Catchlike-inducing train activation of human muscle during isotonic contractions: burst modulation.
(17/794)
Stimulation trains that exploit the catchlike property [catchlike-inducing trains (CITs)] produce greater forces and rates of rise of force than do constant-frequency trains (CFTs) during isometric contractions and isovelocity movements. This study examined the effect of CITs during isotonic contractions in healthy subjects. Knee extension was electrically elicited against a load of 10% of maximum voluntary isometric contraction. The stimulation intensity was set to produce 20% of maximum voluntary isometric contraction. The muscle was tested before and after fatigue with a 6-pulse CFT and 6-pulse CITs that contained an initial doublet, triplet, or quadruplet. For prefatigue responses, the greatest isotonic performance was produced by CITs with initial doublets. When the muscles were fatigued, triplet CITs were best. CITs produce greater excursion, work, peak power, and average power than do CFTs, because CITs produced more rapid rates of rise of force. Faster rates of rise of force enabled the preload on the muscle to be exceeded earlier during the stimulation train. (+info)
Popliteal pterygium syndrome: a clinical study of three families and report of linkage to the Van der Woude syndrome locus on 1q32.
(18/794)
Popliteal pterygium syndrome (PPS) is a rare autosomal dominant disorder, thought to occur with an incidence of approximately 1 in 300 000 live births. The main clinical manifestations are popliteal webbing, cleft lip, cleft palate, lower lip pits, syndactyly, and genital and nail anomalies. This report describes the clinical features in two families with PPS and one isolated case, showing the range of anomalies found both within and between the families. PPS has some features in common with Van der Woude syndrome (VWS), also inherited as an autosomal dominant condition, with cleft lip/palate and, more distinctively, lower lip pits. Although the gene for VWS has not yet been identified, it has been localised to within 1.6 cM in the region 1q32-41. To determine whether PPS and VWS represent allelic forms of the same gene, three families were genotyped for markers flanking and within the critical region. A multipoint lod score of 2.7 was obtained, with no evidence of recombination, supporting the hypothesis that these two disorders are allelic. (+info)
Coincident development of sesamoid bones and clues to their evolution.
(19/794)
Sesamoid bones form within tendons in regions that wrap around bony prominences. They are common in humans but variable in number. Sesamoid development is mediated epigenetically by local mechanical forces associated with skeletal geometry, posture, and muscular activity. In this article we review the literature on sesamoids and explore the question of genetic control of sesamoid development. Examination of radiographs of 112 people demonstrated that the relatively infrequent appearances of the fabella (in the lateral gastrocnemius tendon of the knee) and os peroneum (in the peroneus longus tendon of the foot) are related within individuals (P < 0.01). This finding suggests that the tendency to form sesamoids may be linked to intrinsic genetic factors. Evolutionary character analyses suggest that the formation of these sesamoids in humans may be a consequence of phylogeny. These observations indicate that variations of intrinsic factors may interact with extrinsic mechanobiological factors to influence sesamoid development and evolution. (+info)
A new anterior approach to the sciatic nerve block.
(20/794)
BACKGROUND: Although several anterior approaches to sciatic nerve block have been described, they are used infrequently. The authors describe a new anterior approach that allows access to the sciatic nerve with the patient in the supine position. METHOD: Sciatic nerve blocks were performed in 22 patients. A line was drawn between the inferior border of the anterosuperior iliac spine and the superior angle of the pubic symphysis tubercle. Next, a perpendicular line bisecting the initial line was drawn and extended 8 cm caudad. The needle was inserted perpendicularly to the skin, and the sciatic nerve was identified at a depth of 10.5 cm (9.5-13.5 cm; median and range) using a nerve stimulator and a 15-cm b-beveled insulated needle. After appropriate localization, either 30 ml mepivacaine, 1.5% (group 1 = knee arthroscopy; n = 16), or 15 ml mepivacaine, 1.5%, plus 15 ml ropivacaine, 0.75%, (group 2 = other procedures; n = 6) was injected. RESULTS: Appropriate landmarks were determined within 1.3 min (0.5-2.0 min). The sciatic nerve was identified in all patients within 2.5 min (1.2-5 min), starting from the beginning of the appropriate landmark determination to the stimulation of its common peroneal nerve component in 13 cases and its tibial nerve component in 9 cases. A complete sensory block in the distribution of both the common peroneal nerve component and the tibial nerve component was obtained within 15 min (5-30 min). A shorter onset was observed in patients who received mepivacaine alone compared with those who received a mixture of mepivacaine plus ropivacaine (10 min [5-25 min] vs. 20 min [10-30 min]; P < 0.05). Recovery time was 4.6 h (2.5-5.5 h) after mepivacaine administration. The addition of ropivacaine produced a block of a much longer duration 13.8 h (5.2-23.6 h); P < 0.05. No complications were observed. CONCLUSIONS: This approach represents an easy and reliable anterior technique for performing sciatic nerve blocks. (+info)
Influence of elastic properties of tendon structures on jump performance in humans.
(21/794)
The purpose of this study was to quantify the elastic properties of tendon structures in vivo and to investigate the influence of the tendon properties on jump performance with and without countermovement. Elongation of the tendon and aponeurosis of vastus lateralis muscle (dL) was directly measured by ultrasonography while subjects (n = 31) performed ramp isometric knee extension up to the voluntary maximum (MVC). The relationship between muscle force and dL was fitted to a linear regression above 50% MVC, the slope of which was defined as stiffness of the tendon structures. Statistical analysis revealed no significant difference between duplicated measurements of stiffness, with an interday reliability of r = 0.88 and a coefficient of variance of 6.1%. Although the stiffness was not significantly related to absolute jump height in either vertical jump, it was inversely correlated with the difference in jump height between the vertical jumps performed with and without countermovement. The results suggested that the stiffness of tendon structures has a favorable effect on stretch-shortening cycle exercise, possibly due to adequate storage and recoil of elastic energy. (+info)
Human femoral artery diameter in relation to knee extensor muscle mass, peak blood flow, and oxygen uptake.
(22/794)
It is not known whether the diameter of peripheral conduit arteries may impose a limitation on muscle blood flow and oxygen uptake at peak effort in humans, and it is not clear whether these arteries are dimensioned in relation to the tissue volume they supply or, rather, to the type and intensity of muscular activity. In this study, eight humans, with a peak pulmonary oxygen uptake of 3.90 +/- 0.31 (range 2.29-5.03) l/min during ergometer cycle exercise, performed one-legged dynamic knee extensor exercise up to peak effort at 68 +/- 7 W (range 55-100 W). Peak values for knee extensor blood flow (thermodilution) and oxygen uptake of 6.06 +/- 0.74 (range 4.75-9.52) l/min and 874 +/- 124 (range 590-1,521) ml/min, respectively, were achieved. Pulmonary oxygen uptake reached a peak of 1.72 +/- 0.19 (range 1.54-2.33) l/min. Diameters of common and profunda femoral arteries determined by ultrasound Doppler were 10.6 +/- 0.4 (range 8.2-12.7) and 6.0 +/- 0.4 (range 4.5-8.0) mm, respectively. Thigh and quadriceps muscle volume measured by computer tomography were 10.06 +/- 0.66 (range 6.18-10.95) and 2.36 +/- 0.19 (range 1.31-3.27) liters, respectively. The common femoral artery diameter, but not that of the profunda branch, correlated with the thigh volume and quadriceps muscle mass. There were no relationships between either of the diameters and the absolute or muscle mass-related resting and peak values of blood flow and oxygen uptake, peak pulmonary oxygen uptake, or peak power output during knee extensor exercise. However, common femoral artery diameter correlated to peak pulmonary oxygen uptake during ergometer cycle exercise. In conclusion, common and profunda femoral artery diameters are sufficient to ensure delivery to the quadriceps muscle. However, the common branch may impose a limitation during ergometer cycle exercise. (+info)
Level of arousal and the ability to maintain wakefulness.
(23/794)
The ability to maintain wakefulness under baseline and sleep deprivation conditions was examined in a group of 14 normal young adults. Subjects participated in both standard and manipulation Maintenance of Wakefulness tests after being awake for 7, 19, and 31 h. In the manipulation Maintenance of Wakefulness tests, subjects performed varying degrees of physical activity at the onset of stage 1 to allow them to preserve wakefulness. As expected, ability to maintain wakefulness declined as time awake increased. With amount of time awake held constant, wakefulness was enhanced most after standing and doing knee bends, less after standing, less after sitting up, and least after subjects were spoken to. The improvement in alertness after doing knee bends as compared to being spoken to was of the same relative magnitude as the decrease in alertness after one night of total sleep deprivation. As expected, heart rate also increased consistently as activity increased. Each subject had a negative correlation between their EEG sleep latencies and their minimum r-r interval during the manipulation, i.e. the higher the heart rate, the longer the latency. These data were interpreted as a demonstration of the impact of discrete phasic arousal on the ability to maintain wakefulness. (+info)
Technical evolution of arthoscopic knee surgery.
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The widespread growth of arthroscopic techniques and their use has dramatically changed the practice of orthopaedic surgery. A high degree of clinical accuracy and minimally invasive procedure with a low surgical morbidity have encouraged the use of arthroscopy to assist in diagnosis, to determine prognosis and to provide treatment. In particular, the knee is the proper joint in which arthroscopy has its diagnostic and intraarticular surgical application. The rapid advancement of arthroscopic techniques has demonstrated a variety of surgical techniques in procedures such as meniscectomy, meniscal repair and cruciate ligament reconstruction during the last decade. This article reviews the past history of arthroscopy and technical evolution of arthroscopy in knee surgery in our department. (+info)