ANALYSIS OF MATCH AND TRAINING PERFORMANCE IN SOCCER USING GLOBAL POSITIONING SYSTEM TECHNOLOGY

It generally accepted that soccer is one of the most popular sports in the world. Thanks to technology development, a progressively increasing in studies about external load monitoring in soccer match and training were published. Currently, several are the systems available to simultaneously analyze movement patterns of many players during a soccer match, including video-based time motion analysis equipment and global positioning system (GPS) devices. However, the use of one of the first two methods depends on various factors linked to the strengths and weaknesses of each methodologies. As far as concern GPS technology, it has been demonstrated that GPS devices are reliable instruments for monitoring the true metabolic demands during intermittent or high-intensity exercises such as soccer activities. However, there are several concerns about the use of GPS device to assess the very high-speed bouts, short sprints and/or movements with many changes of direction, even more when the sample rate of the GPS device is low. Different studies have shown that reliability of GPS devices gradually decreases in relation to increasing number of changes of directions and accelerations and to reducing running distance. Thus, first aim of this thesis was to investigate the validity and accuracy of GPS technology with a sampling rate 6710Hz in order to evaluate if it could produce better information on brief activities speed during short shuttle runs. Supporting by GPS technology, categories of movement described in relation to speed, acceleration or power thresholds, difference between playing position, analysis of fatigue during the match and physical demand in different soccer population (i.e adult versus young) have been analyzed during the training or game by researchers to better understand the workload imposed. Results obtained, in adult male players during a soccer match, identified in the high-intensity distance covered an important indicators of match physical performance. Instead, in youth players most information is available for players between 12 and 17 yr of age but, for very young players (<11 yr of age), data describing the activity profile during match play are limited and thus a less clear picture of the movement demands of these developing players is evident. Contrarily, information on match analysis about women\u2019s soccer is relatively few and more confused if compared to those of men. Indeed, so far, there is not universally agreement upon standard velocity thresholds utilized to quantify the distances covered in different locomotor activities, especially for high-speed running and sprinting. However, just recently some studies have presented common recommendation that are now being adopted. Finally, it has been demonstrated that GPS technology could help to better evaluate the workload imposed by specific soccer training. In the last years, the methodology in soccer is changing and it became more difficult to check and program training in order to prevent injury. Not enough time is spent on physical conditioning without ball. Commonly, several technical and tactical exercises are considered the main activities during the soccer. The \u201cmodern\u201d problem could be monitoring the global training load imposed from these type of training modalities. In this contest, the new available technologies could help coaches and sport scientists to better assessed the soccer training workload. Unfortunately, few studies investigated the relationship between GPS data and muscle fatigue after soccer-specific training sessions, and to our knowledge no data are available about the muscle impairments after different soccer training modalities and their relationship with external workload calculated using GPS devises. Therefore, the aims of this thesis were to describe the use of GPS technology in soccer. Four studies are developed in which the purposes were: 1) to evaluate the accuracy and inter-unit variability of a GPS device with a sampling rate of 20Hz for measuring mean and speed of shuttle runs; 2) to characterize match running performance of very young soccer players and evaluate the relationship between these data and physical capacities and technical skills; 3) to examine high-intensity distance covered during matches by elite female soccer players using different velocity thresholds and 4) to compare the decay in muscle performance after soccer-specific aerobic and traditional interval running training session

Untangling the Immunological Implications of Nadir on CD4+ Cell Recovery during Suppressive Highly Active Antiretroviral Therapy

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Physical capacity and match running performance in very young soccer players

Aim. The aim of this study was to analyze match running performance in relation to age and individual physical capacity in youth soccer players aged 8-10 years. Methods. Physical capacity of 12 under-10 (U10) and 15 under-8 (U8) male players was assessed by counter movement jump (CMJ), 20 meter shuttle run (20m-SR) and 10, 20 and 30 meters (10m, 20m and 30m) sprint tests. Shuttle dribble test (SHD) and slalom dribble test (SLD) were also performed to evaluate technical ability. Time motion analyses by global positioning system (K-Gps 10Hz, K-Sport) were performed during 30 (200 observations) official matches (lasting three equal periods of 15-min). Results. U10 vs U8 showed a better shuttle-running performance (1215\ub177 vs 872\ub178m, p<0.005), a lower sprint time on 20m (4.15\ub10.05 vs 4.38\ub10.07s, p<0.05) and 30m (5.72\ub10.06 vs 6.31\ub10.08s, p<0.0001) and a better technical ability (SDL: 10.7\ub10.2 vs 11.8\ub10.2, p<0.001; SHD: 22.3\ub10.3 vs 29.4\ub10.7s, p<0.0001). No differences were observed in CMJ and 10m. U10 covered higher total (3437\ub1137 vs 2348\ub1124m, p<0.0001) and high-intensity distance (1455\ub1104m vs 992\ub1116m, p<0.005) than U8. Distance covered at high-intensity in the third time was not significantly different from first and second time both for U10 and U8. A linear relationship (r2=0.74, p<0.0001) was observed between high-intensity distance and 20m-SR. Conclusions. This is the first study characterizing the match running activity of very young soccer players. If confirmed in a larger population, these data could be used by coaches and support staff as starting point in the design of training programs

HIGH-INTENSITY DISTANCE IN ELITE FEMALE SOCCER PLAYERS BASED ON A GENDER-SPECIFIC THRESHOLD

Introduction The total distance covered in elite matches by female soccer players is relatively lower than their male counterparts (Bradley et al. 2014). The majority of female match play is spent in low-intensity activities with high-intensity distance been 30% lower than male players (Andersson et al. 2010). To date, studies on female players utilized the same absolute velocity threshold of male players despite female player having a lower physical capacity than male players (Bradley and Vescovi, 2015). The aim of this study was to examine high-intensity distance covered during matches by elite female soccer players using different thresholds. Methods Nineteen elite female players participated in this study (age 23\ub14 yr; height 165\ub17 cm; body mass 54.7\ub16.5 kg). Maximal oxygen consumption (VO2max) and respiratory compensation threshold (VT2) were determined by graded exercise test to exhaustion on a motorized treadmill. Players activities across 6 friendly matches (32 observations) were tracked by Global Positioning System (K-Gps 10hz, K-Sport, Italy). Distance covered in total (TD) and at high-intensity (HID) were evaluated. The latter was calculated using both the typical male speed threshold of 15 km\ub7h-1 (MALE) and an individual speed threshold (IND) corresponding to VT2 (Hunter et al. 2015). Results Players VO2max was 49.1\ub13.7 mL\ub7kg-1\ub7min-1 and occurred at a speed value of 14.7\ub10.8 km\ub7h-1. VT2 corresponded to a running speed of 13.5\ub10.9 km\ub7h-1. The total distance covered was 7726\ub1891 m with HID higher (p<0.0001) in IND (1125\ub1533 m) than in MALE (785\ub1353 m). When expressed as percentages of TD, HID was 14.4\ub15.8% in IND and 9.9\ub13.8% in MALE. Discussions These data demonstrate in female soccer that the quantification of high-intensity running activities during match play can be impacted by applying relative or absolute speed thresholds. Even if arbitrary speed thresholds enable longitudinal monitoring of match-demands and comparison within and between players/teams/gender, the utilization of individualized speed threshold should be pursue in order to quantify the correct exercise stimulus in female soccer players. Further studies are needed to understand the best method characterizing the multiple transitions between intensity-domains in female soccer. References Andersson HA, Randers MB, Heiner-Moller A, Krustrup P, Mohr M. (2010). J Strength Cond Res. 24, 912-919. Bradley PS and Vescovi JD. (2015). Int J Sport Phys & Perf. 10, 112-116. Bradley PS, Dellal A, Mohr M, Castellano J, Wilkie A. (2014). Hum Mov Sci. 33, 159-71. Hunter F, Bray J, Towlson C, Smith M, Barrett B, Madden B, Abt G, Lovell R. (2015). Int J Sport Phys & Perf. 36, 41-48. Contact [email protected]

Match running performance and physical capacity profiles of U8 and U10 soccer players

Aim This study aimed to characterize match running performance of very young soccer players and evaluate the relationship between these data and physical capacities and technical skills. Methods Distances covered at different speed thresholds were measured during 31 official matches using GPS technology in U10 (n = 12; age 10.1 ± 0.1 years) and U8 (n = 15; age 7.9 ± 0.1 years) national soccer players. Counter movement jump performance (CMJ), 20 m shuttle running (20 m-SR), linear sprint performance (10, 20, 30 m), shuttle (SHDT) and slalom dribble tests (SLDT) were performed to determine the players physical capacities and technical skills. Results Physical capacities and technical skills were higher in U10 versus U8 players [P 0.05, ES: 0.74). The U10 players covered more total (TD) and high-intensity running distance (HIRD) than their younger counterparts did (P 0.05, ES: 0.99). TD and HIRD covered across the three 15 min periods of match play did not decline (P > 0.05, ES: 0.02–0.55). Very large magnitude correlations were observed between the U8 and U10 players performances during the 20 m-SR versus TD (r = 0.79; P < 0.01) and HIRD (r = 0.82; P < 0.01) covered during match play. Conclusions Data demonstrate differences in match running performance and physical capacity between U8 and U10 players, and large magnitude relationships between match play measures and physical test performances. These findings could be useful to sports science staff working within the academies

Remodeling of cholinergic input to the hippocampus after noise exposure and tinnitus induction in Guinea pigs

Here, we investigate remodeling of hippocampal cholinergic inputs after noise exposure and determine the relevance of these changes to tinnitus. To assess the effects of noise exposure on the hippocampus, guinea pigs were exposed to unilateral noise for 2 hr and 2 weeks later, immunohistochemistry was performed on hippocampal sections to examine vesicular acetylcholine transporter (VAChT) expression. To evaluate whether the changes in VAChT were relevant to tinnitus, another group of animals was exposed to the same noise band twice to induce tinnitus, which was assessed using gap‐prepulse Inhibition of the acoustic startle (GPIAS) 12 weeks after the first noise exposure, followed by immunohistochemistry. Acoustic Brainstem Response (ABR) thresholds were elevated immediately after noise exposure for all experimental animals but returned to baseline levels several days after noise exposure. ABR wave I amplitude‐intensity functions did not show any changes after 2 or 12 weeks of recovery compared to baseline levels. In animals assessed 2‐weeks following noise‐exposure, hippocampal VAChT puncta density decreased on both sides of the brain by 20–60% in exposed animals. By 12 weeks following the initial noise exposure, changes in VAChT puncta density largely recovered to baseline levels in exposed animals that did not develop tinnitus, but remained diminished in animals that developed tinnitus. These tinnitus‐specific changes were particularly prominent in hippocampal synapse‐rich layers of the dentate gyrus and areas CA3 and CA1, and VAChT density in these regions negatively correlated with tinnitus severity. The robust changes in VAChT labeling in the hippocampus 2 weeks after noise exposure suggest involvement of this circuitry in auditory processing. After chronic tinnitus induction, tinnitus‐specific changes occurred in synapse‐rich layers of the hippocampus, suggesting that synaptic processing in the hippocampus may play an important role in the pathophysiology of tinnitus.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150542/1/hipo23058.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150542/2/hipo23058_am.pd