INTER-JOINT DIFFERENCES EXIST IN KINETIC DEMAND FOR PERFORMANCE IN HIGH JUMP

We aimed to clarify the lower-limb kinetic determinants of inter-individual variability in flight height in the high jump. We hypothesised that although the take-off of the high jump requires great external power, the proximal (hip) joint is required to function as a stabiliser rather than as a power generator for higher performance. We analysed high jump motions by 16 male high jumpers. For the hip joint, only maximum torque significantly correlated with the flight height. Meanwhile, for the knee joint, both peak positive power and peak torque were correlated with the flight height, with a stronger correlation for power than for torque. We found that the kinetic requirement for performance differs between joints, which provides the practical implication that the musculoskeletal functions to be trained differ between joints, such as torque exertion for the hip and power exertion for the knee

EFFECTS OF SEGMENTAL ROTATIONS ON VERTICAL AND HORIZONTAL ENERGIES DURING TAKE-OFF OF A LONG JUMP

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

ABSENT MUSCLE COORDINATION PATTERNS AND REDUCED FORCE EXERTION IN THE NOVICE OF CLEAN EXERCISE

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

DIFFERENT EFFECTS OF APPROACH LENGTH ON SAGITTAL AND FRONTAL JOINT KINETICS DURING A RUNNING SINGLE-LEG JUMP

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

HIP AND LUMBOSACRAL JOINT CENTRE LOCATIONS IN ASIAN POPULATION: BIASES BY EXISTING REGRESSIONS AND DEVELOPMENT OF NEW METHODS

Accurate prediction of the lumbosacral and hip joint centres (LSJC, HJC) is crucial for the analysis of lumbo-pelvic-hip dynamics in various movements. Here we show that pre-existing regressions proposed by European research groups produce biased estimates of the LSJC and HJC in Japanese males and females (n = 23, 24), and that the biases in LSJC depend on sex. When compared to locations directly measured by MRI, the pre-existing regressions estimated the LSJC to be more posterior in males and more inferior and posterior in females, and the HJC to be more medial for both sexes. We suggest the importance of considering racial and sexual differences in morphology. We propose new regressions for Asians and validate them using leave-one-out cross-validation. Our regression can be a powerful solution for accurate motion analysis in Asians

ASSOCIATIONS BETWEEN EXERCISE-INDUCED FLATTENING OF FOOT ARCH AND FATIGUE OF EXTRINSIC AND INTRINSIC FOOT MUSCLES

We aimed to examine the associations between exercise-induced flattening of the foot arch and fatigue of extrinsic and intrinsic foot muscles. Fifteen male participants repeated 100 hops/set until they could no longer maintain the hop frequency or had completed 30 sets. The sagittal plane range of motion (ROM) of the midfoot during stance phase significantly decreased at the final set compared to the initial set (-8.8°). After the fatigue task, MRI T2 relaxation time in all measured extrinsic and intrinsic foot muscles significantly increased (17.2‒37.4%); however, only its increase in the tibialis posterior (TP) correlated with the relative change in midfoot ROM (r = 0.684). These results suggest that fatigue of TP is associated with the occurrence of flattening of the foot arch. This study provides a clinical implication that monitoring midfoot kinematics can be used to assess the condition of TP

Chemokine and Free Fatty Acid Levels in Insulin-Resistant State of Successful Pregnancy: A Preliminary Observation

Increased insulin resistance and inflammatory action are observed in pregnancy-induced hypertension (PIH), but similar insulin resistance is observed also in successful pregnancy. To estimate insulin resistance and inflammatory activity in normal pregnancy and PIH, serum concentrations of free fatty acids (FFA; corrected with albumin to estimate unbound FFA), monocyte chemoattractant protein (MCP)-1, and high-molecular weight (HMW) adiponectin were measured in severe PIH patients with a BMI less than 25 kg/m2 and were measured 3 times during the course of pregnancy in women with normal pregnancies. FFA/albumin, MCP-1, and HMW adiponectin concentrations were significantly higher in PIH patients than in women with normal pregnancies. The 3 measurements of FFA/albumin showed a significant increase through the course of uncomplicated pregnancies. In contrast, MCP-1 and HMW adiponectin were significantly decreased during the course of pregnancy. These results suggest that the reduced MCP-1 concentration in normal pregnancy may be a pathway to inhibit the induction of pathological features from physiological insulin resistance and homeostatic inflammation

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