Isokinetic and isometric muscle strength in a healthy population with special reference to age and gender.

AIM: Muscle strength is an excellent indicator of general health when based on reliable measurements. Muscle strength data for a healthy population are rare or non-existent. The aim of the present study was to measure a set of normal values for isometric and isokinetic muscle strength for all the major joint movements of the body and, from these data, to create a basis for comparison of the muscle strength of an individual with the expected value in a normal population. METHODS: A randomly selected group, aged 20-80 years, from the Copenhagen City Heart Study were studied. The group was subgrouped according to age and gender. Isometric and isokinetic muscle strength was measured in each subject across the main joints in the body. A statistical model was developed that encompassed the three main muscle groups: upper limbs, trunk and lower limbs. RESULTS: Muscle strength in healthy men decreases in a linear fashion from the age of 25 years down to between 54% and 89% at the age of 75 years, and seems not highly dependent on any other parameter than age. For women, the muscle strength is dependent on weight and is only related to age from around 40 years of age. The decrease in muscle strength from the age around 40 to 75 years is 48-92%. For most muscle groups, men are 1.5-2 times stronger than women, with the oldest men having strength similar to that observed among the youngest women. CONCLUSION: We developed a model to compare the isometric and isokinetic muscle strength of all the major joint movements of an individual with values for a healthy man or woman at any age in the range of 20-80 years. In all age groups, women have lower muscle strength than men. Men's muscle strength declines with age, while women's muscle strength declines from the age of 41 years.

Maximal isometric strength of the cervical musculature in 100 healthy volunteers.

STUDY DESIGN: A descriptive study involving maximal isometric strength measurements of the cervical musculature. OBJECTIVES: To determine the maximal isometric strength of the flexors and extensors and of the cervical musculature in 100 healthy volunteers (50 men and 50 women). SUMMARY OF BACKGROUND DATA: The literature contains only a few descriptive studies pertaining to strength levels of the cervical musculature. These studies include small subject populations, and measurement methods have demonstrated weak reliability. METHODS: Testing was carried out using strain-gauge technology on a neck muscle training apparatus. RESULTS: A reliability study demonstrated acceptable intraday and day-to-day values. Maximal isometric strength was approximately 20% to 25% higher in male subjects than female subjects in both flexion and extension from the third to the sixth decades. In the seventh decade, the women's strength levels surpassed values for men in both flexion and extension. Extension-flexion ratios were approximately 1.7 to 1 in both the men and women participants. The men demonstrated a significant decrease in maximal isometric strength with increasing age in both flexion and extension, whereas the women were able to maintain strength values in the ages tested. CONCLUSIONS: Men and women demonstrate impressive levels of muscular strength in the flexors and extensors of the cervical spine and can maintain these values until the seventh decade of life. Successful rehabilitation of the cervical musculature will require considerable resistance for sufficient stimulation of the cervical musculature.

Paraplegia, a severe complication to epidural analgesia.

We report four cases where continuous epidural analgesia resulted in epidural abscesses (EA) causing spinal cord damage and paraplegia. The first symptom of EA was intense back pain, which developed 0-20 days after removal of the epidural catheter. The diagnosis of EA was not made prior to the development of severe neurologic disturbances in any of the patients. In all cases there was a time lag of 2-4 days between the first symptoms and institution of the appropriate treatment.

The twitch interpolation technique for the estimation of true quadriceps muscle strength.

The aim of this study was to examine the reliability of the twitch interpolation technique when used to estimate the true isometric knee extensor muscle strength. This included an examination of whether submaximal activation causes any bias in the estimation of the true muscle strength and an examination of the precision of the method. Twenty healthy subjects completed three contraction series, in which the subjects were told to perform as if their voluntary strength was 60%, 80% or 100% of that determined by a maximal voluntary contraction (MVC). Electrical muscle stimulations were given at each of five different contraction levels in each series. At torque levels above 25% of MVC the relationship between torque and twitch size could be approximated to be linear. The true muscle strength (TMS) could therefore be estimated using linear regression of the twitch-torque relationship to the torque point of no twitch in each of the three series, termed TMS60, TMS80 and TMS100. The TMS80 was slightly lower (P < 0.01), median 94% (IQ range 87-101%) of the TMS100. The TMS60 was median 99% (IQ range 83-125%) (NS) of TMS100, but a few severe outliers were observed. In conclusion, we found the reliability of the method acceptable for many research purposes, if series with estimated central activation of below 40-50% were excluded. The only moderate precision and the slightly lower estimations in subjects applying submaximal does, however, limit its usefulness.

Muscle strength, working capacity and effort in patients with fibromyalgia.

The objective of the study was to evaluate the physical capacity and effort in patients with fibromyalgia. Muscle strength and the coefficient of variation of the strength measurements of 181 female fibromyalgia patients and 126 healthy females were compared. These measurements and ergometer exercise capacity, work status and psychometric scoring (SCL-90-R) were correlated. The fibromyalgia patients exhibited significant reduction in voluntary muscle strength of the knee and elbow, flexors and extensors in the order of 20-30%. However, the coefficient of variation was higher among patients, thus indicating lower effort. The physical performance during an ergometer test corresponded to a maximal oxygen consumption of 21 ml/kg-1 x min-1. The maximal increase in heart rate was only 63% (44-90%) of the predicted increase. Degree of effort or physical capacity did not correlate to psychometric scores. Work status was related to psychometric scoring, but not to physical capacity or effort. In conclusion, we found a low degree of effort but near normal physical capacity in the fibromyalgia patients.

The twitch interpolation technique for study of fatigue of human quadriceps muscle.

The aim of the study was to examine if the twitch interpolation technique could be used to objectively measure fatigue in the quadriceps muscle in subjects performing submaximally. The 'true' maximum isometric quadriceps torque was determined in 21 healthy subject using the twitch interpolation technique. Then an endurance test was performed in which the subjects made repeated isometric contractions at 50% of the 'true' maximum torque for 4 s, separated by 6 s rest periods. During the test, the force response to single electrical stimulation (twitch amplitude) was measured at 50% and 25% of the estimated maximum torque. In 10 subjects, the test was repeated 2-4 weeks later. Twitch amplitudes at 50% of maximum torque declined exponentially with time in 20 of 21 subjects. The distribution of the exponential rate constant was skewed with a mean of 4.6 h-1 and range of 0.3-21.5 h-1. After logarithmical transformation, the distribution of the exponential rate constant fitted closely to a normal distribution, and the inter-individual variation was SD = 1.15 compared to an intra-individual variation of 0.29. The coefficient of correlation for repeated determination was 0.91 (P < 0.001, n = 10). In conclusion, the twitch technique can be used for objectively measuring fatigue of the quadriceps muscle.

Muscle strength, voluntary activation and cross-sectional muscle area in patients with fibromyalgia.

The objectives were to determine whether the low muscle strength in fibromyalgia is due to lack of exertion and to determine the relation between strength and muscle area. Secondarily we examined the voluntary muscle strength of the different muscles of the leg. The twitch interpolation technique was used to estimate the degree of central activation and the 'true' quadriceps muscle strength. Muscle cross-sectional area was determined with magnetic resonance imaging (MRI). The estimated 'true' muscle strength was 91 Nm (S.D. = 34 Nm) in 15 fibromyalgia patients compared with 125 Nm (28 Nm) in 14 healthy controls (P < 0.02). The 'true' strength divided by the sum of the maximal areas of the four bellies of the quadriceps muscle was lower, being 1.56 Nm/cm2 (0.32 Nm/cm2) in fibromyalgia patients compared with 2.11 Nm/cm2 (0.39 Nm/cm2) in the controls (P < 0.001). The voluntary muscle strength of the flexor muscles of the knee and of the plantar flexors of the ankle was markedly reduced in patients, but no significant differences could be observed in the strength of the dorsal flexors of the ankle. In conclusion, a reduction of the estimated 'true' quadriceps muscle strength per unit area of about 35% was found in fibromyalgia patients.

Muscle strength, voluntary activation, twitch properties, and endurance in patients with fibromyalgia.

Previous studies have shown decreased voluntary muscle strength and endurance in patients with fibromyalgia. The aim of this study was to determine to what extent this is due to lack of exertion. The twitch interpolation technique was used to determine the degree of central activation and estimate the "true" quadriceps muscle strength in patients with fibromyalgia and age and sex matched controls. Subjects hereafter performed an endurance test consisting of repetitive contractions at 50% of estimated "true" muscle strength of four seconds duration followed by a six second rest until exhaustion, or maximally for 40 minutes. Twitch decline and increases in mean rectified EMG were used as objective markers of fatigue. The estimated "true" muscle strength was 82 (SD 26) Nm in 20 patients with fibromyalgia compared with 133 Nm (SD 28) Nm in the 21 controls (p < 0.001). The "true" muscle strength per cm2 midthigh cross sectional area was lower 0.50 (SD 0.15) Nm/cm2 in the patients compared with 0.74 (SD 0.15) Nm/cm2 in the controls (p < 0.001). The decline over time in twitch sizes was similar in the two groups. The mean rectified EMG signal at a fixed force level of 50% of "true" muscle strength increased similarly in the two groups. Relaxation rates and contraction rates also increased equally in the two groups. In conclusion, a reduction of the estimated muscle strength per area unit of about 35% was found in the patients with fibromyalgia. This might be secondary to physical inactivity or neuroendocrine factors. No differences in changes in the neurophysiological indices associated with fatigue were found between the two groups.

Low power Ga-Al-As laser treatment of painful osteoarthritis of the knee. A double-blind placebo-controlled study.

The aim of this double-blind study was to evaluate the effect of low power Ga-Al-As laser treatment on chronic pain related to osteoarthritis of the knee with periarticular tender points. Twenty-nine out-patients with uni- or bilateral osteoarthritis of the knee were included and randomly assigned to treatment with either laser or placebo laser. Fourteen patients received active laser treatment and all patients included completed the study. The effect variables were daily levels of pain, analgesic requirements, palpation tenderness and isokinetic quadriceps strength. Each patient participated in the study for 9 weeks and registered daily level of pain and consumption of analgesics. In weeks 4, 5 and 6 the patients received a total of nine treatments, each of 15 min and administered to periarticular tender points. The dose per treatment was 22.5 joule. No significant differences in any of the effect variables were found between the two groups before, during or after treatment. With regard to the patients' overall assessment there was a clearly demonstrable positive effect of treatment in both groups. This is likely to be due to a placebo effect.

Biochemical changes in relation to a maximal exercise test in patients with fibromyalgia.

Patients with fibromyalgia often complain of fatigue and pain during exercise and of worsening of pain days after exercise. The aim of the study described here was to determine if abnormal changes in potassium or lactate could be observed during an exercise test in fibromyalgia. Whether an abnormal incline in plasma creatine kinase or myoglobin could be observed days after the test was studied also. Fifteen female fibromyalgia patients and 15 age- and sex-matched controls performed a stepwise incremental maximal bicycle-ergometer test. Blood samples were collected from a catheter in a cubital vein. The changes in heart rate, potassium levels, and haematocrit during the exercise test were similar in the two groups. The maximal obtained lactate concentration was 4.2 mmol l-1 (3.5-5.6) in the patients as compared to 4.9 mmol l-1 (3.9-5.9) in the controls (NS). The estimated anaerobic threshold of 2 mmol l-1 was reached at a heart rate of 124 min-1 in the patients with fibromyalgia as compared to 140 min-1 in the controls (P = 0.02). In relation to workload, the patients scored higher on a Borg scale for perceived exertion during exercise, but if the Borg score was related to lactate no significant difference was found. The patients reported 86% and 79% of maximal pain in the thighs on the visual analogue scale 1 and 2 days after the test, but the creatine kinase and myoglobin concentrations were not increased.

A four-year follow-up study in fibromyalgia. Relationship to chronic fatigue syndrome.

The primary objectives of this study were to examine to what extent fibromyalgia patients later on developed presumpted causative somatic diseases and to examine symptoms and muscle strength some years after the diagnosis of fibromyalgia was established. A secondary objective was to describe the overlap between fibromyalgia and chronic fatigue syndrome. Only in two of 91 the muscle pain was found to be caused by another somatic disease during the median 4 year follow-up period. In one of the 83 attending subjects a somatic disease associated with muscle symptoms was established at the follow-up visit. 60 out of 83 reported increased pain, 8 reported improvement of pain. The 83 subjects showed no significant fall in muscle strength during the follow-up period. The majority reported severe fatigue but only one fifth fulfilled the proposed chronic fatigue syndrome criteria.

Fibromyalgia in the adult Danish population: I. A prevalence study.

Epidemiologic studies of fibromyalgia have so far been based on rheumatologic and general practice settings, which are poor proxies for the underlying population. The study is based on a national health interview survey carried out by the Danish Institute for Clinical Epidemiology in 1990/91 on approx. 6000 randomly selected Danish citizens. For this study 1219 subjects from the eastern part of Denmark aged 18 to 79 years were asked about widespread muscle pain. One-hundred-and-twenty-three persons fulfilled the screening criteria. Clinical examination could be performed on 65 persons (53%). Eight subjects, all female, met the 1990 American College of Rheumatism criteria for fibromyalgia. Dropouts were regarded as not having fibromyalgia. The prevalence of fibromyalgia in the Danish population between 18 and 79 years of age was found to be a minimum estimate of 0.66% (95% confidence limits 0.28%-1.29%).

Fibromyalgia in the adult Danish population: II. A study of clinical features.

Clinical characteristics of fibromyalgia have so far been based mainly on patients identified in rheumatologic settings. This paper offers the clinical findings in fibromyalgia based on a national health interview survey, in which 123 persons fulfilled preset criteria for widespread pain. Clinical examination could be performed on 65 subjects (53%) and included physical examination, tender point palpation by two blinded trained physicians, blood sample analysis, measurement of dynamic muscular strength and a detailed self-administered questionnaire. Significantly more subjective swelling, fatigue, headache, difficulty in stair-climbing, and poorer self-evaluated health with more tender points was found. Contrary to that which was expected, fibromyalgia subjects did not suffer from sleep disturbances, irritable bowels or morning stiffness. Our findings indicate that clinical characteristics of fibromyalgia in the general population may differ from those found in rheumatological settings.

Twitch interpolation technique in testing of maximal muscle strength: influence of potentiation, force level, stimulus intensity and preload.

The aim was to study the methodological aspects of the muscle twitch interpolation technique in estimating the maximal force of contraction in the quadriceps muscle utilizing commercial muscle testing equipment. Six healthy subjects participated in seven sets of experiments testing the effects on twitch size of potentiation, time lag after potentiation, magnitude of voluntary force, stimulus amplitude, stimulus duration, angle of the knee, and angle of the hip. In addition, the consequences of submaximal potentiation on the estimation of maximal force from twitch sizes were studied in five healthy subjects. We found an increase in twitch size with increasing levels of potentiation and twitch size decreased exponentially following potentiation. We found a curvilinear relationship between twitch size and voluntary force, and these properties were more obvious when the stimulation intensity of the preload was reduced. The relationship between twitch size and force was only linear, for force levels greater than 25% of maximum. It was concluded that to achieve an accurate estimate of true maximal force of muscle contraction, it would be necessary for the subject to be able to perform at least 75% of the true maximal force.

[Duplication in a medical department of tests previously performed in a primary sector]. / Gentagelse på medicinsk afdeling af undersøgelser der i forvejen er foretaget på patienterne i primaersektoren.

The aim of this study was to evaluate whether an insufficient flow of information from the primary to the secondary sector was the cause of unnecessary duplications of investigations. From practitioners of 202 patients admitted to a medical department information about paraclinical examinations during the previous year was obtained. In all 111 general practitioners participated. An average of 3.0 blood analyses and 0.9 other investigations were carried out on each patient. 44% of the patients were not investigated at all. An average of 1.9 blood analyses and 0.2 other investigations on each patient were repeated. 22% of the repetitions in both cases were due to insufficient communication between the practitioner and the hospital. These figures seem low and insufficient communication between the primary and the secondary sector appears to be a minor problem.

Comparison of pharmacodynamic effects and plasma levels of oral and rectal ergotamine.

Plasma levels and the vasoconstrictive effect of 1 mg ergotamine tartrate given as tablets or suppositories were compared. In a crossover study, eight male volunteers received tablets or suppositories containing ergotamine in a drug combination (Anervan) and, as a control, suppositories without ergotamine. Blood sampling and measurement of toe-arm systolic gradients with a strain-gauge technique were done for up to 6 h and again after 24 h and 48 h. Only 29 of 160 blood samples contained detectable (greater than 0.1 ng/ml) amounts of ergotamine, and kinetic comparison could not be performed. Only ergotamine-containing suppositories caused a significant (p less than 0.008) decrease in toe-arm systolic gradient which was significantly different (p less than 0.003) from the effects of ergotamine tablets and control suppositories. Rectal ergotamine is thus more biologically active, for the factor used, than oral ergotamine. We suggest that a rectal dose of 1 mg ergotamine tartrate should be tried as the initial dose in the treatment of migraine attacks.