Poster Session III, July 15th 2010 — Abstracts Inertial sensors in sports: application to vertical jumps

Abstract Countermovement jump (CMJ) height is typically estimated by applying the equation of free-fall to the motion of the centre of mass (CM) during the flight phase. In field setting, this is generally done using optical cells/contact mats. The reliability of the estimate is strongly affected by the subject's expertise in executing the jump. Wearable inertial measurement units (IMU), containing 3D accelerometers and gyroscopes, can provide similar information regardless to execution constraints. However, the interpretation of signals still requires the development of computational techniques and of models embodying the specific motor task. This study aims to verify whether IMU can be used to assess CMJ performance. Twenty-eight college students (67±13 kg, 1.73±0.09 m) performed 5 CMJ, with a 3-min rest in between. A wireless IMU (Sensorize, Italy) was placed using an elastic belt around the trunk at L5 level. Sensor accelerations, influenced by trunk bending, were expressed in a global reference system using the gyroscopes. Flight time (T) was identified when the vertical acceleration (az) was lower than gravity. Subsequent numerical integration of az provided velocity and height of the centre of mass at take-off. These quantities and the ballistic law of motion were used to estimate jump height (H). A stereophotogrammetric system (Vicon MX, UK) and a force plate (Bertec, USA) were used to obtain reference values for H (Hr) and T (Tr). ANOVA for repeated measurements ( p 0.05 ) and Pearson's correlation coefficient evaluated statistical differences between H and Hr and T and Tr, respectively. Intra-individual reliability was assessed by means of the Intraclass Correlation Coefficient (ICC). IMU and reference values were highly correlated (H: r = 0.9 ; T: r = 0.9 ) and presented no statistical difference for both H and T. Relevant differences were 2±8% and 4±3% for H and T, respectively. High intra-subject IMU reliability was found (ICCJ=0.834, ICCT=0.868). This study showed how the combination of a 3D accelerometer and gyroscope can lead to an accurate and repeatable estimate of jump height. CMJ height estimate does not suffer from any assumption about the performed task and it is not affected by the subject's expertise (reliable for elderly and young populations). Furthermore, since the IMU is worn by the athlete, vertical jumps can be performed on any surfaces such as grass, sand, springboards, etc

Effect of Number of Players and Maturity on Ball-Drills Training Load in Youth Basketball

This study aimed to assess the basketball ball-drills workload analyzing: (1) the effect of varying the number of players involved on physiological and technical demands; (2) the temporal changes in players’ responses across bouts; and (3) the relationship of players’ workload with their maturation status and training age. Twelve young male basketball players (mean ± SD; age 13.9 ± 0.7 years; height 1.76 ± 0.06 m; body mass 65.7 ± 12.5 kg; HRmax 202 ± 8 beat·min−1) completed three bouts of 4 min interspersed by 2 min of passive recovery of two vs. two and four vs. four ball-drills. The mean percentage of HRmax (%HRmax) and ratings of perceived exertion (RPE) were collected. Technical actions (TAs) (dribbles, passes, shots, interceptions, steals, rebounds, and turnovers) were calculated through notational analysis. Players’ genitalia development (GD) and pubic hair (PH) growth were assessed using Tanner scale. Results showed a higher %HRmax (p = 0.018), RPE (p = 0.042), dribbles (p = 0.007), shots (p = 0.003), and rebounds (p = 0.006) in two vs. two compared to four vs. four condition. Furthermore, a statistical difference was found for %HRmax (p = 0.005) and number of passes (p = 0.020) between bouts. In addition, no correlation between GD, PH, and training age with %HRmax, RPE, and TAs was found. These findings suggest that variations of the number of players involved affect ball-drills workload and that ball-drills training intensity varies across bouts. Finally, ball-drills elicit an adequate training stimulus, regardless of players’ maturation status and training age

Heart rate responses and technical-tactical aspects of official 5-a-side youth soccer matches played on soil and artificial turf.

Using a randomized crossover design, this study aimed to compare the heart rate (HR) responses and match analysis parameters (i.e., type of action; the number of players involved in an action; the number of passes performed in a collective action; precision of the shots; lost balls; ball interceptions; dribblings; and tackles) of official 5-a-side youth male soccer matches played over 2 pitch surface (i.e., clay vs. artificial turf) conditions. Twenty-two young male soccer players (age 8.3 6 0.4 years) engaged in 2 consecutive 15-minute periods in each experimental condition. During the match, 53% of HR responses exceeded 85% of the individual HRpeak. No difference emerged between both pitch surfaces and match periods for HR and match analysis indicators. The two 15-minute periods resulted in being appropriate for 8-year-old players, in resembling the intensity of play and the intermittent nature of adult soccer. The similar HR responses and technical-tactical patterns observed on the 2 surfaces indicate that youth match play is not affected by differences in pitch surface. To support the development of individual and team skills of young soccer players, coaches are advised to prioritize game knowledge based on divergent thinking and experience, rather than traditional teaching based on instructions

Effects of competition level on the centre forward role of men’s water polo.

This study aimed to compare specific technical and tactical indicators of the team and centre forward role of Euro League, and Italian Serie A1, Serie A2, and Serie B men's water polo club competitions. A notational analysis was performed on 21 water polo matches to evaluate the occurrence of technical and tactical team and centre forward indicators, highlighting differences among championships according to chi-square analyses. Differences emerged for Counterattack (P < 0.001) and Power-Play (P < 0.001) possessions, Even (P < 0.001; Euro League: 3 ± 1, Serie A1: 3 ± 2, Serie A2: 3 ± 2, Serie B: 6 ± 4) and Power-Play (P = 0.001) goals, and exclusions and penalties (P = 0.008) of the team during Even possessions. Relatively to the role analyses, effects emerged for perimeter players playing events (P = 0.049), as well as for centre forwards' goals (P = 0.007) and exclusions and penalties (P < 0.001; Euro League: 8 ± 1, Serie A1: 6 ± 2, Serie A2: 6 ± 2, Serie B: 3 ± 2) occurring at the end of Even possessions. Therefore, in Euro League, and Italian Serie A1 and Serie A2, teams perform a high occurrence of Power-Play possessions following up an exclusion, especially achieved by the centre forward during Even possessions, while, in Italian Serie B, goals were mostly scored during Even possessions, with a relevant contribution from the centre forward rol

Race profiles of rowers during the 2014 Youth Olympic Games

Aim: Strategy plays a relevant role. The purpose of this study was to analyze the race profiles of youth athletes competing at the 2014 Youth Olympic Games over a distance of 1000-m. Methods: According to the competition outcome of sculling and sweep events, 48 male and 48 female youth (17\u201318 years) rowers were divided in medallist (W), not medallist (NW), qualified (Q) and not qualified (NQ) athletes. Time at 0\u2013500 m (T1) and 500\u20131000 m (T2) was considered. The average speed for T1 and T2 were normalized in relation to the average speed of the whole race. ANOVA for repeated measures was applied to performance 1xJ and 2-J during qualifying: 2 (sex: females vs. males) 9 2 (outcome: qualified vs. notqualified), repechages and semi-finals: 2 (sex: females vs. males) x 2 (outcome: FB vs. NFB) 9 2 (boat: 1xJ vs. 2-J) and final: 2 (sex: females vs. males) 9 2 (outcome: M vs NM) 9 2 (boat: 1xJ vs. 2-J). Results: Qualifying 1xJ show a difference (F(1, 44) = 57.76, p.001; ES = 0.75) and emerged only between competition sectors, with higher values for T1 (101.9 \ub1 1.7 %) respect to T2 (98.1 \ub1 1.7 %). Similarly, for repechages and semifinals phase 1xJ and 2-J, a difference (F(1,40) = 31.8, p.001; ES = 0.57) was found between competition sectors, with highest values for T1 (101.6 \ub1 2.3 %) and lowest for T2 (98.4 \ub1 2.3 %). For the final phase of the 1xJ and 2-J competitions, no main effect was found. In repechages and semifinals, rowers adopting a positive strategy (88 %), while during the final phase medallist (67 %) adopting a negative strategy. Conclusions: in this study emerges that athletes who adopted a negative strategy had more chance of winning respect to athletes who adopted a positive strategy. Reference Garland SW (2005) An analysis of the pacing strategy adopted by elite competitors in 2000 m rowing. Br J Sports Med 39:39\u201342

Multi-national perceptions on challenges, opportunities, and support structures for Dual Career migrations in European studentathletes

Despite Dual Careers (sports and education) and mobility of students being priorities in the funding policies of the European Commission, migrating student-athletes report severe challenges and decreased performance or dropouts at sport and academic levels. The objective of this study was to depict and assess the perceptions on challenges, support services, and their effectiveness in consideration of specific characteristics of participants and migrations. Based on a meta-synthesis and previous findings, a 50-items questionnaire was developed and completed by 245 student-athletes in 5 European countries. Participants with Dual Careers migration experience (n = 140) were considered for analyses of qualitative and quantitative (ordinal 5pt-Likert-scaled and metric) data on the Dual Career status, migration characteristics, received services, and outcomes. Chi-square-tests were conducted for differences between countries and genders at a significance level of p < .05. Country-related differences were found for experiences and intentions to migrate (X2(12) = 50.52, p<0.001), duration of the migration (X2(16) = 38.20, p = 0.001), financial support (X2(8) = 29.87, p<0.001), and decreased performances in academics (X2(16) = 56.12, p<0.001) and sports (X2(16) = 31.79, p = 0.01). Gender-related difference emerged in financial support (X2(4) = 10.68, p = 0.03), duration of the migration (X2(4) = 14.56, p = 0.01), and decreased academic performance (X2(4) = 10.57, p = 0.03). Tutoring and counselling support was ranked as the most effective support, especially when received from the academic field (4.0±1.0 pt) and others (4.1±0.8 pt), followed by online services from sport and academic sectors (both: 3.9±0.9 pt). Considering the pervasive globalization of sport and education, Dual Career migration can contribute to the development of a European sport culture. The high ratio of migrating student-athletes underlines the relevance of migrations in the field of Dual Careers. This study contributes to the literature by adding insights on practices, challenges, supports, and outcomes perceived by student-athletes migrating in Europe. Moreover, country- and gender-related differences support the consideration of specific characteristics and reveal critical factors in specific target groups. The findings contribute to identifying requirements and effective support measures in Dual Career migrations and can be used to improve support services

Communications Biophysics

Contains reports on four research projects.National Institutes of Health (Grant MH-04737-03)National Science Foundation (Grant G-16526)National Aeronautics and Space Administration (Grant NsG-496