Validity and reliability of an inertial sensor device for specific running patterns in soccer

Electronic performance tracking devices are largely employed in team sports to monitor performance and improve training. To date, global positioning system (GPS) based devices are those mainly used in soccer training. The aim of this study was to analyse the validity and reliability of the inertial sensor device (ISD) in monitoring distance and speed in a soccer-specific circuit and how their performance compare to a GPS system. 44 young male soccer players (age: 14.9 ± 1.1, range 9– 16, years, height: 1.65 ± 0.10 m, body mass: 56.3 ± 8.9 kg) playing in a non-professional soccer team in Italy, participated in the study. We assessed the players trough a soccer running sport-specific circuit. An ISD and a GPS were used to assess distance and speed. Data was compared to a video reference system, and the difference were quantified by means of the root mean square error (RMSE). Significant differences were found for both GPS and ISD devices for distance and speed. However, lower error for distance (dRMSE 2.23 ± 1.01 m and 5.75 ± 1.50 m, respectively) and speed (sRMSE 0.588 ± 0.152 m*s–1 and 1.30 ± 0.422 m*s–1, respectively) were attained by the ISD compared to the GPS. Overall, our results revealed a statistically significant difference between systems in data monitoring for either distance and speed. However, results of this study showed that a smaller error was obtained with the ISD than the GPS device. Despite caution is warranted within the interpreta-tion of these results, we observed a better practical applicability of the ISD due to its small size, lower cost and the possibility to use the device indoor

The analysis of endurance, speed and explosive strength in young football players

Introduction Endurance, speed and explosive strength are determinant factors of sporting performance for football players (Hoff & Helgerud, 2004). An evaluation of these abilities is fundamental in young subjects, who have still not completed their maturation, to plan an individualised and effective training program (Fernandez-Gonzalo et al., 2010). The aim of this study was to examine the level of variability in endurance, speed and explosive strength of lower limbs among young football players. Methods Sixteen male players with 5 years of experience playing football and participating in the “Giovanissimi Regionali” amateur championship (14.00 years old ± 7 months; 57.5 ± 6.66 kg weight, 167.25 ± 6.97 cm height, 13.74 ± 4.40 % fat mass; 86.32 ± 4.46 % lean mass; 63.06 ± 4.69 % muscle mass) were tested. Endurance and speed were evaluated with the Cooper test and 30 m sprint test, respectively. Sargent jump and standing broad jump test were used to measure the explosive strength of lower limbs. The variability percentage of anthropometric features and motor abilities was analyzed calculating the coefficient of variation (CV) within the group. Values were considered significant at p<0.05. Results The players showed a higher variability in weight than stature (CV: 11.59% vs. 4.17%). In particular, weight variation was mainly due to a higher difference in fat mass than muscle mass percentage (CV: 32.03% vs. 7.44%). The explosive strength of lower limbs measured during vertical jump (38.88 ± 4.62 cm) was the ability more changeable (CV: 11.88% vs. 8.67%, 8.57% and 4.83%) compared to the same measured by standing broad jump (194.69 ± 16.88 cm), endurance (2780.00 ± 238.36 m) and speed (4.54 ± 0.22 s). Conclusion The increased variability in the elevation of vertical jump might be associated with a higher variation in fat mass and coordinative abilities among young football players. On the other hand, the lower variability in muscular mass might explain the scarce difference in speed. In conclusion, the explosive strength of lower limbs appears to be the ability that depends mostly on age. This data is preliminary because this study is still in progress and extending on a larger scale. References Hoff, J. & Helgerud, J. (2004). Endurance and Strength Training for Soccer Players. Sports Med, 34, 165-180. Fernandez-Gonzalo, R., Souza-Teixeira, F., Bresciani, G., García-López, D. et al. (2010). Comparison of technical and physiological characteristics of prepubescent soccer players of different ages. J Strength Cond Res, 24,1790-8