Multiple EMG activity and intracortical inhibition and facilitation during a fine finger movement under pressure

The 1st purpose of this study was to examine multiple electromyography (EMG) during voluntary hand movements. A secondary purpose was to investigate possible effects of pressure on intracortical inhibition (ICI) and intracortical facilitation (ICF) functions of the motor cortex, using paired-pulse transcranial magnetic stimulation. Twelve participants traced a 15-cm diameter target circle using a small laser pointer attached to the right index finger. After 5 acquisition trials, they performed 3 nonpressure trials followed by 3 pressure trials. The results showed that pressure had effects not only on agonist EMG activity but also on multiple muscles, such as synergist. In addition, a decrease in ICI and an increase in ICF were both observed under pressure for muscles other than the agonist.     

Transient Effects of Gaze Stability Exercises on Postural Stability in Patients With Posterior Circulation Stroke

The authors sought to investigate if short-term gaze stability exercises have an effect on postural stability of dynamic standing during neck movement in patients with posterior circulation stroke (PCS). Patients in both PCS and non-PCS groups were assigned to either an intervention or control group. The intervention group performed the gaze stability exercises for 10 min while the control group was merely resting. The center of pressure velocity was calculated to evaluate the postural stability. After intervention, PCS and non-PCS showed a significant reduction in center of pressure velocity during dynamic standing with eyes closed condition, and the PCS group showed a significant improvement in eye-opened condition. This study indicated that gaze stability exercises improve PCS patients' postural control, especially during dynamic standing.     

Correlates and Prognosis in Relation to Participation in Social Activities Among Older People Living in a Community in Osaka, Japan

To examine the factors associated with social participation and to determine whether social participation is predictive of mortality, a cohort of 1405 randomly selected older people aged 65 years and over, living in Settsu, Osaka Prefecture, was followed up for 66 months. By multivariate analysis using logistic regression, female sex, older age, disability, medical treatment, no use of health checks, no daily preventive health practices, and no life worth living (no Ikigai) were independent risk factors for no participation in social activities. From the analysis using the Kaplan–Meier method, the cumulative survival rates were higher among those who took part in social activities than among those who did not in both age groups, 65–74 years and 75 years and older, for men and women. Application of the Cox proportional hazards model resulted in adjusted hazard ratio of no participation in social activities for mortality of 1.53 (95% confidence interval: 1.11–2.11), controlling for other potential factors. These results suggest that participation in social activities is closely associated with health and psychosocial conditions and may be an independent risk factor for mortality among community-residing older people.     

Energy redistribution analysis of dynamic mechanisms of multi-body, multi-joint kinetic chain movement during soccer instep kicks

The purpose of this study is to develop a model to analyze energy redistribution mechanisms of a multi-joint limb system and to examine the mechanisms underlying the production of the mechanical energy of the system during instep kicking. Kicking movements of 11 collegiate soccer players were recorded using a motion capture system, and ground reaction force during kicks was measured. Using the experimental data and the state-space power analysis developed in the current study, the kinetic energy change of the modeled segments was decomposed into causal components due to various dynamic factors (muscular and non-muscular interactive moments). The results showed that the increase of the kinetic energy of the kicking limb resulted from the energy transfer mechanisms between the decelerated segment (a proximal segment) and accelerated segment (a distal segment), induced by a non-muscular interactive moment due to the external joint force or the centrifugal force. The proximal (thigh) to distal (shank) sequential motion pattern observed was due to the energy transfer mechanism induced by the centrifugal effect acting to accelerate the shank and decelerate the thigh. The fact suggests that effective use of that mechanism may be advantageous to enhance the kinetic energy of the kicking shank. In conclusion, energy transfer mechanisms likely play a greater role in dynamic kicking than muscle power output, and better coordination to exchange kinetic energy among segments makes kicking more efficient.     

Relationship Between Social Relations and Mortality of Older Japanese People Living Alone

The association of social relations with mortality was studied over a 54-month period in 535 older Japanese people living alone. Sex-specific proportional hazard analyses indicated that finding it difficult to establish and maintain relationships with other people was significantly related to mortality, regardless of age, general health status, history of health management, psychological conditions, or economic status. The adjusted hazard ratio for finding relations with other people difficult was 4.61 [95% confidence interval (CI): 1.39–15.30] for men and 4.56 (95% CI: 2.19–9.48) for women. The adjusted hazard ratio for nonparticipation in social activities was 1.45 (95% CI: 0.42–4.97) for men and 1.72 (95% CI: 0.70–4.22) for women and did not reach statistical significance. On the other hand, there was a gender difference in the direction of the association between a low-level contact with children, siblings, or other relatives and mortality, for which the adjusted hazard ratio was 3.16 (95% CI: 0.94–10.62) for men and 0.51 (95% CI: 0.27–0.97) for women. These results suggest the need to create a different model for the relationship between social relations and mortality for men and for women living alone.     

Effects of Voluntary and Automatic Control of Center of Pressure Sway During Quiet Standing

The authors investigated the effects of voluntary and automatic control on the spatial variables (envelope area, maximal amplitude, and root mean square [RMS]) of center of pressure (COP) displacement during quiet standing and identified differences in their postural control strategies (mean velocity [MV], mean power frequency [MPF], and power density). COP data were recorded under relaxed (experimental control), still (voluntary control), and dual (automatic control) conditions. RMS was significantly lower in the still and dual conditions than in the relaxed condition. MV, MPF, and power density were significantly higher in the still condition than in the dual condition. These results indicate that both voluntary and automatic control decrease the spatial variables of COP displacement; however, their postural control strategies are different.     

Hemispace Asymmetries and Laterality Effects in Arm Positioning

Hemispace asymmetries and laterality effects were examined on an arm positioning reproduction task. Sixteen male subjects were asked to reproduce both abductive and adductive positioning movements with the left or right arm within either the left or the right hemispace. Hemispace was manipulated using a 90 degrees head-rotation paradigm. A left hemispace advantage in positioning accuracy was predicted for both left and right arm movements on the grounds that the perceptual-motor control of positioning movements made in left hemispace is primarily mediated by the right hemisphere which is known to be advantageous for tasks which are spatial in nature (Heilman, Bowers, & Watson, 1984). No arm laterality effects were predicted to occur because the proximal musculature involved in the control of arm movements is innervated from both contralateral and ipsilateral cerebral hemispheres (Brinkman & Kuypers, 1973). Results showed that the predicted left hemispace advantage was evident for the right arm on the positioning variability measure alone, whereas it was absent for all other possible conditions on all error measures. Laterality (arm) effects were absent as predicted. The experiment also demonstrated a greater degradation of reproduction performance under the ′crossed" arm-hemispace conditions than under the ′uncrossed" conditions. A plausible explanation for the uncrossed advantage for the task is that under normal conditions, a single hemisphere is primarily responsible for both controlling the contralateral arm and directing attention to the contralateral hemispace, and consequently potential interhemispheric interference is minimized. A clear response bias effect in movement reproduction was also evident as a function of the direction of concurrent arm movement and head rotation. Arm movements made in the same direction as head rotation were systematically undershot in reproduction to a much greater degree than arm movements made in the opposite direction to head rotation.