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PubMed2004

The muscle strength and bone density relationship in young women: dependence on exercise status.

AIM: Numerous studies report an association between muscle strength and bone mineral density (BMD) in young and older women. However, the participants are generally non-athletes, thus it is unclear if the relationship varies by exercise status. Therefore, the purpose was to examine the relationships between BMD and muscle strength in young women with markedly different exercise levels. METHODS EXPERIMENTAL DESIGN: cross-sectional. SETTING: a University research laboratory. PARTICIPANTS: 18 collegiate gymnasts and 22 age- and weight-matched recreationally active control women. MEASURES: lumbar spine, femoral neck, arm, leg and whole body BMD (g/cm(2)) were assessed by dual X-ray absorptiometry. In addition, lumbar spine and femoral neck bone mineral apparent density (BMAD, g/cm(3)) was calculated. Handgrip strength and knee extensor and flexor torque (60 degrees /s) were determined by dynamometry, and bench press and leg press strength (1-RM) using isotonic equipment. RESULTS: BMD at all sites and bench press, leg press and knee flexor strength were greater in gymnasts than controls (p<0.001). In controls, knee extensor torque was significantly correlated to femoral neck, limb and whole body BMD (r=0.47-0.55, p<0.05), leg press strength was associated with limb and whole body BMD (r=0.52-0.74, p<0.05), and bench press strength with arm BMD (r=0.50, p=0.019). In partial correlations controlling for weight, leg press strength was related to leg and whole body BMD (r=0.46-0.63, p<0.05). There was no association between muscle strength and BMD in gymnasts. CONCLUSION: These results suggest that the association between muscle strength and BMD in young women is dependent on exercise status. The osteogenic effect of increased mechanical loading associated with gymnastics training likely contributes to the dissociation of the relationship in gymnasts.

Absorptiometry, Photon↗

PubMed2004

Level walking and ambulatory capacity in persons with incomplete spinal cord injury: relationship with muscle strength.

STUDY DESIGN: Prospective analysis of relationships. OBJECTIVES: (1) To quantify the relationship between individual lower extremity muscle strength and functional walking measures and (2) to determine whether a multiple regression model incorporating lower extremity muscle strength could predict the performance of functional walking measures in persons with incomplete spinal cord injury (ISCI) living in the community. SETTING: Tertiary rehabilitation center, Vancouver, Canada. METHODS: In all, 22 subjects with ISCI participated. The relationship between functional walking measures (gait speed, 6-min-walk distance, and ambulatory capacity) and muscle strength (manual tests of hip flexors/extensors/abductors, knee flexors/extensors, ankle dorsiflexors/plantarflexors, and great toe extensors) were measured by Pearson's correlation and regression procedures. RESULTS: For both the more and less affected sides, hip flexors, hip extensors, and hip abductors produced the highest correlations with the three functional measures. The less affected hip flexor strength explained more than 50% of the variance in gait speed and 6-min-walk distance while the less affected hip extensor strength explained up to 64% of the variance in ambulatory capacity. For all three functional measures, the strength of the less affected limb was more important than that of the more affected limb. CONCLUSIONS: Lower extremity muscle strength, in particular that of hip flexors, hip extensors, and hip abductors, is an important determinant of functional walking performance.

Adult↗

PubMed2025

Exercise Therapy in Down Syndrome: A Systematic Review and Meta-Analysis Focused on Muscle Strength, Redox Balance, and Inflammatory Profile.

OBJECTIVE: This study systematically reviewed and meta-analyzed randomized and quasi-randomized controlled trials investigating the impact of exercise therapy on muscle strength, redox balance, and inflammatory profile in individuals with Down syndrome. DESIGN: Systematic review and meta-analysis. DATA SOURCES: Cochrane Central Register of Controlled Trials, MEDLINE, CINAHL, SPORTDiscus, EMBASE, and PEDro. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Randomized and quasi-randomized controlled trials exploring exercise therapy effects on muscle strength and redox balance in individuals with Down syndrome. Although no initial restrictions on age, gender, or health condition were applied during the search process, all included studies focused on adult participants (>18 yr old). No language restrictions were applied, and the search covered the period from 1970 to 2021. RESULTS: We assessed the abstract of 1964 studies. Of the 46 studies meeting the inclusion criteria for the period 2004-2021, 32 focused on muscle strength, and 14 examined redox balance and inflammation. A total of 1611 participants with a mean age of 27 yr were included. This review confirmed that different exercise modalities are prone to improve muscle strength (random effect (95% confidence interval): 0.66, 0.54 to 0.78), redox balance and inflammatory profile (random effect (95% confidence interval): -1.04, -1.31 to -0.76) in this population. The multimodel inference suggested that the frequency of training (times per week) might play a significant role in the main effect. Unsupervised machine learning algorithms displayed a pattern-based graphic representation to assess heterogeneity. CONCLUSIONS: Exercise training demonstrated a positive impact on muscle strength in adults with Down syndrome. The review provides valuable insights into the effects of exercise therapy on individuals with Down syndrome, emphasizing the need for tailored training prescriptions.

Humans↗

PubMed2003

Comparison of maximal voluntary isometric contraction and hand-held dynamometry in measuring muscle strength of patients with progressive lower motor neuron syndrome.

Context. Maximal voluntary isometric contraction, a method quantitatively assessing muscle strength, has proven to be reliable, accurate and sensitive in amyotrophic lateral sclerosis. Hand-held dynamometry is less expensive and more quickly applicable than maximal voluntary isometric contraction. Objective. To investigate if hand-held dynamometry is as reliable and valid as maximal voluntary isometric contraction in measuring muscle strength in patients with an adult-onset, non-hereditary progressive lower motor neuron syndrome. Design. Two testers performed maximal voluntary isometric contraction and hand-held dynamometry measurements in six muscle groups bilaterally in patients with progressive lower motor neuron syndrome to assess reliability and validity of both the methods. Setting. Outpatient units of an academic medical center. Patients. A consecutive sample of 19 patients with non-hereditary progressive lower motor neuron syndrome (median disease duration 32.5 months, range 10-84) was tested. Outcome measures. Comparison between maximal voluntary strength contractions as measured by hand-held dynamometry and maximal voluntary isometric contraction. Results. Low intra- and interrater variation in all muscle groups were found, intraclass correlation coefficients vary between 0.86 and 0.99 for both methods. Both methods correlated well in all muscle groups with Pearson's correlation coefficients ranged between 0.78 and 0.98. Scatter plots indicated a trend to under-estimate muscle strength above 250 N by hand-held dynamometry as compared with maximal voluntary isometric contraction. Conclusions. For longitudinal evaluation of muscle strength in patients with progressive lower motor neuron syndrome (i.e. between 0 and 250 N), muscle strength can be accurate quantified with both hand-held dynamometry and maximal voluntary isometric contraction. Hand-held dynamometry has the advantage of being cheap and quickly applicable. However, our results indicate that hand-held dynamometry is less sensitive than maximal voluntary isometric contraction in detecting subnormal muscle strength in strong muscle groups (i.e. >250 N), due to limited strength of the tester.

Adult↗

PubMed2004

Functional status and muscle strength in people with Duchenne muscular dystrophy living in the community.

OBJECTIVE: To describe activity limitation of people with Duchenne muscular dystrophy who are living in the community and to correlate it with age and muscle strength. DESIGN: Descriptive, correlational. SUBJECTS: Twenty-seven children with Duchenne muscular dystrophy aged 7-14 years who are living in the community. METHODS: The subjects' activity limitation was evaluated using the Functional Independence Measure and the muscle strength of their major upper and lower limb muscles was evaluated with manual muscle testing. The Functional Independence Measure was correlated with age and manual muscle testing, and the pattern of activities of daily living limitations and factors related to it were analysed. RESULTS: There were significant correlations between age and averaged MMT score (Spearman's rho = -0.63, p < 0.01), age and Functional Independence Measure motor score (rho = -0.52, p < 0.01), and Functional Independence Measure motor score and averaged manual muscle testing (rho = 0.77, p < 0.01). At similar manual muscle testing level, children with good cognitive function (Functional Independence Measure cognitive score > or = 26) showed significantly higher Functional Independence Measure motor scores than those with poor cognitive function (Mann-Whitney U test, p < 0.01). For individual Functional Independence Measure items, eating and bowel management were the easier, whereas transfer and stair climbing were the more difficult. Patients with mean muscle strength > or = grade 3 were rated as relatively independent, while those with a mean muscle strength < grade 3 were rated as maximal or total assistance (Mann-Whitney U test, p < 0.05). CONCLUSION: Activities of daily living in patients with Duchenne muscular dystrophy are related to age and muscle strength, and manual muscle testing grade 3 is an important cut-off point to predict their disability.

Activities of Daily Living↗

PubMed1998

Isometric muscle strength is an indicator of self-reported physical functional disability in patients with rheumatoid arthritis.

The objective of our study was to examine (1) whether isometric muscle strength contributes to the explanation of the physical functional disability of a rheumatoid arthritis (RA) patient population after accounting for other disease parameters and demographic variables and (2) whether change in isometric muscle strength is an indicator of change in physical functional disability. Sixty-five consecutive patients fulfilling the American Rheumatism Association 1987 revised criteria for RA were included in the study. Isometric muscle strength was measured with a validated Muscle Strength Index (MSI) calculated as the mean score of standardized isometric extension and flexion strength of the knee and elbow joints. Physical functional disability was measured with the physical dimension of the Health Assessment Questionnaire (HAQ). For 56 patients, we could obtain 1 yr follow-up data. Cross-sectionally, there was a significant correlation (r = -0.51, P < 0.01) between the MSI and the HAQ. Muscle strength remained a significant determinant of the HAQ in multivariate analysis accounting for disease and demographic variables. Longitudinally, change in MSI explained additional variance of change in HAQ after accounting for change in pain, the most important correlate of change in HAQ.

Adult↗

PubMed2000

Relationship of skeletal muscle mass, muscle strength and bone mineral density in adults with cystic fibrosis.

Few studies have investigated peripheral muscle strength and quality in patients with cystic fibrosis (CF). The present study tested the isometric and isokinetic strength of the quadriceps and hamstrings using an isokinetic dynamometer and a strength-testing chair in 25 CF adults and 25 controls. Total body and leg muscle mass were determined by dual-energy X-ray absorptiometry, and bone mineral density (BMD) was also measured. Both muscle strength and muscle mass (total body and leg) were decreased in the CF group. In both groups there was a highly significant relationship between quadriceps strength and leg muscle mass (CF, r=0.7, P=0.0002; controls, r=0.6, P=0.0013). When strength was normalized for muscle size, there was no significant difference between the two groups. Total body and leg BMD were significantly reduced in CF subjects compared with controls. However, when corrected for height, the differences disappeared. There was a significant relationship found between leg muscle mass and leg BMD. We conclude that CF adults are significantly weaker than controls. This is due to lower muscle mass, and not to a reduced force-generating capacity of the muscle, implying that there is no decrease in the quality of CF muscle. BMD is also reduced in CF subjects, and this appears to be related to shorter stature in this group.

Absorptiometry, Photon↗

PubMed2007

Cardiopulmonary exercise capacity, muscle strength, and physical activity in children and adolescents with achondroplasia.

OBJECTIVE: To study in children with achondroplasia the response to exercise and muscle strength compared with healthy peers and to describe the relation between exercise capacity, anthropometric factors, and physical activity. STUDY DESIGN: Patients (7 boys and 10 girls; mean age, 11.8 +/- 3.3 years) with achondroplasia performed a maximal treadmill exercise test. Anthropometric variables and muscle strength were measured and compared with the general population. The level of everyday physical activity was measured by using a diary. Functional ability was measured by using the Activity Scale for Kids. RESULTS: The exercise capacity of the children with achondroplasia was significantly reduced compared with reference values. All anthropometrical measurements differed significantly from reference values. There was a decrease in muscle strength in almost all muscle groups. We found a reduced physical activity level and impairments in functional ability. CONCLUSIONS: Cardiopulmonary exercise capacity and muscle strength in children with achondroplasia was reduced compared with reference values. Children with achondroplasia have a unique response to exercise. Clinicians should take these characteristic differences into account when the exercise capacity of subjects with achondroplasia is being tested.

Achondroplasia↗

PubMed2006

Respiratory muscle strength and cough capacity in patients with Duchenne muscular dystrophy.

The function of inspiratory muscles is crucial for effective cough as well as expiratory muscles in patients with Duchenne muscular dystrophy (DMD). However, there is no report on the correlation between cough and inspiratory muscle strength. To investigate the relationships of voluntary cough capacity, assisted cough techniques, and inspiratory muscle strength as well as expiratory muscle strength in patients with DMD (n= 32). The vital capacity (VC), maximum insufflation capacity (MIC), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) were measured. Unassisted peak cough flow (UPCF) and three different techniques of assisted PCF were evaluated. The mean value of MICs (1918 +/- 586 mL) was higher than that of VCs (1474 +/- 632 mL) (p < 0.001). All three assisted cough methods showed significantly higher value than unassisted method (212 +/- 52 L/min) (F = 66.13, p < 0.001). Combined assisted cough technique (both manual and volume assisted PCF; 286 +/- 41 L/min) significantly exceeded manual assisted PCF (MPCF; 246 +/- 49 L/ min) and volume assisted PCF (VPCF; 252 +/- 45 L/min) (F = 66.13, p < 0.001). MIP (34 +/- 13 cmH2O) correlated significantly with both UPCF and all three assisted PCFs as well as MEP (27 +/- 10 cmH2O) (p < 0.001). Both MEP and MIP, which are the markers of respiratory muscle weakness, should be taken into account in the study of cough effectiveness.

Adolescent↗

PubMed1997

Dynamic muscle strength alterations to detraining and retraining in elderly men.

To investigate the effects of cessation and subsequent resumption of training on muscle strength in elderly men, 11 men (aged 65-77 years), just completing a 24-week randomized controlled trial of recombinant human growth hormone (rhGH) and resistance exercise (rhGH, n = 6; placebo, n = 5), detrained for 12 weeks and subsequently retrained for 8 weeks. During the detraining and retraining phase, subjects did not receive rhGH. The resistance programme included three sets of eight repetitions at 75% of one-repetition maximum (1-RM), three times per week, for 10 upper and lower body exercises. Dynamic muscle strength was assessed by the 1-RM method every 2 weeks for 44 weeks. Needle biopsies of vastus lateralis muscle were obtained from seven men. Muscle strength increased during initial training by 40.4 +/- 5.5% (mean +/- SEM), ranging from 26.0 +/- 5.0 to 83.9 +/- 15.6%, depending on muscle group. Increased strength was accompanied by hypertrophy (P < 0.05) of type I (17.4 +/- 4.1%) and II (25.8 +/- 12.4%) muscle fibres. Of initial strength gains, only 29.9 +/- 5.2% was lost with detraining. However, type I and II fibre cross-sectional area reverted to pretraining values. After 8 weeks of retraining, muscle strength returned to trained values, but without a significant change in fibre morphology. The results indicate that elderly men lose some muscle strength following short-term detraining, but that only a brief period of retraining suffices to regain maximal strength. Reversal of fibre cross-sectional area with detraining, and only modest improvement with retraining, suggests that much of the retention in strength with detraining and reacquisition of lost strength with retraining reflects neural adaptation.

Aged↗

PubMed1991

The effect of mediolateral episiotomy at delivery on pelvic floor muscle strength evaluated with vaginal cones.

In a prospective study, pelvic floor muscle strength was investigated pre- and post partum in 87 women with uncomplicated pregnancies. Those vaginally delivered were 71 primiparas, while 16 underwent an elective cesarean section. The objective was to evaluate the effect of the delivery procedure on the pelvic floor muscle strength with the aid of vaginal cones. In the group of women with vaginal delivery three subgroups were identified: episiotomy, spontaneous laceration and intact perineum. Pelvic floor muscle strength was weakest in the episiotomy subgroup, the difference in values between this subgroup and each of the other subgroups and the elective cesarean section group being significant. No significant difference was evident between the spontaneous lacerations and intact perineum subgroups.

Adult↗

PubMedDate not supplied

Timing of surgery in acute anterior cruciate ligament tears on the return of quadriceps muscle strength after reconstruction using an autogenous patellar tendon graft.

To determine if patients who delayed anterior cruciate ligament reconstruction until a convenient time regained quadriceps muscle strength allowing them to return to sports participation at a different rate than patients who had early surgery for anterior cruciate ligament reconstruction, we studied 143 patients who had the same surgical procedure and postoperative rehabilitation program. Group I delayed surgery at a mean of 40 days after injury; Group II had early surgery at a mean of 11 days after injury. Statistically, Group I patients had significantly better mean quadriceps muscle strength at 2 months (P = 0.017) and at 4 months (P = 0.0055) postoperatively. At least 65% quadriceps muscle strength was achieved by 40 of the 50 patients (80%) tested in Group I at 2 months, allowing the patients to progress to sport-specific rehabilitation. Only 35 of the 66 patients (53%) tested in Group II were able to progress toward sports activities at 2 months. By 6 months, 29 of the 40 patients (73%) tested in Group I compared with 27 of the 58 patients (47%) tested in Group II had 80% quadriceps muscle strength. This study demonstrates that the return of quadriceps muscle strength was faster for our patients who delayed anterior cruciate ligament reconstruction than for our patients who had early reconstruction. Thus, despite delaying their early reconstructions, Group I was able to progress sooner from the date of surgery to sport-specific rehabilitation.

Acute Disease↗

PubMed2002

Effects of electrical muscle stimulation on body composition, muscle strength, and physical appearance.

Electrical muscle stimulation devices (EMS) have been advertised to increase muscle strength, to decrease body weight and body fat, and to improve muscle firmness and tone in healthy individuals. This study sought to test those claims. Twenty-seven college-aged volunteers were assigned to either an EMS (n = 16) or control group (n = 11). The EMS group underwent stimulation 3 times per week following the manufacturer's recommendations, whereas the control group underwent concurrent sham stimulation sessions. Bilaterally, the muscles stimulated included the biceps femoris, quadriceps, biceps, triceps, and abdominals (rectus abdominus and obliques). An identical pre- and posttesting battery included measurements of body weight, body fat (via skinfolds), girths, isometric and isokinetic strength (biceps, triceps, quadriceps, hamstrings), and appearance (via photographs from the front, side, and back). EMS had no significant effect on the any of the measured parameters. Thus, claims relative to the effectiveness of EMS for the apparently healthy individual are not supported by the findings of this study.

Adolescent↗

PubMed1997

Two years of growth hormone (GH) treatment increase isometric and isokinetic muscle strength in GH-deficient adults.

GH deficiency in adults is associated with reduced muscle mass and muscle strength. The objective of this trial was to follow the effect of 2 yr of GH treatment in GH-deficient adults on muscle performance in relation to a reference population. Knee extensor and flexor strengths for isometric and isokinetic concentric muscle strength were measured using a Kin-Com dynamometer. Hand-grip strength was measured in both hands. The fatigue index was calculated as the percent reduction in peak torque at 50 repeated isokinetic knee extensions. Superimposed, single twitch electrical stimulation was performed. The GH-deficient subjects had lower isometric knee extensor, knee flexor, and hand-grip strength than the reference population. Two years of GH treatment increased and normalized the mean isometric knee extensor and flexor strengths. The concentric knee flexor and extensor strength at an angular velocity of pi rad/s increased, as did the concentric knee flexor strength at an angular velocity of pi/3 rad/s. The increase in muscle strength was more marked in younger patients and in patients with lower initial muscle strength than predicted. Quadriceps endurance decreased, whereas the effect of superimposing single twitches on isometric contraction and hand-grip strength was unaffected by the GH treatment. Two years of GH therapy in GH-deficient adults increased and normalized isokinetic and isometric muscle strength studied in proximal muscle groups. Hand-grip strength and the degree of lack of maximal motor unit activation on voluntary isometric knee extensor force did not change. The dynamic local muscle fatigue index decreased.

Adult↗

PubMed2002

Bone density in female elite gymnasts: impact of muscle strength and sex hormones.

PURPOSE: The aim of this study was to investigate BMD in Danish female elite gymnasts and the relationships to maximal muscle strength, sex hormone concentrations, and menstrual status. METHODS: Six artistic gymnasts, five rhythmic gymnasts, and six controls aged 15-20 yr served as subjects. BMD (g x cm(-2)) of lumbar spine, proximal femur, distal radius, and whole body were measured by dual-energy x-ray absorptiometry (DXA) scanning. Maximal muscle strength (Nm) was measured in isokinetic trunk extension, trunk flexion, and knee extension. Serum concentrations of estrogen and progesterone in follicular and luteal phases were evaluated. RESULTS: Three out of six artistic gymnasts had amenorrhea, and two artistic and one rhythmic gymnast experienced oligomenorrhea. BMD in artistic gymnasts was greater than controls (24-45%, P < 0.05) in all sites except whole body. BMD in rhythmic gymnasts was greater than controls (4-26%, P < 0.05) in all sites except distal radius. In gymnasts, BMD correlated to both maximal muscle strength (0.60 < r < 0.85, P < 0.05) and serum progesterone (0.65 < r < 0.75, P < 0.05). CONCLUSION: In spite of oligomenorrhea or amenorrhea, it is possible for female gymnasts to maintain a high BMD in both the axial (L2-L4) and appendicular skeleton. The correlations between BMD and maximal muscle strength and progesterone concentration in gymnasts may indicate that within the same athletic group, progesterone concentration has a permissive role in bone formation, thus affecting the positive impact of muscle strength.

Adaptation, Physiological↗

PubMed2004

Isokinetic leg muscle strength in older americans and its relationship to a standardized walk test: data from the national health and nutrition examination survey 1999-2000.

OBJECTIVES: To describe isokinetic knee extensor muscle strength in older U.S. men and women by age and race/ethnicity and to ascertain its relationship to a standard, timed walking-speed test. SETTING: The U.S. National Health and Nutrition Examination Survey (NHANES) 1999-2000. DESIGN: A cross-sectional nationally representative health examination survey. PARTICIPANTS: All surveyed persons aged 50 and older (N=1,499) who performed muscle strength and timed walk examinations in the NHANES mobile examination center. MEASUREMENTS: Concentric peak torque (strength) of the knee extensors at 1.05 rads/ s(-1) velocity and a 6-m walk timed in seconds. RESULTS: Knee extensor strength was inversely associated with age (P<.01), and women had less knee extensor muscle strength than men (P<.01). After adjustment for standing height, no significant difference in muscle strength was found across the three race/ethnicity groups (Mexican Americans, non-Hispanic blacks, and non-Hispanic whites) for men or women. After adjustment for age, race/ethnicity, weight, and height, increasing knee extensor strength was associated with significant increases in meters walked per second (P<.01). CONCLUSION: Knee extensor muscle strength is affected by age and sex but not by race/ethnicity and it is significantly associated with timed walk.

Black or African American↗

PubMed1980

Towards an objective assessment of the "maximal voluntary contraction" component in routine muscle strength measurements.

Routine measurements of muscle strength capabilities commonly use external dynamometers against which the subject exerts maximal voluntary contractions of muscles in static (isometric) tests. These tests require active cooperation of the subject, i.e., full motivation to "give the best". At present, no practicable techniques exist that provide objective clues indicating that indeed a maximal effort is delivered, or if only a portion of the available strength is exerted. This paper describes experiments performed with 30 subjects which indicate that the rate of strength build-up in repeated exertions may provide objective criteria to judge whether or not a subject exerts full muscular strength in a routine test.

Female↗

PubMed2002

Effect of posture on oxygenation and respiratory muscle strength in convalescent infants.

OBJECTIVE: To determine if differences in respiratory muscle strength could explain any posture related effects on oxygenation in convalescent neonates. METHODS: Infants were examined in three postures: supine, supine with head up tilt of 45 degrees, and prone. A subsequent study was performed to determine the influence of head position in the supine posture. In each posture/head position, oxygen saturation (SaO2) was determined and respiratory muscle strength assessed by measurement of the maximum inspiratory pressure (PIMAX). PATIENTS: Twenty infants, median gestational age 34.5 weeks (range 25-43), and 10 infants, median gestational age 33 weeks (range 30-36), were entered into the first and second study respectively. RESULTS: Oxygenation was higher in the prone and supine with 45 degrees head up tilt postures than in the supine posture (p<0.001), whereas PIMAX was higher in the supine and supine with head up tilt of 45 degrees postures than in the prone posture (p<0.001). Head position did not influence the effect of posture on PIMAX or oxygenation. CONCLUSION: Superior oxygenation in the prone posture in convalescent infants was not explained by greater respiratory muscle strength, as this was superior in the supine posture.

Female↗