Poor Joint Work in the Lower Limbs during a Tennis Forehand Groundstroke after a Cross-Over Step Inhibits an Increase in the Racket Speed.

A forward run-up and stepping are used to accelerate hitting tools or throwing objects in sports. This study aimed to investigate the effect of a forward cross-over step on the speed of a hitting tool by analyzing the joint work and mechanical energy of the whole body and the hitting tool using inverse dynamics. Thirteen advanced tennis players performed forehand groundstrokes at maximum effort with and without a forward cross-over step.

Joint Coordination With a Change in Task Constraint During Accurate Overhead Throwing.

In sports situations, players may be required to throw at different speeds. The question of how skilled players throw the ball accurately to the desired location under different speed conditions is of interest to biomechanics researchers. Previous research suggested that throwers use different types of joint coordination.

Mechanical power flow from trunk and lower limb joint power to external horizontal power in the track and field block start.

Sprint start performance is measured as the horizontal external power, the time-average rate of horizontal kinetic energy generation. Although joint powers have been examined, not all segment rotations on which positive powers are exerted necessarily contribute to forward propulsion; details regarding horizontal power remain unclear. Here we show the contributions of segment rotations to the forward and upward propulsion.

Pelvic elevation induces vertical kinetic energy without losing horizontal energy during running single-leg jump for distance.

In a running single-leg jump (RSLJ) for distance, the generation of vertical velocity without loss of horizontal velocity during the take-off phase is ideal, but difficult; however, we hypothesized that the pelvic rotation in the frontal plane achieved it. Here we show the effect of each segment rotation on the horizontal and vertical kinetic energies ( and ) of the centre of mass (CoM) during the take-off phase of an RSLJ for distance. We collected kinematic and ground-reaction-force data during RSLJs for distance by nine male long jumpers, involving an approximately 20-m approach in an outdoor field.

Kinetic Analysis of the Fingers Under Different Ball Velocities During Overarm Throwing.

The purpose of this study is to examine changes in the kinetic parameters of the fingers caused by differences in ball velocity during overarm throwing. Six baseball players participated in the study, and the kinetics of the wrist and metacarpophalangeal (MP) joint were calculated using an inverse dynamics method. The results of Tukey's multiple comparison tests showed that the torque and work of the wrist increased with increasing ball velocity (p < .

Utilizing hierarchical redundancy for accurate throwing movement.

Understanding how athletes reduce motor variability in redundant tasks contributes to improving sports performance and elucidating human motor control mechanisms. This study aimed to clarify how experienced basketball players use two hierarchical redundancies, ball-level and body-level, for accurate free-throw shooting as no study has simultaneously examined how these hierarchical redundancies are used. Experienced basketball players (intermediate-level and top-level) participated in a free-throw shooting experiment using a motion capture system under two conditions: with feedback (FB) and no-feedback (NF) conditions.

Explaining "What for" in Motion Analysis Research: A Proposal for a Counterfactual Framework That Is Slightly Different From the Theory of Causation.

In motion analysis research, the methodology for estimating the physical processes of human movement is highly developed, but the methodology for interpreting such data is relatively undeveloped. One of the aims of this paper is to demonstrate the importance of developing a conceptual basis for interpreting data about the physical processes of body movement. In this conceptual study, one topic was discussed as a central question: what it means to answer the question what a certain movement technique is aimed for.

Acquisition of mechanical energy directly contributing to sideward propulsion in sidestep cutting manoeuvre.

Humans seldom perform steady-state forward locomotion and often change locomotive direction through non-forward propulsion. Such manoeuvrability is essential for humans; however, unsteady-locomotion mechanics are understood less than steady-state locomotion because of the difficulty in research on unsteady locomotion with a wide range of variations. Here we show the body sideward propulsion mechanism in a sidestep cutting manoeuvre.

Curved Approach in High Jump Induces Greater Jumping Height without Greater Joint Kinetic Exertions than Straight Approach.

Purpose: The most height-specific jumping mode, the athletic high jump, is characterized as a running single-leg jump (RSLJ) from a curved approach. The main advantage of a curved approach is believed to be facilitation of bar clearance. However, the effect of a curved approach on center-of-mass (CoM) height generation has not been clarified.

Identifying coordination between joint movements during a throwing task with multiple degrees of freedom.

It is known that coordination between joint movements is crucial for the achievement of motor tasks and has been studied extensively. Especially, in sports biomechanics, researchers are interested in determining which joint movements are coordinated to achieve a motor task. However, this issue cannot be easily addressed with the methods employed in previous studies.

Evaluation of 3D Markerless Motion Capture Accuracy Using OpenPose With Multiple Video Cameras.

There is a need within human movement sciences for a markerless motion capture system, which is easy to use and sufficiently accurate to evaluate motor performance. This study aims to develop a 3D markerless motion capture technique, using OpenPose with multiple synchronized video cameras, and examine its accuracy in comparison with optical marker-based motion capture. Participants performed three motor tasks (walking, countermovement jumping, and ball throwing), and these movements measured using both marker-based optical motion capture and OpenPose-based markerless motion capture.

Kinetic analysis of the wrist and fingers during fastball and curveball pitches.

This study had two objectives: (a) revealing kinetic parameter differences at the fingers during a fastball and curveball, and (b) examining timing control between the wrist and finger torques. The participants were eight baseball pitchers. The kinetics of the wrist and fingers were calculated using an inverse dynamics method.

Non-extension movements inducing over half the mechanical energy directly contributing to jumping height in human running single-leg jump.

The running single-leg jump (RSLJ), including certain non-extension movements (movements not induced by lower-limb extension works), is the highest jumping mode in humans. Here, we show the substantial contributions of non-extension movements, in generating mechanical energy directly contributing to the jumping height (E) in RSLJ. We determined the component of increase in E due to each segment movement in RSLJs by 13 male high-jumpers.

Lumbar axial torque actively induces trunk axial rotation during sidestep cutting manoeuvre: Insight to expand the trunk control concept.

Core stability is widely recognised as 'the body's ability to maintain or resume an equilibrium position of the trunk after perturbation'. As such, large excursions of the trunk during controlled activities are believed to be the result of poor trunk control. Here, we show that the axial torque actively induces the trunk axial rotation (the thoracic rotation relative to the pelvis) rather than minimise the axial rotation during sidestep cutting.

Directional Control Mechanisms in Multidirectional Step Initiating Tasks.

Typical anticipatory postural adjustments (APAs) in forward gait or step initiation tasks to prepare for possible disturbances caused by prime voluntary movements and to accelerate the body forward have been previously reported. However, it is not clear how wide the variations in step directions are differentiated and controlled in non-forward step initiation tasks during the APA phase. The main goal of this study is to explain the directional control mechanisms by investigating the APA of step initiation tasks in forward, diagonal, lateral, and posterior directions.

Basketball players minimize the effect of motor noise by using near-minimum release speed in free-throw shooting.

The aim of this study was to clarify the strategy used by basketball players during free-throw shooting to improve performance in the presence of motor noise. Two possible hypotheses were examined: the players minimize the release speed to decrease signal-dependent noise or the players maximize the shot success probability by accounting for their variability. Eight collegiate players and one professional player participated in this study by attempting shots from the free-throw line using a motion capture system.

Free-leg side elevation of pelvis in single-leg jump is a substantial advantage over double-leg jump for jumping height generation.

In single-leg jumps, humans achieve more than half the jumping height that they can reach for double-leg jumps. Although this bilateral deficit in jumping has been believed to be due to the reduction of leg extensor force/work exertions, we hypothesised that the three-dimensional biomechanical differences between double-leg and single-leg jumps also influence the bilateral deficit in jumping. Here, we show the substantial effect of the elevation of the pelvic free-leg side in single-leg squat jumps on the bilateral deficit in jumping in addition to extensor force reduction.

Three-dimensional kinetic function of the lumbo-pelvic-hip complex during block start.

Previous studies on joint kinetics during track and field block starts have been limited to lower-limb sagittal kinetics; however, we hypothesised that lumbopelvic extensors, lateral flexors, and hip abductors also act as substantial energy generators. The present study aimed to examine the three-dimensional lumbo-pelvic-hip kinetics to better understand the generation of mechanical energy during a block start. 3D kinematic and force data during block starts of 10 m maximal sprinting in 12 male sprinters (personal best in a 100 m sprint, 10.

A biomechanical study of the relationship between running velocity and three-dimensional lumbosacral kinetics.

Faster running is not performed with proportional increase in all joint torque/work exertions. Although previous studies have investigated lumbopelvic kinetics for a single velocity, it is unclear whether each lumbopelvic torque should increase for faster running. We examined the relationship between running velocity and lumbopelvic kinetics.

Mechanical properties of upper torso rotation from the viewpoint of energetics during baseball pitching.

This study aims to examine if upper torso rotation is caused mainly by pelvis rotation during baseball pitching from the viewpoint of energetics. Twelve right-handed males participated in this study. Five were and seven had been collegiate baseball pitchers, and all used an overarm style.

The sidestep cutting manoeuvre requires exertion of lumbosacral lateral flexion torque to avoid excessive pelvic obliquity.

During sidestep cutting, the pelvis is supported only on one side; this affects the athlete's posture. This study investigated the mechanism to avoid excessive pelvic obliquity during sidestep cutting. Ten physically active men performed sidestep cutting with maximal effort, and we captured the kinematics and kinetics with force platforms and an eight-camera motion capture system.

Directionally compensated mechanical work provided by the shoulder leads to similar racket velocities during open and square stance forehand groundstrokes in tennis.

The differences between the racket-arm acceleration mechanisms during open and square stance forehand groundstrokes in tennis were examined by quantifying the mechanical work done on the racket arm. We studied 13 advanced tennis players as they performed these strokes at maximum effort and calculated the work using inverse dynamics. The racket head speed was similar between the open and square stances.

Hip Abductors and Lumbar Lateral Flexors act as Energy Generators in Running Single-leg Jumps.

In humans, hip abductor and lumbar lateral flexor muscles are well-developed as side-to-side lumbopelvic stabilizers. We hypothesized that the hip abductors and lumbar lateral flexors act as energy generators during a running single-leg jump, although they are generally recognized as stabilizers. We collected kinematics and ground reaction force data in running single-leg jumps by 13 male high jumpers and calculated three-dimensional kinetic variables.

The effect of increased shooting distance on energy flow in basketball jump shot.

The aim of this study is to clarify the effect of shooting distance on energy flow in basketball jump shot. Ten male right-handed basketball players participated in this study, and three successful shots at three different distances (short condition, equating to a free-throw; long condition, equating to a three-point shot; and mid condition, equating to the mid-point of the short- and long-condition shots) were recorded using a motion capture system and force platforms. Kinetic variables of joints during shooting were analysed using inverse dynamics method.

Kinetic Analysis of Fingers During Aimed Throwing.

This study had two objectives: (a) revealing the difference in finger segments between the conventional and finger models during aimed throwing and (b) examining the central nervous system's timing control between the wrist torque and finger torque. Participants were seven baseball players. Finger kinetics was calculated by an inverse dynamics method.