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PubMed1996

Physiotherapy in knee osteoarthrosis: effect on pain and walking.

Patients with knee osteoarthrosis are often referred for physiotherapy and many different types of treatment are given. The value of many of these treatments has been questioned. This study was intended to evaluate the effect of commonly used physiotherapy treatments in a training programme on patients with medial knee osteoarthrosis, scheduled for surgery. The results from this study also provide useful data for further evaluation of different physiotherapy treatments to this patient group. Thirty-four patients were randomised to physiotherapy three times a week for 5 weeks and the other 34 received no treatment. The training programme is described in detail. The patients were evaluated by clinical examination, step test, gait analysis and isokinetic measurements of thigh muscle strength before and after treatment. The patients in the treatment group experienced a feeling of overall improvement in the knee and the ability to descend steps improved when compared to the control group. There were no significant differences in gait, range of motion or isokinetic measurements of muscle strength between the groups. We conclude that physiotherapy as given here made our patients feel better and their ability to descend stairs improved. These improvements are beneficial to the patients and support the positive effects of exercises and activity. Whilst the objective improvements were small, suggesting that this treatment may not be justified, patients in the treatment group believed that they were improved.

Aged↗
PubMed1993

Sarcomere shortening velocity in pressure overload hypertrophied rabbit right ventricular myocardium at physiological sarcomere lengths.

Earlier we noted the importance of internal loads for sarcomere shortening in heart muscle. Internal loading may change with hypertrophy and influence sarcomere shortening velocity. Therefore, we force clamped trabeculae from normal rabbit right ventricles and those hypertrophied due to pulmonary artery constriction. Diffraction of a laser (lambda = 632.8 nm) by a trabecula was used to measure sarcomere length (SL) in isotonic twitches. Resting SL was set at 2.36 +/- 0.17 microns in the normal (n = 5) and 2.23 +/- 0.08 microns in the hypertrophied (n = 5) (+/- S.E.M.) muscles. The relationship of total stress with log10 sarcomere shortening velocity was linear. In the normals, log(SL/s) = 0.39-1.32 (P(total)/P(isom)), and in hypertrophy, log(SL/s) = -0.16-0.57 (P(total)/P(isom)). SL/s is sarcomere shortening velocity in microns/s divided by SL at the onset of constant force. P(total) is isotonic plus resting stress and P(isom) is peak total isometric stress. The hypertrophy (P(total)/P(isom))-(SL/s) relationship is depressed below normal at low loads (P < 0.001). Estimated unloaded SL/s in the normals was 2.47 and 0.69 in hypertrophy. Paired stimulation had no effect on normal SL/s. In hypertrophy, paired stimulation increased SL/s at low loads to normal levels. Thus, depressed sarcomere shortening velocity at low loads in hypertrophy at physiological sarcomere lengths disappeared when myoplasmic [Ca2+] increased. The results suggested that internal loading was greater than normal during shortening of hypertrophied myocardium. Increased myoplasmic [Ca2+] increased the number of crossbridges and reduced the load per crossbridge. This was a likely mechanism for the increase of sarcomere shortening velocity to normal levels.

Animals↗
PubMed1993

Calcium modulates the influence of length changes on the myofibrillar adenosine triphosphatase activity in rat skinned cardiac trabeculae.

The relationship between adenosine triphosphate (ATP) turnover and muscle performance was investigated in skinned cardiac trabeculae of the rat at different [Ca2+] and two different sarcomere lengths (1.8 microns and 2.2 microns) at 20 degrees C. ATP turnover was measured photometrically by enzymatic coupling of the regeneration of ATP to the oxidation of reduced nicotinamide adenine dinucleotide. The trabeculae were studied under isometric conditions and when the length was altered repetitively at a frequency of 23 Hz, with a square wave, by 5% of the initial length. The isometric ATPase activity amounted to 0.48 mM/s. Isometric ATP turnover and force were proportional at different [Ca2+]. During length changes at maximal activation (pCa 4.27) and 2.2 microns sarcomere length, ATPase activity increased to up to 162% whereas at low [Ca2+], ATPase activity decreased with respect to the isometric value at that pCa. At pCa 5.5, ATPase activity was reduced to 33%. These results indicate that during the length changes the apparent cross-bridge detachment rate is increased and the apparent attachment rate is decreased. The findings suggest that the Fenn effect, i.e. the increase in energy turnover above the isometric value during shortening, is present in cardiac trabeculae at high levels of activation, but is absent or reversed at lower levels of activity.

Adenosine Triphosphatases↗
PubMed1990

Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women.

Twenty-four women completed a 20-week heavy-resistance weight training program for the lower extremity. Workouts were twice a week and consisted of warm-up exercises followed by three sets each of full squats, vertical leg presses, leg extensions, and leg curls. All exercises were performed to failure using 6-8 RM (repetition maximum). Weight training caused a significant increase in maximal isotonic strength (1 RM) for each exercise. After training, there was a decrease in body fat percentage (p less than 0.05), and an increase in lean body mass (p less than 0.05) with no overall change in thigh girth. Biopsies were obtained before and after training from the superficial portion of the vastus lateralis muscle. Sections were prepared for histological and histochemical examination. Six fiber types (I, IC, IIC, IIA, IIAB, and IIB) were distinguished following routine myofibrillar adenosine triphosphatase histochemistry. Areas were determined for fiber types I, IIA, and IIAB + IIB. The heavy-resistance training resulted in significant hypertrophy of all three groups: I (15%), IIA (45%), and IIAB + IIB (57%). These data are similar to those in men and suggest considerable hypertrophy of all major fiber types is also possible in women if exercise intensity and duration are sufficient. In addition, the training resulted in a significant decrease in the percentage of IIB with a concomitant increase in IIA fibers, suggesting that strength training may lead to fiber conversions.

Adult↗
PubMed1980

Extracellular K+ concentration and K+ balance of the gastrocnemius muscle of the dog during exercise.

Exercise-induced changes of the extracellular and the venous K+ concentrations ([K+]e, [K+]ven) were measured continuously in autoperfused dog gastrocnemii using PVC liquid membrane electrodes. O2 consumption (VO2), blood flow and performance of the muscles were also determined. The muscles were stimulated indirectly and isotonic tetanic contractions (0.2 s) were produced every 0.7 s for more than 45 min. 1. [K+]e started to increase immediately after the onset of exercise and reached a maximal value of 7.4 meq/l after 4 min of exercise, thereafter it decreased, reaching 5.3 meq/1 at the end of the 12 min exercise. After 6 min of recovery [K+]e became lower than the control level. [K+]ven reached maximal values of 5.0 meq/l after 30 s of exercise and thereafter decreased slowly to 3.8 meq/l at the end of exercise. Thus, a K+ gradient of up to 3 meq/l was observed between the interstitial space and the venous blood. About 30 s after the end of exercise a net K+ uptake of up to 0.3 mu eq per min per g was observed. 2. The K+ loss of the muscle fibres reached maximal values of 1.5 mu eq per min per g at 1.5 min after the onset of exercise. Total K+ loss was 7% during 12 min of exercise and 12.5% of intracellular K+ during 45 min of exercise. 3. The changes of [K+]e correlated closely with performance and VO2 during exercise but not during recovery. On the other hand, blood flow correlated with the changes of [K+]e during both exercise and recovery. These results support the hypothesis that changes of [K+]e of the working muscle might be an important factor regulating exercise hyperemia.

Animals↗
PubMed1984

Mechanisms of hypoxia-induced decrease of load dependence of relaxation in cat papillary muscle.

Relaxation of mammalian cardiac muscle is very sensitive to the prevailing load, but becomes largely load-independent during hypoxia. This effect was previously ascribed to a delayed removal of activating myoplasmic calcium. To further elucidate the underlying mechanisms of this effect of hypoxia, relaxation was now studied in 26 cat papillary muscles, in which hypoxia-induced decrease of load dependence of relaxation was compared with the effects of low [Ca2+]o (1.0, 0.5, 0.375 mM), verapamil (1 microM) and nifedipine (0.1 microM). Load dependence of relaxation was quantified by comparing force and time coordinates at the onset of the isometric relaxation phase in several after-loaded isotonic twitch contractions with the relaxation of the isometric control contraction. Hypoxia, low [Ca2+]o, verapamil and nifedipine decreased load dependence of relaxation. Although low [Ca2+]o, verapamil and nifedipine had a more marked negative inotropic effect on the contraction phase than hypoxia, the decrease of load dependence with hypoxia was significantly more pronounced and it included two phases: an early and fast drop, followed by a slower and longer-lasting decrease. The early fast phase was neutralized in low [Ca2+]o and also diminished after administration of verapamil or nifedipine. An impaired calcium reuptake by the sarcoplasmic reticulum would underly only the second phase of decreased load dependence. The first phase on the other hand originated mainly from changes in the isometric relaxation of the papillary muscles.

Animals↗
PubMedDate not supplied

The necessity of using two parameters to describe isotonic shortening velocity of muscle tissues: the effect of various interventions upon initial shortening velocity (vi) and curvature (b).

In skinned skeletal muscle fibers and skinned preparations of myocardium or smooth muscle, for all conditions studied, the length traces during isotonic shortening are always found to be significantly curved. It is demonstrated that the observed curvature is not simply due to inhomogeneities on the sarcomere level in striated muscle, damaged ends of the preparations, double overlap and collision of filaments, or depletion of MgATP during the period of isotonic shortening. It is shown that the velocity of shortening can be described by an exponential function: v = vi exp (-b[SLi-SL]) with SLi: sarcomere length at the start of the release; SL: sarcomere length during isotonic shortening. Thus, instantaneous shortening velocity (v) is determined by two parameters: vi, the initial shortening velocity for SL = SLi, and b, a constant characterizing the decrease in velocity during isotonic shortening. Factors which affect isotonic shortening can do this by affecting vi, or by changing b, or both. Therefore, when analysing the effects of interventions which affect instantaneous shortening velocity, these two possibilities have to be distinguished. Since curvature of the length traces might be caused by noncross-bridge components, only vi, the initial speed of shortening, is a parameter which directly reflects kinetics of the cross-bridge cycle while instantaneous speed of shortening might also be affected by noncross-bridge factors. Analysing isotonic shortening in terms of vi and b, the effects of ionic strength, free Ca++ concentration, MgATP/MgADP ratio and temperature on unloaded isotonic shortening have been studied. For the conditions used, it can be shown that ionic strength and free Ca++ concentration only affect b without significant effect on vi, whereas MgATP/MgADP ratio and temperature affect both vi and b. This means that of these factors only MgATP/MgADP ratio and temperature affect the cross-bridge kinetics which determine the maximum speed of shortening while ionic strength and free Ca++ concentration have no such effect within the experimental error.

Adenosine Triphosphate↗
PubMed1985

Hindered muscle relaxation in spasticity: experimental evidence suggesting a possible pathophysiological mechanism.

In ten spastic patients and in an equal number of healthy controls, the relaxation phase occurring at the end of an isotonic voluntary contraction has been studied on soleus muscle using EMG and H-reflex methods. In the spastic group, the duration of motor unit-decruitment was consistently prolonged (from two to six times the control values). Moreover, the decrease in the excitability of the H-reflex arc, which normally accompanies the end of muscle contraction was delayed in time, reduced in amplitude or in some cases even absent. As a rule, patients in whom such release-associated inhibition (RAI) was lacking or severely reduced exhibited the longest motor unit-decruitment times, due to the interference of sustained clonic sequences. It is proposed that a lowered effectiveness of RAI might explain the clonic activity which frequently hinders voluntary muscle relaxation in spasticity.

Adult↗
PubMed2003

Effects of non-specific vs individualized exercise training protocols on aerobic, anaerobic and strength performance in severely obese subjects during a short-term body mass reduction program.

The purpose of the present study was to compare aerobic, anaerobic and strength performance changes induced by two short-term (3-week) body mass reduction programs based on the same low-calory diet (1200-1500 kcal/day), nutritional education and psychological counseling, but entailing different exercise training protocols. An individualized, low-volume and moderate-intensity exercise training (IET) was contrasted with a non-specific, high-volume, low-intensity exercise training (NET). Thirty obese in-patients (12 males, 18 females; mean age +/- SD: 33.9 +/- 9.4 yr, range: 19-51yr; mean BMI: 40.5 +/- 3.8 kg/m2, range: 35.3-51.4 kg/m2) were randomly divided in two gender-matched groups of 15 subjects each undergoing a different exercise training protocol. Maximum oxygen uptake (VO2max) determined with a submaximal indirect test on a bicycle ergometer, lower limb maximum power output (W(max)) determined with the jumping method, global motor capabilities determined by analysis of locomotor pattern during a short (8 m) running, maximum strength (1-RM) of upper and lower limb muscle groups determined with isotonic machines were tested before and after the program. Adherence to an individual exercise activity and maintenance of body weight (bw) loss were evaluated with a telephonic interview 6 months after the completion of the program. In both groups a significant (p < 0.001) and comparable weight loss was observed (IET: -4.27%; NET: -4.17%). In both groups VO2max and W(max) increased significantly (p < 0.05-0.001) when expressed relatively to body mass, while in absolute terms they were significantly (p < 0.001) improved only in IET group. 1-RM in all tested muscle groups was significantly increased in both IET and NET subjects (p < 0.001-0.01), but improvements were significantly greater in IET as compared with NET (p < 0.05-0.001). The analysis of locomotor pattern during the short running indicated that IET subjects significantly improved their global motor capabilities (p < 0.05-0.001), while no change was observed in NET group. After 6 months, IET subjects reported a level of spontaneously chosen physical activity significantly higher (p < 0.05) than NET subjects, displaying a trend of further decrease in bw. It was concluded that, although no difference in bw loss was appreciated between the two studied groups and significant improvements were found also in subjects performing NET protocol, the IET protocol offers better overall results in terms of muscle performance and physical fitness, with a possibly stronger motivation to subsequent exercise activity.

Adult↗
PubMed2002

Characteristics of histamine tachyphylaxis in rat uterine smooth muscle.

OBJECTIVE AND DESIGN: To study both the desensitisation induced by short-term exposure to histamine and the mechanism responsible in the isolated rat uterus. MATERIAL: Precontracted isolated uterus (37 mM KCl) from oestrogenised Wistar rats were used. TREATMENT: Repetitive responses to histamine (10(-6), 10(-5), 10(-4), 10(-3) M), dimaprit and clonidine (10(-4) M) were tested at 15, 30, 45 and 105 min., with their modifications by (5 mg/kg, 24 h before sacrifice) reserpine, 10(-7) M propranolol, 10(-8) M atropine, and 10(-6) M indomethacin. Dose-response curves for adrenaline were carried out as standard protocol. METHODS: In vitro techniques (de Jalon's solution, 31 degrees C, carbogen, isotonic registration, resting tension 1 g). Levels of cAMP were studied in response to histamine, adrenaline and isoproterenol by radioassay. RESULTS: Repeated histamine produced a rapid loss of inhibitory uterine response depending on the number of exposures and increase in concentration. The tachyphylaxis phenomenon is not modified by the different pretreatments used. Dimaprit, but not clonidine or adrenaline, produced tachyphylaxis. The second exposition to 10(-3) M histamine produced a 38.8% reduction in cAMP production. CONCLUSION: Histamine appears to induce homologous and probably cAMP-dependent desensitisation of H2-receptors.

Adrenergic alpha-Agonists↗
PubMed2002

Relationship between passive properties of the calf muscles and plantarflexion concentric isokinetic torque characteristics.

The purpose of this study was to use a model of aging to examine the relationships between passive properties of the calf muscles and plantarflexion concentric isokinetic torque characteristics. Eighty-one active women 20-84 years of age were tested using a Kin-Com isokinetic dynamometer interfaced with electromyography (EMG). The passive properties were tested by stretching the muscles from relaxed plantarflexion to a maximal dorsiflexion (DF) angle at a rate of 5 degrees.s(-1) (0.087 rad.s(-1)) with minimal raw EMG activity (<0.05 mV). The maximal concentric torque was tested from maximal passive DF into plantarflexion at four randomly ordered velocities of 30, 60, 120, and 180 degrees.s(-1). Pearson correlation coefficients (Bonferroni adjusted) indicated a hierarchical order of high to moderate positive correlations between four passive properties and the peak and mean concentric torque for all test velocities. Correlation coefficients for the four passive properties ranged from 0.50 to 0.78 ( P<0.001), and the coefficients of determination ( r(2)) from higher to lower were: (1) maximal DF passive resistive torque ( r(2): 0.50-0.62), (2) length extensibility ( r(2): 0.40-0.49), (3) maximal muscle length ( r(2): 0.28-0.41), and (4) passive elastic stiffness in the last half of the full-stretch range of motion ( r(2): 0.25-0.31). The maximal DF passive resistive torque and the length extensibility accounted for 50-62% and 40-49% of the variability in the concentric torque, respectively. The results indicate that the concentrically stronger calf muscles of active women were positively correlated with passively stronger, longer, and stiffer calf muscles, which are characteristics of the calf muscles of younger women. Further studies are needed to examine whether therapeutic interventions, such as stretching and strengthening, can promote adaptations in the calf muscles of older women to attain these more youthful characteristics.

Adult↗
PubMed1986

Central and peripheral components of cardiac failure.

Chronic heart failure results from two processes, i.e., myocardial and congestive failure. Myocardial failure is clinically silent, most often progresses slowly, and is documented by a depressed left ventricular ejection fraction. Multiple etiologic factors include systolic and diastolic overloads, myocardial necrosis and/or ischemia, and, perhaps, microvascular spasm. Myocardial failure ultimately leads to exaggerated neurohumoral compensatory mechanisms and derangements of the peripheral circulation, which are the hallmarks of congestive heart failure. At that stage of the syndrome, patients have symptoms, initially, with exercise and, later, at rest. Objective assessment of severity is afforded by determination of maximal oxygen uptake during maximal exercise testing. When congestive heart failure supervenes, the prognosis is poor. Current medical therapy is aimed at improving the derangements of the peripheral circulation, which relieves the symptoms but leaves the primary myocardial process unaffected. The goal of future therapy is to intervene at an earlier stage of the syndrome to halt or even partially reverse the myocardial failure.

Aminopyridines↗
PubMed1993

Reliability of eccentric isokinetic knee flexion and extension measurements.

This study assessed the test-retest reliability of knee isokinetic eccentric muscle performance in subjects with and without a history of tibio-femoral pathology. Nineteen adults were tested at 60 degrees/sec and 180 degrees/sec on three occasions using a standardized protocol that incorporates a same-session learning phase. Results revealed moderate to excellent reliability for average peak torque test-retest ICC (2,1) = .58 to .96, total work ICC = .63 to .93, and power ICC = .67 to .93. Joint angle at peak torque was unreliable (ICC = .01 to .69) for both muscle groups at both angular velocities. Knee flexion reliability was higher than extension reliability at both 60 degrees/sec and 180 degrees/sec. Subjects with tibio-femoral pathologies had ICC values lower than the healthy subjects. Reliable eccentric isokinetic measurements can be obtained for average peak torque, total work, and power. Clinicians should not assume the same degree of reliability in testing patients as in testing healthy subjects.

Adult↗
PubMed1993

Biomechanical analysis of the knee extension exercise.

A mathematical analysis of knee extension and flexion exercise is presented to determine effectiveness in strengthening the quadriceps and hamstring muscles. A quantitative relationship between the quadriceps force and the hamstring force is obtained for several variations of the exercises. The theoretical results are supplemented with experimental studies performed on subjects exercising with the Tekdyne Incentive Dynamometer.

Biomechanical Phenomena↗
PubMed1988

Frequency response analysis of human saccadic eye movements: estimation of stochastic muscle forces.

A frequency response method is used to estimate parameters of a fourth-order model of the oculomotor system and the active state tensions during a saccadic eye movement. The lateral and medial rectus muscle of each eye is modeled as a parallel combination of an active state tension generator with a viscosity and elastic element, connected to a series elastic element. The eyeball is modeled as a sphere connected to a viscosity and elastic element. Each of these elements is assumed to be ideal and linear. The active state tension for each muscle is modeled by a low-pass filtered pulse-step waveform. Initial estimates of the oculomotor mechanical components are based on physiological evidence. Initial estimates of the active state tension are based on an extrapolation of the eye movement trajectory. Horizontal saccadic eye movements were recorded from infrared signals reflected from the anterior surface of the cornea and then digitized. Parameter estimates were calculated for the model by using a conjugate gradient search program which minimizes the integral of the absolute value of the squared error between the model and the data. The predictions of the model are shown to be in good agreement with the data. Final estimates of motoneuronal activity demonstrate that the agonist muscle is maximally stimulated during the early portion of a saccadic eye movement regardless of the amplitude of the saccade; only the duration of the maximal stimulation affects the size of the saccade. The antagonist muscle is completely inhibited during the period of maximum agonist muscle stimulation. Furthermore, it is demonstrated that saccade motoneuronal activity is a stochastic phenomenon.

Elasticity↗
PubMed1994

Compliance of normal, dystrophic and transplanted mouse muscles.

Parallel and series compliances have been studied in extensor digitorum longus (fast) and soleus (slow) muscles in normal (strain C57BL/10) and dystrophic (strain mdx) mice, and in muscles regenerated after transplantation. Resting elasticity was analysed by measuring the tension-length relationship in unstimulated muscles. Passive tension is larger in mdx and in transplanted muscles than in their normal controls: at 1.15L0, passive tension is 0.12P0 in controls, 0.32P0 in mdx, and 0.40P0 in transplanted muscles. The differences are statistically significant. This indicates that passive tension is mainly determined by the amount of connective tissue. The stress-strain relationship of the series compliance was analysed by the method of isotonic releases during tetani. It is adequately described by a single exponential equation, with a rate constant of about 8P0/P. No difference was found between the various muscles studied. Extension of the series compliance at P0 is 0.02L0. Compliance is about 3% (L0/P0) at 0.2P0, and is not significantly different from zero at P0. Series compliance is thus very low in mouse muscles, substantially lower than in frog and rat muscles. Consequently, it can be neglected in studies of whole mouse muscle in which tension is higher than 0.4P0.

Animals↗
PubMed1992

Changes in muscarinic acetylcholine receptors in the isolated duodenum from repeatedly cold-stressed rats and the effect of neurotropin.

In rats repeatedly cold-stressed by specific alternation of rhythm in environmental temperature (SART-stressed rats), the contractile response to acetylcholine (ACh) of the isolated duodenum was remarkably decreased, whereas the contractile responses to K+, Ba2+ and Ca2+ were comparable to those in non-stressed rats. The amount of [3H]quinuclidinyl benzilate in the duodenum of SART-stressed rats was about 50% of that in non-stressed rats, but the KD value remained unchanged. Long-term administration of hexamethonium prevented the changes in SART-stressed rats. The daily treatment with Neurotropin, an extract isolated from inflamed rabbit dermis inoculated with vaccinia virus, dose-dependently prevented the changes in SART-stressed rats. However, Neurotropin had no effect on the ACh-induced decrease in muscarinic ACh receptor (m-ACh.R) in cultured vas deferens of guinea pig. These results suggest that down-regulation of m-ACh.R in duodenum by SART stress may be associated with enhanced activity in the parasympathetic center. Moreover, Neurotropin is thought to prevent the down-regulation of m-ACh.R throughout the central nervous system.

Acetylcholine↗