Studies focused on jumping performance in humans have so far investigated either its biological o... more Studies focused on jumping performance in humans have so far investigated either its biological or sociocultural significance, with very little attentions paid to the inseparable relations of these two aspects in daily life of people. Integrating both ethnographic and biomechanical methods, this research investigated the biosocial features of the jump performance of Maasai youth in its most well observed context, the wedding ceremony. Ethnographic data were used to explain the social status of participants, the physical movements and singing tempo of performers, and their interactions. Biomechanical methods were applied to assess the heights and frequencies of identified repetitive double-legged vertical jumps (n = 160, from 15 male youths). All youth performers followed a certain posture pattern, paying specific attention to their final landing. Large variations exist in their jumping heights [coefficient of variation (CV) = 0.237]; however, the frequency in jump repetitions were maintained with the least variations (CV = 0.084). Cheering interactions were confirmed, but with no significant difference in height between the cheered and non-cheered groups. These results indicate that the Maasai youths did not compete for jump height during local ceremonies. Rather, they emphasized the rhythmical retention of jumps, corresponding to other youth mates who were singing alongside. In the broader context of human behaviors, the analysis addresses the diverse meanings of motor performances in different daily contexts that reject the generalized sports regime of "higher/faster-the-better".
Background Early childhood is a transferring stage between the two accelerated growth periods (in... more Background Early childhood is a transferring stage between the two accelerated growth periods (infant and adolescent). Body dimensions are related to physical growth and development. The purpose of this study was to investigate physical growth in terms of anthropometry, muscle growth of the lower extremity, and functional development over early childhood. Methods A cross-sectional study was carried out on 29 preschool children (PS: 3–5 years), 21 school children (SC: 6–8 years), and 22 adults (AD: 20–35 years). Lower extremity characteristics (segmental dimensions, muscle and adipose tissue thicknesses of the thigh and lower leg), and voluntary joint torque (knee and ankle) were measured. Correlations between parameters and group comparisons were performed. Results All the parameters except for body mass index (BMI) and subcutaneous adipose tissue thickness were correlated with age for PS and SC combined (r = 0.479–0.920, p < 0.01). Relative thigh and shank lengths to body height...
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-... more This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
In a running single-leg jump (RSLJ) for distance, the generation of vertical velocity without los... more 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.Highlights• 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.• 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.• We highlight the importance of pelvic movement in the frontal plane for controlling both the vertical and horizontal velocities with single-leg stance.
Human steady-state locomotion modes are symmetrical, leading to symmetric mechanical function of ... more Human steady-state locomotion modes are symmetrical, leading to symmetric mechanical function of human feet in general; however, track distance running in a counterclockwise direction exposes the runner’s feet to asymmetrical stress. This may induce asymmetrical adaptation in the runners’ foot arch functions, but this has not been experimentally tested. Here, we show that the plantar fascia (PF), a primary structure of the foot arch elasticity, is stiffer for the left than the right foot as a characteristic of runners, via a cross-sectional study on 10 track distance runners and 10 untrained individuals. Shear wave velocity (index of tissue stiffness: SWV) and thickness of PF and foot dimensions were compared between sides and groups. Runners showed higher PF SWV in their left (9.4 ± 1.0 m/s) than right (8.9 ± 0.9 m/s) feet, whereas untrained individuals showed no bilateral differences (8.5 ± 1.5 m/s and 8.6 ± 1.7 m/s, respectively). Additionally, runners showed higher left to right...
PurposeSprinters exhibit inhomogeneous muscularity corresponding to musculoskeletal demand for sp... more PurposeSprinters exhibit inhomogeneous muscularity corresponding to musculoskeletal demand for sprinting execution. An inhomogeneous morphology would affect the mass distribution, which in turn may affect the mechanical difficulty in moving from an inertia perspective; however, the morphological characteristics of sprinters from the inertia perspective have not been examined. Here we show no corresponding differences in the normalized mass and normalized moment of inertia between the sprinters and untrained non-sprinters.MethodsWe analyzed fat- and water-separated magnetic resonance images from the lower limbs of 11 male sprinters (100 m best time of 10.44–10.83 s) and 12 untrained non-sprinters. We calculated the inertial properties by identifying the tissue of each voxel and combining the literature values for each tissue density.ResultsThe lower-limb relative mass was significantly larger in sprinters (18.7 ± 0.7% body mass) than in non-sprinters (17.6 ± 0.6% body mass), while th...
The clarification of the problems to perform the clean in novice obtains several suggestions for ... more The clarification of the problems to perform the clean in novice obtains several suggestions for technical guidance. We aimed to identify the control of muscle coordination patterns and related kinetic problems during the clean. Five experienced participants (EXP) and five novices (NOV) performed the clean. The synchronous activation patterns among several muscles were extracted using a decomposition technique. The median number of patterns in NOV (2) was smaller than that of EXP (4). We specified the absent pattern, which was related to the activation of lower limb extensors at the termination of the scoop phase. This might lead to insufficient ankle plantarflexion torque or backward ground reaction forces for pulling the barbell. A practical implication is that a novice needs to pay attention to learning the appropriate activation timing of lower limb extensors for sufficient force exertion.
The approach lengths in running single-leg jumps (RSLJs) vary depending on various sports. We exa... more The approach lengths in running single-leg jumps (RSLJs) vary depending on various sports. We examined the effects of approach length on joint kinetics in RSLJ. We analysed RSLJs for height from the approaches of 1, 3, 5, and 7 steps by 10 male jumpers. The approach length did not have a main effect on hip extension torque (from 3.18±0.46 to 3.41±0.65 Nm/kg), while the hip abduction torque increased with increase in approach length (from 1.84±0.38 to 2.62±0.66 Nm/kg). The lumbosacral lateral flexors behaved similarly to the hip abductors. Results suggest that the greater frontal torques must be exerted from longer approaches whereas the greater hip extensors are important for RSLJs from shorter approaches. The findings provide the information for athletes what torque exertion ability should be trained with a priority depending on their approach lengths.
This study aimed to reveal the effect of segmental rotation on the generation of vertical velocit... more This study aimed to reveal the effect of segmental rotation on the generation of vertical velocity and loss of horizontal velocity during take-off of a long jump. 3D motion capture system and force plates were used to capture the long jumps by nine male athletes with an approach running distance of approximately 20 m. Forward rotations of the shank and thigh of the stance leg increased vertical energy (Evert) and decreased horizontal energy (Ehori); however, elevation of the free leg side of the pelvis increased Evert (0.53 ± 0.16 J/kg), although pelvic elevation did not decrease Ehori (0.01 ± 0.02 J/kg). It was revealed that although shank and thigh movements involved the loss of horizontal velocity, elevation of the free leg side of the pelvis generated vertical velocity without the loss of horizontal velocity. This study provides evidence for a new technical approach for a long jump.
Humans seldom perform steady-state forward locomotion and often change locomotive direction throu... more 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.
Core stability is widely recognised as 'the body's ability to maintain or resume an equilibrium p... more 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.
Medicine & Science in Sports & Exercise, 2021
PURPOSE The most height-specific jumping mode, the athletic high jump, is characterized as a runn... more 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. Yet, 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) than any other segment (≤ 0.36 J/kg). CONCLUSION Compared to a straight approach, a curved approach induces greater CoM height without increasing joint kinetic exertions during take-off. The curved approach changes the initial condition of the take-off and promotes transformation of horizontal kinetic energy into Evert. This study provides novel practical perspectives for high jumpers and highlights the importance of segment and joint biomechanics in human motor performance.
Previous studies on joint kinetics during track and field block starts have been limited to lower... more 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.
Free-leg side elevation of pelvis in single-leg jump is a substantial advantage over double-leg j... more Free-leg side elevation of pelvis in single-leg jump is a substantial advantage over double-leg jump for jumping height generation,
Studies focused on jumping performance in humans have so far investigated either its biological o... more Studies focused on jumping performance in humans have so far investigated either its biological or sociocultural significance, with very little attentions paid to the inseparable relations of these two aspects in daily life of people. Integrating both ethnographic and biomechanical methods, this research investigated the biosocial features of the jump performance of Maasai youth in its most well observed context, the wedding ceremony. Ethnographic data were used to explain the social status of participants, the physical movements and singing tempo of performers, and their interactions. Biomechanical methods were applied to assess the heights and frequencies of identified repetitive double-legged vertical jumps (n = 160, from 15 male youths). All youth performers followed a certain posture pattern, paying specific attention to their final landing. Large variations exist in their jumping heights [coefficient of variation (CV) = 0.237]; however, the frequency in jump repetitions were maintained with the least variations (CV = 0.084). Cheering interactions were confirmed, but with no significant difference in height between the cheered and non-cheered groups. These results indicate that the Maasai youths did not compete for jump height during local ceremonies. Rather, they emphasized the rhythmical retention of jumps, corresponding to other youth mates who were singing alongside. In the broader context of human behaviors, the analysis addresses the diverse meanings of motor performances in different daily contexts that reject the generalized sports regime of "higher/faster-the-better".
Background Early childhood is a transferring stage between the two accelerated growth periods (in... more Background Early childhood is a transferring stage between the two accelerated growth periods (infant and adolescent). Body dimensions are related to physical growth and development. The purpose of this study was to investigate physical growth in terms of anthropometry, muscle growth of the lower extremity, and functional development over early childhood. Methods A cross-sectional study was carried out on 29 preschool children (PS: 3–5 years), 21 school children (SC: 6–8 years), and 22 adults (AD: 20–35 years). Lower extremity characteristics (segmental dimensions, muscle and adipose tissue thicknesses of the thigh and lower leg), and voluntary joint torque (knee and ankle) were measured. Correlations between parameters and group comparisons were performed. Results All the parameters except for body mass index (BMI) and subcutaneous adipose tissue thickness were correlated with age for PS and SC combined (r = 0.479–0.920, p < 0.01). Relative thigh and shank lengths to body height...
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-... more This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
In a running single-leg jump (RSLJ) for distance, the generation of vertical velocity without los... more 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.Highlights• 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.• 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.• We highlight the importance of pelvic movement in the frontal plane for controlling both the vertical and horizontal velocities with single-leg stance.
Human steady-state locomotion modes are symmetrical, leading to symmetric mechanical function of ... more Human steady-state locomotion modes are symmetrical, leading to symmetric mechanical function of human feet in general; however, track distance running in a counterclockwise direction exposes the runner’s feet to asymmetrical stress. This may induce asymmetrical adaptation in the runners’ foot arch functions, but this has not been experimentally tested. Here, we show that the plantar fascia (PF), a primary structure of the foot arch elasticity, is stiffer for the left than the right foot as a characteristic of runners, via a cross-sectional study on 10 track distance runners and 10 untrained individuals. Shear wave velocity (index of tissue stiffness: SWV) and thickness of PF and foot dimensions were compared between sides and groups. Runners showed higher PF SWV in their left (9.4 ± 1.0 m/s) than right (8.9 ± 0.9 m/s) feet, whereas untrained individuals showed no bilateral differences (8.5 ± 1.5 m/s and 8.6 ± 1.7 m/s, respectively). Additionally, runners showed higher left to right...
PurposeSprinters exhibit inhomogeneous muscularity corresponding to musculoskeletal demand for sp... more PurposeSprinters exhibit inhomogeneous muscularity corresponding to musculoskeletal demand for sprinting execution. An inhomogeneous morphology would affect the mass distribution, which in turn may affect the mechanical difficulty in moving from an inertia perspective; however, the morphological characteristics of sprinters from the inertia perspective have not been examined. Here we show no corresponding differences in the normalized mass and normalized moment of inertia between the sprinters and untrained non-sprinters.MethodsWe analyzed fat- and water-separated magnetic resonance images from the lower limbs of 11 male sprinters (100 m best time of 10.44–10.83 s) and 12 untrained non-sprinters. We calculated the inertial properties by identifying the tissue of each voxel and combining the literature values for each tissue density.ResultsThe lower-limb relative mass was significantly larger in sprinters (18.7 ± 0.7% body mass) than in non-sprinters (17.6 ± 0.6% body mass), while th...
The clarification of the problems to perform the clean in novice obtains several suggestions for ... more The clarification of the problems to perform the clean in novice obtains several suggestions for technical guidance. We aimed to identify the control of muscle coordination patterns and related kinetic problems during the clean. Five experienced participants (EXP) and five novices (NOV) performed the clean. The synchronous activation patterns among several muscles were extracted using a decomposition technique. The median number of patterns in NOV (2) was smaller than that of EXP (4). We specified the absent pattern, which was related to the activation of lower limb extensors at the termination of the scoop phase. This might lead to insufficient ankle plantarflexion torque or backward ground reaction forces for pulling the barbell. A practical implication is that a novice needs to pay attention to learning the appropriate activation timing of lower limb extensors for sufficient force exertion.
The approach lengths in running single-leg jumps (RSLJs) vary depending on various sports. We exa... more The approach lengths in running single-leg jumps (RSLJs) vary depending on various sports. We examined the effects of approach length on joint kinetics in RSLJ. We analysed RSLJs for height from the approaches of 1, 3, 5, and 7 steps by 10 male jumpers. The approach length did not have a main effect on hip extension torque (from 3.18±0.46 to 3.41±0.65 Nm/kg), while the hip abduction torque increased with increase in approach length (from 1.84±0.38 to 2.62±0.66 Nm/kg). The lumbosacral lateral flexors behaved similarly to the hip abductors. Results suggest that the greater frontal torques must be exerted from longer approaches whereas the greater hip extensors are important for RSLJs from shorter approaches. The findings provide the information for athletes what torque exertion ability should be trained with a priority depending on their approach lengths.
This study aimed to reveal the effect of segmental rotation on the generation of vertical velocit... more This study aimed to reveal the effect of segmental rotation on the generation of vertical velocity and loss of horizontal velocity during take-off of a long jump. 3D motion capture system and force plates were used to capture the long jumps by nine male athletes with an approach running distance of approximately 20 m. Forward rotations of the shank and thigh of the stance leg increased vertical energy (Evert) and decreased horizontal energy (Ehori); however, elevation of the free leg side of the pelvis increased Evert (0.53 ± 0.16 J/kg), although pelvic elevation did not decrease Ehori (0.01 ± 0.02 J/kg). It was revealed that although shank and thigh movements involved the loss of horizontal velocity, elevation of the free leg side of the pelvis generated vertical velocity without the loss of horizontal velocity. This study provides evidence for a new technical approach for a long jump.
Humans seldom perform steady-state forward locomotion and often change locomotive direction throu... more 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.
Core stability is widely recognised as 'the body's ability to maintain or resume an equilibrium p... more 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.
Medicine & Science in Sports & Exercise, 2021
PURPOSE The most height-specific jumping mode, the athletic high jump, is characterized as a runn... more 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. Yet, 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) than any other segment (≤ 0.36 J/kg). CONCLUSION Compared to a straight approach, a curved approach induces greater CoM height without increasing joint kinetic exertions during take-off. The curved approach changes the initial condition of the take-off and promotes transformation of horizontal kinetic energy into Evert. This study provides novel practical perspectives for high jumpers and highlights the importance of segment and joint biomechanics in human motor performance.
Previous studies on joint kinetics during track and field block starts have been limited to lower... more 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.
Free-leg side elevation of pelvis in single-leg jump is a substantial advantage over double-leg j... more Free-leg side elevation of pelvis in single-leg jump is a substantial advantage over double-leg jump for jumping height generation,
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