Purpose: Adolescents have significantly higher rates of diagnosed anterior cruciate ligament (ACL) injuries compared to adult cohorts. Approximately two-thirds of ACL injuries are non-contact scenarios that occur while performing “high-risk” maneuvers. Less than 50% of adolescents are able to return-to-activity, with females specifically having a lower activity level post-injury (Hewett, Di Stasi, & Myer, 2013; Schmale, Kweon, Larson, & Bompadre, 2014). Identifying the quantitative demand of a task used to assess return-to-activity will help establish its role in evaluating the knee stabilization strategies based on muscular coactivations and biomechanical outputs. Therefore, the aim of this study was to (1) assess the neuromuscular and biomechanical quantitative outputs of the lunge and drop-vertical jump (DVJ) in healthy adolescent male and females athletes and (2) to examine the muscular coactivation strategies of adolescent male and female athletes with and without an ACL injury. Methods: A total of 68 uninjured adolescent male and female athletes between the ages of 10 to-18 were used to identify the quantitative demand of the lunge and DVJ. Neuromuscular and biomechanical quantitative outputs included mean peak knee flexion (PKF), integrated knee excursion (iKEXC) in the sagittal and frontal planes, integrated knee joint power (iJP), and integrated electromyography (EMG) were used to assess the within (task) and between (sex) interactions. An additional 17 male and 37 female adolescents with an ACL injury were included to assess the impact of an ACL injury on the knee stabilization strategies (coactivations) used to maintain dynamic knee joint stability (frontal plane knee excursion). Ethics was approved by the University of Ottawa Research Ethics Board (uOttawa REB H09/17/10) (CHEO REB 17/74X). Results: Quantitative data for uninjured groups indicated that the lunge produced greater peak knee flexion, knee excursion, and quadriceps activation values than the DVJ. Conversely, the DVJ produced greater joint power, biceps femoris, gastrocnemii, and gluteus medius values. As for knee stabilization strategies, during the DVJ female ACL injured groups produced greater symmetry and higher muscular activations between anterior-posterior and medial-lateral muscular coactivations, which resulted in increased stability compared to uninjured female groups. Males with an ACL injury indicated similar knee stabilization strategies however decreased stability compared to males without an ACL injury. Conclusion: Results of this thesis identified differences in quantitative data between the lunge and DVJ, indicating differing demand requirements for each task. Results of the second study indicate that uninjured females use knee stabilization strategies that do not restrict their degrees of freedom through asymmetrical coactivations, while females with an ACL injury have increased coactivations in both anterior-posterior and medial-lateral muscle groups, resulting in increased dynamic knee joint stability as evidenced by reduced frontal plane knee excursion motion. Males, however, failed to show a difference between groups in dynamic knee stability, suggesting that those with an ACL injury compensated in a way to perform the DVJ efficiently and similarly to the uninjured group, while maintaining dynamic knee joint stability. In a clinical setting, these findings may help in understanding the direction of use of the lunge and DVJ tasks in a rehabilitation setting. As well as provide insight into the differing male and female adolescent knee stabilization strategies used to maintain dynamic knee joint stability during functional tasks.

Effects of a custom bite-aligning mouthguard on performance in college football players. J Strength Cond Res 30(5): 1409-1415, 2016 - Besides injury prevention, mouthguards can also be employed to improve physical performance. The effects of personalization of mouthguards have rarely been investigated. This 3-armed, randomized, controlled crossover trial investigated the difference of wearing (a) personalized or custom-made (CM, e.g., bite-aligned), (b) standard (BB, boil and bite), and (c) no (CON) mouthguards on general fitness parameters in experienced collegiate football players. A group of 10 upperclassmen (age, 19-22 years; mean ± SD: age 20.7 ± 0.8 years; body mass 83 ± 7.4 kg; height 179.1 ± 5.2 cm; body mass index 25.9 ± 2.2 kg·cm -2), National Collegiate Athletic Association Division II football players with at least 2 years of playing experience, were randomly assigned to the 3 mouthguard conditions: a randomized, within-subjects repeated-measures design was applied. All participants were randomly tested on strength and endurance performance Vo 2 max testing, with Bruce treadmill protocol including (a) time to fatigue, (b) blood lactate concentration in millimoles per liter at stage 2 and (c) at peak fatigue, (d) flexibility, (e) reaction time, (f) squat vertical jump, (g) countermovement vertical jump, and (h) 1 repetition maximum bench press. Repeated-measures analysis of variance showed no significant differences between the 3 conditions for each outcome variable (0.23 < p < 0.94; 0.007 < < 0.15). These data indicate that CM mouthguards did not superiorly affect general fitness parameters compared with BB and CON. In turn, protective BB or CM mouthpieces did not appear to impair general fitness performance vs. CON. The recommendation of a custom bite-aligning mouthguards for performance enhancement in young Division II football players is questioned. Further studies with larger sample sizes, gender comparison, and (sport) discipline-specific performance testing are needed.

We examined a static jump test’s relationship with back squat strength in collegiate athletes. Forty-one (n=41) young (aged 20.8+2.4 years), healthy volunteers reported estimated back squat one-repetition maximums and completed a static jump protocol. The static jump protocol included five loading conditions, and jump height was estimated via flight time from portable contact mats. Loading conditions for males (n=19) included 0 kg (polyvinylchloride pipe), 20.42 kg, 43.10 kg, 61.25 kg, and 83.94 kg whereas females (n=22) used 0 kg, 12.70 kg, 20.42 kg, 29.49 kg, and 43.10 kg. Relationships between back squat one-repetition maximums, jump height, ratio (jump height/system mass) at each loading condition, mean jump height and ratio across loading conditions, change in jump height and ratio per condition (ΔJH, ΔRatio), and performance slope (slope of best fit line for system mass vs. jump height) were evaluated. Amongst all subjects, large (r>0.70), statistically significant correlations were found between back squat one-repetition maximums and jump height for the two lightest loading conditions, mean jump height, and performance slope. However, relationships varied by sex with mean jump height demonstrating the greatest consistency in both males and females. Mean jump height may be the most practical variable from this static jump protocol for monitoring training adaptations, particularly in relatively homogenous female collegiate athlete populations.

Purpose: to examine the relationship between isometric force characteristics (IF) and vertical jump height under various loading conditions. Sixty-three collegiate athletes participated in this investigation. Athletes performed static jump (SJ) and countermovement jumps (CMJ) with 0 and 20kg, and isometric mid-thigh pulls on a force plate. Force-time curve analysis was conducted for each isometric pull and jump to determine force related characteristics. Jump height (JH) was derived from flight time. Isometric forces were normalized using allometric scaling: absolute force/ (body mass(kg)0.67)= IPFa. Results: There was a strong positive correlation between isometric peak force and isometric rate of force development (IRFD). Stronger athletes had smaller decrements in jump height with additional loading. Conclusion: The ability to produce higher peak and instantaneous forces and IRFD is related to JH and smaller differences between weighted and unweighted jumps. A weighted jump may be a practical method of assessing relative strength levels.

INTRODUCTION: The prevalence of ACL injuries is increasing in previous years. One of the most common studied kinematic risk factors related to ACL injuries is a resultant weak, leg axis alignment known as the dynamic knee valgus angle presented during a vertical drop jump [8, 14, 15]. Hewett et. al. concluded that a knee valgus angle was a primary predictor of the mechanism that leads to an ACL rupture [8]. By increasing the excessive knee valgus angle during a two-legged DVJ, an athlete is in turn increasing the possibility of a high knee valgus moment, which can increase the anterior tibial translation as well as the load on the ACL several-fold and the chances for an ACL tear [4]. METHODS: In our study, ten collegiate female participants, including ballet and non-ballet athletes performed two-legged DVJs for 6 different flexor and extensor muscles while digital recordings of knee valgus angle were captured at initial contact and push off with simultaneous collection of EMG data. RESULTS: Results displayed statistical significance for the average valgus angle to estimated GRF ratio for the non-dominant leg at push-off between the ballet and non-ballet athletes (0.8 ± 0.43 vs. 1.8 ± 0.33 degrees/N, p < 0.05). In addition, we also found that the hip extensor activity significantly increased for the non-ballet group and that the lateral thigh CCI noticeably increased for the non-dominant leg for the non-ballet group, which could be indicative of the noticeable difference in the biceps femoris muscle activation for the non-ballet group when comparing sports type. In addition, statistically significant interactions between sports type and leg type for vastus medialis and gluteus maximus were produced. Observed results also indicated that there was an increase in overall variability for the dominant leg of the non-ballet athletes amongst all studied muscles and for the non-dominant leg for the ballet group specifically studying the gluteus maximus muscle activity. DISCUSSION: Relatively, the non-ballet group could be at a higher risk for increase in femoral adduction, hip adduction, and tibial external rotation, and overall predict a larger knee valgus moment; therefore, the non-ballet group could potentially be at a higher risk for an ACL injury than the ballet group. In addition, there is potential in continued research of neuromuscular differences between ballet and non-ballet athletes to further investigate the vastus medialis and the gluteus maximus muscle activations as well as to investigate the knee valgus moment values.

No description available.

The primary objective of this study was to analyze the relationship between testosterone levels and vertical jumping performance in elite men and women athletes. The secondary objective was to verify whether testosterone levels and vertical jumping performance were different in men and women athletes and if those measurements were different between different athletic groups. Seventy (22 women and 48 men) elite athletes in track and field (sprinters), handball, volleyball, and soccer competing at national and international levels participated in the study. After 10 hours of fasting and 1 day of rest, blood samples were drawn from the antecubital vein for determining testosterone levels. Vertical jumping tests consisted of counter-movement jumps conducted on a resistive platform connected to a digital timer. Resting testosterone levels in women were 9.5% of those of the men (respectively 0.62 ± 0.06 ng·ml−1 and 6.49 ± 0.37 ng·ml−1; p < 0.001). Countermovement jump performance was significantly different between women and men athletes, with women's jumping ability 86.3% of that of men (p < 0.001). A significant positive relationship was identified between testosterone levels and vertical jump performance when all data where considered (r = 0.61, p < 0.001, n = 70).

This present study was intended to identify the reliability and validity of the Vert™ device when compared to a Switch mat. Vert is a wireless device intended to measure jump count and jump height through an application on a smartphone or tablet and the Switch mat provides jump height using wireless sensors. Jump height is an important factor in many sports such as volleyball and basketball and it is important to have devices that coaches and trainers can use for testing that they can rely on. If this device is found to be valid and reliable, coaches and trainers could potentially use it in more practical settings such as practice and games due to the portability and small size. This study consisted of 6 subjects who volunteered. The switch mat was connected to the device to display the jump height immediately after the jump. The Vert sensor was clipped onto the subject’s hip near the center of mass and the jump count and height were then displayed on an app. The subjects completed a series of warm-ups followed by 3 sets of 5 repetition countermovement jumps while using both devices to collect the data. The total 15 jump heights from these 3 sets of 5 were then analyzed using Pearson correlation analysis as well as a paired sample T-test. The jump height recorded from the Vert was consistently about 10 cm off from the jump height of the switch mat, which for a volleyball player, could be the difference between blocking and missing the ball. The results of this study showed that the Vert device is reliable but not practically valid. If technical improvements were made to the device to correct the height components the device could potentially be used in place of a force plate or switch mat when conducting athlete testing but the device is not currently valid for practical use.

The purpose of this study was to investigate the effects of Nordic hamstring strength training (NHST) program on (1) leg power, (2) vertical jump, (3) and knee proprioception measurements of 10-12 years old male basketball players. Nordic Hamstring Strength Training (NHST) group (N=16), participated in basketball training plus in Nordic hamstring strength training, while the control group (N=11) participated in basketball training only. Subjects were tested before and after 5-week training program for, vertical jump, isokinetic leg strength and knee proprioception. Each subject who agreed to participate in this investigation signed a consent form along their parent. Pre and post test differences between experimental and control group was investigated by MANOVA and paired sample t-test was used to evaluate the differences between pre and post tests of both groups. There was no significant difference in pre and post test results of NHST and control group. There were statistically significant increase in concentric quadriceps and hamstring strength, eccentric quadriceps strength, conventional H:Q strength ratio, and vertical jumping measurements in experimental group between the pre and post tests. It can be concluded that NHST program combine with basketball training has beneficial effects on the leg strength and H:Q strength ratio. These findings also suggest that hamstring exercise may be beneficial or helpful for preventing the hamstring injury occurrence and improving the physical performances such as jumping ability.

Made available in DSpace on 2016-12-06T17:07:17Z (GMT). No. of bitstreams: 1 Raquel Petry.pdf: 1234634 bytes, checksum: d18697901e3f94a1e978e7524fb895e4 (MD5) Previous issue date: 2008-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In Rhythmic Gymnastics, the body element jump is one of sportive gestures that is harder to achieve to correct execution. As the gymnast executes the jump, vertical displacement is indispensable. The lift of the centre of gravity increase of gymnast is one of the basic requisites to jump validation. The general objective of this study is to analyze the vertical displacement on four different jumps realizing by rhythmic gymnastic in distinct training phases. Eight gymnasts of juvenile category of Florianópolis Team, with mean of age at 13,37 + 0,74 years old took part of this study. The data mining was executed at the Instituto Estadual de Educação gymnasium. The vertical displacement jumps were measured by a soil contact measuring system, projected and made at the Labin/UDESC. The statistic analysis was made by the means of software SPSS 14.0. The data was analyzed by descriptive and inferential statistic where ANOVA 4x6 was applied among participants with Bonferroni´s correction and Pearson´s correlation, with significance level of p<0,05. By obtained results it was verified which is, or not, an effect between training phases and the height of jumps (p=0,111; &#61544;2 = 0,218). There is not an effect between training phase x jump and the height of jumps (p=0,239; &#61544;2 = 0,153). However, it was verified that there`s a strong effect between the jump's jump height and type (p=0,000; &#61544;2 = 0,937). It could be perceived that the variability of height depends almost exclusively on the type of jump. It also could be perceived that there's no correlation between the height of gymnast and the height of jump under analysis. Although a restrict number of individuals were observed on this study, it could be verified that the height of jumps is directly associated to its type and the complexity of jump don't determine a higher height. The quantitative evaluation of specific movements of the Rhythmic Gymnastic (RG), like the jump shall be a support to improve of this technique serving, thus, like helping elements to the training, increasing the performance of the proper sportive expressions in search of optimal results. / Na Ginástica Rítmica, o elemento corporal salto é um dos gestos desportivos mais difíceis de ser realizado corretamente. O deslocamento vertical durante a execução do salto torna-se imprescindível. A elevação do centro de gravidade da ginasta é um dos requisitos básicos para a validação do salto. O objetivo geral deste estudo é analisar o deslocamento vertical dos quatro diferentes saltos realizados por praticantes de Ginástica Rítmica em diferentes fases do treinamento. Participaram deste estudo oito ginastas da categoria juvenil da Equipe de Florianópolis, com média de idade de 13,37 + 0,74 anos. A coleta de dados foi realizada no ginásio do Instituto Estadual de Educação. O deslocamento vertical dos saltos foi mensurado através de um sistema de medição de contato com o solo idealizado e confeccionado no Labin/UDESC. A análise estatística foi realizada pelo software SPSS-14.0. Os dados foram analisados através de estatística descritiva e inferencial, onde foi aplicada Anova 4X6 dentre participantes com correção de Bonferroni e correlação de Pearson, com nível de significância de p<0,05. Através dos resultados obtidos verificou-se que não existe um efeito entre a fase de treinamento e a altura dos saltos (p=0,111; &#61544;2=0,218) e também não existe um efeito entre a interação fase de treinamento X salto e a altura dos saltos (p=0,239; &#61544;2=0,153). Entretanto, pôde-se verificar que existe um forte efeito do tipo de salto em relação à altura do salto (p=0,000; &#61544;2=0,937). Pôde-se perceber que a variabilidade da altura do salto depende quase que exclusivamente do tipo do salto. Pôde-se verificar, também, que não há correlação entre estatura das ginastas e a altura dos saltos analisados. Apesar do número restrito de sujeitos neste estudo, pode-se verificar que a altura dos saltos está diretamente associada à sua forma e que a complexidade do salto não determina uma maior altura. A avaliação quantitativa de movimentos específicos do esporte, como o salto na GR poderá auxiliar no aprimoramento desta técnica servindo, portanto, como elementos acessórios ao treinamento melhorando o desempenho dos próprios gestos desportivos na busca de resultados ótimos.