Effect of lower extremity muscular fatigue on motor control performance.

PURPOSE: The purpose of this study was to determine whether lower extremity fatigue affects the ability of an individual to balance on an unstable platform. METHODS: Twenty healthy subjects (average age, 29 yr, range, 20 to 39 yr) were tested on an instrumented balance assessment system. Static tests were done on the limbs unilaterally and then bilaterally, and finally a dynamic test was performed in which the subject moved the platform in a circular manner to chase a moving object on a computer screen. After testing, subjects were fatigued using an isokinetic dynamometer, which imposes closed kinetic chain antagonistic exercise on the ankle, knee, and hip, similar to a stair stepper. No rest was allowed, and subjects were fatigued to less than 50% of their initial tested force. Subjects were then immediately retested on the unstable platform using the same testing protocol. All subjects completed the testing. RESULTS: Analysis of pre- and post-fatigue balance results demonstrated significant decreases in motor control performance on the three static tests following exercise to fatigue in all subjects (P < 0.001). CONCLUSIONS: Our findings support anecdotal evidence that fatigued individuals are at increased risk of injury because of loss of balance. Avoidance of fatigue and preconditioning may prevent injury.

A review of selected noncontact anterior cruciate ligament injuries in the National Football League.

During five football seasons, from 1989 through 1993, 61 surgically proven, noncontact, anterior cruciate ligament injuries, were identified from among 22 National Football League teams. The variables of surface, shoe type, playing conditions, and whether or not the shoe was spatted were identified for each reported injury. Forty noncontact injuries occurred in conventional cleated shoes on natural grass, and 21 occurred on an artificial surface. Almost half of all injuries (47.5%) occurred during game-day exposures despite the fact that the practice versus game-day exposure rate was 5:1. Of these injuries, 95.2% (N = 58) occurred on a dry field. The factors of cleat and shoe type, type of surface (natural versus artificial), surface conditions (wet/dry), and the effect of "spatting" a shoe are presented. The significance of these factors and their likelihood to be associated with injury is analyzed by use of a statistical tool, the incidence density ratio.

Differences in friction and torsional resistance in athletic shoe-turf surface interfaces.

This study evaluated the shoe-surface interaction of 15 football shoes made by 3 manufacturers in both anterior translation and rotation using a specially designed pneumatic testing system. The shoes included traditional cleated football shoes, "court" shoes (basketball-style shoes), molded-cleat shoes, and turf shoes. Under an 11.35-kg (25-pound) axial load, all shoes were tested on synthetic turf under wet and dry conditions and on natural stadium grass. Test-retest reliability, as calculated using the Pearson Product-Moment Correlation test, was 0.85 for force of translation and 0.55 for the moment of rotation. The wet versus dry surface values on translation were significantly different for rotation about the tibial axis. Spatting, which is protective taping of the ankle and heel applied on the outside of the shoe, resulted in a reduction of forces generated in both translation and rotation. No overall difference between shoes on grass versus AstroTurf was noted. However, there were significant differences for cleated and turf shoes. Shoes tested in conditions for which they were not designed exhibited reproducible excessive or extreme minimal friction characteristics that may have safety implications. On the basis of this study, we urge shoe manufacturers to display suggested indications and playing surface conditions for which their shoes are recommended.

Bone-patellar tendon-bone grafts for anterior cruciate ligament reconstruction: the effects of graft pretensioning.

Viscoelastic creep is a well-known phenomenon associated with collagenous soft tissues under sustained tensile load. Despite our understanding of this phenomenon and the potential for "loosening" of the graft over time, pretensioning of bone-patellar tendon-bon (B-PT-B) grafts for reconstruction of the anterior cruciate ligament (ACL) to eliminate this elastic deformation is not commonly practiced. This investigation quantified viscoelastic creep in B-PT-B grafts using both an in vivo and an in vitro model. In vivo, 10-mm B-PT-B grafts were procured and prepared in a standard manner for arthroscopically assisted ACL reconstruction. A total of 153 grafts were evaluated. During preparation, each graft was tensioned using a commercially available graft preparation board (Smith & Nephew DonJoy). An initial tensile load of 2.25 N (0.5 lb) was applied to the graft and a measurement was taken between bone-tendon junctions at either end. A sustained load of 89 N (20 lb) was then applied for a minimum of 4 minutes and the measurement repeated. In the in vitro model, grafts were harvested in a standard manner, then placed in a servohydraulic for tensile loading. A differential variable reluctance transducer was implanted in each graft to quantify net displacement during 15 minutes of sustained tensile loading at 89 N (20 lb). A total of 13 specimens were evaluated. In the in vivo model, mean pretension bone-tendon junction length was 43.6 mm (range, 29 to 64 mm; SD, +/- 6.7). Mean post-tension bone-tendon length was 49.6 mm (range, 33 to 71 mm; SD, +/- 7.1), representing a mean increase in length of 6.0 mm (range, 2 to 12; SD, +/- 2.1) or 14.0% (range, 3.8 to 28.6; SD, +/- 5.2). In the in vitro model, the mean pretension tendon length was 42.81 m (range, 35.20 to 51.48; SD, 4.54). The mean post-tension length was 47.11 mm (range, 38.05 to 56.23; SD, +/- 5.04) representing a mean increase of 4.30 mm or 10.12%. These data would seem to support the hypothesis that without pretensioning, significant postimplantation graft creep will occur.

Early motion after repair of Achilles tendon ruptures.

The purpose of this study was to evaluate the clinical outcome of patients treated with limited immobilization and early motion after repair of acute Achilles tendon ruptures. Thirteen consecutive patients with complete ruptures of the Achilles tendon were identified, repaired, and rehabilitated with early motion starting an average of 10 days after surgery. Active range of motion was begun at an average of 23 days and weightbearing in a walking boot was started at an average of 3.5 weeks after surgery. The average length of follow-up was 27 months. Twelve of 13 patients returned to running activities in an average of 3 months. All 12 patients who participated in lateral motion activities before their injury returned to similar activities in an average of 7 months. The patients rated their overall status at an average of 93% of their preinjury level. Follow-up Cybex testing demonstrated plantarflexion strength averaging 92%, plantarflexion power averaging 88%, and plantarflexion endurance averaging 88% of the nonindexed extremity. Early range of motion after Achilles repair is safe and there is no increased risk of rerupture in compliant patients. The patients achieved good return of plantarflexion strength, power, and endurance.

[Dosage reduction of d-phe-6-GnRH for the regulation of ovulation by complexation with polyglycine]. / Dosisminderung von D-Phe6-GnRH bei der Ovulationsregulierung durch Komplexierung mit Polyglycin.

The gonadotropin-releasing-hormone analogue D-Phe6-GnRH was complexed with polyglycine under non-denaturing conditions. The liberation behaviour of these complexes was investigated in vitro in dependence of hormone content. The "effective dose 50" (ED 50) could be decreased by factor 34 in vivo in mouse ovulation test by reason of protection effect of polyglycine for the hormone against untimely proteolytical degradation.

[Scintigraphy of sustained-release agar-embedded insulin suppositories]. / Szintigraphische Verfolgung der retardierten Insulinliberation aus Agar-Einbettungen in Suppositorien.

In earlier publications [1-3] we reported on the retardation and protective effect of insulin-agar-embeddings in triglyceride suppositories by in vitro and in vivo tests on rabbits. The discovered effects were visually followed by gammascintigraphic test of adequate rectally applied 131I-insulin-specimens in the rectum and thyroid gland and, in relation with the glucose lowering course, the liberation, distribution and bioavailability of the immobilized hormone was illustrated.

[The application of insulin-agar embedding in suppositories for controlled hormone liberation and dose lowering]. / Uber die Verwendung von Insulin-Agar-Einbettungen in Suppositorien zur verzögerten Hormonliberation und Dosissenkung.

By embedding of insulin in agar a significant retardation as well as a protective effect for the hormone is obtained. As demonstrated on in vivo animal experiments, this embedding method in dependence on the insulin concentration and particle size of the polymeric matrix allows to prepare rectal insulin applications with remarkable depot effects. Alternatively in combination with resorption promoting tensides it permits to lower the administered hormone doses to a order of magnitude reaching those used for parenteral insulin applications.

[Insulin polyamino acid complexes--a variable principle in the preparation of sustained-release forms]. / Insulin-Polyaminosäure-Komplexe--ein variationsfähiges Prinzip zur Gewinnung von Verzögerungsformen.

Polyglycine, polyalanine, polyleucine, poly-alpha-glutamic acid, poly-gamma-glutamic acid and poly-alpha-lysine were complexed with insulin under non denaturating conditions. The liberation behaviour of the hormone was investigated in vivo and in vitro in dependence of the insulin content, mole mass, ionic interaction and hydrophobicity of the polyamino acid. The in vitro results were mainly confirmed by animal experiments and indicated distinct effects of the physiochemical parameters to the bioavailability of insulin. The complex of poly-alpha-lysine and polyglycine were shown to be the most suited retard form, producing significant blood glucose lowering effects up to 12 hours.

[Studies on the liberation behavior of insulin from polymeric matrices]. / Untersuchungen zum Freisetzungsverhalten von insulin aus polymeren matrices.

The in-vitro and in-vivo liberation of insulin from embeddings in polymeric matrices was investigated dependent on the charging degree, the particle- and pore size, respectively, of the granules and the dissolution behaviour of the hormone. Polyacrylamide, agar-agar, dextrane and Sephadex G-100 were used as ground-mass. These polymers are characterized by a good swelling and a high binding capacity. If these properties quality them for insulin was investigated in model experiments. Information concerning the obtained retention effects of the matrix mould were produced by photochemical methods (application of insulin against citrate phosphate buffer; absorption region of 230 to 320 nm). The in-vitro effects yielded could be confirmed by means of representative in-vivo studies in eumetabolic insulin sensitive rabbits.

Instrumented measurement of anterior laxity of the knee.

We performed instrumented measurement of anterior-posterior laxity of the knee in thirty-three cadaver specimens, 338 normal subjects, and eighty-nine patients with unilateral disruption of the anterior cruciate ligament. The test instrument was the Medmetric knee arthrometer, model KT-2000. We measured total anterior-posterior laxity, produced by anterior and posterior loads of eighty-nine newtons (twenty pounds), and the anterior compliance index. The total anterior-posterior laxity is composed of an anterior displacement and a posterior displacement; these are measured from a testing reference position, defined as the resting position of the knee after applying and then releasing a posterior load of eighty-nine newtons. The anterior compliance index is defined as the anterior displacement between an anterior load of sixty-seven newtons and one of eighty-nine newtons. All tests were performed with the knee held on a thigh support that placed the knee in 20 +/- 5 degrees of flexion. The mean anterior displacement at eighty-nine newtons was 5.7 millimeters in a group of normal subjects and 13.0 millimeters in a group of patients with a disrupted anterior cruciate ligament. Ninety-two per cent of the normal subjects had a left knee-right knee difference in anterior displacement of no more than two millimeters, while 96 per cent of the patients with a unilateral disruption of the anterior cruciate ligament had an injured knee-normal knee difference in anterior displacement of more than two millimeters. Ninety-three per cent of the normal subjects had a difference in the left-right compliance index of no more than 0.5 millimeter, and 85 per cent of the patients with unilateral disruption of the anterior cruciate ligament had a difference in the compliance index of the injured and normal sides of more than 0.5 millimeter.

The effect of continuous passive motion on anterior cruciate ligament reconstruction stability.

This study was undertaken to examine the immediate effect of continuous passive motion (CPM) on anterior cruciate ligament (ACL) reconstruction stability. Cadaver knees were tested with a knee arthrometer with the anterior cruciate intact and then with the anterior cruciate sectioned. One of three anterior cruciate reconstructions was then performed and stability was restored to the knee and it was again tested with the knee arthrometer. Stability was defined as being within 2 mm of the intact measurement. The three operations selected were the Marshall-MacIntosh "over-the-top," (OTT) a patellar bone-patellar tendon-tubercle bone (BTB) graft, and a semitendinosis reconstruction. The specimens were placed on a CPM device in a cooler at 38 degrees F and put through a range of motion of 20 to 70 degrees at 10 cycles per minute for 3 days. A success was less than a 2 mm increase in the post-CPM measurement compared to pre-CPM. All three bone-tendon-bone operations failed. The semitendinosis operation was successful in only three out of eight specimens. The OTT operation was successful in eight out of nine specimens. The possible reasons for success and failure are discussed. Because of the potential problems with failure of an ACL with CPM it is suggested that the particular technique being used for an anterior cruciate reconstruction be tested prior to it being used with CPM clinically.

Hydrogenolytic debenzylation of sulfur-containing peptides.

S-protected cysteine derivatives are desulfurized by hydrogenation with Pd/H2 forming inhibiting thiols and alanine derivatives. In the case of protected cysteine peptides, this inhibition effect may be suppressed by adding BF3-etherate, the extent of suppression depending on the position of the cysteine and on the sequence length of the peptide derivative. With sufficient sequence distance from the cysteine sulfur, benzyl type protecting groups may be quantitatively removed from the cysteine sulfur by means of hydrogenolysis.

Active fragments of native streptokinase obtained by partial tryptic degradation.

By partial tryptic digestion of streptokinase, degradation products of the molecular weight range 27 000--42 000 were obtained. Among these, fibrinolysis activating components could be demonstrated.