Language：English   Publishing type：Research paper (scientific journal)  

The present study investigated factors related to trunk intramuscular adipose tissue (IntraMAT) content in younger and older men. Twenty-three healthy younger (20 to 29 years) and 20 healthy older men (63 to 79 years) participated in this study. The trunk IntraMAT content was measured using magnetic resonance imaging at the height of the 3rd lumbar vertebra. In addition to blood properties and physical performance, dietary intake was assessed by a self-administered diet history questionnaire. The dietary intake status was quantified using the nutrient adequacy score for the intake of 10 selected nutrients by summing the number of items that met the criteria of dietary reference intakes for Japanese individuals. The results obtained revealed that the trunk IntraMAT content was significantly higher in the older group than in the younger group (p < 0.05). In the younger group, the trunk IntraMAT content significantly correlated with systolic and diastolic blood pressure and HbA1c (rs = 0.443 to 0.464, p < 0.05). In the older group, significant and negative correlations were observed between the trunk IntraMAT content and 5-m usual walking speed, handgrip strength, and nutrient adequacy scores (rs = -0.485 to -0.713, p < 0.05). These results indicate that factors associated with the trunk IntraMAT content differed in an age dependent manner. In the younger group, the trunk IntraMAT content correlated with the metabolic status such as blood pressure and HbA1c. In the older group, physical performance and the dietary intake status negatively correlated with the trunk IntraMAT content.

DOI： 10.1016/j.exger.2022.111922

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.6890/IJGE.202207_16(3).0020

Web of Science

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Association of Exercise Epidemiology  

DOI： 10.24804/ree.2130

CiNii Research

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

We investigated the effect of physical activity on muscle tissue size and intramuscular adipose tissue (IntraMAT) content in the thigh muscle groups of younger and older men. Twenty younger and 20 older men participated in this study. The muscle tissue cross-sectional area (CSA) and the IntraMAT content in the quadriceps femoris (QF), hamstrings (HM), hip adductors (AD), and mid-thigh total were measured using magnetic resonance imaging. The physical activity time was measured using a triaxial accelerometer, and four levels of physical activity were determined depending on the metabolic equivalent of task (METs), including sedentary (≤ 1.5 METs), light intensity (≤ 2.9 METs), moderate intensity (3.0-5.9 METs), and vigorous intensity (≥ 6.0 METs). No significant correlation was observed between the physical activity parameters and muscle tissue CSA in both groups. The IntraMAT content of the three muscle groups (QF, AD, and HM) and the total thigh was inversely correlated with the time of moderate-intensity physical activity (rs =  - 0.625 to - 0.489, P < 0.05, for all comparisons) in the young group, but not in the older group. These results indicate that IntraMAT accumulation was associated with the amount of moderate-physical activity in younger men.

DOI： 10.1038/s41598-021-99126-x

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

PURPOSE: While brown adipose tissue (BAT) activity is known to be associated with both muscle and adipose tissue volumes, the association between BAT and muscle composition remains unclear, especially in adults. Therefore, the present study aimed to examine the association between BAT parameters (glucose uptake and fat-fraction) and muscle volumes and intramuscular adipose tissue contents among healthy young and middle-aged men. METHODS: BAT glucose uptake was determined using positron emission tomography with [18F]-2-deoxy-2-fluoro-D-glucose (18F-FDG) during cold exposure in 19 young and middle-aged men (36.3 ± 10.7 years). The fat-fraction of BAT was determined from volumes of interest set in cervical and supraclavicular adipose tissue depots using signal fat-fraction maps via magnetic resonance imaging (MRI). Muscle volumes and intramuscular adipose tissue contents of m. tibialis anterior and m. multifidus lumborum were measured using MRI. RESULTS: The fat-fraction of BAT was significantly associated with intramuscular adipose tissue content in m. tibialis anterior (n = 13, rs = 0.691, P = 0.009). A similar trend was also observed in m. multifidus lumborum (n = 19, rs = 0.454, P = 0.051). However, BAT glucose uptake was not associated with intramuscular adipose tissue contents in both muscles, nor were muscle volumes associated with the BAT glucose uptake and fat-fraction. CONCLUSION: The fat-fraction of BAT increases with skeletal muscle adiposity, especially in the lower leg, among healthy young and middle-aged men.

DOI： 10.1007/s00421-021-04816-z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.archger.2021.104463

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PURPOSE: Increased arterial stiffness predicts cardiovascular disease, which is associated with deteriorated pulmonary function and worsened chronic obstructive pulmonary disease. The present study examined whether arterial function was associated with pulmonary function in postmenopausal women. METHODS: This study evaluated 41 postmenopausal women (age range: 59-85 years). Arterial function was measured as central systolic blood pressure (cSBP), central pulse pressure (cPP), brachial systolic BP (bSBP), brachial diastolic BP (bDBP), brachial PP (bPP), brachial mean arterial pressure (bMAP) and the augmentation index (AIx). AIx was adjusted for a heart rate of 75 beats per minute (bpm) (AIx@75) and served as the index of arterial stiffness determined by the reflected wave at the central artery. Pulmonary function was measured as forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and the FEV1/FVC ratio. RESULTS: Univariate regression analysis demonstrated that cPP, bDBP and bPP were correlated with FVC and FEV1 (p<0.05, respectively), while AI@75 was correlated with FVC, FEV1 and FEV1/FVC ratio (p<0.01, respectively). A stepwise multivariate regression analysis revealed that bDBP was independently associated with FVC (p=0.032), while AI@75 was independently associated with FVC, FEV1 and FEV1/FVC ratio (p=0.001, p=0.003 and p=0.017, respectively). The FVC, FEV1 and FEV1/FVC ratio were lower in participants with a high AIx versus with a low AIx (p=0.0001, p=0.001 and p=0.044, respectively). CONCLUSION: These results suggest that increased AIx is associated with lower pulmonary function in postmenopausal women.

DOI： 10.1016/j.hlc.2021.08.005

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Online exercise is undoubtedly useful and important; however, chronic adaptations to online exercise, particularly strength gain, muscle hypertrophy, and cardiovascular parameters, remain unclear. We investigated the effect of online exercise training using Zoom on fitness parameters compared with the same exercises supervised directly. In the present study, 34 subjects (age: 42.9±14.4 years) were included. Twenty-three subjects performed eight weeks of body mass-based exercise training online using Zoom, and eleven subjects performed the same exercise supervised directly as the control group. The subjects performed low-load resistance exercises twice a week for 8 weeks for a total of 16 sessions. The sessions included 9 exercises: leg raises, squats, rear raises, shoulder presses, rowing, dips, lunges, Romanian dead lifts, and push-ups. Chair-stand, push-up, and sit-and-reach tests were performed on all subjects. Overall, the home exercise program effectively increased strength and muscle mass and decreased blood pressure and arterial stiffness, but there were no differences between the groups. Changes in chair-stand and sit-and-reach test results were higher in the control group than in the online group. Our results show that there is a similar training response to body mass-based training in both groups, even with virtual experiences using Zoom.

DOI： 10.1055/a-1582-2874

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This study examined the validity of extended-field-of-view (EFOV) ultrasound imaging for evaluating the quantity (cross-sectional area [CSA]) and quality (accumulation of intramuscular fat) of trunk skeletal muscles (rectus abdominis, abdominal oblique and erector spinae) using magnetic resonance imaging (MRI) as a reference. Thirty healthy young men participated in this study. Cross-sectional images of the trunk at the height of the third lumbar vertebra were acquired and compared by EFOV ultrasound imaging and MRI. No significant differences were observed in CSAs between the two methods (0.74 ≤ R2 ≤ 0.85). Echo intensities significantly correlated with MRI-derived accumulation of intramuscular fat in each skeletal muscle group. However, the correlation coefficients were relatively low (0.37 ≤ r ≤0.47; p < 0.05). These results indicate that EFOV ultrasound imaging is a reliable method for assessing trunk skeletal muscle CSA. Further research is warranted to find the optimal ultrasound setting for evaluating muscle quality.

DOI： 10.1016/j.ultrasmedbio.2020.11.006

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The present study aims to investigate the effects of 8 weeks of bed rest, with or without resistance exercise intervention, on the volumes of muscle tissue and the intramuscular, intermuscular, and subcutaneous adipose tissues of the thigh. Twenty men were included, who were randomly assigned in three groups: resistance exercises group (RE group), resistance exercises with whole-body vibration group (VRE group), and nonexercise control group (CTR group). The RE and VRE groups performed resistance exercises during 8 weeks of bed rest (3 days per week). Additionally, consecutive axial magnetic resonance images were obtained before and after the bed rest. Using these images, the volumes of the muscle tissue and the intramuscular adipose tissue, intermuscular adipose tissue, and subcutaneous adipose tissue of the thigh were evaluated. No significant time-by-group interaction was observed the volumes of the muscle tissue and the intramuscular adipose tissue, intermuscular adipose tissue, and subcutaneous adipose tissue between the RE and VRE groups. Furthermore, the RE and VRE groups were pooled as the resistance exercise intervention group (TR group), wherein their thigh muscle tissue volume was observed to be maintained after the bed rest. However, that of the CTR group significantly decreased. Regarding the thigh intramuscular adipose tissue and intermuscular adipose tissue volumes, no significant difference was observed among the CTR and TR groups. Although subcutaneous adipose tissue volume in the CTR group significantly increased after the bed rest, no changes were observed in that of the TR group. Therefore, the results of the present study suggested that within the 8 weeks of bed rest, adipose tissue adaptation differs depending on the location.

DOI： 10.14814/phy2.14560

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Although age-related deterioration of skeletal muscle strength and size has gained much attention, the age-related increase in adipose tissue within skeletal muscle has not received the same level of attention, especially in older individuals. It is not well known how echo intensity (EI), which is an index of intramuscular adipose tissue (IntraMAT) and connective tissue, is associated with demographic, functional, and morphological characteristics in older individuals. The purpose of this study was to assess the relationships between the EI of the quadriceps femoris (QF) and demographic, functional, and morphological characteristics in pre-old (65-74 years) and old (75 years or older) individuals. One hundred thirty-two men and women aged 65 to 74 years (45 men and 51 women; Pre-old group) or 75 years and older (17 men and 19 women, Old group) participated in this study. The EI and muscle thickness (MT) of the QF were measured using B-mode ultrasonography. Sit-up, supine-up, sit-to-stand, 5-m maximal walk, and 6-min walk tests were performed. The EI of the QF in the Old group (73.1 ± 9.0 a.u.) was significantly higher than that in the Pre-old group (67.6 ± 9.1 a.u.). The EI of the QF was significantly correlated with the MT of the QF in both the Pre-old (r = -0.542, P < 0.01) and Old (r = -0.622, P < 0.01) groups. Stepwise multiple linear regression analysis with the EI of the QF as a dependent variable showed that the MT of the QF was a significant variable in both the Pre-old and Old groups. These results suggest that MT is an extremely valuable factor for explaining the EI of the QF regardless of age group. Exercise interventions are recommended to decrease the risks of metabolic impairment by increasing muscle size and decreasing IntraMAT in individuals aged 65 years or older.

DOI： 10.1016/j.exger.2020.111015

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Muscle quality is well-known to decrease with aging and is a risk factor for metabolic abnormalities. However, there is a lack of information on race-associated differences in muscle quality and other neuromuscular features related to functional performance. This study aimed to compare muscle quality, function, and morphological characteristics in Japanese and Brazilian older individuals. Eighty-four participants aged 65-87 years were enrolled in the study (42 Japanese: 23 men, 19 women, mean age 70.4 years; 42 Brazilians: 23 men, 19 women, mean age 70.8 years). Echo intensity (EI) and muscle thickness (MT) of the quadriceps femoris were measured using B-mode ultrasonography. A stepwise multiple linear regression analysis with EI as a dependent variable revealed that MT was a significant variable for Japanese participants (R2 = 0.424, P = 0.001), while MT and subcutaneous adipose tissue (SCAT) thickness were significant variables for Brazilian participants (R2 = 0.490, P = 0.001). A second stepwise multiple linear regression analysis was performed after excluding MT and SCAT thickness from the independent variables. Sex and age for Japanese participants (R2 = 0.381, P = 0.001) and lean body mass and body mass index for Brazilian participants (R2 = 0.385, P = 0.001) were identified as significant independent variables. The present results suggest that MT is closely correlated with muscle quality in Japanese and Brazilian older individuals. Increases in muscle size may induce decreases in intramuscular adipose tissue and/or connective tissues, which are beneficial for reducing the risks of metabolic impairments in Japanese and Brazilian older individuals.

DOI： 10.1371/journal.pone.0243589

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PURPOSE: The purpose of this study was to compare intramuscular adipose tissue content determined by two-point Dixon imaging and T1-weighted imaging, calculated using thresholding techniques. METHODS: In total, 19 nonobese younger adults (26.2 ± 4.9 years) and 13 older adults (72.2 ± 6.0 years) were recruited. Axial images of the mid-thigh were taken using T1-weighted and two-point Dixon sequences with a 3.0 T whole-body magnetic resonance device and used to measure intramuscular adipose tissue content of the vastus lateralis, adductor magnus, and long head of the biceps femoris. RESULTS: There was no significant difference in intramuscular adipose tissue content between T1-weighted and two-point Dixon imaging for the vastus lateralis (11.0 ± 4.4% and 12.2 ± 2.4%); however, intramuscular adipose tissue content determined by T1-weighted imaging was significantly higher than that of two-point Dixon imaging for the other muscles. Bland-Altman analysis showed a proportional bias for intramuscular adipose tissue calculations in all three muscles. CONCLUSION: The validity of intramuscular adipose tissue content measurements between T1-weighted and two-point Dixon imaging is muscle-specific. This study showed discrepancies of intramuscular adipose tissue content between T1-weighted and two-point Dixon imaging. ADVANCES IN KNOWLEDGE: This study's results suggest that care should be taken when selecting an imaging modality for intramuscular adipose tissue, especially for patients who would be suspected to have higher intramuscular adipose tissue values.

DOI： 10.1371/journal.pone.0231156

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SERDI  

ackground: The association of physical activity (PA) intensities and duration spent in those activities with different walking tasks remains unclear. Objectives: To examine the association between the duration of PA intensities and three walking speeds (usual walking speed, maximal walking speed and zig-zag walking speed). Design: Multiple linear regression analysis was used to estimate the association of age, BMI, maximum knee extension strength, light PA, moderate PA and vigorous PA with walking speeds. Setting: University lab. Participants: Eighty-six older women (67 ± 7 years). Measurements: PA was measured for 30 consecutive days using the Lifecorder-EX accelerometer. Exercise intensity was categorized as light (levels 1-3), moderate (levels 4-6) and vigorous (levels 7-9) based on the manufacturer algorithms. Usual straight walking speed (20 m), maximal straight walking speed (20 m) and zig-zag walking speed tests (10 m) were performed by each participant. Results: For the usual straight walking speed model (R2 = 0.296, SEE = 0.15 m/s), the significant predictors were BMI, knee extension strength, light PA and vigorous PA. For the maximal straight walking speed model (R2 = 0.326, SEE = 0.20 m/s), only age was a significant predictor. For the zig-zag walking speed model (R2=0.417, SEE = 0.14 m/s), age and maximum knee strength were significant predictors in the model. Conclusions: Overall, the results of this study suggest that vigorous PA and maximal knee extension strength are two important factors that are associated with different walking speeds in older women.

DOI： 10.14283/jfa.2019.26

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We investigated the effect of resistance training and fish protein intake on the motor unit firing pattern and motor function in elderly. Fifty healthy elderly males and females (69.2 ± 4.7 years) underwent 6 weeks of intervention. We applied the leg-press exercise as resistance training and fish protein including Alaska pollack protein (APP) as nutritional supplementation. Subjects were divided into four groups: fish protein intake without resistance training (APP-CN, n = 13), placebo intake without resistance training (PLA-CN, n = 12), fish protein intake with resistance training (APP-RT, n = 12), and placebo intake with resistance training (PLA-RT, n = 13). Motor unit firing rates were calculated from multi-channel surface electromyography by the Convolution Kernel. For the chair-stand test, while significant increases were observed at 6 weeks compared with 0 week in all groups (p < 0.05), significant increases from 0 to 3 weeks and 6 weeks were observed in APP-RT (18.2 ± 1.9 at 0 week to 19.8 ± 2.2 at 3 weeks and 21.2 ± 1.9 at 6 weeks) (p < 0.05). Increase and/or decrease in the motor unit firing rate were mainly noted within motor units with a low-recruitment threshold in APP-RT and PLA-RT at 3 and 6 weeks (12.3 pps at 0 week to 13.6 pps at 3 weeks and 12.1 pps at 6 weeks for APP-RT and 12.9 pps at 0 week to 13.9 pps at 3 weeks and 14.1 pps at 6 weeks for PLA-RT at 50% of MVC) (p < 0.05), but not in APP-CN or PLA-CN (p > 0.05). Time courses of changes in the results of the chair-stand test and motor unit firing rate were different between APP-RT and PLA-RT. These findings suggest that, in the elderly, the effect of resistance training on the motor unit firing rate is observed in motor units with a low-recruitment threshold, and additional fish protein intake modifies these adaptations in motor unit firing patterns and the motor function following resistance training.

DOI： 10.3389/fphys.2018.01733

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Background: Older individuals have been shown to present muscle atrophy in conjunction with increased fat fraction in some muscles. The proportion of fat and connective tissue within the skeletal muscle can be estimated from axial B-mode ultrasound images using echo intensity (EI). EI was used to calculate the index of muscle quality. Walking, home-based weight-bearing resistance training, and its combinations are considered simple, easy, and practical exercise interventions for older adults. The purpose of this study was to quantify the effects of walking and walking with home-based resistance training on muscle quality of older individuals. Methods: Thirty-one participants performed walking training only (W-group; 72 ± 5 years) and 33 participants performed walking and home-based resistance training (WR-group; 73 ± 6 years). This study was a non-randomized controlled trial with no control group. All participants were instructed to walk 2 or 3 sets per week for 10 weeks (one set: 30-min continuous walking). In addition, the WR-group performed home-based weight-bearing resistance training. EI was measured as a muscle quality index using axial B-mode ultrasound images of the rectus femoris and vastus lateralis of the mid-thigh. We further averaged these parameters to obtain the EI of the quadriceps femoris (QF). Participants further performed five functional tests: sit-ups, supine up, sit-to-stand, 5-m maximal walk, and 6-min walk. Results: QF EI was significantly decreased in both groups after training (W-group 69.9 ± 7.4 a.u. to 61.7 ± 7.0 a.u., WR-group 64.0 ± 9.5 a.u. to 51.1 ± 10.0 a.u.; P < 0.05), suggesting improved muscle quality. QF EI was further decreased in the WR-group compared with the W-group. The sit-up test in both groups and the sit-to-stand and 5-m maximal walk tests in the W-group were significantly improved after training. Conclusion: These results suggest that training-induced stimulation is associated with a decrease in EI in some thigh regions. Furthermore, the addition of home-based resistance training to walking would be effective for a greater reduction of EI.

DOI： 10.1186/s11556-018-0201-2

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Background: Since age-related muscle strength loss cannot be explained solely by muscle atrophy, other determinants would also contribute to muscle strength in elderly. The present study aimed to clarify contribution of neuromuscular activation pattern to muscle strength in elderly group. From 88 elderlies (age: 61~ 83 years), multi-channel surface electromyography (EMG) of the vastus lateralis muscle was recorded with two-dimensional 64 electrodes during isometric submaximal ramp-up knee extension to assess neuromuscular activation pattern. Correlation analysis and stepwise regression analysis were performed between muscle strength and the parameters for signal amplitude and spatial distribution pattern, i.e., root mean square (RMS), correlation coefficient, and modified entropy of multi-channel surface EMG. Results: There was a significant correlation between muscle strength and RMS (r = 0.361, p = 0.001) in the elderly. Muscle thickness (r = 0.519, p < 0.001), RMS (r = 0.288, p = 0.001), and normalized RMS (r = 0.177, p = 0.047) were selected as major determinants of muscle strength in stepwise regression analysis (r = 0.664 in the selected model). Conclusion: These results suggest that inter-individual difference in muscle strength in elderly can be partly explained by surface EMG amplitude. We concluded that neuromuscular activation pattern is also major determinants of muscle strength on elderly in addition to indicator of muscle volume.

DOI： 10.1186/s11556-018-0192-z

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Ectopic adiposity has gained considerable attention because of its tight association with metabolic and cardiovascular health in persons with spinal cord injury (SCI). Ectopic adiposity is characterized by the storage of adipose tissue in non-subcutaneous sites. Magnetic resonance imaging (MRI) has proven to be an effective tool in quantifying ectopic adiposity and provides the opportunity to measure different adipose depots including intermuscular adipose tissue (IMAT) and intramuscular adipose tissue (IntraMAT) or intramuscular fat (IMF). It is highly important to distinguish and clearly define these compartments, because controversy still exists on how to accurately quantify these adipose depots. Investigators have relied on separating muscle from fat pixels based on their characteristic signal intensities. A common technique is plotting a threshold histogram that clearly separates between muscle and fat peaks. The cut-offs to separate between muscle and fat peaks are still not clearly defined and different cut-offs have been identified. This review will outline and compare the Midpoint and Otsu techniques, two methods used to determine the threshold between muscle and fat pixels on T1 weighted MRI. The process of water/fat segmentation using the Dixon method will also be outlined. We are hopeful that this review will trigger more research towards accurately quantifying ectopic adiposity due to its high relevance to cardiometabolic health after SCI.

DOI： 10.4103/1673-5374.221170

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PURPOSE: This study aimed to examine the reliability of extended field-of-view (EFOV) ultrasound imaging to evaluate the cross-sectional area (CSA) and echo intensity of abdominal skeletal muscles. METHODS: Twenty-seven healthy young males (age 18.6 ± 1.0 years, body mass index 20.9 ± 2.8 kg/m2, waist circumference 75.0 ± 7.9 cm, body fat 16.6 ± 5.9%) visited the laboratory on 2 days. EFOV ultrasound images of the rectus abdominis, abdominal oblique, and erector spinae muscles were acquired at the height of the third lumbar vertebra with the subject lying on a bed. We then analyzed CSA and echo intensity using ImageJ software and calculated intra-class correlation coefficients (ICC) and the standard error of measurement (SEM). RESULTS: No significant differences (p = 0.149-0.679) were observed in CSA or echo intensity values for each skeletal muscle between days. ICC and SEM values in CSA for each skeletal muscle ranged between 0.944 and 0.958 and 4.9% and 7.3%, respectively. The corresponding values for echo intensity were 0.851-0.945 for ICC and 5.3-9.7% for SEM. CONCLUSIONS: The present results indicate that EFOV ultrasound imaging has high repeatability for measuring CSA and echo intensity of abdominal skeletal muscle groups in healthy college-aged males.

DOI： 10.1007/s00421-017-3713-y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.archger.2017.01.014

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Age-related changes in motor unit activation properties remain unclear for locomotor muscles such as quadriceps muscles, although these muscles are preferentially atrophied with aging and play important roles in daily living movements. The present study investigated and compared detailed motor unit firing characteristics for the vastus lateralis muscle during isometric contraction at low to moderate force levels in the elderly and young. Fourteen healthy elderly men and 15 healthy young men performed isometric ramp-up contraction to 70 % of the maximal voluntary contractions (MVC) during knee extension. Multichannel surface electromyograms were recorded from the vastus lateralis muscle using a two-dimensional grid of 64 electrodes and decomposed with the convolution kernel compensation technique to extract individual motor units. Motor unit firing rates in the young were significantly higher (~+29.7 %) than in the elderly (p < 0.05). There were significant differences in firing rates among motor units with different recruitment thresholds at each force level in the young (p < 0.05) but not in the elderly (p > 0.05). Firing rates at 60 % of the MVC force level for the motor units recruited at <20 % of MVC were significantly correlated with MVC force in the elderly (r = 0.885, p < 0.0001) but not in the young (r = 0.127, p > 0.05). These results suggest that the motor unit firing rate in the vastus lateralis muscle is affected by aging and muscle strength in the elderly and/or age-related strength loss is related to motor unit firing/recruitment properties.

DOI： 10.1007/s11357-016-9915-0

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To investigate the relationships between site-specific muscle loss in the thigh, muscle quality and zigzag walking performance, 40 men and 41 women aged 65-79 years had muscle thickness (MTH) measured by ultrasound at nine sites on the anterior and posterior aspects of the body. Skeletal muscle mass (SM) was estimated from an ultrasound-derived prediction equation. Site-specific thigh sarcopenia was calculated using ultrasound-measured MTH at the anterior/posterior aspects of the thigh (AP-MTH ratio). Zigzag walking time (ZWT) and maximum isometric knee extension (KE) and flexion (KF) torques were measured. Muscle quality (torque/thigh SM) and knee joint strength index (torque/body mass) were calculated. There were no significant correlations between SM index and ZWT. However, AP-MTH ratio was inversely correlated (P < 0.05) to ZWT in men (r = -0.335) and women (r = -0.309). ZWT was also inversely correlated (P < 0.05) to KE-strength index in both sexes (men, r = -0.328; women, r = -0.372). Similarly, ZWT was correlated to KF-strength index (r = -0.497) and muscle quality (r = -0.322) in women, but not in men. After adjusting for age, height and body mass, AP-MTH ratio was inversely correlated to ZWT in men (r = -0.325) and tended to be correlated to ZWT in women (r = -0.263). Zigzag walking performance may be associated with site-specific thigh sarcopenia in older men and women.

DOI： 10.1556/APhysiol.101.2014.006

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AIM: Recently, data have questioned the homogenous model of sarcopenia, and suggest that the loss of muscle mass could occur in a site-specific manner. It is unclear, however, whether a muscle strength ratio can be used to assess age-related, site-specific muscle loss. The purpose of the present study was to investigate the relationship between the age-related loss of thigh muscle, muscle function and gait performance. METHODS: A total of 55 men aged 18-79 years had muscle thickness (MTH) measured by ultrasound at three sites on the anterior (30% and 50% of thigh length) and posterior (70% of thigh length) aspects of the thigh. MTH ratios were calculated to assess the site-specific muscle loss (anterior 30% : posterior 70% MTH [A30:P70] and anterior 50% :posterior 70% MTH [A50:P70]). Walking performance, maximum isometric knee extension/flexion, toe-grasping and handgrip strength were measured. RESULTS: Age was inversely correlated with the ratios of A30:P70 (r=-0.332) and A50:P70 (r=-0.466). There were no significant correlations between the A30:P70 and A50:P70 ratios, and height and bodyweight. The A30 : P70 and A50 : P70 ratios were also not correlated with maximal walking speed. However, the A50:P70 ratio was significantly correlated with zig-zag walking (r=-0.350) and handgrip strength (r=0.334). In addition, these MTH ratios were also correlated with knee extension (r=0.309 and r=0.405), flexion (r=0.306 and r=0.412) and toe-grasping strength (r=0.265 and r=0.336). After adjusting for physical activity, the MTH ratios were still not correlated with ratio of muscle strength. CONCLUSION: Strength ratios did not correlate with MTH ratios. Our cross-sectional analysis suggests that age-related site-specific muscle loss could assess the decrease in absolute muscular strength, but not the ratio of muscle strength.

DOI： 10.1111/ggi.12179

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Very little information is available concerning the relationship between handgrip strength and muscle size in the upper and lower extremities, especially the forearm muscle itself. To investigate the relationships among ultrasound-measured forearm muscle thickness from the radius and ulna bone interface with handgrip strength, knee extension strength, walking speed and absolute/relative total skeletal muscle mass (TMM), 32 Japanese men and 21 Japanese women ages 70-83 years had muscle thickness (MT) measured by ultrasound. In the forearm, two MTs (forearm-radius and forearm-ulna MT) were measured. TMM was estimated from an ultrasound-derived prediction equation. Handgrip-strength was significantly correlated with forearm-ulna MT in both men and women. There were no significant correlations between forearm MT and walking speed in either sex. In men, both forearm-radius and forearm-ulna MT were significantly correlated with TMM and TMM index. In women, a significant correlation was only observed between forearm-ulna MT and TMM index. Our results suggest that forearm-ulna MT may be a useful parameter for evaluating handgrip strength and TMM index in older Japanese men and women.

DOI： 10.1016/j.ultrasmedbio.2014.05.003

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AIM: To test the hypothesis that static balance is associated with site-specific loss of muscle mass in older adults. METHODS: A total of 57 active women aged 52-83 years had their muscle thickness (MTH) measured by ultrasound at four sites on the anterior and posterior aspects of their upper- and lower-leg. MTH ratios were calculated to assess the site-specific muscle loss. One-leg standing balance with eyes open and maximum isometric knee extension/flexion strength were measured. Daytime physical activity was also measured. The participants were separated into three groups based on achieved timed one-leg balance test: less than 60 s (n = 19, G1), 60-120 s (n = 12, G2) and over 120 s (n = 26, G3). RESULTS: Age was inversely correlated to the upper-leg (A50 : P70) MTH ratios (r = -0.389, P < 0.001), but not lower-leg ratio (r = 0.047), thus site-specific muscle loss was observed in the upper-leg. Total muscle mass was similar among the groups. A50 : P70 MTH ratio and absolute and relative knee flexion strength were lower in G1 than in G3. Step counts and durations of moderate and vigorous exercise were lower in G1 and G2 than in G3. There were significant correlations between one-leg balance and A50 : P70 MTH ratio (r = 0.271, P < 0.05) and physical activity level (r = 0.357-0.481, P < 0.01). After adjusting for step count, one-leg balance was only correlated significantly with duration of vigorous exercise (r = 0.319, P < 0.05). CONCLUSION: Higher physical activity could have more impact on balance regulation, as the influence of site-specific muscle loss was weak in active women.

DOI： 10.1111/ggi.12112

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND AND AIMS: It is unknown if the site-specific muscle loss of ageing muscle is associated with accelerometer-determined daily step count and/or intensity of physical activity. The purpose of this study was to examine the relationships between accelerometer- determined physical activity and lower body muscle size in women. METHODS: Forty-eight women aged 52 to 76 years had their muscle thickness (MTH) measured by B-mode ultrasound at seven sites on the anterior and posterior aspects of their upper- and lower-leg. Daytime physical activity was measured using an accelerometer on 30 consecutive days and the total duration of each level of exercise intensity (light-PA, moderate-PA and vigorous-PA), average step count, and physical activity-related energy expenditure were calculated. RESULTS: Age was inversely correlated with anterior 30% upper-leg MTH (r=-0.296, p<0.05), but not with other measured MTH sites. Light-PA was not significantly (p>0.05) correlated with measured lower body MTH. However, moderate-PA was correlated (p<0.05) with lower-leg MTH, while vigorous-PA was correlated (p<0.05) with lower-leg and anterior 30% upper- leg MTH. Following adjustment for confounding factors, the anterior and posterior lower-leg MTH was positively correlated (p<0.05) with duration of moderate- PA and vigorous-PA, as well as average step count. CONCLUSIONS: Thus daily moderate and vigorous physical activity was associated with higher muscle mass in the lower leg, but not in the upper-leg muscle, suggesting that the site-specific upper-leg muscle loss may not be prevented or attenuated by daily physical activity.

DOI： 10.3275/8758

PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.archger.2012.06.009

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

CONTEXT: Previous studies investigated the relationship between ultrasound-derived anatomical muscle thickness (MTH) and individual muscle cross-sectional area (CSA) and muscle volume in several limb and trunk muscles; however, the adductor muscle that contributes to hip adduction and pelvic stabilization, as well as balance ability, has not been studied. OBJECTIVE: To examine the relationship between MTH of the lower, middle, and upper thigh measured by B-mode ultrasound and the muscle CSA and volume of adductor muscle obtained by magnetic resonance imaging (MRI) to confirm the possibility of predicting adductor muscle CSA/volume using ultrasound-derived MTH. SETTING: University research laboratory. SUBJECTS: 10 men and 10 women (20-41 y old) volunteered to participate in this study. MAIN OUTCOME MEASURES: A series of continuous muscle CSAs along the thigh were measured by MRI scans (1.5-T scanner, GE Signa). In each slice, the anatomical CSA of the adductors was analyzed, and the muscle volume was calculated by multiplying muscle CSA by slice thickness. Thigh MTH was measured by B-mode ultrasound (Aloka SSD-500) at 5 sites (anterior 30%, 50%, and 70% and posterior 50% and 70% of thigh length). RESULTS: A strong correlation was observed between anterior 30% MTH and 30% adductor CSA in men (r = .845, P < .002) and women (r = .952, P < .001) and in both groups combined (r = .922, P < .001). Anterior 30% MTH was also strongly correlated to adductor muscle volume when combined with thigh length (n = 20, r = .949, P < .001). However, there were moderate or nonsignificant correlations between anterior and posterior 50% and 70% MTH and adductor muscle CSA/volume. CONCLUSIONS: The results suggest that MTH in the upper portion of anterior thigh best reflects adductor muscle CSA or muscle volume, while the lower portions of the anterior and posterior sites are least likely to predict adductor muscle size.

PubMed

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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The purpose of this study was to compare the component characteristics of thigh muscle volume in Japanese young and older men. The subjects in both young (YM, n = 15) and older (OM, n = 13) men were physically active (performed aerobic-type exercise 1-3 times per week), but none of the subjects had regularly participated in resistance training for a minimum of 3 years prior to the study. Contiguous transverse magnetic resonance imaging (1.5-T scanner) images were obtained from the thigh, and total and individual (quadriceps, hamstrings and adductors) muscle volumes were calculated by multiplying the muscle cross-sectional area (CSA) by slice thickness and the total number of slices. Muscle length and average muscle CSA (muscle volume divided by muscle length) were determined for each muscle. Maximum voluntary isometric (MVC) knee extension and flexion strength were measured, and muscle quality was defined as MVC per unit average muscle CSA (MVC/CSA). Quadriceps muscle volume and average CSA were, respectively, 20% and 16% lower (P < 0.05) in the OM than in the YM, while hamstrings and adductors muscle volumes and average CSA were similar in both groups. Knee extension and flexion MVC were lower (P < 0.05) in the OM than in the YM. Knee extensor MVC/CSA was similar in the two groups, while knee flexor MVC/CSA was lower (P < 0.05) in the OM than in the YM. Our results suggest that age-related thigh muscle volume loss is muscle specific, in that greater quadriceps muscle loss was found in the older group.

DOI： 10.1111/j.1475-097X.2011.01057.x

PubMed

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