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. However, joint coordination with a change in throwing speed has not been studied. Here, we show the effects of changes in throwing speed on joint coordination during accurate overhead throwing. Participants were seated on a low chair with their trunk fixed and threw a baseball aimed at a target under 2 different speed conditions (slow and fast). In the slow condition, the elbow flexion/extension angle coordinated with other joint angles and angular velocities to reduce the variability of the vertical hand velocity. In the fast condition, the shoulder internal/external rotation angle and the shoulder horizontal flexion/extension angular velocity coordinated with other joint angles and angular velocities to reduce the variability of the vertical hand velocity. These results showed that joint coordination differed with changes in throwing speed, indicating that joint coordination is not always fixed, but may differ depending on the task constraints, such as throwing speed.

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 (Ehoriz and Evert) 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. We determined the components of the Ehoriz and Evert changes due to each segment movement. Elevation of the pelvic free-leg side increased Evert (0.53±0.16 J/kg, 9±3% of the total Evert change). Pelvic axial rotation decreased Ehoriz, while pelvic elevation did not affect it (0.01±0.02 J/kg, no significant difference from zero). In contrast, forward rotations of the stance-leg shank and thigh decreased Ehoriz while simultaneously increasing Evert. The results showed that pelvic elevation increased the vertical CoM velocity without causing a loss in horizontal velocity, although the lower-limb segments' effects on the vertical and horizontal velocities exhibited a trade-off, as previously speculated. RSLJs for distance have been frequently assumed as sagittal movements. However, our findings highlight the importance of three-dimensional pelvic movement, particularly in the frontal plane, for controlling both the vertical and horizontal velocities.Highlightsl We show the effect of each segment rotation on the horizontal and vertical kinetic energies (Ehoriz and Evert) of the centre of mass during the take-off phase of a running single-leg jump for distance.l Elevation of the pelvic free-leg side increased Evert but did not decrease Ehoriz, while the forward rotations of the stance-leg thigh and shank decreased Ehoriz, while simultaneously increasing Evert.l We highlight the importance of pelvic movement in the frontal plane for controlling both the vertical and horizontal velocities with single-leg stance.

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. We calculated the joint power exerted on each segment and the contributions from segment rotations to the normalised average horizontal and vertical external powers (P^horiz¯ and P^vert¯) during the sprint start by 12 male sprinters. Over half P^horiz¯ (55 ± 6%) is due to the front thigh rotation (0.30 ± 0.04), on which the hip and knee exert positive power. Pelvic rotation does not contribute to P^horiz¯ (0.00 ± 0.01). This highlights the importance of the hip-extensors strength and the need for it accompanied by the lumbar-extensors strength cancelling out the hip-extensors action on the pelvis and promoting hip-extensor-induced thigh rotation. The front thigh rotation decreases P^vert¯ (-0.08 ± 0.02). P^vert¯ is primarily induced by rotations of the thorax (0.04 ± 0.01), lumbar region (0.06 ± 0.02), and pelvis (0.04 ± 0.01). Rotations of the lower-limb segments did not contribute to upward propulsion. Therefore, the front thigh induces downward movement, which is counterbalanced by the trunk segments. We bridge the gap in the current understanding from joint power to P^horiz¯. We present a case involving segments on which positive joint powers are exerted similarly but play different roles: forward or upward propulsion, thereby providing insights into directional control mechanisms in explosive initiation of motion. HIGHLIGHTSWe examined the contributions of segment rotations to the normalised average horizontal and vertical external powers (P^horiz¯, P^vert¯): the sprint start performance and the parameter to assess upward propulsion.Over half the total P^horiz¯ (55 ± 6%) is due to the front thigh rotation, while the front thigh rotation decreases P^vert¯, which was counterbalanced by rotations of the thorax, lumbar region, and pelvis.We bridge the gap in the current understanding from joint power to P^horiz¯ and further present a case involving segments on which positive joint powers are exerted but play different roles: forward or upward propulsion.

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 < .05), indicating that wrist torque and work contributed to the adjustment of ball velocity. Peak MP joint torque also increased with ball velocity (p < .05), although the work of the MP joint remained relatively constant. We conclude that MP joint torque and work contribute to the achievement of stable ball release rather than adjusting ball velocity.

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. To quantify the coordination, the solution manifold and tolerance, noise, and covariation analysis were used for the ball-level redundancy, while uncontrolled manifold analysis and the covariation by randomization method were used for the body-level redundancy. The ball-level analysis revealed that the covariation and noise components were related to the performance, and that the noise component showed a larger contribution to performance than the covariation component, indicating that the reproducibility of the release parameters has a larger room for improvement than coordination. The coordination of release parameters was not significantly different between the FB and NF conditions, indicating that the effect of performance feedback on coordination is unclear. The body-level analysis revealed that interjoint coordination reduced the variability of the longitudinal positions of the hand and fingertip, showing that interjoint coordination improves the reproducibility of the ball-release position, especially in the direction that strongly affects the motor performance. In conclusion, interjoint coordination improved the reproducibility of ball-release parameters, which enhanced motor performance in basketball free-throw shooting.

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. The peak torque and work of finger adduction during the curveball was significantly larger than that during the fastball. During the fastball pitch, the maximal correlation coefficient between the wrist flexion torque and finger flexion torque was very high (r = 0.94 ± 0.05). The reasons for this result are twofold: (a) the extrinsic finger muscles cross the wrist (biarticular muscle) and (b) the wrist flexion torque during the fastball pitch acts in the direction of acceleration of the ball. During the curveball pitch, we found two typical types of wrist and finger torque control. Furthermore, the two pitchers exerted large wrist extension and radial torque, and finger adduction torque. Although the other six pitchers hardly exerted these torques, they exerted wrist flexion torque predominantly. It was considered that the six pitchers selected wrist flexion torque as the control for the fastball and curveball pitch to confuse the batter.

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. Here, we show that the curved RSLJ (C-RSLJ) is more suitable than the straight RSLJ (S-RSLJ) for CoM height generation. METHODS: We collected data using motion capture from 13 male high jumpers (personal best, 2.02-2.31 m) that performed C-RSLJ and S-RSLJ. We then compared the energy generation contributing to CoM height (Evert) in each approach. RESULTS: All participants attained greater CoM height in C-RSLJ than in S-RSLJ (difference, 0.055 ± 0.024 m). Three-dimensional joint kinematics and kinetics were similar between both approaches, except for the ankle plantar-flexion torque, which was smaller in C-RSLJ. The sum of positive work was comparable between the approaches, whereas the sum of negative work in C-RSLJ was significantly smaller than in S-RSLJ. The shank forward rotation induced a larger difference in Evert generation between C-RSLJ and S-RSLJ (0.80 ± 0.36 J·kg-1) than any other segment (≤0.36 J·kg-1). CONCLUSIONS: Compared with a straight approach, a curved approach induces greater CoM height without increasing joint kinetic exertions during takeoff. The curved approach changes the initial condition of the takeoff and promotes the transformation of horizontal kinetic energy into Evert. This study provides novel practical perspectives for high jumpers and highlights the importance of segment biomechanics in human motor performance.

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. We first introduced the distinction between explanations from the perspective of causes and explanations from the perspective of purposes as a mode of explaining events, and pointed out the importance of explanations from the perspective of purposes. We next argued that by taking the perspective of whether a given movement technique leads to a desired outcome in comparison to other movement techniques, we can expect to interpret what a given movement technique is for based on objectively observable information rather than the subjective intentions of the athlete. In addition, we discussed how the criterion movement patterns should be defined when assessing the fitness for purpose of a given movement technique in terms of its consequences. In this regard, our argument is that it is necessary to take into account that the exact same movement pattern cannot be performed every time, even for the same motor task, and that there are multiple options for how to define the set of possible movement patterns that can be performed. Our discussion reveals the peculiarity of grasping the meaning of movement techniques, and therefore suggests that there is a substantial need for motion analysis researchers to deepen their conceptual analysis to understand the nature of this issue.

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. We analysed the motion and ground reaction force of 10 males during the stance phase in 90° sidestep cutting with maximal efforts and determined the segmental components to the changes in the mediolateral-kinetic (EML), anteroposterior-kinetic (EAP), and superoinferior-kinetic plus gravitational-potential energies (ESI). The medial velocity and EML increased from the beginning to the end of the stance. The stance-leg shank rotation increased EML and decreased EAP(early stance: 0.54 ± 0.17 and -1.49 ± 0.59 J/kg, late stance: 0.25 ± 0.14 and - 0.40 ± 0.17 J/kg), even while the knee and ankle work outflowed energy from the shank. The shank rotation induced over half the total increase in EML during the early stance (58 ± 7%). The stance-leg thigh rotation increased EML and decreased EAP (early stance: 0.28 ± 0.12 and -0.26 ± 0.15 J/kg, late stance: 1.43 ± 0.26 and -0.47 ± 0.13 J/kg). We added the transformation from EAP to EML by the shank and thigh rotations in the transverse plane to the sideward propulsion mechanisms, similar to the transformation from EAP into ESI in running single-leg jumps in a previous study. Coupled with previous studies, we prove the commonality in propulsion mechanisms across non-forward locomotion modes with different objective directions, which bridges the knowledge between unsteady locomotion modes.

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. Therefore, we aimed to propose a method for identifying joint coordination. Subsequently, we examined which joint movements were coordinated using accurate overhead throwing, which required reduction in vertical hand velocity variability. Fourteen baseball players participated by attempting throwing using a motion capture system. The index of coordination for each joint movement and the effect of deviation of one joint movement on vertical hand velocity were quantified. Our results showed that the shoulder internal/external rotation angle (θ1-IE) and the other joint movements or the shoulder horizontal flexion/extension angular velocity (ω1-FE) and the other joint movements were coordinated. These results could be explained by the fact that the effects of the deviation of the shoulder internal rotation angle (θ1-I) and shoulder horizontal flexion angular velocity (ω1-F) on vertical hand velocity were larger than those of the other joint movements. This meant that it was necessary to cancel the deviations of θ1-IE and ω1-FE by the other joint movements. These findings indicate that the method proposed in this study enables the identification of which joint movements are coordinated in multiple degrees of freedom.

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. The differences in corresponding joint positions, estimated from the two different methods throughout the analysis, were presented as a mean absolute error (MAE). The results demonstrated that, qualitatively, 3D pose estimation using markerless motion capture could correctly reproduce the movements of participants. Quantitatively, of all the mean absolute errors calculated, approximately 47% were <20 mm, and 80% were <30 mm. However, 10% were >40 mm. The primary reason for mean absolute errors exceeding 40 mm was that OpenPose failed to track the participant's pose in 2D images owing to failures, such as recognition of an object as a human body segment or replacing one segment with another depending on the image of each frame. In conclusion, this study demonstrates that, if an algorithm that corrects all apparently wrong tracking can be incorporated into the system, OpenPose-based markerless motion capture can be used for human movement science with an accuracy of 30 mm or less.

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 (Evert) in RSLJ. We determined the component of increase in Evert due to each segment movement in RSLJs by 13 male high-jumpers. The stance-leg shank forward rotation (rotation opposite to the actions of the knee extensors and ankle plantar flexors on the shank), increased Evert (0.76 ± 0.70 J/kg). Evert due to the stance-leg thigh forward rotation (4.39 ± 0.57 J/kg) was substantially larger than the inflowing energy into the thigh (difference: 2.36 ± 0.42 J/kg). These results suggest that the forward rotations of the shank and thigh transformed horizontal kinetic energy (Ehori) to Evert.Evert was increased by the elevation of the free-leg side of the pelvis (0.53 ± 0.22 J/kg) and rotation of free-leg thigh (1.52 ± 0.26 J/kg). The non-extension movements contributed to over half (59 ± 6%) the increase in Evert during the take-off phase. Human-specific morphologies are essential for the contributions of non-extension movements; fully extensible knee joints and relatively longer legs with respect to body mass for the transformation from Ehori to Evert by shank and thigh rotations, and a wide and short pelvis for increasing Evert by pelvic elevation. This study provides quantifiable evidence to indicate how substantially non-extension movements contribute to higher RSLJ.

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. The center of pressure (COP) trajectories and related muscle (soleus, tibialis anterior, and gluteus medius of both lower limbs) activities during the APA of step initiation tasks in nine different directions were analyzed in six healthy young males. Posterior shifts of COP during APA decreased as the direction became more lateral (0° to 90°). For posterior step initiations, COP moved anteriorly from the initial position to accelerate the center of mass of the whole body (COM) backward. Lateral shifts of COP toward the stepping foot during APA decreased as the stepping direction became more lateral (from 0° to 45° and from 180° to 113°) while it plateaued to about zero in the direction from 45° to 113°. Both anteroposterior and lateral displacements of COP in APA were nonlinearly modulated to each direction, but they were linearly related to the anteroposterior and mediolateral component of the velocities of COM at the take-off of the stance foot. Thus, the scaling of APA, reflected in the anteroposterior and lateral displacements of COP and the temporal sequence of selected muscle activities, was based on the anteroposterior and mediolateral components of the take-off velocity of COM that ultimately controls the direction of steps.

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. We analysed the kinematic and kinetic data of 90° sidestep cutting with maximal effort by 10 physically active men. The thorax rotated toward the objective direction prior to the pelvis, resulting in the trunk axial rotation with the peak angle of 21.0 ± 6.0°. Lumbosacral axial torque was exerted toward the objective direction during the early stance phase, and it was then exerted inversely during the late stance and flight phases, which was consistent with the increase/decrease in the trunk axial rotation velocity. In the early stance phase, the absolute integrated component of the lumbosacral axial torque for pelvic rotation (0.074 ± 0.033 Nms/kg) was significantly larger than any other integrated component. In the late stance and flight phases, the lumbosacral axial torque mainly rotated the pelvis. The results indicate that the axial torque is exerted to actively induce the trunk axial rotation rather than minimise the trunk movement, suggesting that the trunk control concept probably should include not only stabilising but also actively moving the trunk.

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. We collected the kinematic and ground reaction force data during single-leg and double-leg squat jumps from ten male participants using motion capture systems and force platforms. We determined the components of the mechanical energy directly contributing to the height of the centre of mass due to segment movement. The energy due to rotations of the foot, shank, thigh, and pelvis were significantly greater in single-leg squat jumps than in double-leg squat jumps. The magnitudes of the difference in energy between single-leg and double-leg squat jumps due to the pelvis (0.54 ± 0.22 J/kg) was significantly larger than that due to any other segment (<0.30 J/kg). This indicates that pelvic elevation in single-leg jump is a critical factor causing bilateral deficit in jumping, and that humans generate the jumping height with a single leg not just by an explosive leg-extension but also by synchronous free-leg side elevation of the pelvis. The findings suggest that this pelvic mechanism is a factor characterising human single-leg jumps.

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, 10.78 ± 0.19 s [range, 10.43-11.01 s]) were captured using a motion capture system and force platform. The three-dimensional lumbo-pelvic-hip kinetics were calculated. The peak lumbosacral extension torque (3.64 ± 0.39 Nm/kg) was significantly larger than any other lower-limb and lumbosacral torques (<3.0 Nm/kg). It was suggested that large lumbopelvic extension torques are needed during the block start to anchor the pelvis by cancelling out both hip extension torques acting on the pelvis, leading to hip extensor-induced thigh sagittal rotations rather than pelvic posterior tilt. During the double-stance phase, the lumbosacral extensors generated mechanical energy (0.35 ± 0.16 J/kg, 14 ± 4% of the sum of lumbosacral and lower-limb net joint work). During the single-stance phase, the sum of the net mechanical work by lumbosacral lateral flexors and front hip abductors was 0.35 ± 0.14 J/kg, which comprised 9 ± 3% of the sum of the net joint work. The results lead to the speculation of the importance of strengthening not only the leg extensors, but also the lumbopelvic extensors, lateral flexors, and hip abductors for block starts. Further training studies to verify this speculation will improve training strategies for the track and field block start performance.

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. The solution manifold consisting of ball parameters at release was calculated and the optimal strategy was simulated by considering ball parameter variability; this result was compared with the actual data. Our results showed that participants selected the solution of near-minimum release speed. The deviation of the measured release angle from the minimum-speed angle was close to zero (2.8 ± 3.1∘). However, an increase in speed-dependent noise did not have a significant influence on the ball landing position through simulation. Additionally, the effect of release angle error on the ball landing position was minimum when using the minimum speed strategy. Therefore, the players minimize the release speed to minimize the effect of the release error on performance, instead of minimizing the speed-dependent noise itself. In other words, the strategy is "near-minimum-speed strategy" as well as "minimum-error-propagation strategy". These findings will be important for understanding how sports experts deal with intrinsic noise to improve performance.

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

Abstract 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. They threw a baseball as fast and precisely as possible, and data from three strikes were used. A motion capture system consisting of 13 cameras and two force platforms was used to collect the data and calculate joint torques of the thoracic and the lumbar joint. The joint torque of the thoracic and the lumbar joint were calculated using a top-down and a bottom-up approach, respectively. Then, the mechanical energy generation and transfer by the torsional torques were quantified. The mechanical energy generation exerted by the torsional torques of the thoracic and lumbar joints were 0.03 ± 0.03 and 0.15 ± 0.04 J kg-1 m-1, respectively. The mechanical energy transfer exerted by the torsional torques of the thoracic and lumbar joints were 0.72 ± 0.19 and 0.88 ± 0.24 J kg-1 m-1, respectively. These results indicated that torsional torques transferred a substantial amount of mechanical energy from the pelvis to the upper torso. Furthermore, the findings indicate that the mechanical energy transfer exerted by the torsional torques was a major contributor to the upper torso rotation.

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. Our results showed that the joint work was not significantly different for short- and mid-condition shots; however, the amount of energy transferred from the torso to the shooting arm by the shoulder joint force increased significantly for the mid-condition shots ([Formula: see text] as opposed to [Formula: see text] J/kg, [Formula: see text]), whereas between the mid- and long-conditions, it was found that the joint work in the lower limbs increased significantly ([Formula: see text] as opposed to [Formula: see text] J/kg, [Formula: see text]). These results suggest that sufficient energy transfer from the lower limbs to the shoot arms is important to keep the motions of the shooting arms approximately constant when shooting from various distances.

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. We calculated the three-dimensional lumbosacral kinetics of 10 male sprinters during steady-state running on a temporary indoor running track at five target velocities: 3.0 (3.20 ±â€¯0.16), 4.5 (4.38 ±â€¯0.18), 6.0 (5.69 ±â€¯0.47), 7.5 (7.30 ±â€¯0.41), and maximal sprinting (9.27 ±â€¯0.36 m/s). The lumbosacral axial rotation torque increased more markedly (from 0.37 ±â€¯0.06 to 1.99 ±â€¯0.46 Nm/kg) than the extension and lateral flexion torques. The increase in the axial rotation torque was larger above 7.30 m/s. Conversely, the extension and lateral flexion torques plateaued when running velocity increased above 7.30 m/s. Similar results were observed for mechanical work. The results indicate that faster running required larger lumbosacral axial rotation torque. Conversely, the extension and lateral flexion torques were relatively invariant to running velocity above 7 m/s, implying that faster running below 7 m/s might increase the biomechanical loads causing excessive pelvic posterior tilt and excessive pelvic drop which has the potential to cause pain/injury related to lumbopelvic extensors and lateral flexors, whereas these biomechanical loads might not relate with running velocity above 7 m/s.