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PubMed2001

Do knee injuries have long-term consequences for isometric and dynamic muscle strength?

To ascertain whether decrements in knee extensor muscle strength persist years after a traumatic ligamentous or meniscal knee injury, with reference to (1) the type of muscle activity, (2) the dominance of injury, and (3) the time since injury, 36 subjects with previous unilateral knee injuries were assessed. Peak voluntary quadriceps muscle strength was measured using the KinCom 500H dynamometer during isometric, concentric (30 degrees.s-1 and 120 degrees.s-1) and eccentric contractions (30.s-1), and the findings for each type of contraction were compared. Significant differences in quadriceps muscle strength were seen between (1) the injured and uninjured limbs during maximal voluntary isometric (P = 0.0003), concentric (P < 0.0001) and eccentric (P < 0.0001) contractions, and (2) the isometric and concentric decrements (P = 0.004), and the isometric and eccentric decrements (P = 0.012) within the same injured limb. The decrements in eccentric strength were significantly greater if they affected the dominant rather than the non-dominant limb (P = 0.0186). No relationship was seen between the time since injury and the degree of isometric or dynamic decrement. Deficits in quadriceps muscle strength remained for a long time after traumatic knee injury, with exercise levels rarely returning to the previously uninjured state. The degree of decrement in muscle strength was dependent upon the type of muscle activity, with concentric and eccentric activity showing greater decrements than those seen with isometric activity. Deficits in the type of activity varied widely in the same individual, and eccentric decrements were significantly worse following dominant knee injuries. Possible explanations for these findings and the implications for rehabilitation following knee injury are discussed.

Adolescent↗

PubMed2001

Relationship between hip muscle imbalance and occurrence of low back pain in collegiate athletes: a prospective study.

OBJECTIVE: To assess whether athletes with strength imbalance of the hip musculature would be more likely to require treatment for low back pain (LBP) over the ensuing year. DESIGN: The study population included 163 National Collegiate Athletic Association Division I college athletes (100 males and 63 females) undergoing preparticipation sports physicals. Institutional review board approval was obtained to acquire and analyze hip muscle strength data. A commercially available dynamometer (Chatillon, Lexington, KY) incorporated into a specially designed anchoring station was used for testing the hip extensors and abductors. The maximum force generated for the hip abductors and extensors was used to calculate a percentage difference between the right and left hip extensors and abductors. Treatment of athletes by the athletic trainers for LBP unrelated to blunt trauma over the ensuing year was recorded. RESULTS: Of all athletes, 5 of 63 females and 8 of 100 males required treatment for LBP. Logistic regression analysis indicated that for female athletes, the percentage difference between the right and left hip extensors was predictive of whether treatment for LBP was required over the ensuing year (P = 0.05). There was no significant association noted for the percentage difference between the right and left hip abductors in females and for the percentage difference between both the right and left hip abductors and right and left hip extensors in males requiring treatment for LBP. CONCLUSIONS: These data support our results from our previous cohort study, adding validity to the concept of hip muscle imbalance being associated with LBP occurrence in female athletes. This research further supports the need for the assessment and treatment of hip muscle imbalance in individuals with LBP.

Female↗

PubMed1995

Isometric muscle strength and muscular endurance in normal persons aged between 17 and 70 years.

Isometric muscle strength was measured in 63 women and 65 men, randomly selected, aged 17-70 years, using Penny & Giles' hand-held dynamometer. Eight muscle groups as well as the hand grip strength were tested bilaterally. The muscular endurance was measured as time to exhaustion in the abductors of the shoulder and the flexors of the hip. Reference values for muscle strength and muscular endurance are given in the age groups 17-18, 20-29, 30-39, 40-49, 50-59 and 60-70 years of age. The mean strength of females was about 65-70% of that of the men, but when the results were related to weight, the differences almost disappeared. Both men and women seem to have the greatest muscle strength at the age of about 17-18. The strength is rather constant up to the age of about 40 years, after which a discrete decline is seen up to about 60, from where the decline is more obvious. Muscular endurance showed great variability between individuals. However, no decrease in endurance was seen in older ages. For both sexes, lower reference limits of endurance, with the methods used, for arm abductors are suggested as being 3 minutes and for hip flexors, 90 seconds.

Adolescent↗

PubMed1992

Training can improve muscle strength and endurance in 78- to 84-yr-old men.

Nine men, 78-84 yr of age, participated in a dynamometer training program 2-3 times/wk, totaling 25 sessions, using voluntary maximal isometric, concentric, and eccentric right knee-extension actions (30 and 180 degrees/s). Measurements of muscle strength with a Kin-Com dynamometer and simultaneous electromyograms (EMG) were performed of both sides before and after the training period. Muscle biopsies were taken from the right vastus lateralis muscle. The total quadriceps cross-sectional area was measured with computerized tomography. Training led to an increase in maximal torque for concentric (10% at 30 degrees/s) and eccentric (13-19%) actions in the trained leg. The EMG activity increased at maximal eccentric activities. The total cross-sectional quadriceps area of the trained leg increased by 3%, but no changes were recorded in muscle fiber areas in these subjects, who already had large mean fiber areas (5.15 microns 2 x 10(3)). The fatigue index measured from 50 consecutive concentric contractions at 180 degrees/s decreased and the citrate synthase activity increased in all but one subject. The results demonstrate that increased neural activation accompanies an increase in muscle strength at least during eccentric action in already rather active elderly men and that muscle endurance may also be improved with training.

Aged↗

PubMed2004

Hemoglobin levels and skeletal muscle: results from the InCHIANTI study.

BACKGROUND: Anemia is associated with reduced physical performance and muscle strength. The aim of the study was to explore whether anemia and hemoglobin levels are associated with differences in quantitative and qualitative measures of muscle and fat. METHODS: The study sample consisted of 909 participants 65 years and older enrolled in the "Invecchiare in Chianti" (InCHIANTI) study, a prospective population-based study of older people aimed at identifying risk factors for late-life disability. All the analyses were performed considering continuous hemoglobin levels as well as the dichotomous anemia variable (defined according to World Health Organization criteria as hemoglobin <12 g/dL in women and <13 g/dL in men). A peripheral quantitative computed tomography (pQCT) scan was performed in all participants to evaluate total, muscular, and fat cross-sectional areas of the calf and relative muscle density. Ankle extension strength was measured using a hand-held dynamometer. Linear regression analyses were used to assess the multivariate relationship of pQCT and skeletal muscle strength measures with hemoglobin levels and anemia after adjustment for demographics, chronic conditions, medication use, and other biological variables. RESULTS: Participants were aged 74.8 +/- 6.8 years. In our sample, 94 participants (10.3%) were anemic. Hemoglobin levels were significantly associated with muscle density (beta = 0.225 [SE, standard error 0.098], p=.02), muscle area/total area ratio (beta=0.778 [SE 0.262], p=.003), fat area/total area ratio (beta=-0.869 [SE 0.225]; p<.001). Skeletal muscle strength and muscle density were highly associated with anemia (beta=-3.266 [SE 1.173], p=.005 and beta=-0.816 [SE 0.374], p=.03, respectively). Results did not change when analyses were rerun in a restricted sample of participants not affected by major medical conditions. CONCLUSION: The present study shows that hemoglobin levels are associated with the parameters of body composition obtained by pQCT, and that decreases in muscular strength measures occur in the presence of anemia.

Aged↗

PubMed1995

Muscle function after endoprosthetic replacement of the proximal tibia. Different techniques for extensor reconstruction in 17 tumor patients.

We analyzed in 17 patients the outcome of various surgical techniques for reconstruction of the extension apparatus after resection of the proximal tibia and tumor prosthesis implantation. The mean follow-up period was 5 (1.5-11) years. Knee extension and flexion strength were measured isokinetically by dynamometer and muscle activities of the vastus medialis, the vastus lateralis and the rectus femoris muscles determined by means of EMG. Muscle function of the operated leg was compared to that of the contralateral extremity by using various surgical techniques: fibula transposition, transposition of the gastrocnemius muscle, and combination technique. The results concerning the operated leg were compared within the 3 groups and the activity and strength of both legs were compared to those of a control group of healthy subjects matched for age and weight. The strength of extensor muscles of the healthy leg was greater than that of the control group in flexion position (60 degrees-90 degrees); the hamstring strength values were within the normal range. The strength of extensor muscles of the operated leg differed between groups II and III at 90 degrees in favor of group II (p < 0.01) and at 60 degrees to 20 degrees (p < 0.001) in favor of group III. Expressed in percentage ranges (nonoperated leg set at 100 percent) the flexor muscles averaged 30 percent, the extensor muscles represented on average 12 percent (9-17 percent) in group I, 9 percent (5-18 percent) in group II and 16 percent (6-26 percent) in group III, depending on the knee angle.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗

PubMed2005

[Evaluation of the surgical results of Achilles tendon ruptures by gait analysis and isokinetic muscle strength measurements].

OBJECTIVES: We evaluated the long-term results of surgical treatment of Achilles tendon ruptures. METHODS: Fifteen male patients (mean age 39.5 years; range 28 to 58 years) underwent surgery for Achilles tendon ruptures. All the ruptures but one occurred during sport recreation. Eleven patients were treated within the first week of trauma. After surgery, a cast was applied for four weeks, after which it was switched to a polyethylene splint that did not allow dorsiflexion. Partial weight bearing was allowed in the fourth postoperative week. Subjective and objective evaluations were made according to the system by Thermann et al. Muscle strength was measured by an isokinetic dynamometer and gait analysis was performed. Data from the healthy sides were used for comparisons. The mean follow-up was 16.8 months (range 8 to 48 months). RESULTS: Seven patients (46.7%) had no pain, while six patients (40%), one patient (6.7%), and one patient complained of pain during heavy, medium, and light sports activities, respectively. Muscle strength did not decrease in nine patients (60%). Seven patients (46.7%) returned to preinjury activity levels. Twelve patients (80%) evaluated the outcome as very good or good. The mean muscle atrophy on the affected side was 0.43 cm. The overall results were very good or good in nine patients (60%), moderate in four patients (26.7%), and poor in two patients (13.3%). One patient had superficial infection and delayed healing. Isokinetic measurements showed decreased peak torque, and increased total work. By gait analysis, no significant relationship was found between the dorsiflexion and plantar flexion difference and forefoot ground reaction forces. CONCLUSION: Early surgical treatment of Achilles tendon ruptures followed by a shorter immobilization period is associated with satisfactory results, and in the long-term, with a higher rate of patient satisfaction.

Achilles Tendon↗

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↗

PubMed1988

Isokinetic investigation of knee extensors and knee flexors in young French soccer players.

The knee extensor and knee flexor muscle groups in three groups of young soccer players were tested with a Cybex II isokinetic dynamometer and compared with adults. Muscle strength increased with age. The largest gain was observed in young players aged 16-17 years whose quadriceps was the most modified muscle group giving the lowest H/Q ratio. Analysis of the regression equations obtained for torque values at 30 degrees s-1 and 180 degrees s-1 revealed that there were two distinct groups: under 16 and over 16. After reaching 16 years of age, the increase in muscle strength is greater at low velocity than at high velocity.

Adolescent↗

PubMed1994

Potentiation of concentric plantar flexion torque following eccentric and isometric muscle actions.

In a stretch-shortening cycle (SSC) the concentric muscle action is enhanced by a preceding eccentric muscle action. The hypothesis of the present study is that a preceding isometric action can also have an effect on a following concentric action, but to a lesser degree. A KINetic-COMmunicator II dynamometer was used to test muscle strength of the plantar flexion of the right foot in 20 healthy women. Maximal voluntary torque measurements were made at different angular velocities (120 degrees s-1 and 240 degrees s-1) and the range of motion of the ankle joint was 78-125 degrees. The assessment was based on concentric torque output and EMG recording from the gastrocnemius muscle under three different types of testing conditions (concentric actions with and without preceding eccentric or isometric actions, all with maximal efforts). The results showed that preceding muscle actions led to greater concentric torque output (P < 0.01) between 90 and 99 degrees plantar flexion. However, the increase in the concentric action was significantly (P < 0.01) larger with eccentric than with isometric preceding action, regardless of velocity. The EMG activity of the concentric action showed unchanged or lower values when preceded by a muscle action. In this model our conclusion is that the main reason for larger concentric torque values after a preceding muscle action is that time is sufficient for maximal muscle tension development; in addition, elastic energy is stored, particularly during the preceding eccentric action. Our results show that the effect of preceding muscle actions should be taken into account when measuring isokinetic muscle strength at relatively small angular movements.

Adolescent↗

PubMedDate not supplied

Partial rupture of the patellar ligament. Results after operative treatment.

Partial rupture of the patellar ligament, also known as jumper's knee, is defined as a repetitive overload lesion at the bone-ligament junction at the lower patellar pole. It is found mainly in athletes and is caused either by microruptures or partial macroruptures of the proximal part of the ligament. The abnormal anatomical lesion is focal degeneration, microruptures and macroruptures, and devitalized tissue at the insertion of the patellar ligament. Proliferation and neovascularization are often found, as well as degeneration and incomplete tissue healing. Surgical treatment is indicated only if a prolonged and well-supervised conservative treatment program fails. We operated on 78 patients with jumper's knee, by carefully removing the abnormal tissue from the ligament. At follow-up examination, 71 of 78 patients had excellent or good functional results and complete resumption of sports activities. Objective measurements of thigh muscle strength using a Cybex II dynamometer correlated with the functional results at a low angular velocity.

Adolescent↗

PubMed2000

Portable dynamometer anchoring station for measuring strength of the hip extensors and abductors.

OBJECTIVE: To assess the reliability of a specially designed dynamometer anchoring station in the measurement of hip muscle strength. DESIGN: Prospective study using test-retest design. SETTING: Outpatient clinic setting. PARTICIPANTS: Ten subjects, ages 25 to 35yrs. MAIN OUTCOME MEASURES: Using the apparatus, three consecutive measures were recorded for hip abduction and extension by an inexperienced examiner. Two weeks later, the same subjects were retested, with the evaluator blinded to the initial results. In both the test and retest, average and maximal values of strength were calculated for each muscle. Reliability of the device was assessed by computing the intraclass correlation coefficients and coefficients of variation (CVs). RESULTS: Intraclass correlation coefficients ranged from .94 to .98. The average CV for the maximal and average abduction strength had values of 4.77% and 4%, respectively. The maximal and average extension strength had average CV values of 8.06% and 7.83%, respectively. CONCLUSION: This specially designed dynamometer anchoring station has been found to be highly reliable in the measurement of hip girdle strength and has the advantage of easy adjustability and portability for large-scale screenings. This device enhances the reliability of the dynamometer, which may be subject to considerable variability when applied by hand to the powerful hip girdle musculature.

Adult↗

PubMed1999

The relation between bone mineral density, insulin-like growth factor I, lipoprotein (a), body composition, and muscle strength in adolescent males.

Osteoporosis is the most common metabolic bone disease. A low peak bone mass is regarded a risk factor for osteoporosis. Heredity, physical activity, and nutrition are regarded important measures for the observed variance in peak bone mass. Lp(a) lipoprotein is a well-known risk factor for atherosclerosis. Serum insulin-like growth factor I (IGF-I) has been found to be increased in males with early cardiovascular disease. In this study, we evaluated the association between bone mass, body constitution, muscle strength, Lp(a), and IGF-I in 47 Caucasian male adolescents (mean age, 16.9 yr). Bone mineral density (BMD) and body composition were measured by dual x-ray absorptiometry, muscle strength of thigh using an isokinetic dynamometer, IGF-I by RIA, and Lp(a) by enzyme-linked immunosorbent assay. IGF-I was only associated with Lp(a) (r = 0.38, P < 0.01). Lp(a) was related to total body (r = 0.40, P < 0.01), skull (r = 0.45, P < 0.01), and femoral neck BMD (r = 0.44, P < 0.01). Lp(a) was also related to fat mass (r = 0.34, P < 0.05) and muscle strength (r = 0.30-0.42, P < 0.05). After multiple regression and principal component (PC) analysis, the so-called PC body size (weight, fat mass, lean body mass, and muscle strength) was the most significant predictor of BMD (beta = 0.28-0.51, P < 0.05-0.01), followed by the so-called PC physical activity (beta = 0.28-0.38, P < 0.05-0.01, weight-bearing locations). However, the PC analysis confirmed that Lp(a) was an independent predictor of total body, skull, and femoral neck BMD (beta = 0.33-0.36, P < 0.01). The present investigation confirms that BMD, body size, and muscle strength are closely related and that the level of physical activity is a major determinant of BMD. However, the positive relation of Lp(a), a major risk factor for cardiovascular disease, to BMD has not previously been described. The importance of this observation has to be further investigated.

Adolescent↗

PubMed1987

Upper extremity strength deficits in hemiplegic stroke patients: relationship between admission and discharge assessment and time since onset.

This study describes objective upper extremity strength deficits in hemiplegic stroke patients on initial and discharge assessment, and the relationship between these deficits and the time since onset. The static strength of ten different muscle groups had been measured bilaterally in patients (n = 24 to 58, depending on the muscle group), using a hand-held dynamometer. Strength deficits were calculated in relation to the nonparetic side of the body. Zero order correlations were calculated for strength deficit and time variables. Only the relationships between the strength deficits of the initial and discharge assessments were significant (p less than 0.01). These results suggest that the strength deficits of an initial assessment are the best predictors of strength deficits at discharge. This finding has implications for clinicians in clinical decision-making and in addressing patient expectations.

Aged↗

PubMed2002

Skeletal muscle damage and recovery.

Muscular strength is essential for recovery after an acute illness. Disuse atrophy of muscle begins within 4 hours of the start of bed rest resulting in decreases in muscle mass, muscle cell diameter, and the number of muscle fibers. Strenuous exercise of atrophic muscle can lead to muscle damage including sarcolemmal disruption, distortion of the myofibrils' contractile components, and cytoskeletal damage. Assessment of skeletal muscle for disuse atrophy is done clinically at the bedside through strength assessment. Examination of the muscle itself can be conducted through the use of nuclear magnetic resonance imaging, whereas muscle strength can be quantified with a computerized dynamometer. Biochemical markers, including creatine kinase and troponin, also are available for the assessment of skeletal muscle damage. Activity management in the critical care environment focuses on an individualized plan, developed in cooperation with the recovering patient, with the goal of preserving and improving atrophic skeletal muscle.

Disease Management↗

PubMedDate not supplied

[Evaluation of force and mobility following the open Bankart operation for treatment of recurrent dislocation of the shoulder].

AIM: The purpose of this study was to evaluate the isokinetic muscle strength, range of motion and radiological signs of arthopathy of recurrent dislocation of the shoulder after an open Bankart procedure. METHODS: This retrospective study is based on the analysis of isokinetic muscle strength, range of motion, function and arthropathy of the shoulders of 81 patients at an average of 2.3 years (range 1-4 years) after a Bankart procedure. Isokinetic muscle strength testing was performed using the Cybex 6000 dynamometer. RESULTS: Clinical testing at follow-up revealed no significant loss of range of motion of the operated shoulder compared to the healthy contralateral shoulder. The deficit of muscle strength (average peak torque, total work, total power) of the involved side averaged 10 % of the not-involved side and was not statistically different. Follow-up radiographs demonstrated an increase of arthropathy in 35 % of the shoulders after the Bankart procedure. CONCLUSION: At an average follow-up of 2.3 years after an open Bankart repair for treatment of recurrent dislocation of the shoulder we found no significant difference between the operated shoulder and the healthy contralateral side concerning range of motion and isokinetic muscle strength. From that we conclude that the Bankart procedure offers an excellent clinical outcome combined with a low degree of morbidity.

Adolescent↗

PubMed2003

Sporadic inclusion body myositis: pilot study on the effects of a home exercise program on muscle function, histopathology and inflammatory reaction.

OBJECTIVE: To evaluate the safety and effect of a home training program on muscle function in 7 patients with sporadic inclusion body myositis. DESIGN: The patients performed exercise 5 days a week over a 12-week period. METHODS: Safety was assessed by clinical examination, repeated muscle biopsies and serum levels of creatine kinase. Muscle strength was evaluated by clinical examination, dynamic dynamometer and by a functional index in myositis. RESULTS: Strength was not significantly improved after the exercise, however none of the patients deteriorated concerning muscle function. The histopathology was unchanged and there were no signs of increased muscle inflammation or of expression of cytokines and adhesion molecules in the muscle biopsies. Creatine kinase levels were unchanged. A significant decrease was found in the areas that were positively stained for EN-4 (a marker for endothelial cells) in the muscle biopsies after training. CONCLUSION: The home exercise program was considered as not harmful to the muscles regarding muscle inflammation and function. Exercise may prevent loss of muscle strength due to disease and/or inactivity.

Aged↗

PubMed1996

[Long-term maintenance therapy of multifocal motor neuropathy by weekly administration of human immunoglobulin].

High-dose intravenous immunoglobulin therapy for multifocal motor neuropathy (MMN) exhibits a beneficial, but temporary effect in most cases. We experienced a patient with MMN having a high titer of anti-GM1 ganglioside antibody. He was weekly administered human immunoglobulin, and his muscle strength was successfully improved and maintained at the improved level after high-dose human immunoglobulin infusion. The pattern of improvement and maintenance by weekly administration of human immunoglobulin was variable among the muscles; e.g. only a minimal improvement was observed in the most severely involved brachioradial muscles. Successive measurements with a hand-held dynamometer revealed in detail the changes in the strength of each muscle during treatment. Anti-GM1 ganglioside antibody titers did not significantly change during the treatment, but a slight improvement in motor conduction amplitudes and velocities was observed in mildly affected nerves. Our findings suggest that weekly administration of human immunoglobulin is a safe and effective therapy for MMN and that the anti-GM1 ganglioside antibody titer may not be a good indicator for this therapy.

Adult↗