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Results for “Muscle Strength Dynamometer”

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PubMed2000

Anaerobic power and muscle strength in young hemophilia patients.

PURPOSE: The purpose of this study was to evaluate muscle strength and anaerobic power in young boys with hemophilia compared with healthy boys. METHODS: Thirteen boys with severe hemophilia (H) (mean (+/- SD) age = 12.0 +/- 3.17 yr) and 16 control (C) boys (age = 11.9 +/- 2.8 yr) performed elbow and knee flexion and extension on the Biodex System II dynamometer at two angular velocities. They also performed a Wingate Anaerobic Test (WAnT) for the legs and for the arms. All H subjects received prophylactic factor VIII treatment in the 24 h pretesting, and no test was performed in the presence of hemorrhage. RESULTS: C were consistently stronger than H in all dynamic strength measures (e.g., elbow flexors: 0.47 +/- 0.15 vs 0.36 +/- 0.08 N x m x kg(-1) for C and H, respectively, P < 0.05). Anaerobic mean power was also higher in C compared with H in both upper and lower extremities (arms: 3.08 +/- 0.99 vs 2.22 +/- 0.46 W x kg(-1) for C and H, respectively; legs: 6.94 +/- 1.62 vs 5.54 +/- 1.03 W x kg(-1) for C and H, respectively, P < 0.05). Upper and lower extremity strength, as well as anaerobic power, increased with age in C but not in H. By using the Godin Leisure-Time Exercise Questionnaire, H were found to be much less active, especially in intense activities, compared with C. CONCLUSION: Children and adolescents with hemophilia are characterized by lower muscle strength and anaerobic power compared with age-matched controls. This may be related to their lower leisure-time activity.

Adolescent↗

PubMed1988

Ratio of hamstring to quadriceps femoris muscles' strength in the anterior cruciate ligament insufficient knee. Relationship to long-term recovery.

The purposes of this study were 1) to investigate the peak torque and total-work ratios of hamstring to quadriceps femoris muscles' (HQ) in 41 subjects (27 male, 14 female; means age = 35 years) with an anterior cruciate ligament insufficient knee (ACLIK) and 2) to determine the relationship between HQ ratios and long-term subject outcome. Quadriceps femoris and hamstring musculature strengths of both legs were measured at follow-up with an isokinetic dynamometer, and peak torque values were recorded at lower (60 degrees/sec) and higher (180 degrees/sec) speeds. Maximal isometric extension and flexion outputs were measured at a 60-degree knee-flexion angle. Three standardized knee-scoring scales were used to determine the overall outcome of the ACLIK. High intersubject variability of the HQ ratios (range = 23%-205%) was observed in all strength tests, including tests of healthy knees. The injured knee of all subjects had a higher HQ ratio (46%-95%) in every test than the healthy knee (42%-85%). The HQ ratio difference between knees was significant at the isokinetic higher speed (p less than .05) and for the total-work (p less than .05) tests because of the weak quadriceps femoris muscle of the injured knee. Outcome scores did not differ significantly between the groups with low, optimal, or high HQ ratios of the ACLIK but were significantly better in subjects whose HQ ratio of the injured knee was similar to that of their uninjured knee.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2002

Effects of a treadmill walking program on muscle strength and balance in elderly people with Down syndrome.

BACKGROUND: Longer life expectancy is resulting in increasing numbers of elderly adults with mental retardation. In elderly adults with Down syndrome (DS), the maintenance of muscle strength, endurance, and dynamic balance are important to ensure quality of life and functional independence. The objective of this study was to compare isokinetic leg strength and dynamic balance of aged mentally retarded individuals with DS (n = 16, mean age 63) before and after a treadmill walking program lasting 6 months in comparison with a nonwalking control group (n = 10) with similar physical characteristics. METHODS: Participants in the study undertook leg strength testing on a dynamometer. Parameters measured included peak torque, peak torque % body weight, and average power % body weight. A "timed get-up and go" functional test for dynamic balance was also analyzed and compared prior to and after the treadmill program. RESULTS: Knee extension and flexion isokinetic strength in elderly individuals with DS showed significant improvement after 6 months of treadmill training. Dynamic balance performance was also significantly improved (p <.05). CONCLUSIONS: Aged adults with DS can significantly improve muscle strength and balance by adopting suitable programs of treadmill walking.

Aged↗

PubMedDate not supplied

Function of the quadriceps and hamstrings muscles in knees with chronic partial deficiency of the anterior cruciate ligament. Isometric and isokinetic evaluation.

We assessed the isokinetic and isometric strength and power profile of the knees of 37 patients who had a previous grade II sprain (partial tear) of the anterior cruciate ligament. Of the 37 knees, 11 had an isolated partial anterior cruciate ligament rupture and 26 had a partial anterior cruciate ligament rupture combined with a partial medial collateral ligament rupture. The Cybex II isokinetic dynamometer was used in the measurements. Eight years after the injury, the mean strength deficit of the injured knees was minimal when compared with the uninjured side. In the hamstrings of both groups, the relative strength deficit increased significantly with a higher speed of isokinetic movement (P less than 0.05). Compared with the strength parameters (peak torques), the other functional parameters (total work, average power, and peak angular impulse) of the injured knees showed some, but not significantly greater, deficits (hamstrings, 7% to 10%; quadriceps, 4% to 10%). We found that the general thigh muscle function in knees with old grade II sprains of the anterior cruciate ligament appears adequate except in flexion where the strength deficits are significantly greater in higher speeds of isokinetic movement. Therefore, rehabilitation using high-speed flexion (and extension) exercises is recommended.

Adult↗

PubMed2001

A randomized two-year study of the effects of dynamic strength training on muscle strength, disease activity, functional capacity, and bone mineral density in early rheumatoid arthritis.

OBJECTIVE: To evaluate the impact of a 2-year program of strength training on muscle strength, bone mineral density (BMD), physical function, joint damage, and disease activity in patients with recent-onset (<2 years) rheumatoid arthritis (RA). METHODS: In this prospective trial, 70 RA patients were randomly assigned to perform either strength training (all major muscle groups of the lower and upper extremities and trunk, with loads of 50-70% of repetition maximum) or range of motion exercises (without resistance) twice a week; all were encouraged to engage in recreational activities 2-3 times a week. All patients completed training diaries (evaluated bi-monthly) and were examined at 6-month intervals. All were treated with medications to achieve disease remission. Maximum strength of the knee extensors, trunk flexors and extensors, and grip strength was measured with dynamometers. BMD was measured at the femoral neck and lumbar spine by dual x-ray densitometry. Disease activity was determined by the Disease Activity Score, the extent of joint damage by the Larsen score, and functional capacity by the Health Assessment Questionnaire (HAQ); walking speed was also measured. RESULTS: Sixty-two patients (31 per group) completed the study. Strength training compliance averaged 1.4-1.5 times/week. The maximum strength of all muscle groups examined increased significantly (19-59%) in the strength-training group, with statistically significant improvements in clinical disease activity parameters, HAQ scores, and walking speed. While muscle strength, disease activity parameters, and physical function also improved significantly in the control group, the changes were not as great as those in the strength-training group. BMD in the femoral neck and spine increased by a mean +/- SD of 0.51 +/- 1.64% and by 1.17 +/- 5.34%, respectively, in the strength-training group, but decreased by 0.70 +/- 2.25% and 0.91 +/- 4.07% in the controls. Femoral neck BMD in the 17 patients with high initial disease activity (and subsequent use of oral glucocorticoids) remained constantly at a statistically significantly lower level than that in the other 45 patients. CONCLUSION: Regular dynamic strength training combined with endurance-type physical activities improves muscle strength and physical function, but not BMD, in patients with early RA, without detrimental effects on disease activity.

Adult↗

PubMed1988

Muscle strength in the triceps surae and objectively measured customary walking activity in men and women over 65 years of age.

1. Objective measurements of the maximal voluntary strength of triceps surae and the amount and speed of customary walking have been made in 56 men and 66 women aged over 65 years, who were living independently. 2. Strength was measured using a dynamometer based upon a hydraulic system (Bourdon tube). Walking was assessed, for amount using a mechanical accelerometer (pedometer) over a week, and for speed using a self-paced test for normal walking over 100 m on the level. The reliability and validity of these methods has been described. 3. The men were significantly stronger (1128 +/- 206 vs 873 +/- 177 N) even after adjustment for body weight; their amount of walking was similar to that of women, but they walked significantly faster (4.8 +/- 0.6 vs 4.2 +/- 0.6 km/h). Men were significantly more active in leisure pursuits (as assessed by questionnaire). 4. Significant associations between strength and chosen normal walking speed were found for both sexes (r = 0.41, P less than 0.001 for men and r = 0.36, P less than 0.01 for women). The amount of walking (daily stepscore as a mean from 7 consecutive days recorded) was significantly but less strongly correlated with strength (r = 0.30, P less than 0.05) in the men only. 5. Multiple regression analysis showed that in men neither age nor amount of walking had any further effect in addition to speed, but in women age had an additional effect (multiple R = 0.48). 6. An association has been demonstrated which raises the possibility of reversing loss of muscle strength through increased daily activity.

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PubMed1995

Shoulder abduction strength measurement in football players: reliability and validity of two field tests.

Musculoskeletal and neurologic injuries affecting shoulder strength are common in contact sports. Full-strength recovery is desired before resumption of competition. On-field assessment of shoulder strength is usually done by manual muscle testing, which lacks sensitivity and reliability. Our objective was to determine the reliability and validity of two field instruments capable of quantifying shoulder abduction strength. Twenty junior football players underwent bilateral isokinetic (60 degrees/s) and isometric shoulder abduction strength measurements using a Cybex 340 isokinetic dynamometer. Test-retest measurements of both shoulders of each player were made using strain gauge (SG) and handheld dynamometer (HHD) instruments. Players were tested during rested and competition conditions. Within and between session reliabilities were calculated using the intraclass coefficient, and validity was assessed using Pearson's correlation coefficient. Overall reliability for each device was calculated using Lisrel analysis. SG was found to be superior to HHD in overall reliability and validity. Within-session reliability in the rested and competition states was 0.75 and 0.78, respectively, for SG and 0.60 and 0.81, respectively, for HHD. Between-session reliability in the rested and competition states dropped to 0.51 and 0.63, respectively, for SG and 0.55 and 0.70, respectively, for HHD. Validity was 0.41 and 0.70 for SG when correlated with Cybex at 0 degree and 60 degrees/s respectively. Validity for HHD was 0.28 and 0.42 for Cybex speeds of 0 degree and 60 degrees/s, respectively. SG reliability and validity were similar when testing was done one shoulder at a time or both shoulders concurrently.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Eccentric and concentric muscle performance in patients with spastic paresis secondary to motor neuron disease. A preliminary report.

This study investigated the potential value of eccentric (ECC) and concentric (CONC) isokinetic testing for quantifying motor deficit in patients with spastic paresis secondary to motor neuron disease. We hypothesized that, at a moderately fast (120 degrees s-1) angular velocity, spastic patients would demonstrate different ECC-CONC torque relationships from healthy controls or patients with non-spastic neuromuscular disorders. Eleven patients with motor neuron disease having clinical evidence of spasticity, and 11 disease-control patients (with non-spastic disorders, e.g. lower motor neuron disease or myopathy) underwent isokinetic testing. One healthy subject was matched to each of the 22 patients. The average torque generated during maximal voluntary ECC and CONC knee flexion (KF) and extension (KE) was measured using an isokinetic dynamometer (Kin-Com). Reliability was established (all ICC > or = 0.97) for patient torque measurements. Relative strength (% of control subject torque) in spastic patients was significantly higher for ECC than for CONC actions in both KF and KE; conversely, in non-spastic disease-control patients relative strength was not affected by the type of muscle action. The ECC/CONC average torque ratios for KE and KF at 120 degrees s-1 were significantly greater in spastic patients than controls, but did not differ from controls in non-spastic patients. In spastic patients the ECC-CONC imbalances were related to ambulatory dysfunction. In four spastic patients followed with serial testing, the disproportion between ECC and CONC voluntary capacity persisted over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Peak torque per unit cross-sectional area differs between strength-trained and untrained young adults.

It is unclear whether gender differences in the relative strength of the upper and lower body are due to differences in muscle mass distribution or dissimilarity of use. There is also controversy as to whether prolonged resistance training increases strength per unit cross-sectional area (CSA). To help resolve these questions, maximum isometric torque per unit muscle and bone (M+B) CSA was measured in the upper arm and thigh of 26 trained (13 males; 13 females) and 26 untrained (13 males; 13 females) young adults. Muscle and bone CSA values were calculated from limb circumferences and skinfolds. Maximal isometric torque values were recorded by a LIDO isokinetic dynamometer. There was no significant difference (P > 0.05) in mean upper arm or thigh torque per unit M+B CSA between the trained males and trained females, or between the untrained males and untrained females. However, mean torque per unit M+B CSA was significantly higher for the trained subjects of both genders compared with the untrained subjects of both genders for the upper arm (28.9%; P < 0.0001) and thigh (18.8%; P < 0.0001). These results suggest that muscle quality (peak torque/CSA) is equal between genders, and that the increase in muscle strength per unit area that occurs with resistance training is not gender-dependent.

Adolescent↗

PubMed1992

Skeletal muscle function in patients with hemophilia A and unilateral hemarthrosis of the knee.

Acute hemarthrosis is a frequent complication of hemophilia A. To test the hypothesis that recurrent hemarthrosis has an adverse effect on neuromuscular function, ten patients with hemophilia A and history of unilateral hemarthrosis of the knee were studied. The uninvolved (U) side was used as the control. The time since diagnosis, factor level, and the number of bleeding episodes in the involved (I) knee averaged 11.6 +/- 6.6 years, 7.7 +/- 5.1%, and 7.0 +/- 7.4, respectively. Neuromuscular function was evaluated on a Cybex 340 isokinetic dynamometer. Knee extensor strength measured at 60 degrees/sec was significantly (p less than .05) lower in the I side (mean = 58Nm) than in the U side (mean = 85Nm). Similarly, lower (p less than .05) total work (I = 479J, U = 656J) and average power output (I = 59W, U = 83W) values were obtained. Adjusting for thigh circumference did not eliminate any of these differences. Testing the extensors at faster angular velocities (180 degrees/sec and 240 degrees/sec) and the flexor muscle groups at the three speeds revealed no differences between I and U. X-rays showed minimal changes. These data show that patients with hemophilia A and history of unilateral hemarthrosis of the knee have neuromuscular dysfunction in the I extremity that precedes the appearance of radiologic evidence of joint pathology. It is suggested that strength training should be started early in the rehabilitation of hemophiliacs.

Adolescent↗

PubMed1988

Physical activity in postmenopausal women: effect on back muscle strength and bone mineral density of the spine.

In this cross-sectional study, the bone mineral density of the lumbar spine, the back extensor strength, and the level of physical activity were determined in 68 healthy, postmenopausal women. Physical activity was determined by a graded questionnaire and varied from sedentary to heavy vocational and avocational activity levels. Bone mineral density (L2 through L4) was measured with dual-photon absorptiometry. Back extensor strength was determined with use of a strain-gauge dynamometer. Bone mineral density ranged from 0.77 to 1.49g/cm2 (mean +/- SD, 1.06 +/- 0.18g/cm2). Back extensor strength ranged from 37 to 145 lb (84.6 +/- 23.5 lb). Physical activity scores ranged from 3 to 13 (8.0 +/- 2.7). Statistical analysis demonstrated a significant positive correlation (r = 0.34, p less than 0.005) between bone mineral density and back extensor strength. Bone mineral density was also positively correlated with the level of physical activity (r = 0.24, p less than 0.05). There was a significant positive correlation between back extensor strength and level of physical activity (r = 0.37, p less than 0.005). The data suggest that levels of physical activity and back muscle strength may be contributors to the bone mineral density of vertebral bodies.

Aged↗

PubMed2001

Study of differences in peripheral muscle strength of lean versus obese women: an allometric approach.

OBJECTIVE: To investigate whether peripheral muscle strength is significantly different between lean and obese women controlled for age and physical activity, using an allometric approach. DESIGN: Cross-sectional study of isometric handgrip and isokinetic leg and trunk muscle strength. SUBJECTS: 173 obese (age 39.9+/-11.4 y, body mass index (BMI) 37.8+/-5.3 kg/m(2)) and 80 lean (age 39.7+/-12.2 y, BMI 22.0+/-2.2 kg/m(2)) women. MEASUREMENTS: Anthropometric measures (weight, height) and body composition (bioelectrical impedance method), isometric handgrip (maximal voluntary contraction on the Jamar dynamometer), isokinetic trunk flexion-extension, trunk rotation, and knee flexion-extension (Cybex dynamometers). RESULTS: Absolute isokinetic strength output (that is, strength uncorrected for fat-free mass) was larger in obese compared to lean women, except for knee flexion and isometric handgrip, which were not significantly different (P>0.05). Pearson correlation coefficients between strength measures and fat-free mass (kg) were low to moderate both in lean (r=0.28-0.53, P<0.05) and in obese (r=0.29-0.49, P<0.001) women. There was no correlation with fat mass (kg) in the lean, whereas in the obese women a weak positive relation could be observed for most isokinetic data (r=0.21-0.39, P<0.01). When correcting for fat-free mass (raised to the optimal exponent determined by allometric scaling), all strength measurements were at least 6% lower in obese when compared to the lean women, except for trunk flexion, which was at least 8% stronger in obese women. DISCUSSION: The higher absolute knee extension strength measures of leg and the similar extension strength of the trunk in the obese sample compared to the lean might be explained by the training effect of weight bearing and support of a larger body mass. However when the independent effect of fat-free mass is removed, these strength measures, as well as oblique abdominal muscle and handgrip strength, turned out to be lower in obese women. These observations could be the reflection of the overall impairment of physical fitness as a consequence of obesity and its metabolic complications.

Adult↗

PubMed2002

The effects of a 10-kilometer run on muscle strength and power.

Recovery of maximal force and power following a 10-km race has not been widely studied in the scientific literature. Ten healthy men who were experienced distance runners participated in this investigation. Data were collected prerace, immediate postrace, and 48 hours postrace to examine the effect of a 10-km race on muscle force production in the lower body. Maximal peak torque was measured via an isokinetic dynamometer at 30 degrees, 180 degrees, and 300 degrees.s-1. A significant (p <or= 0.05) reduction in peak torque for knee flexion was observed at 30 degrees.s-1 immediately postrace. Average power of the knee flexors were significantly decreased immediately postrace. Total work (J) flexion performed over the last 17 repetitions of the 50-repetition test were significantly reduced from baseline values during both the immediate and 48-hour postrace tests. Significant reductions in peak vertical jump force remained reduced 48 hours postrace testing. No changes were observed for jump power after the race. These data indicate that only the hamstring muscle group was not fully recovered to perform the 50-repetition test and that force production in the vertical jump test was compromised 48 hours after a 10-km race. Nevertheless, it appears that strength and power capabilities of the 10-km runner are for the most part restored 48 hours after an all-out 10-km race effort. From a practical perspective, it appears that a minimum of 48 hours should be utilized between multiple trials in 10-km races at track and field meets.

Adolescent↗

PubMed2006

Maintenance of muscle strength may counteract weight-loss-related postmenopausal bone loss--a population-based approach.

INTRODUCTION: Weight loss significantly increases postmenopausal bone loss, but the effects of muscle strength change on weight-loss-associated bone loss remain unclear. The study population, 587 peri- and postmenopausal women, was a random sample of the original Osteoporosis Risk Factor and Prevention Study (OSTPRE) study cohort (n=14,220) in Kuopio, Finland. Bone mineral density (BMD) at the lumbar spine (LS) and femoral neck (FN) was measured with dual x-ray absorptiometry, and grip strength was measured with a pneumatic squeeze dynamometer at baseline in 1989-1991 and at the 10-year follow-up in 1999-2001. METHODS: Women were divided into three groups according to change in age-grouped grip-strength quartile in both of the measurements: "decreased" (n=133), "maintained" (n=300), and "improved" (n=154). In addition, the study sample was divided into two groups according to weight change during the follow-up: weight losers (n=156) and weight gainers (n=431). RESULTS: There were no differences in the change status of grip (muscle) strength between the weight loss and weight gain groups (p>0.500, Pearson chi-square test). Women losing weight during the follow-up and within the improved grip-strength-change group had a significantly lower bone loss rate compared with those in the maintained and decreased grip-strength-change groups (p<0.01 in comparison to the decreased group). This was in contrast to women who gained weight during the follow-up (not significant between any grip-strength-change groups). Furthermore, women who lost body weight and were in the improved grip-strength-change group had a bone loss rate comparable with that of the women who gained body weight (not significant). This was in contrast to the maintained (p<0.05 between weight losers versus gainers in LS) and decreased grip-strength-change groups (p<0.01 weight losers versus gainers in LS and FN). CONCLUSION: The present study suggests that maintaining muscle strength may counteract postmenopausal bone loss related to weight loss. Accordingly, exercise that improves muscle strength may be encouraged for postmenopausal women with weight loss intentions for other health reasons.

Absorptiometry, Photon↗

PubMed1980

Effects of strength training and immobilization on human muscle fibres.

Seven healthy male subjects were studied under control conditions and following 5-6 months of heavy resistance training and 5-6 weeks of immobilization in elbow casts. Cross-sectional fibre areas and nuclei-to-fibre ratios were calculated from cryostat sections of needle biopsies taken from triceps brachii. Training resulted in a 98% increase in maximal elbow extension strength as measured by a Cybex dynamometer, while immobilization resulted in a 41% decrease in strength. Both fast twitch (FT) and slow twitch (ST) fibre areas increased significantly with training by 39% and 31%, respectively. Immobilization resulted in significant decreases in fibre area by 33% for FT and 25% for ST fibres. The observed nuclei-to-fibre ratio was 10% greater following the training programme. However, this change was non-significant. There was also a non-significant correlation between the magnitude of the changes in fibre size and the changes in maximal strength following either training or immobilization.

Adult↗

PubMed2004

Physical disability and muscular strength in relation to obesity and different body composition indexes in a sample of healthy elderly women.

OBJECTIVES: The aim of the present study was to test the association between muscular strength, functional limitations, body composition measurements and indexes of sarcopenia in a sample of community-dwelling, elderly women at the high end of the functional spectrum. DESIGN: Cross-sectional. SUBJECTS: In all, 167 women aged 67-78 y were selected from the general population in central Verona. A group of 120 premenopausal healthy women aged 20-50 y represented the young reference group. MEASUREMENTS: Body weight, height, body mass index (BMI) and the presence of acute and chronic conditions were evaluated in each subject. Body composition was measured by dual-energy X-ray absorptiometry (DXA). Physical functioning was assessed using a modified version of the Activities of Daily Living Scale. Dominant leg isometric strength was measured with a Spark Handheld Dynamometer. RESULTS: Elderly women with BMI higher than 30 kg/m(2) and in the highest quintile of body fat percent showed a significantly higher prevalence of functional limitation. In our population study, about 40% of sarcopenic elderly women and 50% of elderly women with high body fat and normal muscle mass were functionally limited. The prevalence of functional limitation significantly increased in subjects with class II sarcopenia, defined according to the skeletal muscle mass index (SMI=skeletal muscle mass/body mass x 100). In logistic regression models, after adjusting for age and different chronic health conditions, subjects with BMI higher than 30 kg/m(2), in the highest quintile of body fat, or with high body fat and normal muscle mass or class II sarcopenia according to SMI, had a 3-4 times increased risk of functional limitations. Finally, isometric leg strength was significantly lower in subjects in the lowest quintile of relative muscle mass and in sarcopenic and sarcopenic obese women. CONCLUSIONS: High body fat and high BMI values were associated with a greater probability of functional limitation in a population of elderly women at the high end of the functional spectrum. Among the different indexes of sarcopenia used in this study, only SMI predicted functional impairment and disability. Isometric leg strength was significantly lower in subjects with sarcopenia and sarcopenic obesity.

Absorptiometry, Photon↗

PubMed1996

Assessment of extensor and flexor strength in the individual gonarthrotic patient: interpretation of performance changes.

The intra-session and inter-session reproducibility of knee extensor and flexor strength measurements were examined in 21 gonarthrotic subjects (ten women and eleven men). Using the Cybex 6000 dynamometer, isokinetic peak torque and total work at 30 and 120 degrees/second and isometric peak torque were measured three times on separate days within two weeks by the same examiner. The reproducibility of walking and stair climbing time measurements was also assessed. The concept of critical difference (i.e. the difference between two measurements which would be statistically significant when applied to a reference group in steady state) for the interpretation of muscle strength data obtained by monitoring individual patients is presented. Individual coefficients of variation (CV) were calculated for each muscle strength variable. Depending on the velocity and on whether peak torque or total work were measured, the median CV of intra-session and inter-session extensor strength measurements ranged from 1.5-4.9% and 7.4-10.1%, respectively. CVs for flexor strength measurements were significantly higher. Substantial variability of within subject variances were found, e.g. the 80% central range of CVs for extensor torque at 30 degrees/second was 2.5-29.5% (inter-session). Calculated from CVs, critical differences for inter-session measurements exceeded 30% for all muscle strength variables. Median CVs for walking and stair-climbing time were 7.0% and 4.9%, respectively. In conclusion, the large CVs and corresponding critical differences may be a major limitation in the use of muscle strength measurements in the individual gonarthrotic patient.

Aged↗

PubMed2005

Shared genetic and environmental effects on strength and power in older female twins.

PURPOSE: This study examined the relative contribution of genetic and environmental effects on maximal leg extensor power and also investigated whether leg extensor power and maximum voluntary isometric knee extensor strength share a genetic component. METHODS: Muscle functions were measured as part of the Finnish Twin Study on Aging in 101 monozygotic (MZ) and 116 dizygotic (DZ) female twin pairs aged 63-76 yr. Leg extensor power was measured using the Nottingham Leg Extensor Power Rig and maximum voluntary isometric knee extensor strength using an adjustable dynamometer chair. The analyses were carried out using the maximum likelihood method in Mx-program on the raw data set. RESULTS: A bivariate Cholesky decomposition model showed that leg extensor power and isometric knee extensor strength shared a genetic component in common, which accounted for 32% of the total variance in leg extensor power and 48% in isometric knee extensor strength. In addition, power and strength had a nonshared environmental effect in common accounting for four percent of the variance in power and 52% in strength. Remaining variance for leg extensor power was due to trait-specific shared and nonshared environmental effects. CONCLUSION: Observed genetic effect in common for leg extensor power and maximum voluntary isometric knee extensor strength indicated that these two traits are regulated by the same genes. However, also environmental effects have a significant role in explaining the variability in power and strength.

Aged↗