The influence of motor unit composition and stature on fractionated patellar reflex times in untrained men

Abstract

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.

Synaptic transmission correlates of general mental ability

“…are within a similar range to those reported previously (Ryushi, Fukunaga, Yuasa, & Nakajima, 1990). In comparison with the mean total reflex time of 89.9 ms, the mean conscious response time of 175.1 ms was significantly slower (t = 18.430, df = 68, P < .001) with no overlap between distributions.…”

Surface electromyography reveals males have a slower patellar reflex than females

“…Whereas in the other study (Ryushi et al, 1990) given that they used a more limited height range (16 cm) of subjects than we employed: 24 cm, where our more expansive height range would be expected to increase the likelihood for detection of stature-dependent effects. One possible reason for both the larger and stature dependent latency reported by Ryushi et al (1990) is that their sample population was (presumably) exclusively Japanese in origin, whereas ours was entirely Caucasian. This effect of ethnicity is supported by the similarity of our male latency to that of Viitasalo and Komi (1981) who, like us, also sampled from a predominantly Caucasian (in their case Finnish) population.…”

Summation of elementary phonomyograms during isometric twitches in humans

“…It has been shown that slow motor units are stier than fast motor units, in rats (Goubel and Marini 1987) and in humans (Ryushi et al 1990). It is likely that the recruitment of weaker slow motor units, probably emitting lower amplitude elementary PMG, for the highest stimulation intensities is compensated for by a greater rate of increase of stiness.…”

“…That would largely explain the latency decrease with recruitment documented here. Because the slowest motor units have been suggested to have a higher passive stiness (Ryushi et al 1990), muscle tension generated by an increasing number of recruited slow units would be better transmitted through a stier muscle medium and tendon. The decrease of PMG and force delays accompanying recruitment would suggest that they have a common origin, the stretching of the series elastic element (from sarcomere to ®nger) adding a constant delay.…”