| The stimulus-response process can be applied to a wide variety of research areas that contribute to the production or prevention of injury. First, the recovery strategies of older adults during a treadmill acceleration task were examined to determine if the biomechanics of failed recoveries resemble those of failed recoveries from a trip. The results showed that similar to failed recoveries from a trip, the failed recoveries on a treadmill had slower reaction times, shorter step lengths, and greater trunk flexion angles and velocities. Additionally, subjects who failed on the initial treadmill attempt were able to modified their recovery strategy to successfully recover on subsequent trials.; Second, the response times of young athletes (ages 8-16 years) performing a simulated baseball-fielding task were investigated. Reaction times and movement times were influenced by projected velocity of the baseball (26.8 and 33.5 m·s-1), by the attention condition (full-attention and attention-splitting), and by age, but not by gender. The results showed that subjects had sufficient time to respond to exit-velocities from 26.8 m·s -1 (8-9 years old group) to 33.5 m·s-1 (16 year old group). However, the accuracy of the response was negatively affected by baseball velocity. If the exit-velocities seen during actual competition exceed the calculated maximum exit-velocities for these age groups, then modifications to the game of baseball to reduce the actual exit-velocities may be warranted to reduce the potential for serious or catastrophic injury.; Third, differences in knee extensor muscle EMG and rate of change of moment prior to voluntary maximum concentric and eccentric contractions were determined. The EMG of the eccentric contractions was significantly smaller than that of the concentric contractions, while the rate of change of knee extension moment generally did not differ between the two conditions. During additional trials it was found that the initial EMG reflects he intended contraction condition versus the contraction condition that was actually performed. Overall, the difference between concentric and eccentric contractions observed during the period of the initial muscle activation implies that descending signals from the central nervous system include information that distinguishes between eccentric and concentric contractions. |
