We conducted one‐atmosphere uniaxial compression experiments on fine‐grained (~1 μm) Fe‐bearing olivine (Mg1.8Fe0.2SiO4) aggregates that were variably doped with CaO ± Al2O3. We identified power‐law interface‐controlled creep at low stresses and grain‐boundary diffusion creep at high stresses, which operate as mutually coupled, that is, sequential processes. We established constitutive equations for interface‐controlled creep and diffusion creep of undoped olivine and used the combined rate equation as a reference to examine the effect of doping on creep rates. Ca and Al were found to enhance rates of both interface‐controlled creep and diffusion creep above certain temperatures, and this effect becomes significant with increasing temperature. We attribute the rate enhancements to grain‐boundary disordering promoted by grain‐boundary segregation of the dopants at near‐solidus conditions. The enhancements are well described in relation to the sample solidus temperature and an additional activation energy relative to that of the reference creep state.

Joint angle kinematics of the throwing limb from the early-cocking phase to ball release were investigated for the fastball (FB) and curveball (CB) baseball pitches through use of a three-dimensional film analysis technique. Small sticks were fixed to the hand and forearm to permit rotations of the radioulnar and wrist joint to be calculated. The actions were very similar for two pitches within one subject. There were no differences in the motions of the shoulder and elbow joints or in the temporal sequences between FB and CB pitches. However, there was a significant difference (p<0.05) in the motion of supination/pronation of the forearm and dorsiflexion/palmar flexion of the wrist prior to the ball release; the forearm was supinated more in the CB (maximum supination: 39.9 ±6.0° at 0.072 ±0.045 s before ball release, or BRL) compared to the FB (19.4 ±8.5° at 0.076 ±0.046 s before BRL), whereas the wrist was dorsiflexed more in the FB (maximum dorsiflexion: 41.7 ±6.5° at 0.039 ±0.011 s before BRL) compared to the CB (31.2 ±4.7° at 0.036 ±0.013 s before BRL) during late-cocking and acceleration phases leading to the ball release.

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Study design: This cross-sectional study was conducted by comparing bone mineral density (BMD) of paraplegic and quadriplegic patients. Objectives: The purpose of this study was to investigate the relationship between the bone mineral loss and injury level in spinal cord injury patients. Settings: Experiments were conducted at Yoneda Hospital and Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan. Methods: Lumbar spine (L2-4), proximal femur (femoral neck, trochanter region and Ward's triangle) and whole body BMD were measured in ten paraplegic and ten quadriplegic patients using dual-energy X-ray absorptiometry (DXA, HITACHI BMD-1X). Results: Signi®cant di erences were observed in the lumbar spine, trochanter region and upper extremities BMD between paraplegic and quadriplegic patients (P50.05, P50.05 and P50.01, respectively), but not in the femoral neck, Ward's triangle, head, pelvis, lower extremities or whole body BMD. Conclusion: These results suggest that the injury level in¯uences on the lumbar spine, upper extremities and trochanter region BMD. From a biomechanical standpoint, it is possible to explain that the di erences in mechanical loading exerted on bones also a ected the di erence of lumbar spine BMD in the two groups.

To prevent a decline in gait with age, it is necessary to investigate age-related changes in gait performance and detect related factors. The purpose of this study was to assess the association between gait ability and leg extension power among middle-aged and elderly people. Height, weight, maximum gait velocity (MGV) and leg extension power (LEP) were measured in 752 males and females who participated in the National Institute for Longevity Sciences, Longitudinal Study of Aging (NILS-LSA). Age-related changes in MGV and LEP and the association between MGV and LEP were assessed. There were significant decline trends in height, weight, MGV and LEP with advancing age (p<0.001). MGV showed a significantly positive correlation with LEP (in males: r=0.48 p<0.001, in females: r=0.47; p<0.001). Subjects aged 60yrs and over showed a significantly higher correlation than those under 60yrs in males, but not in females, after adjustment for height and weight. Although the relationships between MGV and LEP were different by age and gender, LEP may be one of the important factors in maintaining gait ability.

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In Part 1 of this study (Yabe et al., 2020, https://doi.org/10.1029/2020JB019415), we established an olivine grain‐boundary diffusion creep law that incorporates the chemically induced enhancement of creep rates, which becomes significant with increasing temperature. The effect was attributed to grain‐boundary disordering that starts at ~0.92 × solidus (bulk eutectic temperature). In this study, we estimated solidus temperatures of the samples used in the previous diffusion creep experiments. These temperatures were used to compare previously reported diffusion creep rates for olivine with our established diffusion creep law. We found that the law explains a difference of up to 2 orders of magnitude in olivine creep rates at the same temperatures, stresses, grain sizes, and water contents in the previous studies. The geotherm normalized by the mantle solidus was calculated for the upper mantle with water contents ranging from 0 to 300 μg/g, which predicts depths where grain‐boundary diffusion creep is enhanced due to grain‐boundary disordering. Constructed viscosity‐depth profiles reveal a very thin mantle lithosphere beneath mid‐ocean ridges, with development of the lithosphere away from the ridge, leaving a low‐viscosity region below. Given a grain size of 1 mm and depending on the water content, a viscosity of 2–5 × 1019 Pa·s is predicted for the low‐viscosity mantle beneath 50‐million‐year‐old seafloor.

The effects of pre-motion silent period (PSP) on dynamic force exertion were studied in ten healthy subjects performing ballistic elbow extensions. The experiments were designed to evaluate the significance of mean differences between the averaged dynamic force curves of two groups: PSP-presence groups and PSP-absence groups. The presence of PSP was judged quantitatively and automatically by means of a newly developed method using statistical analysis. The results indicated that there were two effects of PSP on dynamic force exertion: one was a reducing effect, observed prior to the movement; the other was a reinforcing effect, observed in the first part of the ballistic movement. The duration of the reinforcement was significantly correlated with the duration of the reducing effect of PSP. The findings suggested that the reinforcement of dynamic force may be produced by the pre-stretch of agonistic muscles caused by prior force reduction due to PSP occurrence. The fact that PSP plays an important role in dynamic force exertion suggests that PSP may be incorporated in the central motor control system designed to interrupt the background activity, to stretch the agonist and to reinforce the dynamic force.