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PubMed1997

Relationship between isokinetic muscle strength and exercise capacity in chronic heart failure.

The exercise intolerance and excessive ventilatory response to exercise of chronic heart failure is associated with abnormalities of skeletal muscle function, in particular a reduction in muscle strength. Isometric and isokinetic leg muscle strength were measured in 10 patients with chronic heart failure and 10 age-matched controls. Each subject undertook maximal exercise testing to measure peak oxygen consumption (V(O2)) and the ventilatory response to exercise as measured by the slope of the relation between ventilation and carbon dioxide production (V(E)/V(CO2) slope). Quadriceps strength (mean (S.D.)) was reduced in heart failure as measured by isometric (444.9 (129.6) N vs. 556.0 (136.0); P<0.01) and isokinetic (123.6 (30.2) Nm vs. 146.8 (40.0); P=0.04). Hamstring strength was also reduced as measured by isokinetic testing (53.6 (15.6) Nm vs. 71.1 (28.1); P=0.02). Isokinetic and isometric strengths correlated, but not closely (r=0.52, P<0.001). There were negative correlations between the V(E)/V(CO2) slope, and isokinetic measures: with average torque, r=-0.62, P<0.004; with peak torque, r=-0.64, P=0.002. We have found evidence for reduced muscle function affecting both knee flexors and extensors. This reduction in muscle strength correlates with the ventilatory response to exercise. These observations lend support to the muscle hypothesis of the generation of symptoms in chronic heart failure.

Angiotensin-Converting Enzyme Inhibitors↗

PubMedDate not supplied

Achilles tendinosis and calf muscle strength. The effect of short-term immobilization after surgical treatment.

We prospectively studied calf muscle strength in 7 men and 4 women (mean age, 40.9 +/- 10.1 years) who had surgical treatment for chronic Achilles tendinosis. Surgery was followed by immobilization in a weightbearing below-the-knee plaster cast for 2 weeks followed by a stepwise increasing strength training program. Strength measurements (peak torque and total work) were done preoperatively (Week 0) and at 16, 26, and 52 weeks postoperatively. We measured isokinetic concentric plantar flexion strength at 90 and 225 deg/sec and eccentric flexion strength at 90 deg/sec on both the injured and noninjured sides. Preoperatively, concentric and eccentric strength were significantly lower on the injured side at 90 and 225 deg/sec. Postoperatively, concentric peak torque on the injured side decreased significantly between Weeks 0 and 16 and increased significantly between Weeks 26 and 52 at 90 deg/sec but was significantly lower than that on the noninjured side at all periods and at both velocities. The eccentric strength was significantly lower on the injured side at Week 26 but increased significantly until at Week 52 no significant differences between the sides could be demonstrated. It seems, therefore, that the recovery in concentric and eccentric calf muscle strength after surgery for Achilles tendinosis is slow. We saw no obvious advantages in recovery of muscle strength with a short immobilization time (2 weeks) versus a longer (6 weeks) period used in a previous study.

Achilles Tendon↗

PubMedDate not supplied

Fat mass rather than muscle strength is the major determinant of physical function and disability in postmenopausal women younger than 75 years of age.

OBJECTIVE: Few studies have investigated the relationships between body composition, functional ability, and age-related disability in postmenopausal women. We investigated the relative role of fat mass, lean mass, and muscle strength in the development of disability in a group of healthy postmenopausal women younger than 75 years. DESIGN: We performed a cross-sectional study among 396 independently living women aged 56-73 years, randomly selected between 8 and 30 years after menopause. Lean mass and fat mass were assessed by dual-energy x-ray absorptiometry. Muscle strength (grip and leg extensors) was assessed using dynamometry. Functional ability was estimated by Physical Performance Score, physical activity during the preceding year, and impairment in activities of daily living. RESULTS: Of the participants, 43.7 % were overweight (25 > or = BMI < 30 kg/m2), and 17.7% were obese (BM I > or = 30 kg/m2). Higher muscle strength was observed with increasing lean body mass, and participants with higher muscle strength scored better in the physical performance score and activities of daily living. Higher fat mass was significantly associated with a lower physical performance score, lower physical activity, and a higher frequency of disability. Increasing fat mass was associated with increasing lean mass and decreasing lean/fat ratio. The increase in lean mass and muscle strength associated with higher fat mass was mainly localized in the legs. CONCLUSIONS: Our results support the role of fat mass as the primary risk marker for disability, which might later accelerate by the age-related decrease in lean mass and the development of sarcopenia after the age of 75 years.

Absorptiometry, Photon↗

PubMed1978

Muscle strengths in relation to fat storage rate in young men.

Hand-grip strength, elbow flexion strength, trunk extension strength and knee extension strength, and body composition (measured by densitometry) were measured in 59 male students (mean 19.2 years) in order to compare the muscle strength of obese men, in relation to fat storage rate (% fat), with those of non-obese men. Their % fat ranged from 6.2-35.6%. Correlations of body weight and lean body mass were found to be significant with each muscle strength. Our findings presented that obese men had lower muscle strengths for body weight and lean body mass than non-obese men do. This might be the result of two characteristics, inactivity and weak willpower, of obese men. Besides, the 20% fat of threshold of obesity for men proposed by Behnke and Wilmore was reasonable from the viewpoint of the muscle strength because of the differences between group D (18.8% fat) and group E (23.8% fat).

Adipose Tissue↗

PubMed1997

Genetic influences on muscle strength, lean body mass, and bone mineral density: a twin study.

Lean body mass and muscle strength are both associated with bone mineral density (BMD), which is known to be under strong genetic control. In this classical twin study, we examine the size of the genetic component of both muscle strength and lean body mass and to what degree they account for the genetic component of BMD. In all, 706 postmenopausal women were examined; 227 pairs of monozygous (MZ) twins and 126 pairs of dizygous (DZ) twins. Grip strength was measured using a hand-help grip bulb and leg strength using a dynamic leg extensor power rig. Lean body mass and BMD at multiple sites were measured by dual-energy X-ray absorptiometry. BMD correlated with both leg extensor strength (r = 0.16-0.26) and grip strength (r = 0.12-0.21). Lean mass was significantly correlated with BMD at all sites (r = 0.20-0.39). All three muscle variables have a moderate genetic component with heritability estimates of 0.52 for lean body mass, 0.46 for leg extensor strength, and 0.30 for grip strength (all p < 0.05). The genetic component of BMD was not significantly reduced after adjusting for lean mass and muscle strength, with less than 20% of the genetic variance of BMD explained by the muscle variables. In conclusion, these data suggest that the three muscle variables have a modest genetic component, suggesting the potential for clinical intervention and lifestyle modifications. The genetic component to muscle bulk and strength accounts for little of the genetic component to BMD, confirming the rationale for research into bone-specific genes.

Age Factors↗

PubMed2001

Longitudinal muscle strength changes in older adults: influence of muscle mass, physical activity, and health.

The longitudinal changes in isokinetic strength of knee and elbow extensors and flexors, muscle mass, physical activity, and health were examined in 120 subjects initially 46 to 78 years old. Sixty-eight women and 52 men were reexamined after 9.7 +/- 1.1 years. The rates of decline in isokinetic strength averaged 14% per decade for knee extensors and 16% per decade for knee flexors in men and women. Women demonstrated slower rates of decline in elbow extensors and flexors (2% per decade) than men (12% per decade). Older subjects demonstrated a greater rate of decline in strength. In men, longitudinal rates of decline of leg muscle strength were approximately 60% greater than estimates from a cross-sectional analysis in the same population. The change in leg strength was directly related to the change in muscle mass in both men and women, and it was inversely related to the change in medication use in men. Physical activity declined yet was not directly associated with strength changes. Although muscle mass changes influenced the magnitude of the strength changes over time, strength declines in spite of muscle mass maintenance or even gain emphasize the need to explore the contribution of other cellular, neural, or metabolic mediators of strength changes.

Aged↗

PubMed2006

Effect of brisk walking in 1 or 2 daily bouts and moderate resistance training on lower-extremity muscle strength, balance, and walking performance in women who recently went through menopause: a randomized, controlled trial.

BACKGROUND AND PURPOSE: Menopause may induce a phase of rapid decreases in bone mineral density, aerobic fitness, muscle strength, and balance, especially in sedentary women. The purpose of this study was to examine the effects and feasibility of an exercise program of 1 or 2 bouts of walking and resistance training on lower-extremity muscle strength (the force-generating capacity of muscle), balance, and walking performance in women who recently went through menopause. SUBJECTS AND METHODS: The subjects were 134 women who recently went through menopause. The study was a 15-week, randomized, controlled trial with continuous and fractionated exercise groups. The outcomes assessed were lower-extremity muscle strength, balance, and walking time over 2 km. Feasibility was assessed by questionnaires, interviews, and training logs. RESULTS: One hundred twenty-eight women completed the study. Adherence to the study protocol was 92%. Both continuous and fractionated exercise groups improved equally in lower-extremity muscle strength and walking time but not in balance. Almost 70% of the subjects considered the program to be feasible. Two daily walking sessions caused fewer lower-extremity problems than did continuous walking. DISCUSSION AND CONCLUSION: Brisk walking combined with moderate resistance training is feasible and effective. Fractionating the walking into 2 daily sessions is more feasible than continuous walking.

Exercise↗

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↗

PubMed1996

Comparative effects of high- and low-intensity resistance training on thigh muscle strength, fiber area, and tissue composition in elderly women.

The effects of 52 weeks resistance training at one of two exercise intensities on thigh muscle strength, fiber cross-sectional area (CSA), and tissue composition were studied in healthy 65-79-year-old women. Subjects were assigned to either a control (CO), high-intensity (HI) or low-intensity (LO) training group. Exercise regimens consisted of three sets of leg press, knee extension, and knee flexion exercises, 3 days/week, at either 80% of one-repetition maximum (1-RM) for seven repetitions (HI) or 40% of 1-RM for 14 repetitions (LO). Dynamic muscle strength was evaluated by 1-RM, thigh lean tissue mass (LTM), fat mass, and bone mineral density (BMD, g/cm2) by dual energy X-ray absorptiometry, and fiber CSA of vastus lateralis m. by histomorphometry. Muscle strength increased, on average (+/- SEM), by 59.4 +/- 7.9% and 41.5 +/- 7.9% for HI and LO, respectively, compared to 1.3 +/- 4.8% in CO (P = 0.0001). Type I fiber CSA increased over time (P < 0.05) in both exercise groups, with a trend for increased type II area (HI, P = 0.06; LO, P = 0.11). There was no significant effect of either exercise program on thigh tissue composition, except for BMD at the 1/3 site (middle third of the femur), where LO and CO groups experienced a decline (P < 0.05) of -2.2 +/- 0.5% and -1.8 +/- 0.6%, respectively, while HI maintained BMD (+1.0 +/- 1.0%). Both training programs produced significant gains in thigh muscle strength, which were associated with fiber hypertrophy, although these did not translate into appreciable alterations in thigh tissue composition.

Absorptiometry, Photon↗

PubMed2005

The genetic contribution to longitudinal changes in knee structure and muscle strength: a sibpair study.

OBJECTIVE: To estimate the heritability of longitudinal changes in knee cartilage volume, chondral defects, subchondral bone size, and lower limb muscle strength. METHODS: A sibpair design was used. Longitudinal changes in lateral and medial tibial cartilage volume and bone size, as well as progression of chondral defects, were determined on serial magnetic resonance images. Radiographs were obtained and scored for individual features of radiographic osteoarthritis (OA) at baseline. Lower limb muscle strength was measured by dynamometry. Heritability was estimated using the SOLAR software package. RESULTS: A total of 115 subjects (55 men and 60 women, mean age 45 years) from 48 families representing 95 sibling pairs were successfully followed up for a mean of 2.4 years. The adjusted heritability estimates for changes in cartilage volume were 73% for the medial compartment (P < 0.01) and 40% for the lateral compartment (P = 0.10). The adjusted heritability estimates for changes in bone size were 62% for the lateral compartment (P = 0.03) and 20% for the medial compartment (P = 0.22). The adjusted heritability estimate for changes in muscle strength was 64% (P = 0.01). The adjusted heritability estimates for progression of chondral defects were 80% for the lateral compartment (P = 0.06) and 98% for the medial compartment (P = 0.03). These estimates changed little after adjusting for each other and for the predominantly mild radiographic OA, with the exception of progression of chondral defects in the lateral compartment. CONCLUSION: Early longitudinal changes in knee structures of relevance to later OA, such as changes in medial tibial cartilage volume, lateral tibial bone size, progression of chondral defects, and muscle strength, have high heritability, most likely reflecting a strong genetic component and suggesting their potential to be studied in quantitative trait linkage and association analysis.

Adult↗

PubMed2001

Hip Abductor and Knee Extensor Muscle Strength of Children with and without Down Syndrome.

PURPOSE: The purposes of this study were to 1) determine test-retest reliability of hand-held dynamometer measurements of right hip abductor and knee extensor muscle strength in children with Down syndrome (DS), 2) identify differences in isometric muscle strength between children with DS and peers who are developing typically, and 3) determine the relationship between various anthropometric and demographic variables and isometric muscle strength. METHODS: Seventeen children with DS between the ages of seven and 15 years and a comparison group of 17 age- and gender-matched peers who were developing typically participated in the study. A hand-held dynamometer was used to measure peak force during maximal isometric right hip abduction and knee extension at two test sessions approximately one week apart. Peak torque values were calculated by multiplying peak force measurements by the appropriate segment lengths. Anthropometric measurements were obtained, and a questionnaire was used to measure habitual physical activity levels. RESULTS: Test-retest reliability was high, with intraclass correlation coefficients ranging from 0.89 to 0.95. Children with DS had significantly lower mean peak torque values for hip abduction and knee extension than children in the comparison group. Regression analyses indicated that weight, body mass index, height, activity level, and gender were significant predictors of peak torque production for the sample as a whole. CONCLUSIONS: Hand-held dynamometry can be used to obtain reliable measurements of isometric muscle strength in children with DS. Anthropometric characteristics and activity levels may play a role in peak torque production in children with and without DS.

Journal Article↗

PubMed1990

Muscle strength in hyperthyroid patients before and after medical treatment.

Ten hyperthyroid patients were assessed for muscle strength before and after a period of medical treatment that averaged 12 months. The subjects did not change their habitual level of physical activity between the two test occasions. Maximal voluntary isokinetic knee extensor muscle strength was determined during various concentric, eccentric and isometric conditions. Average increases in strength from before to termination of treatment ranged from 25 to 41% for the concentric and isometric tests (P less than 0.01, n = 10), and from 19 to 35% for the eccentric tests (P less than 0.01, n = 6). The present study demonstrates that medical treatment of hyperthyroid patients results in a marked increase in muscle strength.

Adult↗

PubMed1990

Association of muscle strength with functional status of elderly people.

We have studied the association of muscle strength (quadriceps, biceps, handgrip), measured by a portable chair technique, with functional status (Barthel Index, manual dexterity, Mental Test Score, history of falls, fracture, prescribed drugs), in a sample of 92 elderly subjects attending a Local Authority Day Centre and Day Hospital. Anthropometric measurements and hand-grip strength were also measured in 30 young controls. Muscle area, mass and strength were significantly greater in young controls. Elderly men had significantly greater muscle area, mass and strength than elderly women. Muscle strength correlated with several measures of functional status. Using stepwise multiple regression, an independent association of muscle strength with manual dexterity, Barthel Index and receipt of domiciliary services is demonstrated.

Aged↗

PubMed2003

Effects of creatine supplementation and resistance training on muscle strength and weightlifting performance.

Creatine monohydrate has become the supplement of choice for many athletes striving to improve sports performance. Recent data indicate that athletes may not be using creatine as a sports performance booster per se but instead use creatine chronically as a training aid to augment intense resistance training workouts. Although several studies have evaluated the combined effects of creatine supplementation and resistance training on muscle strength and weightlifting performance, these data have not been analyzed collectively. The purpose of this review is to evaluate the effects of creatine supplementation on muscle strength and weightlifting performance when ingested concomitant with resistance training. The effects of gender, interindividual variability, training status, and possible mechanisms of action are discussed. Of the 22 studies reviewed, the average increase in muscle strength (1, 3, or 10 repetition maximum [RM]) following creatine supplementation plus resistance training was 8% greater than the average increase in muscle strength following placebo ingestion during resistance training (20 vs. 12%). Similarly, the average increase in weightlifting performance (maximal repetitions at a given percent of maximal strength) following creatine supplementation plus resistance training was 14% greater than the average increase in weightlifting performance following placebo ingestion during resistance training (26 vs. 12%). The increase in bench press 1RM ranged from 3 to 45%, and the improvement in weightlifting performance in the bench press ranged from 16 to 43%. Thus there is substantial evidence to indicate that creatine supplementation during resistance training is more effective at increasing muscle strength and weightlifting performance than resistance training alone, although the response is highly variable.

Creatine↗

PubMed2004

Trunk muscle strength in relation to balance and functional disability in unihemispheric stroke patients.

OBJECTIVE: To evaluate trunk muscle strength in unihemispheric stroke patients and to assess how it relates to body balance and functional disability in this patient group. DESIGN: This prospective case-comparison study investigated isometric and isokinetic reciprocal trunk flexion and extension strength at angular velocities in 38 unihemispheric stroke patients and 40 healthy volunteers. The Berg balance scale was used to assess balance and stability, and the FIM instrument was used to evaluate functional disability in the patient group. Patients were evaluated as soon as they were able to stand long enough for testing. RESULTS: Peak torque values for trunk flexion and extension were lower in the stroke patients than in the controls. The differences were significant for trunk flexion and for trunk extension. In both groups, peak torque values for trunk flexors were greater than peak torque values for trunk extensors. There was a significant positive correlation between trunk muscle strength and Berg balance scale score at discharge. Trunk muscle strength was not correlated with FIM total score or FIM motor score, but the locomotion-transfers FIM subscore at discharge was positively correlated with trunk muscle torque values, except for isometric extension. CONCLUSION: The findings indicate trunk flexion and extension muscle weakness in unihemispheric stroke patients, which can interfere with balance, stability, and functional disability.

Abdominal Muscles↗

PubMed1996

Correlation of trunk muscle strength with age in children 5 to 18 years old.

OBJECTIVE: To determine the correlation of trunk muscle strength with age in children and the effect of gender on changes in trunk muscle strength. MATERIAL AND METHODS: Strength of the back extensors and back flexors was evaluated in 137 healthy boys and 109 healthy girls who were 5 to 18 years old. Anthropometric determinations of height and weight were done in all study subjects. Maximal back muscle strength was measured with an isometric dynamometer (BID-2000). Standardized positioning techniques were used to allow comparison with the follow-up evaluations. RESULTS: Regression analysis revealed significant increases in trunk strength with increasing age; the strength of the boys began diverging from that of the girls at age 9 to 10 years. Back extensor strength also increased with increasing height and weight, and expected differences were noted between boys and girls. Strength levels ranged from 80 to 774 newtons (18 to 174 lb). Mean back extensor strength in 2-year age intervals ranged from 153 newtons (34.4 lb) in girls 5 to 7 years old to 504 newtons (113.3 lb) in boys 16 to 18 years of age. (Each newton is equal to 0.2248 lb.) CONCLUSION: Results of this study demonstrated that age, height, and weight are all important predictors of trunk strength in children, and the effects of these factors are modulated by gender.

Adolescent↗

PubMed1996

Calf muscle strength in former elite distance runners.

The purpose of this investigation was to examine calf muscle strength and cross-sectional area in 29 middle-aged men (current mean = 48.3 +/- 3.1 years) who had significant differences in their physical activity levels. These men were initially evaluated to determine the physiological requirements for successful distance running in the late 1960s at a time when they were all considered elite distance runners. Based on their training regimens in the interim between testing, subjects were described as highly trained (HI; n = 10), fitness trained (FIT; n = 12), or untrained (UT; n = 7). In addition, an aged-matched sedentary group (CON; n = 7) was tested. Each subject was evaluated for VO2max, plantar flexion calf muscle strength and cross-sectional area (CSA) of the lower leg (gastrocnemius and soleus). Muscle CSA was determined by computed tomography, whereas calf strength measurements were made using a specially designed leg restraint system and an isokinetic dynamometer. There were no significant differences in plantar flexion strength (at 60 and 180 degrees/s) or CSA of the gastrocnemius and soleus muscles among the groups. Calf muscle strength per CSA was also similar at both test velocities for all groups. These data demonstrate that middle-aged distance runners who have continued to run at a relatively high level for 20-25 years have similar calf muscle CSA and strength compared with aged-matched males who run significantly less or not at all.

Biopsy↗

PubMed1986

The relationship between the leg muscle strength and physical capacity in patients with rheumatoid arthritis, with reference to the influence of corticosteroids.

It has been shown that patients with rheumatoid arthritis have weak muscles, especially when they are treated with corticosteroids. Forty-six female patients suffering from rheumatoid arthritis were evaluated with regard to the physical capacity in the lower legs by measuring the walking speed and the climbing performance as correlated to the isokinetic muscle strength of the knee extensors and the plantar flexors. Twenty-six of the patients (average age 60 years, range 34-76) had been treated with corticosteroids. Twenty patients (average age 58 years, range 31-72) had never received corticosteroids. The mean maximal isokinetic muscle strength of the knee extensors in corticosteroid treated patients was 62 +/- 28 Nm (SD) at the angular velocity 30 degrees/s, and the mean maximal isokinetic muscle strength of the plantar flexors in the same group of patients was 33 +/- 21 Nm (SD) at the same angular velocity. Compared to patients with rheumatoid arthritis who had never been treated with corticosteroids the reduction in muscle strength was 37% and 28%, respectively (p less than 0.001 and p less than 0.01). The mean walking speed in patients with corticosteroid treatment was 0.9 m/s, which was a 36% reduction as compared with that found in patients who had not received corticosteroids (p less than 0.01). Half of the patients who had not received corticosteroids were able to climb a 50 cm step, while this was possible in only 16% of the group of corticosteroid-treated patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗