「うつくし」と「らうたし」の意味の変化について

Abstract

Three-dimensional, high-speed cinematography was used to compare backspin backhand techniques of high performance players hitting low (5.4 cm below hip height) and high (41.6 cm above hip height) bouncing balls using their preferred method of holding the racket (eastern backhand or continental grip: hand generally on top of the handle) and non-preferred ('behind the handle') grip. The Direct Linear Transformation method was used for three-dimensional space reconstruction from two-dimensional images recorded from laterally placed phase-locked cameras operating at 200 Hz. The only significant differences (P < 0.05) caused by the change in grip were that the ball was impacted further in front of the body when using the non-preferred grip, and a lower peak racket-shoulder speed was recorded for a high bouncing ball when using the non-preferred grip. Irrespective of the type of grip, the players significantly modified (P < 0.01) their technique to hit a high bouncing ball by adopting a more upright trunk, more rotated shoulder alignment (racket shoulder pointing more towards opponent), a larger front knee angle and a more abducted upper arm. Hitting a high ball was also characterized by a less inclined approach trajectory of the racket, a more vertical racket-face and a different speed profile for the segments of the upper limb and racket.