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PubMed2004

The isolated and combined effects of menstrual cycle phase and time-of-day on muscle strength of eumenorrheic females.

Diurnal variation in muscle performance has been well documented in the past few years, but almost exclusively in the male population. The possible effects of the menstrual cycle on human circadian rhythms have remained equivocal, particularly in the context of muscle strength. The purpose of the study was to analyze the isolated and combined effects of circamensal variation and diurnal changes on muscle strength. Eight eumenorrheic females (age 30 +/- 5 yrs, height 1.63 +/- 0.06m and body mass 66.26 +/- 4.6kg: mean +/- SD) participated in this investigation. Isokinetic peak torque of knee extensors and flexors of the dominant leg were measured at 1.05, 3.14rad.s(-1) (through 90 degrees ROM) at two times-of-day (06:00, 18:00 h) and five time points of the menstrual cycle (menses, mid-follicular, ovulation, mid-luteal, late luteal). In addition, maximum voluntary isometric contraction of knee extensors and flexors and electrically stimulated isometric contraction of the knee extensors were measured at 60 degrees of knee flexion. Rectal temperature was measured during 30min before the tests. There was a significant time-of-day effect on peak torque values for isometric contraction of knee extensors under electrical stimulation (P< 0.05). At 18:00 h, muscle force was 2.6% greater than at 06:00 h. The time-of-day effect was not significant when the tests were performed voluntarily without stimulation: effect size calculations indicated small differences between morning and evening for maximal voluntary isometric contraction and peak torque (at 1.05rad.s(-1) for the knee extensors. A circamensal variation was observed for peak torque of knee flexors at 1.05rad.s(-1), extensors at 3.14rad.s(-1), and also isometric contraction of knee flexors, values being greatest at the ovulation phase. Interaction effects between time-of-day and menstrual cycle phase were not observed in any of the indices of muscle strength studied. The phase of the menstrual cycle seemed to have a greater effect than did the time-of-day on female muscle strength in this group of subjects. The present results suggest that peripheral rather than central mechanisms (e.g., motivation) are implicated in the diurnal variation of maximal isometric strength of women.

Adult↗

PubMed2006

Functional and isokinetic assessment of muscle strength in patients with idiopathic inflammatory myopathies.

OBJECTIVE: To assess muscle strength in patients with idiopathic inflammatory myopathies (IIM) using neuromuscular scales and isokinetic testing. METHODS: Muscle function was evaluated in 27 IIM patients being followed at the Rheumatology Unit of the University of Pisa using: (i) a modified version of the grading system used to assess Duchenne dystrophy, (ii) the four-stage grading system of Henriksson and Sandstedt, (iii) an isokinetic muscle strength test (Kin Com, Chatanooga) and (iv) the Health Assessment Questionnaire (HAQ). RESULTS: The neuromuscular scales showed normal or only mildly impaired muscle strength in 60% (Duchenne scale) and 80% (Henriksson and Sandstedt scale) of the patients, respectively, whereas isokinetic testing detected moderate to severe reductions in muscle strength in almost 70% of the patients. No correlations were observed between muscle strength and disease activity, therapy, age at evaluation and disease duration. There was a correlation between the results of the HAQ and neuromuscular testing, but not the isokinetic test. CONCLUSIONS: Although less easy and more expensive to administer, isokinetic testing appears to be a more sensitive instrument than the standard neuromuscular tests for assessing muscle function in IIM patients. In particular, it can detect small reductions in muscle strength.

Adrenal Cortex Hormones↗

PubMed2006

Patterns and correlates of muscle strength loss in older women.

BACKGROUND: The aging process is associated with progressive declines in muscle strength, resulting in functional disability and reduced quality of life. OBJECTIVE: The purpose of this epidemiological study was to examine the age-related loss of grip strength both cross-sectionally and longitudinally and the risk factors associated with the decline in muscle strength in a large population of community-living older women (aged 65-91 years). METHODS: Clinical visits, including physical examinations and lifestyle assessment, were conducted at baseline and biennially afterwards for a total of 10 years of follow-up. The upper-body muscle strength was measured by grip strength using a hand-held dynamometer. RESULTS: The muscle strength decreased cross-sectionally (n = 9,372) as well as longitudinally (n = 5,214), as age increased, and the decline in muscle strength measured during follow-up was greater than that measured cross-sectionally at baseline. The average loss of grip strength during 10 years of follow-up was 5.1 kg, equivalent to a rate of 2.4% decline per year, with the greatest loss seen in the oldest age group (80 years or older). Cross-sectional analysis revealed that the correlates of lower muscle strength included older age, greater weight, greater height loss since age 25 years, lower protein intake, difficulties in functional tasks, and lower physical activity. In longitudinal analysis, older age, baseline strength, weight and height loss during follow-up, difficulties in functional tasks, and lower physical activity were found to be significantly and independently associated with greater loss in grip strength during follow-up. CONCLUSIONS: Cross-sectional and longitudinal analyses of age-related loss of muscle strength yielded different rates of decline. In addition to older age and difficulties in functional tasks, a number of modifiable factors, including weight and physical activity, are associated with increased decline in muscle strength among older women.

Age Factors↗

PubMedDate not supplied

Changes in pelvic muscle strength and stress urinary incontinence associated with childbirth.

Pelvic muscle strength and stress urinary incontinence were studied in 20 nulliparous women at 32 to 36 antepartum weeks and 6 postpartum weeks. Measures used included a digital muscle strength score, observed incontinence, and urine flow interruption. Pelvic muscle strength declined from the antepartum to postpartum periods in women with vaginal births; however, women with greater antepartal pelvic muscle strength tended to preserve a higher level of strength during the postpartum period. In general, less pelvic muscle strength was found in women who demonstrated stress urinary incontinence.

Adult↗

PubMed2006

Decreased muscle strength and quality in older adults with type 2 diabetes: the health, aging, and body composition study.

Adequate skeletal muscle strength is essential for physical functioning and low muscle strength is a predictor of physical limitations. Older adults with diabetes have a two- to threefold increased risk of physical disability. However, muscle strength has never been investigated with regard to diabetes in a population-based study. We evaluated grip and knee extensor strength and muscle mass in 485 older adults with diabetes and 2,133 without diabetes in the Health, Aging, and Body Composition study. Older adults with diabetes had greater arm and leg muscle mass than those without diabetes because they were bigger in body size. Despite this, muscle strength was lower in men with diabetes and not higher in women with diabetes than corresponding counterparts. Muscle quality, defined as muscle strength per unit regional muscle mass, was significantly lower in men and women with diabetes than those without diabetes in both upper and lower extremities. Furthermore, longer duration of diabetes (>or=6 years) and poor glycemic control (HbA(1c) >8.0%) were associated with even poorer muscle quality. In conclusion, diabetes is associated with lower skeletal muscle strength and quality. These characteristics may contribute to the development of physical disability in older adults with diabetes.

Aged↗

PubMed1999

Predictors of isokinetic back muscle strength in patients with low back pain.

STUDY DESIGN: Testing for trunk muscle strength was performed on 105 patients with chronic low back pain. OBJECTIVES: To investigate prediction of isokinetic back muscle strength in patients with low back pain. SUMMARY OF BACKGROUND DATA: The clinical evaluation of patients with chronic low back pain often in difficult because of discrepancy between disability and impairment. The isokinetic trunk device was developed as a tool for objective assessment of back muscle strength. However, the performance of patients depends on radiologic abnormalities of the spine, conditions of the back muscles, and various psychosocial factors. Studies are warranted that address how these variables influence back muscle strength. METHODS: The patients with chronic low back pain were tested by an isokinetic trunk muscle strength test (Cybex TEF, Ronkonkoma, NY). In addition, the following variables were recorded: gender, age, body mass index, emotional distress, pain on exertion, self-efficacy for pain, degenerative changes of the lumbar spine, cross-sectional area, and density of the erector spinae muscles. The three latter variables were estimated by computed tomography scans. The sum of the total work performed during isokinetic extension strength test was the dependent variable in a multiple regression analysis, and anthropometric, demographic, psychological, and radiologic factors were independent variables. RESULTS: Gender, cross-sectional muscle area, and pain on exertion were the most powerful predictors of isokinetic back muscle strength. The final regression model, which included these variables, could account for approximately 40% of the variability in back muscle strength. CONCLUSION: For assessing the results of an isokinetic trunk muscle strength test, cross-sectional muscle area, gender, and pain on exertion should be taken into account.

Adult↗

PubMed1999

Muscle strength characteristics and central bone mineral density in women with recent onset rheumatoid arthritis compared with healthy controls.

Muscle strength and bone mineral density (BMD) at the lumbar spine (BMDspine) and femoral neck (BMDfem) were determined in 20 healthy women and in 20 women with recent onset rheumatoid arthritis (RA). The mean duration of articular symptoms of the patients was eleven months and none of them had used glucocorticoids or disease modifying antirheumatic drugs. BMDs were measured by dual x-ray absorptiometry (DXA). Knee extension, trunk extension, and flexion as well as grip strength were measured with David 200 and Digitest dynamometers. BMDspine (1.17 g/cm2 and 1.20 g/cm2) and BMDfem (0.98 g/cm2 and 0.96 g/cm2) between the women with early RA and healthy women did not differ. However, knee extension strength was 46%, grip strength 31%, trunk extension strength 14% and overall muscle strength index 29% lower in RA women (p < 0.020-0.001) than in healthy subjects. Femoral neck BMD correlated statistically significantly with knee extension strength and muscle strength index in both groups and with trunk extension and flexion strength as well as rapid force development in RA women. The data indicates that the loss of muscle strength is clearly visible during the first months of disease but the significant bone loss at central bone regions develops later.

Adult↗

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↗

PubMedDate not supplied

Patterns and determinants of muscle strength change with aging in older men.

Decreased muscle strength with aging is associated with functional disability in older adults. However, few studies have longitudinally evaluated the rate of muscle strength loss and the risk factors for the loss in older men. This study examined the patterns and determinants of muscle strength change with aging in a healthy older male population. The study participants were 321 men (age range 51-84 yrs) recruited from population-based listings in the Pittsburgh region, USA. Grip strength was measured at baseline and after an average of 7-years of follow-up. The amount of longitudinal rate of grip strength loss was 2.8% per year (a total of 20% decline during 7-year follow-up). Although all age groups experienced a decline in strength during follow-up, the rate of loss accelerated with age. After adjusting for baseline measurement, grip strength loss ranged from 2.0% decline per year for men aged < 60 years to 3.4% decline per year for men aged 70 years or older (p < .0001). Multivariate analyses revealed that besides older age, other risk factors also contributed to the loss of muscle strength in older men, including back pain, use of calcium channel blockers, caffeine intake, and height and weight loss.

Age Factors↗

PubMed1998

Measurement of quadriceps muscle strength and bulk in juvenile chronic arthritis. A prospective, longitudinal, 2 year survey.

OBJECTIVE: In a prospective survey over a 2-year period we studied strength and bulk of the quadriceps muscle in the thighs of children with juvenile chronic arthritis (JCA). METHODS: Every third month for 2 years we measured isometric muscle strength in knee extensors with a hand-held dynamometer in 20 children with JCA. Ultrasound equipment was used to measure thigh muscle bulk. A joint evaluation was made using a standard severity score. The children had their ordinary medical treatment and physiotherapy during the observation period. RESULTS: Children with high severity scores in the knee or hip had least strength and muscle bulk. In the 4 children with the highest severity scores muscle strength was reduced to half of that expected. In 10 of the children there were clear variations in severity scores during the study period, for either better or worse. In these children an increase in the severity score correlated significantly with reduction in muscle strength and bulk (p < 0.05). The muscle strength and bulk changed in parallel in these children. Other factors, although not independent, such as polyarticular JCA, long duration of disease, and steroid treatment, also reduced muscle strength. CONCLUSION: The presence and intensity of local arthritis is one important factor affecting muscle function in JCA. Normal muscle strength and bulk is rapidly lost near an inflamed joint. It is difficult to maintain or achieve normal muscle function in the presence of active arthritis despite medical and physical treatment. We assume that the muscle weakness is in part caused by atrophy of the muscle, which is influenced by local arthritis.

Adolescent↗

PubMed1994

Muscle strength from adolescence to adulthood--relationship to muscle fibre types.

The aim of the present study was to reinvestigate muscle strength and the relationship to muscle fibre and the level of physical activity in adult men and women previously studied during adolescence. A group of 55 men and 26 women were tested for maximal strength (handgrip, Sargent jump and two-hand lift) and completed a questionnaire concerning physical activity during their leisure time (activity index) at the ages of 16 and 27 years. Biopsy specimens were taken from the vastus lateralis and analysed for fibre type (percentage of I, IIA, IIB) and fibre area (area I, area IIA, area IIB). The sex differences in strength increased from age 16 to 17 years. Body dimension, sex, percentage of type II, mean fibre area and the activity index contributed to explaining 50-75% of the strength at both ages. Different changes in relationship between fibre type composition and strength in women and men was seen with increasing age. In the women, the relationship between strength and the percentage of type II fibres changed with age (from 16 to 27 years of age) from a positive correlation (only Sargent jump) to negative correlations for all the strength tests, i.e. the more type I fibres the stronger the subject. A positive correlation between strength and the level of physical activity during leisure time was revealed in the women at both ages. The positive correlation between strength and type II fibres in the 16-year-old men had disappeared at age 27. No systematic relationships between strength and the level of physical activity were seen in the men at either 16 or 27 years of age. It is suggested that women may be more dependent on physical activity than adult men to develop strength and the percentage of type I fibres reflects the degree of physical activity among adult women but not among adolescent women.

Adolescent↗

PubMedDate not supplied

Muscle strength and ageing: methodological aspects of isokinetic dynamometry and androgen administration.

1. To evaluate interventions aiming to increase muscle strength in older men, it is necessary to use an objective and reproducible method to measure strength. The most reliable method to evaluate muscle strength is isokinetic peak torque (PT) measured by a dynamometer; however, raw PT varies with differences in body size and an optimal scaling for body physique to control confounding effects of body size is necessary to make the most valid comparisons. 2. The present study was designed to estimate the effects of age (part A) and androgen administration (part B) on muscle strength and to estimate reproducibility and evaluate various scaling methods in order to optimize comparisons of isokinetic PT measurements. 3. A single isokinetic exercise protocol was used to compare the muscle strength of 31 healthy men of two age groups (< 40 and > 60 years; part A) and change in strength due to administration of dihydrotestosterone (DHT; 70 mg/day) or placebo gel for 3 months in 35 healthy older (> or = 60 years) men (part B). 4. Muscle strength was assessed by a total of 16 PT measurements using a Cybex NORM dynamometer (Cybex, Ronkonkoma, NY, USA). Age-related differences in muscle strength were estimated by using PT evaluated as raw data or scaled by normalizing methods, including simple ratio (PT/weight), allometric PT (PT/weight(0.67)) and adjustment of PT by weight, height, body mass index and body surface area (BSA). The goodness-of-fit for various scaling methods was compared using the Akaike Information Criterion (AIC) as an objective measure of model-based entropy reduction. 5. The effects of DHT administration according to different scaling methods were estimated by eta-squared measure of effect size in treatment models. In part A, older men were weaker than younger men in five knee PT, consistently by all eight analysis models but not in shoulder PT. In part B, DHT treatment resulted in an increase one knee PT (dominant knee flexion at 120 degrees/s) with the difference consistent in all seven models. 6. The scaling model using BSA proved superior to other comparison models throughout both parts of the present study according to entropy minimization criteria (AIC) for goodness-of-fit of the model or eta-squares for treatment effect size. 7. We conclude that differences in muscle strength due to age or androgen administration in older men are restricted to a minority of lower limb contractions and that use of BSA scaling for PT values is considered the best scaling method for muscle strength comparisons in either cross-sectional or longitudinal studies.

Adult↗

PubMed2006

Muscle strength improves after abductor-sparing periacetabular osteotomy.

UNLABELLED: We measured muscle strength after curved periacetabular osteotomy, one form of abductor-sparing periacetabular osteotomy, and then investigated the factors influencing postoperative muscle strength recovery. Curved periacetabular osteotomy was performed for acetabular dysplasia on 24 hips in 22 patients. All patients were females, with a mean age of 34.4 years. We based the severity of hip disease on the Tönnis classification. Isokinetic muscle strengths of the hips were measured preoperatively and 6 months and 12 months postoperatively. At 12 months postoperatively, the mean muscle strength (percentage difference to preoperative value) of the abductor was 42.2 Nm (129.6%), adductor 39.4 Nm (131.4%), flexor 48.4 Nm (121%), and extensor 45.8 Nm (130.5%), all of which exceeded the preoperative values. The 12-month postoperative muscle strength of patients with Grade 0 disease based on the Tönnis classification was greater in all directions than that of patients with Grades 1 and 2 disease. The preoperative stage was thought to be an essential factor in postoperative muscle strength recovery. LEVEL OF EVIDENCE: Prognostic study, Level II (lesser quality prospective study--eg, patients enrolled at different points in their disease or < 80% followup). See the Guidelines for Authors a complete description of levels of evidence.

Acetabulum↗

PubMed1994

[Muscle strength training in old age].

Muscle strength decreases with increasing age. The main causes for this are intrinsic age-dependent mechanisms and hypokinesia. Immobilization and bed rest accelerate the loss of muscle strength. A number of studies show that even very old people can increase their strength, sometimes to a surprising degree. Thus, there is considerable potential for strength training in the rehabilitation of the elderly. Adaptation to strength training, the methods for improving strength and the importance of health problems related to strength training are discussed. If carefully planned and supervised, strength training is feasible even in people with chronic diseases like mild hypertension, coronary heart disease and osteoarthritis; actually, strength training may even be beneficial. Also, strength training becomes increasingly important in rehabilitation after orthopedic surgery.

Aged↗

PubMed1998

Muscle strength, task performance and low back load in nurses.

Poor muscle strength, relative to the physical demands of specific jobs, is considered a risk factor for low back pain. To gain an understanding of the underlying mechanisms, this study questioned whether muscle strength was related to task performance and low back load in nursing tasks. Trunk extension, elbow flexion and knee extension strength were therefore measured in 17 nurses. The independent effects of muscle strength on task duration, jerkiness of effort and L5-S1 torque were investigated as the nurses performed several patient handling tasks. Despite a large variation in muscle strength within the subject population, no effect of strength on task duration, jerkiness or L5-S1 torques was observed. In conclusion, poor muscle strength was found not to be related to increased low back load. If 'weaker' nurses were to be at a higher risk, it would be due to a reduced capability to withstand the mechanical load, rather than to an increased mechanical load.

Adult↗

PubMed2006

Muscle strength recovery and its effects on outcome after open reduction and internal fixation of acetabular fractures.

OBJECTIVE: To determine the relationship between muscle strength recovery and functional outcome in patients who were treated for an acetabular fracture via an anterior approach. DESIGN: Case series. SETTING: University Medical Center. PATIENTS: Fifteen patients with a displaced acetabular fracture treated via an anterior, ilioinguinal approach were studied. Hip muscle strength of these patients was then compared with the muscle strength of a similar group of patients treated via a Kocher-Langenbeck approach (posterior approach). These patient groups were then combined and muscle strength recovery was compared with the functional outcome. MAIN OUTCOME MEASURE: Primary outcome measures included hip muscle strength, including work (J/min) and maximum torque (Nm/kg) for abductors/adductors and flexors/extensors. Clinical outcome was assessed with the Musculoskeletal Function Assessment (MFA) questionnaire and the results correlated with muscle strength. Secondary outcome measures included adequacy of fracture reduction, radiographic grade, severity of heterotopic ossification, and range of motion of the affected and unaffected hips. RESULTS: At an average follow-up of 44 months, patients treated via an anterior approach had an overall muscle strength deficit of 9%. Hip extension strength was affected to the least extent (6% deficit when compared with the unaffected hip) whereas abduction, adduction, and flexion strength was affected to a greater degree. For each measure the affected side was typically weaker than the unaffected side. The average MFA score for the anterior approach group was 17 (range, 0 to 47) with most patients reporting poorest results in those domains assessing activities of the arms and legs, and those involving life changes and feelings. When MFA scores were compared with the muscle strength, a relationship was found between hip extension/flexion work and maximum torque and hip adduction work and maximum torque and MFA score. For each of these muscle groups, patients reported worsening function with decreased muscle strength. Assessment of the most recent radiographs revealed 9 patients with an excellent radiographic grade, 3 patients with a good grade, 1 patient with a fair grade, and 2 patients with a poor grade. Hip range of motion was not statistically different when the affected hip was compared with the unaffected hip, and none of these variables correlated with outcome. Heterotopic ossification was found in 8 patients; 4 with grade 1, and 4 with grade 2. CONCLUSIONS: Standardized muscle strength determination and completion of an MFA questionnaire provided a thorough evaluation of patients who had undergone open reduction and internal fixation of a displaced acetabular fracture. In these patients, hip muscle strength after operative treatment of a displaced acetabular fracture directly influences patient outcome. Therefore, in order to maximize the outcome of these patients, particular attention must be paid to postoperative muscle strengthening protocols and accurate and validated methods to assess strength and outcomes.

Acetabulum↗

PubMed1977

Assessment of muscle strength in Duchenne muscular dystrophy.

Muscle strength in 23 patients with Duchenne dystrophy was tested against gravity and manual resistance during an 8-year period. The data show striking linearity in rate of loss of strength with age for any given patient. The tempo does not appear altered during growth spurts, bracing, or loss of ambulation. Variability in disease severity was documented clearly by 7 years of age and appears to be related to earlier age at onset of symptoms. This long ignored method of muscle strength assessment provides a precise measure of disease progression and, since the technique is widely used by physical therapists, it should be incorporated in clinical studies and therapeutic trials.

Age Factors↗

PubMed2004

Motor function-muscle strength relationship in spinal muscular atrophy.

The relationship between motor function and muscle strength in patients with spinal muscular atrophy (SMA) is still controversial. In 120 genetically proven SMA patients, aged 5 years or older, we measured muscle strength in the arms and legs by a hand-held dynamometer, forced vital capacity by a spirometer, and the time needed to walk 10 m, arise from the floor, and climb steps. SMA patients had markedly reduced muscle strength, approximating 20% of that predicted from age- and gender-matched normative data. Knee extensors were the weakest muscles in SMA patients. The young ambulant SMA patients performed better than adults in all the timed tests and had greater muscle strength on knee extension. This study shows a good relationship between motor ability and muscle strength in SMA and confirms that age-related loss of function in SMA is due to loss of muscle strength.

Adolescent↗