Aim: The aim of this study was to investigate the effects of performing an isometric conditioning contraction (CC) consisting of two sets of five seconds maximal voluntary contraction in physically active individuals prior to three sets of Loaded Squat Jumps (LSJ). Method: 5 males and 4 females (mean ± SD: age 25 ± 2 years, height 175 ± 10 cm, body mass 70 ± 15 kg) were assessed on their power output, force production, jump height and velocity on three sets of LSJ on two separate sessions. Each participant attended two sessions in randomized order: a control session (CON) and an experimental session (EXP) separated by at least two hours. The EXP session consisted of a 10 min warm-up followed by 2 x 5 seconds isometric CC, this was proceeded by another two minutes of rest before three sets of LSJ were performed, each set separated by a two-minute rest. During the CON session a two-minute rest, followed by three sets of LSJ, replaced the isometric CC sequence. Results: No significant improvement was found on any of the physical parameters assessed, comparing the CON and EXP session (p > 0.05). The results showed a variance on individual response were some subjects performed better after the CC and others did not . Conclusion: In conclusion, this study evaluated the effect of performing an isometric CC prior three sets of LSJ. The results indicate that an isometric CC consisting of two sets of five seconds maximal voluntary contraction is insufficient to enhance the performance in an LSJ.

Background: Teamgym is a relatively new and emerging sport that originating comes from Scandinavia. Teamgym differs a lot from the most known form of gymnastics, artistic gymnastic. For example artistic gymnastics is an individual sport, while teamgym is performed by 6-12 members in each team. In general gymnasts have to acquire many skills at a very young age like jumping, bouncing and twisting in different directions. A good jumping ability has been linked to a successful performance for gymnasts and is defined by a gymnast’s capacity to jump upwards and then perform series of forward and backward rotations in a successful way. Plyometric is a type of training based on the stretch- shortening cycle (SSC) and is often used to improve an athletes sprint and vertical jump ability. Studies indicate that these two components have been linked to a successful performance in gymnastics but there are no studies that are looking at this correlation in teamgym. Aim: The aim of this study was to investigate how strong the correlation is between the vertical jump height in counter movement jump with arm swing, drop-jump and 20, 25- meters sprint in young female teamgymnasts. Methods: Seventeen (17) female teamgymnasts participated to test their vertical jump ability by using countermovement jump with arm swing (CMJa) and drop-jump (DJ). Their sprint ability was tested through 20 and 25 meter sprint. The highest CMJa and DJ were correlated with the fastest time on 20 and 25 meter sprint. To study the relationship between the vertical jumps and the sprints, Spearman’s rank order correlation (rs) was used in SPSS version 20.0. If the correlation is between 0.30 to 0.49 (-0.30 to -0.49) it is considered as a medium correlation. Anything under these values is a weak correlation and everything above it is strong correlation. Result: CMJa showed a strong significant correlation with both 20 and 25 meter sprint and DJ showed a moderate non-significant correlation with both 20 and 25 meter sprint. When the weight was set as a control variable the CMJa showed a moderate non-significant correlation with both the sprints but DJ showed a strong significant correlation with both 20 and 25 meter sprint. Conclusion: No other studies have looked at the relationship between vertical jump and sprint ability in teamgym but the result of this study somehow reflects findings in studies looking at the same variables. The findings in this study can be useful for gymnastic coaches when they create training programs for their athletes. Coaches and gymnasts will know the value of a good jumping- and sprinting ability and that plyometric- and sprint training can improve the gymnasts skills. More research is needed on this type of gymnastics and future studies should look at these variables in a larger sample size and with more experienced test subjects.

Background: Teamgym is originally from Scandinavia and the first competition was held in Finland in 1996. The sport includes parts such as trampette, tumbling and floor programs which is performed by the whole team which often consists of six to twelve gymnasts. Trampette and tumbling program consists of three series of tumbles and vaults performed by six gymnasts of the team. The floor program is three minutes long and performed by the team. Female elite gymnasts are often short, lightweight and have a good strength and power and are very flexible and limber. Jumping movements are common in this sport especially to vault and floor programs. It is also preferable that the gymnasts achieves a high sprint speed in order to carry out the movements that are included in the sport. Plyometric training along with resistance training has proven to have positive effects on the gymnasts jumping ability. Especially the jumping ability is incredibly important for a gymnast and for its development in the sport. Plyometrics improves not only the acceleration during the sprint, but also increases the athlete’s strength in the lower extremity. Very few previous studies have been done on gymnastics, particularly in teamgymnastic. Aim: The aim of this study was to investigate if there is any linear correlation between vertical jump height and 10 and 15 meter sprint in teamgym gymnastics. Method: 17 young female teamgymnasts, 12-17 years old, were tested in 10 and 15 meter sprint and two different vertical jumps, countermovement jump with arm swing (CMJa) and squat jump (SJ). The highest was correlated with the fastest sprint time. To analyze the correlation between vertical jumps and sprint the Spearman’s rank correlation (rs) was used. Result: CMJa shows a moderate negative correlation to 10 meter sprint (rs = -0.447) and CMJa also shows moderate negative correlation to 15 meter sprint (rs = -0.488). SJ shows a weak negative correlation to 10 meter sprint (rs = -0.23). SJ also shows weak negative correlation to 15 meter sprint (rs = -0.16). When controlling for the weight, SJ and both sprints went from a weak correlation to a strong correlation. Conclusion: The strongest correlation was found between CMJa and 15 meter sprint. When controlling for the weight, SJ and both sprints went from a weak correlation to a strong correlation. The result showed that the test subjects jumped higher during CMJa than during SJ, with a median of 36.0 compared with 30.0 centimeters. No previous studies have examined these variables and their relationship on teamgymnasts. Further research should be done on the teamgymnasts, since very little previous research has been done in this area.

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.

Aim and objectives The aim of this study was to examine how different biomechanical, physiological and anthropometry variables relate to snowboard jump performance. The first objective was to investigate the differences in velocity at take-off, jumping height, jumping length and air-time (AT) in straight jumps and tricks with different degrees of rotations in a jump. The second objective was to identify which biomechanical and physiological parameters correlate with snowboard jump performance, which was defined as the ranking of the athletes’ best 720° jump subjectively determined by an experienced snowboard judge. Method Eleven students at Malung-Sälens Snowboard High-school performed straight jumps and backside rotations on a snowboard jump, while data on snow variables such as velocity at take-off, jumping height, jumping length and AT were collected. An experienced judge evaluated all 720° jumps. Participants also performed strength and flexibility tests to assess their physiological performance. The physiological tests included: 1RM squat, squat jump with weight equal to 40% of their 1RM squat weight, unweighted squat jump, countermovement jumps, countermovement jumps with arm swing, chin-ups, brutal bench and a modified sit and reach test. Results While performing the 720° rotations the riders had significantly higher jumping height and AT than during the 360° jumps. No significant correlations were found between the best subjectively judged 720° and jumping height, jumping length or AT. None of the physiological tests results produced significant correlations with subjectively judged snowboard performance. Conclusions When the participants performed a higher degree of rotation, jumping height and AT increased significantly. No relationships were observed between jumping height, jumping length, or AT with subjectively judged snowboard jump performance. It is believed that the rank of the best 720° was primarily based on the athletes’ personal riding style. The physiological tests showed no relationship to the subjectively judged snowboard jump performance. Other factors such as psychology, technique and coordination might be more important for performance.

Bakgrund: Hopphöjden är en viktig faktor inom volleyboll och kan vara direkt avgörande i spelsituationer. Drop jump (DJ) är en vanligt förekommande plyometrisk övning som används för att förbättra hopphöjden. Ett fåtal studier har påvisat den omedelbara effekten utav att implementera DJ i ett träningsupplägg. Syfte: Syftet med studien var att undersöka om ett set med fem repetitioner av DJ kan förbättra hopphöjden efter tre minuters aktiv vila. Avsikten med studiens upplägg var att det med enkelhet ska kunna implementeras i en matchsituation. Metod: Nio kvinnliga volleybollspelare på elitnivå deltog i studien i åldern 25±7 år, med vikt 73±6 kg och längd 172±8 cm. Deltagarnas hopphöjd testades med tre countermovement jump (CMJ) och 72 timmar senare utfördes fem DJ innan liknande CMJ utfördes. Hopphöjden uppmättes med Ivar jump system.   Resultat: Resultatet påvisade ingen signifikant förbättring i hopphöjd (p = 0,6) efter utförandet av fem DJ. Dock noterades en positiv trend då åtta av nio deltagare förbättrade sin hopphöjd med ±1,6 cm. Slutsats: Utförandet av fem DJ före en hopprestation kan ge positiv effekt. Ytterligare forskning krävs dock för att kunna fastställa slutsatsen och hur länge effekten håller i sig.

In this thesis, I introduce a promising framework for representing an air traffic flow (stream) and flow-management action operating under weather uncertainty. I propose to use a meshed queuing and Markov-chain model---specifically, a queuing model whose service-rates are modulated by an underlying Markov chain describing weather-impact evolution---to capture traffic management in an uncertain environment. Two techniques for characterizing flow-management performance using the model are developed, namely 1) a master-Markov-chain representation technique that yields accurate results but at relatively high computational cost, and 2) a jump-linear system-based approximation that has promising scalability. The model formulation and two analysis techniques are illustrated with numerous examples. Based on this initial study, I believe that the interfaced weather-impact and traffic-flow model analyzed here holds promise to inform strategic flow contingency management in NextGen.

To operate a production plant, one requires considerable amounts of power. With a wide range of energy sources, the price of electricity changes rapidly throughout the year, and so does the cost of satisfying the electricity demand. Battery technology allows storing energy while the electric power is lower, saving us from purchasing at higher prices. Thus, adding batteries to run plants can significantly reduce production costs. This thesis proposes a method to determine the optimal battery regime and its maximum capacity, minimizing the production plant's energy expenditures. We use stochastic differential equations to model the dynamics of the system. In this way, our spot price mimics the Uruguayan energy system's historical data: a diffusion process represents the electricity demand and a jump-diffusion process - the spot price. We formulate a corresponding stochastic optimal control problem to determine the battery's optimal operation policy and its optimal storage capacity. To solve our stochastic optimal control problem, we obtain the value function by solving the Hamilton-Jacobi-Bellman partial differential equation associated with the system. We discretize the Hamilton-Jacobi-Bellman partial differential equation using finite differences and a time splitting operator technique, providing a stability analysis. Finally, we solve a one-dimensional minimization problem to determine the battery's optimal capacity.

Introduction: Running economy (RE) is known to be a strong indicator for performance on long distance running. RE is improved by plyometric training through an increase in stiffness in the musculotendinous system. Stretch shorten cycle (SSC) is a function in the muscle where a contraction is preceded by a stretch or an eccentric action. Orienteering is an endurance sport where RE is important for performance. Purpose: The purpose of the study was to examine whether or not there is a correlation between jumping performance and performance on long distance running in young elite orienteers 16-19 years old. Methods: 34 young elite orienteers did drop jumps (DJ) and countermovement jumps (CMJ) on an ErgoJump Bosco System contact mat. In conjunction with the jumps time on a 5 or 7 km (for girls and boys respectively) running test was collected. Pearson's correlation test was then used to determine the correlation between jumping height and running velocity. Results: The jumping height of the CMJ was on average 30,46 cm and 28,24 cm for the DJ. The running velocity was on average 14,19 km/h. Pearson's correlation test for the correlation between DJ and running velocity was 0,463 and for the correlation between CMJ and running velocity it was 0,461. In both cases the significance was 0,006. Conclusions: There is a significant, moderate to strong correlation between jump height in DJ and CMJ and performance on long distance running on a running test in young elite orienteers.

I denna översiktsartikel granskades 17 randomiserade kontroll studier som undersökt hur excentrisk träning har påverkat hopphöjd, muskelstyrka och effektutveckling hos tränade och skadefria individer, med mål att svara på följande två frågeställningar; 1) ”Är excentrisk träning ett effektivt sätt att träna för att utveckla hopphöjd, muskelstyrka och effektutveckling för tränade och skadefria individer?” 2) ”Om det är det, hur bör denna träning i så fall se ut?”. Majoriteten av insamlade studier kunde inte urskilja några signifikanta förändringar till följd av excentrisk träning. Endast sex av 17 studier kunde påvisa akuta såväl som kortsiktiga signifikanta förbättringar av hopphöjd, muskelstyrka och effektutveckling. Dock ifrågasätts relevansen av dessa fynd då effektstorleken inte rapporterats i alla studier samt att utformningen av studierna varierat från en studie till en annan. Sammantaget lyckades inte de granskade studierna bevisa att excentrisk träning är en effektiv metod för att utveckla hopphöjd, muskelstyrka och effektutveckling hos tränade och skadefria individer. / In this review 17 randomized control studies were reviewed that had examined the effects of eccentric training regarding jump height, strength and power for trained and non-injured individuals. The purpose of the review was to answer the following two questions at issue; 1) “Is eccentric training an efficient method to enhance jump height, strength or power for trained and non-injured individuals?” 2) “If so, how should that training regime be designed?”. Most of the included studies could not distinguish any significant changes because of eccentric training. Only six out of 17 studies could show acute as well as short term significant improvements in jump height, strength and power. The relevance of these findings is questioned since effect size has not been reported in all the included studies. The variety between the different interventions in each study also makes it difficult to compare the results between one study and another. In conclusion, the reviewed studies failed to show that eccentric training is an effective method to enhance jump height, strength and power for trained and non-injured individuals.