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The effects of a functional knee brace on intramuscular pressure in the leg and thigh were measured in eight subjects with a mean age of 32 years. Pressures in the tibialis anterior and rectus femoris muscles were recorded without a knee brace and with a brace applied with strap tensile force of 25 N, 50 N, and a force preferred by the subject. External compression caused by the brace significantly increased intramuscular pressures at rest and muscle relaxation pressure during exercise in the leg and thigh muscles. Pressure in the tibialis anterior muscle increased 3 to 10 times, to mean values between 17.5 and 41 mm Hg, depending on the tensile force of the straps used at brace application. Corresponding mean pressure values in the rectus femoris muscle were between 17.5 and 32.5 mm Hg. Mean pressures in the standing subject varied between 37 and 62 mm Hg. Our study showed that intramuscular pressure at rest and muscle relaxation pressure during exercise in the tibialis anterior and the rectus femoris muscles increased significantly in the braced limb. Local blood perfusion pressure in the supine subject decreased significantly, by 16% to 42%, in the compressed muscles.

Negative external pressure has been used previously in experiments on the blood circulation in humans and is currently being considered as a counter-measure to the musculoskeletal deconditioning which occurs during the exposure to microgravity. Intramuscular pressure (IMP) measurement is an important tool for determining the effectiveness of the transmission of negative pressure. Therefore two IMP techniques, a fibre optic transducer-tipped catheter and a fluid-filled teflon catheter with side holes, were evaluated using laboratory and human tests for measuring negative pressures. For the laboratory tests, both catheters were placed inside a lower leg negative pressure (LLNP) chamber and pressures of 0, -20, -50, -80, -100 and back to 0 mmHg were applied. Both catheters measured pressures equally and remained stable over 1 min at all pressure levels. When the teflon catheter was infused at rates commonly used for IMP recordings at normal atmospheric pressures, the drip rate at the catheter tip increased inversely with the magnitude of negative pressure. The cables and pressure tubings of the catheters within the LLNP chamber were not affected by the negative pressures. For tests in humans, the catheters were inserted side by side in the tibialis anterior muscle in eight legs of four human volunteers. The leg was placed in the LLNP chamber and pressures of 0, -20, -50, -80 and back to 0 mmHg were applied. The teflon catheter was used without infusion. Both catheters measured IMP similarly at rest and both remained stable over 1 min at all pressure levels; also the IMP during muscle contractions and immediately following contractions was similarly recorded by both catheters. We concluded that both catheter systems are suitable for recording negative pressures over a wide range. As is the case with recordings at normal atmospheric pressures, the fibre optic transducer-tipped catheter system may be preferred when recording IMP in a negative pressure environment when complex limb movements are involved.

The objectives of this study were to determine whether the occurrence of delayed onset muscle soreness (DOMS) for the vastus lateralis muscle was associated with elevated intramuscular pressure (IMP); and to assess, whether high eccentric forces occurred at an increased muscle length (as determined by joint angle). Therefore, peak knee extension torque, peak IMP of the vastus lateralis muscle, and the joint angle at which peak torque (JAPT) occurred were determined in eight male subjects during repetitive eccentric and concentric activities until fatigue occurred. Peak torque was significantly higher for eccentric compared to concentric activity (P < 0.01) and declined significantly for both activities (P < 0.01) throughout the protocols. When comparing the start (prior to fatigue) to the end (fatigue state), mean torque for eccentric activity declined from 191 to 147 (N.m) and for concentric activity declined from 166 to 104 (N.m). In contrast, peak IMP was not significantly different between the types of activity and did not change significantly with time. At the start and the end, the mean IMP remained constant for eccentric activity at 54 mmHg (7.2 kPa) but for concentric activity was 78 mmHg (10.4 kPa) and 96 mmHg (12.8 kPa), respectively. All the subjects, however, experienced DOMS of the vastus lateralis muscle exclusively for the eccentric activity leg. The JAPT was not different between activity types and did not change significantly with time; however, a significant interaction between activity type and time was observed (P = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of a functional knee brace on local intramuscular pressures and on calculated blood perfusion pressure in the tibialis anterior muscle of the legs of six volunteers were determined. Torque generation during dorsiflexion of the ankle joint was measured with a Kinetic Computerized ergometer, and the time to elicit muscle fatigue during exercise was recorded. For each experimental subject studies compared right with left unbraced legs, then right braced with left unbraced legs, and finally right unbraced with left braced legs. In the braced leg, intramuscular pressure at rest and muscle relaxation pressure during exercise were significantly higher, and the time to elicit muscle fatigue was 35% shorter. The calculated local blood perfusion pressure was lower because of the increased muscle relaxation pressure. We conclude that the increased muscle relaxation pressure during exercise caused by a knee brace is a possible explanation for the premature development of muscle fatigue in the braced leg.

The effect of three different functional knee braces on intramuscular pressures in the anterior compartment of the leg was investigated in 8 healthy subjects. Pressures were recorded with the microcapillary infusion technique while the subjects were either supine, sitting, or standing. Pressures at rest in the anterior tibial muscle increased significantly following application of each of the three knee braces regardless of posture. Similarly, muscle relaxation pressure during exercise also increased significantly on brace application. A pressure of 40 mm Hg was exceeded in 9 of 18 intramuscular pressure measurements with the subject standing. The tested functional knee braces increased muscle pressures at rest and muscle relaxation pressure during exercise to levels that, according to other studies, might decrease muscle blood flow significantly. External compression from a knee brace on leg muscles might, therefore, induce premature muscle fatigue because of local insufficient perfusion of the working muscle.

The efficacy of a modified fibre optic transducer-tipped catheter system for measuring intramuscular pressures during exercise was determined. A microcapillary infusion technique using a catheter was employed as the standard of comparison due to its established dynamic properties. Pressures were measured in the tibialis anterior muscle of six healthy adults at rest before exercise, during isometric and concentric exercise, and at rest after exercise. The fibre optic system measured contraction pressures equal to the microcapillary infusion technique during all phases of the exercise protocols but recorded a lower relaxation pressure during isometric exercise and a lower rest pressure following 20 min of concentric exercise. Negative relaxation pressures were recorded by the fibre optic system for two subjects during continuous concentric exercise. It is hypothesized that a piston effect, due to the sliding of muscle fibres at the catheter tip following a contraction, rendered falsely low pressures during relaxation and that this artefact was reflected in the subsequent rest pressure following exercise. The larger volume (157 mm3) and area (3.49 mm2) of the fibre optic catheter in the muscle made it more prone to this effect than the conventional catheter (39 mm3 and 0.87 mm2, respectively). The fibre optic system may be preferred when recording the muscle contraction pressures during complex limb movements but should not be used when assessing the relaxation pressures or the pressure at rest following exercise.

Laboratory and clinical tests were used to determine the efficacy of a new fiber optic "transducer-tipped" catheter for measuring intramuscular pressures. When pressures ranging from 0 to 250 mm Hg were applied by a mercury manometer, the fiber optic system accurately recorded the pressures. In addition, the fiber optic system showed long-term stability by accurately recording the manometer pressure over a 3 day period. The Slit system showed a higher magnitude of hydrostatic pressure artifacts with catheter tip movement as compared to the fiber optic system. The two catheters showed no difference when measuring pressures in pig muscle at rest or when being compressed throughout a range of 0 to 250 mm Hg. In human volunteers, both catheters measured essentially equal pressures at rest, during venous stasis, and during a combination of venous stasis and compression. For long-term assessment, the Slit system required as many as three saline flushes, whereas the fiber optic system measured pressures continuously without manipulation. We conclude that the fiber optic system is as accurate as the Slit catheter for measuring tissue fluid pressures at rest. In addition, the fiber optic system offers distinct advantages over conventional fluid-filled systems for measuring intramuscular pressures due to a lack of hydrostatic pressure artifacts caused by limb position and to the lack of flushing for long-term measurements.

Intramuscular pressures and muscle blood flow were measured in the anterior tibial muscle during dynamic concentric exercise in 14 subjects. Pressures were recorded by the microcapillary infusion method and muscle blood flow by the 133-Xenon clearance technique. Muscle blood flow during constant exercise decreased from 34.5 (SD = 10.3) to 10.6 (SD = 4.9) ml/100 g/min (P less than 0.001) when muscle relaxation pressure was increased from 13.5 (SD = 2.7) to 39.9 (SD = 9.0) mm Hg by external compression. Muscle relaxation pressure during exercise is the intramuscular pressure between contractions. External compression of the lower limb during exercise impedes muscle blood flow by increasing muscle relaxation pressure. The experimental model seems suitable to study the influence of external compression by knee braces on intramuscular pressure during exercise.

Intramuscular pressure was recorded in 28 patients with exercise-induced posteromedial pain in the lower leg. Pressure was recorded simultaneously in the posterior tibial muscle and in the flexor digitorum muscle during an exercise test and at rest after exercise. This study shows that intramuscular pressures during exercise and the time period for normalization of the pressure at rest after exercise were within normal limits. The result of pressure recording depends on which muscle in the deep posterior compartment is investigated and on the type of work performed. This article describes some of the difficulties associated with pressure recording in the deep posterior compartment. Chronic compartment syndrome in the deep posterior compartment as a reason for pain in the posteromedial part of the lower leg could not be demonstrated.

Shoulder pain correlated to manual labour is an increasing problem. The etiology is multifactorial and often unclear. High local muscle load and muscle ischemia in the supraspinatus muscle is present in elevated arm positions, as shown in several electromyographic studies. The purpose of this study was to evaluate intramuscular pressure (IMP) as a way to describe local muscle load in the supraspinatus muscle. Measurements were made in 15 arm positions, and with hand loads of 0, 1, or 2 kg weight, in 12 shoulders. The IMP was recorded with microcapillary infusion technique. The method was found to be suitable in recording IMP at rest and during exercise. High intramuscular pressures, i.e., above 50 mm Hg (6.7 kPa), were seen in moderate humeral abduction. The IMP increased further in abduction up to 90 degrees, where mean IMP was 122 mm Hg (16.2 kPa). Added hand load increased intramuscular pressure in all positions except in shoulder flexion of 135 degrees. The study thus demonstrated that intramuscular pressure offers important information about the load on the supraspinatus muscle in different positions of the arm. The results indicate that fatigue and shoulder pain related to elevated arm positions may be caused by muscle ischemia induced by the high intramuscular pressure present in these positions.

Intramuscular pressure was recorded in 80 patients suspected of suffering from chronic anterior compartment syndrome in the lower leg; the diagnosis was verified in 22 of these patients. The history and clinical findings of the chronic compartment syndrome patients were compared with those of the 58 patients without the syndrome. Pain induced only by athletic activity and only in the anterior lower leg forcing the patient to interrupt running indicated chronic compartment syndrome. The history and clinical findings alone were found to be insufficient to establish the diagnosis. In relation to generally accepted pressure parameters at rest, the muscle relaxation pressure during exercise was found to be a reliable parameter for diagnosing chronic compartment syndrome, whereas mean muscle pressure and muscle contraction pressure were found to be unreliable.

The microcapillary infusion method (MCI) is described and compared to the pump infusion (PI) and the wick catheter methods for recording pressure in the anterior tibial muscle at rest and during exercise in 34 volunteers and in 11 patients with chronic compartment syndrome (CCS). The infusion techniques offered excellent dynamic properties in recording pressure during exercise with infusion rates exceeding 0.1 ml/hour. Infusion rates below 3.0 ml/hour in normal legs and below 1.5 ml/hour in CCS legs were found not to increase the pressure at rest during 30 minutes. The wick catheter method was found to be unsuitable in recording intramuscular pressure during exercise because of its slow response time. The MCI method had a lower compliance, a higher resonance frequency, and a shorter response time than the PI method. The muscle relaxation pressure (MRP) during exercise increased to 34.6 (SD = 5.6) mmHg in the CCS patients during exercise compared to 17.3 (SD = 4.6) mmHg in the control group. The MCI technique offers a practical tool for studying equilibrium pressures during muscle contraction and relaxation in routine clinical investigations and research.

Clinical examination following an exercise test that elicits the symptoms of lower leg pain is most helpful in diagnosing the causes. Location of swelling, pain, impaired muscle function and impaired nerve function should all be analysed. History and clinical signs alone are insufficient to establish the diagnosis of chronic anterior compartment syndrome, and for this reason intramuscular pressure recordings have an important role in diagnosis. Different techniques for pressure recording and different pressure parameters are reviewed. Muscle relaxation pressure during exercise and intramuscular pressure at rest after exercise are the best parameters to study. Fasciotomy relieves pain in between 60% and 100% of patients. Closure of a fascial defect is never indicated, because it decreases the compartment size and may precipitate an acute compartment syndrome. Recording of nerve conduction velocity is a helpful complement in the diagnosis and evaluation of superficial peroneal nerve compression. Decompression by local fasciectomy and fasciotomy of the lateral compartment gives good results in more than 50% of patients. The value of periostitis as a clinical sign and the possibility of chronic pain following eccentric exercise are discussed.

The pressure in the subacromial bursa during passive provocation tests and during active motion was recorded in five healthy persons, and in seven patients with a subacromial pain syndrome. During the passive impingement test, the mean bursa pressure increased from 6 to 56 mmHg in healthy persons and from 8 to 45 mmHg in the patients. A passive test for anterior glenohumeral instability yielded bursa pressures below 0 mmHg in both groups. Active flexion of the arm at the shoulder produced a pressure increase up to 90° and a pressure decrease between 90 and 180° of flexion for both groups., (Copyright © 1988. Published by Elsevier Ltd.)

Fifteen patients with clinical signs that could indicate a chronic compartment syndrome of the first dorsal interosseous muscle of the hand were investigated by pressure recording at rest and during exercise. Objective data, verifying such a syndrome, were found in four of the patients. Increased muscle relaxation pressure during exercise and intramuscular pressure at rest after exercise compared with normal pressure were well correlated to the development of the symptoms of chronic compartment syndrome. Fasciotomy of the first dorsal interosseous muscle relieved the symptoms and normalized the pressure.

Recording of intramuscular pressure by using the injection technique in different ways has been evaluated in 12 healthy subjects and 12 patients with medial tibial syndrome. Pressure recording with an injection needle was compared to the recording by a Teflon catheter with multiple side holes at its tip. Following an injection of 0.07 ml, the intramuscular pressure was significantly higher when it was recorded with the injection needle. Pressure recorded with an injection needle by the "meniscus method" was found to be significantly closer to the preinjection pressure compared to the injection technique described by Whitesides et al. Pressure readings by the "meniscus method" after injection, and by a catheter or needle with multiple side holes, decrease the drawbacks of the injection technique.

Intramuscular pressure in the anterior tibial compartment and calf circumference were measured daily during six days following reconstructive surgery for lower limb atherosclerosis in 31 patients. Both intramuscular pressure and calf circumference were significantly increased in the operated extremity from the first postoperative day. Maximum intramuscular pressure was found on the second postoperative day. No patient developed a compartment syndrome. Calf circumference increased more slowly and reached maximum on the fifth postoperative day. Following successful reconstructive arterial surgery intramuscular pressure and calf circumference increased most in patients undergoing dissection of the groin and leg, probably reflecting intraoperative damage of lymphatic vessels. In four patients where the reconstructive arterial surgery failed intramuscular pressure and calf circumference remained unchanged postoperatively despite dissection of the groin and leg. Thus, the present study suggests that both impaired lymphatic drainage and increased capillary filtration contribute to the development of increased intramuscular pressure and calf circumference following reconstructive arterial surgery of the leg.

The microcapillary infusion (MCI) technique was evaluated in monitoring pressure in the subacromial bursa in 30 shoulders in healthy volunteers. The total pressure in the bursa was studied as the volunteers held their arms at rest and as they lifted their arms and held them lifted with or without a weight of 1 kg in the hands. The pressure in the bursae at rest averaged 8 mm Hg and was found stable during a 40-min period. When the arms were lifted, the average bursa pressure increased from 8 to 39 mm Hg. As the arms were held up, the weights were put in the hands, and the average bursa pressure then further increased to 56 mm Hg. When the infusion catheters were repeatedly flushed, during a period of 5 min and with a total of 1.2 ml of saline, the average bursa pressure doubled regardless of arm position and load in the hands. The compliance of the bursae decreased from 0.09 to 0.04 ml/mm Hg when the arms were lifted and from 0.04 to 0.02 ml/mm Hg when the arms were lifted and the hands were loaded. The MCI method was found suitable for recording pressure in the subacromial bursa during exercise.

Our objective was to compare two techniques for measuring intramuscular pressures during dynamic exercise. In 20 volunteers muscle contraction and relaxation pressures were recorded with a noninfusion method (slit catheter) and with a microcapillary infusion method (Myopress catheter). Relaxation pressures measured by noninfusion were higher than those measured by infusion. The dynamic properties of the infusion method were higher as compared with the noninfusion method. The dynamic properties of the noninfusion method increased when microcapillary infusion was connected. This resulted in a lower recording of the muscle-relaxation pressure than without infusion. We concluded that the microcapillary infusion technique and the design of the tip of the Myopress catheter are better suited for pressure recordings during exercise.

Intramuscular pressure and muscle blood flow was measured in the supraspinatus muscle in 6 healthy subjects. The recordings were performed at rest, during isometric exercise, during an isometric muscle contraction of 5.6 kPa (42 mm Hg) and 10.4 kPa (78 mm Hg) and at rest after the contraction. Intramuscular pressure was measured by the microcapillary infusion technique, and muscle blood flow by the Xenon-133 washout technique. Intramuscular pressure was 38.2 kPa (SD 12.0) (287 mm Hg) during maximal voluntary contraction. A muscle contraction pressure of 5.6 kPa (42 mm Hg), which is 16% of maximal voluntary contraction, reduces local muscle blood flow significantly. It is concluded that the high intramuscular pressures found in supraspinatus during work with the arms elevated impedes local muscle blood flow.