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PubMed2006

Effects of strength training on muscle strength characteristics, functional capabilities, and balance in middle-aged and older women.

Progressive strength training can lead to substantial increases in maximal strength and mass of trained muscles, even in older women and men, but little information is available about the effects of strength training on functional capabilities and balance. Thus, the effects of 21 weeks of heavy resistance training--including lower loads performed with high movement velocities--twice a week on isometric maximal force (ISOmax) and force-time curve (force produced in 500 milliseconds, F0-500) and dynamic 1 repetition maximum (1RM) strength of the leg extensors, 10-m walking time (10WALK) and dynamic balance test (DYN.D) were investigated in 26 middle-aged (MI; 52.8 +/- 2.4 years) and 22 older women (O; 63.8 +/- 3.8 years). 1RM, ISOmax, and F0-500 increased significantly in MI by 28 +/- 10%, 20 +/- 19%, 31 +/- 34%, and in O by 27 +/- 8%, 20 +/- 16%, 18 +/- 45%, respectively. 10WALK (MI and O, p < 0.001) shortened and DYN.D improved (MI and O, p < 0.001). The present strength-training protocol led to large increases in maximal and explosive strength characteristics of leg extensors and in walking speed, as well to an improvement in the present dynamic balance test performance in both age groups. Although training-induced increase in explosive strength is an important factor for aging women, there are other factors that contribute to improvements in dynamic balance capacity. This study indicates that total body heavy resistance training, including explosive dynamic training, may be applied in rehabilitation or preventive exercise protocols in aging women to improve dynamic balance capabilities.

Exercise↗
PubMed1976

[Studies on the strength and the cutting performance of dental canal reamer. (II). Torsional strength and tip diameter of dental canal reamers (author's transl)].

Strength of pulp canal reamers are important problems for cutting treatments of the root of tooth at the dental regions. Reamers have been used as cutting tools by the twisting movements, and then, fracture of reamers are especially caused by the shearing stress at the bite tips. So, this paper treated the shear strength of dental canal reamers, which are torsional strength and twisting rigidity of these cutting instruments. And we made the torsional apparatus for cutting and twisting tests, and tested the torsional strength of raw materials and pulp canal reamers. Type of reamer's configuration are treated by Japanese industrial standard (JIS) and these properties are readjusted with dimensions of diameter of reamers. Shear strength of reamers are 120 approximately 140 kg/mm2 and strength of straight bar with taper are about two times of that of reamers which are about 40 kg/mm2 (except reamer's number 1, 2). Scattering of value of strength and torsional angle of these reamers are examined and showed the range of scattering of these properties. Effectiveness of torsional angle on the fracture properties are considered on the clinical treatments and treated the safety of fracture of these reamers.

Dental Instruments↗
PubMed1983

Comparison of granule strength and tablet tensile strength.

The granule strength (crushing load) of lactose granulated with 1-9% povidone was measured initially and at intervals during a 1-year period. The granule strengths of dibasic calcium phosphate dihydrate granulated with various concentrations of starch and povidone were measured. The axial and radial tensile strengths of tablets compressed from these granules were determined and related to concentration of binder and granule strength. The effect of compressional force on the integrity of granules in a tablet matrix is shown in scanning electron photomicrographs of the fractured tablets which had undergone a diametral compression test. It appears that the compressional force and the concentration of binder contribute more than granule strength to tablet tensile strength.

Hardness↗
PubMed1994

Absorbable self-reinforced polyglycolide (SR-PGA) screws for the fixation of fractures and osteotomies: strength and strength retention in vitro and in vivo.

The initial mechanical strength and strength retention in vitro and in vivo of novel absorbable and self-reinforced polyglycolide (SR-PGA) screws for the fixation of fractures and osteotomies were determined. The SR-PGA screws showed initial bending strength values comparable with those of yield strength of standard stainless steel. The SR-PGA screws lost all their bending and shear strengths in 6 weeks in vivo. The strength retention properties of SR-PGA screws are sufficient for safe fixation of relatively rapidly consolidating fractures and osteotomies of cancellous bone that are not exposed to hard mechanical stresses.

Animals↗
PubMed2004

Decreased isometric neck strength in women with chronic neck pain and the repeatability of neck strength measurements.

OBJECTIVES: To evaluate neck flexion, extension, and, especially, rotation strength in women with chronic neck pain compared with healthy controls and to evaluate the repeatability of peak isometric neck strength measurements in patients with neck pain. DESIGN: Cross-sectional. SETTINGS: Rehabilitation center and physical and rehabilitation medicine department at a Finnish hospital. PARTICIPANTS: Twenty-one women with chronic neck pain and healthy controls matched for sex, age, anthropometric measures, and occupation. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak isometric strength of the cervical muscles was tested in rotation, flexion, and extension. RESULTS: Significantly lower flexion (29%), extension (29%), and rotation forces (23%) were produced by the chronic neck pain group compared with controls. When the repeated test results were compared pairwise against their mean, considerable variation was observed in the measures on the individual level. Intratester repeatability of the neck muscle strength measurements was good in all the 4 directions tested in the chronic neck pain group (intraclass correlation coefficient range,.74-.94). The coefficient of repeatability was 15N, both in flexion and extension, and 1.8 Nm in rotation. On the group level, improvement up to 10% due to repeated testing was observed. CONCLUSIONS: The group with neck pain had lower neck muscle strength in all the directions tested than the control group. This factor should be considered when planning rehabilitation programs. Strength tests may be useful in monitoring training progress in clinical settings, but training programs should be planned so that the improvement in results is well above biologic variation, measurement error, and learning effect because of repeated testing.

Adult↗
PubMed2001

In vitro bond strengths of resin modified glass ionomer cements and composite resin self-cure adhesives: introduction of an adhesive system with increased bond strength and inhibition of decalcification.

This study evaluated the shear bond strength and adhesive remnant index of 5 self-cure adhesives to comparatively evaluate a new adhesive system. Extracted human incisors were randomly divided into 7 test groups of 20 each. Incisor mesh-backed brackets were bonded to the tooth specimens in each group with their respective adhesive according to the manufacturer's instructions. The specimens were thermocycled for 2 weeks at temperatures from 5 degrees to 55 degrees C to simulate oral conditions and debonded using an Instron machine. Acceptable bond strength parameters were present with the Contacto No-Mix (composite resin containing glass ionomer 8.75 MPa) and Fuji Ortho SC with acid conditioning (6.98 MPa). Contacto No-Mix had a higher bond strength (11.2 MPa) when microetching and Megabond were employed than when these adjuncts were not employed. When FUJI Ortho SC specimens were conditioned with polyacrylic acid, they showed a higher bond strength (6.98 MPa) than when bonded to unetched teeth (5.41 MPa). In test 3, EXPT-fluoride adhesive (AF) demonstrated a higher bond strength (13.44 MPa) than both resin composite Contacto No-Mix (8.8 MPa, GAC 7.4 MPa) and FUJI Ortho SC (5.41 MPa). Expt AF (Test 3) and Concise had equal bond strengths, however, the former can potentially release fluoride from the glass ionomer. Although the Ex

Adhesiveness↗
PubMed2007

Effects of muscle strength training and megestrol acetate on strength, muscle mass, and function in frail older people.

OBJECTIVES: To determine the independent and combined effects of progressive resistance muscle strength training (PRMST) and megestrol acetate (MA) on strength, muscle mass, and function in older recuperative care patients. DESIGN: Double-blind, randomized, controlled intervention using a two-by-two factorial design and conducted between 1999 and 2001. SETTING: University-affiliated Department of Veterans Affairs hospital. PARTICIPANTS: Twenty-nine patients (mean age 79.4 +/- 7.4, 90% white) aged 65 and older and had recent functional decline. INTERVENTIONS: After randomization to one of four treatment groups (low-resistance exercises plus 800 mg per day of MA or a placebo or high-intensity PRMST plus 800 mg/d of MA or placebo), subjects received training and the drug or placebo for 12 weeks. MEASUREMENTS: Change in muscle strength, mid-thigh muscle area, and aggregate functional performance score as assessed using analysis of covariance. RESULTS: Five subjects withdrew from the study before its completion. Based on intent-to-treat analyses, subjects who received high-intensity PRMST and placebo experienced the greatest strength gains. The addition of MA was associated with worse outcomes than with high-intensity exercise training alone, especially with regard to the leg exercises. Post hoc analysis demonstrated that subjects who received high-intensity PRMST and placebo experienced significantly greater percentage increases in leg strength than subjects in either of the MA treatment groups (P<.05 for each comparison). There was also a significant negative effect of MA on physical function. In general, subjects who received MA experienced a deterioration in aggregate physical function scores, whereas the remaining subjects improved (-0.80+/-0.40 vs 0.48+/-0.41, P=.04). There was not a significant interaction between exercise and MA for any outcome. CONCLUSION: High-intensity PRMST is a safe and well-tolerated exercise regimen for frail elderly patients. The addition of MA appears to blunt the beneficial effects of PRMST, resulting in less muscle strength and functional performance gains.

Aged↗
PubMed2006

Reproducibility and relationship of single-joint strength vs multi-joint strength and power in aging individuals.

INTRODUCTION: Reliable and sensitive muscle strength/power assessments are essential when evaluating age-related and/or training-induced changes in maximal strength and power. AIM: To investigate the reproducibility and inter-relationship of single-joint isokinetic/isometric leg muscle strength vs multi-joint mechanical muscle function during counter-movement jump (CMJ) in moderately trained aging individuals (age 72.3+/-6.6). RESULTS: The within-subject coefficient of variation (CV(w-s)) for the single-joint test showed good reproducibility (<10%) for quadriceps and hamstring strength (except for hamstring isometric). Plantar flexion demonstrated good to moderate reproducibility (CV(w-s) range: 10.4-17.2%). Excellent to good CV(w-s) (<10%) was observed for all concentric CMJ parameters, except for plantar flexor mean work (CV(w-s)=13%). Eccentric CMJ parameters demonstrated good to moderate reproducibility (CV(w-s) range: 8.1-18.2%). Isokinetic and isometric quadriceps, hamstring and plantar flexor single-joint strength measurements were found to correlate with several CMJ parameters. CONCLUSION: Single-joint and multi-joint strength and power assessment tests of the lower limbs appear to be reproducible in aging individuals. Furthermore, associations between single-joint strength and multi-joint CMJ power and force variables exist. To evaluate functional capacity in elderly people further investigations must be carried out to identify specific power/strength parameters that are most tightly linked to functional performance.

Aging↗
PubMed1994

Isokinetic testing of ankle strength in older adults: assessment of inter-rater reliability and stability of strength over six months.

The study purposes were (1) to estimate the inter-rater reliability of isokinetic strength tests at the ankle in older adults (test-retest interval of three to 7 days), and to determine whether more experienced examiners were more reliable; and (2) to estimate 6 month stability of strength tests. Inter-rater reliability was high for plantar flexion and dorsiflexion tests where average strength was more than about 10 Newton-meters (Nm) (Pearson R = 0.87-0.95). When average strength was less than 10Nm, reliability was less (R = 0.42-0.75). Experienced examiners (physical therapists) and less experienced examiners (research assistants) were equally reliable. Variability in strength over 6 months was no greater than variability over a few days. We conclude that isokinetic tests of ankle strength in older adults are highly reliable and stable when examiners are adequately trained and subjects maintain usual physical activity levels.

Aged↗
PubMed2006

Moral competence and character strengths among adolescents: the development and validation of the Values in Action Inventory of Strengths for Youth.

Moral competence among adolescents can be approached in terms of good character. Character is a multidimensional construct comprised of a family of positive traits manifest in an individual's thoughts, emotions and behaviours. The Values in Action Inventory for Youth (VIA-Youth) is a self-report questionnaire suitable for adolescents that measures 24 widely valued strength of character. Data from several samples bearing on the internal consistency, stability, and validity of the VIA-Youth are described, along with what is known about the prevalence and demographic correlates of the character strengths it measures. Exploratory factor analysis revealed an interpretable four-factor structure of the VIA-Youth subscales: temperance strengths (e.g., prudence, self-regulation), intellectual strengths (e.g., love of learning, curiosity), theological strengths (e.g., hope, religiousness, love), and other-directed (interpersonal) strengths (e.g., kindness, modesty). The uses of the VIA-Youth in research and practise are discussed along with directions for future research.

Adolescent↗
PubMed2006

Using support vector machines to optimally classify rotator cuff strength data and quantify post-operative strength in rotator cuff tear patients.

Shoulder strength data are important for post-operative assessment of shoulder function and have been used in diagnosis of rotator cuff pathology. Support vector machines (SVM) employ complex analysis techniques to solve classification and regression problems. A SVM, a machine learning technique, can be used for analysis and classification of shoulder strength data. The goals of this study were to determine the diagnostic competency of SVM based on shoulder strength data and to apply SVM analysis in efforts to derive a single representative shoulder strength score. Data were taken from fourteen isometric shoulder strength measurements of each shoulder (involved and uninvolved) in 45 rotator cuff tear patients. SVM diagnostic proficiency was found to be comparable to reported ultrasound values. Improvement of shoulder function was accurately represented by a single score in pairwise comparison of the pre-operative and the 12 month post-operative group (P < 0.004). Thus, the SVM-based score may be a promising metric for summarizing rotator cuff strength data.

Artificial Intelligence↗
PubMed1995

The low ionic strength crystal structure of horse cytochrome c at 2.1 A resolution and comparison with its high ionic strength counterpart.

BACKGROUND: Cytochrome c is an integral part of the mitochondrial respiratory chain. It is confined to the intermembrane space of mitochondria, and has the function of transferring electrons between its redox partners. Solution studies of cytochrome c indicate that the conformation of the molecule is sensitive to the ionic strength of the medium. RESULTS: The crystal structures of cytochromes c from several species have been solved at extremely high ionic strengths of near-saturated solutions of ammonium sulfate. Here we present the first crystal structure of ferricytochrome c at low ionic strength refined at 2.1 A resolution. In general, the structure has the same features as those determined earlier. However, there are some differences in both backbone and side-chain conformations in several areas. These areas coincide with those observed by NMR and resonance Raman spectroscopy to be sensitive to ionic strength. CONCLUSIONS: Neither ionic strength nor crystal-packing interactions have much influence on the conformation of horse cytochrome c. Nevertheless, some differences in the side-chain conformations at high and low ionic strengths may be important for understanding how the protein functions. Close examination of the gamma-turn (residues 27-29) conserved in cytochromes c leads us to propose the 'negative classical' gamma-turn to describe this unusual feature.

Amino Acid Sequence↗
PubMed1996

Effects of strength and endurance training on isometric muscle strength and walking speed in elderly women.

The separate effects of 18 weeks of intensive strength and endurance training on isometric knee extension (KE) and flexion (KF) strength and walking speed were studied in 76- to 78- year-old women. Maximal voluntary isometric force for both KE and KF was measured in a sitting position on a custom-made dynamometer chair at a knee angle of 60 degrees from full extension. Maximal walking speed was measured over a distance of 10 m. The endurance-trained women increased KE torque and KE torque/body mass after the first 9 weeks of training when compared with the controls. when comparing the baseline, 9 week and 18 week measurements within the groups separately, both the endurance- and strength-training groups increased KE torque, KE torque/body mass and walking speed. Individual changes in KE torque/body mass before and after 18 weeks of training averaged 19.1% in the strength group, 30.9% in the endurance group and 2.0% in the controls. This study indicates that in elderly women the effects of physical training on muscle strength and walking speed occur after endurance as well as strength training. The considerable interindividual variation in change of muscle performance is also worth noticing.

Aged↗
PubMed2002

An investigation into the transverse and impact strength of "high strength" denture base acrylic resins.

A range of materials, often marketed as high strength resins is available. These materials are often expensive options to conventional heat-cured acrylic resin. The aim of this study was to investigate transverse and impact strength of five "high strength" acrylic resin denture base materials. A conventional heat-cured acrylic resin was used as a control. Specimens were prepared as specified in the International Standard Organization (ISO 1567: 1988) and British standards for the Testing of Denture Base Resins (BS 2487: 1989) and the British Standard Specification for Orthodontic resins (BS 6747: 1987) for transverse bend and impact testing. The impact strength was measured using a Zwick pendulum impact tester and the transverse bend strength measured using a Lloyds Instruments testing machine. The results showed that Metrocryl Hi, Luctitone 199 and N.D.S. Hi all had an impact strength which was significantly higher than the control. For the modulus of rupture, there was a significant difference between Sledgehammer and the other groups. There was no significant difference between the other groups and the control. For the modulus of elasticity, Sledgehammer produced the highest value followed by the control. The remaining four materials had a modulus of elasticity less than the control.

Acrylic Resins↗
PubMed1995

The influence of aging on muscle strength and muscle fiber characteristics with special reference to eccentric strength.

It is well established that aging seriously reduces isometric and concentric muscle strength due to atrophy, deterioration of mechanical properties, and motor unit loss. However, there is limited information on the impact of aging on eccentric strength despite the fact that such forces play an equally important role during daily activities. The purpose of this study was to examine the influence of aging on three expressions of muscle strength (isometric, concentric, and eccentric) in relation to muscle fiber characteristics, with special emphasis on eccentric force. Sedentary but healthy men (age range 18-80 years, n = 60) and women (20-74 years, n = 30) were tested for maximal effort isometric, concentric, and eccentric (1.05, 2.09, 3.14 rads.s-1) quadriceps strength, body composition, and muscle fiber characteristics of the vastus lateralis (men only). There was a significant (p < .05) approximately 30 N per decade decline in isometric and concentric forces, but only 9 N per decade reduction in eccentric strength. There was a significant reduction in Type II muscle fiber area with aging (p < .05). Isometric, eccentric, and concentric force correlated r = .33, r = .32 (p < .05), and r = .12 (p > .05) with Type II muscle fiber area, respectively. The correlation between age and fat-free mass/force ratio ranged from r = .39 to .43 in men and r = .27 to .50 in women. The data suggest a relative preservation of eccentric strength with aging in men and women that seems to be independent of muscle mass or muscle fiber type or size.

Adolescent↗
PubMed1987

Normal trunk muscle strength and endurance in women and the effect of exercises and electrical stimulation. Part 2: Comparative analysis of electrical stimulation and exercises to increase trunk muscle strength and endurance.

Several studies have shown positive correlations between muscle strength, flexibility, and the frequency of low-back pain. Weak trunk musculature and decreased endurance have thereby come to be identified as significant risk factors in the development of occupational back problems. Because it is widely accepted that exercise plays an important role in the conservative treatment and prevention of low-back pain, the goals of most rehabilitative programs involves improving the strength and endurance of the low-back pain patient. Whereas electrical stimulation has been shown to increase the muscle strength of the lower extremities, this effect has not been demonstrated for the trunk muscles. Part 2 is a prospective controlled study designed to document and to compare objectively the effects of electrical stimulation and exercise on trunk muscle strength. A total of 117 healthy women were divided randomly into four groups. Two groups received electrical stimulation with different electrical parameters, one group received exercises, and one group acted as a control group. The results showed that low-frequency electrical stimulation and exercises significantly (P less than .05) increased isokinetic back-muscle strength compared to the control and medium-high-frequency electrical stimulation groups. Both types of electrical stimulation, however, significantly increased (P less than .05) the endurance in the back muscles compared with the control and the exercise groups. This study showed that electrical stimulation may be a valuable treatment in the early care of low-back pain patients in maintaining and increasing strength and endurance of back muscles when a more active exercise program is too painful to perform.

Adolescent↗
PubMed1996

Trunk extensor and flexor strength measured by the Cybex 6000 dynamometer. Assessment of short-term and long-term reproducibility of several strength variables.

STUDY DESIGN: Isokinetic trunk extensor and flexor strength (peak torque, total work, power acceleration time, and torque acceleration energy) at 30 degrees/sec, 120 degrees/sec, and 180 degrees/sec and isometric extensor and flexor peak torque were measured in 24 healthy women. Measurements were performed in three separate sessions at the same time of day and by the same experienced examiner. The number of days between Session 1 and Session 2 and between Session 1 and Session 3 ranged from 1 to 7 (median, 2 days) and from 23 to 48 (median, 32 days), respectively. The test results were not revealed before all sessions were completed. OBJECTIVES: To determine the intrasession, short-term, and long-term reproducibility of several trunk strength variables measured by the Cybex 6000 isokinetic dynamometer (Lumex, Inc., Ronkonkoma, NY). SUMMARY OF BACKGROUND DATA: Only few and insufficient data regarding the reproducibility of trunk strength measurements exist. Previous studies have focused on coefficients of correlation to express reproducibility. Correlations, however, are misleading and inappropriate for this purpose. The critical difference is the difference between two results that would be statistically significant when applied to a reference group in steady state. The critical difference in percentage is calculated as 2.77 X coefficient of variation (%). METHODS: Isokinetic dynamometry (Cybex 6000). Reproducibility was expressed as pooled coefficients of variation, individual coefficients of variation, and critical differences. RESULTS: Substantial between-subject variation of coefficients of variation was found for all strength variables; for example, the 80% central range for individual coefficients of variation for long-term reproducibility of extensor strength measurements at 30 degrees/sec ranged from 2.5% to 19.5%. Critical differences calculated using the pooled variances for long-term reproducibility were higher than 20% for all measures, mounting to 80% for acceleration time. CONCLUSIONS: Strength testing is of limited value in the individual subject because of considerable day-to-day variability. This finding has important clinical implications.

Adolescent↗