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POSTURAL STABILITY AND ANTICIPATORY POSTURAL ADJUSTMENTS PERFORMANCES AFTER GENERAL MUSCLE FATIGUE IN TRAINED AND UNTRAINED ADULTS
Get PDFThe objective of this study was to explore the differences of postural stability and Anticipatory Postural Adjustments (APAs) performances after general muscle fatigue between trained and untrained adults. The displacements of Center of Pressure (COP) during static bipedal standing, the APAs of deep trunk muscles induced by voluntary movements, the Heart Rate (HR) and the Borg Rating of Perceived Exertion Scale (RPE) were recorded before and after a 20-minute general muscle fatigue on a rowing ergometer for eighteen trained and eighteen untrained subjects. After fatigue, the trained group exhibited less disturbed postural stability performances. Meanwhile, earlier and larger APAs activations of lumbar multifidus (LMF) were found in trained group regardless of fatigue conditions. These results suggest a beneficial effect of long-term training experience on counter-perturbation feedforward control and highlight the distinguishing role of LMF in evaluation and rehabilitation of motor dysfunction
WITHIN-DAY REPEATABILITY OF COORDINATION VARIABILITY MEASURES ACROSS THE RUNNING GAIT CYCLE
Get PDFThe purpose of this study was to identify the within-day repeatability of coordination variability calculated using a velocity ellipse area method. Twenty participants attended two data collection sessions within 6 hours. At each session, a marker based motion capture system measured kinematics whilst participants ran at 12 km/h on a treadmill. The minimum detectable change in coordination variability was calculated for four commonly researched joint/segment couplings. Of the couplings investigated, thigh flexion/extension – shank flexion/extension and hip flexion/extension – knee flexion/extension were most repeatable. But in the most repeatable coupling, an average change of 75% across the gait cycle would be required between sessions to detect a meaningful change. This indicated poor repeatability and possible causes are discussed
WHOLE-BODY CHANGE OF DIRECTION TASK EXECUTION ASYMMETRIES AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION
Get PDFThe angle and speed at which a change of direction (COD) manoeuvre is performed is strongly associated with lower limb mechanical loading. Asymmetries present in these factors after anterior cruciate ligament reconstruction (ACLR) may therefore influence the interpretation of inter-limb differences in joint-level biomechanical variables. We investigated the presence of asymmetries in centre of mass (COM) deflection and body rotation during a 90° COD manoeuvre in 144 male athletes 9 months after ACLR. COM deflection during stance phase was reduced on the operated limb, and differences in body orientation, COM heading angle and velocity at touchdown were observed. Differences in task execution may require consideration when interpreting joint-level inter-limb asymmetries after ACLR, although further work is needed to determine clinical relevance
ANY OLYMPIC JUMP THAT WOMEN CAN DO, MEN CAN DO NEARLY 20% BETTER
Get PDFMen clearly outperform women in events that depend on moving the body’s mass through space. However, the between-sex differences may vary with event specific mechanical demands. Existing observations suggest between-sex differences are relatively greater for jumping than running events. We tested this sytematically by comparing the top 50 performances for men and women in Olympic running (n=9) and three jumping (n=3) events over a recent 15-year period. We found that mean male–female difference across the three jumping events (17.8± 2.7%) was 1.5 times greater than the respective mean for the nine running events (11.2 ± 1.4%) examined. We conclude that male–female differences are substantially greater for all-out jumping versus running events
INTER-LIMB COORDINATION DURING SPRINT ACCELERATION
Get PDFBilateral coordination is inherent to running motions but has not been investigated during sprint acceleration. The purpose of the study was to examine inter-limb thigh coordination during the first four steps of sprint acceleration in elite and sub-elite athletes. Anti-phase coordination patterns predominated in each step, but the proportion of anti-phase motion was higher in elite athletes (85.9 ± 10.8%) than sub-elite athletes (76.8 ± 10.9%, ES 0.83). Coordination profiles suggest that sub-elite athletes exhibit longer periods of the trailing (+) pattern around the time of touchdown (swing thigh flexing, stance thigh fixed) and the leading (-) pattern in the latter part of stance (stance thigh extending, swing thigh fixed) compared with elite athletes. These results provide preliminary empirical support for the emphasis placed on the switching of the limbs by coaches
THE CONTRIBUTION OF BODY CENTER OF MASS VELOCITY TO BASKETBALL BALL RELEASE VELOCITY ACROSS SHOT DISTANCES
Get PDFThis study investigated the contribution of the body center of mass velocity to basketball ball velocity at release when taking shots from different distances from the hoop. Seven basketball players with ten years of experience performed at least ten shots from progressively greater distances: close (\u3c 2.5 m), medium (4.57 m, free throw line), and long (6.02 m, American high school three-point line). As the distance from the hoop increases, the ball velocity required at release increases. Our hypothesis was that an increase in the shot distance would increase the contribution of the body center of mass velocity to ball velocity at release was hypothesized. Kinematics of the ball were recorded using video. Reaction forces generated by each leg were measured using two force plates and used to determine the velocity of the body center of mass during the shooting motion. The results indicate that the percent contribution of the body center of mass velocity to ball velocity at release increased, and the arm contribution decreased with an increase in shot distance. Releasing the ball earlier in the body center of mass trajectory before the apex resulted in a greater percent body contribution of the center of mass vertical velocity to ball vertical velocity
ADAPTATIONS IN TRICEPS SURAE MUSCLE-TENDON UNIT MECHANICAL PROPERTIES IN ELITE JUMPERS
Get PDFThe purpose of this study was to analyse the triceps surae (TS) muscle-tendon unit (MTU) mechanical properties (muscle strength, maximal tendon strain and tendon stiffness) in elite track and field jumpers (long jump, triple jump, high jump, pole vault) over several years, in order to examine potential alterations in the uniformity of adaptation within the TS MTU. The findings demonstrated a higher TS muscle strength and tendon stiffness for the take-off leg in comparison to the swing leg, irrespective of the jumping discipline. Similar symmetry indexes for muscle strength and tendon stiffness indicated to a uniform TS MTU adaptation in healthy elite track and field jumpers. Longitudinal investigation demonstrated greater fluctuations in TS MTU properties over one year in elite jumpers compared to age-matched controls, predominantly for the take-off leg, irrespective of the training period (preparation vs. competition period). Nevertheless, athletes with lower adaptive similarities between muscle and tendon adaptation may experience temporary increased demand on the tendon and potentially be at greater risk for tendon injuries
TRANSVERSE PLANE HEAD-TRUNK COORDINATION DURING ANTICIPATED AND UNANTICIPATED SIDESTEPPING TASKS
Get PDFThe purpose of this study was to examine head control during anticipated and unanticipated sidestepping tasks. Twelve collegiate male soccer players performed seven anticipated and seven unanticipated sidestepping tasks. Head and trunk orientation and coordination were assessed during the preparatory and stance phases of the change of direction stride. The head and trunk were less oriented toward the new travel direction with reduced planning time. During the change of direction stride, participants aligned the head with the new travel direction but the trunk lagged behind to a greater extent during the preparatory phase when planning time was reduced. No differences in head and trunk coordination patterns were reported during the stance phase. These different head and trunk orientation and coordination patterns may impact perceptual awareness and potential for injury
DATA-TRACKING AND PREDICTIVE SIMULATIONS OF SPRINT RUNNING
Get PDFThe sprint running literature contains recommendations for how athletes should consider modifying their technique, yet, very few studies have documented their affect on performance. We used a musculoskeletal modelling and simulation approach to initially perform a data-tracking simulation to evaluate the outputs against experimental data. A predictive simulation with limited constraints was then performed to assess the influence of technique modications on performance. The data-tracking simulation tracked the experimental data well, particularly the ground reaction forces (largest RMSE = 0.04 BW). The predictive simulation resulted in the model covering 2.79 m in 0.325 s through an increase in step frequency, and this was a time duration improvement of 6.9% in comparison to the athlete’s own performance. In this preliminary work we have managed to track experimental sprint running data, and provided a promising basis to further explore hypothetical modifications in technique
THE EFFECT OF TRUNK ROTATION ON LOWER LIMB KINEMATICS DURING RUNNING – PRELIMINARY STUDY
Get PDFThe purpose of this study was to examine the running kinematics such as stride length, stride rate, speed, and joint range of motion when trunk rotation was manipulated. Six female recreational runners were recruited to perform a total of nine trials of over ground running in their comfortable speed (≈ 3.31 m/s) for natural gait, restricted trunk rotation, and exaggerated trunk rotation conditions. Exaggerating trunk rotation during running resulted in greater stride length and smaller stride rate significantly when compared to natural and restricted trunk rotation conditions. Although some of the significant change of the running kinematics were observed, the manipulation of the trunk rotation did not alter the overall running kinematics such as speed and range of motion at hip, knee, and ankle joints during braking and propulsive phases