BIOMECHANICAL INVESTIGATIONS OF PERFORMANCE CHARACTERISTICS OF VARIOUS TYPES OF ICE HOCKEY STICKS

INTRODUCTION: The primary non-skating skills employed in ice hockey all involve use of a hockey stick to some degree. The importance of the stick is obvious in offensive skills such as shooting and passing. It is less obvious but equally important in defensive skills such as checking and face-offs. The selection and use of a stick depends on several factors which vary according to the level of hockey an individual is playing and on the skill level of the player. Cost, appearance, feel, performance, and durability are all areas that might be considered by various players. However, for those performing at elite levels feel and performance are likely the most significant factors. The stick must feel right in the hands before a player will consider using it and it must perform up to required standards in skills such as shooting and passing. The variables contributing to how a hockey stick feels and performs include primarily: weight, centre of mass location, shaft flex, resistance to twist, and breaking force. Together, these factors will determine the success of a manufacturer in promoting and selling a particular model. At present, there are three primary types of ice hockey stick. The traditional stick is made of wood with a wooden blade being glued to a wooden shaft. Variants include fibreglass wraps that cover the blade or perhaps layers of laminated wood and fibre glass pressed into the shaft. A second type of stick incorporates a hollow aluminum tube (perhaps filled with foam to dampen vibrations) into which a wooden or composite blade is inserted at one end and a wooden plug at the other end. When the blade breaks it is replaced by another without the necessity of discarding the shaft. The third type of hockey stick is similar to the aluminum tube except that it consists of a hollow tube comprised of composite materials such as graphite and kevlar. These materials are combined with resins and fibreglass to form a shaft into which a blade and a plug are inserted. At amateur levels of play all types of sticks are in common use. At the professional level, aluminum sticks have been phased out over the past two years and with the rare exception all players use either wooden or composite graphite sticks. The differences between the three types of sticks that might contribute to performance and Afeel≅ have been a topic of concern for manufacturers of hockey sticks for the past several years. Baseline information on stick and shaft characteristics is important to future design and modifications of hockey sticks. Therefore, it was the purpose of this study to evaluate characteristics of various types of hockey stick shafts that contribute to the feel and performance capacity of the stick. Professional hockey players and highly skilled amateurs select sticks intuitively on the basis of Afeel≅. In this study, large samples of wood (N = 40), aluminum (N = 32), and composite (N = 55) hockey sticks were evaluated for the following characteristics: weight, centre of mass, flex strength, torsional resistance, and breaking force. Although the sticks were sampled from several manufacturers, the test protocol followed a standard procedure used by Louisville Hockey to test for performance characteristics and quality control

BIOMECHANICS OF NORMAL AND ANTERIOR CRUCIATE LIGAMENT DEFICIENT GAIT UNDER BRACED AND UNBRACED CONDITIONS

The anterior cruciate ligament (ACL) performs an important role in stabilizing the knee joint during gait. However, little research has examined the effect of ACLdeficiency on gait mechanics. Furthermore, the mechanics of braced ACL-deficient gait remain unclear. The purposes of this study were to evaluate the running mechanics of normal and ACL-deficient individuals, and secondly, to investigate the running mechanics of normal and ACL-deficient Individuals while wearing a derotation knee brace. Seven ACL-deficient individuals (X age = 25 +I- 5 yrs, X height = 1.80 +I- .07 m, X mass = 85.0 +/ 16 kg) and seven uninjured males (X age = 24 +I- 2 yrs, X height = 1.80 +/- .05 m, X mass = 86.0 +I- 5 kg) participated. Subjects were filmed during braced and unbraced straight-lie running across a force platform (cadence = 77 cycles-perminute). One acceptable trial was recorded for each subject under braced and unbraced conditions. Running velocities were 3.24 m/s and 3.50 m/s for normal and ACL-deficient subjects, respectively. Selected kinematic and kinetic parameters were calculated to quantify the differences between normal and ACL-deficient individuals, and the effect of bracing the knee. A 2 X 2 repeated measures analysis of variance revealed no statistically significant difference on any dependent variable (a = .05). It appears that ACL-deficiency may not alter the running mechanics of wellrehabilitated individuals during a low-risk, non-fatigued running task. Bracing the knee seemed to have no effect on the gait mechanics of normal or ACL-deficient individuals. The assessment of ACL-deficiency and bracing may require more demanding experimental protocol and/or newlyinjured/less-rehabilitated subjects. Future studies may benefit from an examination of the muscle moments at the occurrence of specific events during the support period

Work-Energy Analysis of Triathletes Running Under Bike/Run and Run Only Conditions

The purpose of the study was to determine if a triathlete's running mechanics are altered at various intervals during a 10 km run or if they are affected by having just completed a 40 km bike ride. Specifically, five skilled male triathletes volunteered as subjects and were filmed at three separate intervals (l km, 5 km, and 9 km) during each of two 10 km runs. In one instance the subjects had just completed a .40 km bIcycle race while in the other condition the subjects simply ran a 10 km run following a brief warm-up. Each performance was filmed at 50 hz by a 16 mm, Locam camera and data were collected from film through use of an Altek AC 30 digitizer and microcomputer system. Raw segment end-point data were processed using a Butterworth, fourth order, low pass digital filter with a cutoff to sampling ratio of 1 to 10. Both kinematlc and work-energy data (using the method of Pierrynowskl et al., 1980) were collected for each trial and each dependent variable was evaluated for statistically significant differences using a 2 X 3 repeated measures ANOVA. The mean running velocities at each of the three intervals selected were significantly higher in the run only condltlon (6.65 m/s, 6.38 m/s, 6.83 m/s) than in the bllce/run condltion (4.28 m/s/ 4.32 m/s, 4.24 m/s). These differences were accompanied by significant changes in the length of the running stride but not in the rate of striding. Analysis of the work-energy values revealed a statistically significant interval effect for the rate of working when passive energy exchanges were accounted for. In addition, there were significant differences in the work ra te between the bike/run and run only conditions. However, no significant differences were found in either the amount of energy passively transferred or the rate of passive energy transfer in comparlsons across intervals or between condItions. It was concluded that there are significant differences in running mechanics between a run which occurs following a 40 km bike race and a run following a brief warm-up. In addition, it was concluded that significant changes in both kinematics and work-energy characteristics of running mechanics occur between various intervals in a 10 km run

IMPACT CHARACTERISTICS OF TWO TYPES OF HOCKEY ARENA BOARDS

The purpose of this study was to investigate the energy absorption and energy transmission characteristics of two different types of ice hockey arena boards when impacted at both shoulder height and hip height. Traditional or standard boards were compared to a new, "softer", and theoretically more energy absorbent, type of boards. A pendulum system was designed to provide a method of impacting both the "glass" and "boards" sections with varying masses and at varying velocities. A Tri-axial accelerometer and a displacement transducer were attached to the pendulum mass to allow direct measurement of acceleration, velocity, and displacement during impact. Using these variables, forces and energies could be calculated. The results of this study indicated that standard arena boards returned 73 % more peak force per joule of initial energy than the new softer boards. The pooled data over conditions also indicated that the standard boards were 136 % stiffer than the new boards and that the new, softer boards absorbed 23 % more impact energy than their traditional counterparts. These results have particular relevance to the problem of injuries in the sport of ice hockey. It would appear that the softer boards are significantly better at absorbing impact energy and reducing peak forces, thus reducing the risk of injury on impact

EFFECTS OF FATIGUE ON FORWARD, MAXIMUM VELOCITY IN ICE HOCKEY SKATING

The purpose of the study was to compare the skating mechanics of skilled and less skilled hockey skaters under fatigued and non-fatigued conditions. 14 subjects participated in the skating task. Each was video taped from two views on three occasions during a 380 m task. The first occasion was considered non-fatigued and the latter two fatigued conditions. The video was analysed via a three dimensional APAS. The independent variables were skill level and fatigue level. Several dependent variables reflecting skating mechanics were also measured. Statistical analysis indicated several changes accompanying fatigue. The variables affected included stride length, skating velocity, and range of motion and angular velocities in the lower limbs. It was concluded that fatigue does have significant detrimental affects on skaters at both skill levels prompting rapid redeployment during game situations

Cleareye In-Ground and In-Concrete DIV Inspections: FY11 Final Report

This report summarizes the results of a series of feasibility testing studies for in-ground and in-concrete imaging/detection technologies including radar imaging and acoustic time-of flight method. The objectives of this project are: (1) Design Information Verification (DIV) Tools for In-Concrete Inspections - To determine the feasibility of using holographic radar imaging (HRI), radar imaging, and acoustic time-of-flight (TOF) non-destructive evaluation technologies to detect, locate and identify pipes and voids embedded in standard-density and high-density concrete walls that typify those the IAEA will need to verify during field inspections; (2) DIV Tools for In-Ground Inspections - To determine the feasibility of using HRI and radar imaging non-destructive evaluation technologies to detect, locate, and identify objects buried at various depths made of various materials (metal, plastic, wood, and concrete) and representing geometries that typify those the IAEA will need to verify during field inspections; and (3) Based on the results of the studies, recommend the next steps needed to realize fieldable tools for in-concrete and in-ground inspections (including detection of deeply buried polyvinyl chloride [PVC] pipes) that employ the technologies shown to be feasible

Search for the standard model Higgs boson decaying to a bbˉb\bar{b} pair in events with no charged leptons and large missing transverse energy using the full CDF data set

We report on a search for the standard model Higgs boson produced in association with a vector boson in the full data set of proton-antiproton collisions at $\sqrt{s} = 1.96$ TeV recorded by the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.45 fb$^{-1}$. We consider events having no identified charged lepton, a transverse energy imbalance, and two or three jets, of which at least one is consistent with originating from the decay of a $b$ quark. We place 95% credibility level upper limits on the production cross section times standard model branching fraction for several mass hypotheses between 90 and $150 \mathrm{GeV}/c^2$. For a Higgs boson mass of $125 \mathrm{GeV}/c^2$, the observed (expected) limit is 6.7 (3.6) times the standard model prediction.Comment: Accepted by Phys. Rev. Let

Search for the standard model Higgs boson decaying to a bb pair in events with one charged lepton and large missing transverse energy using the full CDF data set

We present a search for the standard model Higgs boson produced in association with a W boson in sqrt(s) = 1.96 TeV p-pbar collision data collected with the CDF II detector at the Tevatron corresponding to an integrated luminosity of 9.45 fb-1. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the W boson to an electron or muon and a neutrino, we set 95% credibility level upper limits on the WH production cross section times the H->bb branching ratio as a function of Higgs boson mass. At a Higgs boson mass of 125 GeV/c2 we observe (expect) a limit of 4.9 (2.8) times the standard model value.Comment: Submitted to Phys. Rev. Lett (v2 contains clarifications suggested by PRL

Search for the standard model Higgs boson decaying to a bb pair in events with two oppositely-charged leptons using the full CDF data set

We present a search for the standard model Higgs boson produced in association with a Z boson in data collected with the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.45/fb. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electron or muon pairs, we set 95% credibility level upper limits on the ZH production cross section times the H -> bb branching ratio as a function of Higgs boson mass. At a Higgs boson mass of 125 GeV/c^2 we observe (expect) a limit of 7.1 (3.9) times the standard model value.Comment: To be submitted to Phys. Rev. Let