塙 大樹

Ultrasound imaging is used to measure the muscle–tendon junction (MTJ) to investigate the mechanical properties of the tendon and the interaction of the muscle–tendon unit in vivo. Although the MTJ can be observed clearly in the resting state, accurate tracking of the MTJ is difficult during muscle contractions due to changes in its morphology. We devised a novel method using an algorithm that extracts and tracks multiple feature points in ultrasound images to automatically measure the MTJ that moves during muscle contraction. Instead of using a single reference image, multiple feature points are used to improve the tracking performance during the deformation of the MTJ. Subsequently, we experimentally evaluated the usefulness of this method. Tests were conducted on 20 healthy participants performing isometric maximal contractions, and ultrasound echo images of the medial gastrocnemius and Achilles tendon junctions were recorded. MTJ excursion was calculated using the developed multiple feature point algorithm and two conventional methods—multi-updating template-matching and modified Lucas–Kanade (LK)—based on automatic and manual analyses. The root mean square error (RMSE) was used to compare the results. The intraclass correlation coefficient (ICC) was used to evaluate the repeatability among examiners. RMSE was 1.57 ± 0.62 for the proposed algorithm and 2.18 ± 0.89 and 1.84 ± 1.13 for the conventional methods. The Bland-Altman plot showed that the proposed method exhibited a lower 95% confidence interval than the two conventional methods. Thus, the proposed algorithm had the smallest error. Furthermore, the ICC values were 0.96, 0.40, and 0.86 for the proposed algorithm, multi-updating template-matching, and the modified LK method, respectively. When tracking an MTJ excursion that flexibly changes its shape, the use of multiple feature points provides robust results and achieves tracking that approximates the manual analysis results.

Abstract Plantar fasciitis is one of the most common musculoskeletal injuries in runners and jumpers, with a higher incidence in females. However, mechanisms underlying sex-associated differences in its incidence remain unclear. This study investigated the possible differences in landing and jumping kinematics and kinetics of the foot between sexes during drop-jump activities. Twenty-six participants, including 13 males and 13 females, performed drop-jumps from a platform onto force plates. Nineteen trials including ten males and nine females were selected for inverse dynamics analysis. The patterns of stretch and tensile force generated by the plantar aponeurosis (PA) were estimated using a multi-segment foot model incorporating the PA. Our results demonstrated that dorsiflexion, angular velocity, and normalized plantarflexion moment of the midtarsal joint right after the heel landed on the floor were significantly larger in females than in males. Consequently, the PA strain rate and tensile stress tended to be larger in females than in males. Such differences in the kinematics and kinetics of the foot and the PA between sexes could potentially lead to a higher prevalence of foot injuries such as plantar fasciitis in females.

Abstract Rising movements from bed comprise an important aspect of recovery from the bedridden state; however, they have not been sufficiently investigated using motion analysis studies. In particular, the effect of using the upper limb of the non-rising side before waist flexion on rising movements remains to be analyzed; this study aimed to clarify this effect. Accordingly, motion analyses were performed on rising movements under two constraint conditions, namely raising the upper limb of the non-rising side (upper limb use-condition) and keeping it in contact with the pelvis (upper limb non-use-condition); subsequently, the kinematics and kinematics parameters were compared. In comparison with the upper limb use-condition, in the upper limb non-use-condition, the distance traveled by the center of mass of the body (CoM trajectory, p < 0.01) increased while switching from the half-side-lying to on-hand postures, horizontal body movement (movement speed (Normalized time/total time), p < 0.01 and weight of center of body mass (CoM momentum in horizontal plane), p < 0.05) during the same period increased, and the half-side-lying time approached the peak value of the waist flexion angular velocity (Time lag between from half-side-lying to waist angler peak velocity, p < 0.05). The compensatory movement that occurred due to the upper limb non-use-condition denoted an increase in body momentum in the horizontal direction, rather than in the sagittal plane. Therefore, the upper limb on the non-rising side contributed to the smooth movement of the body in the horizontal direction. Moreover, this study demonstrated that asymmetrical rising movement in the diagonal direction is a characteristic movement wherein the horizontal movement of the body constitutes the main movement.

Abstract We investigated the coordinated activity patterns of muscles based on cosine tuning in the elderly during an isometric force exertion task. We also clarified whether these coordinated activity patterns contribute to the control of hip and knee joint torque and endpoint force as co-activation. Preferred direction (PD) of activity for each muscle in 10 young and 8 older males was calculated from the lower limb muscle activity during isometric force exertion task in various directions. The covariance of endpoint force (η) was calculated from the exerted force data using a force sensor. Relationship between PD and η was used to examine the effect of muscle co-activation on the control of endpoint force. Co-activation between rectus femoris and semitendinosus/biceps femoris increased with changes in muscle PD. Additionally, the η values were significantly low, suggesting that co-activation of multiple muscles may contribute to endpoint force exertion. The mechanism for cooperative muscle activity is determined by the cosine tuning of the PD of each muscle, which affects the generation of hip and knee joint torque and endpoint force exertion. Co-activation of each muscle’s PD changes with age, causing increased muscle co-activation to control torque and force. We demonstrated that co-activation in the elderly is a stabilizer of unsteady joints and a muscle control strategy for cooperative muscle activity.

ABSTRACT Rhythmic limb multi-joint movement like locomotion is controlled by intralimb coordination. Intralimb coordination changes entail immediate alterations in movement patterns and be related with cerebellum function. Synchronized cerebellum activity has known to modulate the frequency of walking, but not known the effect of only intralimb coordination. The purpose of this study was to reveal the effect of synchronized and unsynchronized cerebellum activity on the coordination of multi-joint movements of the unilateral leg in young and elderly people. To achieve our purpose, we applied synchronized and unsynchronized cerebellum transcranial alternating current stimulation during cyclic unilateral multi-joint movement by visual tracking task. The results showed that the reduction in comprehensive synchrony between targets and movements through trials had no significant differences under all stimulus conditions in young and elderly people. However, the reduction in variation of synchronization through trials was significantly smaller under the synchronized transcranial alternating current stimulation condition in both young and elderly groups. Variation of synchronization was remarkably reduced under the synchronized transcranial alternating current stimulation condition for the elderly group. This study showed that movement-synchronized cerebellum activity contributes to reducing fluctuations in movement synchrony by coordinating unilateral multi-joint movements. Moreover, this reduction was remarkable in the elderly group.

急性期脳卒中患者の立ち上がり動作における異常筋シナジー（筋活動パタン）を階層クラスタ分析により分類した結果、重症度に応じて健常成人とは異なるクラスタが形成された。本研究結果は、早期離床時の定量的評価として価値がある。

This study aimed to evaluate the validity and reliability of our new multi-segment foot model by measuring a dummy foot, and examine the kinematic characteristics of our new multi-segment foot model by measuring the living body. Using our new model and the Rizzoli model, we conducted two experiments with a dummy foot that was moved within a range from -90 to 90 degrees in all planes; for the living body, 24 participants performed calf raises, gait, and drop jumps. Most three-dimensional (3D) rotation angles calculated according to our new models were strongly positively correlated with true values (r > 0.8, p < 0.01). Most 3D rotation angles had fixed biases; however, most of them were in the range of the limits of agreement. Temporal patterns of foot motion, such as those in the Rizzoli model, were observed in our new model during all dynamic tasks. We concluded that our new multi-segment foot model was valid for motion analysis and was useful for analyzing the foot motion using 3D motion capture during dynamic tasks.

BACKGROUND: Adaptation to split-belt treadmill walking differs between individual stroke survivors. Many discussions only address spatiotemporal parameters that are related to movement, and the changes in interlimb spatiotemporal parameters as a consequence of adaptation are poorly understood. OBJECTIVES: To investigate symmetry of the center of pressure (CoP) position relative to the center of mass (CoM), and ascertain whether this can be used to identify differences in adaptation of interlimb spatiotemporal parameters among stroke survivors during split-belt walking. METHODS: Twenty-two chronic post-stroke patients and nine elderly controls walked in tied- then split-belt (2:1 ratio of fast:slow) conditions. Spatiotemporal parameters were compared within groups to assess symmetry of the CoM-CoP angle at foot contact. RESULTS: Asymmetry of the CoM-CoP angle was associated with asymmetry of spatiotemporal parameters. Re-establishment of symmetry of CoM-CoP angle was reflected in re-established symmetry of spatiotemporal parameters in post-stroke and control participants. CONCLUSIONS: Post-stroke patients who re-establish symmetry of the COM-COP angle are able to adapt their walking for split-belt perturbation. This suggests that predictively symmetric foot placements on the fast and slow sides are necessary for adaptation in walking. Symmetrical foot placement is achieved by interlimb coordination and may contribute to dynamic stability.

<p> 【目的】歩行における前額面上の足部軌道は能動的かつ多関節協調をもって行われ歩行安定性を担保する。また，前額面における足部軌道制御の結果である歩隔は体幹運動の影響を受け変化する。本研究は上部体幹運動の拘束による足部軌道制御およびその多関節協調性への影響を明らかにすることを目的として実施した。【方法】三次元動作解析装置を用いて，上部体幹運動を拘束する条件と自由歩行条件において，足部軌道変化と軌道を制御する多関節協調性の変化をUncontrolled manifold（UCM）解析を用いて明らかにした。【結果】足部軌道と多関節協調性は両条件において変化を認めなかった。しかし，協調性を構成する全体的な変動性は上部体幹拘束によって上昇した。【考察】歩行における前額面上の足部軌道とその多関節協調性は身体的拘束による運動変動性増加によって変化しない頑健さを有する可能性を示唆した。</p>

<p> 【目的】本研究の目的は，変形性膝関節症者（以下，膝OA）の歩行における筋シナジーがKL分類と運動力学のどちらと関連するかを明らかにすることである。【方法】膝OA患者10名は，トレッドミル歩行を行い，体幹・下肢16筋の筋電図から筋シナジーを抽出した。同時に前額面の股・膝関節モーメントを取得した。各被験者の筋シナジー数に対して，KL分類における重症度，外部股関節内転モーメントと膝関節外転モーメントとの比較検討を行なった。【結果】筋シナジー数の変化とKL分類は有意な相関を示さなかった。一方で，筋シナジーがより少ない被験者においては，外部股関節内転モーメントが増加する傾向が示された。【考察】KL分類と臨床症状は必ずしも一致しないという先行研究と類似する結果を示した。一方で，筋シナジーは，膝OA歩行の股・膝関節の特徴を反映し，歩行機能に特化した新たな機能評価指標として有用である可能性を示した。</p>

<p>【目的】片麻痺者と健常人におけるsplit-belt歩行時の床反力推進成分の変化を明らかにすることとした。【方法】慢性期片麻痺者8名，健常成人15名に対しダブルベルトトレッドミルにて通常歩行2分間，続いて麻痺側が倍速に変化し，非対称歩行を5分間行った。計測は三次元動作解析装置を用い，立脚時間，ステップ長，床反力推進成分（GRFy）のRMS値，ピークタイミングを抽出し，対称（Baseline）・非対称（Early-adapt，Late-adapt）歩行での変化を一要因の反復測定分散分析，多重比較検定を行った。【結果】GRFyピークタイミングのみがsplit-beltにより歩行周期において早期化した健常人と異なり，片麻痺者では変化しなかった。【結論】本研究のsplit-belt条件では，麻痺側下肢の床反力推進成分ピークタイミングを健常化するには至らない可能性が示唆された。</p>

【目的】近年，初期変形性膝関節症（膝OA）の軟骨厚の減少に矢状面の膝関節トルクの関与が報告された。そのため膝OA患者が立ち上がり動作時に矢状面において力源に主にどのトルク成分を用いているか，また，膝関節の力学的動態に対して股関節や足関節がどのように関係しているかを明らかにすることを目的とした。【方法】対象は膝OA患者4名，健常高齢者3名，課題動作は立ち上がり動作とした。逆動力学計算を用いて下肢3関節のネットトルク（NET）,筋トルク（MUS），相互作用トルク（INT），重力トルク（GRA）,椅子からの反力（CHAIR）を算出し，動作全体，相ごとの各トルクの寄与率（CI）を求めた。【結果】離殿～足関節最大背屈相においてCIは膝関節MUSで有意に高く,膝関節INTでは有意差を認めなかった。またすべての関節においてNETは高齢者に比べて膝OAで低かった。【結論】膝OA患者は立ち上がり動作時の膝関節INT生成に股関節機能を利用できず，結果として膝関節の筋の負担が増大していること示唆された。<br>

【目的】歩行中の上肢運動は，能動的に制御されることで安定化し，歩行効率性に寄与している。しかし，上肢運動の適切な目標変数は明らかでない。本研究は，歩行中の上肢運動が,いかなる目標変数を基に制御されているかを明らかにすることを目的としてUncontrolled manifold（UCM）解析を行った。【方法】タスク変数として水平・鉛直方向の手先位置と速度を設定し，タスク変数に影響を及ぼさない良い変動（以下V_UCM），影響を及ぼす悪い変動（以下V_ORT）を求めた。【結果】手先位置をタスク変数とした場合は水平・鉛直方向ともに，1歩ごとの変動を抑えるような協調構造を有しなかった。手先速度をタスク変数とした場合は鉛直方向のみV_UCM＞V_ORTであり（p＜0.01），変動を抑える協調構造が存在した。【考察】歩行中の上肢運動においては，手先位置と比較して手先速度が制御の重要な変数である可能性を示唆した。<br>

【目的】本研究は健常人において，split-belt treadmill を用い，非対称歩行時の下肢の変化動態を運動学，及び運動力学的に明らかにすることを目的とした。【方法】健常成人10名に対し，ダブルベルトトレッドミル上で対称歩行中に左右 1:2 の速度比に変化し，再び対称に戻る歩行課題を行なった。この際の運動学，運動力学パラメータの左右対称性を速度変化時や変化前後で比較することで，適応反応や学習効果の残存を抽出した。【結果】ベルト速度が速側の下肢では後方伸展と推進力が増大していることが明らかとなった。【考察】これは先行研究で明らかになっている肢体間協調機能に起因して生じる速側下肢特有の動態であった可能性が示唆された。以上より，本研究は下肢の推進力や後方伸展の不全化を呈する対象者に対し，split-belt treadmillのリハビリテーションツールとしての理論確立の一端となったと考察する。<br>