Relationships among body weight, joint moments generated during functional activities, and hip bone mass in older adults.

OBJECTIVE: To investigate the relationships among hip joint moments produced during functional activities and hip bone mass in sedentary older adults. METHODS: Eight male and eight female older adults (70-85 yr) performed functional activities including walking, chair sit-stand-sit, and stair stepping at a self-selected pace while instrumented for biomechanical analysis. Bone mass at proximal femur, femoral neck, and greater trochanter were measured by dual-energy X-ray absorptiometry. Three-dimensional hip moments were obtained using a six-camera motion analysis system, force platforms, and inverse dynamics techniques. Pearson's correlation coefficients were employed to assess the relationships among hip bone mass, height, weight, age, and joint moments. Stepwise regression analyses were performed to determine the factors that significantly predicted bone mass using all significant variables identified in the correlation analysis. FINDINGS: Hip bone mass was not significantly correlated with moments during activities in men. Conversely, in women bone mass at all sites were significantly correlated with weight, moments generated with stepping, and moments generated with walking (p<0.05 to p<0.001). Regression analysis results further indicated that the overall moments during stepping independently predicted up to 93% of the variability in bone mass at femoral neck and proximal femur; whereas weight independently predicted up to 92% of the variability in bone mass at greater trochanter. INTERPRETATION: Submaximal loading events produced during functional activities were highly correlated with hip bone mass in sedentary older women, but not men. The findings may ultimately be used to modify exercise prescription for the preservation of bone mass.

The Role of Foxo3 in Leydig Cells.

PURPOSE: Foxo3 in female reproduction has been reported to regulate proliferation of granulose cells that form follicles. There are no reports so far that discuss on the role of Foxo3 in males. This study was designed to outline the role of Foxo3 in the testes. MATERIALS AND METHODS: Testes from mice at birth to postpartum week (PPW) 5 were isolated and examined for the expression of Foxo3 using immunostaining. To elucidate role of Foxo3 in Leydig cells, R2C cells were treated with luteinizing hormone (LH) and the phosphorylation of Foxo3. Testosterone and steroidogenic acute regulatory (StAR) protein levels were measured after constitutive active [triple mutant (TM)] human FOXO3 adenovirus was transduced and StAR promoter assay was performed. RESULTS: Foxo3 expression in the testicles started from birth and lasted until PPW 3. After PPW 3, most Foxo3 expression occurred in the nuclei of Leydig cells; however, at PPW 5, Foxo3 was expressed in both the nucleus and cytoplasm. When R2C cells were treated with luteinizing hormone, Foxo3 phosphorylation levels by AKT increased. After blocking the PI3K pathway, LH-induced phosphorylated Foxo3 levels decreased, indicating that LH signaling regulates Foxo3 localization. When active FOXO3-TM adenovirus was introduced into a Leydig tumor cell line, the concentrations of testosterone and StAR protein decreased. When FOXO3 and a StAR promoter vector were co-transfected into HEK293 cells for a reporter assay, FOXO3 inhibited the StAR promoter. CONCLUSION: FOXO3 affects testosterone synthesis by inhibiting the formation of StAR protein. LH hormone, meanwhile, influences Foxo3 localization, mediating its function.

Lower-extremity biomechanics during forward and lateral stepping activities in older adults.

OBJECTIVE: To characterize the lower-extremity biomechanics associated with stepping activities in older adults. DESIGN: Repeated-measures comparison of kinematics and kinetics associated with forward step-up and lateral step-up activities. BACKGROUND: Biomechanical analysis may be used to assess the effectiveness of various 'in-home activities' in targeting appropriate muscle groups and preserving functional strength and power in elders. METHODS: Data were analyzed from 21 participants (mean 74.7 yr (standard deviation, 4.4 yr)) who performed the forward and lateral step-up activities while instrumented for biomechanical analysis. Motion analysis equipment, inverse dynamics equations, and repeated measures ANOVAs were used to contrast the maximum joint angles, peak net joint moments, angular impulse, work, and power associated with the activities. RESULTS: The lateral step-up resulted in greater maximum knee flexion (P<0.001) and ankle dorsiflexion angles (P<0.01). Peak joint moments were similar between exercises. The forward step-up generated greater peak hip power (P<0.05) and total work (P<0.001); whereas, the lateral step-up generated greater impulse (P<0.05), work (P<0.01), and power (P<0.05) at the knee and ankle. CONCLUSIONS: In older adults, the forward step-up places greater demand on the hip extensors, while lateral step-up places greater demand on the knee extensors and ankle plantar flexors. RELEVANCE: Clinicians may use data from biomechanical analyses of in-home exercises to more effectively target specific lower-extremity muscle groups when prescribing exercise activities for older adults. The forward step-up is recommended for maintaining or improving hip extensor performance; whereas, the lateral step-up is recommended when targeting the knee extensors and ankle plantar flexors.

Changes in gait patterns with rhythmic auditory stimulation in adults with cerebral palsy.

The objective is to evaluate the changes in gait patterns with rhythmic auditory stimulation (RAS) in adults with cerebral palsy (CP). Fourteen CP with bilateral spasticity participated in this study. A repeated-measures analysis of gait was performed in the presence and absence of RAS. Thirty healthy controls were also recruited. Each subject walked 10 m at their comfortable walking speed. Temporospatial data and kinematic parameters of gait were analyzed without RAS and with RAS. RAS was provided using a combination of a metronome beat set to the individual's cadence and rhythmic cueing from a live keyboard playing. Kinematic parameters, gait deviation index (GDI) as a measure of overall gait pathology, and asymmetry of temporospatial data were assessed. Gait analysis revealed that anterior tilt of pelvis and hip flexion during a gait cycle was significantly changed with RAS (p < 0.05), whereas there were no statistical differences in knee, ankle, and foot kinematic parameters. Additionally, the GDI exhibited a modest, but a statistically significant, improvement with RAS (p < 0.05). Based on ambulatory status, household ambulators showed that side-to-side asymmetry of step length as well as the GDI was significantly attenuated with RAS (p < 0.05). Walking with RAS resulted in kinematic changes of the pelvic and hip movement in spastic CP. Especially, the application of RAS immediately ameliorated overall gait pathology as well as temporospatial asymmetry in household ambulators. Therefore, RAS may be one of the therapeutic tools for gait training in adults with CP.

Biomechanics of the heel-raise exercise.

The purpose of this investigation was to determine whether increases in internal (muscular) demand would be proportional to increases in the external demand during heel-raise exercise. Seven male (mean age 74.9 +/- 4.8 years) and 9 female (mean age 74.4 +/- 5.1 years) older adults performed both double-leg heel raises and single-leg heel raises under 3 loading conditions (no external resistance and +5% and +10% of each participant's body weight). Kinematic and kinetic dependent variables were calculated using standard inverse-dynamics techniques. The results suggest that although the single-heel raise led to increases in peak net joint moments, power, and mechanical-energy expenditure (MEE), it did so at the expense of range of motion and angular velocity. In addition, increasing the external resistance by 5% of participants' body weight did not elicit significant changes in either the power or the MEE of the ankle joint. These effects should be considered when prescribing these exercises to older adults.