Citations

This paper examined the feasibility of using different optimization criteria in inverse dynamic optimization to predict antagonistic muscle forces and joint reaction forces during isokinetic flexion/extension and isometric extension exercises of the knee. Both quadriceps and hamstrings muscle groups were included in this study. The knee joint motion included flexion/extension, varus/valgus, and internal/external rotations. Four linear, nonlinear, and physiological optimization criteria were utilized in the optimization procedure. All optimization criteria adopted in this paper were shown to be able to predict antagonistic muscle contraction during flexion and extension of the knee. The predicted muscle forces were compared in temporal patterns with EMG activities (averaged data measured from five subjects). Joint reaction forces were predicted to be similar using all optimization criteria. In comparison with previous studies, these results suggested that the kinematic information involved in the inverse dynamic optimization plays an important role in prediction of the recruitment of antagonistic muscles rather than the selection of a particular optimization criterion. Therefore, it might be concluded that a properly formulated inverse dynamic optimization procedure should describe the knee joint rotation in three orthogonal planes.

This study analyzed forces in the tibiofemoral and pa tellofemoral joints during isokinetic exercise using an analytical biomechanical model. The results show that isokinetic exercise can produce large loads on these joints, especially during extension exercises. The tibio femoral compressive force (4.0 body weight) is approx imately equal to that obtained during walking but it occurs at 55° of knee flexion. Anterior shear forces (resisting force to anterior drawer) exist during exten sion exercise at less than 40° of knee flexion, with a maximum of 0.3 body weight. Posterior shear forces (resisting force to posterior drawer) exist during exten sion exercise at knee joint angles greater than 40° and during the flexion portion of isokinetic exercise. The maximum posterior shear force is 1.7 body weight. The patellofemoral joint can encounter loads as high as 5.1 body weight which are 10 times higher than during straight leg raises. These results suggest that isokinetic exercise should be used cautiously in patients with knee lesions.

Golf is an activity generally stressful to the hands and wrists and particularly can produce increasing symp toms in players with underlying problems such as hand and wrist arthritis or tendinitis. The purpose of this study was to quantitate wrist motion and club head/ ball impact force in subjects with pathologic conditions of the hand, wrist, or forearm, within a laboratory environment. A regular straight-handled golf club was compared to a new BioCurve handle design that has a 19° ulnar bend. We measured and compared the effect of the two grips on wrist motion, club head velocity, ball impact force, ball impact location, and isometric torsional strength in 20 subjects who had a variety of upper extremity disorders. This data was then com pared to data collected in an identical fashion from golfers without such conditions. The results of our study show that there were no differences related to club handle design on impact force or impact location, club head velocity, or club head path and face angle. Wrist kinematic differences were minimal between handle designs. The differences that were significant (P < 0.05) centered around the decreased ulnar deviation of the left hand that resulted when subjects used the BioCurve handle design, which also allowed greater resistance to torque than the straight grip club. In addition to collecting objective data, we asked subjects for their opinions of the two grips. As a whole, the normal group and the group with pathologic conditions noted more comfort, improved grip, and less shock transmission with the BioCurve handle.

The purpose of this study was to investigate the rela tionship of isometric and isokinetic endurance of the forearm complex under maximum effort in a healthy population. Isometric and isokinetic endurance meas urements of elbow flexion and extension of the domi nant and nondominant sides were made in 32 healthy male subjects (age range, 21 to 39 years). Both fatigue rates and the amount of time elapsed in reaching fatigue were determined. Analysis of these data reveals that 1) isometric endurance of the forearm complex cannot be used as a predictor of isokinetic endurance, as there is no relationship between the two, 2) dominant and non dominant endurance are related, a result that supports the belief that in the assessment of the endurance of a single diseased upper extremity, the best available comparison is with the contralateral healthy extremity, and 3) healthy males in the age range tested have greater endurance in elbow extension than in flexion.

Eighteen junior elite figure skaters were filmed while performing axel and double axel jumps. These same skaters were assessed for strength of the shoulders, knees, and hips at multiple angular velocities using a Cybex II system. The height of the jumps was signifi cantly correlated with the strength data. Knee exten sion at 240 deg/sec and shoulder abduction at 300 deg/sec were shown to be the most important strength parameters in determining the height of the jump. This information may be useful for designing strength train ing programs for figure skaters.

The practice of prophylactic ankle taping or wrapping to reduce the incidence of inversion ankle sprains in athletes has come under attack. The purpose of this study was to measure objec tively one ankle taping technique's ability to withstand the stresses placed upon it by a standardized exercise routine. Electrogoniometers were used to measure the three-dimen sional ankle motion of 20 subjects walking on a level surface and a 10° sideslope. The evaluations were carried out under these three conditions: (1) both ankles untaped, (2) both ankles taped before exercises, and (3) both ankles taped after exercise. The results from this study indicate that the tape does indeed restrict those motions associated with inversion ankle sprain. Methods similar to those described in this study could be used in the evaluation of many current training room practices and thereby provide an objective rationale for their application.

A fracture healing monitoring system with external fixators was analysed using the finite element method. Pin displacement and side bar strain under axial and side loading were evaluated at various stages of simulated fracture healing. In general, a recovery of rigidity at the fracture site of up of 25 percent of intact bone could be sensitively predicted. Effects of cross-sectional distribution and length of callus at the fracture site on pin displacement and side bar strain were studied. Alterations of fixation configuration, such as component failure during the healing process, were found to have relatively little effect on pin displacement but a rather larger effect on side bar strain. In general, the assessment of fracture healing by monitoring the deformation of external fixation devices is a useful idea. However, in practice, great care must be taken to fully understand the implication of the monitoring system before drawing conclusions on such measurements.

Genome-wide variance components linkage analysis was performed on 4 latent factors underlying metabolic syndrome derived from 10 risk factors. The latent factors represent obesity and insulin, blood pressure, lipids and insulin, and central obesity. The metabolic syndrome factor scores were derived in 4 ethnic groups recruited in 3 Networks of the Family Blood Pressure Program: GENOA (blacks, Hispanics, and whites), HyperGEN (blacks and whites), SAPPHIRe (Asians). Heritabilities of metabolic syndrome factors ranged from 66% for obesity and insulin to 11% for blood pressure factor. We observed higher heritabilities for obesity and insulin, and lipids and insulin, whereas those for blood pressure and central obesity were smaller. Linkage analysis detected two major quantitative trait loci. One of them linked to the obesity and insulin factor with a lod score of 3.94 ( P =0.00001, marker GATA11A06, D18S53, 41.24 cM) at marker positions linkage (lod 4.71, at 46.84 cM at 1-cM-apart distances linkage), located on chromosome 18p11.21 in GENOA black. The other linked to the blood pressure factor with a lod score of 3.22 ( P =0.000059, marker GATA49C09, D17S1290, 82 cM) at marker positions linkage (lod 3.56, at 84.63 cM for 1 cM apart distances linkage) located on chromosome 17q23.1 in Hispanics. These quantitative trait loci, together with 4 additional ones with lod scores >2.5, and 30 additional ones with lod score >1.7, offer hope for dissecting the genetic architecture of metabolic syndrome with beneficial implications for molecular diagnosis, prognosis, and in potential medical intervention.