EFFECTS OF VEST LOADING ON SPRINT RUNNING BIOMECHANICS

The study investigated the influence of vest loading on relative GRF’s during maximum velocity sprinting, and determined the relationship between flight times and relative vertical GRF’s. As a vertical vector-training stimulus, vest loading decreased flight times and vertical GRFs. Vertical loading does not seem to produce desirable effects on sprinting performance or GRFs

CARRYING A BALL CAN INFLUENCE SIDESTEPPING MECHANICS IN RUGBY

Sidestepping mechanics have been implicated as a risk factor for knee injury in rugby. Carrying a ball is proposed to alter movement patterns. Therefore the purpose of the study was to examine the effects of sidestepping with a ball compared to sidestepping without a ball on lower-extremity biomechanics in male rugby athletes. Three-dimensional kinematics of 18 male rugby athletes were recorded during a maximal effort 45° sidestepping task without and with a ball. Sidestepping with a ball resulted in 15% greater knee adduction angle during weight acceptance and 18% greater hip adduction angle during peak pushoff than without a ball. Future biomechanical evaluations of athletes require the inclusion of the ball specific to the sport to ensure accurate interpretation of movement patterns

MEASUREMENT OF STRIKING IMPACT KLNETKS VIA INERTIAL MODELLING AND ACCELEROMETRY

Striking impact has teen explored repeatedly in combat sports. The majority of methods used in the literature require intricate equipment. This study implemented a novel and simple method of measuring impact kinetics using a common, commercially available striking bag. Impulse and peak force of impacts were determined, with reliability and validity statistics obtained from multiple impacts with a custom ballistic pendulum. Test-retest reliability calculations determined that all measures had acceptable reliability (CVI less than/ equal to 2.4%). Using linear regression modelling, the coefficient of determination scores displayed a good fit for the model (R exponent 2 greater than / equal to 0.96) when plotted with a spectrum of pendulum masses. This novel method represents a reliable and valid approach to measuring striking impact kinetics which is easily adaptable to any type of hanging striking target

The Influence of Head Impact Threshold for Reporting Data in Contact and Collision Sports: Systematic Review and Original Data Analysis

- Background - Head impacts and resulting head accelerations cause concussive injuries. There is no standard for reporting head impact data in sports to enable comparison between studies. - Objective - The aim was to outline methods for reporting head impact acceleration data in sport and the effect of the acceleration thresholds on the number of impacts reported. - Methods - A systematic review of accelerometer systems utilised to report head impact data in sport was conducted. The effect of using different thresholds on a set of impact data from 38 amateur senior rugby players in New Zealand over a competition season was calculated. - Results - Of the 52 studies identified, 42 % reported impacts using a >10-g threshold, where g is the acceleration of gravity. Studies reported descriptive statistics as mean ± standard deviation, median, 25th to 75th interquartile range, and 95th percentile. Application of the varied impact thresholds to the New Zealand data set resulted in 20,687 impacts of >10 g, 11,459 (45 % less) impacts of >15 g, and 4024 (81 % less) impacts of >30 g. Discussion Linear and angular raw data were most frequently reported. Metrics combining raw data may be more useful; however, validity of the metrics has not been adequately addressed for sport. Differing data collection methods and descriptive statistics for reporting head impacts in sports limit inter-study comparisons. Consensus on data analysis methods for sports impact assessment is needed, including thresholds. Based on the available data, the 10-g threshold is the most commonly reported impact threshold and should be reported as the median with 25th and 75th interquartile ranges as the data are non-normally distributed. Validation studies are required to determine the best threshold and metrics for impact acceleration data collection in sport. Conclusion Until in-field validation studies are completed, it is recommended that head impact data should be reported as median and interquartile ranges using the 10-g impact threshold

Lower Limb Mechanical Properties: Significant References Omitted

International audienceWe read with attention the recent narrative literature review by Pearson and McMahon [1]. We were very surprised and quite disappointed by the amount of relevant literature omitted by the authors on lower limb mechanical properties and, specifically, how ‘limb stiffness’ could affect performance and risk of injury. Although this review focuses on muscle-tendon unit (MTU) stiffness, the more global vertical, leg and joint stiffness (i.e. referred to as limb stiffness, collectively) are also reviewed, as the authors assume that limb stiffness is primarily controlled by MTU stiffness

Activation of the <i>gluteus maximus</i> during performance of the back squat, split squat and barbell hip thrust and the relationship with maximal sprinting

The purpose of this research was to compare muscle activation of the gluteus maximus and ground reaction force between the barbell hip thrust, back squat, and split squat and to determine the relationship between these outcomes and vertical and horizontal forces during maximal sprinting. Twelve male team sport athletes (age 25.0 ± 4.0 years, stature 184.1 ± 6.0 cm, body mass 82.2 ± 7.9 kg) performed separate movements of the three strength exercises at a load equivalent to their individual three repetition maximum. The ground reaction force was measured using force plates and the electromyography (EMG) activity of the upper and lower gluteus maximus was recorded in each leg and expressed as percentage of the maximum voluntary isometric contraction (MVIC). Participants then completed a single sprint on a non-motorized treadmill for the assessment of maximal velocity, horizontal and vertical forces. Although ground reaction force was lower, peak EMG activity in the gluteus maximus was higher in the hip thrust than the back squat (p = 0.024; 95%CI = 4 – 56%MVIC) and split squat (p = 0.016; 95%CI = 6 – 58%MVIC). Peak sprint velocity was correlated with both anterior-posterior horizontal force (r = 0.72) and peak ground reaction force during the barbell hip thrust (r = 0.69) but no other variables. The increased activation of gluteus maximus during the barbell hip thrust and the relationship with maximal running speed suggests that this movement may be optimal for training this muscle group in comparison to the back squat and split squat

Relationships between sprinting, agility, one- and two-leg vertical and horizontal jump in soccer players

The aim of this study was to profile physical characteristics of soccer players measured by acceleration, vertical jump (VJ), horizontal jump (HJ) and change of direction ability (CODA) tests, and to quantify the relationships between these characteristics. Additionally, leg asymmetries between the dominant and nondominant legs during unilateral VJ and HJ were assessed. Thirty-nine male soccer players (22.9±2.8 years, 179.9±6.01 cm, 77.0±8.3 kg), competing in the third division of the Spanish Soccer League, participated in this study. Soccer experience of these players amounted to 15.19±3.15 years. Significant moderate correlations (p<.05) were found between all HJ tests and the modified agility (MAT) or the 505 test, and between all VJ tests and the Y20 or the 505 test. The significant differences between the dominant and non-dominant legs were found for the horizontal drop jump test (p=.001, d=.66) and horizontal three jump test (p=.017, d=.33). No significant differences between the dominant and non-dominant legs were found for VJ tests. The correlation between jumping and CODA varied depending on the characteristics of test types. The significant leg asymmetry in horizontal jumps with bounds found in the present study suggests that soccer players have greater leg asymmetries in the horizontal jump than in the vertical jump

Injury risk factors, screening tests and preventative strategies: A systematic review of the evidence that underpins the perceptions and practices of 44 football (soccer) teams from various premier leagues

Purpose: To systematically review the scientific level of evidence for the ‘Top 3’ risk factors, screening tests and preventative exercises identified by a previously published survey of 44 premier league football (soccer) teams. Also, to provide an overall scientific level of evidence and graded recommendation based on the current research literature. Methods: A systematic literature search (Pubmed [MEDLINE], SportDiscus, PEDRO and Cochrane databases). The quality of the articles was assessed and a level of evidence (1++ to 4) was assigned. Level 1++ corresponded to the highest level of evidence available and 4, the lowest. A graded recommendation (A: strong, B: moderate, C: weak, D: insufficient evidence to assign a specific recommendation) for use in the practical setting was given. Results: Fourteen studies were analysed. The overall level of evidence for the risk factors previous injury, fatigue and muscle imbalance were 2++, 4 and ‘inconclusive’, respectively. The graded recommendation for functional movement screen, psychological questionnaire and isokinetic muscle testing were all ‘D’. Hamstring eccentric had a weak graded ‘C’ recommendation, and eccentric exercise for other body parts was ‘D’. Balance/proprioception exercise to reduce ankle and knee sprain injury was assigned a graded recommendation ‘D’. Conclusions: The majority of perceptions and practices of premier league teams have a low level of evidence and low graded recommendation. This does not imply that these perceptions and practices are not important or not valid, as it may simply be that they are yet to be sufficiently validated or refuted by research

TTN genotype is associated with fascicle length and marathon running performance.

Titin provides a molecular blueprint for muscle sarcomere assembly and sarcomere length can vary according to titin isoform expression. If variations in sarcomere length influence muscle fascicle length, this may provide an advantage for running performance. Thus the aim of this study was to investigate if the titin (TTN) rs10497520 polymorphism was associated with muscle fascicle length in recreationally active men (RA; n = 137) and marathon personal best time in male marathon runners (MR; n = 141). Fascicle length of the vastus lateralis was assessed in vivo using B-mode ultrasonography at 50% of muscle length in RA. All participants provided either a whole blood, saliva or buccal cell sample, from which DNA was isolated and genotyped using real-time polymerase chain reaction. Vastus lateralis fascicle length was 10.4% longer in CC homozygotes, those carrying two copies of the C-allele, than CT heterozygotes (p = 0.003) in RA. In the absence of any TT homozygotes, reflective of the low T-allele frequency within Caucasian populations, it is unclear if fascicle length for this group would have been smaller still. No differences in genotype frequency between the RA and MR groups were observed (p = 0.500), although within the MR group the T-allele carriers demonstrated marathon personal best times 2 min 25 s faster than CC homozygotes (p = 0.020). These results suggest that the T-allele at rs10497520 in the TTN gene is associated with shorter skeletal muscle fascicle length and conveys an advantage for marathon running performance in habitually trained men. This article is protected by copyright. All rights reserved

Relationship between vertical and horizontal force-velocity-power profiles in various sports and levels of practice

This study aimed (i) to explore the relationship between vertical (jumping) and horizontal (sprinting) force–velocity–power (FVP) mechanical profiles in a large range of sports and levels of practice, and (ii) to provide a large database to serve as a reference of the FVP profile for all sports and levels tested. A total of 553 participants (333 men, 220 women) from 14 sport disciplines and all levels of practice participated in this study. Participants performed squat jumps (SJ) against multiple external loads (vertical) and linear 30–40 m sprints (horizontal). The vertical and horizontal FVP profile (i.e., theoretical maximal values of force (F0), velocity (v0), and power (Pmax)) as well as main performance variables (unloaded SJ height in jumping and 20-m sprint time) were measured. Correlations coefficient between the same mechanical variables obtained from the vertical and horizontal modalities ranged from −0.12 to 0.58 for F0, −0.31 to 0.71 for v0, −0.10 to 0.67 for Pmax, and −0.92 to −0.23 for the performance variables (i.e, SJ height and sprint time). Overall, results showed a decrease in the magnitude of the correlations for higher-level athletes. The low correlations generally observed between jumping and sprinting mechanical outputs suggest that both tasks provide distinctive information regarding the FVP profile of lower-body muscles. Therefore, we recommend the assessment of the FVP profile both in jumping and sprinting to gain a deeper insight into the maximal mechanical capacities of lower-body muscles, especially at high and elite levels