Countermovement jump height: gender and sport-specific differences in the force-time variables.

The goal of this study was to assess (a) the eccentric rate of force development, the concentric force, and selected time variables on vertical performance during countermovement jump, (b) the existence of gender differences in these variables, and (c) the sport-specific differences. The sample was composed of 189 males and 84 females, all elite athletes involved in college and professional sports (primarily football, basketball, baseball, and volleyball). The subjects performed a series of 6 countermovement jumps on a force plate (500 Hz). Average eccentric rate of force development (ECC-RFD), total time (TIME), eccentric time (ECC-T), Ratio between eccentric and total time (ECC-T:T) and average force (CON-F) were extracted from force-time curves and the vertical jumping performance, measured by impulse momentum. Results show that CON-F (r = 0.57; p < 0.001) and ECC-RFD (r = 0.52, p < 0.001) are strongly correlated with the jump height (JH), whereas the time variables are slightly and negatively correlated (r = -0.21-0.23, p < 0.01). Force variables differ between both sexes (p < 0.01), whereas time variables did not differ, showing a similar temporal structure. The best way to jump high is to increase CON-F and ECC-RFD thus minimizing the ECC-T. Principal component analysis (PCA) accounted for 76.8% of the JH variance and revealed that JH is predicted by a temporal and a force component. Furthermore, the PCA comparison made among athletes revealed sport-specific signatures: volleyball players revealed a temporal-prevailing profile, a weak-force with large ECC-T:T for basketball players and explosive and powerful profiles for football and baseball players.

Power athletes and distance training: physiological and biomechanical rationale for change.

The development of power lies at the foundation of all movement, especially athletic performance. Unfortunately, training programmes of athletes often seek to improve cardiovascular endurance through activities such as distance training that are detrimental for the performance of power athletes, rather than using other means of exercise. Performance decrements from continuous aerobic training can be a result of inappropriate neuromuscular adaptations, a catabolic hormonal profile, an increased risk for overtraining and an ineffective motor learning environment. However, long, sustained exercise continues to be employed at all levels of competition to obtain benefits that could be achieved more effectively through other forms of conditioning. While some advantageous effects of endurance training may occur, there are unequivocal drawbacks to distance training in the power athlete. There are many other types of conditioning that are more relevant to all anaerobic sports and will also avoid the negative consequences associated with distance training.

Overview of safety issues concerning the preparation and processing of soft-tissue allografts.

With the increasing use of allograft tissue and the recent infections found in patients undergoing surgical procedures, the current practices that prepare grafts for implantation must be examined. Initially, most tissue banks harvest allografts aseptically. There are many steps in the different techniques of preparation and processing of allograft tissue. Before allograft tissue is ready for clinical use, it undergoes specific disinfection methods, according to the individual tissue bank's specific process. Tissue banks use in-process bactericidal and virucidal steps via physical cleaning, chemical treatments, or application of irradiation to the allografts (or some combination thereof). Gamma irradiation may also be used as a terminal processing method to reach an assurance of sterility after the allograft has been packaged. Because of the allograft toxicity potential, the use of ethylene oxide as a final tissue sterilization measure is really nonexistent. The role of the Food and Drug Administration and American Association of Tissue Banks in allograft tissue handling is presented, as well as the new rules that regulate tissue banks and affect their processing methods.