Masae Miyatani

VALIDITY OF BIOELECTRICAL IMPEDANCE AND ULTRASONOGRAPHIC METHODS FOR ESTIMATING THE MUSCLE VOLUME OF THE UPPER ARM

Abstract The present study aimed to investigate the validity of bioelectrical impedance and ultrasonographic methods for predicting the muscle volume of the upper arm. Bioelectrical impedance of the right upper arm and the thickness of elbow flexor and extensor muscles were measured from 26 healthy young adult men using a specially designed bioelectrical impedance data acquisition system and brightness-mode ultrasound apparatus, respectively. As reference data, the muscle volume (MVMRI) of the right upper arm was determined using a magnetic resonance imaging method. The impedance index was calculated as L2/Z, where L is the upper arm length and Z is the impedance of the shoulder to the elbow. The muscle volume (MVULT) was calculated as π·(d/2)2·L, where d is muscle thickness. L2/Z and MVULT were significantly correlated with MVMRI with correlation coefficients of 0.971 and 0.962, respectively. In these relationships, the standard errors of estimation were 44.2 cm3 (6.3%) for L2/Z and 50.7 cm3 (7.2%) for MVULT. There was no significant difference between the absolute errors of muscle volumes estimated by L2/Z and MVULT: 36.2 (4.8, SEM) cm3 for L2/Z versus 40.3 (5.8) cm3 for MVULT. The present results suggest that both bioelectrical impedance and ultrasonographic methods may be useful for predicting the muscle volume of the upper arm.

Pulse wave velocity for assessment of arterial stiffness among people with spinal cord injury: a pilot study.

Abstract Background/Objective: The most significant complication and leading cause of death for people with spinal cord injury (SCI) is coronary artery disease (CAD). It has been confirmed that aortic pulse wave velocity (PVW) is an emerging CAD predictor among able-bodied individuals. No prior study has described PWV values among people with SCI. The objective of this study was to compare aortic (the common carotid to femoral artery) PWV, arm (the brachial to radial artery) PVW, and leg (the femoral to posterior tibial artery) PVW in people with SCI (SCI group) to able-bodied controls (non-SCI group). Methods: Participants included 12 men with SCI and 9 non-SCI controls matched for age, sex, height, and weight. Participants with a history of CAD or current metabolic syndrome were excluded. Aortic, arm, and leg PVW was measured using the echo Doppler method. Results: Aortic PVW (mean ± SD) in the SCI group (1,274 ± 369 cm/s) was significantly higher (P < 0.05) than in the non-SCI group (948 ± 110 cm/s). There were no significant between-group differences in mean arm PVW (SCI: 1,152 ± 193 cm/s, non-SCI: 1,237 ± 193 cm/s) or mean leg PVW (SCI: 1,096 ± 1 73 cm/s, non-SCI: 994 ±178 cm/s) values. Conclusions: Aortic PVW was higher among the SCI group compared with the non-SCI group. The higher mean aortic PVW values among the SCI group compared with the non-SCI group indicated a higher risk of CAD among people with SCI in the absence of metabolic syndrome.

Age and cardiorespiratory fitness are associated with arterial stiffening and left ventricular remodelling

Arterial stiffening, hypertension and left ventricular (LV) remodelling are associated with increased risk of cardiovascular disease. Cardiorespiratory fitness is associated with cardiovascular function and reduced risk of cardiovascular disease. This cross-sectional study was carried out to determine the relationships between cardiorespiratory fitness, arterial stiffness, blood pressure (BP) and LV remodelling in women. On the basis of peak oxygen uptake, a total of 159 premenopausal (young) and postmenopausal (older) women were categorized into either low (unfit) or high (fit) cardiorespiratory fitness groups. The arterial stiffness and LV remodelling were measured by brachial-ankle pulse wave velocity (baPWV) and carotid augmentation index (AI) and LV relative wall thickness (RWT). Two-way analysis of variance indicated a significant interaction between age and cardiorespiratory fitness in baPWV, carotid AI, BP and RWT. In the older group, arterial stiffness (baPWV; 1401±231 vs 1250±125 cm s–1, P<0.01, AI; 32.9±9.9 vs 24.8±10.1%, P<0.01), systolic blood pressure (SBP) (130±22 vs 117±15 mm Hg, P<0.01) and RWT (0.47±0.08 vs 0.42±0.04, P<0.05) in fit women were lower than in unfit women. In older women, RWT was significantly related to baPWV (r=0.46, P<0.01), carotid AI (r=0.29, P<0.05), SBP (r=0.57, P<0.01) [Vdot ]2peak (r=−0.32, P<0.05). In young women, they were not significant correlations, except for a weak correlation between RWT and SBP (r=0.21, P<0.05). These results suggest that higher cardiorespiratory fitness is associated with lower arterial stiffness, BP and RWT in older women.

Cardiovascular response to functional electrical stimulation and dynamic tilt table therapy to improve orthostatic tolerance

Orthostatic hypotension is a common condition for individuals with stroke or spinal cord injury. The inability to regulate the central nervous system will result in pooling of blood in the lower extremities leading to orthostatic intolerance. This study compared the use of functional electrical stimulation (FES) and passive leg movements to improve orthostatic tolerance during head-up tilt. Four trial conditions were assessed during head-up tilt: (1) rest, (2) isometric FES of the hamstring, gastrocnemius and quadriceps muscle group, (3) passive mobilization using the Erigo dynamic tilt table; and (4) dynamic FES (combined 2 and 3). Ten healthy male subjects experienced 70 degrees head-up tilt for 15 min under each trial condition. Heart rate, blood pressure and abdominal echograms of the inferior vena cava were recorded for each trial. Passive mobilization and dynamic FES resulted in an increase in intravascular blood volume, while isometric FES only resulted in elevating heart rate. No significant differences in blood pressure were observed under each condition. We conclude that FES combined with passive stepping movements may be an effective modality to increase circulating blood volume and thereby tolerance to postural hypotension in healthy subjects.

Muscle mass and bone mineral indices: does the normalized bone mineral content differ with age?

Objective:To investigate the relationships between regional skeletal muscle mass (SM mass) and bone mineral indices and to examine whether bone mineral content (BMC) normalized to SM mass shows a similar decrease with age in young through old age.Subjects/Methods:One hundred and thirty-eight young and postmenopausal women aged 20–76 years participated in this study and were divided into three groups: 61 young women, 49 middle-aged postmenopausal women and 28 older postmenopausal women. Muscle thickness (MTH) was determined by ultrasound, and regional SM mass (arm, trunk and leg) was estimated based on nine sites of MTH. Whole-body and regional lean soft tissue mass (LSTM), bone mineral density (BMD) and BMC (whole body, arms, legs and lumbar spine) were measured using dual-energy X-ray absorptiometry.Results:Ultrasound spectroscopy indicated that SM mass is significantly correlated with site-matched regional bone mineral indices and these relationships correspond to LSTM. The BMC and BMD in older women were significantly lower than those in middle-aged women. When BMC was normalized to site-matched regional SM mass, BMC normalized to SM mass in arm and trunk region were significantly different with age; however, whole-body and leg BMC normalized to SM mass showed no significant difference between middle-aged and older postmenopausal women.Conclusions:The age-related differences in BMC were found to be independent of the ageing of SM mass in the arm and trunk region. However, differences in BMC measures of the leg and whole body were found to correspond to age-related decline of SM mass in postmenopausal women.

Variability of limb muscle size in young men

The purpose of this study was to determine the interindividual variability of the upper and lower limb muscle size in young men. Subjects were 655 Japanese men aged 18–39 years. They were sedentary and mildly to highly active individuals, including college athletes of various sports. Muscle thicknesses at each of the anterior and posterior portions of the upper arm, thigh, and lower leg were measured using B‐mode ultrasonography. Interindividual variability of muscle thickness was evaluated by coefficients of variation (CVs). The CVs of muscle thicknesses were found to be in the order of upper arm posterior (17.7%), thigh anterior (14.8%), thigh posterior (12.6%), upper arm anterior (12.2%), lower leg anterior (9.8%), and lower leg posterior (9.4%). The CVs were significantly different between each pair of measurement sites except for those of upper arm anterior‐thigh posterior and lower leg anterior‐posterior. These differences remain significant even when the muscle thicknesses were normalized to the segment length. The observed differences in the size variability can be interpreted as muscle‐related differences in hypertrophic responsiveness to resistance training. The muscle‐dependent size variability may be related to the differences in the fiber‐type composition and/or muscle usage in daily life among examined muscle groups. Am. J. Hum. Biol. 2010.

Required muscle mass for preventing lifestyle-related diseases in Japanese women.

BackgroundSince it is essential to maintain a high level of cardiorespiratory fitness to prevent life-style related disease, the Ministry of Health, Labour and Welfare of Japan in 2006 proposed to determine the maximal oxygen uptake (Vo2max: mL·kg-1·min-1) reference values to prevent life-style related diseases (LSRD). Since muscle mass is one of the determinant factors of Vo2max, it could be used as the reference parameter for preventing LSRD. The aim of this study was to determine and quantify the muscle mass required to maintain the Vo2max reference values in Japanese women.MethodsA total of 403 Japanese women aged 20–69 years were randomly allocated to either a validation or a cross-validation group. In the validation group, a multiple regression equation, which used a set of age and the percentage of muscle mass (%MM, percentage of appendicular lean soft tissue mass to body weight), as independent variables, was derived to estimate the Vo2max. After the equation was cross-validated, data from the two groups were pooled together to establish the final equation. The required %MM for each subject was recalculated by substituting the Vo2max reference values and her age in the final equation.ResultsThe mean value of required %MM was identified as (28.5 ± 0.35%). Thus, the present study proposed the required muscle mass (28.5% per body weight) in Japanese women to maintain the Vo2max reference values determined by the Japanese Ministry of Health Labour and Welfare.ConclusionThe estimated required %MM (28.5% per body weight) can be used as one of the reference parameters of fitness level in Japanese women.

Test-retest reliability of pulse wave velocity in individuals with chronic spinal cord injury

Abstract Background Pulse wave velocity (PWV), which reflects arterial stiffness, is an important predictor of future coronary artery disease. The test–retest reliability of PWV has not been investigated in people with spinal cord injury (SCI). Purpose To report the test–retest (day-to-day) reliability of PWV measurements among people with SCI, and to determine the smallest real difference (SRD) of PWV values. Participants Twenty men (n = 19) and a woman (n = 1) with SCI (C4-T10; AIS A-D; ≥1-year post-injury; 10 with paraplegia and 10 with tetraplegia; time post-injury: 11.8 ± 8.7 years; age: 43.0 ± 12.6 years). Methods On two occasions within a 2-week period, aortic PWV (between the common carotid and femoral artery), arm PWV (between the brachial and radial artery), and leg PWV (between femoral and posterior tibial artery) were assessed at the same time of day using Doppler flowmeters. Results No statistically significant differences were found between days 1 and 2 in aortic PWV (day 1: 941 ± 185 cm/seconds, day 2: 917 ± 160 cm/seconds, P = 0.257), leg PWV (day 1: 1088 ± 141 cm/seconds, day 2: 1122 ± 165 cm/seconds, P = 0.099) and arm PWV (day 1: 1283 ± 185 cm/seconds, day 2: 1358 ± 256 cm/seconds, P = 0.180). The aortic and leg PWVs had high test–retest reliability (intraclass correlation coefficient: ICC = 0.920 and 0.913, respectively; P < 0.001 for both) and arm PWV had moderate test–retest reliability (ICC = 0.598, P = 0.03). SRDs for each PWV were 104 cm/seconds (aortic PWV), 97 cm/seconds (leg PWV) and 143 cm/seconds (arm PWV). Conclusion The test–retest reliability of PWV assessment is high among patients with chronic SCI. Changes in aortic PWV values above 104 cm/seconds with repeated testing like represent true changes in health status.

Association between abnormal arterial stiffness and cardiovascular risk factors in people with chronic spinal cord injury.

Aims To describe the association between cardiovascular risk factors and abnormal arterial stiffness, defined by a carotid-femoral pulse wave velocity ≥ 10 m/s, in patients with chronic spinal cord injury (SCI). Methods Ninety consenting adults with chronic SCI (C1–T10 ASIA Impairment Scale A–D) participated in this cross-sectional study. The cardiovascular risk factors considered included age, sex, duration of injury, neurological level of injury (C1–T1, tetraplegia; T2–T12, paraplegia), age at injury, impairment scale category, supine resting systolic blood pressure, diastolic blood pressure, mean arterial pressure, heart rate, leisure time physical activity, treated hypertension, treated hyperlipidemia, diabetes, lipid profiles, fasting blood glucose, glycated hemoglobin, and C reactive protein. Logistic regression analysis was used to determine the association between abnormal arterial stiffness and dichotomized cardiovascular risk factors. Results Dichotomized variables significantly associated with increased arterial stiffness were: age ≥ 52 years (OR 22.1, CI 4.28–113.99); systolic blood pressure ≥ 130 mmHg (OR 11.76, CI 2.89–47.88); heart rate ≥ 62 bpm (OR 6.62, CI 1.33–33.03); and paraplegia (OR 4.26, CI 1.00–18.33). The area under the receiver operating characteristic curve for probability of arterial stiffness was 0.920 (95% CI 0.861–0.978, p < 0.001). Conclusions Age, resting systolic blood pressure, resting heart rate, and neurological level of injury can identify patients at high risk of elevated arterial stiffness in the population with chronic SCI.

Exercise Intensity during Treadmill Walking with Gait-Patterned FES among Patients with Incomplete Spinal Cord Injury: Case Series

Purpose. To determine the feasibility of increasing the cardiopulmonary exercise intensity during walking with gait-patterned functional electrical stimulation (GP-FES) among individuals with motor incomplete SCI. Methods. Two men with motor-incomplete SCI (Subjects A and B, age 45 and 50 years; Level of Injury: C4 and T10; AIS score: D and D, resp.) performed a three sequential four-minute continuous walking sessions [(1) regular gait (non-GP-FES-1); (2) gait with GP-FES (GP-FES); (3) regular gait (non-GP-FES-2)]. Oxygen consumption (Vo2) was measured continuously during trials. Results. Vo2 was higher during GP-FES (Subjects A and B; 14.5 and 19.1 mL/kg/min, resp.) as compared to regular gait (Non-GP-FES-1: Subjects A and B; 13.4 and 17.0: mL/kg/min, resp.; non-GP-FES-2: Subjects A and B; 13.1 and 17.5: mL/kg/min, resp.). Conclusion. The exercise intensity of GP-FES walking was higher than that of regular walking among individuals with motor incomplete SCI. Further investigations are required to determine the clinical relevance of the exercise.