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Biomedical subjects

E C Frederick

Publications and source records attributed to E C Frederick.

13 recordsLinked to original sources
PubMed1992

Mechanical constraints on Nordic ski performance.

Skiers, coaches, and sports scientists must work within mechanical constraints to improve performance. If Nordic skiing is to be improved by mechanical means, it will be achieved by affecting one or more of the major constraints: gravity, mass, friction, aerodynamic or hydrodynamic lift and drag, and centripetal force. For example, the skier who assumes a tucked position, drafts a competitor, and wears a drag-reducing hood and body suit is reducing aerodynamic constraints. Sliding friction may also be reduced by using specially prepared skis and by selecting skis appropriate for the snow characteristics of the race course. Skin friction hydrodynamic drag may also be affected by ski selection and by special base preparations. Gravity and mass constraints are diminished by using lightweight components, by carrying them in the least costly way, and by minimizing swing weight. The toppling effect of centripetal forces is addressed by leaning into turns. All of these examples address mechanical constraints in a way that reduces physical power requirements, and thus decrease the metabolic power required to ski at a given speed, as well as increasing the maximal speed attainable.

Biomechanical Phenomena↗
PubMed1987

Groucho running.

An important determinant of the mechanics of running is the effective vertical stiffness of the body. This stiffness increases with running speed. At any one speed, the stiffness may be reduced in a controlled fashion by running with the knees bent more than usual. In a series of experiments, subjects ran in both normal and flexed postures on a treadmill. In other experiments, they ran down a runway and over a force platform. Results show that running with the knees bent reduces the effective vertical stiffness and diminishes the transmission of mechanical shock from the foot to the skull but requires an increase of as much as 50% in the rate of O2 consumption. A new dimensionless parameter (u omega 0/g) is introduced to distinguish between hard and soft running modes. Here, omega 0 is the natural frequency of a mass-spring system representing the body, g is gravity, and u is the vertical landing velocity. In normal running, this parameter is near unity, but in deep-flexed running, where the aerial phase of the stride cycle almost disappears, u omega 0/g approaches zero.

Adult↗
PubMed1986

Kinematically mediated effects of sport shoe design: a review.

One prominent pattern emerging from a review of the literature on sport shoes and biomechanics is the observation that many effects are the indirect result of shoe-induced adjustments in movement, i.e. a particular shoe characteristic elicits a kinematic adaptation which in turn has secondary consequences on kinetics and on injury and performance. For example, in addition to its variable effects on peak forces, cushioning system design has been shown to alter electromyographic patterns and to affect knee flexion during foot strike and affect indirectly the economy of running. Mediolateral stability as measured by rearfoot kinematics is strongly influenced by shoe design features such as heel lift, and sole hardness and geometry. The frictional properties of the shoe and surface interface have also been shown to affect kinematics in a way that in turn affects the recorded frictional forces themselves. Such kinematically mediated responses are the most provocative result of studies of the biomechanical effects of footwear. It is becoming apparent that the shoe can be a powerful tool for manipulating human movement. The abundance of shoe design possibilities coupled with the body's tendency to adjust in predictable ways to shoe mechanical characteristics have given us a new way to manipulate human kinematics and kinetics, as well as a convenient model for studying biomechanical adaptation.

Ankle Joint↗
PubMed1986

Systematic ankle stabilization and the effect on performance.

Stabilization of the ankle joint is used as a deterrent to injury, however, insufficient or excessive ankle control can cause negative effects. This study determined the effects of systematic changes in ankle and subtalar joint stabilization on performance through an obstacle course. Data were collected on six subjects as they completed two test procedures. Ankle range of motion in the sagittal and frontal planes was determined using a modified Inman apparatus. Completion time through an obstacle course, set up on a basketball court, was used as a measure of performance. High-top basketball shoes were constructed with pockets which allowed strips of plastic (stiffeners) to be positioned just anterior and posterior to the medial and lateral malleoli. Four shoe conditions were used including the shoe with no stiffeners. Significant differences (P less than 0.05) in eversion, flexion, and inversion were found between the shoe conditions. A general trend of decreased range of motion with increased restriction was observed. Significant differences (P less than 0.05) in performance were found between the shoe conditions, with a general trend of increased times with increased restriction. These results indicate that systematic changes in the range of motion of the ankle and subtalar joints can measurably affect performance.

Adult↗
PubMed1985

Synthesis, experimentation, and the biomechanics of economical movement.

An issue that should concern sports biomechanists is the need for more synthesis of ideas and experimental testing of those ideas. Descriptive analysis is overemphasized at present, and more stress on synthesis of existing data and experimental testing of new ideas should generate new theories that will give us insights into the mechanical behavior of structures and the kinetics and kinematics of sports movements. One area where this approach may be especially helpful is in studying the question of what makes movements energetically economical. Twenty-six behavioral and mechanical factors have been shown to have an association with the economy of movement. A synthesis should be undertaken which probes the meaning of these various data. Trends in these findings point to intra- and intersegmental energy transfer, center of mass excursion, and elastic energy storage as potential areas for expanding our understanding of the biomechanics of economical movement. These possibilities might be explored by enhancing link-segmental mathematical models to predict what makes movements economical and then testing these predictions by using biofeedback techniques to train subjects to perform the correct movements while being monitored. Optimization models might offer an additional strategy for developing a theory of mechanically and energetically economical movement.

Biomechanical Phenomena↗
PubMed1983

Effects of shoe cushioning upon ground reaction forces in running.

To determine the effects of widely varying amounts of cushioning upon vertical force (VF) parameters, ten male subjects, (mean weight = 68.0 kg) ran at a speed of 4.5 m . s-1 (6 min/mile pace) and contacted a Kistler force platform. Two shoes were tested: a hard one and a softer shoe that had 50% more cushioning as measured by an instrumented impact tester. Five right footfalls were collected for each shoe on each subject during which the ground reaction forces were sampled at 500 HZ using a PDP 11/34 minicomputer. Eight parameters from the VF data obtained for each trial were selected for analysis and compared statistically using a paired difference t test. It was found [force magnitudes expressed in multiples of body weight (BW)] that the time to the vertical force impact peak (VFIP) was significantly longer (hard = 22.5 ms, soft = 26.6 ms) in the soft shoe; however, no differences were seen in the magnitudes (hard = 2.30 BW, soft = 2.34 BW). The minimum after the VFIP was also significantly delayed in the soft shoe (hard = 33.8 ms, soft = 37.9 ms) and was significantly greater in the soft shoe (hard = 1.46 BW, soft = 1.90 BW). The peak VF propulsive force occurred statistically at the same time in both shoes (hard = 85.7 ms, soft = 84.0 ms), but was significantly greater in the soft shoe (hard = 2.73 BW, soft = 2.83 BW).(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1983

The effects of shoe design parameters on rearfoot control in running.

Control of the amount and/or rate of pronation of the foot which occurs during distance running has been cited as an important consideration for runners when selecting a running shoe. In this study, high-speed movie film was taken from the rear while 10 subjects ran on a treadmill at a pace of 3.8 m X s-1. These subjects wore 36 different shoes in combinations of three midsole hardnesses, three heel flares, and four heel heights. The film data were digitized and used to determine the eversion or inversion of the heel relative to the lower leg throughout foot contact. Because eversion of the foot is a component of pronation it was used as a predictor of how much pronation was occurring. It was found that shoes with soft midsoles (25 durometer, Shore A scale) allowed significantly more maximum pronation (MP) and total rearfoot movement (TRM) than shoes with either medium (35 durometer) or hard (45 durometer) midsoles. Shoes with 0 degrees heel flare allowed significantly more MP and TRM than shoes with either 15 degrees or 30 degrees heel flares. Heel height was found to have no significant effect on either MP or TRM. These data provide guidelines for the construction of running shoes designed to limit rearfoot movement.

Biomechanical Phenomena↗
PubMedDate not supplied

Effect of shoe cushioning on the development of reticulocytosis in distance runners.

We studied erythropoietic activity in relation to the rearfoot cushioning of shoes worn by 14 male runners before, during, and the morning after a 17-day period of increased training mileage. The percentage of reticulocytes in the red blood cell count (normal, less than 0.8%) served as the marker for erythropoietic activity. Each runner was assigned to either a firm-sole group (7) or a soft-sole group (7) according to the heel impact attenuation character (Peak g) of his shoes. Peak g was 18% greater in the firm-sole group (P less than 0.001). Otherwise, the groups were similar in physical characteristics, training mileage, and running ability. All subjects ran a total of 430 km, a distance that averaged 79% higher than their regular training distance for a 17-day period. Resting blood samples were obtained at baseline and on three mornings (Days 11, 13, and Day 18, which followed the completion of the increased training period). No significant differences were found between the groups in red blood cell count, hematocrit, or total hemoglobin, haptoglobin, plasma-free hemoglobin, and serum ferritin levels. The groups did not differ in percent reticulocytes at baseline (0.2% firm-sole versus 0.2% soft-sole), on Day 11 after running 280 km (0.8% firm-sole versus 0.8% soft-sole), or on Day 13 after 48 hours of rest (1.3% firm-sole versus 1.0% soft-sole). However, on Day 18 after running 430 km, reticulocyte counts were 29% higher (P less than 0.05) in firm-sole than soft-sole (2.2% versus 1.7%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗