Calcaneal inclination in children may influence their standing posture. However, the calcaneal inclination of modern children is unclear. This study aimed to clarify the characteristics of calcaneal inclination and its effects on spinal alignment and the center of pressure (COP) position in children. The study included 402 elementary school children (208 boys, 194 girls). The variables measured included calcaneal inclination, lower leg lateral inclination angle, spinal alignment, and COP position. The mean calcaneal inclination was 4.40 ± 3.5°, indicating mild eversion. Calcaneal inclination was classified into calcaneal eversion (+), calcaneal introversion (-), and a mid-heel position. Overall, 3.7% (15/402) of the subjects had bilateral calcaneal introversion (-), 18.2% (73/402) had unilateral calcaneal introversion (-), and 21.9% (88/402) had calcaneal introversion (-). An examination of the relationship between calcaneal inclination and each measured variable showed a significance level of <5% between calcaneal inclination and age, height, and body weight, but the correlation coefficients were <0.2 each, indicating little correlation. However, a significant correlation was found between right and left calcaneal inclination and the right and left lower leg lateral inclination angles. Overall, 21.9% (88/402) of the elementary school children had calcaneal inclination in a standing posture. These results suggest that calcaneal inclination may not affect spinal alignment and COP position.

Recently, poor posture (hyperkyphosis) has become a problem among children. This study investigated the effectiveness of an intervention (a spine mat) by measuring spinal alignment before and after the intervention in elementary school students. The study included 83 elementary school students. For the intervention, each participant was placed in a supine position on a bed and a spine mat was inserted ensuring that it adhered to the thoracic spine. The primary outcome variables included the thoracic kyphosis angle (TKA), upper thoracic angle, lower thoracic angle, lumbar lordosis angle (LLA), and sacral anteversion angle (SAA) measured in the standing and sitting positions using Spinal Mouse® before and after the intervention. Based on this evaluation, we assigned the participants to two groups: hyperkyphosis (n=25) and non-hyperkyphosis (n=58). Significant differences were observed between the pre-test and post-test TKA in the hyperkyphosis group in the standing position (pre-test: 45.3±4.5° and post-test: 40.8±9.0°, P<0.05). In the non-hyperkyphosis group, significant differences were observed between the pre-test and post-test LLA and SAA in the standing position. However, no significant difference was observed between the pre-test and post-test spinal alignment in the sitting position in both groups. The results of this study indicated that using a spine mat in elementary school children resulted in decreased TKA in the standing position only in the hyperkyphosis group, which exhibited a TKA of 40° or more after the intervention.

It has been reported that using of the spine mat increases chest expansion, inspiratory capacity (IC) and maximum inspiratory mouth pressure (PImax). However, no changes were observed in other respiratory functions and the respiratory muscle strength. The purpose of this study was to clarify the effects of pursed-lip breathing lying on the spine mat to the respiratory function and respiratory muscle strength. Forty-two adult male participants were assigned to two groups; an intervention group (IG group) of 21 participants who performed pursed-lip breathing on top of a spine mat and a control group (CG group) of 21 participants who performed pursed-lip breathing only. The intervention period was 5 days, and the respiratory features evaluated were chest expansion, respiratory function, respiratory muscle strength, and spinal alignment. A significant increase between the Pretest and the Posttest in chest expansion at the circumference of the axilla level, of the xiphoid process level and of the 10th rib level was observed only in IG group. For the respiratory function and the respiratory muscle strength, intervention group showed significant increases in percentage of vital capacity (%VC), tidal volume (TV), PImax, and maximum expiratory mouth pressure (PEmax). In the control group, only the TV indicated a significant increase. Regarding changes before and after the intervention, the intervention group showed significantly higher PImax and PEmax than the control group. No significant difference in spinal alignment was observed between the two groups. These results showed that pursed-lip breathing lying on the spine mat would increase the PImax, PEmax and the chest expansion.

Previous studies have reported that poor posture can induce various musculoskeletal disorders. Recently, poor posture in children has become a problem. This study aimed to determine the characteristics of sagittal spinal alignment in standing and sitting positions in elementary school students and how spinal alignment changes from standing to sitting position. Moreover, it clarifies how poor posture (hyperkyphosis) in the standing position affects sitting posture. This study was conducted among 83 elementary school students. The Spinal-Mouse® System was used to measure the thoracic kyphosis angle (TKA), upper thoracic angle (UTA), lower thoracic angle (LTA), lumbar lordosis angle (LLA), and sacral anteversion angle (SAA) in the standing and sitting positions. Hyperkyphosis was defined as a thoracic kyphosis angle of >40°. Participants were assigned to two groups: hyperkyphosis and non-hyperkyphosis. Significant differences were noted in all spinal alignment characteristics in both the positions. When spinal alignment was changed from standing to sitting, ΔUTA and ΔLTA correlated with ΔLLA and ΔSAA, respectively. A strong negative correlation was noted between ΔLLA and ΔSAA. In the sitting position, TKA, UTA, and LLA were significantly higher in the hyperkyphosis group than in the non-hyperkyphosis group. ΔUTA was significantly higher in the hyperkyphosis group than in the non-hyperkyphosis group when spinal alignment was changed from standing to sitting. The characteristics of sagittal spinal alignment in the sitting position were significantly different from those in the standing position. The study findings suggest that poor posture (hyperkyphosis) in the standing position affects the sitting posture.

Poor posture (thoracic hyperkyphosis) in children is reportedly caused by changes in their living environment. A previous study (conducted 30 years ago) reported that the position of the center of pressure (COP) in a child with an upright posture was approximately 40% from the heel. The present study aimed to determine the position and characteristics of the COP while standing in children aged 6–12 years. This study enrolled 83 elementary school students. A Win-Pod (Medicapteurs) platform was used to measure the COP. The COP position was expressed as a percentage from the heel as a relative ratio with a foot length of 100%. Spinal Mouse® was used to measure thoracic kyphosis, lumbar lordosis, sacral anteversion, and trunk inclination angles in the standing position. The COP position was 30.3±8.9% from the heel. We found positive correlations between the COP position, height, and weight. Further, the COP position was significantly more anterior in 28 upper elementary grade children (35.1 ± 9.2%) than in 25 middle (29.5 ± 8.6%) and 30 lower grade children (26.5 ± 6.7%). Regarding sex differences, the COP position was significantly more anterior in 46 boys (32.3 ± 9.8%) than in 37 girls (27.9 ± 6.9%). There was a weak positive correlation between the COP position and trunk inclination angle (r=0.251, p<0.05). Thus, we found that the COP position in modern children aged 6–12 years while standing was 30.3 ± 8.9% from the heel, indicating a shift toward the heel (backward) compared to that reported in previous studies.

To analyze the relationship of cause and effect between the onset of throwing disorders of the shoulder and decreased muscle strength, two studies were conducted at a baseball field. In study 1, shoulder joint muscle strength was measured when pain developed during practice and the relationship between pain onset and muscle strength was investigated. Decreased muscle strength was noted at the time of pain onset in 8.1% of players. Study 2 was a prospective study in which the relationship between changes in shoulder joint muscle strength from the start of pitching at the beginning of the season to one month later when competitive games began, and shoulder pain that appeared at the beginning of competitive games was analyzed. Based on the results, the possibility of shoulder joint muscle strength being a predictive factor for the onset of throwing disorders of the shoulder was investigated. However the pain group had greater muscle strength than the normal group at the beginning of the season. On the baseball field, the players’ throwing motions and joint function change daily, making it difficult to determine the reason for onset of disorders and injuries. These results suggest that onset of pain at the start of competitive games cannot be predicted from muscle strength at the beginning of the season.

The mandibular condyle formation during temporomandibular joint (TMJ) development exhibits endochondral bone formation, and the elongation process is dependent on the normal cartilage proliferation and differentiation. Retinoids are important for maturation of growth-plate chondrocytes, but the identity of their downstream effectors remains unclear. In this study, we carried out a series of studies at the cellular, biochemical, and molecular levels to determine whether, and if so how, retinoid signaling is related to the expression and function of Indian hedgehog (Ihh) in chondrocyte proliferation. First we analyzed the RA receptor (RAR) and Ihh expression pattern in E18 mandibular condyle. RARα and RARβ mRNA were characterized in the perichondrium around the condyle, whereas RARγ mRNA was expressed in the immature and prehypertrophic chondrocytes and the expression was overlapped with Ihh gene expression. Next we established a high-density culture model of chick cephalic chondrocytes in the prehypertrophic stage. We found that all-trans retinoic acid (RA) induced Ihh mRNA gene expression in this system. The RA pan-antagonist Ro 41-5253 inhibited both endogenous and RA-induced Ihh mRNA in a dose-dependent manner. The Ihh mRNA expression induced by RA required de novo protein synthesis, and was mediated by RARγ. Immunoblots showed that the prehypertrophic chondrocytes contained sizable levels of phosphorylated p38 mitogen-activated protein (MAP) kinase that were time- and dose-dependently increased by the RA treatment. Experimental p38 inhibition led to a severe drop in baseline and RA-stimulated Ihh expression. Exogenous recombinant Ihh stimulated the proliferation of proliferating chondrocytes, whereas RA inhibited the proliferation of these chondrocytes through p38 MAPK. Retinoids appear to play a primary role in controlling both the expression and function of Ihh in prehypertrophic chondrocytes and do so via p38 MAP kinase.