[Care of spinal injuries in New Zealand. International recognition of devoted work in research and development].
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Hospital Units↗
Biomedical subjects
J Fridén
Publications and source records attributed to J Fridén.
Substance P and calcitonin gene-related peptide expression at the extensor carpi radialis brevis muscle origin: implications for the etiology of tennis elbow.
With use of immunohistochemistry and antibodies to substance P and calcitonin gene-related peptide, nerve fibers showing substance P-like and calcitonin gene-related peptide-like immunoreactivity were demonstrated at the origin of the extensor carpi radialis brevis muscle in patients with tennis elbow (n = 6) and in healthy controls (n = 6). The nerve fibers were distributed in association with a subpopulation of small blood vessels and in nerve bundles but were not distributed in the tunica media-adventitia junction of the arterioles. There were no inflammatory-cell infiltrates and few solitary mast cells. The present study gives further evidence to previous suggestions that tennis elbow is not an inflammatory process in the sense of involving inflammatory cells. Frequent mechanical involvement affects sensory innervation, and substance P and calcitonin gene-related peptide may have various important efferent effects, including microvascular leakage and local edema formation; therefore, the observations from this study constitute a morphological substrate for possible effects of substance P and calcitonin gene-related peptide at the origin of the extensor carpi radialis brevis muscle.
Adult↗
Task design, psycho-social work climate and upper extremity pain disorders--effects of an organisational redesign on manual repetitive assembly jobs.
A company redesign was carried out to improve production efficiency and minimise the prevalence of work-related musculoskeletal disorders and sick leave. The redesign was evaluated on the basis of studies of assembly workers before (17 workers) and after (12 workers) the redesign. The redesign resulted in more varied, less repetitive, and more autonomous assembly jobs. The psycho-social work climate was both improved and impaired. A medical examination showed that eight of 17 workers before and nine of 12 workers after the redesign suffered from upper extremity pain disorders. Neither the production goals nor the goals of the redesign were fulfilled. Our conclusion was that the increased task variation and impaired psycho-social work climate, combined with a lack of skill and competence, actually increased the physical stress, risk for disorders and difficulties in fulfilling the production goals.
Adult↗
Sarcomere length varies with wrist ulnar deviation but not forearm pronation in the extensor carpi radialis brevis muscle.
Extensor carpi radialis brevis (ECRB) sarcomere length was measured in seven patients using intraoperative laser diffraction. Sarcomere length was measured with the forearm in one of four positions: wrist in neutral with regard to radial-ulnar deviation and forearm in neutral rotation, wrist in ulnar deviation and forearm in neutral rotation, wrist in neutral and forearm in pronation, and wrist in ulnar deviation and forearm in pronation. Two-way ANOVA comparing sarcomere length between the four positions revealed a significant effect of ulnar deviation (p < 0.05), no significant effect of pronation (p > 0.7) and no significant interaction (p > 0.9). These results demonstrate that the axes of forearm rotation and wrist radial-ulnar deviation act independently, at least with regard to the ECRB and have implications regarding the etiology of tennis elbow.
Adult↗
Mechanisms of muscle injury after eccentric contraction.
Eccentric contractions of skeletal muscles produce injury and, ultimately, muscle strengthening. Current data suggests that the earliest events associated with injury are mechanical in nature and may be based primarily on the sarcomere strain experienced by the muscle. In this review, recent experimental data, primarily from rabbit dorsiflexor muscles, are used to provide general information regarding the factors that cause injury and means for preventing injury. Mechanical experiments reveal that excessive sarcomere strain is the primary cause of injury. We hypothesize that excessive strain permits extracellular or intracellular membrane disruption that may permit hydrolysis of structural proteins leading to the myofibrillar disruption that is commonly observed. Inflammation that occurs after injury actually further degrades the tissue, but prevention of the inflammation leads to a long-term loss in muscle function. Simple treatments such as increasing muscle oxidative capacity ("getting into shape") or cyclic stress-relaxation of tissue ("stretching out") have no measurable effect on the magnitude of muscle injury that occurs. Ultimately, an improved understanding of the damage mechanism may improve our ability to provide rehabilitative and strengthening prescriptions that have a rational scientific basis.
Animals↗
Swelling of sarcoplasmic reticulum in the periphery of muscle fibres after isometric contractions in rat semimembranosus lateralis muscle.
The decline in isometric force, swelling of sarcoplasmic reticulum and loss of desmin was measured in semimembranosus lateralis muscle of male Wistar rats immediately after a short series of brief (500 ms) maximal isometric contractions. For the active muscle, the series ended below (protocol A) and just over muscle optimum length (protocol AA). In one protocol, the muscle remained passive and was extended to lengths just over muscle optimum length (protocol P). After all experimental protocols, no loss of desmin was observed and sarcomere appearance was normal. Protocol A produced swelling (87%) of the sarcoplasmic reticulum but no decline in isometric force. Protocol AA produced larger swelling (147%) of the sarcoplasmic reticulum and an isometric force decline (<49%) at short muscle lengths. Swelling of sarcoplasmic reticulum was observed mainly in the periphery of muscle fibres. Protocol P did not result in swelling of the sarcoplasmic reticulum and isometric force decline. It is concluded that swelling of the sarcoplasmic reticulum in the periphery of muscle fibres after brief maximal isometric contractions is associated with muscle force and not muscle length.
Animals↗
Wrist extensor muscle pathology in lateral epicondylitis.
The morphology of the extensor carpi radialis brevis (ECRB) muscle was investigated in 20 patients with longstanding lateral epicondylitis. Muscle biopsies were obtained from the proximal or distal portion of the ECRB and analysed by enzyme- and immunohistochemical methods. Morphological abnormalities were significantly more frequent in patients than controls and included moth-eaten fibres, fibre necrosis and signs of muscle fibre regeneration as well as higher percentages of the fast-twitch oxidative (type 2A) fibre type. Changes were equally distributed proximally and distally. It is concluded that these changes, directly or indirectly, may reflect the cumulative effect of mechanical and/or metabolic overload and that decreased muscular performance in patients with lateral epicondylitis may be due to both elbow pain and physical damage to the ECRB muscle.
Adult↗
Sympathetic and sensory innervations are heterogeneously distributed in relation to the blood vessels at the extensor carpi radialis brevis muscle origin of man.
By using immunohistochemistry and antibodies to a general nerve marker, protein gene product (PGP) 9.5, the overall innervation at the extensor carpi radialis brevis (ECRB) muscle origin was investigated in patients with tennis elbow and in healthy controls. The autonomic innervation was studied by using antibodies to neuropeptide Y (NPY), tyrosine hydroxylase (TH), and vasoactive intestinal peptide (VIP). The sensory innervation was visualized by using antibodies to substance P and calcitonin gene-related peptide. PGP 9.5 immunoreactions were detected in association with small blood vessels and arteries and within nerve bundles. There was, however, heterogeneity in the perivascular nerve fiber distribution since some blood vessels exhibited a high degree of PGP 9.5 innervation and some negligible or no such innervation at all. There was marked TH/NPY innervation in the walls of a subpopulation of the arteries, basically no VIP-containing nerves, and sensory innervation restricted to the small blood vessels. These observations show that the ECRB muscle origin is supplied with heterogeneously distributed sympathetic and sensory innervations and, furthermore, that there appears to be an imbalance between the vasoconstrictor and vasodilator innervations along the vascular tree in this region.
Adult↗
[Reconstructive hand surgery after cervical spinal injury: a new method increases the possibilities to reconstruct important functions].
The sarcomere is the basic unit of force generation in skeletal muscle. Since muscle force generation is highly dependent on sarcomere length, it is important to know the normal range of sarcomere length if informed decisions are to be made regarding surgical procedures affecting muscle length, such as tendon transfer or lengthening. The article reports intraoperative sarcomere length measurement with a laser diffraction technique. Sarcomere length as a function of joint angle was monitored during various tendon transfers performed to restore lost finger, thumb, wrist, forearm and elbow function in tetraplegics. The intraoperative measurements were essentially the same as those obtained in cadaveric muscle sarcomere models. Muscle fiber length, torque and tendon length are the most important structural determinants of the operating range and torque profile of each motor, while the relation between passive tension and active force is the most critical factor in making surgical decisions.
Arm↗
Segmental muscle fiber lesions after repetitive eccentric contractions.
Immunohistochemical and electron-microscopic techniques were used to analyze the extensor digitorum longus muscles of New Zealand White rabbits 1 h, 1 day, 3, 7, and 28 days after repetitive eccentric contractions. Loss of the cytoskeletal protein desmin was the earliest manifestation of injury. Apart from 1 h post-exercise, all desmin-negative fibers stained positively with antibody to plasma fibronectin, indicating loss of cellular integrity accompanying cytoskeletal disruption. Fiber sizes were significantly increased from 1-7 days after exercise. The large (hyaline) fibers found in histological sections after repetitive eccentric contractions resulted from segmental hypercontraction of the fiber. This phenomenon occurred proximally and distally to plasma membrane lesions of the muscle fiber and necrosis and manifested itself as very short sarcomere lengths. Thus, in serial sections, staining characteristics, sizes and shapes of one and the same fiber often varied dramatically. We conclude that the following sequence of events occurs: cytoskeletal disruptions, loss of myofibrillar registry, i.e., Z-disk streaming and A-band disorganization, and loss of cell integrity as manifested by intracellular plasma fibronectin stain, hypercontracted regions, and invasion of cells. When a fiber is disrupted, the remaining intact fibers apparently take up the tension put on the muscle and later fewer fibers are subjected to eccentric contractions.
Animals↗
Evidence for muscle attachment at relatively long lengths in tendon transfer surgery.
Sarcomere length was measured intraoperatively during 22 tendon transfers about the wrist primarily involving the flexor carpi ulnaris (15), but also including the extensor carpi radialis longus (4) and brachioradialis (3). Muscle tension during transfer was chosen based on traditional guidelines suggested for optimal function. After these criteria were used, it was determined that sarcomere lengths were consistently much longer than optimal lengths, even to the point of resulting in zero active tension generation. Average sarcomere length after transfer was 3.78+/-0.52 microm (mean+/-SD), which was significantly different than optimal sarcomere length (2.8 microm) in human skeletal muscle. Muscles were predicted to generate on average-on the basis of the 3.78-microm sarcomere length-only 28% of maximum active force. This appeared to be due to the fact that passive tension in upper-extremity skeletal muscles becomes important at only relatively long lengths. It is suggested that the use of passive tension as the major factor guiding intraoperative decision making results in overstretch of the muscle-tendon unit and accompanying low active force generation.
Humans↗
Musculoskeletal balance of the human wrist elucidated using intraoperative laser diffraction.
This review describes a series of experiments in which sarcomere length was measured in human wrist muscles to understand their design. Sarcomere length measurements were combined with studies on cadaveric extremities to generate biomechanical models of human wrist function and to provide insights into the mechanism by which wrist strength balance is achieved. Intraoperative measurements of the human extensor carpi radialis brevis (ECRB) muscle during wrist joint rotation reveal that this muscle appears to be designed to operate on the descending limb of its length-tension curve and generates maximum tension with the wrist fully extended. Interestingly, the synergistic extensor carpi radialis longus (ECRL) also operates on its descending limb but over a much narrower sarcomere length range. This is due to the longer fibers and smaller wrist extension moment arm of the ECRL compared to the ECRB. Sarcomere lengths measured from wrist flexors are shorter compared to the extensors. Using a combination of intrapoperative measurements on the flexor carpi ulnaris (FCU) and mechanical measurements of wrist muscles, joints and tendons, the general design of the prime wrist movers emerges: both muscle groups generate maximum force with the wrist fully extended. As the wrist flexes, force decreases due to extensor lengthening along the descending limb of their length-tension curve and flexor shortening along the ascending limb of their length-tension curve. The net result is a nearly constant ratio of flexor to extensor torque over the wrist range of motion and a wrist that is most stable in full extension. These experiments demonstrate the elegant match between muscle, tendon and joints acting at the wrist. Overall, the wrist torque motors appear to be designed for balance and control rather than maximum torque generating capacity.
Biomechanical Phenomena↗
Simultaneous stiffness and force measurements reveal subtle injury to rabbit soleus muscles.
The time course of force generation and the time course of muscle stiffness were measured in rabbit soleus muscles during eccentric contraction to understand the underlying basis for the force loss in these muscles. Muscles were activated for 600 msec every 10 sec for 30 min. Soleus muscles contracting isometrically maintained constant tension throughout the treatment period, while muscles subjected to eccentric contraction rapidly dropped tension generation by 75% within the first few minutes and then an additional 10% by the end of 30 min. This indicated a dramatic loss in force-generating ability throughout the 30 min treatment period. To estimate the relative number of cross-bridges attached during the isometric force generation phase immediately preceding each eccentric contraction, stiffness was measured during a small stretch of a magnitude equal to 1.5% of the fiber length. Initially, muscle stiffness exceeded 1300 g/mm and, as eccentric treatment progressed, stiffness decreased to about 900 g/mm. Thus, while muscle stiffness decreased by only 30% over the 30 min treatment period, isometric force decreased by 85%. In isometrically activated muscles, stiffness remained constant throughout the treatment period. These data indicate that, while soleus muscles decreased their force generating capability significantly, there were a number of cross-bridges still attached that were not generating force. In summary, the loss of force generating capacity in the rabbit soleus muscle appears to be related to a fundamental change in myosin cross-bridge properties without the more dramatic morphological changes observed in other eccentric contraction models. These results are compared and contrasted with the observations made on muscles composed primarily of fast fibers.
Animals↗
Increased oxidative capacity does not protect skeletal muscle fibers from eccentric contraction-induced injury.
Isometric electrical stimulation was delivered to rabbit dorsiflexor muscles at 10 Hz for 1 s on and 1 s off over 30 min, 5 days/wk for 3 wk to induce an increase in muscle oxidative capacity. Stimulation-trained muscles as well as untrained muscles were then subjected to a 30-min eccentric exercise bout to test whether increased oxidative capacity provided a protective effect against muscle injury. Electrical stimulation results in significant training of both the extensor digitorum longus (EDL) and tibialis anterior (TA) muscles, with EDL citrate synthase (CS) activity increasing an average of 67% (P < 0.0001) and TA CS activity increasing by 27% (P < 0.05). For all parameters measured, the magnitude of change was much greater for EDL than for TA muscle. Dorsiflexor fatigability decreased significantly during the 3-wk training period (P < 0.0001), whereas the EDL TA individually showed strong decreasing trends in fatigability after training. TA and EDL capillary density measured histomorphometrically increased from 839 +/- 56 to 1,026 +/- 71 mm-2 (P = 0.07) and from 589 +/- 37 to 792 +/- 66 mm-2 (P < 0.05), respectively. TA and EDL capillary-to-fiber ratio increased from 1.32 +/- 0.10 to 1.55 +/- 0.16 (P > 0.2) and 1.08 +/- 0.07 to 1.36 +/- 0.14 (P > 0.1), respectively. Type 2A fiber type percentage increased after stimulation training by 68% (P < 0.0001) for the EDL and by 32% (P > 0.1) for the TA at the expense of type 2D fibers. Despite the large training effect for the EDL and the modest training effect for the TA, no differences were observed between stimulation-trained and untrained groups for maximum dorsiflexion torque (P > 0.3) or maximum tetanic tension (P > 0.3) after eccentric contraction-induced injury. Additionally, no significant correlation was observed between CS activity and maximum tetanic tension after eccentric contraction-induced injury for either muscle (P > 0.2). Thus we conclude that increasing muscle oxidative capacity by isometric electrical stimulation training did not protect muscle against eccentric contraction-induced injury.
Animals↗
The relationships between EMG and muscle morphology throughout sustained static knee extension at two submaximal force levels.
This study investigated the relationship between muscle morphology and surface electromyographic parameters (mean frequency, f(mean); and signal amplitude, RMS) during sustained static knee extension to exhaustion at 25% maximal voluntary contraction (MVC) and at 70% MVC. Twenty clinically healthy subjects participated. EMGs were registered from the quadriceps. Muscle forces during knee extension at a 90 degree joint angle were maintained at the respective levels throughout the measurement periods. A biopsy was obtained of the vastus lateralis muscle. The total time to exhaustion was normalized for each subject. By means of regression analysis, the intercept (i) (i.e. the unfatigued state) and the regression coefficient (k) were determined for each EMG parameter. The endurance time increased with decreasing force level. A significantly higher perception of fatigue was found at 25% MVC than at 70% MVC. From principal component analyses it was concluded that RMS-k at 25% MVC mainly correlated with the type 2 muscle fibre proportions (%), and at 70% MVC mainly with the areas of type 2 muscle fibre. At 25% MVC, f(mean)-k correlated with the areas of type 2A, 2B and 2C fibres, and at 70% MVC negatively with the proportion of type 2B and to some extent with areas of type 2A, 2B and 2C fibres. f(mean)-i at 25% MVC correlated with fibre type proportions (%); f(mean)-i at 70% MVC correlated with the areas of type 2A, 2B and 2C. The present study indicates relationships between surface EMG and muscle morphology, which is contrary to presented models of the EMG.
Adult↗
Differential responses in intramuscular pressure and EMG fatigue indicators during low- vs. high-level isometric contractions to fatigue.
This study investigated changes in intramuscular pressure (IMP) and surface electromyographic (EMG) parameters (mean frequency of the power spectrum, f(mean); and signal amplitude denoted as root mean square, RMS) during contractions to fatigue at 25 and 70% of maximal voluntary contraction (MVC). Parameters were recorded simultaneously from the vastus lateralis muscle during knee extension. A significant decrease in f(mean) occurred with time at both contraction levels; however, the rate of decline (slope) was greater at 70% MVC. RMS increased throughout the contractions at both levels, with the relative increase being significantly greater for 25% MVC. IMP increased during 25% MVC but did not change during the 70% MVC contraction. IMP at rest was significantly higher post-contractions than it was pre-contractions at 25% MVC (21.1 vs. 8.0 mmHg, P < 0.01) and 70% MVC (13.7 vs. 8.6 mmHg, P < 0.01). Consequently, post-contraction IMP was higher at 25% MVC than at 70% MVC (P < 0.01). IMP changes throughout the fatiguing contractions correlated negatively with f(mean) and positively with RMS at both MVC levels; however, these correlations were better at 25% MVC. The extent of intramuscular water accumulation is discussed as a major cause of the difference in IMP changes between 25% and 70% MVC. Significant differences in the rate of change for all parameters between high vs. low contraction levels may suggest a common mechanism governing changes in IMP and EMG fatigue indicators.
Adult↗
Intraoperative measurement and biomechanical modeling of the flexor carpi ulnaris-to-extensor carpi radialis longus tendon transfer.
Sarcomere length was measured intraoperatively in five patients undergoing tendon transfer of the flexor carpi ulnaris (FCU) to the extensor carpi radialis longus (ECRL) for radial nerve palsy. All measurements were made with the elbow in 20 deg of flexion. Prior to tendon transfer, FCU sarcomere length ranged from 2.84 +/- .12 microns (mean +/- SEM) with the wrist flexed to 4.16 +/- .15 microns with the wrist extended. After transfer into the ECRL tendon, sarcomere length ranged from 4.82 +/- .11 microns with the wrist flexed (the new longest position of the FCU) to 3.20 +/- .09 microns with the wrist extended, resulting in a shift in the sarcomere length operating range to significantly longer sarcomere lengths (p < 0.001). At these longer sarcomere lengths, the FCU muscle was predicted to develop high active tension only when the wrist was highly extended. A biomechanical model of this tendon transfer was generated using normative values obtained from previous studies of muscle architectural properties, tendon compliance, and joint moment arms. Predicted sarcomere lengths pre- and post-tendon transfer agreed well with intraoperative experimental measurements. The theoretical wrist extension moment-wrist joint angle relationship was also calculated for a variety of values of FCU muscle length. These different lengths represented the different conditions under which the FCU could be sutured into the ECRL tendon. Variation in FCU muscle length over the range 200 mm to 260 mm resulted in large changes in absolute peak moment produced as well as the angular dependence of peak moment. This was due to the change in the region of FCU operation on its sarcomere length-tension curve relative to the magnitude of the ECRL moment arm. These data demonstrate the sensitivity of a short-fibered muscle such as the FCU to affect the functional outcome of surgery. In addition, we demonstrated that intraoperative sarcomere length measurements, combined with biomechanical modeling provide the surgeon with a powerful method for predicting the functional effect of tendon transfer surgery.
Adult↗
Intraoperative sarcomere length measurements reveal differential design of human wrist extensor muscles.
The design of the wrist extensor muscles was studied using a combination of intraoperative laser diffraction and biomechanical modelling of data obtained from human patients and previously published data. Intraoperatively, the change in sarcomere length per degree joint angle rotation (i.e. dSL/d omega) was measured as the wrist was moved from neutral to full flexion in both the extensor carpi radialis brevis (ECRB) and extensor carpi radialis longus (ECRL) muscles. Sarcomere length change per degree rotation was approximately twice as great for the ECRB compared with the ECRL muscle (9.06 +/- 1.06 versus 4.69 +/- 1.20 nm degree-1, mean +/- S.E.M., N = 7). Muscle fibre length and wrist extensor moment arms were obtained from published data and dSL/d omega calculated. The experimental values for dSL/d omega were extremely close to the calculated values. These data demonstrate that architectural differences between the ECRB and ECRL are accentuated by differences between their wrist extensor moment arms. This differential design may permit the extensor muscles, as a group, to generate high force over a wider range of velocities than would be possible with a single muscle or it may permit conservation of mass such that the two muscles together can generate approximately the same force and excursion as a single muscle but with approximately 30% less mass.
Humans↗