groups: control, static stretch, or sagittal plane hold-relax exercise. Pretest and posttest straight-leg raise measurements of the right lower extremity were performed for each subject.

RESULTS

A 1-way ANOVA of the change scores showed a significant difference between groups. A Tukey post hoc analysis of the change scores showed that both treatment groups' means differed significantly from the control group and from each other, with the sagittal plane hold-relax group exhibiting the largest change (mean of 7.8 degrees +/- 2.8 degrees).

CONCLUSIONS

The results of this study show that sagittal plane hold-relax exercise and passive prone results of this study show that sagittal plane hold-relax and passive prone positioning can significantly increase straight-leg raise range of motion, however the sagittal plane hold-relax stretching of the anterior thigh is more effective than passive prone positioning.

Exercise to improve spinal flexibility and function for people with Parkinson's disease: a randomized, controlled trial

OBJECTIVES

The effectiveness of an exercise intervention for people in early and midstage Parkinson's disease (stages 2 and 3 of Hoehn and Yahr) in improving spinal flexibility and physical performance in a sample of community-dwelling older people is described.

DESIGN AND SETTING

Fifty-one men and women, aged 55-84 years, identified through advertisement, local support groups, and local neurologists were enrolled into a randomized, controlled trial. Subjects were assigned randomly to an intervention or a usual care arm (i.e., no specific exercise). Of the original 51 participants, 46 completed the randomized, controlled trial. Participants in the exercise arm (n = 23) received individual instruction three times per week for 10 weeks. Participants in the usual care arm (n = 23) were "wait listed" for intervention.

MEASUREMENTS

Changes over 10 weeks in spinal flexibility (i.e., functional axial rotation) and physical performance (i.e., functional reach, timed supine to stand) were the primary outcome measures.

RESULTS

MANOVA conducted for the three primary outcome variables demonstrated significant differences (P < or = .05) between the two groups. Further analysis using ANOVA demonstrated significant differences between groups in functional axial rotation and functional reach for the intervention compared with the control group. There was no significant difference in supine to sit time.

CONCLUSION

Study results demonstrate that improvements in axial mobility and physical performance can be achieved with a 10-week exercise program for people in the early and midstages of PD.

The role of mechanical and neural restraints to joint range of motion during passive stretch

Musculoskeletal flexibility is typically characterized by maximum range of motion (ROM) in a joint or series of joints. Resistance to passive stretch in the mid-range of motion is a function of the passive mechanical restraints to motion. However, an active contractile response may contribute resistance at terminal ROM.

PURPOSE

The purpose of this study was to examine whether maximum straight leg raise (SLR) ROM was limited by passive mechanical forces or stretch-induced contractile responses to stretch.

METHODS

An instrumented SLR stretch was applied to the right leg of 16 subjects ending at the point of discomfort. Torque was measured with a load cell attached to the ankle. An electrogoniometer was placed on the hip, and the knee was braced in extension. Surface electrodes were placed over the rectus and biceps femoris muscles. Following the instrumented SLR test, maximum ROM was measured goniometrically by a physical therapist using the standard SLR test (PT SLR ROM). Torque/ROM curves were plotted for each subject.

RESULTS

PT SLR ROM was positively related to total energy absorbed (area under the curve) (r = 0.49, P = 0.044), negatively related to the increase in torque from 20 to 50 degrees (r = -0.81, P < 0.0001) and negatively related to energy absorbed from 20 to 50 degrees (r = -0.73, P < 0.001). Minimal stretch-induced hamstring activity was elicited (3 +/- 1% MVC), and the EMG activity was unrelated to PT SLR ROM (r = -0.06, P = 0.8). A combination of the increase in torque from 20 to 50 degrees and total energy absorbed improved the relationship to PT SLR ROM (r = 0.89, P = 0.001). Seventy-nine percent of the variability in maximum SLR ROM could be explained by the passive mechanical response to stretch.

CONCLUSIONS

These data lend support to the concept that musculoskeletal flexibility can be explained in mechanical terms rather than by neural theories.

Flexibility and its effects on sports injury and performance

Flexibility measures can be static [end of ROM (range of motion)], dynamic-passive (stiffness/compliance) or dynamic-active (muscle contracted, stiffness/compliance). Dynamic measures of flexibility are less dependent on patient discomfort and are more objective. Acute and chronic changes in flexibility are likely to occur with stretching exercises, but it is difficult to distinguish between changes in stretch tolerance as opposed to changes in muscle stiffness. How flexibility is measured impacts these findings. There is no scientifically based prescription for flexibility training and no conclusive statements can be made about the relationship of flexibility to athletic injury. The literature reports opposing findings from different samples, frequently does not distinguish between strain, sprain and overuse injury, and rarely uses the proper denominator of exposure. There is basic scientific evidence to suggest that active warm-up may be protective against muscle strain injury but clinical research is equivocal on this point. Typically, specific flexibility patterns are associated with specific sports and even positions within sports. The relationship of flexibility to athletic performance is likely to be sport-dependent. Decreased flexibility has been associated with increased in-line running and walking economy. Increased stiffness may be associated with increased isometric and concentric force generation, and muscle energy storage may be best manifested by closely matching muscle stiffness to the frequency of movement in stretch-shorten type contractions.

The relationship between elbow flexor volume and angular stiffness at the elbow

OBJECTIVE: The purpose of this experiment was to determine if a correlation exists between the volume of the elbow flexors and angular stiffness at the elbow, and to determine the contribution of the biceps brachii and the brachialis muscles to angular stiffness. DESIGN: This study is a descriptive, correlational study and presents a graphical model of the passive properties of muscle. BACKGROUND: The correlation between arm volume and angular stiffness has been shown, but the measurement of arm volume was not specific to the structures being strained. Pre-positioning a bi-articular muscle by stretching over one joint decreases the range of motion at the other joint and may affect the stiffness. METHODS: Angular stiffness at the elbow of 14 female and 15 male volunteers was measured, and the volume of the elbow flexors was calculated from compounded ultrasound imaging. Initial biceps length was set by pre-positioning the shoulder in two different positions. RESULTS: A significant linear relationship was observed between the slope of phase 1 of the stiffness curve and volume of the elbow flexors in both horizontal flexion (r = 0.92) and horizontal extension (r = 0.79) of the shoulder. Phase 2 of the stiffness curve showed no linear relationship to muscle volume in either shoulder position (flexion, r = 0.22; extension r = 0.33). The slopes of phases 1 and 2 were significantly greater with the shoulder in horizontal extension than in horizontal flexion. CONCLUSION: The volume of the elbow flexor muscles is a good predictor of angular stiffness in phase 1 of the curve. A model of the additive contribution of the biceps and brachialis muscles is presented to account for the increased stiffness in the shoulder extended position. RELEVANCE: Recognition of the correlation between muscle volume and stiffness, coupled with understanding that pre-positioning a bi-articular muscle may affect muscle stiffness may aid the clinician in accurately assessing muscle stiffness in patients with connective tissue disorders, neurological dysfunction and contractures.

Determinants of musculoskeletal flexibility: viscoelastic properties, cross-sectional area, EMG and stretch tolerance

Cross-sectional area, stiffness, viscoelastic stress relaxation, stretch tolerance and EMG activity of the human hamstring muscle group were examined in endurance-trained athletes with varying flexibility. Subjects were defined as tight (n = 10) or normal (n = 8) based on a clinical toe-touch test. Cross-sectional area was computed from magnetic resonance imagining (MRI) images. Torque (Nm) offered by the hamstring muscle group, electromyographic (EMG) activity, knee joint angle and velocity were continuously monitored during two standardized stretch protocols. Protocol 1 consisted of a slow stretch at 0.087 rad/s (dynamic phase) to a pre-determined final angle followed by a 90-s static phase. In the dynamic phase final angle and stiffness was lower in tight (28.0+/-2.9 Nm/rad) than normal subjects (54.9+/-6.5 Nm/rad), P<0.01. In the static phase tight subjects had lower peak (15.4+/-1.8 Nm) and final torque (10.8+/-1.6 Nm) than normal subjects (31.6+/-4.1 Nm, 24.1+/-3.7 Nm, respectively)(P<0.01), but torque decline was similar. Protocol 2 consisted of a slow stretch to the point of pain and here tight subjects reached a lower maximal angle, torque, stiffness and energy than normal subjects (P<0.01). On the other hand, stiffness was greater in tight subjects in the common range (P<0.01). Cross-sectional area of the hamstring muscles and EMG activity during the stretch did not differ between the groups. However, lateral hamstring cross-sectional area was positively related to mid-range stiffness (P<0.05), but inversely related to final stiffness, peak torque and the toe-touch test (P<0.01). Final angle and peak torque in protocol 1 combined to improve the predictability of the toe-touch test (R2=0.77, P<0.001). These data show that the toe-touch test is largely a measure of hamstring flexibility. Further, subjects with a restricted joint range of movement on a clinical toe-touch test have stiffer hamstring muscles and a lower stretch tolerance.

Accuracy and variability of leg velocities during concentric and eccentric actions of the quadriceps femoris muscles

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.

Influence of age on concentric isokinetic torque and passive extensibility variables of the calf muscles of women

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.

Influence of hamstring length on the standing position and flexion range of motion of the pelvic angle, lumbar angle, and thoracic angle

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.

Comparison of four clinical tests for assessing hamstring muscle length

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)

Biomedical applications of hand-held force gauges: a bibliography

Hand-held force gauges have been used increasingly in recent years to measure sensory and motor performance. In an effort to identify comprehensively journal articles in which the biomedical use of hand-held force gauges is described, five bibliographic data bases were searched, reference lists of relevant articles were examined, and current journals were scanned. The multifaceted process resulted in a bibliography of 158 articles describing the use of the instruments to measure muscle performance, resistant to joint movement, and force or pressure sensitivity.

Stiffness of the hamstring muscles and its relationship to function in anterior cruciate ligament deficient individuals

The relationship between hamstring muscle stiffness and the functional ability level of 17 subjects with complete anterior cruciate ligament rupture confirmed at arthroscopy was examined. The hamstring muscles were modelled as a single degree of freedom mass spring system with a damping component. Using this model the stiffness of these muscles was examined at 30, 45, and 60% of a maximum voluntary isometric muscle action. The functional ability of the subjects, attained using the Noyes knee rating system, was then correlated to muscle stiffness measures. Positive correlations of 0.71, 0.72, and 0.62 at the three respective muscle loading levels were observed. These findings suggested that hamstring muscle stiffness may have an important role to play in the functional ability of subjects with anterior cruciate ligament deficiency. At this time there is no single effective treatment for all individuals with anterior cruciate ligament deficiency. Those individuals who undergo a conservative management programme are usually treated with hamstring muscle exercises for improving knee flexion strength. The current study provides evidence that hamstring exercises may alter other properties of muscles, such as their active stiffness, which in turn may influence the functional ability of the anterior cruciate ligament deficient individual.

Passive compliance and length of clinically short hamstring muscles of healthy men

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).