Shinichi Demura

Centre of pressure sway characteristics during static one-legged stance of athletes from different sports

Abstract The frequency of one-legged stance and two-legged stance differs considerably among sports. We therefore expect the balance ability of athletes from different sports to vary. This study compared the sway characteristics during a static one-legged stance of soccer players, basketball players, swimmers, and non-athletes. The centre of pressure sway during one-legged stance of ten male participants representing each of the four groups was measured using a stabilometer. Centre of pressure sway was assessed by four sway factors: sway velocity, anterior-posterior sway, horizontal sway, and high-frequency sway. None of the four groups of participants showed significant differences in body sway between standing on the dominant leg and standing on the non-dominant leg. The soccer players had more high-frequency sway and less anterior-posterior sway and horizontal sway than the basketball players, swimmers, and non-athletes. These results suggest that soccer players have superior ability to maintain a stable one-legged stance. Further study is required to determine how much of the superior balance ability in soccer players is innate and how much is developed through training, as well as to determine the relationship between balance ability and playing performance.

Body‐sway characteristics during a static upright posture in the elderly

Aim:  This study aimed to determine the reliability and sex and age‐level differences of body‐sway parameters, based on center of pressure (COP) measurements, during a static upright posture in the elderly and to clarify their body‐sway characteristics in comparison with those of young adults.

Development of an Apparatus to Estimate Coordinated Exertion of Force

The purpose of this study was to develop a practical apparatus for estimation of the coordinated exertion of force and to develop methods for display, test duration, and sampling interval. A total of 84 healthy male college students were required to match their grip strength to a changing demand value appearing on the display of a personal computer (using two descriptions in the form of a bar chart and wave form). The variables were the maximal difference and the total sum of the differences between demanded and produced grip strength over time. In estimating coordinated exertion of force, an actual force (kgf) scale was more effective than a relative force (%) scale. Reliability tests indicated that a 30-sec. test was effective. Both bar chart and wave form displays were effective.

Ability to coordinate exertion of force by the dominant hand: comparisons among university students and 65- to 78-year-old men and women.

The purposes of this study were to examine the characteristics of ability to coordinate exertion of force in 60 healthy older people (30 men, 30 women) from the viewpoint of sex differences and to compare their performance with those of 60 healthy university students (30 men, 30 women). The test of ability to coordinate exertion of force was conducted by having the subject fit the exertion value of grip strength to a changing demand value appearing on the display of a personal computer (using a bar chart-description form). The changes in the demand value were tracked. The variable estimating ability to coordinate exertion of force was the total sum of the differences between demand and the produced grip strength induced by time lapses. The ability to coordinate exertion of force in the older subjects was inferior to that of the younger subjects, and large individual differences were observed. Unlike the younger subjects, the means of the ability to coordinate exertion of force of the older subjects significantly decreased between trials. The ability to coordinate exertion of force of the older women was significantly inferior to that of the older men, but the means of the measurements among three trials shows a similar tendency to decrease in both sexes.

LATERAL DOMINANCE OF LEGS IN MAXIMAL MUSCLE POWER, MUSCULAR ENDURANCE, AND GRADING ABILITY '

The purpose of this study was to examine lateral dominance in maximal muscle power, muscular endurance, and grading ability, using isokinetic muscular strength in knee extension and flexion. The subjects were 50 healthy male students whose ages ranged from 19 to 23 years (M height: 173.6 ±6.2 cm, M weight: 67.2 ± 6.8 kg). Their dominant legs for power exertion and for functional use were based on questionnaire items selected from those used in previous studies. The angular velocities of extension and flexion for exerting maximal muscle power were 60, 180, and 300 · sec.−1. A continuous exertion 30 times at an angular velocity of 180 · sec.−1 was used as the load for muscular endurance. For grading ability, 25%, 50%, and 75% of the maximal muscle strength at angular velocities of 60 and 180 · sec.−1 were the required values, and the difference between these values and the exerted muscular strength was evaluated. The dominant leg and nondominant leg were compared for both power exertion and functional use. There was no lateral dominance in maxima] muscle power and muscular endurance. In muscular endurance, especially, some subjects showed one leg superior in power exertion and some superior in functional use. Lateral dominance was noted across maximal muscle power and muscular endurance in grading ability. The dominant leg tended to be better than the nondominant leg in functional use. However, lateral dominance was not remarkable for flexing motion and in exertion for a short time.

The relationship of force output characteristics during a sit-to-stand movement with lower limb muscle mass and knee joint extension in the elderly.

This study examined the reliability of ground reaction force (GRF) parameters during sit-to-stand (STS) movements and the relationships between the GRF parameters and lower limb muscle mass and knee extension muscle strength. Fifty elderly females performed an STS movement twice from a chair adjusted to their knee height and the GRF, lower limb muscle mass and isometric knee extension muscle strength were measured. Reliabilities of GRF parameters were high (intra-class correlation coefficient=ICC=0.70-0.95). Parameters on force output during trunk flexion phase (ground reaction force at hip-lift off, sum of force output between beginning of STS movement and hip-lift off) differed significantly between trials, but their effect sizes were small (0.15-0.23). GRF parameters during hip-lift off and knee-hip joint extension phases significantly correlated with knee extension strength (|r|=0.29-0.64) but not lower limb muscle mass. In conclusion, the reliability of GRF during STS movement is good in hip-lift off and knee-hip joint extension phases and these phases relate significantly with lower limb muscle function. These two phases are useful for evaluation of leg muscle function of the elderly.

Setting the criterion for fall risk screening for healthy community-dwelling elderly

This study aimed to develop a criterion for screening high risk elderly using Demuras fall risk assessment chart (DFRA), compared with the Tokyo Metropolitan Institute of gerontology (TMIG) fall risk assessment chart. Participants included 1122 healthy elderly individuals aged 60 years and over (380 males and 742 females) 15.8% of whom had experienced a fall. We assessed fall risk of the elderly by DFRA and TMIG. To develop a criterion for screening high fall risk subjects among community-dwelling elderly, receiver-operating-characteristic (ROC) analysis was conducted using fall experience (separated into the categories of faller and non-faller) and the following fall risk scale scores: (1) TMIG score, (2) DFRA score, and (3) potential for falling score according to the DFRA (summing the scores of three items). In ROC analyses, the area under the ROC curve (AUC) for evaluating the potential for falling gave a value of 0.797 (95% CI=0.759-0.834) which proved better than the evaluation of the overall TMIG (0.654, 95% CI=0.600-0.706) and DFRA scores (0.680, 95% CI=0.633-0.727). Assessment of the potential for falling and fall experience are of benefit in screening for elderly persons deemed to be at a high fall risk. Further examinations based on the prospective data setting will be required.

CONCURRENT VALIDITY OF TESTS TO MEASURE THE COORDINATED EXERTION OF FORCE BY COMPUTERIZED TARGET PURSUIT

The purpose of this study was to examine concurrent validity of a new test for coordinated exertion of force. Coordinated exertion of force was measured using computerized target pursuit from the following viewpoints: the relations between the new test, a pursuit-rotor test, and a pegboard test. College students (24 men and 24 women) were required to change their grip exertion to match changing demand values (displayed in either a bar chart or a wave form) appearing on the display of a personal computer. The sum of the differences between the demanded values and grip-exertion values for 25 sec. was a parameter to evaluate the new test. The reliabilities of the new test, the pursuit-rotor, and the pegboard test were acceptable (ICC = .70 to .99). Scores on the new test showed low correlations with the pursuit-rotor and the pegboard test. The relation between the two different displays in the new test was significant but low (r = .49, p<.05). It was inferred that the new test measures a somewhat different ability than that measured by the pursuit-rotor and pegboard test and that the abilities tested by the types of displayed demand values are somewhat different.

Specific factors that influence deciding the takeoff leg during jumping movements.

Miyaguchi, K and Demura, S. Specific factors that influence deciding the takeoff leg during jumping movements. J Strength Cond Res 24(9): 2516-2522, 2010-The definition of the dominant leg (lateral dominance) is not clear, and there has been little reporting related to lateral dominance in the legs. To uncover the practical factors influencing which leg to use as the takeoff leg in 1-legged jumping movements, this study aimed to investigate the subjective dominance side of fundamental movements and to examine the lateral dominance of motor functions between the takeoff leg and non-takeoff leg. The subjects consisted of 27 young men who exercised regularly. They had not trained particularly on unilateral jumping. Fifteen men are the athlete group (left-legged jumpers group [LG]) using a left leg and 12 men are the athlete group (right-legged jumpers group [RG]) using a right leg as determined by a preliminary survey related to takeoff leg during high jump. The fundamental motions of the subjective dominant leg were investigated and the differences between the motor functions of takeoff and lead legs, such as sole shapes, single-leg vertical jump, 20-m hopping, ladder hopping, single-leg balance, and isokinetic strength were examined. It was found that many RG subjects (83%) tended to select the right leg for hopping, and many LG subjects (87%) tended to select the left leg for 1-legged balance. It was suggested that skilled movements show right-leg dominance in both takeoff leg groups. In the LG subjects, the left leg showed a higher value than the right leg in sole shape. The RG subjects showed a higher value in the right leg than in the left leg in a single-leg vertical jump. However, marked dominance was not found in the takeoff leg. The lower limbs may not show marked lateral dominance such as in the upper limbs.

Relationships between Physical Activity, ADL Capability and Fall Risk in Community-Dwelling Japanese Elderly Population

ObjectiveThe purpose of this study was to clarify the relationships among fall risk, physical activity habits, and ADL capability in a community-dwelling Japanese elderly population.MethodsThe subjects were 1,407 Japanese aged 65 or older (604 males, 803 females). Fall risk was evaluated using the Falling Assessment Chart of Suzuki et al. (2003). Physical activity habits such as the frequency of leaving the house, the use of transportation, the frequency of physical exercise, and interests were evaluated. ADL capability was evaluated using the Tokyo Metropolitan Institute of Gerontology Index of Competence.ResultsApproximately 25% of the subjects had a high fall risk (score of 5 or more). Fall risk increased with age and ADL capability decreased with age. The group with a low fall risk (score<5) had a significantly higher ADL capability than the group with a high fall risk (score≥5). From results of two-way ANCOVA (gender×physical activity habits) with age as the covariate, the fall risk of people who regularly go on leaving the house, exercise, and have interests tended to be low. Further more, the relationships between the scores and physical activity habits were examined by two-way ANCOVA with age and ADL capability as the covariates. There were significant differences in the frequency of leaving the house, and elderly persons who leaved regularly the house, had a low fall risk.ConclusionsThis study showed that fall risk is closely related to ADL capability, and that the frequency of leaving the house is very important for reducing fall risk.