Second-leg home advantage in the Copa Libertadores da América (2005-2015)

Aims: To investigate the home advantage (HA) in the Copa Libertadores da América (CLA) from 2005 to 2015. Methods: A naive analysis was applied considering how many times a team that played the second leg at home qualified for the next round. To verify differences between home, away and draw results, the Chi-square ( χ2 ) and the Full Bayesian Significance Test were applied. For the binomial variables ("Home" or "Away"), the probability of second-leg knockout occurrence was calculated. Results: The probability of second-leg HA varied from 27.27% to 63.64% suggesting fluctuations of second-leg HA during competitive phases (round of 16, quarterfinals, semi-finals and final matches) and decision forms (full time, goals away rule or penalty-shoots). Conclusion: The results counteract the common belief that there is a large advantage to playing the second match of a two-leg tie at home during all competition phases. Penalty-shots seemed to affect positively the second-leg HA. Despite the causes of second leg HA in CLA need to be better investigated, soccer coaches could to use these results to think better strategies to win your knockout matches.(AU)

Analysis of lower limb injuries in collegiate American football team: a 2-year prospective study / 体力科学

Collegiate American football injuries for two year seasons in Japanese Kansai Division I team were analyzed using injury rates (IR) per 1000 athlete-exposures (1000AE: one athlete-exposure was defined as a player participating in one game or one practice.), especially focusing on lower limb injuries. The overall game injury rate (GIR: 38.3) was significantly higher than practice injury rate (PIR: 13.1) (X²=12.355, p < 0.05). The difference between GIR in 2008 season (50.8) and in 2007 season (25.7) was significant (X²=8.235, p < 0.05). The lower extremity injuries approximately occupied 60% of all injuries, especially GIRs of both ankle inversion sprains (3.8) and anterior cruciate ligament (ACL: 3.3) injuries being much higher. PIR in this study was higher than the rates of collegiate American football teams in the U.S.A., especially PIRs of knee ligament injuries (ACL and medial collateral ligament injuries) and ankle sprains (inversion and eversion sprains) being much higher. Regarding the occurrence of injury, GIR with contact in ACL injuries (2.8) and GIR without contact in ankle inversion sprains (2.4) were the highest. It is also necessary to change practice plans and circumstances so that the PIR of knee and ankle injuries could be reduced. Research is needed on injury prevention for knee and ankle injuries in the games and practices.

Relationship between helmet temperature and tympanic temperature during american football practice / 体力科学

Purpose: The purpose of this study was to examine the relationship among helmet surface temperature (Thl), head top temperature (Thd) and tympanic temperature (Tty) during American football practice in summer. Methods : The subjects were collegiate American football players. Temperatures were measured in August in 1993 and 1994. Thl, Thd and Tty were measured by infrared tympanic thermometers. Environmental temperatures that were measured were dry-bulb temperature (Td), wet-bulb temperature (Tw), globe temperature (GT) and wet-bulb globe temperature (WBGT) . Results: Significant correlations were observed among all measured temperatures (P<0.0001) . High coefficients of correlation were observed among Thl, Thd and GT. The highest relationships were observed between Thl and Thd (r=.727), and between Tty and Td (r=.766) . The coefficient of correlation between Tty and Thl was higher than that between Tty and Thd. Heat stress of the whole body (F1; heat stress factor: Tty, Td, Tw and WBGT, proportion=71.4%) and head environment factor (F2 ; helmet factor : Thl, Thd and GT, proportion=14.3%) were chosen in factor analysis. A close relationship was observed between both factors (r=.773) . Both GT and Thl showed a high correlation with Thd, which suggests the influence of radiant heat through a helmet on the whole body. Conclusion : The temperature in a helmet is a micro environment temperature surrounding the head. Accordingly, the heat load is reduced by taking the helmet off frequently during football practice.

A study of the isometric cervical extension strength of college american football players. Measured by a cervical extension machine / 体力科学

The purpose of this study is to evaluate and compare isometric cervical extension strength (extension strength) of college American football players belonging to different level leagues at the eight cervical positions measured by a cervical extension machine (Medx Inc.) and give some suggestions for preventing neck injuries. The subjects were American football players at N University (n=41) belonging to the first-level league and at G University (n=32) belonging to the third-level league. The findings were as follows.<BR>1. The isometric cervical extension strength/body weight of players at N University was sig-nificantly higher than that of G University at 72°, 54°and 36° (a neutral cervical position) .<BR>2. The extension strength/body weight of the linemen at N University was significantly higher at 108°, 54°and 36°than that of the linemen at G University. While there were no significant differences between universities in the eight cervical positions of back players herein referred to as‘backs’.<BR>In conclusion, it was shown that there were significant differences in the extension strength and the extension strength/body weight between teams of different levels. The differences tended to be larger between the linemen than between the backs. Therefore, it was suggested that the evaluation of neck muscle strength was important for preventing neck injuries especially caused by a mismatch of players at different performance levels.

A study of neck muscle strength in college american football players-Based on performance level, year and experience- / 体力科学

A study was conducted to evaluate and compare neck muscle strength between two levels of college American football players with the aim of preventing neck injuries. The subjects were American football players at N University (n=52) belonging to the first level league and American football players at G University (n=14) belonging to the third level league. The findings were as follows.<BR>1. The neck muscle strength of freshman players at N University tended to be lower than that of senior players.<BR>2. It was shown that the neck muscle strength/body weight of experienced American football players was 10-30% higher than that of inexperienced players.<BR>3. There was a significant difference in neck muscle strength/body weight between N University and G University in 1997. However, there was no significant difference between them in 1998, because neck muscle strength/body weight of G University players increased by 13-30% after neck muscle training for about nine months. It was suggested that coaching staff must evaluate the neck muscle strength of each player, especially in freshmen who have had no experience of American football, in order to prevent neck injuries because mismatch of performance level may cause catastrophic neck injury.