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PubMed2002

Muscle strength and tibolone: a randomised, double-blind, placebo-controlled trial.

OBJECTIVE: To investigate the effects of tibolone, a tissue-specific compound with a mixed (estrogenic, progestogenic and androgenic) hormonal profile, on skeletal muscle strength in a group of healthy postmenopausal women. DESIGN: Randomised, parallel group, double-blind, placebo-controlled, single-centre trial conducted between August 1997 and July 1999. PARTICIPANTS: Eighty-five healthy women, between one and 15 years postmenopausal, (mean [SD] age, 54.2 [4.7] years) recruited from local paper advertisements. Participants were randomly assigned to 2.5 mg tibolone or to identically appearing placebo pills daily for 12 months, taken orally in the morning. METHODS: Both maximal handgrip strength, representing upper body strength, and maximal quadriceps strength, representing lower body strength, were measured isometrically. MAIN OUTCOME MEASURES: Treatment effect estimates (between group differences) in handgrip strength and isometric knee extension at last visit. RESULTS: Tibolone significantly (P = 0.04) increased handgrip strength compared with placebo (difference 0.99 kg, [95% CI 0.1-1.9]). No significant treatment effect (P = 0.61) was observed in isometric knee extension strength. Isometric strength adjusted for body mass index resulted in a trend favouring tibolone (P = 0.06). Individual trend analysis showed a significant difference in rate of change throughout the year (6.8% [95% CI 2.1-10.7]) favouring tibolone. CONCLUSIONS: Administration of tibolone increased handgrip strength in postmenopausal women compared with placebo. A trend indicating a positive effect in isometric knee extension strength adjusted for body mass index was observed. Tibolone seems to mitigate the menopause-related decline in muscle strength.

Administration, Oral↗

PubMed2004

The effect of mechanical undercuts on the strength of composite repair.

BACKGROUND: The authors conducted an in vitro study to test the hypothesis that undercuts prepared in old composite restorations could improve the strength between the restoration and a flowable composite as repair material. METHODS: The authors used three composites to fabricate cylinders as repair substrates. The etched-only group was ground, etched, dried and built up with a flowable composite. For the undercut group, the authors introduced arrays of fissures on the surfaces before preparing the specimens for subsequent buildup in the manner described for the etched-only group. They made nonrepaired cylinders for baseline measures of strength. They sliced all finished cylinders into slender bars with a diamond saw. Flexure strength values were determined by a three-point-bending test. RESULTS: Nonrepaired bars exhibited statistically significantly higher flexure strength values than did repaired bars, as determined by Wilcoxon rank sum test. Two-way general linear model showed that both material (P < .0001) and undercut (P = .0207) exhibited a statistically significant influence on the repaired flexure strength. Repair substrate with elastic modulus close to that of repair material exhibited a greater percentage of recovery of the respective cohesive strength. Compared with the etched-only group, the undercut group yielded a higher mean flexure strength with one composite but a lower mean flexure strength with the other two. Examination of the fractured surfaces showed that a significant number of undercuts were filled only partially. CONCLUSION: Flexure strengths of repaired specimens always were lower than the cohesive flexure strengths of the materials being repaired. Undercuts did not generally improve repair strength. CLINICAL IMPLICATIONS: Small undercuts on the surface of composite often are difficult to fill completely, resulting in areas of stress concentration that result in no improvement in the repair strength.

Analysis of Variance↗

PubMed2006

The use of neuromuscular electrical stimulation to improve activation deficits in a patient with chronic quadriceps strength impairments following total knee arthroplasty.

STUDY DESIGN: Case report. BACKGROUND: Long-term deficits in quadriceps femoris muscle strength and impaired muscle activation are common among individuals with total knee arthroplasty (TKA). Failure to address strength-related impairments results in poor surgical and functional outcomes, which may accelerate the progression of osteoarthritis in other lower extremity joints. The purpose of the current case report was to implement a neuromuscular electrical stimulation (NMES) treatment protocol in conjunction with an intense weight-training program, with the aim of reversing persistent quadriceps muscle impairments after TKA. CASE DESCRIPTION: The patient was a 62-year-old male cyclist 12 months following simultaneous, bilateral TKA with impairments in left quadriceps strength and volitional muscle activation. His left quadriceps strength was 26% weaker than his right and central activation ratio (CAR) of his left quadriceps was 13% lower than his right quadriceps CAR. NMES to the left quadriceps was implemented for 6 weeks, in addition to an intense volitional weight-training program with emphasis on unilateral lower extremity exercises. OUTCOMES: The patient demonstrated a 25% improvement in left quadriceps femoris maximal volitional force output following 16 treatments of combined NMES and volitional strength training over a 6-week period. The patient's volitional muscle activation improved from a CAR of 0.83 before treatment to 0.97 after treatment. At discharge from physical therapy and at his 18-month postoperative follow-up, the patient's left quadriceps strength was only 4% lower than his right quadriceps strength. At the 24-month follow-up, the patient's left quadriceps strength was 6% stronger than his right quadriceps strength. DISCUSSION: The patient was able to achieve symmetrical quadriceps strength and complete muscle activation following 6 weeks of NMES and volitional strength training. An intense strengthening program may have the potential to reverse persistent strength-related impairments following TKA.

Arthroplasty, Replacement, Knee↗

PubMed2005

[Isometric muscle strength measurements and assessment: a pilot study].

OBJECTIVE: To determine the anthropometric parameters and the isometric muscle strength in a working population sample in China, and to investigate the relationship between muscle strength and individual attributes, such as age, gender, height and weight. METHODS: The study population consisted of 146 male and 47 female people including workers, administrators and college students. Four types of muscle strength, i.e., handgrip, arm lift, shoulder lift, and torso pull, were measured. RESULTS: Left handgrip, right handgrip, arm lift, shoulder lift and torso pull of male workers were (42.07 +/- 7.20), (43.92 +/- 7.14), (26.79 +/- 4.64), (33.79 +/- 6.88), (88.56 +/- 17.98) kg, respectively while those of female workers were (21.29 +/- 5.09), (23.26 +/- 5.47), (13.29 +/- 3.37), (18.52 +/- 4.01), (41.06 +/- 12.04) kg, respectively. The female's strength was about 50% lower than the male's. The strength in the 40 approximately years old group was higher than that in other age groups. There were significant positive correlation between the gender and the isometric strength as well as between the body weight and the isometric strength. If the body weight served as the corrected parameter, there was no significant difference in the handgrip among the groups (P < 0.05), but the torso pull of male workers > college students > administrators. All relative muscle strengths except the torso pull were similar for all age groups. CONCLUSION: The body weight as the independent variable can be used for establishing the predictive equation of the muscle strength. Calculation of the relative muscle strength can relieve the interference of the body weight for the muscle strength.

Adolescent↗

PubMed1989

Relationship of body composition, muscle strength, and aerobic capacity to bone mineral density in older men and women.

We evaluated the relationship of body composition, maximal aerobic capacity (VO2max), and muscle strength to bone mineral density in 91 healthy men and women, age 61-84 years. Lean body mass was estimated from two independent measures of fat mass, bioelectrical impedance and skinfold thickness. VO2max was determined by treadmill ergometry with direct measurement of oxygen consumption. Grip and back strength were measured by isometric dynamometry. Mineral density of lumbar spine and midradius were measured by dual- and single-photon absorptiometry. Men had significantly greater lean mass, muscle strength, aerobic capacity, and bone density than women. In women, grip strength correlated with forearm and spine density (r = 0.37, r = 0.28, p less than 0.05). In men, grip strength correlated with forearm density (r = 0.47, p less than 0.05), and back strength was significantly correlated with both spine (r = 0.46, p less than 0.01) and forearm density (r = 0.46, p less than 0.01). In women, neither forearm nor spine density correlated significantly with aerobic capacity. In men, midradius density did not correlate significantly with oxygen consumption, but the simple correlation between spine density and VO2max was significant (r = 0.41, p less than 0.05). Back strength and VO2max were significantly related in men (r = 0.47, p less than 0.01). By stepwise multiple regression, back strength emerged as the most robust predictor of spine mineral, accounting for 19% of the variation in bone density. Addition of VO2max to the regression did not add significant predictive value. However, when VO2max was expressed per kilogram lean body mass, both back strength and VO2max contributed significantly to the prediction of spine density in men, and the coefficient of determination R2 increased to 0.30. We conclude that body mass and grip strength, but not aerobic capacity, significantly predict bone density in elderly women. In elderly men, back strength is a more robust predictor of axial bone density than traditional expressions of aerobic capacity, but VO2max per kilogram lean mass and back strength both make significant contributions to the prediction of spine mineral density. The applicability of these results to younger men and women is uncertain.

Aged↗

PubMed1990

Muscle strength as a predictor of bone mineral density in young women.

It is widely accepted that physical activity is beneficial to bone. However, the specific relationships of muscle strength to bone mineral density (BMD) are poorly understood. We examined strength and BMD in 59 women aged 18-31 years who ranged in exercise patterns from sedentary to active. Mineral density of the right proximal femur (hip) and spine (L2-4) was evaluated by dual-energy x-ray absorptiometry. BMD at the midradius was measured by single-photon absorptiometry. Dynamic strength (one repetition maximum) was measured for the following muscle groups: back, elbow flexors (biceps), leg extensors (quadriceps), and the hip flexors, extensors, adductors, and abductors. Isometric grip strength was assessed by dynamometry. Mineral density at the hip correlated independently with muscle strength and body weight, but not with age. Specifically, femoral neck BMD was significantly correlated with back strength and weight, whereas trochanter and overall hip mineral density were significantly related to biceps, back, and hip adductor strength. Hip mineral density was not related to strength of the quadriceps groups or to that of the hip flexors, extensors, or abductors. In addition, muscle strength was an independent predictor of lumbar spine and midradius mineral density. In stepwise multiple regression analysis, biceps strength proved the most robust predictor of hip BMD and grip strength best predicted bone density at the lumbar spine and radius. We conclude that muscle strength is an independent predictor of bone mineral density, accounting for 15-20% of the total variance in bone density of young women.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2004

Ionic strength and the polyvalent cation receptor of shark rectal gland and artery.

The dogfish shark Squalus acanthias regulates plasma osmolality and extracellular volume by secreting a fluid from its rectal gland which has a higher NaCl and lower urea concentration than plasma. We have previously identified the presence of a calcium-sensing receptor or polyvalent cation sensing receptor (CaSR) on vascular smooth muscle of the rectal gland artery (RGA) and rectal gland tubules (RGT). Activity of the CaSR is influenced by changes in ionic strength. This led us to speculate that the ingestion of invertebrate sea animals increased plasma ionic strength, resulting in inhibition of the receptor, relaxation of RGA, and reversal of inhibition of chloride secretion by the RGT. In contrast, ingestion of fish could diminish ionic strength and have the opposite effect. To study the effect of changes in extracellular ionic strength, shark Ringers solutions were adjusted to three different ionic strengths with NaCl, but the osmolarities were kept constant by varying the concentration of urea. High ionic strength inhibited and low ionic strength enhanced the response to increasing external Ca2+ from 2.5 to 4.7 mM in RGT. The increase in cytosolic Ca2+ ([Ca2+]i) of cells in low, normal, and high ionic strength Ringers solution was 344 +/- 60, 201 +/- 26, and 114 +/- 15 nmol/L, respectively. The [Ca2+]i responses of RGA to external Ca2+ in Ringers of three different ionic strengths were 323 +/- 43, 231 +/- 14, and 56 +/- 11 nmol/L, respectively. Activation of the CaSR by spermine was reduced by more than 50% by high ionic strength in both RGT and RGA. Whether the small changes in shark plasma ionic strength that occur after a shark ingests marine animals with lower and higher ionic strength modulates salt secretion by the rectal gland is not yet known.

Animals↗

PubMed1991

Arm lift strength in work space.

This study was conducted to determine arm strength values for isometric and isokinetic efforts around the human trunk. Thirty-eight normal young adults (20 male and 18 female) performed a total of 19 tasks. These consisted of one self-selected optimum posture with upright stance and elbows bent at 90 degrees , designated as standard posture for isometric test. In addition, isometric testing was done sagittally symmetrical 30 degrees and 60 degrees lateral planes at half-, three-quarters- and full-reach distances at knuckle height. The isokinetic tests were done between knuckle height and shoulder height in postures identical to isometric tests. The sequence of these tasks was randomised. The peak strength in standard posture was invariably lower than the peak strength at half-reach in isometric condition in all three planes for both sexes with the exception of one condition among females (60 degrees lateral plane, half-reach isometric). Peak and average arm lift strengths of males were significantly higher than those of females (p < 0.01) and ranged between 44% and 71%. For both sexes isometric strength was significantly higher than isokinetic strength (p < 0.01). The peak and average strengths in the sagittal plane were invariably higher than those of asymmetric postures, with one exception among females. With increasing reach distance the strength declined significantly for all conditions among both genders (p < 0.01). The ANOVA showed that the gender, mode of lifting, postural symmetry and reach of lifting, in addition to affecting the peak and average strength individually (p < 0.01), had significant 2-way and 3-way interactions (p < 0.01). All strength values were inter-correlated (p < 0.01). The regressions predicting peak and average strengths from anthropometric characteristics and sagittal plane strengths accounted for 63% to 89% of all variance and were highly significant (p < 0.01).

Journal Article↗

PubMed2006

Bone strength and its determinants in pre- and early pubertal boys and girls.

Higher fracture rates in women than men may be related to a sex difference in bone strength that is thought to emerge during growth. However, sexual dimorphism in bone strength and the determinants of bone strength in boys and girls are not well understood. Thus, our objectives were to (1) compare tibial bone strength and its components (geometry and density) between pre- and early pubertal boys and girls and (2) identify the contribution of muscle cross-sectional area and other modulating factors to bone outcomes. We used pQCT to assess the distal tibia (8%) and tibial midshaft (50%) in 424 Asian and Caucasian pre- and early pubertal boys and girls. Our primary outcomes were bone strength index (BSI, mg2/mm(4)) at the distal tibia and strength strain index (SSI, mm3) at the midshaft. We also assessed components of bone strength including bone geometry [total (ToA) and cortical (CoA) cross-sectional areas, mm2] and total (ToD, mg/cm3) and cortical (CoD, mg/cm3) density. We used ANCOVA to compare bone outcomes between boys and girls in each maturity group (PRE or EARLY pubertal by Tanner stage) and multiple regression to evaluate the contribution of muscle cross-sectional area (MCSA, mm2 by pQCT), maturity, ethnicity, physical activity, dietary calcium, and vertical jump height to bone outcomes. After adjusting for tibial length and MCSA, bone strength indices were 6-15% (P < 0.05) greater in PRE and EARLY boys compared with PRE and EARLY girls. The sex difference in bone strength was due largely to greater bone areas (4-6%) in boys. At the distal tibia ToD was significantly greater in PRE boys (6%, P < 0.001) compared with PRE girls and at the midshaft CoD was slightly greater in both PRE and EARLY girls (1%, P = 0.01). After adjusting for tibial length, MCSA was the primary explanatory variable of tibial bone geometry and strength in both sexes accounting for 10-16% of the variance. The influence of maturity, ethnicity, physical activity, and dietary calcium on pQCT bone outcomes was small and was both site- and sex-specific. Sexual dimorphism in tibial bone strength is evident in prepuberty. Our results are consistent with a functional model of bone development in which bone adapts its geometry and strength to withstand challenges from muscle forces during growth.

Bone Density↗

PubMed2006

The impact of ionic strength and background electrolyte on pH measurements in metal ion adsorption experiments.

Our understanding of metal ion adsorption to clay minerals has progressed significantly over the past several decades, and theories have been promulgated to describe and predict the impacts of pH, ionic strength, and background solution composition on the extent of adsorption. Studies evaluating the effects of ionic strength on adsorption typically employ a broad range of background electrolyte concentrations. Measurement of pH in these systems can be inaccurate when pH values are measured with liquid junction pH probes calibrated with standard buffers due to changes in the liquid junction potential between standard, low ionic strength (0.05 M) buffers and high ionic strength solutions (>0.1 M). The objective of this research is to determine the extent of the error in pH values measured at high ionic strength, and to develop an approach for accurately measuring pH over a range of ionic strengths using a combined pH electrode. To achieve this objective, the adsorption of cobalt (10(-5) M) onto gibbsite (10 g/L) from various electrolyte solutions (0.01-1 M) was studied. The pH measurements were determined from calibrations with standard buffers and ionic strength corrected buffer calibrations. The results show a significant effect of the aqueous solution background electrolyte anion and ionic strength on pH measurement. The 0.5 and 1 M ionic strength metal ion adsorption edges shifted to lower pH with increasing ionic strength when pH was calibrated with standard buffers whereas no shift in the adsorption edges was observed when calibrated with ionic strength corrected buffers. Therefore, to obtain an accurate pH measurement, pH calibration should contain the same electrolyte and ionic strength as the samples.

Journal Article↗

PubMed2004

Predicting shoulder strength using allometry: implications for shoulder outcome assessments.

INTRODUCTION: Shoulder strength is an integral component of shoulder function. In assessing shoulder function many functional scales rely on direct or indirect measures of strength. Strength, and thus these scales, is often highly correlated with age. We propose an allometric method for assessing shoulder strength. Allometric modeling has provided accurate predictions of biologic growth and physiologic function in both human and animal studies. Allometry utilizes the relationship between the two homologous structures on the left and right sides of the body, providing in effect an internal control and thus eliminating many confounding effects, e.g. age and level of activity. METHODS: Twenty patients with unilateral shoulder dysfunction underwent strength testing of their affected and unaffected shoulder. Strength testing of the bilateral shoulders was also assessed in twenty people without shoulder pain in order to delineate the effect of hand dominance on strength in those without shoulder pain. Absolute and predicted strength deficits of the involved shoulder were calculated via regression analysis. Pearson's correlation coefficients were computed between age and strength. RESULTS: Utilizing the contralateral extremity as an internal control eliminates age as a confounding variable in predicting strength outcomes (r = 0.093). CONCLUSION: Allometric concepts, applied to shoulder strength assessment, eliminates age as a confounding variable. Strength testing of both shoulders should be considered in the development of future shoulder outcome scales in order to eliminate the strong influence of age.

Adult↗

PubMed2002

Neck muscle strength across the sagittal and coronal planes: an isometric study.

OBJECTIVE: To determine the maximal isometric strength of neck muscles across different anatomical positions in the body sagittal and coronal planes. DESIGN: A descriptive study involving maximal isometric strength measurements of the cervical musculature in extension, flexion, and left and right lateral bending. Before measurements, the new device was tested for reliability. BACKGROUND: The literature contains only a few studies on cervical musculature strength assessment. Of these, measurement methods have displayed weak reliability. No studies existed reporting neck strength at various positions in the body coronal plane. METHODS: A new device incorporating local population anthropometry was developed for neck strength assessment on an isokinetic dynamometer. The device's repeatability attributes at measuring the strength of functionally different groups of neck muscles were first evaluated. The isometric apparatus was next used to determine the maximal strength of the cervical musculature of 17 healthy volunteers at different anatomical positions across the body sagittal and coronal motion planes. RESULTS: The results showed good intratester repeatability for intraday and day-to-day studies for all measured parameters. Strength values demonstrated that extensor muscles yielded the greatest torque and that flexor muscles provided the least torque. Linear regression analyses showed strong association of isometric strength with anatomical positions in the two body planes. CONCLUSIONS: Maximal isometric strength of neck muscles in four directions was quantified. Cervical musculature strength levels vary in discernible patterns with head-neck positions and contraction directions. RELEVANCE: Knowledge of normative values of neck muscle strength is essential for designing and implementing appropriate rehabilitation programmes. Results from the present study contribute to such literature.

Adult↗

PubMed2001

Strength, balance, and the modifying effects of obesity and knee pain: results from the Observational Arthritis Study in Seniors (oasis).

OBJECTIVE: To examine the relationship between muscular strength and dynamic balance in a sample of older adults with knee pain and to determine the role that obesity and severity of knee pain play in the ability to maintain balance. DESIGN: Cross-sectional study designed to examine the association between strength and balance in a cohort of older adults with chronic knee pain. SETTING: A university health and exercise science center. PARTICIPANTS: A cohort of 480 adults age 65 and older with knee pain. MEASUREMENTS: Force platform dynamic balance measure of the center of pressure excursion during a forward and subsequent backward lean. Isokinetic strength measures of concentric and eccentric knee flexion and extension and concentric ankle plantar flexion and dorsiflexion. Body mass index (BMI) and a knee pain scale were used to measure obesity and knee pain, respectively. RESULTS: A regression model was developed to investigate the relationship between dynamic balance and muscular strength while controlling for gender, BMI, radiographic severity, knee pain, and foot length. Knee strength alone explained 18.4% of the variability in dynamic balance. The addition of knee pain, BMI, radiographic severity, gender, and foot length explained an additional 6.7%. When the knee-ankle interaction, ankle strength, and knee strength--pain interaction variables were added to the regression model, 28.9% of the variability in dynamic balance was explained. CONCLUSIONS: Strength appears to play a significant role in maintaining balance in an older, osteoarthritic population. We found that mean knee strength accounted for approximately 19% of the variability in dynamic balance. Hence, greater knee strength was associated with better dynamic balance. The best dynamic balance performances occurred in participants that had a combination of strong knees and strong ankles. However, knee osteoarthritic patients with weak knee strength could still maintain high levels of dynamic balance by having strong ankle strength. Moreover, we have shown that obesity is associated with attenuated dynamic balance performance and that poorer balance is associated with higher pain scores in the presence of weaker knees. For stronger knees, however, pain does not appear to be related to balance.

Activities of Daily Living↗

PubMed2004

Flower and fruit abortion in sweet pepper in relation to source and sink strength.

Source strength (assimilate supply) and sink strength (assimilate demand) of the plant were varied in different ways to investigate to what extent flower/fruit abortion in sweet pepper (Capsicum annuum L.) is determined by the availability of assimilates. Source strength was varied by changing the light level, plant density, and leaf pruning. Sink strength was varied by changing the temperature and the number and position of earlier formed fruits. Shading as well as heating for short periods showed that flowers/fruits were the most susceptible to abortion during the first week after anthesis. The different experiments where source strength was varied all showed that when source strength decreased, the rate of abortion increased linearly, whether source strength was decreased by shading, high plant density, or leaf pruning. That flower and fruit abortion not only depends on the source strength but also on the sink strength of competing organs is shown by varying the number or the position of earlier formed fruits. With the same source strength, the rate of abortion showed a close relationship with the growth rate of the earlier formed competing fruits, suggesting that the induction of abortion by earlier formed fruits is due to their sink strength. Most of the variation in abortion could be related to differences in vegetative growth rate, the latter being an indicator of the source-sink ratio. However, with the same vegetative growth rate, the rate of abortion was lower for the leaf pruning treatments where no competing fruits were retained than for the fruit load treatments. This indicates that although most of the variation in abortion can be related to the source and sink strength of the plant, some effects of competing fruits can only be explained by a combination of competition and dominance.

Acclimatization↗

PubMed2000

Knee strength deficits after hamstring tendon and patellar tendon anterior cruciate ligament reconstruction.

PURPOSE: The purpose of this study was to examine the strength of the knee flexors and knee extensors after two surgical techniques of ACL reconstruction and compare them to an age and activity level matched control group. METHODS: Twenty-four subjects who had undergone ACL reconstruction greater than 1 yr previously were placed into one of two groups according to autograft donor site: patellar tendon (BPB; N = 8) and hamstring (H; N = 16), and compared with an active, control group (N = 30). Knee flexor and extensor strength was evaluated using isovelocity dynamometry (5 speeds, eccentric and concentric, 5-95 degrees ROM). Strength maps were used to graphically analyze strength over a broad operational domain of the neuromuscular system. Average strength maps were determined for each autograft group and compared with controls. A difference map (control minus graft group) and confidence (t-test) maps were used to quantitatively identify strength deficits. RESULTS: The combined ACL group (N = 24) revealed a global 25.5% extensor strength deficit, with eccentric regional (angle and velocity matched) deficits up to 50% of control. Strength deficits covered over 86% of the sampled strength map area (P < 0.01). These knee extensor strength deficits are greater than previously reported. In addition, the BPB group demonstrated a concentric, low velocity, knee extensor strength deficit at 60-95 degrees that was not observed in the H group. Significant graft site dependent, regional knee flexor deficits of up to 50% of control were observed for the H group. CONCLUSIONS: Strength deficits localized to specific contraction types and ranges of motion were demonstrated between the ACL and control groups that were dependent upon autograft donor site. Postoperative rehabilitation protocols specific to these deficits should be devised.

Adult↗

PubMed2002

Normative database of isometric cervical strength in a healthy population.

OBJECTIVES: This was a descriptive study involving maximal and average isometric strength measurements of the cervical musculature. The purpose of this study was 1) to determine the test-retest reliability of a computerized dynamometer for measuring muscular strength of the neck flexor and extensor muscles in a healthy population, and 2) to afford a normative database of the maximal and averaged isometric strength of the cervical flexors and extensors in a healthy population of 94 volunteers. The literature contains only a few descriptive studies pertaining to strength levels of the cervical musculature; none of these studies used a computerized dynamometer to determine cervical isometric strength. Only a few studies include cervical flexor and extensor isometric strength, evaluating its normal ratio as well as their correlation to body mass index. METHODS: Testing was carried out using a computerized dynamometer to measure isometric cervical strength at 0 degrees (neutral), 5 degrees, and 10 degrees of flexion and extension of the neck. RESULTS: Men show approximately 30 to 40% more strength than women both for flexion and extension at all angles and age groups. Neutral positioning showed the maximum strength values for both flexion and extension. CONCLUSION: There was a significant negative correlation between age and cervical strength and a significant positive correlation between weight and strength and between height and strength. However, the flexor/extensor ratio was maintained around 0.6 in all ages.

Adult↗

PubMed2002

Reliability and validity of hip adduction strength to measure disease severity in posterior pelvic pain since pregnancy.

STUDY DESIGN: A cross-sectional analysis was performed in patients with posterior pelvic pain since pregnancy (PPPP). The strength of adduction of the hips was measured and compared with the scores of commonly used disease severity measures of lumbopelvic pain. OBJECTIVES: To assess the reliability and validity of using hip adduction strength as measure of disease severity in patients with PPPP. SUMMARY OF BACKGROUND DATA: Various tools are used to measure disease severity in PPPP; there is still a need for simple tests with high reliability and validity. METHODS: Intra- and intertester reliability of hip adduction strength measurement was assessed in two small groups of women with PPPP. Validity of hip adduction strength to measure disease severity was investigated in a group of 200 patients with PPPP by comparing the test scores with the medical history, scores on self-reported scales on disability, pain, and tiredness, pain provocation tests, and the active straight leg raise test. Responsiveness of hip adduction strength was assessed in a group of 75 patients with PPPP. Global impression of improvement, scored by the patient, was used as criterion standard. The responsiveness of the hip adduction strength was expressed as the standardized response mean and was compared with the responsiveness of the Quebec Back Pain Disability Scale. RESULTS: The intratester reliability for measuring hip adduction strength and the intraclass correlation coefficient were both 0.79. The intertester reliability for measurement of adduction strength and the intraclass correlation coefficient were also both 0.79. Hip adduction strength correlated as expected with all disease severity measures. Responsiveness of the hip adduction strength was large (standardized response mean = 0.93) and slightly less than that of the Quebec Back Pain Disability Scale (standardized response mean = 1.20). CONCLUSION: Hip adduction strength can be recommended to measure disease severity in PPPP, especially to describe groups of patients and to evaluate the course of the disease in groups as well as in individual patients. Decreased hip adduction strength appears to be caused by the inability to use the hip muscles rather than by weakness of the muscles.

Adult↗

PubMed2004

Augmentation of pedicle screw fixation strength using an injectable calcium phosphate cement as a function of injection timing and method.

STUDY DESIGN: Axial pullout tests using fresh cadaveric thoracolumbar vertebral bodies. OBJECTIVES: To evaluate the effect of a new injectable calcium phosphate cement on the axial pullout strength of both revised and augmented pedicle screws in comparison with polymethyl methacrylate and in terms of injection method. SUMMARY OF BACKGROUND DATA: Failure of pedicle screws by loosening and back out remains a significant clinical problem and is of particular concern for patients with low bone quality. Polymethyl methacrylate was shown to significantly improve the screw pullout strength. However, polymethyl methacrylate is known to have a high polymerization temperature, which may damage surrounding tissues, and a short handling time, and it lacks long-term biocompatibility. Bone mineral cements such as calcium phosphate have a longer working time, very low thermal effect, and are biodegradable as well as having good mechanical strength. Recently, new calcium phosphate cement with improved infiltration properties for better injectability has been introduced, but its performance in augmenting the pedicle screw fixation has not been tested yet. METHODS: The bone mineral densities of 52 vertebral bodies (T11-L5) were measured using dual-energy x-ray absorptiometry. In each vertebral body, a 6.5-mm-diameter and 45 +/- 5-mm-long pedicle screw was inserted into either the right or left pedicle, representing an initial intact implantation. These intact screws were pulled axially until failure at 10 mm/min. Following failure of the intact pedicle, 3.0 cc of cement was injected into the failed screw hole, representing a revision case, and the prepared screw hole in the contralateral intact pedicle representing an augmentation case. The cement was injected either to the distal tip of the screw hole (calcium phosphate-1 group, n = 19) or along the entire length of the screw hole (calcium phosphate-2 group, n = 20), and the screws were inserted. The cement was then allowed to cure for 24 hours at room temperature before both screws were pulled to failure. In 13 specimens, polymethyl methacrylate was injected along the entire length of the screw hole (polymethyl methacrylate group). Kruskal-Wallis and Mann-Whitney tests were used to compare the screw pullout strengths for study groups, whereas linear relationships between variables were assessed with scatter plots and Spearman correlation coefficients with a significance level of 0.05. RESULTS: Mean bone mineral densities of all groups were similar. A significant positive correlation was seen between bone mineral density and intact pullout strength. In revision, the pullout strength of calcium phosphate-1 was similar to that of intact, whereas the pullout strength of calcium phosphate-2 and polymethyl methacrylate was significantly greater than that of intact. In augmentation, all 3 injection methods significantly improved the pullout strength over intact. Injection of the calcium phosphate cement along the entire screw length was found to produce significantly higher pullout strengths than injection only at the distal tip of the screw in revision case. Injection of polymethyl methacrylate produced significantly higher pullout strengths than the injection of calcium phosphate by either method in both revision and augmentation. CONCLUSION: Results of this study demonstrate that the new calcium phosphate cement can improve the axial pullout strength of revised and augmented pedicle screws when injected along the entire length of the screw. This suggests that the injection method may be crucial for revision of failed pedicle screws. Considering inherent properties more favorable for in vivo application, such as nonexothermal polymerization and longer working time, and significant improvement in pullout strength, the new calcium phosphate cement may be a good alternative to polymethyl methacrylate for the augmentation of pedicle screw fixation.

Aged↗