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The functional importance of trunk muscle strength for running movement is widely recognised, but the kinematic effects of undertaking specific training are unclear. This study investigated the change in joint angle and its variability during running following trunk muscle training. Eighteen young female and novice runners participated. Using Plug-in-gait model with infrared markers attached to the body surface, the lower limb and lumber angles during running were measured, and the variability was examined by calculating the coefficient variation and Lyapunov exponent. Measurements of trunk endurance were also performed. Over four weeks of training, the subjects performed trunk muscle endurance trainings three times a week. Following this intervention, trunk endurance was found to have significantly increased. The Lyapunov exponent of lumbar flexion-extension angle also significantly increased. Moreover, a decreased range of the ankle angle and increased range of the hip angle were observed following the training. These results demonstrate that the trunk training promoted adjustments to lumbar movement and altered the movement patterns of the participants' lower limbs during running.

Improper footwear can lead to painful knee and functional limitations for knee osteoarthritis (OA) patients. This study aimed to examine the use of different footwear types in Japanese knee OA and ...

Background Accumulating evidence indicates that abnormal foot posture are risk factors for knee osteoarthritis (OA). However, the relationship between foot posture and tibiofemoral contact force (CF) during habitual weight-bearing activities remains unclear. This study aimed to determine the association between tibiofemoral CF and foot posture while walking. Methods In total, 18 patients with knee OA and 18 healthy individuals participated in this cross-sectional study. Foot parameters were evaluated by Foot Posture Index (FPI), Staheli Arch Index (SAI), hallux valgus angle, calcaneus inverted angle relative to the floor as a static rearfoot posture, navicular height, and toe grip strength. In addition, all participants underwent kinetic and kinematic measurements during a self-selected speed gait. The measurement device used was the three-dimensional motion analysis system with a sampling rate of 120 Hz. The musculoskeletal model, which has 92 Hill-type muscle–tendon units with 23 degrees of freedom, was used to calculate tibiofemoral CF. Partial correlations was used to investigate the association between foot parameters and total, medial, and lateral tibiofemoral CF of the first and second peaks while controlling for gait speed. Results A significant negative correlation was observed between Walking SAI and first peak medial tibiofemoral CF in control participants (r = -0.505, p = 0.039). SAI was also significantly positively correlated with first peak medial tibiofemoral CF in patients with knee OA (r = 0.482, p = 0.042). Conclusions Our findings revealed a correlation between the medial first peak tibiofemoral CF and the SAI. This study indicates that people with knee OA and flatfoot have excessive first medial tibiofemoral CF during walking.

The aim of this study was to analyze individual muscle contributions to knee angular acceleration using a musculoskeletal simulation analysis and evaluate knee extension mechanics in the early stance phase in patients with knee osteoarthritis (OA). The subjects comprised 15 patients with medial knee OA and 14 healthy elderly individuals. All participants underwent gait performance test using 8 infrared cameras and two force plates to measure the kinetic and kinematic data. The simulation was driven by 92 Hill-type muscle-tendon units of the lower extremities and a trunk with 23° of freedom. We analyzed each muscle contribution to knee angular acceleration in the 5%-15% and 15%-25% periods of the stance phase (% SP) using an induced acceleration analysis. We compared accelerations by individual muscles between the two groups using an analysis of covariance for controlling gait speed. Patients with knee OA had a significantly lesser knee extension acceleration by the vasti muscles and higher knee acceleration by hip adductors than those in controls in 5-15% SP. In addition, knee OA resulted in significantly lesser knee extension acceleration by the vasti muscles in 15-25% SP. These results indicate that patients with knee OA have decreased dependency on the vasti muscles to control knee movements during early stance phase. Hip adductor muscles, which mainly control mediolateral motion, partly compensate for the weak knee extension by the vasti muscles in patients with knee OA.

We aimed to characterize rectus abdominis, internal oblique, and external oblique muscle activity in healthy adults under expiratory resistance using surface electromyography. We randomly assigned 42 healthy adult subjects to 3 groups: 30%, 20%, and 10% maximal expiratory intraoral pressure (PEmax). After measuring 100% PEmax and muscle activity during 100% PEmax, the activity and maximum voluntary contraction of each muscle during the assigned experimental condition were measured. At 100% PEmax, the external oblique (p

Many individuals with knee osteoarthritis (OA) generate low forward center of mass (COM) acceleration during the late stance phase, consequently making it difficult to walk fast. This study analyzed individual muscle contributions to forward COM acceleration and the muscle potential (i.e., acceleration by unit force) to clarify whether reduced acceleration was related to decreased muscle potential of forward progression by the triceps sure. Twelve individuals with knee OA and 12 healthy age-matched individuals participated in this study. All participants underwent kinetic measurements during normal gait. The simulation involved 92 Hill-type muscle-tendon units with 23 degrees of freedom. We analyzed how each muscle contributed to forward COM acceleration during the 70-100% stance phase using an induced acceleration analysis. Next, the muscle potential of forward COM acceleration was calculated. Our results showed that individuals with knee OA had significantly lower forward COM acceleration with the soleus, gastrocnemius, and iliopsoas muscles compared with controls. Lower muscle potential in the soleus was found in those with knee OA. These findings implied that improving the contribution of the soleus to forward body progression would be effective for increasing the gait speed of those with knee OA during the late stance phase.

Toe-out angle alternation is a potential tactic for decreasing the knee adduction moment during walking. Published reports have not examined the medial knee contact force during the toe-out gait, although it is a factor affecting knee articular cartilage damage. This study investigated the effects of increased toe-out angle on the medial knee contact force, using musculoskeletal simulation analysis. For normal and toe-out gaits in 18 healthy subjects, the muscle tension forces were simulated based on the joint moments and ground reaction forces with optimization process. The medial knee contact force during stance phase was determined using the sum of the muscle force and joint reaction force components. The first and second peaks of the medial knee contact force were compared between the gaits. The toe-out gait showed a significant decrease in the medial knee contact force at the second peak, compared with the normal gait. In contrast, the medial knee contact forces at the first peak were not significantly different between the gaits. These results suggest that the toe-out gait is beneficial for decreasing the second peak of the medial knee contact force.

Objective: Lower limb movement velocity is a good predictor of mobility in older adults. The movement velocities of the trunk and upper limbs are also good determinants of mobility. However, the reason for this is not clear, possibly because the basic characteristics of the movement velocities are still unclear. To investigate these characteristics, we evaluated the associations between the movement velocities of all three body regions and between these velocities and mobility measurements. Methods: One hundred twelve community-dwelling older adults (mean age 74.1 years) participated in this study. We measured the movement velocities (lower limbs, upper limbs and trunk), muscle strength (knee extensor, trunk extensor and plantar flexor), mobility measures (gait speed and timed up and go test (TUG)), and gait parameters (step length and cadence). Results: All movement velocities were moderately correlated with each other (r=-0.42 to 0.61). All movement velocities were also significantly associated with mobility to the same degree as muscle strength (gait speed r=-0.42 to 0.51, TUG r=-0.37 to 0.57). A stepwise regression analysis revealed that the movement velocities of the upper and lower limbs were significant predictors of gait speed, while that of the trunk was an independent predictor of TUG. Movement velocities were associated with step length more than with cadence. Conclusion: These findings indicate that movement velocities can be treated as individual values and considered good indicators of mobility in older adults, regardless of body region.

OBJECTIVE: The tissue destruction around knee joint is considered to involve medial knee contact force overload. However, no report has examined the relationship between the medial knee contact force and dysfunction. In this study, we investigated the medial knee contact force during gait in elderly subjects using musculoskeletal model-based simulation analysis and revealed its connection with pain and dysfunction. METHODS: We separated 122 elderly participants into 2 groups, the pain group and non-pain group, according to the existence of knee pain. Medial knee contact force was calculated based on the previously published inverse dynamics solution for normal walking. The muscle and joint reaction forces were used to determine the medial knee contact force during the stance phase. Japanese knee osteoarthritis measurement was used to assess the severity of symptoms for knee pain subjects. RESULTS: The medial knee contact force was significantly correlated with total Japanese knee osteoarthritis measurement scores and subscale dysfunction scores for pain subjects, although there was no difference in the medial knee contact force between the 2 groups. CONCLUSION: An increased medial knee contact force during gait might relate to dysfunction among elderly individuals with knee pain.

External knee adduction moment has been studied as a surrogate for medial knee contact force. However, it is not known whether adduction moment is a rational measure for predicting medial knee contact force. The aim of this study was to investigate the correlation between knee adduction moment and medial knee contact force in older people, using musculo-skeletal simulation analysis. One hundred and twenty-two healthy older subjects participated in this study. Knee moment and medial knee contact force were calculated based on inverse dynamics analysis of normal walking. Muscle force and joint reaction force were used to determine the medial knee contact force during stance phase. The results showed that the maximum medial knee contact force was moderately correlated to the maximum knee adduction (r = 0.59) as well as the maximum extension moment (r = 0.60). The first peak of medial knee contact force had a significant strong correlation with the first peak of adduction moment and a moderate correlation with the maximum flexion moment. The second peak of medial knee contact force had a significant moderate correlation with both the second peak of adduction and the maximum extension moment. These results implied that the maximum adduction moment value could be used, to some extent, as a measure of the maximum medial knee contact force.

Aim A number of studies have shown that the maximum movement velocity of the lower limbs is a critical determinant of gait speed in elderly adults. However, it is still unclear whether gait speed is associated with the movement velocity of the lower limbs or the movement velocity itself. Therefore, we measured the movement velocity of upper limbs that would not have a direct effect on gait, and examined the relationship between the movement velocity and gait speed. Methods A total of 76 community-dwelling adults aged older than 60 years (mean age 73.3 years) participated in the study. We measured the movement velocity of the upper limbs, maximum gait speed, quadriceps strength, trunk muscle endurance and skeletal muscle mass index. Results A significant correlation was found between the movement velocity of the upper limbs and maximum gait speed (r = 0.47; P

Few studies have examined balance training of elderly people using wobble boards. This study assessed the effects of wobble board balance training on physical function in institutionalized elderly people. This study examined 23 subjects (age 84.2 ± 5.9 years) who lived in a nursing home. The exercise program for the training group comprised balance training standing on a wobble board for 9 weeks, twice a week. In all, 11 training group subjects and 11 control group subjects completed this study. After 9 weeks, standing time on a wobble board, standing time on a balance mat, and maximum displacement distance of anterior-posterior center of pressure in the training group were significantly greater than those of the control group. Frequency analysis revealed that the power spectrum in 0.1-0.2 Hz significantly increased in the training group. These results suggest that wobble board training is effective for elderly people to improve their standing balance, by which they frequently control their center of gravity and maintain a standing posture on unstable surface conditions.

Human multi-segmental motion is a complex task requiring motor coordination. Uncoordinated motor control may contribute to the decline in mobility; however, it is unknown whether the age-related decline in intersegmental coordination relates to the decline in gait performance. The aim of this study was to clarify the association between intersegmental coordination and gait speed in elderly females. Gait measurements were performed in 91 community-dwelling elderly females over 60 years old. Foot, shank, and thigh sagittal motions were assessed. Intersegmental coordination was analyzed using the mean value of the continuous relative phase (mCRP) during four phases of the gait cycle to investigate phase differences in foot-shank and shank-thigh motions during a normal gait. The results showed that foot-shank mCRP at late stance had negative correlations with gait speed (r=-0.53) and cadence (r=-0.54) and a positive correlation with age (r=0.25). In contrast, shank-thigh mCRP at late stance had positive correlations with gait speed (r=0.37) and cadence (r=0.56). Moreover, partial correlation, controlling age, height, and weight, revealed that foot-shank mCRP at late stance had negative correlations with gait speed (r=-0.52) and cadence (r=-0.54). Shank-thigh mCRP at late stance had a positive correlation with gait speed (r=0.28) and cadence (r=0.51). These findings imply that the foot-shank and shank-thigh coordination patterns at late stance relate to gait speed, and uncoordinated lower limb motion is believed to be associated with the age-related decline in cadence.

Introduction: The purpose of this study was to characterize the rectus abdominis (RA), external oblique (EO), and internal oblique (IO)muscle activity level in healthy adults under expiratory resistance to expose the limitations of conventional expiratory muscle training. Methods: A total of 37 healthy adult subjects were randomly assigned to one of three groups: 30% of maximal expiratory intraoral pressure (30% PE max) group, 20% PE max group, and 10% PE max group. The RA, EO, and IO muscle activity level were measured during maximum voluntary contraction and during performed forced expiration under the assigned condition afrer measurement of maximal expiratory intraoral pressure (100% PE max) and muscle activity level during 100% PE max for all subjects. Results: At 100% PE max, the EO ( P P P P P P P P Conclusion: The two abdominal oblique muscles are the most active during forced expiration. Moreover, 30% PE max is the minimum intensity required to achieve significant muscle activity when expiratory resistance is applied, but the muscle activity obtained at 30% PE max is very small.

Humans employ two distinct strategies to maintain balance during standing: the ankle and hip strategies. People with a high fall risk tend to alter their motion patterns during forward body tilting from a hip to an ankle strategy. Improved knowledge regarding how muscles control the center of mass (COM) during balancing would facilitate clinical assessment. The present study aimed to investigate individual muscle contributions to COM motion during forward body tilting with both ankle and hip strategies in 16 healthy adults. While standing, participants were instructed to oscillate their bodies and touch anterior and posterior targets at 0.5Hz. The anterior target was positioned at the sternum height level in a HIGH and 5% lower in a LOW condition to induce ankle and hip strategies, respectively. The muscle tension force was calculated from measured angle data using a two-dimensional, muscle-driven forward simulation model. Muscle contributions to COM acceleration during forward body tilting were calculated via induced acceleration analysis. Long hamstrings were found to increase upward-contributing action and forward COM acceleration in the LOW condition during forward tilting. In contrast, the contribution of the soleus to backward COM acceleration was reduced. These results imply that the contribution of hamstrings to forward COM acceleration is disadvantageous to fore-aft COM control and balance recovery during forward body tilting.

[Purpose] We reported that carbon dioxide (CO2) water bathing accelerates skeletal muscle regeneration; however, the underlying mechanism was unclear. MyoD and myogenin play roles in muscle regeneration, and the purpose of this study was to determine changes in MyoD and myogenin caused by CO2 water bathing after injury. [Subjects] Sixteen female Wistar rats (n = 4 per group) were used. [Methods] The rats were divided into four groups: no-injury (NI), injury (IC), injury + tap water bathing (ITW), and injury + CO2 water bathing (ICO2). Muscle injury was induced by injection of bupivacaine hydrochloride into the left tibial anterior (TA) muscles. Tap water and CO2 (1,000 ppm) water bathing were performed at 37 °C for 30 minutes once a day. The left TA muscles were removed 4 days after injury, and the expressions of MyoD and myogenin were measured. [Results] MyoD and myogenin were increased in the IC, ITW, and ICO2 groups compared with the NI group. Although the MyoD level was similar in the IC, ITW, and ICO2 groups, myogenin increased more in the ICO2 group than in the IC and ITW groups. [Conclusion] CO2 water bathing after muscle injury appears to induce an increase in the expression of myogenin.

[Purpose] Accuracy in coordinating limb movements decreases with aging. The effect of aging on the variability of cyclic movements is not well known. The aim of this study was to examine the effect of aging on seated stepping variability. [Subjects and Methods] Twenty-six healthy young adults and 15 healthy elderly adults were instructed to walk at their preferred speed. Foot contact was monitored using reflective markers. Seated stepping was performed on force plates. The participants synchronized their stepping with 6 different metronome beats: 90–140 beats per minute (bpm). The time-series coefficient of variation (CV) was calculated. [Results] The cadence of young adults was 121 steps/min and that of the elderly adults was 125 steps/min in the elderly adults. The seated stepping CV decreased gradually from 90 to 120 bpm, but sharply increased at 130 and 140 bpm. Compared to young adults, the elderly adults had significantly higher CVs of seated stepping; however, the intergroup difference in the CV of seated stepping at 120 bpm was negligible. [Conclusions] Our results suggest that the stepping accuracy of the elderly is decreased; however, the rhythmic seated stepping accuracy does not decrease at the same rate as gait.

This study aimed to determine the effect of muscle co-contraction on balance recovery by using a simulation model. The muscle-driven forward simulation model included an inverted pendulum with two ankle muscles, a plantar flexor muscle (PF), and a dorsal flexor muscle (DF). The model was created based on experimental data obtained from balance recovery after applying backward platform translation to a standing elderly woman. Baseline simulation was performed using this model. Additionally, we performed two simulations with increased DF excitation at the same level of simulation and at the same pattern of simulation. The same level of simulation had the same PF excitation level as the baseline simulation with increased DF excitation. The same pattern simulation had the same increased or decreased PF excitation pattern but with a constant increase in PF excitation level to offset the increased DF excitation. Our results revealed that the same pattern simulation decreased the maximum dorsal flexion angle after platform translation. During the same level of simulation, the insufficient PF force used to recover balance resulted in a forward fall. These results imply that co-contraction is an effective strategy for recovering balance at the expense of additional muscle excitation in the elderly.

A number of studies have shown that the maximum movement velocity of the lower limbs is a critical determinant of gait speed in elderly adults. However, it is still unclear whether gait speed is associated with the movement velocity of the lower limbs or the movement velocity itself. Therefore, we measured the movement velocity of upper limbs that would not have a direct effect on gait, and examined the relationship between the movement velocity and gait speed.A total of 76 community-dwelling adults aged older than 60 years (mean age 73.3 years) participated in the study. We measured the movement velocity of the upper limbs, maximum gait speed, quadriceps strength, trunk muscle endurance and skeletal muscle mass index.A significant correlation was found between the movement velocity of the upper limbs and maximum gait speed (r=0.47; P0.01). In a stepwise multiple regression analysis using maximum gait speed as a dependent variable, age, movement velocity of the upper limbs, body mass index and quadriceps strength were selected as independent variables (R(2)=0.55, P0.001).The movement velocity of the upper limbs is a significant determinant of maximum gait speed, suggesting that the ability to move any region rapidly might be a critical factor in maximum gait speed.

Although trunk function is known to be critical for maintaining balance during gait, a detailed evaluation regarding the relationship between trunk function and mobility has not been performed. We previously reported that the ability of quick lateral trunk movements in a seated position reflects mobility in elderly people. In this study, we further examined whether trunk movement in the anterior-posterior direction is also a determinant of mobility. In addition, the correlation between range of lateral trunk movement and mobility was also examined. One hundred and forty community-dwelling elderly participants (73.3±6.2 years) were enrolled in this study. We performed various trunk movement tests in a seated position, such as the seated side tapping test (SST), the seated anterior-posterior tapping test (APT), and the lateral sitting functional reach test (sitting reach test). Maximum gait speed and the timed up and go test (TUG) were performed to determine mobility. Parameters of trunk movement were compared. SST and APT showed moderate significant correlations with both maximum gate speed and TUG, while the sitting reach test weakly correlated (SST r=-0.58, p