The purpose of the present study was to investigate the influence of muscle fibre composition and stature on fractionated patellar reflex times in ten healthy untrained men (mean age: 23.3 years, SD 3.1; mass: 65.9 kg, SD 8.5; height: 172.3 cm, SD 5.3). Biopsies were taken from the right vastus lateralis muscle. Using staining for myofibrillar adenosine triphosphatase after pre-incubation at pH 4.3 and 4.6, muscle fibres were classified into slow twitch (ST), fast twitch, oxidative-glycolytic (FTa) and fast twitch, glycolytic (FTb) fibres. Total patellar reflex time (TRT) and its fractionated components--reflex latency (LAT) and reflex motor time (MT)--were obtained from the mean of ten trials in each subject whilst performing Jendrassik's maneuvre. The TRT, LAT and MT were 77.7 ms, SD 16.5, 23.4 ms, SD 1.3 and 54.2 ms, SD 16.3, respectively. The LAT was significantly correlated to the percentage number of ST (r = 0.758, P less than 0.05) and FTa fibres (r = -0.657, P less than 0.05), fast twitch:slow twitch ratio (r = -0.799, P less than 0.01) and to the height of the subjects (r = 0.901, P less than 0.001), whereas TRT and MT were not significantly correlated with either fibre types or the height of the subjects. From these results it can be concluded that the LAT during the patellar reflex is influenced by muscle fibre composition and the length of the sensory and/or motor nerve.
AbstractThe purpose of this study was to investigate the hypothesis that pole vaulters regulate their stride length during the approach run, and to determine the eŠects of diŠerently regulated gait patterns on take-oŠ velocity and performance. The approach runs and take-oŠ movements of ten male pole vaulters were analyzed. It was revealed that each pole vaulter regulated his gait pattern in the approach run in order to adjust for the distance to the toe-box at take-oŠ, in a similar way to the technique used by long jumpers and triple jumpers. The standard deviation of the distance to the toe-box at take-oŠ and the length of each step in the approach run showed no signiˆcant diŠerence between high-and low-performance-level vaulters. However, vaulters with a higher personal best started to adjust their stride length earlier than vaulters with a lower personal best, and hadˆnished most of their run-up adjustment by the second to last stride. To clarify the eŠect of run-up adjustment on the velocity in the take-oŠ phase, the subjects were classied into three groups according to the timing of their adjustment: Early, Medium, and Adjacent. It was found that the take-oŠ velocity of Early Adjusters tended to be higher than in the other groups, and that Adjacent Adjusters had the lowest velocity.The presentˆndings suggest that in order to perform well in the pole vault, it is important for the vaulter to regulate his stride length in the approach run, rather than performing a stereotyped run-up. In addition, regulation of stride in theˆrst half of the approach run and avoidance of stride regulation immediately before take-oŠ seem to be more eŠective for achieving better performance.
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