Shinya Ogaya

Effects of balance training using wobble boards in the elderly.

Ogaya, S, Ikezoe, T, Soda, N, and Ichihashi, N. Effects of balance training using wobble boards in the elderly. J Strength Cond Res 25(9): 2616-2622, 2011—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.

Quickness of trunk movements in a seated position, regardless of the direction, is more important to determine the mobility in the elderly than the range of the trunk movement

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<0.01, APT r=-0.63, p<0.01, sitting reach test r=0.30, p<0.01). Moreover, multiple regression analysis revealed that SST and APT were independent indicators of both maximum gate speed and TUG, while the sitting reach test was not. These findings indicate that quickness, regardless of the direction of the movement, is more important than range in determining mobility in the elderly.

Surface electromyography activity of the rectus abdominis, internal oblique, and external oblique muscles during forced expiration in healthy adults

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<0.01) and internal oblique (p<0.01) showed significantly elevated activity compared with the rectus abdominis muscle. Furthermore, at 20% and 30% PEmax, the external oblique (p<0.05 and<0.01, respectively) and the internal oblique (p<0.05 and<0.01, respectively) showed significantly elevated activity compared with the rectus abdominis muscle. At 10% PEmax, no significant differences were observed in muscle activity. Although we observed no significant difference between 10% and 20% PEmax, activity during 30% PEmax was significantly greater than during 20% PEmax (external oblique: p<0.05; internal oblique: p<0.01). The abdominal oblique muscles are the most active during forced expiration. Moreover, 30% PEmax is the minimum intensity required to achieve significant, albeit very slight, muscle activity during expiratory resistance.

Maximum movement velocity of the upper limbs reflects maximum gait speed in community-dwelling adults aged older than 60 years.

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.

Effect of higher muscle coactivation on standing postural response to perturbation in older adults

BackgroundAlthough several studies have reported that muscle coactivation during postural control increases with age, the effect of higher muscle coactivation on standing postural response to perturbation is unknown.AimsTo investigate whether higher muscle coactivation affects standing postural response to perturbation in older adults.MethodsThirty-four community-dwelling older participants were randomly assigned either to the coactivation group (CG), where muscle coactivation was increased intentionally, or to the non-coactivation group (NCG). The participants were instructed to stand on a force plate that moved forward or backward. Electromyography data were collected from the lower leg muscles. We requested the participants in the CG to increase the activity of their tibialis anterior, and to maintain this posture during the tasks. We moved the force plate with a constant amplitude and velocity, and measured kinematic data with a camera during the tasks.ResultsDuring forward transfer, the knee extension and hip flexion decreased in the CG after perturbation compared to NCG, and the trunk extension angle increased. The center of pressure (COP) displacement decreased around the peak of the movement in the CG compared to NCG. During backward transfer, ankle dorsal and knee flexion changed after perturbation in the CG compared to NCG.Discussion and ConclusionOur study found that higher muscle coactivation inhibits lower limb and COP movement as well as increases trunk tilt and the risk for falls during forward perturbations. Postural control with higher coactivation appears to be inefficient for maintaining balance during the backward sway of posture.

The association between intersegmental coordination in the lower limb and gait speed in elderly females

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.

CONTRIBUTION OF MUSCLE TENSION FORCE TO MEDIAL KNEE CONTACT FORCE AT FAST WALKING SPEED

Fast walking is considered as a factor that causes pain in patients suffering from knee disorders. This study examined the effect of walking speed on the medial knee contact force and identified contributions to the muscle tension on the medial knee contact force during fast walking using musculoskeletal simulation analysis. The muscle contribution to the medial knee contact force was calculated based on the joint angles and ground reaction force for the normal and fast walking experiments of seven subjects. The muscle force and joint reaction force were used to estimate the medial knee contact force. Results showed, in average, 70% increase in medial knee contact force at the first peak and 34% increase at the second peak with a fast walking speed, compared to when they walked at a normal walking speed. The remarkable increase in the first peak was mainly contributed by the increase in the quadriceps force resisting the external knee flexion moment. In contrast, the moderate increase of second peak was contributed by the increase in the gastrocnemius muscle force. These results suggest that the increase in medial knee contact force at fast walking speeds is caused by the increased muscle force.

Carbon Dioxide Water Bathing Enhances Myogenin but Not MyoD Protein Expression after Skeletal Muscle Injury

[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.

Muscle contributions to center of mass excursion in ankle and hip strategies during forward body tilting

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.

Movement velocity is a sensitive risk factor of falls in high-functioning older adults.

To the Editor: Falls are a major public health problem for older adults and society. There are many risk factors for falls in older adults, such as age, gait, balance, muscle strength, and visual acuity. Above all, gait speed is a good predictor of falls. Because movement velocity of lower limbs is a strong predictor of gait speed, it may be useful as a predictor of falls. Movement velocity was measured to determine whether it has an influence on falls in healthy older adults. To clarify the characteristics of movement velocity itself, the velocity of the upper limbs and trunk was also measured.