LINEAR AND ANGULAR MOMENTUM OF THE UPPER BODY IN TENNIS FOREHANDS

Linear momentum and angular momentum are said to be the two sources of power in the tennis forehand and they “should act together in a coordinated manner” (Groppel, 1992). However, the relationship between them has not been investigated. Thus, the purposes of this study were to determine linear and angular momentum of the upper body in tennis forehands and to investigate their coordination

PHYSIOLOGICALLY REASONABLE ‘TORQUE REVERSAL’ CAUSED IN COMPUTERSIMULATED PLANAR BALL THROWING DOES NOT INCREASE BALL SPEED AT RELEASE

INTRODUCTION: Herring and Chapman (1992) reported that some torque reversals caused by the agonist deactivation and the antagonist activation at the proximal joints of a planar three link segment model for ball throwing with the upper extremity increased ball speed at ball release. The paper has often been referred as the study showing possible positive roles of antagonisms for planar motions (Sorensen et al. 1996; Do”rge et al., 1999) in spite of its unrealistically rapid torque reversal for human movements. The purpose of this study was to investigate influences of the speeds of the deactivation and activation on the ball speed in computer-simulated ball throwing using a model similar to that used by Herring and Chapman (1992)

KINEMATICS OF TABLE TENNIS TOPSPIN FOREHANDS: EFFECTS OF PERFORMANCE LEVEL AND BALL SPIN

INTRODUCTION: The topspin forehand in table tennis is an effective offensive shot especially against backspin balls. It would be interesting for coaches and players to compare the kinematics of the stroke between different performance level players and between different ball spins. The purpose of this study was to clarify whether performance level and ball spin affect the kinematics of the table tennis topspin forehand

BIOMECANICS OF THE LOWER LIMBS IN RELRVÉ EN POINTÉ OF CLASSIC BALLET

INTRODUCTION: Relevé en pointé of classic ballet is a technique of standing on tiptoe with hard ballet shoes (Fig.1). Foot and ankle injuries caused by the motion have troubled dancers (Keryl, 2006). Though mechanics of the ankle joint have been investigated, lower limb mechanics have not been analyzed yet (Lin et al., 2005). In addition, muscle activities of the lower limbs have not been focused on. The purpose of this study was to investigate mechanics of the hip and knee joints besides the ankle joint in relevé en pointé

STRATEGY OF BALANCE CONTROL DURING PIRUETTÉ IN CLASSICAL BALLET

The purpose of this study was to investigate how ballet dancers control their balance on one leg during pirouetté in classical ballet. The hypothesis was that the classical ballet dancer balances letting the COP locate under the centre of mass (COM) of the whole body by translating the supporting leg. Piruettés by four Russian and one Japanese male ballet dancers were captured. COM, COP and supporting foot kinematics were analysed. The dancers’ COPs move after the COMs during the first half of one revolution. Then the COP began to stop near the COM and dancers’ body axes became more straight during latter half of one revolution. Most dancers translate the COP under the COM, controlling the COP locations in the supporting foot

MOMENTA OF BODY SEGMENTS CONVERTED INTO IMPACT FORCE OF A REAR HAND STRAIGHT PUNCH INTO AN UNFIXED TARGET

INTRODUCTION: When top-class martial artists such as champion kickboxers threw a rear hand straight punch with maximum effort into a target fixed on a wall, the contribution of the momentum of the throwing limb to an impact force or an impulse to the target was about 60% (Yoshihuku,1987). Yoshihuku (1995) suggested that the contribution of the momenta of the other body segments reduced when the punch was thrown into an unfixed target. The purpose of this paper was to clarify the contribution of the momentum of the throwing limb to the impulse when the punch was thrown into an unfixed target similar to the human head

Report on the geological, geomorphological and geodetic field party in the Sør Rondane Mountains, 1986 (JARE-27)

The 27th Japanese Antarctic Research Expedition (JARE-27) carried out the geological, geomorphological and geodetic field work in the central part of the Sør Rondane Mountains for 33 days from January 5 to February 6,1986. The field work was conducted by two parties with four persons each in order to investigate the vast area. They carried out expected investigations on spite of meeting with many crevasses. They used four snow vehicles and six snowmobiles. The snowmobiles were very useful to the field work in the area. This report gives detailed of operation including logistics, a summary of the field work, and information on the weather and the surface condition of snow and ice observed in this period