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CHARACTERISTICS OF THE PATELLAR TENDONS IN ANTERIOR CRUCIATE LIGAMENT INJURED ATHLETES
Get PDFThe purpose of this study was to demonstrate the characteristics of patellar tendons and the quadriceps strength of athletes with anterior cruciate ligament reconstruction (ACLR) throughout rehabilitation. Athletes of different sports (n=27) had both patellar tendons (PT) assessed with ultrasound tissue characterization (UTC) method, and bilateral isokinetic quadriceps strength quantified in intervals of 1.5 months over their rehabilitation period. Reduction in the quality of the involved PT was observed after ACLR surgery, with these values returning to baseline at approximately 7.5 months post surgery. The uninvolved PT displayed no significant differences. Despite the increase in quadriceps strength, no statistical relevance was observed. ACLR caused reduction in the quality of the involved PT which might be correlated with tendon symptoms during the rehabilitation
EFFECT OF LANDING STRATEGIES ON LOWER LIMB JOINT KINETICS DURING LOADED JUMPS
Get PDFThe purpose of this study was to analyze the effect of landing strategies on the landing kinetics during loaded jumps. Ten male participants performed counter movement jumps with 50% body weight (BW) additional load using four different landing strategies. Landing strategy referred to peak knee joint flexion during landing. Peak vertical force increased up to 50% with decreasing knee joint flexion during landing. No changes were found regarding peak joint moments and powers. Total lower limb joint work increased up to 83% with increasing knee joint flexion during landing. The results suggest that energy dissipation during loaded landing is shifted from active (muscle-tendon system) to passive (skeletal system) as peak knee flexion decreases during landing, resulting in mechanical stress on different body tissues depending on the landing strategy
ROAD BIKE DAMPING: COMFORT OR PERFORMANCE RELATED?
Get PDFThe aim of this study was to determine if a road bike specific damping system increases short term performance. Muscular activation of the triceps surae and quadriceps femoris, oxygen consumption, heartrate and maximum power output of thirty male, trained cyclists were recorded. The participants performed on a damped and non-damped road racing bike six-minute steady state and four-minute all-out tests with and without vibration. Vibration significantly increased the mean activation of the triceps surae and significantly increased oxygen uptake and heartrate. Damping had no impact on muscular activation, energy requirements and cardiopulmonary response. It is therefore concluded, that cycling specific vibration affects the musculoskeletal system and slightly increases total energy demand. Damping contributes to upper body comfort but does not influence short term performance directly
BODY SHAPE AND CENTER OF MASS ESTIMATION USING MULTI-VIEW IMAGES
Get PDFThis study presents a method for estimating human 3D body shape in action. We propose a method for estimating 3D human body shape motion that uses multiple view images and visual hulls. Related methods necessitated lengthier preparations, such as camera calibration, which would require several tries before actually capturing the image. We solve this issue by combining state-of-the-art computer vision methods to automatically process the required inputs and parameters, so that camera images are the only resource needed for estimation. In our experiments, we applied our method to a video of human subject kicking a soccer ball to left and right side of a goal; we successfully acquired the subject’s 3D body shape. In addition, we verified that the application’s automatically obtained body shape successfully provides the subject’s center of mass
A QUANTITATIVE COMPARISON OF TWO BIOMECHANCIS CONCEPT INVENTORY VERSIONS
Get PDFThis study quantified student responses between two different versions (1 and 3) of the Biomechanics Concept Inventory (BCI) assessment. Fifty students from a comprehensive university in the USA took both BCI versions on the first (pre) and last (post) day of an introductory undergraduate biomechanics course. Students scored significantly higher on BCI 3 for the post-test and gain score (i.e.: difference between pre and post). Eight of the twelve competency areas resulted in significantly different correct scores between versions. Correlations of competencies between versions ranged from -0.13 to 0.43, however, only two were significant. Discriminant analysis of the competency areas determined that BCI 1 predicted overall assessment performance better than BCI 3. The disparate results between versions should be considered in determining which to use
EFFECT OF SMOOTHING ON IMPACT VARIABLES IN SOCCER KICKING
Get PDFThis technical note examined the effect of smoothing on calculation on several impact effectiveness variables in soccer kicking. A skilled male soccer player performed 10 maximum effort place kicks with a regulation soccer ball. Two-dimensional foot and ball motion were recorded by high-speed (210 Hz) for the 0.4 seconds around impact. Kinematic data were smoothed either through impact or using a separation and five-point linear interpolation technique (Knudson, 2005). Smoothing protocol had a significant effect on three of five impact effectiveness variables (e, foot-to-ball speed ratio, VFpre). Smoothing protocol did not affect VBpost and effective striking mass. The results supported previous studies reporting distortions of velocities near impact in striking objects, however these distortions inconsistently affected more complex impact parameters. More research is needed on smoothing techniques for impact kinematic variables, particularly parameters utilizing both pre- and post-impact velocity values
MATURITY RELATED CHANGES IN INTER-SUBJECT VARIABILITY DURING CUTTING MANOEUVRES OF ADOLESCENT SOCCER PLAYERS
Get PDFThe incidence of various injury rises with the onset of puberty and the growth spurt around 13 years. The biomechanical reasons are unclear. Therefore, the purpose of this study was to investigate the kinematics of the hip and knee joint of pre peak height velocity (PHV) and mid PHV soccer players during a 90° cutting manoeuvre. Twenty-two participants were investigated with a 3D movement analysis system and a force platform. Results showed no statistical difference in the time series of the hip and knee joint kinematics. Average variability of the knee flexion and internal rotation angle were significantly higher for the pre PHV group. This indicates a consolidation of the movement technique during the phase of the growth spurt, caused by the fast changes in length and masses of the segments
TOWARDS A “MORE VALID” METHOD OF VALIDATION: APPLICATION OF EFFECTIVE MASS FOR ERROR RESOLUTION OF FORCE PLATE MEASUREMENTS
Get PDFWe introduce effective mass as the preferred alternative to total system mass when analyzing a multi-link model of the human body. Effective mass is defined as the mass that would have equivalent motion characteristics at the point of force application if substituted for the whole system. We demonstrate our findings by deriving formulations for loaded back squat and bench press exercises. Our results suggest that force-plate-derived metrics such as velocity and power contain non-trivial errors when total system mass is used to infer kinematics of external loads. We elaborate on the sources of these errors and how they can compromise the assessment of the validity or reliability of other devices, such as linear position transducers and IMU-based tools
EFFECTS OF STANDARDIZING KICK PLATE POSITION ON TRACK START BIOMECHANICS IN ELITE SWIMMERS
Get PDFKick plate position in the track start is arbitrary but may influence performance. The purpose of this study was to investigate the influence of standardizing kick plate position based on shin length. 15 elite swimmers performed 3 starts at 3 kick plate positions (\u3c shin length, shin length, and \u3e shin length). Differences in reaction time (RT), block phase time, flight phase time, flight distance, underwater phase time, and time to the 15 m mark were examined between kick plate positions. Only RT was significantly different, (F(2,28)=4.713, p=.017). RT was lower when the kick plate distance was one shin’s length versus \u3c shin length (0.173+0.034vs 0.194+0.061 sec) and \u3e shin length (0.173+0.034 vs 0.195+0.047 sec),
Threat Perception Alteration as an Effect of Use-of-Force Simulation Training
Get PDFDue to the nature of police work police officers are often placed in life threatening situations. To prepare officers for these interactions police academies employ use-of-force simulations to train relevant skills such as situational awareness and judgement. Repeated exposure to threatening situations, such as those in the use-of-force simulations, may alter the threat perception of the participant. Using self-report measures of anxiety (STAI-6 Item) and affect (PANAS), as well as respiration rate data, and short answer self-reports, the present study aims to determine if perception of threat is altered as a result of the use-of-force training, both directly after one training session and after completing the 16 week training. Two alternative hypotheses predict the outcome: a) the training will increase the participant’s situational awareness, in turn increasing threat perception with an increase in anxious symptoms and autonomic arousal as evidence, or b) the training will desensitize the participant to violence leading to decreased threat perception with decreased positive and negative affect, and decreased autonomic arousal as evidence. Evidence for the latter hypothesis was found indicating that repeated exposure to the use-of-force training simulation increased participant’s perception of threat, manifested by an overall decrease in emotional responding suggesting that the participants were desensitized to threat over time. It is possible that decreased emotional responding due to desensitization can lead to maladaptive processes such as affective blunting, therefore it is important to examine this link between officer training and desensitization to threat