Reliability and fall experience discrimination of Cross Step Moving on Four Spots Test in the elderly.

OBJECTIVES: To examine the reliability and fall experience discrimination of the Cross Step Moving on Four Spots Test (CSFT) and the relationship between CSFT and fall-related physical function. DESIGN: The reliability of the CSFT was examined in a test-retest format with the same tester. Fall history, fall risk, fear of falling, activities of daily living (ADL), and various physical parameters were measured for all participants. SETTING: A community center and university medical school. PARTICIPANTS: Elderly community-dwelling subjects (N=533; 62 men, 471 women) aged 65 to 94 years living independently. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Time to complete all the CSFT steps required, fall risk score, ADL score, and fall-related physical function (isometric muscle strength: toe grip, plantar flexion, knee extension, hip flexion, hand grip; balance: 1-leg standing time with eyes open, functional reach test using an elastic stick; and gait: 10-m maximal walking speed). RESULTS: The trial-to-trial reliability test indicated good reliability of the CSFT in both sexes (intraclass correlation coefficient =.833 in men, .825 in women). However, trial-to-trial errors increased with an increase in the CSFT values in both sexes. Significant correlations were observed between the CSFT values and scores for most fall-related physical function tests in both sexes. However, the correlation coefficient for all significant correlations was <0.5. Two-way analysis of variance (sex × fall experience) revealed that the fall experience is a significant factor affecting CSFT values; values in fallers were significantly lower than those in nonfallers. The odds ratios in logistic regression analysis were significant in both sexes (men, 1.35; women, 1.48). As determined by the Youden index, the optimal cutoff value for identifying fall experience was 7.32 seconds, with an area under the curve of .676. CONCLUSIONS: The CSFT can detect fall experience and is useful in the evaluation of different fall-related physical functions including muscle strength, balance, and mobility.

Gait characteristics when walking with rounded soft sole shoes.

This study aimed to examine the effect of shoes with a rounded soft sole (Stretch Walker: SW) on gait. Fifteen healthy male (mean age: 23.2) walked under three conditions (SW, Flat-bottomed Shoe: FS, Barefoot: BF). Including walking speed, stance time, step length were selected as temporal-spatial parameters. The angle of hip, knee, and ankle joints during particular phases were selected as kinematic parameters. Walking speed, stance time, step length and flexion angle of the ankle joint at initial contact were greater when wearing either shoe than walking BF; cadence was faster walking BF than wearing either shoe; double support time increased (FS>SW>BF); step width was greater (FS>SW>BF); walking angle was greater wearing the SW than wearing the FS and walking BF; and range of motion and maximum flexion angle of the hip and knee joints were greater wearing the FS than walking BF. In conclusion, wearing the SW with a heel-to-toe rocker and soft sole changes the double support time, step width, and walking angle and increases step length and walking speed compared to walking BF. The difference of the range of motion in hip and knee joints was larger between walking BF and wearing the FS than between walking BF and wearing the SW.

Different gripping intervals in reproducibility of force-decreasing curve and muscle oxygenation kinetics during sustained maximal gripping.

The purpose was to examine the properties and reproducibility of the force-decreasing curve and muscle-oxygenation kinetics measured by near infrared spectroscopy in sustained isometric grip and rhythmic repeated grip measurements using various contraction intervals (2 to 5 sec.). 10 healthy young adults performed both grip tests for 6 min., during which muscle-oxygenation kinetics were measured. The intraclass correlation coefficients of the time to reach the minimum value for oxygenated hemoglobin and myoglobin tended to become lower with longer relaxation time, especially over a 3-sec. interval. Although blood-flow obstruction closely influences the initial decreasing grip force during both grip tests with a 2-sec. interval, the decreasing grip force during rhythmic repeated gripping with over a 3-sec. interval is low. Hence, the physiological mechanism related to rhythmic repeated grip with over a 3-sec. interval may differ from that related to sustained isometric grip and rhythmic repeated grip with a 2-sec. interval.

Effect of linear polarized near-infrared light irradiation and light exercise on muscle performance.

This study aimed to determine the effect of active warm-up by local muscle light exercise and passive warm-up by polarized light irradiation on skin and muscle temperatures and forearm muscle performance (muscle strength, power, endurance, and controlled force-exertion). Ten healthy males performed various grip tests before and after active (local muscle light exercise) and passive (linear polarized near-infrared light irradiation) warm-ups. An active warm-up involved intermittent gripping exercise (contraction: 1 second and relaxation: 1 second) for 10 minutes using a sponge. A passive warm-up consisted of polarized light irradiation to the forearm (superficial digital flexor) for 10 minutes (irradiation: 5 seconds and rest: 1 second). Skin and muscle temperatures were measured during both warm-ups. Skin and muscle temperatures increased significantly after 5 minutes of local muscle light exercise and after 10 minutes of polarized light irradiation. Temperatures were significantly higher after 6 minutes of local muscle light exercise than after 6 minutes of polarized light irradiation. There were no significant differences of muscle strength, power, and controlled force-exertion before and after either warm-up. Average force outputs in all conditions significantly decreased with exertion time, and at 30, 60, 90, and 120 seconds they were higher in both warm-up conditions than in the non-warm-up condition. In conclusion, both warm-ups may contribute to improve muscle endurance performance in the decreasing force phase.

Effect of L-ornithine hydrochloride ingestion on intermittent maximal anaerobic cycle ergometer performance and fatigue recovery after exercise.

L-Ornithine plays an important role in ammonia metabolism via the urea cycle. This study aimed to examine the effect of L-ornithine hydrochloride ingestion on ammonia metabolism and performance after intermittent maximal anaerobic cycle ergometer exercise. Ten healthy young adults (age, 23.8 ± 3.9 year; height, 172.3 ± 5.5 cm; body mass, 67.7 ± 6.1 kg) with regular training experience ingested L-ornithine hydrochloride (0.1 g/kg, body mass) or placebo after 30 s of maximal cycling exercise. Five sets of the same maximal cycling exercise were conducted 60 min after ingestion, and maximal cycling exercise was conducted after a 15 min rest. The intensity of cycling exercise was based on each subject's body mass (0.74 N kg(-1)). Work volume (watt), peak rpm (rpm) before and after intermittent maximal ergometer exercise and the following serum parameters were measured before ingestion, immediately after exercise and 15 min after exercise: ornithine, ammonia, urea, lactic acid and glutamate. Peak rpm was significantly greater with L-ornithine hydrochloride ingestion than with placebo ingestion. Serum ornithine level was significantly greater with L-ornithine hydrochloride ingestion than with placebo ingestion immediately and 15 min after intermittent maximal cycle ergometer exercise. In conclusion, although maximal anaerobic performance may be improved by L-ornithine hydrochloride ingestion before intermittent maximal anaerobic cycle ergometer exercise, the above may not depend on increase of ammonia metabolism with L-ornithine hydrochloride.

Examination of validity of fall risk assessment items for screening high fall risk elderly among the healthy community-dwelling Japanese population.

We aimed to examine the validity of fall risk assessment items for the healthy community-dwelling elderly Japanese population. Participants were 1122 healthy elderly individuals aged 60 years and over (380 males and 742 females). The percentage who had experienced a fall was 15.8%. This study used fall experience and 50 fall risk assessment items representing the five risk factors (symptoms of falling, physical function, disease and physical symptom, environment, and behavior and character), as we described before. The accuracy of predicting fall experience from the total score or each risk factor score was examined by discriminant analysis. The percentage correctly distinguishing the faller from the total score was 14.4%, and that from the five risk factor scores was 39.7%. This percentage, when using each risk factor score as an independent variable, was 42.5% (symptom of falling), 0.6% (physical function score), 0.6% (disease and physical symptoms score), 0.0% (environment score), and 1.1% (behavior and character score), respectively. The best predictor of fall experience of the community-dwelling elderly was the "symptom of falling" score. For fall risk assessment of the community-dwelling elderly, both of screening of fall risk level and assessing risk profile comprehensively is important.

Accuracy of simple predictive equations for visceral fat area after 8 weeks of training.

We previously proposed two predictive equations of visceral fat area applicable in a field setting (Demura & Sato, 2007a, 2007b). One uses the fat mass of the trunk measured by bioelectrical impedance as the main predictor (equation 1) and the other uses internal fat mass estimated from several anthropometric variables (equation 2). In this study, we examined the inter- and intra-individual accuracy of estimated values using these equations after 8 weeks of exercise training. Participants were 42 Japanese adults aged 42.7 +/- 10.3 years (22 males, 20 females). Visceral fat area, body composition, and blood biochemistry were measured at baseline and after 8 weeks. There were no significant differences in reference visceral fat area measured by computed tomography and visceral fat area predicted by the equations either at baseline or after 8 weeks, and the values were highly consistent (equation 1: baseline R(2) = 0.829, after R(2) = 0.860; equation 2: baseline R(2) = 0.832; after R(2) = 0.850). No significant relationship was observed between the reference and change in visceral fat area for equation 1 (males: r = 0.272, P > 0.05; females: r = 0.428, P > 0.05), but there was a significant relationship for females with equation 2 (males: r = 0.279, P > 0.05; females: r = 0.474, P <0.05). Our findings indicate that these equations have high inter-individual consistency but low intra-individual consistency with the reference and are of limited use for the longitudinal evaluation of visceral fat area.

Influence of high ambient temperatures on the physiological responses and body sway in healthy young adults after quickly standing.

This study was aimed to compare the variations in cerebral oxygenation, blood pressure and center-of-foot pressure after standing from sitting and supine positions at normal (22 degrees C) and high (32 degrees C) room temperatures. Thirty young adults stood up from a resting posture (sitting or supine position) and kept the static standing posture for 90 sec. Meanwhile, their center-of-foot pressure (COP), blood pressure, and cerebral oxygenation kinetics were measured in continuity. The change of the frequency domain low-to-high frequency (LF/HF) ratio of the R-R interval before and after standing from a supine position was significantly higher than that from a sitting position under both temperature conditions. Blood pressure as well as total and oxygenated hemoglobin levels decreased immediately after standing up and the ratio of blood pressure change when moving from a supine position to standing at high room temperature was the largest as compared with the other conditions. Total hemoglobin (Hb) volume was found to temporarily decrease after standing and required 22-24 sec to recover when the subject started from the sitting position and 33-36 sec when the subject started from the supine position. Cerebral oxygenation kinetics tended to be larger under high, rather than normal, temperature conditions. All COP parameters after standing were significantly larger in the high temperature condition than in the normal temperature condition. Body sway after standing was larger in the high temperature condition than in the normal temperature condition and after standing from a supine position than from a sitting position. In conclusion, cerebral oxygenation kinetics and blood pressure measured after the subject moved to the standing position changed dramatically under high temperature conditions, and variations in this parameter may influence body sway.

Changes in subjective muscle fatigue sensation and blood lactate and their relationships with decreasing force during sustained handgripping using various target values and its recovery stage.

The purpose of this study was to examine the relationship between the level of subjective muscle fatigue sensation (SMS) and the physiological responses to decreasing force during and after sustained and constant effort static gripping (SSG) at 50, 75 and 100% of the maximal voluntary contraction (MVC). The subjects were 10 healthy males without upper extremity impairments. Each subject performed SSG for 6 min with three target forces. SMS of the forearm by Borg's CR 10 scale was measured every 30 sec during and after the SSG. The blood lactate concentration (La) and MVC were measured before the SSG and at 0, 4 and 7 min after the SSG. There were no significant differences in the average grip force after 30 sec from the SSG onset between the target forces. The SMS for 75% MVC during the SSG increased markedly, and was the highest at 30 sec after the onset (p < 0.05). Although the La at 4 min was higher than that before the SSG, the La recovered to 80% at 7 min after the SSG, and the SMS recovered almost completely. The cross correlation coefficients between the increasing SMS and decreasing force during the SSG were very high in all conditions (r(xy) = -0.819 to -0.979, -0.930 to -0.988, -0.789 to -0.985, for 50%, 75% and 100%, respectively; all coefficients: lag = 0), but the relationships between the recovery ratio of the SMS and that of the maximal grip force at 4 and 7 min after the SSG were low. In addition, the relationships between the recovery ratio of the La and the maximal grip force for 75% MVC were high at 0 and 4 min after the SSG (r = -0.814, -0.744, respectively). In the case of sustained muscle contraction for a long time, there were no significant differences between the target forces for the SMS, La and maximal grip force after SSG, and the degree of muscle fatigue was considered to be similar at each target force. However, the SMS during SSG, especially before the gripping force decreased to the almost steady state, may differ at each target force.

Changes in elbow flexor power with intermittent contractions and various loads.

This study examined intermittent elbow flexion every 2 sec. for 1 min. using various loads to study the properties of muscle power output and their relationship to peak power, defined as the maximum power output. 18 young men performed intermittent explosive elbow flexion (30 times x min.(-1)) using 30%, 40%, and 50% maximal voluntary contraction (MVC). The power outputs at 30% and 40% MVC slightly decreased (rate of decrease from peak power to average power output during the 26 to 30 contractions was about 5%). However, at 50% MVC, there was a marked decrease (33.6%). Power output for 8 contractions was significantly larger at 50% MVC than at 30% and 40% MVC, but after 9 contractions there was no significant difference between 40% and 50% MVC. In addition, after 27 contractions, 40% MVC was significantly larger than 30% and 50% MVC. That is, the tendency for power output to decrease differed among the various loads. The rate of decrease of power outputs showed no significant correlation with peak power for each load. Therefore, the rate of decrease of power output in intermittent contractions may help sustain the power output and cannot be evaluated as accurately as peak power.

Sex differences of intermittent elbow flexion power using various loads.

This study was designed to clarify a sex difference in muscle power output properties by intermittent elbow flexion using various loads. 10 young males and 10 young females performed intermittent elbow flexion power outputs at 30 times x min.(-1) for 1 min. using 30%, 40%, and 50% MVC loads. For both sexes, the decreasing peak power showed a similar trend between trials at all loads, and the reliability of each power parameter was good. The power outputs decreased largely with increasing load mass, and the power output in 50% MVC for males markedly decreased to the same level as that during the final phase in 30% MVC. Although the absolute value of regression coefficients for males became significantly larger with increasing load mass, that for females showed a significant difference only between 30% and 50% MVC. In 50% MVC, a large decrease for males was observed. Maximal peak power outputs were significantly larger with increasing load mass for both sexes, but for males more than for females. In both sexes, there were no significant differences among final powers of each load mass, and between total powers of 40% and 50% MVC. For the sum of every 5 consecutive power outputs, males showed significant differences between 30% and 40% MVC in all periods after the 6th contraction, but females did not and also between 30% and 50% MVC in periods after the 16th contraction. In conclusion, it is considered that power outputs in the latter phases in 50% MVC are affected largely by muscle fatigue, and an intermittent power output test with 50% MVC can measure sustained power (fatigue resistance) in the latter phases, but there is a sex difference in the tendency to decrease.

Sex and age differences of relationships among stepping parameters for evaluating dynamic balance in the elderly.

This study aimed to examine the relationships among various stepping parameters, sex, and age in the elderly. Healthy elderly Japanese individuals 60-85 years old (50 males and 61 females) performed 4 types of stepping motions for 20 s. Stepping motions included bilateral stepping (back/forth and right/left) and unilateral stepping (back/forth and right/left). The number of steps, the average connecting time of a foot during one step, and the average time of both feet touching the floor at the same time (bilateral connecting time) were measured with a foot switch sheet. The trial-to-trial reliability was very high (above 0.86) except for the bilateral connecting time in the bilateral stepping back/forth test for 70-85 year olds (males: 0.67, females: 0.68). With age, the number of steps was significantly smaller, and the average connecting time and the bilateral connecting time were shorter in all stepping tests. There were significant sex differences in bilateral connecting time for bilateral stepping right and left and the number of steps for the bilateral stepping back and forth and the unilateral stepping right and left tests. The number of steps and average connecting time showed high correlations between bilateral stepping right/left and back/forth (r=0.71-0.94) and between unilateral stepping back/forth and right/left (r=0.87-0.99). There were significant correlations of the average connecting time between bilateral and unilateral stepping motions (r=0.51-0.83), but both stepping motions are considered to have different motion properties from the viewpoint of center of gravity sway. The correlations between the bilateral connecting time and the number of steps in bilateral stepping were relatively low (males: /r/<0.70, females: /r/<0.57). The bilateral connecting time was near 0 s in many males; thus, it may depend greatly on individual or sex differences in stepping strategy. These results suggest that the stepping motions used in this study can evaluate dynamic balance ability, and that the unilateral test may be useful for the elderly who cannot walk independently with ease.

Relationships between force-time parameters and muscle oxygenation kinetics during maximal sustained isometric grip and maximal repeated rhythmic grip with different contraction frequencies.

The purposes of this study were to examine the relationships between various force-time parameters and muscle oxygenation kinetics during maximal sustained isometric grip (SIG) and maximal repeated rhythmic grips (RRG) with different grip intervals (interval times: 5, 4, 3, and 2 s). Subjects were 10 healthy young males, aged 20-26 years (height 173.9+/-7.3 cm, body mass 71.5+/-11.2 kg). After measuring maximal grip force, each subject performed the SIG and RRG tests with a target frequency of 12, 15, 20, and 30 grips.min(-1) (interval times: 5, 4, 3, and 2 s, respectively) for 6 min. The decreasing time until 80% MVC showed significant and high correlations with final force values in RRGs with over 3 s intervals (r=0.866-0.941), but not in the SIG and RRG with a 2 s interval. The time at the lowest Oxy-Hb/Mb value showed a significant and high correlation with the time at the highest Deoxy-Hb/Mb value only in the SIG and RRG with a 2 s interval (r=0.825-0.916). Oxy-Hb/Mb decreases markedly and deoxy-Hb/Mb increases after the onset of SIG due to the obstruction of blood flow caused by the increase in intramuscular pressure. A similar physiological response to that of SIG occurs also in RRG with a 2 s interval, but RRGs with intervals over 3 s achieve more resumption of blood flow in the muscular relaxation phase. Hence, in spite of the same RRGs, it was determined that RRGs with intervals over 3 s differ significantly in a changing pattern of grip force and muscle oxygen kinetics from RRGs with a 2 s interval.

Effects of room temperature and body position change on cerebral blood volume and center-of-foot pressure in healthy young adults.

This study aimed to examine the effects of room temperature and body position changes on cerebral blood volume, blood pressure and center-of-foot pressure (COP). Cerebral oxygenation kinetics and blood pressure were measured by near infrared spectroscopy (NIRS) and volume-compensation, respectively, in 9 males and 9 females after rapid standing from sitting and supine positions in low (12 degrees C) or normal (22 degrees C) room temperatures. COP was also measured in a static standing posture for 90 s after rapid standing. The total hemoglobin (Hb) decreased just after standing. Blood pressure after standing at normal temperature tended to decrease immediately but at low temperature tended to decrease slightly and then to increase greatly. The decreasing ratio of total Hb and blood pressure upon standing from a supine position at normal room temperatures was the largest of any condition. Total Hb recovered to a fixed level approximately 25 sec after standing from a sitting position and approximately 35 sec after standing from a supine position. All COP parameters after standing tended to change markedly in the supine position compared to the sitting position, especially at normal temperatures. The COP parameters after standing in any condition were not significantly related to the decreasing ratio of total Hb but were related to the recovery time of total Hb after standing. In conclusion, decreasing ratios of total Hb and blood pressure after standing from a supine position at normal temperatures were large and may affect body sway.

Attention of postural control on foot somatosensor disturbance caused by the compression of blood vessels.

This study aimed to compare the center of foot pressure (CFP) during different ischemia periods by cuff compression. Ten healthy young adult males held their CFP for 1 min before and after cuff compression (250 mmHg) of lower limb blood vessels during two different compression periods (10 min and 26 min). Two-point discrimination thresholds and electric stimulus perception thresholds of each subject's right foot sole were measured during cuff compression to examine changes in the perceived level of cutaneous and proprioceptive sensation by blood flow inhibition. In addition, oxygenation kinetics in the anterior tibial muscle tissue was examined by near-infrared spectroscopy during cuff compression. The CFP was evaluated by using 36 parameters. CFP deflection tended to increase after cuff compression and to be larger over a long ischemic time (26 min) as compared with a short ischemic time (10 min). The proprioceptive perception threshold using electric stimulation showed a significant interaction and was higher after 26 min ischemia than at the initial timepoint and after 10 min ischemia. The delta[Oxy Hb/Mb], delta[Deoxy Hb/Mb] and Tissue oxygenation index (TOI) changed significantly after both ischemic conditions than at the initial condition. There was no significant difference in the Tissue oxygenation index and delta[Deoxy Hb/Mb] between both ischemic conditions. Many parameters regarding the deflection velocity and anteroposterior and lateral deflection had significantly larger values after 26 min ischemia than at the initial time point and after 10 min ischemia. Postural deflection may not be affected by the oxygen deficiency of muscle tissues caused by the compression of blood vessels for 10 min, but strongly affected by the cutaneous and proprioceptive sensation disturbances occurring from compression lasting over 10 min.

Effect of linear polarized near-infrared light irradiation on muscle fatigue recovery after repeated handgrip exercise.

Linear polarized near-infrared light (PL) irradiation is considered one of the useful methods for muscle fatigue recovery, because it increases the blood flow and skin temperature of the irradiated part. The purpose of this study was to examine the effect of PL-irradiation on muscle fatigue recovery and physiological response in the upper limbs after maximal repeated rhythmic hand gripping (RRH). Ten males and ten females participated in this study. Subjects performed RRH for 9 min, and then rested for 20 min with PL- or placebo-irradiations. After rest, they again performed RRH for 3 min. As evaluation parameters, we selected the sustained force curve during RRH, subjective muscle-fatigue sensation (Fs), blood lactate concentration (La), muscle oxygenation (Total Hb, Oxy-Hb, and Deoxy-Hb), and skin temperature. The decreasing rate of the integrated area for 30 sec during RRH was significantly smaller in the PL-irradiation than with the placebo. There were no significant differences between irradiation conditions for fatigue sensation and lactate concentration skin temperature during rest was kept high by PL-irradiation. Muscle oxygenation tended to remain slightly high during the initial phase (1-8 min after the exercise). It is inferred that PL-irradiation maintains a high skin temperature and blood flow, but it may not contribute to recover muscle contraction performance in muscle fatigue.

The properties and interrelationships of various force-time parameters during maximal repeated rhythmic grip.

The purpose of this study was to examine the properties and interrelationships of various force-time parameters including the inflection point for the rate of decline in force during a maximal repeated rhythmic grip. Fifteen healthy males (age M=21.5, SD=2.1 yr, height M=172.4, SD=5.7 cm, body mass M=68.2, SD=9.2 kg) participated in this study. Subjects performed a maximal repeated rhythmic grip with maximal effort with a target frequency of 30 grip.min(-1) for 6 min. The force value decreased linearly and markedly until about 70% of maximal strength for about 55 s after the onset of a maximal repeated rhythmic grip, and then decreased moderately. Because all parameters showed fair or good correlations between 3 min and 6 min, they are considered to be able to sufficiently evaluate muscle endurance for 3 min instead of 6 min. However, there were significant differences between 3 min and 6 min in the integrated area, the final force, the rate of the decrement constant (k) fitting the force decreasing data to y=ae(-kx)+b and the force of maximal difference between the force and a straight line from peak force to the final force. Their parameters may vary generally by the length of a steady state, namely, a measurement time. The final force value before finishing and the rate of the decrement constant (k) reflect the latter phase during a maximal repeated rhythmic grip. Although many parameters show relatively high mutual relationships, the rate constant (k) shows relatively low correlations with other parameters. We inferred that decreasing the time until 80% of maximal strength and the amount of the decrement force for the first 1 min reflect a linear decrease in the initial phase.

Sex differences and properties of the decreasing force during sustained static grip at various target forces.

The purpose of this study was to examine properties and sex differences of the decreasing force during sustained isometric grip using various target forces, 50%, 75%, and 100% of maximal voluntary contraction (MVC), for 6 min. Participants were healthy, 15 men (height = 172.9 +/- 4.6 cm, body mass = 67.7 +/- 5.36 kg) and 15 women (height = 160.9 +/- 5.4 cm, body mass = 55.9 +/- 5.36 kg). The force decrease for target forces of 75% and 100% MVC was marked until 60 sec. from the onset of grip and then decreased gradually. On the other hand, the target force of 50% MVC was maintained for about 60 sec. and then decreased markedly until 100 sec. Differences in the decreasing force among target force levels was observed until 60 sec., and there were no significant differences of the time to decay to 20%, 30%, and 40% MVC. Namely, the time and force exertion reaching an almost steady state were considered to be almost the same at any target force. A sex difference on a parameter was found after 60 sec. or a decreasing force after 40% MVC, and women held it longer or higher than the men. However, the tendency was smaller in the latter phase of the steady state.

Influence of differences of visual acuity in various visual field conditions on spectral characteristics of the center of pressure sway.

This study examined the influence of visual acuity and visual field on the spectral characteristics of the center of pressure during standing. 17 men and 20 women participated in High and Low visual acuity groups. Both groups underwent center of pressure measurements under three visual field conditions: No vision: subjects were given no visual information, Central vision: they were given only central visual field information, and Full vision: they were given full visual information. To assess the spectral characteristics of center of pressure, mean power frequency and frequency of maximal power were calculated from medial-lateral and anterior-posterior center of pressure directions. The Friedman test and Scheffé pairwise comparison tests showed that frequency of maximal power was higher in the No vision than in the Central and Full vision conditions in the High visual acuity group. In conclusion, people with high visual acuity are more susceptible to visual field conditions than those with low visual acuity. It is suggested that postural control characteristics differ with visual acuity or resolution in the central visual field.

Residual volume on land and when immersed in water: effect on percent body fat.

There is a large residual volume (RV) error when assessing percent body fat by means of hydrostatic weighing. It has generally been measured before hydrostatic weighing. However, an individual's maximal exhalations on land and in the water may not be identical. The aims of this study were to compare residual volumes and vital capacities on land and when immersed to the neck in water, and to examine the influence of the measurement error on percent body fat. The participants were 20 healthy Japanese males and 20 healthy Japanese females. To assess the influence of the RV error on percent body fat in both conditions and to evaluate the cross-validity of the prediction equation, another 20 males and 20 females were measured using hydrostatic weighing. Residual volume was measured on land and in the water using a nitrogen wash-out technique based on an open-circuit approach. In water, residual volume was measured with the participant sitting on a chair while the whole body, except the head, was submerged . The trial-to-trial reliabilities of residual volume in both conditions were very good (intraclass correlation coefficient > 0.98). Although residual volume measured under the two conditions did not agree completely, they showed a high correlation (males: 0.880; females: 0.853; P < 0.05). The limits of agreement for residual volumes in both conditions using Bland-Altman plots were -0.430 to 0.508 litres. This range was larger than the trial-to-trial error of residual volume on land (-0.260 to 0.304 litres). Moreover, the relationship between percent body fat computed using residual volume measured in both conditions was very good for both sexes (males: r = 0.902; females: r = 0.869, P < 0.0001), and the errors were approximately -6 to 4% (limits of agreement for percent body fat: -3.4 to 2.2% for males; -6.3 to 4.4% for females). We conclude that if these errors are of no importance, residual volume measured on land can be used when assessing body composition.