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EFFECT OF ALPINE SKI BOOTS ON LOWER LIMB MOVEMENT DURING JUMPING
Get PDFThis study aimed to investigate the effects of alpine ski boots (ASB) on lower-limb power generation for movements such as jumps. Seven male alpine ski racers participated in this study and performed counter movement jumps and squat jumps. All trials were recorded using a motion capture system and two force plates. The jump height in the ASB condition was significantly lower than that in the training shoe (TS) condition for both jumps. The range of motion of both the ankle and knee joints in the ASB condition significantly decreased for both jumps. The angular velocity at hip joint extension in the ASB condition was significantly higher than that in the TS condition for both jumps. Our findings revealed that lower-limb movement and power are restricted when wearing ASB, and suggested the importance of power transfer training using the hip joint while wearing an ASB
SEX DIFFERENCES IN PROPRIOCEPTION AND BALANCE CONTROL IN INDIVIDUALS WITH CHRONIC ANKLE INSTABILITY
Get PDFThe study aimed to investigate sex differences in proprioception and balance control in individuals with chronic ankle instability (CAI). A total of 50 CAI participants (26 males and 24 females) were assessed using an isokinetic dynamometer, static balance system, and Y-Balance test. Absolute error, sway velocity and reach distance were used to measure the performance. Results showed compared with males, females had significantly better ankle force sense (plantarflexion: females 1.69±1.13N·m/kg, males 3.37±2.72N·m/kg; dorsiflexion: females 0.99±0.73N·m/kg, males 2.05±1.10N·m/kg) and exhibited smaller sway velocity of center of pressure in static balance. These findings emphasized the importance of sex-specific differences in proprioception and static balance among CAI, especially for males
ANALYSIS OF GAZE BEHAVIOR AND ELECTROMYOGRAPHY DURING NIHON KENDO KATA
Get PDFThis study aims to elucidate whether the gaze strategies of performers in Nihon Kendo kata and the muscle activity involved in gripping the sword depend on skill level. Six college-aged students participated, three having over 14 years of experience and the remaining three being novices. A wearable eye-tracking device was employed, and the surface electromyography (EMG) of the flexor digitorum profundus was recorded. We calculated objective features and applied a two-way ANOVA. As a result, a main effect of the expertise level was observed for the number and duration of fixations, the average acceleration obtained from eye movement, and the normalized time-averaged values from EMG (
EXAMINING FATIGUE EFFECTS ON BIOMECHANICAL ACL INJURY RISK FACTORS IN FEMALE ATHLETES DURING SINGLE-LEG DROP VERTICAL JUMP
Get PDFThis study aimed to examine the impact of fatigue on biomechanical factors associated with ACL injury risk in female athletes during the single-leg drop vertical jump task. Thirty-nine female athletes participated, undergoing a fatigue protocol comprising functional high-intensity exercises. Participants completed five trials before and after the fatigue protocol. Post-fatigue, significant differences were observed, including lower peak knee flexion angle. Notably, while fatigue induced changes in kinematic indicators, kinetics remained unaffected. As conflicting evidence in the role of fatigue is still on-going, this study highlights the influence of fatigue on specific mechanics, providing additional insights into the relationship between fatigue and biomechanical changes
EFFECTS OF DIAZEPAM, D-AMPHETAMINE, AND MORPHINE ON RATS’ CHOICES BETWEEN FOOD ALONE AND FOOD WITH DELAYED SHOCK
Get PDFRepeated choices that result in immediate reinforcing consequences followed by delayed aversive consequences are commonly associated with failures in “self-control”. The present study evaluated acute effects of diazepam, d-amphetamine, and morphine on rats’ choices using a variable-delay procedure that arranged choices involving conflicting-valence consequences. Rats pressed response levers to choose between a single-valence consequence (1 food pellet) and a conflicting-valence consequence (3 food pellets followed by a delayed shock). In each condition, the delay to shock varied systematically in a fixed sequence across blocks of trials of a session. After choice was stable, rats were exposed to acute administration of diazepam, d-amphetamine, and morphine. Effects of the drugs were shown by changes in patterns of choice of the single-valence consequence across the delays in each session, area under the curve, and response latencies. In sessions in baseline, following vehicle administration, and sessions conducted on the day before drug administrations, single-valence consequence choice was generally highest in blocks with short delays to shock and lowest in blocks with long delays, showing that effects of shock were an inverse function of the delay to shock. Following administration of diazepam, effects of shock on choice generally decreased, but this effect depended on the diazepam dose. Following administration of d-amphetamine, effects of shock on choice generally increased, but this effect depended on the d-amphetamine dose. Administration of morphine generally had no systematic effect on choice. This study sheds light on the general effects of commonly prescribed drug classes on choice in the conflicting-consequences paradigm
VELOCITY-BASED STRENGTH TRAINING: COMPARING DURATION AND MEAN VELOCITY TO PREDICT THE MAXIMUM NUMBER OF REPETITIONS IN A SET
Get PDFThis study explores the relationships among various velocity parameters and the maximum number of repetitions in a set (XRM). Specifically, the predictive power of the concentric phase duration (Tconc) and other velocity parameters, such as the peak velocity, are examined against the conventional average concentric velocity (ACV) approach. Using a preliminary dataset, various models are developed in this study to predict the maximum number of repetitions performed in a set. The findings indicate that Tconc significantly predicts repetitions with the adjusted model (R²: 0.37, standard error of estimate (SEE): 2.98), outperforming the ACV model (R²: 0.14, SEE: 3.46). However, because of the limitations of its small sample size and the absence of a test group, the study\u27s models necessitate further validation. The results highlight the potential of assessing and analyzing the features of the velocity curve and lay the groundwork for larger, more diverse studies to validate and build upon these initial findings. This research advocates for a more in-depth examination of velocity curves, which could lead to more effective and safer training methodologies
VISUAL TASK CONSTRAINTS INFLUENCE HEAD CONTROL AND COORDINATION VARIABILITY IN CONTACT SPORT ATHLETES
Get PDFWe sought to determine whether contact sport participation affects visual acuity, head control, and coordinative variability during locomotor tasks. Thirteen contact and eleven noncontact athletes completed treadmill walking tasks with and without a visual Landolt C task (identify open circle orientation). During baseline, head motion did not differ between groups, but contact athletes had reduced pelvis-thigh variability compared to noncontact athletes. During the visual condition only noncontact athletes reduced vertical head displacement which may reflect an adaptive motor strategy not present in contact athletes. These differences were accompanied by significantly reduced coordinative variability in contact athletes compared to noncontact athletes. These findings highlight motor alterations associated with contact sport status, which have the potential to impair perceptual awareness in sport-specific settings
LANDING BIOMECHANICAL CHARACTERISTICS OF ADOLESCENT ATHLETES WITH ANTERIOR KNEE PAIN COMPARED TO HEALTHY CONTROLS
Get PDFAnterior knee pain (AKP) is defined as chronic peripatellar pain. It may be caused by repetitive the knee extensor mechanism, which may predispose adolescent athletes to AKP due to the incomplete maturation. To reduce risk of AKP, we should understand landing biomechanics in adolescent athletes with AKP. Therefore, we aimed to identify landing biomechanical characteristics of the AKP group compared to the control group. We collected data on joint angles, moments, and power, ground reaction forces, and vertical stiffness during landing. We used Mann-Whitney U test and ensemble curve analyses to compare outcome variables between the AKP and control groups. The AKP group showed the landing strategies susceptible to AKP compared to the control group. Based on our findings, interventions to prevent AKP should be implemented in adolescent athletes
ON-FIELD ASSESSMENT OF CHANGE-OF-DIRECTION (COD) MOVEMENTS: ADAPTATION IN LEG AND TRUNK POSTURE THROUGHOUT A COD SEQUENCE
Get PDFThis study investigated adaptations in change-of-direction (COD) movement strategies throughout a sequence of maximum-speed CODs in an on-field testing scenario that involved complex decision making and limited time for motor preparation. Twenty soccer players completed randomized sequences of pre-planned and unplanned 45°-135° CODs and their joint movements were tracked using inertial measurement units. For 90°-135° turns, the last vs. first CODs showed a more extended knee and rotated trunk at initial contact. These kinematic features may reflect insufficient time to prepare for the ground contact of a COD that immediately follows a previous COD and are more consistent with postures observed during non-contact ACL injuries. Testing COD sequences rather than isolated CODs may be more sensitive for detecting ACL injury-prone movement strategies
UNRAVELING KINEMATICS OF UNPLANNED CHANGE-OF-DIRECTION MANEUVERS: A FIELD-BASED EXPLORATION FOCUSED ON ACL INJURY RISK
Get PDFACL injury risk during COD maneuvers is dependent on the chosen movement pattern, which can be impacted by factors like anticipation. This study used a field-based approach including multiple COD angles and directions to explore the effects of anticipation and COD angle on joint angles at the initial ground contact. Twenty soccer players completed planned and unplanned CODs, with kinematic data collected by IMU sensors. For unplanned scenarios, we found evidence for risk-mitigating adaptations (higher knee flexion (p \u3c .001), lower hip abduction (p = 0.046)) as well as injury-provoking movements (less pelvis pre-orientation (p \u3c .001), higher trunk rotation (p = 0.016)), which resulted in decreased COD performance (completion time). This study provides insight into the impact of reduced preparation time on on-field COD kinematics, mimicking the dynamic nature of sports