Naohiko Kanemura

Contribution of knee adduction moment impulse to pain and disability in Japanese women with medial knee osteoarthritis.

BACKGROUND An increase in the knee adduction moment is one of the risk factors of medial knee osteoarthritis. This study examined the relationship between knee adduction moment and self-reported pain and disability. We also investigated the influence of pain on the relationships between knee adduction moment and gait performance and disability. METHODS Thirty-eight Japanese women with medial knee osteoarthritis participated in this study (66.37 years (41-79 years)). Gait analysis involved the measurement of the external knee adduction moment impulse in the stance duration and during 3 subdivisions of stance. The total, pain and stiffness, and physical function Japanese Knee Osteoarthritis Measure scores were determined. FINDINGS The pain and stiffness, physical function, and total scores were positively correlated with the knee adduction moment impulses in the stance duration, and initial and second double support interval, and single limb support interval. The knee adduction moment impulse during the stance duration was related to the pain and stiffness subscale and gait velocity. The pain and stiffness subscale was related to the physical function subscale. INTERPRETATION Our results suggest that increasing in the knee adduction moment impulse, a proxy for loading on the medial compartment of the knee, is related to increased pain during weight-bearing activities such as walking, thereby restricting walking performance and causing disability by reducing gait velocity. Thus, the reduction in the knee adduction moment impulse during gait may result in pain relief and may serve as a conservative treatment option with disease-modifying potential.

Effects of aging and exercise training on the histological and mechanical properties of articular structures in knee joints of male rat

The impact of aging on joints can have a profound effect on an individual’s functioning. Our objectives were to assess the histological and mechanical properties of the knee joint capsule and articular cartilage with aging, and to examine the effects of exercise on age-related changes in the knee joint. 2-year-old Wistar rats were divided into a sedentary control group and an exercise-trained group. 10-week-old animals were used to investigate the changes with aging. The joint capsule and cartilage were evaluated with histological, histomorphometric, immunohistochemical, and mechanical analyses. Severe degenerative changes in articular cartilage were observed with aging, whereas exercise apparently did not have a significant effect. The articular cartilage of aged rats was characterized by damage to the cartilage surface, cell clustering, and an abnormal cartilage matrix. Histomorphometric analysis further revealed changes in cartilage thickness as well as a decreased number of chondrocytes. Aging led to stiffness of the articular cartilage and reduced the ability to dissipate the load and distribute the strain generated within the joint. Joint stiffness with aging was independent of capsular stiffness and synovitis was not a characteristic feature of the aging joint. This study confirms that aging alone eventually leads to joint degeneration in a rat model. The lack of recovery in aging joint changes may be due to several factors, such as the duration of the intervention and the regeneration ability of the cartilage.

Effect of position of electrodes relative to the innervation zone onsurface EMG

We investigated the effect of the position of electrodes relative to the innervation zone (IZ) of the biceps brachii muscle during isometric elbow flexion using eight-channel surface array electrodes. We estimated the location of the IZ near the centre of the muscle in 20 male subjects. The pulse peaks from electromyogram (EMG) waveforms were detected for each channel and averaged, the triphasic pulse was determined, and the peak values of the first and third phases were compared. The results showed significantly greater pulse values for the first phase when the electrode placement was proximal to the estimated IZ, and for the third phase when the electrode placement was distal to the estimated IZ. Using this method, the positional relationship between electrodes and IZ can be determined using a surface EMG waveform recorded with a pair of bipolar electrodes. This method may be clinically useful in confirming the reliability of a recorded surface EMG.

Investigation of Innervation Zone Shift with Continuous Dynamic Muscle Contraction

Innervation zone (IZ) has been identified as the origin of action potential propagation in isometric contraction. However, IZ shifts with changes in muscle length during muscle activity. The IZ shift has been estimated using raw EMG signals. This study aimed to investigate the movement of IZ location during continuous dynamic muscle contraction, using a computer program. Subjects flexed their elbow joint as repetitive dynamic muscle contractions. EMG signals were recorded from the biceps brachii muscle using an eight-channel surface electrode array. Approximately 100 peaks from EMG signals were detected for each channel and summed to estimate the IZ location. For each subject, the estimated IZ locations were subtracted from the IZ location during isometric contractions with the elbow flexed at 90°. The results showed that the IZ moved significantly with elbow joint movement from 45° to 135°. However, IZ movement was biased with only a 3.9 mm IZ shift on average when the elbow angle was acute but a 16 mm IZ shift on average when it was obtuse. The movement of IZ location during continuous dynamic muscle contraction can be investigated using this signal processing procedure without subjective judgment.

Effect of Changing the Joint Kinematics of Knees With a Ruptured Anterior Cruciate Ligament on the Molecular Biological Responses and Spontaneous Healing in a Rat Model.

Background: The poor healing capacity of a completely ruptured anterior cruciate ligament (ACL) has been attributed to an insufficient vascular supply, cellular metabolism, and deficient premature scaffold formation because of the unique intra-articular environment. However, previous studies have focused on intra-articular factors without considering extra-articular factors, including the biomechanical aspects of ACL-deficient knees. Hypothesis: Changing the joint kinematics of an ACL-ruptured knee will improve cellular biological responses and lead to spontaneous healing through the mechanotransduction mechanism. Study Design: Controlled laboratory study. Methods: A total of 66 skeletally mature Wistar rats were randomly assigned to a sham-operated group (SO), ACL-transection group (ACL-T), controlled abnormal movement group (CAM), and an intact group (IN). The ACL was completely transected at the midportion in the ACL-T and CAM groups, and the CAM group underwent extra-articular braking to control for abnormal tibial translation. The SO group underwent skin and joint capsule incisions and tibial drilling, without ACL transection and extra-articular braking. The animals were allowed full cage activity until sacrifice at 1, 2, 4, 6, and 8 weeks postoperatively for histological, molecular biological, and biomechanical assessment. Results: All injured ACLs in the ACL-T group were not healed, but those in the CAM group healed spontaneously, showing a typical ligament healing response. Regarding the molecular biological response, there was an upregulation of anabolic factors (ie, transforming growth factor–β) and downregulation of catabolic factors (ie, matrix metalloproteinase). Examination of the mechanical properties at 8 weeks after injury showed that >50% of the strength of the intact ACL had returned. Conclusion: Our results suggest that changing the joint kinematics of knees with a ruptured ACL alters the molecular biological responses and leads to spontaneous healing. These data support our hypothesis that the mechanotransduction mechanism mediates molecular responses and determines whether the ACL will heal. Clinical Relevance: Elucidating the relationship between the mechanotransduction mechanism and healing responses in knees with completely ruptured ACLs may result in the development of novel nonsurgical treatment that enables the ACL to spontaneously heal in patients who are not suitable for reconstruction.

Immediate effect of passive and active stretching on hamstrings flexibility: a single-blinded randomized control trial

[Purpose] This study compared the efficacy of passive and active stretching techniques on hamstring flexibility. [Subjects] Fifty-four healthy young subjects were randomly assigned to one of three groups (2 treatment groups and 1 control group). [Methods] Subjects in the passive stretching group had their knees extended by an examiner while lying supine 90° of hip flexion. In the same position, subjects in the active stretching group extended their knees. The groups performed 3 sets of the assigned stretch, with each stretch held for 10 seconds at the point where tightness in the hamstring muscles was felt. Subjects in the control group did not perform stretching. Before and immediately after stretching, hamstring flexibility was assessed by a blinded assessor, using the active knee-extension test. [Results] After stretching, there was a significant improvement in the hamstring flexibilities of the active and passive stretching groups compared with the control group. Furthermore, the passive stretching group showed significantly greater improvement in hamstring flexibility than the active stretching group. [Conclusion] Improvement in hamstring flexibility measured by the active knee-extension test was achieved by both stretching techniques; however, passive stretching was more effective than active stretching at achieving an immediate increase in hamstring flexibility.

Exercise enhances cognitive function and neurotrophin expression in the hippocampus accompanied by changes in epigenetic programming in senescence-accelerated mice

Aerobic exercise is known to increase expression of neurotrophins, particularly brain-derived neurotrophic factor (BDNF), in the hippocampus and to improve cognitive function. Exercise exerts neuroprotective effects in the hippocampus by inducing epigenetic changes, which play crucial roles in aging and neurodegenerative diseases. Specifically, the activity levels of histone acetyltransferases (HATs) and histone deacetylases (HDACs) regulate histone acetylation and modulate gene transcription. The objective of the present study was to assess the interactive effects of exercise and aging on cognitive function, expression of neurotrophins (BDNF and neurotrophin-4) and their receptors (tyrosine receptor kinase B and p75), and epigenetic regulations, including the activity of HATs and HADCs in the hippocampus. We used the senescence-accelerated mouse (SAM) model, specifically 13-month-old SAM resistant 1(SAMR1) and SAM prone 1 (SAMP1) lines. Mice were distributed into four groups based on accelerated senescence and exercise status. Mice in the exercise groups exercised on a treadmill for approximately 60min a day, 5days a week. Aerobic exercise for 4 weeks improved cognitive function, accompanied by an increase in BDNF expression and a decrease in p75 transcription in both SAMR1 and SAMP1. In addition, the exercise regimen activated both HAT and HDAC in the hippocampus. Therefore, the present study reveals that despite accelerated senescence, long-term exercise improved cognitive function, upregulated the expression of BDNF, and downregulated p75, a receptor involved in apoptotic signaling. Furthermore, long-term exercise enhanced activity of both HAT and HDAC, which may contribute to the transcriptional regulation underlying the improvement of cognitive function.

Estimation of inertial parameters of the lower trunk in pregnant Japanese women: A longitudinal comparative study and application to motion analysis.

We aimed to quantify the inertial parameters of the lower trunk segment in pregnant Japanese women and compare kinetic data during tasks calculated with parameters estimated in this study to data calculated with standard parameters. Eight pregnant women and seven nulliparous women participated. Twenty-four infrared reflective markers were attached to the lower trunk, and the standing position was captured by eight infrared cameras. The lower trunk was divided into parts, and inertial parameters were calculated. Pregnant women performed a movement task that involved standing from a chair, picking up plates, and walking forward after turning to the right. Kinetic analysis was performed using standard inertial parameters and the newly calculated parameters. There were more significant differences between methods in the kinetic data at the latter stages of pregnancy. The inertial parameters calculated in this study should be used to ensure the validity of biomechanical studies of pregnant Japanese women.

A novel approach for evaluating nerve function in healthy elderly persons: A pilot study

Background Motor nerve function decreases with age and can cause abnormalities in motor function. Using newly designed methods, we used evoked electromyograms to evaluate change in motor nerve function. Material/Methods Motor function was assessed by grip strength, timed up-and-go test, 5-m normal walk, and 5-m fastest walk. In addition, motor nerve conduction velocity was calculated by measuring latency differences (NCV) in elderly and young subjects. We also investigated motor nerve conduction velocity by correlation coefficient (NCVCC) and the difference between NCV and NCVCC (DNCV). Results Significant differences were observed in the motor function of elderly and young persons in grip strength, the timed up-and-go test, and the 5-m fastest walk; however, no difference was observed in the 5-m normal walk test. NCVCC was lower than NCV in both elderly and young. The correlation coefficient peak of the NCVCC calculation was lower in elderly than in young. A negative correlation was observed between correlation coefficient peak and DNCV in elderly subjects. Conclusions NCVCC compares the overall shape of compound muscle action potential and reflects not only the fastest motor unit, but also the motor nerve conduction velocity of other motor unit components. A significant negative correlation between DNCV and the correlation coefficient peak was observed only in elderly subjects, suggesting that older individuals, including those that maintain a high level of physical strength, experience a loss of motor nerve function. Thus, changes in motor nerve function among elderly persons can potentially be further examined for clinical use.

Controlling Abnormal Joint Movement Inhibits Response of Osteophyte Formation

Objective Osteoarthritis (OA) is induced by accumulated mechanical stress to joints; however, little has been reported regarding the cause among detailed mechanical stress on cartilage degeneration. This study investigated the influence of the control of abnormal joint movement induced by anterior cruciate ligament (ACL) injury in the articular cartilage. Design The animals were divided into 3 experimental groups: CAJM group (n = 22: controlling abnormal joint movement), ACL-T group (n = 22: ACL transection or knee anterior instability increased), and INTACT group (n = 12: no surgery). After 2 and 4 weeks, the knees were harvested for digital microscopic observation, soft X-ray analysis, histological analysis, and synovial membrane molecular evaluation. Results The 4-week OARSI scores showed that cartilage degeneration was significantly inhibited in the CAJM group as compared with the ACL-T group (P < 0.001). At 4 weeks, the osteophyte formation had also significantly increased in the ACL-T group (P < 0.001). These results reflected the microscopic scoring and soft X-ray analysis findings at 4 weeks. Real-time synovial membrane polymerase chain reaction analysis for evaluation of the osteophyte formation–associated factors showed that the mRNA expression of BMP-2 and VEGF in the ACL-T group had significantly increased after 2 weeks. Conclusions Typically, abnormal mechanical stress induces osteophyte formation; however, our results demonstrated that CAJM group inhibited osteophyte formation. Therefore, controlling abnormal joint movement may be a beneficial precautionary measure for OA progression in the future.