Publications by authors named "Noriaki Ichihashi"

183 Publications

Prevalence and physical characteristics of locomotive syndrome stages as classified by the new criteria 2020 in older Japanese people: results from the Nagahama study.

BMC Geriatr 2021 09 9;21(1):489. Epub 2021 Sep 9.

Human Health Sciences, Graduate School of Medicine, Kyoto University, 53, Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.

Background: The Japanese Orthopaedic Association (JOA) proposed the concept of locomotive syndrome (LS) in 2007 for detecting high-risk individuals with mobility limitation. In 2020, the JOA revised the clinical decision limits and introduced LS stage 3, which carried the highest-risk for LS compared to the conventional stages, 1 and 2. The purpose of this study was to characterize the prevalence, comorbidities, and physical characteristics in each LS stage, as per the LS criteria 2020.

Methods: We analyzed 2077 participants (64.9% women; mean age, 68.3 ± 5.4 years) from the Nagahama Study aged ≥60 years. Participants were classified into 4 groups, non-LS and LS stages 1, 2, and 3, based on a 25-question Geriatric Locomotive Function Scale. The prevalence of comorbidities (sarcopenia, osteoporosis, diabetes mellitus, low back pain [LBP], and knee pain) were investigated. Physical characteristics were measured based on the physical performance tests including gait speed, five-times chair-stand, single-leg stand, and short physical performance battery; muscle strength tests including grip, knee extension, hip flexion, and abduction; and body-composition analysis including muscle quantity and quality. Differences in the prevalence of comorbidities between LS stages were tested using the chi-square test. The general linear model was performed for univariate and multivariate analyses with post-hoc test to compare the differences in physical characteristics among the LS stages.

Results: The prevalence of LS increased with age, and the mean prevalence of LS stages 1, 2, and 3 were 24.4, 5.5, and 6.5%, respectively. The prevalence of comorbidities, including sarcopenia, osteoporosis, LBP, and knee pain, increased with worsening LS stage. Physical performance tests were significantly different between LS stages 2 and 3; and muscle strength differed significantly between LS stages 1 and 2. Additionally, in terms of body composition analysis, muscle quality but not muscle quantity showed significant differences among all the LS stages.

Conclusions: Our findings suggest that muscle strengthening and dynamic training, including balance training in LS stage 1 and 2, respectively, were needed for preventing the LS progression. Individuals with LS stage 3 should perform dynamic training and muscle strengthening exercises while receiving treatment for comorbidities.
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http://dx.doi.org/10.1186/s12877-021-02440-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8428127PMC
September 2021

Differences in lower limb muscle strength and balance ability between sarcopenia stages depend on sex in community-dwelling older adults.

Aging Clin Exp Res 2021 Aug 20. Epub 2021 Aug 20.

Human Health Sciences, Kyoto University Graduate School of Medicine, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.

Aim: This study aimed to compare motor function between sarcopenia stages with respect to sex in community-dwelling older adults.

Methods: The participants, comprising 2107 community-dwelling older adults (738 men and 1369 women), were classified into 4 groups and the groups were operationally defined-normal, low muscle mass, low physical function, and sarcopenia groups. Lower limb muscle strength and balance ability were assessed for evaluating motor function. To compare motor function between sarcopenia stages, an analysis of covariance adjusted for age and body mass index was performed.

Results: Lower limb muscle strengths were significantly lower not only in the sarcopenia group but also in the low muscle mass and low physical function groups than that in the normal group in both men and women. Low hip abductor muscle strength was observed in the low physical function group compared to the low muscle mass group in women, but not in men. Timed Up and Go test results in the sarcopenia and low function groups was lower than in the normal and low muscle mass groups for men and women. One-leg standing in the low physical function group was lower than that in the normal group, only for women.

Conclusions: Reduced motor function was observed not only in older people with sarcopenia but also in older people with only low muscle mass or low physical function, and the decline in lower limb muscle strength and balance ability in the low function group were greater in older women than in older men.
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http://dx.doi.org/10.1007/s40520-021-01952-6DOI Listing
August 2021

Weak hip flexor strength predicts progression of functional capacity decline due to locomotor system dysfunction in community-dwelling older adults: A longitudinal cohort study.

Arch Gerontol Geriatr 2021 Aug 2;97:104499. Epub 2021 Aug 2.

Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.

Purpose: It is critical to determine the risk factors for activities of daily living (ADL) disability caused by locomotor dysfunction. However, no longitudinal study has investigated the association between disability due to locomotive dysfunction and multidimensional factors. Therefore, we investigated the relationship between the progression of functional capacity decline due to locomotive dysfunction and multiple physical functions among older adults in a longitudinal study.

Methods: The participants comprised of 433 community-dwelling older adults. Physical function was assessed at baseline, which included handgrip strength, maximal isometric strength of hip flexion, hip extension, hip abduction, knee extension, toe flexion (index for muscle strength), the 5-time chair-stand test (index for muscle power), the one-legged stance and timed ''Up & Go'' tests (index for balance function), the 30-s stair test (index for muscle endurance), and range of motion (ROM) (an index of joint condition). Functional capacity decline due to locomotive dysfunction was assessed using the 25-question Geriatric Locomotive Function Scale (GLFS-25) before and after a 12-month period. Based on changes in the GLFS-25 score compared with baseline, the non-decline and decline groups were operationally defined. Logistic regression analyses with the groups as the dependent variable and physical function as independent variables were performed.

Results: Of the 433 participants, 189 (43.6%) were included in the decline group. Logistic regression analysis revealed hip flexor strength as a primary determinant in the progression of functional capacity decline.

Conclusion: These results suggest that among physical functions, hip flexor strength influences the progression of disability resulting from locomotive dysfunction in older adults.
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http://dx.doi.org/10.1016/j.archger.2021.104499DOI Listing
August 2021

Electromyographic analysis of a selective exercise for the serratus anterior muscle among patients with frozen shoulder and subacromial impingement syndrome.

Am J Phys Med Rehabil 2021 Aug 3. Epub 2021 Aug 3.

Kyoto University Hospital, Rehabilitation Unit, Kyoto, Japan. Department of Orthopedic Surgery, Kyoto University, Kyoto, Japan. Take Physical Conditioning Gym, Kyoto, Japan. Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

Objective: Patients with shoulder disorders show altered periscapular muscle activity [e.g., decreased serratus anterior (SA) and increased upper trapezius (UT) activities]. We herein devised a novel method for strengthening SA without excessive UT activation, named Squeezing Ball exercise (SB-ex) in which patients squeezed a ball between both elbows with maximum voluntary isometric contraction in the horizontal adduction direction with the arms elevated at a 45° angle. The present study aimed to investigate if the SB-ex could produce high muscle activity in the SA in patients with frozen shoulder and subacromial impingement syndrome (SAIS) before the rehabilitation intervention.

Design: This is a proof-of-concept study. SA and UT activities during SB-ex were evaluated using electromyography (EMG) in 16 patients with frozen shoulders and SAIS. EMG signals were normalized using maximal voluntary isometric contraction (MVIC), and the muscle balance ratios (UT/SA) were calculated.

Results: The average SA and UT activity was 69.9% ± 30.8% and 10.2% ± 6.3% MVIC during the SB-ex, respectively, whereas the UT/SA ratio of the affected side was 0.15 ± 0.07.

Conclusion: The high SA activation and low UT/SA ratio during SB-ex could be attributed to the limb position where shortened SA exerts itself without painful subacromial impingement. SB-ex could be a novel rehabilitation tool for patients with frozen shoulders and SAIS.
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http://dx.doi.org/10.1097/PHM.0000000000001860DOI Listing
August 2021

Effective muscle elongation positions for the neck extensor muscles: An ultrasonic shear wave elastography study.

J Electromyogr Kinesiol 2021 Oct 17;60:102569. Epub 2021 Jun 17.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

This study aimed to clarify the effective stretching positions for neck extensor muscles. Fifteen healthy men were measured shear moduli of the right neck extensor muscles using ultrasound shear wave elastography in following positions: rest (Rest), flexion (Flex), contralateral bending (Bend), flexion + contralateral bending (Flex → Bend), flexion + contralateral bending + contralateral rotation (Flex → Bend → ConRot), and flexion + contralateral bending + ipsilateral rotation (Flex → Bend → IpsRot). The increase in the shear modulus indicated a greater muscle elongation. Regarding the upper trapezius and splenius capitis, the shear moduli at Flex → Bend, Flex → Bend → ConRot, and Flex → Bend → IpsRot were significantly higher than those at Rest. The shear moduli at stretching positions, including contralateral bending, were significantly higher than those at Rest and Flex in the levator scapulae. The results indicated that the stretching position with a combination of flexion and contralateral bending could be effective for elongation of the upper trapezius and splenius capitis. Furthermore, the stretching positions including contralateral bending could be effective for the levator scapulae.
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http://dx.doi.org/10.1016/j.jelekin.2021.102569DOI Listing
October 2021

Cut-off Values for Lower Limb Muscle Thickness to Detect Low Muscle Mass for Sarcopenia in Older Adults.

Clin Interv Aging 2021 25;16:1215-1222. Epub 2021 Jun 25.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

Purpose: Ultrasound-based prediction methods for the detection of low muscle mass for sarcopenia in older adults have been explored previously; however, the muscle that most accurately predicts it is unclear. This study aimed to clarify prediction accuracy and cut-off values for ultrasound-derived thigh and lower leg muscle thickness (MT) to detect low skeletal muscle mass index (SMI) in older adults and to estimate cut-off values based on two standard deviations (SD) below younger adult means for the corresponding muscles as an early detection tool for site-specific low muscle mass.

Methods: This study included 204 community-dwelling older (64 males, 140 females, mean age: 75.4 years) and 59 younger (31 males, 28 females, mean age: 22.3 years) adults. The MT of the rectus femoris, vastus intermedius, gastrocnemius, and soleus muscles was measured using ultrasound; SMI was measured using bioelectrical impedance analysis.

Results: The prevalence of a low SMI among older adults was 20.3% (n=13) for males and 21.4% (n=30) for females. The receiver operating characteristic analysis revealed that the total MT for the four muscles measured presented the highest area under the curve (AUC) value to predict low SMI for males (0.849) and females (0.776). The AUC value was the highest for the total MT of the gastrocnemius and soleus muscles for males and the gastrocnemius for females (0.836, 0.748; cut-off value: 5.67 cm, 1.42 cm, respectively). Muscle-specific differences between the low SMI-predicting and SD-based cut-off values were observed. The SD-based value for the rectus femoris (1.85 cm) was substantially higher than the low SMI-predicting value (1.51 cm) in males.

Conclusion: Ultrasound measurement of lower leg muscles may be a simple, robust measure to detect low muscle mass for sarcopenia. Additionally, cut-off values for site-specific muscle mass loss may not always agree with those for whole-limb muscle mass loss.
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http://dx.doi.org/10.2147/CIA.S304972DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8241812PMC
July 2021

Landmark-free, parametric hypothesis tests regarding two-dimensional contour shapes using coherent point drift registration and statistical parametric mapping.

PeerJ Comput Sci 2021 18;7:e542. Epub 2021 May 18.

Department of Archaeology, University of York, York, United Kingdom.

This paper proposes a computational framework for automated, landmark-free hypothesis testing of 2D contour shapes (i.e., shape outlines), and implements one realization of that framework. The proposed framework consists of point set registration, point correspondence determination, and parametric full-shape hypothesis testing. The results are calculated quickly (<2 s), yield morphologically rich detail in an easy-to-understand visualization, and are complimented by parametrically (or nonparametrically) calculated probability values. These probability values represent the likelihood that, in the absence of a true shape effect, smooth, random Gaussian shape changes would yield an effect as large as the observed one. This proposed framework nevertheless possesses a number of limitations, including sensitivity to algorithm parameters. As a number of algorithms and algorithm parameters could be substituted at each stage in the proposed data processing chain, sensitivity analysis would be necessary for robust statistical conclusions. In this paper, the proposed technique is applied to nine public datasets using a two-sample design, and an ANCOVA design is then applied to a synthetic dataset to demonstrate how the proposed method generalizes to the family of classical hypothesis tests. Extension to the analysis of 3D shapes is discussed.
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http://dx.doi.org/10.7717/peerj-cs.542DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8157043PMC
May 2021

The effects of knee pain on knee contact force and external knee adduction moment in patients with knee osteoarthritis.

J Biomech 2021 06 18;123:110538. Epub 2021 May 18.

Department of Physical Therapy, Human Health Science, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo, Kyoto 606-8507, Japan.

Knee osteoarthritis (OA) is a major cause of knee pain, leading to physical dysfunction. External knee adduction moment (KAM), a surrogate measure of knee contact force (KCF) in the medial compartment, is related to knee pain, but the association between KCF and pain severity remains unclear. This study aimed to reveal the differences in KCF due to pain severity. Twenty-eight patients with knee OA were evaluated knee symptoms including pain severity via the Knee Society Score. Based on the median symptom score, 17 points in this study, subjects were classified as having Mild symptomatic OA (n = 15) and Severe symptomatic OA (n = 13). Subjects walked three times at a comfortable speed along a six-meter walkway, and we calculated KAM during the stance phase. KCF magnitude and distribution were also computed using the subject-specific musculoskeletal model, considering physical characteristics such as the femorotibial angle measured by X-ray. No differences in physical characteristics such as femorotibial angle and gait speed were found by symptom severity, whereas KAM and medial KCF at minimum and second peak in Severe symptomatic OA patients were significantly greater than those in Mild symptomatic OA. A significant medial shift of KCF in Severe symptomatic OA was also seen at first peak and minimum. Severe symptomatic OA had a greater medial KCF and medial shift of KCF. Detailed evaluations of KCF magnitude and distribution in addition to KAM would provide crucial information on knee contact force in relation to symptom severity.
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http://dx.doi.org/10.1016/j.jbiomech.2021.110538DOI Listing
June 2021

Influence of simulated hip muscle weakness on hip joint forces during deep squatting.

J Sports Sci 2021 May 19:1-9. Epub 2021 May 19.

Department of Physical Therapy, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

This study aimed to determine the effects of simulated hip muscle weakness on changes in hip joint forces during deep squat motion. Ten healthy individuals performed squat motion at three different positions (0° foot angle [N-squat], 10° toe-in [IN-squat], and 30° toe-out [OUT-squat]). A scaled musculoskeletal model for each participant was used to calculate the muscle and hip joint forces. For each hip muscle, models of full strength, mild muscle weakness (15% decrease), and severe muscle weakness (30% decrease) were created. The muscles affecting the hip joint forces were identified, and the rate of change in the joint forces was compared among the three squat conditions. The anterior hip joint force was increased in the muscle weakness models of the inferior gluteus maximus (iGlutMax) and iGlutMax+deep external rotator (ExtRot) muscles. With 30% muscle weakness of these muscles, statistically significant differences in the rate of increase in the anterior joint force were observed in the following order: IN-squat (iGlutMax, 29.5%; iGlutMax+ExtRot, 41.4%), N-squat (iGlutMax, 18.3%; iGlutMax+ExtRot, 27.8%), and OUT-squat (iGlutMax, 5.6%; iGlutMax+ExtRot, 9.3%). OUT-squat may be recommended to minimize the increase in hip joint forces if accompanied by hip muscle weakness.
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http://dx.doi.org/10.1080/02640414.2021.1929009DOI Listing
May 2021

Enhanced echo intensity and a higher extracellular water-to-intracellular water ratio are helpful clinical signs for detecting muscle degeneration in patients with knee osteoarthritis.

Clin Rheumatol 2021 Oct 17;40(10):4207-4215. Epub 2021 May 17.

Human Health Sciences, Graduate School of Medicine, Kyoto University, 53-Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.

Objectives: Enhanced muscle echo intensity (EI) with ultrasound imaging and a higher extracellular water-to-intracellular water (ECW/ICW) ratio with segmental-bioelectrical impedance spectroscopy (S-BIS) represent muscle quality loss. This study aimed to clarify quadriceps muscle degeneration characteristics, focusing on muscle quality changes in patients with knee osteoarthritis (OA).

Method: Forty-one women with knee OA (mean age, 71.4±6.0 years) and 27 healthy women (mean age, 75.6±4.9 years) participated. Ultrasonography was used to evaluate the muscle thickness (MT) and the EI of each quadriceps compartment. The ECW/ICW ratio was obtained by S-BIS. MT, EI, and ECW/ICW ratio differences between the two groups were tested using univariate analysis of variance, adjusting for age and body mass index. Logistic regression analyses were performed with the group as the dependent variable, and the MT and EI of the vastus medialis (VM) and the ECW/ICW ratio as independent variables.

Results: Patients with knee OA had a significant decrease in VM MT, enhanced VM, and vastus intermedius EIs and a higher ECW/ICW ratio compared with healthy participants. Logistic regression analysis showed that the VM EI (odds ratio [OR], 1.19; 95% confidence interval [CI], 1.06-1.35) and the ECW/ICW ratio were independently associated with knee OA (OR, 1.19; 95% CI, 1.00-1.42).

Conclusions: VM EI and the ECW/ICW ratio, rather than VM MT, characterised quadriceps muscle degeneration in patients with knee OA. Therefore, enhanced EI and a higher ECW/ICW ratio are helpful clinical signs for detecting muscle degeneration in patients with knee OA. Key Points •Echo intensity (EI) of the vastus medialis and the extracellular-to-intracellular water (ECW/ICW) ratio significantly increased in patients with knee osteoarthritis OA). •Enhanced EI and a higher ECW/ICW ratio are useful clinical signs for detecting muscle degeneration in patients with knee OA.
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http://dx.doi.org/10.1007/s10067-021-05763-yDOI Listing
October 2021

Epimuscular myofascial force transmission from biarticular rectus femoris elongation increases shear modulus of monoarticular quadriceps muscles.

J Biomech 2021 06 8;122:110421. Epub 2021 Apr 8.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

This study aimed to examine the effect of rectus femoris (RF) elongation with passive hip angle change on the shear moduli of the vastus lateralis (VL) and medialis (VM) to verify whether Epimuscular myofascial force transmission (EMFT) occurs in the human quadriceps. Fourteen healthy men participated in this study. The shear moduli of the RF, VL, and VM were measured in four hip positions: flexion (Flex), extension and abduction (Ext-Abd), extension (Ext), and extension and adduction (Ext-Add). As the behavior of shear moduli may differ depending on the parts of the vasti muscles, we measured the medial and lateral parts of the VL (Medial-VL and Lateral-VL) and VM (Medial-VM and Lateral-VM). The shear moduli at the Ext and Ext-Add positions were higher than at the Flex position in the RF, VL, and VM. The shear moduli during Ext and Ext-Add were higher than at the Ext-Abd in the RF, VL, and Lateral-VM. Moreover, the shear modulus of the Lateral-VM was higher than of the Medial-VM (Flex: 8.5% higher; Ext-Abd: 15.6%; Ext: 30.2%; Ext-Add: 32.6%). The shear moduli of the VL and VM, which are monoarticular muscles of the knee, increased with passive hip extension or adduction with extension, even when the knee angle was kept constant. The results suggest that EMFT occurs in the quadriceps, and EMFT had a great impact in the Lateral-VM, which is anatomically adjacent to the RF, but it had little effect in the Medial-VM, which is further away from the RF.
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http://dx.doi.org/10.1016/j.jbiomech.2021.110421DOI Listing
June 2021

Strategies for increasing gait speed in patients with hip osteoarthritis: their clinical significance and effects on hip loading.

Arthritis Res Ther 2021 04 28;23(1):129. Epub 2021 Apr 28.

Department of Physical Therapy, Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.

Background: Changes in gait speed are required in various situations and can be achieved by changing stride length, cadence, or both. Differences in strategies for increasing gait speed may have different effects on hip joint and physical function. The purpose of this study was to determine the effects of strategies for increasing gait speed on hip pain, physical function, and changes in hip loading during gait in patients with hip osteoarthritis (OA). We hypothesized that patients who increase gait speed mainly by increasing cadence would have lesser hip pain, a higher physical function, and a lower rate of increase in hip moments with increasing gait speed.

Methods: Forty-seven patients with secondary hip OA (age, 48.3 ± 11.0 years) were included. Gait speed, stride length, cadence, and peak and impulse of the hip moments were measured during gait at self-selected normal and fast gait speeds. The patients were classified as types S (with mainly increasing stride length, n = 11 [23.4%]), C (with mainly increasing cadence, n = 23 [48.9%]), and SC (with increasing stride length and cadence, n = 13 [27.7%]) according to whether they used changes in stride length and/or cadence to transition from normal to fast gait. Hip pain, physical function, and hip moment changes during gait were compared between types.

Results: The physical function was higher in types C (38.0 ± 8.8, P = 0.018) and SC (40.6 ± 8.5, P = 0.015) than in type S (28.2 ± 7.8), even after adjustment for age and minimum joint space width. Hip pain was not significantly different between types. The robustness of these results was confirmed with sensitivity analysis. The rates of increases in peak external hip adduction (P = 0.003) and internal rotation moments (P = 0.009) were lower in type C than in type SC.

Conclusions: Type C tended to suppress the increase in hip moments during fast gait. Types C and SC, which included increased cadence, maintained higher physical function levels than type S. Encouraging the use of cadence-increasing strategy may be useful for reducing hip loading and maintaining physical function in patients with hip OA.
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http://dx.doi.org/10.1186/s13075-021-02514-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8080338PMC
April 2021

Regional differential stretching of the pectoralis major muscle: An ultrasound elastography study.

J Biomech 2021 05 20;121:110416. Epub 2021 Apr 20.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

Pectoralis major (PMa) muscle injuries are becoming more prevalent, and their incidence differs among the PMa regions, i.e., the clavicular, sternal, and abdominal regions. Therefore, identifying the position for effectively lengthening each PMa region is critical in preventing PMa injuries. The purpose of this study was to determine the effective stretching position for each PMa region through shear wave elastography, which can indirectly assess individual muscle lengthening. Fifteen men participated in this study. Twelve stretching positions were compounded with shoulder abductions (45°, 90°, and 135°), pelvic rotation (with or without), shoulder external rotation (with or without), and shoulder horizontal abductions. The shear modulus of each PMa region was measured through shear wave elastography in the stretching positions mentioned above. At the clavicular region, the shear modulus was higher for three stretching positions: shoulder horizontal abduction at 45° abduction during pelvic rotation and shoulder external rotation, shoulder horizontal abduction at 90° abduction, and shoulder horizontal abduction at 90° abduction while considering shoulder external rotation. For the sternal region, the shear modulus was higher in two stretching positions: shoulder horizontal abduction at 90° abduction while adding external rotation, and combination of pelvic rotation and external rotation. For the abdominal region, the shear modulus was higher in the shoulder horizontal abduction at 135° abduction with pelvic and external rotation. These results indicated that the effective stretching position was different for each PMa region.
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http://dx.doi.org/10.1016/j.jbiomech.2021.110416DOI Listing
May 2021

The relation between kinematic synergy to stabilize the center of mass during walking and future fall risks: a 1-year longitudinal study.

BMC Geriatr 2021 04 13;21(1):240. Epub 2021 Apr 13.

Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo, Kyoto, 606-8507, Japan.

Background: Incorrect body weight shifting is a frequent cause of falls, and the control of the whole-body center of mass (CoM) by segmental coordination is essential during walking. Uncontrolled manifold (UCM) analysis is a method of examining the relation between variance in segmental coordination and CoM stability. However, no prospective cohort study has thoroughly investigated how variance in segmental configurations to stabilize the CoM relates to future falls. This study explored whether variance to stabilize the CoM was related to future falls.

Methods: At the baseline visit, 30 community-dwelling older adults walked 20 times on a 6-m walkway. Using kinematic data collected during walking by a three-dimensional motion capture system, UCM analysis was performed to investigate how segmental configuration contributes to CoM stability in the frontal plane. One year after the baseline visit, we evaluated whether the subjects experienced falls. Twelve subjects had experienced falls, and 16 had not. Comparisons of variance between older adults with and without falls were conducted by covariate analysis.

Results: No significant differences in variance were found in the mediolateral direction, whereas in the vertical direction, older adults with fall experiences had a greater variance, reflecting an unstable CoM, than those with no fall experiences.

Conclusions: We verified that the high variance in segmental configurations that destabilize the CoM in the vertical direction was related to future falls. The variables of UCM analysis can be useful for evaluating fall risk.
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http://dx.doi.org/10.1186/s12877-021-02192-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8045323PMC
April 2021

Effective stretching position of the coracobrachialis muscle.

J Biomech 2021 05 20;120:110390. Epub 2021 Mar 20.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

An increase in the stiffness of the coracobrachialis muscle can restrain proper movement of the glenohumeral joint and scapula during arm elevation. Therefore, muscle stiffness should be reduced through stretching. The aim of this study was to determine the effective stretching position of the coracobrachialis muscle using ultrasound shear wave elastography imaging to evaluate the stiffness of individual muscles. Eighteen healthy young men participated in this study. The shear modulus of the coracobrachialis muscle was measured at the following eight shoulder positions: i) 20° abduction (Rest), ii) maximal external rotation at 90° abduction (ER2), iii) maximal internal rotation at 90° abduction (IR2), iv) maximal flexion (Flex), v) maximal extension (Ext), vi) maximal horizontal abduction at 90° abduction (Hab), vii) maximal horizontal abduction and maximal external rotation at 90° abduction (HabER), and viii) maximal horizontal abduction and maximal internal rotation at 90° abduction (HabIR). The shear modulus in each position was compared with that of Rest using the Wilcoxon signed-rank test, and a multiple comparison test was performed among the positions that exhibited significant difference. The shear modulus of all stretching positions was significantly higher than that of Rest, except for Flex. Moreover, the shear moduli of IR2, Ext, Hab, HabER, and HabIR were significantly higher than that of ER2. The shear modulus of Ext was significantly higher than that of HabIR. The coracobrachialis muscle could be stretched effectively at IR2, Ext, Hab, HabER, and HabIR. Among these positions, Ext, Hab, and HabER are recommended for clinical settings.
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http://dx.doi.org/10.1016/j.jbiomech.2021.110390DOI Listing
May 2021

Age-related changes in gait speeds and asymmetry during circular gait and straight-line gait in older individuals aged 60-79 years.

Geriatr Gerontol Int 2021 May 29;21(5):404-410. Epub 2021 Mar 29.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

Aim: The present study aimed to investigate the age-related changes in gait speeds and asymmetry during circular and straight-line gaits among older adults aged 60-79 years.

Methods: The study included 391 community-dwelling older adults aged >60 years, who participated in the Nagahama cohort study. They were assigned to four age groups: 60-64 years (early 60s), 65-69 years (late 60s), 70-74 years (early 70s) and 75-79 years (late 70s). For the circular gait test, the time required to walk twice around a 1-m diameter circle for right and left rotations were measured. The average time of the two trials was measured as the circular gait time, and the side-to-side difference in the circular gait times was calculated as an asymmetry index. Walking speed, asymmetry of step length, and asymmetry of stance duration time during straight-line gait at comfortable and maximal walking pace were measured.

Results: Circular gait time in older women in the late 70s group was significantly slower than that in other age groups; however, no age-related change was observed in older men. Maximal gait speeds in the early and late 70s groups were significantly slower than those in the early 60s group.

Conclusions: Age-related decline in circular gait speed was observed in older women aged ≥75 years, but not in older men. Maximal straight-line gait speed decreased significantly in both genders after the age of 70 years. Geriatr Gerontol Int 2021; 21: 404-410.
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http://dx.doi.org/10.1111/ggi.14150DOI Listing
May 2021

Acute effects of repetitive peripheral magnetic stimulation following low-intensity isometric exercise on muscle swelling for selective muscle in healthy young men.

Electromagn Biol Med 2021 Jul 25;40(3):420-427. Epub 2021 Mar 25.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

Repetitive peripheral magnetic stimulation (rPMS) is a non-invasive stimulator that can induce strong muscle contraction in selective regions. This study aimed to measure acute changes in skeletal muscle thickness induced by rPMS following a low-intensity exercise. Fifteen healthy young men performed an isometric knee extensor exercise at 30% of maximum strength consisting of three sets of 10 contractions on their dominant leg. rPMS was then applied on the vastus lateralis (VL) at the maximum intensity of the rPMS device. Muscle thicknesses of the rectus femoris (RF) and VL were measured using an ultrasound device and were compared among baseline, post-exercise, and post-rPMS. There were significant increases in muscle thickness of both the RF and VL post-exercise compared with baseline values (RF: baseline; 24.7 ± 2.4, post-exercise; 25.3 ± 2.4 mm, = .034, VL: baseline; 27.0 ± 2.8, post-exercise; 27.4 ± 2.8 mm, = .006). Compared with post-exercise, there was a significant increase post-rPMS in only the VL (VL: post-rPMS; 28.3 ± 2.9 mm, = .002). These findings suggest that low-intensity isometric exercise can induce acute increases in muscle thickness (muscle swelling) in synergist muscles, and rPMS following exercise can induce further acute muscle swelling via repetitive muscle contraction.
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http://dx.doi.org/10.1080/15368378.2021.1907402DOI Listing
July 2021

Quantification of muscle coordination underlying basic shoulder movements using muscle synergy extraction.

J Biomech 2021 05 7;120:110358. Epub 2021 Mar 7.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

Numerous muscles around the shoulder joint are required to work in a coordinated manner, even when a basic shoulder movement is executed. Muscle synergy can be utilized as an index to determine muscle coordination. The purpose of the present study was to investigate the muscle coordination among different shoulder muscles underlying basic shoulder movements based on muscle synergy. Thirteen men performed 14 multiplanar shoulder movements; five movements were associated with elevation and lowering, while five were associated with horizontal abduction and adduction. The four additional movements were simple rotations at different positions. Muscle activity was measured from 12 muscle portions using surface electromyography. Using the dimensionality reduction technique, synergies were extracted first for each movement separately ("separate" synergies), and then for the global dataset (containing all movements; "global" synergies). The least number that provided 90% of the variance accounted for was selected as the optimal number of synergies. For each subject, approximately two separate synergies and approximately six global synergies with small residual values were extracted from the separate and global electromyography datasets, respectively. Specific patterns of these muscle synergies in each task were observed during each movement. In the cross-validation method, six global synergies explained 88.0 ± 1.3% of the global dataset. These findings indicate that muscle activities underlying basic shoulder movements are expressed as six units, and these units could be proxies for shoulder muscle coordination.
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http://dx.doi.org/10.1016/j.jbiomech.2021.110358DOI Listing
May 2021

Immediate effects of stance and swing phase training on gait in patients with stroke.

Int J Rehabil Res 2021 06;44(2):152-158

Department of Physical Therapy, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto.

To compare the effects of gait trainings targeting the stance (stance training) and the swing phases (swing training) among the subjects with stroke, and quantify the characteristics in the subjects who benefitted from either the stance training or the swing training. Sixteen subjects with stroke performed the stance training, which focused on the center of pressure to move from the heel to the forefoot, and the swing training, which focused on the improvement of hip flexion in the swing phase. To investigate the immediate effects of the stance training and the swing training, the instrumented gait analysis was performed before and after training. To quantify the characteristics, subjects were divided into two groups based on the gait speed change. These two groups were compared using clinical examinations. After the stance training, the center of pressure displacement of the paretic limb was increased compared with the swing training. Subjects who benefitted from the stance training had slower Timed Up and Go and weaker paretic hip muscle strength than those who benefitted from the swing training. Stance training may be more effective in subjects with slower Timed Up and Go outcomes and weaker hip muscles.
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http://dx.doi.org/10.1097/MRR.0000000000000464DOI Listing
June 2021

Acute and Prolonged Effects of Stretching on Shear Modulus of the Pectoralis Minor Muscle.

J Sports Sci Med 2021 03 1;20(1):17-25. Epub 2021 Mar 1.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Shogoin, Sakyo-ku, Kyoto, Japan.

Increased muscle stiffness of the pectoralis minor (PMi) could deteriorate shoulder function. Stretching is useful for maintaining and improving muscle stiffness in rehabilitation and sport practice. However, the acute and prolonged effect of stretching on the PMi muscle stiffness is unclear due to limited methodology for assessing individual muscle stiffness. Using shear wave elastography, we explored the responses of shear modulus to stretching in the PMi over time. The first experiment (n = 20) aimed to clarify the acute change in the shear modulus during stretching. The shear modulus was measured at intervals of 30 s × 10 sets. The second experiment (n = 16) aimed to observe and compare the prolonged effect of different durations of stretching on the shear modulus. Short and long stretching duration groups underwent 30s × 1 set and 30s × 10 sets, respectively. The assessments of shear modulus were conducted before, immediately after, and at 5, 10, and 15 min post-stretching. In experiment I, the shear modulus decreased immediately after a bout (30 s) of stretching (p < 0.001, change: -2.3 kPa, effect size: = 0.72) and further decreased after 3 repetitions (i.e., 90 s) of stretching (p = 0.03, change: -1.0 kPa, effect size: = 0.53). In experiment II, the change in the shear modulus after stretching was greater in the long duration group than in the short duration group (p = 0.013, group mean difference: -2.5 kPa, partial = 0.36). The shear modulus of PMi decreased immediately after stretching, and stretching for a long duration was promising to maintain the decreased shear modulus. The acute and prolonged effects on the PMi shear modulus provide information relevant to minimum and persistent stretching time in rehabilitation and sport practice.
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http://dx.doi.org/10.52082/jssm.2021.17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7919355PMC
March 2021

Verification of validity of gait analysis systems during treadmill walking and running using human pose tracking algorithm.

Gait Posture 2021 03 13;85:290-297. Epub 2021 Feb 13.

Department of Physical Therapy, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

Background: The human tracking algorithm called OpenPose can detect joint points and measure segment and joint angles. However, the validity of gait analysis using OpenPose has not been examined yet.

Research Question: What is the validity of OpenPose-based gait analysis?

Methods: Twenty-four healthy young people participated in this study. The participants were assessed during walking and running. Pelvic segment angles, and hip, knee, and ankle joint angles during treadmill walking and running were measured using VICON. Simultaneously, images were captured using digital cameras from the right and back sides. After processing with OpenPose, the corresponding angles were measured from the estimated joint points. To validate these estimations, linear regression analysis was performed, and intraclass correlation coefficients [ICCs (2, 1)] between the data obtained by OpenPose and VICON were calculated. Furthermore, the agreement between the data obtained by OpenPose and VICON was assessed by Bland-Altman analysis.

Results: For most ranges of motion (ROM) in the sagittal plane, the hip, knee, and ankle joints had large coefficients of determination, without proportional biases. For most peak angles in the sagittal plane, the knee and ankle joints had large coefficients of determination without proportional biases, although the hip joint had nonsignificant coefficients of determination and proportional biases. In particular, for the hip flexion-extension ROM and peak knee flexion angle during running and the knee ROM during slow walking, the ICCs showed good to excellent agreement. However, for the parameters of the pelvis and hip joint in the frontal plane, there were nonsignificant coefficients of determination and poor ICCs with fixed and proportional biases.

Significance: The lower limb ROM in the sagittal plane during gait can be measured by the OpenPose-based motion analysis system. The markerless systems have the advantage of being more economical and convenient than conventional methods.
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http://dx.doi.org/10.1016/j.gaitpost.2021.02.006DOI Listing
March 2021

Differences in shear elastic modulus of the latissimus dorsi muscle during stretching among varied trunk positions.

J Biomech 2021 03 9;118:110324. Epub 2021 Feb 9.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Japan.

The latissimus dorsi (LD) can be divided into the upper, middle, and lower parts, but the effective stretching positions for each part are unknown. In this study, we aimed to investigate effective trunk positions for stretching of the LD. A total of 14 healthy males participated in this study. The following seven trunk positions were chosen as the LD stretching positions; upright of the trunk (Baseline), flexion of the trunk (Flex), contralateral bending of the trunk (LB), contralateral rotation of the trunk (Rot), flexion and contralateral bending of the trunk (Flex + LB), flexion and contralateral rotation of the trunk (Flex + Rot), and contralateral bending and contralateral rotation of the trunk (LB + Rot). Maximal elevation of the upper limb was passively added to all positions. The shear elastic modulus, used as the index of muscle elongation, was measured at the four parts (upper, middle, lower, distal parts) of the LD. The shear elastic moduli showed obviously high values in Rot and LB + Rot at the upper, middle, and distal parts, and also in LB, Rot, and LB + Rot at the lower part. These findings suggest that contralateral trunk rotation, or a combination of contralateral trunk bending and rotation are effective trunk positions for stretching all parts of the LD. Contralateral trunk bending was also effective for stretching the lower part of the LD.
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http://dx.doi.org/10.1016/j.jbiomech.2021.110324DOI Listing
March 2021

Coexistence of low back pain and lumbar kyphosis is associated with increased functional disability in knee osteoarthritis: the Nagahama Study.

Arthritis Care Res (Hoboken) 2021 Feb 19. Epub 2021 Feb 19.

Kyoto University, Department of Physical Therapy, Human Health Sciences, Graduate School of Medicine, Kyoto, Japan.

Objective: To examine the association of low back pain (LBP) and lumbar kyphosis with functional disabilities and knee symptoms in patients with knee osteoarthritis (OA).

Methods: We analyzed 586 participants (80.1% female; age, 68.8 ± 5.2 years) from the Nagahama Study who were aged ≥60 years and had radiographically confirmed knee OA. The Knee Scoring System (KSS) was used to assess functional disabilities and knee symptoms. LBP was defined as the presence of any persistent back pain for more than 3 months. Lumbar kyphosis was determined by skin-surface methods using a computer-aided electronic device called the Spinal Mouse. Multiple linear regression analysis was used for assessing the association of LBP and lumbar kyphosis with the KSS scores. Subgroup analyses based on sex were also performed.

Results: LBP and lumbar kyphosis were independently associated with a lower KSS function score after adjustment for covariates (mean difference [95%CI, confidence interval] = -4.96 [-7.56 to -2.36] points for LBP alone, -4.47 [-8.51 to -0.43] points for lumbar kyphosis alone, and -13.86 [-18.86 to -8.86] points for the coexistence of LBP and lumbar kyphosis, respectively). The coexistence of LBP and lumbar kyphosis in women was associated with a lower KSS symptom score (mean difference [95%CI] = -4.49 [-6.42 to -2.55] points).

Conclusion: These findings suggest that both LBP and lumbar kyphosis are useful clinical signals indicating functional disability and knee symptoms in patients with knee OA.
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http://dx.doi.org/10.1002/acr.24580DOI Listing
February 2021

Assessment of Edematous Changes Using Three-Dimensional Body Scanning and Segmental-Bioelectrical Impedance Spectroscopy.

Lymphat Res Biol 2021 Feb 19. Epub 2021 Feb 19.

Department of Physical Therapy, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

The primary purpose of this study was to clarify the occurrence of sites of edematous changes using the measured circumferences of the thigh and lower leg via three-dimensional (3D) body scanning. The secondary purpose was to determine the relationship between the volume changes using 3D body scanning and the resistance changes as indicator of extracellular water (ECW) via segmental-bioelectrical impedance spectroscopy (S-BIS). Fifteen healthy women participated. Limb circumferences were measured using 3D body scanning at 10% intervals between 50% and 80% in the thigh circumference and between 0% and 80% in the lower leg circumference. The resistance of the ECW component (R) and total body water (R) was measured using S-BIS in the thigh and lower leg segments. These measurements were conducted at baseline and 6 hours postobservation. A paired -test was conducted for the differences in these parameters, and the effect sizes (ESs) were calculated using Cohen's . Correlations between changes in segmental volume and R were analyzed. Measurement-site circumferences and segmental volume significantly increased in the lower leg at postobservation but not in the thigh. The ES of circumference changes in the lower leg's central region were larger (ESs were 0.40-0.71 at 30%-50%) than in other regions. A significant correlation was observed between changes in segmental volume and R of the lower leg (ρ = -0.79,  < 0.001). Assessing the circumference using 3D body scanning, we found the edematous changes to be significant in the lower leg's central regions. Moreover, volumetry using 3D body scanning can detect edematous change in the lower leg.
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http://dx.doi.org/10.1089/lrb.2020.0087DOI Listing
February 2021

Extracellular-to-intracellular water ratios are associated with functional disability levels in patients with knee osteoarthritis: results from the Nagahama Study.

Clin Rheumatol 2021 Jul 23;40(7):2889-2896. Epub 2021 Jan 23.

Department of Physical Therapy, Human Health Sciences, Graduate School of Medicine, Kyoto University, 53-Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.

Introduction/objectives: To test the hypothesis that greater extracellular-to-intracellular water (ECW/ICW) ratios in lower-limb muscles are associated with worsened functional abilities in patients with knee osteoarthritis (OA).

Methods: We analyzed data from 787 participants (82.2% female; mean age, 69.6 ± 5.3 years) from the Nagahama Prospective Cohort who were ≥60 years old and had radiographically confirmed bilateral knee OA. The Knee Scoring System (KSS) was used to assess functional abilities. Lower-limb ECW/ICW ratios and skeletal mass index values were determined with multi-frequency bioelectrical impedance analysis (BIA). Multiple linear regression analysis was used to test for associations between ECW/ICW ratios and functional abilities. Subgroup analyses based on OA severities and symptomaticity were also conducted.

Results: Increased ECW/ICW ratios were associated with a 4.38-point decrease in the KSS function scores (95% confidence interval [CI], 3.15-5.62 points) after adjusting for covariates. This association varied according to the degree of knee symptoms, especially in individuals with radiologically mild OA. ECW/ICW ratios in individuals with asymptomatic mild OA were associated with a 2.14-point decrease in the KSS function score (95% CI, 0.32-3.96 points), whereas those in individuals with severe symptomatic mild OA were associated with a 6.16-point decrease (95% CI, 2.13-10.19 points).

Conclusions: Our findings indicate that higher ECW/ICW ratios are associated with greater functional disability in patients with knee OA. Therefore, ECW/ICW ratio measurements with multi-frequency BIA can serve as valuable indicators for functional disability in patients with knee OA. Key Points • Higher extracellular-to-intracellular water (ECW/ICW) ratios are associated with greater functional disability levels in patients with knee osteoarthritis (OA). • ECW/ICW ratios are useful clinical signs as a biomarker for poor functional abilities in patients with knee OA.
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http://dx.doi.org/10.1007/s10067-021-05591-0DOI Listing
July 2021

The function of the popliteus muscle: An in vivo ultrasound shear wave elastography study.

Hum Mov Sci 2021 Apr 21;76:102751. Epub 2021 Jan 21.

Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.

The function of the popliteus muscle [PM] is crucial to knee function. However, it remained unclear in vivo. Thus, this study aimed to explore the PM function in the non-weight-bearing and the weight-bearing conditions in vivo. Fourteen healthy subjects participated in this study. The muscle stiffness of the PM was measured using shear wave elastography as an index of muscle force. Muscle stiffness was measured at 30° knee flexion as a reference value. Muscle stiffness was also measured at passive 0°knee flexion and passive 20° external rotation and internal rotation at 30° knee flexion, and during isometric knee extension, flexion, external rotation, and internal rotation at 30° knee flexion. Moreover, muscle stiffness was measured during one-leg standing at 0° and 30° of knee flexion. Muscle stiffness was significantly greater at passive 0° knee flexion and 20° external rotation and during isometric knee flexion and internal rotation than the reference value. Two-way analysis of variance revealed significant main effects of weight bearing and knee angle: Muscle stiffness increased with weight bearing and knee extension. Moreover, muscle stiffness was significantly lower at 30° than at 0° knee flexion during one-leg standing. The PM function is knee flexion and internal rotation, and the PM force increases with weight bearing and decreases with knee flexion during one-leg standing.
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http://dx.doi.org/10.1016/j.humov.2020.102751DOI Listing
April 2021

Relation between frontal plane center of mass position stability and foot elevation during obstacle crossing.

J Biomech 2021 02 12;116:110219. Epub 2021 Jan 12.

Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo, Kyoto 606-8507, Japan.

High foot elevation during obstacle crossing is viewed as a conservative strategy in older adults, but excessive foot elevation may result in large mediolateral center of mass (CoM) displacement. Since an incorrect transfer of CoM can lead to balance loss during locomotion, both appropriate foot elevation and CoM position must be controlled and coordinated by adjusting body segment positions. However, no studies have revealed time profiles of CoM position by coordinated segment movements and the relation of foot elevation with CoM position during obstacle crossing. Twenty-five healthy older adults crossed an obstacle (depth: 1 cm, width: 60 cm, height: 8 cm) during comfortable-speed walking. Synergy indices were calculated during lead- and trail-limb swing using uncontrolled manifold analysis. High synergy index values indicate a strong multi-joint kinematic synergy, or co-fluctuations in segment movements, to control CoM position. The maximum foot heights of the swing limbs were calculated as the maximum vertical distance between the most distal foot point and the ground. In the mediolateral direction, synergy index values during early lead-limb swing were significantly greater than during early trail-limb swing, and in the vertical direction, large synergy index values were found during early- and mid-swing phases. Moreover, maximum trail-foot height was correlated to vertical synergy index during early phase. CoM position was not well controlled by a kinematic synergy during trail-limb swing and the low control of CoM position was observed with great trail-foot height. The results suggest that a conservative strategy with great trail-foot height would not always be helpful for successful obstacle crossing.
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http://dx.doi.org/10.1016/j.jbiomech.2020.110219DOI Listing
February 2021

Relationship between postural sway on an unstable platform and ankle plantar flexor force steadiness in community-dwelling older women.

Gait Posture 2021 02 25;84:227-231. Epub 2020 Dec 25.

Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.

Background: Force steadiness is evaluated as force variability during constant force exertion around a target level. Ankle plantar flexor force steadiness is reported to be related to postural sway on an unstable platform in healthy young adults; however, this relationship in older adults is unclear.

Research Question: This study aimed to investigate whether ankle plantar flexor force steadiness was related to postural sway on stable and unstable platforms in older adults.

Methods: Twenty-six community-dwelling older women participated in this study (72 ± 6 years). Maximal isometric strength and force steadiness at 5%, 20 %, and 50 % of the maximal strength of ankle plantar flexion were assessed. Postural sway in the anteroposterior direction during bipedal standing was measured on stable and unstable platforms.

Results: The results showed that force steadiness at any intensity level and maximal isometric strength were not related to postural sway on the stable platform. Force steadiness at 20 % of maximal strength alone was significantly correlated with postural sway on the unstable platform (ρ = 0.441, p < 0.05).

Significance: These results indicate that the ability to control muscle force could be important for postural stability on an unstable platform in older adults.
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http://dx.doi.org/10.1016/j.gaitpost.2020.12.023DOI Listing
February 2021

Muscle size-scaled shear elastic modulus: A muscle force index independent of maximal voluntary contraction, assessed during elbow extension.

J Biomech 2020 11 22;112:110049. Epub 2020 Sep 22.

Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Kawara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.

Shear elastic modulus (G) can differ among individuals due to muscle size and other factors, even for constant muscle force. Inter-individual comparisons of G usually require normalization by maximal voluntary contraction (MVC), but MVC procedures may not be appropriate for certain clinical populations including those presenting with pain or other compromised functionality. This study aimed to test whether muscle size-scaled G, which does not require MVC testing, would yield stronger correlation with absolute torque than unscaled G. Twelve-healthy males performed isometric elbow extension across a range of torque magnitudes (from 5 Nm until 60% MVC). G of the triceps brachii was measured using shear wave elastography during each trial. Cross-sectional area (CSA) and muscle thickness (MT) of the triceps brachii were measured at rest. Scaled G was calculated as a product of G and CSA or MT ("G-CSA" and "G-MT", respectively). Within-individual linear regressions were conducted between absolute torque and the three force indicator variables. The regression slopes' coefficient of variation (CV) was calculated for each indicator across individuals. Between-individual correlation coefficients were calculated, after pooling all data across individuals into a single regression analysis for each indicator. Linear regression found that inter-individual slope variation increased in the following order: G-CSA, G-MT, and unscaled G (CV = 0.15, 0.18, and 0.29, respectively). Pooled-individual correlation coefficients were significantly higher in G-CSA and G-MT than in unscaled G (r = 0.948, 0.924, and r = 0.783, respectively). These results suggest that muscle size-scaled G may be more appropriate than unscaled G when comparing shear moduli across individuals.
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http://dx.doi.org/10.1016/j.jbiomech.2020.110049DOI Listing
November 2020

Effects of trunk lean and foot lift exercises in sitting position on abdominal muscle activity and the contribution rate of transversus abdominis.

Eur J Appl Physiol 2021 Jan 30;121(1):173-181. Epub 2020 Sep 30.

Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan.

Purpose: Abdominal hollowing exercise has been recommended to improve trunk stability. Trunk lean and foot lift exercises while sitting may easily promote abdominal muscle activity even in people who cannot perform abdominal hollowing consciously. The purpose of the present study was to examine the changes in abdominal muscle activity and contribution rate of the transversus abdominis muscle (TrA) when leaning the trunk and lifting the foot during sitting.

Methods: The muscle stiffnesses (indicators of muscle activity) of the right rectus abdominis, external oblique, internal oblique, and TrA of 14 healthy men were measured during abdominal hollowing and the following nine sitting tasks: reference posture, 15° and maximal posterior trunk lean, 20° and maximal ipsilateral and contralateral trunk lean, and ipsilateral and contralateral foot lift. The TrA contribution rate was calculated by dividing the TrA stiffness by the sum of the abdominal muscles' stiffnesses.

Results: The TrA stiffness was significantly higher in abdominal hollowing than in reference posture, posterior and ipsilateral trunk lean, and ipsilateral foot lift, but not higher than in contralateral trunk lean and contralateral foot lift. There was no significant difference in the TrA contribution rates between abdominal hollowing and ipsilateral or contralateral foot lift.

Conclusion: The contralateral trunk lean or contralateral foot lift could enhance TrA activity for people who cannot perform abdominal hollowing consciously. The contralateral foot lift could particularly be beneficial to obtain selective activity of TrA.
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http://dx.doi.org/10.1007/s00421-020-04508-0DOI Listing
January 2021
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