ISBS (International Society of Biomechanics in Sports): Conference Proceedings Archive
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HEAD IMPACT FREQUENCY IN YOUTH AMERICAN FOOTBALL, AGES 9-13
Get PDFThe objective of this study was to quantify head impact frequency in youth American football players, ages 9-13. Kinematic data from head impacts were collected from 25 players on two teams (11.7 ± 1.2 years) using a helmet-mounted accelerometer system. A total of 4432 head impacts were recorded, including 1800 during 265 practice sessions and 2632 during 175 game sessions. Most peak linear acceleration magnitudes were less than 20 g in practices (60%) and games (55%). For impacts greater than or equal to 60 g, players sustained 122% more in games than practices. Both teams played in leagues that limited full-contact practice time, which likely contributed to lower impact frequencies in practices. Interventions to further reduce head impact frequency in youth football should include measures which affect in-game exposure
EFFECTS OF FOOT PLANTING POSITIONS ON KNEE JOINT IN DROP LANDING
Get PDFThe purpose of this study was to investigate the effect of three different foot placement positions at the moment of foot-ground contact on the knee joint kinematics and kinetics in drop landing in an attempt to estimate the risk of non-contact anterior cruciate ligament (ACL) injury. Three foot placement positions were toe-in (TI), neutral (N), and toe-out (TO) positions according to the heading direction of toes relative to femur. Seventeen college students participated in this study and motion capturing system with forceplatforms was used to assess the drop landings. Toe-in (TI) position should be avoided due to the highest combined loading of valgus and internal rotation. The neutral foot landing position is recommended to minimize the risk of non-contact ACL injury
VALIDITY AND RELIABILITY OF ACCELEROMETRY FOR ASSESSING IMPACT LOADS IN JUMPING TASKS
Get PDFHigh injury rates in gymnastics have been suggested to be related to impact loading. This study examined the validity and reliability of a tri-axial accelerometer, mounted on the upper back, to estimate impact loads. Twelve female participants performed a continuous double legged hopping task and rebound jumps from a drop of 40, 60 and 80 cm. Peak resultant acceleration (PRA) showed moderate to good reliability. Correlation coefficients between ground reaction force (GRF) and PRA ranged from rs=0.860 for the continuous hopping task to rs= 0.608 for rebound jumps from 80 cm, and were all significant. The results of the current study support the use of PRA to estimate impact load in jumping tasks, and show potential for this measure to be employed in a gymnastics training setting
A BIOMECHANICAL ANALYSIS OF THE KICKING LEG DURING A RUGBY PLACE KICK
Get PDFThe successful performance of rugby place kicks is often important in determining the outcome of a match. This study aimed to further the understanding of rugby place kicking technique by quantifying and explaining kicking leg joint mechanics. Three-dimensional joint kinematics and kinetics were calculated using an inverse dynamics analysis. Whilst ankle motion was negligible, the knee flexed until around 50% of the kicking phase before extending towards ball contact. A resultant hip flexor moment was largely dominant throughout; it initally reduced extension before initiating flexion near support foot contact. Whilst these patterns were broadly similar to soccer kicking, peak magnitudes of angular velocity and resultant moment appeared to differ from soccer kicking and, along with the mechanics about other joint axes, these require further investigation
USING REAL-TIME BIOMECHANICAL FEEDBACK TO CHANGE ERGOMETER ROWING TECHNIQUE
Get PDFStudy focuses on improving ergometer rowing technique using biomechanical feedback. Kinetic and kinematic data are acquired during rowing, processed, and compared with reference models based on skilled rowers. Feedback information provides knowledge of performance using concurrent feedback, video feedback, video modelling, and error correction strategies. Based on the real-time feedback, the rower modifies movement towards a proper technique. 36 participants in three groups took part in an evaluation study. One group trained without supervision, one with a trainer, and one with the realtime biomechanical feedback. The results show that participants were able to utilize the provided feedback. The results of training with the biomechanical feedback were much better than training without supervision and comparable to training with a trainer
CONTRIBUTION OF THE ARMS IN THE SPRINT START AND THEIR INFLUENCE ON FORCE AND VELOCITY CHARACTERISTICS
Get PDFThe purpose of this case study was to quantify the contribution of the arms in the sprint start and compare the difference in force and velocity characteristics when arm forces are not accounted for. One elite student athlete performed 6 starts with the same block position whilst forces were measured independently for front and rear legs and left and right hands. The arms were found to apply force for 0.14s, initiated a peak force of 593N (0.83 BW) and accounted for 18% of the total vertical impulse generated. Inclusion of the arm forces increased the first vertical peak force by 118N, movement time by 0.03s, vertical toe-off velocity by 0.6m/s and projection angle by 10 degrees. Differences in vertical velocity and projection angle were halved by modifying the vertical system load to BW at the onset of movement. Peak horizontal forces and velocities were similar
RELATIONSHIP BETWEEN UPPER EXTREMITY MASS DISTRIBUTION AND PERFORMANCE IN COLLEGIATE TENNIS PLAYERS
Get PDFThe purpose of this study was to assess the relationship between upper extremity mass distribution and performance in tennis. Eighteen healthy collegiate tennis players consented to participate in this study. The study consisted of body mass distribution analysis using a dual X-ray absorptiometry scan and a simulated performance assessment to gauge accuracy and velocity of various tennis shots. The data collected suggests that mass distribution in the upper extremity is related to both shot velocity and accuracy
SWEEP LENGTH VS SWEEP RATE ANALYSIS IN COMPETITIVE MALE AND FEMALE CURLERS
Get PDFThe purpose of this study was to examine sweep length and sweep rate in competitive male and female curlers. Sixteen curlers (8 males, 8 females) completed a 25-second bout of maximal effort sweeping which was video recorded and analyzed using Dartfish. Sweep length and sweep rate were determined for each 5-second interval (0-5s, 5-10s, 10-15s, 15-20s, 20-25s). Comparisons were made among time intervals and between genders. Sweep length was found to be similar between genders (p = 0.922), with significant differences seen between the 0-5s and 5-10s time intervals (p < 0.05). Sweep rate was significantly faster for males across all time intervals (p < 0.001), with males and females showing differences in the rate at which sweep rate decreased over time. This information may help curlers improve their sweeping strategy during competitive play
DIFFERENCES IN SEMG BETWEEN NORMAL SQUATS AND ACCENTUATED ECCENTRIC LOADED SQUATS IN COMPETITIVE COLLEGIATE WEIGHTLIFTERS
Get PDFThe purpose of the present work was to compare the effect of accentuated eccentric loaded (AEL) squats to normally loaded (NOR) squats on surface measured muscle activation (sEMG) in competitive weightlifters. Eight experienced, competitive weightlifters (six males, two females) completed both an AEL and NOR squat session (seven days apart), comprised of nine sets of squats, and was identical to their normal scheduled training. sEMG data from the vastus medialis (VM), vastus lateralis (VL), and biceps femoris (BF) was collected (at 1000Hz) during the entirety of the concentric (CON) phases of the AEL and NOR sessions. RMANOVAs (set x session-type) were calculated and no statistical differences were found (p > 0.05) while promising statistical effect sizes (?2 partial 0.073 to 0.273) were observed
PRONATE GLOBALLY BUT SUPINATE LOCALLY: EVIDENCE OF RADIO-ULNAR SUPINATION AT BALL RELEASE
Get PDFThe purpose of this study was to investigate the radio-ulnar longitudinal rotation during baseball pitching. We captured movements of nine skilled pitchers during pitching by using a system with 16 high-speed cameras (Vicon MX, 1000 Hz). Ten fastest trials which hit a target were averaged to obtain representative data for each participant. We found that the radio-ulnar joint supinated at around the moment of ball release (BRL), although the wrist continued rotating in the direction of pronation at around BRL in the global coordinate. The supination occurred due to the influence of the combination of elbow extension and shoulder internal rotation