Influence of body mass normalization on the correlations between muscle cross-sectional area and physical performance outcomes in older women.

AIMS: Normalization is a method used to account for body mass in clinical practice and research. It is unclear if this method will improve the correlation between muscle cross-sectional area (CSA) and physical performance. We examined the correlations between quadriceps muscle morphology parameters and physical performance outcomes in older women. Material and methods: Twenty older women participated in this study. Ultrasound imaging was used to measure quadriceps muscle CSA and echo intensity. Muscle CSA was expressed as an absolute value (cm2) and as a relative value normalized to body mass (cm2/kg). Physical performance was assessed from timed up-and-go and 6-min walk tests. RESULTS: Relative CSA was significantly related to timed up-and-go scores (r=-0.489, p=0.029) and 6-min walking speed (r=0.606, p=0.005), whereas absolute CSA was not significantly associated with these performances (r=-0.231, p=0.327 and r=0.373, p=0.105). There was a significant correlation between absolute CSA and body mass (r=0.456, p=0.043). There were also significant correlations between echo intensity and timed up-and-go scores (r=0.556, p=0.011) and 6-min walking speed (r=-0.484, p=0.031). CONCLUSIONS:  Our study showed that relative CSA correlated better than absolute CSA with physical performance. These findings support the need to normalize measurements of muscle CSA to body mass in older adults.

Can handgrip strength measurements predict postural balance performance in older women?

OBJECTIVES: The link between handgrip strength and postural balance in older adults is not well understood. This study aimed to examine the correlations between postural balance performance and handgrip peak force and rate of force development (RFD) measurements in older women. METHODS: Twenty older women (67 ± 5 years) participated in this study. Handgrip contractions were used to assess peak force, peak RFD, and RFD at 0-100 (RFD100) and 0-200 (RFD200) ms. Postural balance was evaluated using a commercially designed balance testing device, which provides a measurement of static stability based on the sway index. RESULTS: There were significant correlations between sway index and handgrip peak force (r = -0.497, P = 0.026), peak RFD (r = -0.552, P = 0.012), RFD100 (r = -0.539, P = 0.014), and RFD200 (r = -0.499, P = 0.025). Stepwise multiple regression analysis indicated that handgrip peak RFD was the single best predictor of sway index (R2 = 0.305). The other variables, including peak force, did not add any unique variance to the stepwise prediction model. CONCLUSION: These findings suggest that handgrip strength, and in particular peak RFD, may be an effective parameter at predicting postural balance performance in older women.

Relationships between hamstring morphological characteristics and postural balance in elderly men.

OBJECTIVES: The link between hamstring morphology and postural balance performance in older adults is not well understood. This study aimed to examine the relationships between hamstring morphological characteristics of muscle size (cross-sectional area [CSA]) and quality (echo intensity [EI]) and postural balance with the eyes open and closed in elderly men. METHODS: Nineteen healthy elderly men (age= 73±4 years) participated in this study. Muscle CSA and EI were determined from ultrasound scans of the hamstrings. Postural balance was assessed with the eyes open and closed using a commercially designed balance testing device, which provides a measurement of static stability based on the sway index. RESULTS: The sway index with eyes closed was significantly related to muscle EI (r=0.474; P=0.040) but not CSA (r=0.021; P=0.932). The sway index with eyes open was not related to muscle CSA (r= -0.036; P=0.883) or EI (r=-0.079; P=0.747). CONCLUSIONS: The significant relationship observed between the sway index with eyes closed and muscle EI suggests that hamstring muscle quality may be a characteristic relevant to postural balance in the absence of visual feedback. These findings may provide important insight regarding the morphological mechanisms involved in maintaining balance and in the development of proper training programs aimed at improving postural stability in older individuals.

Acute effects of static stretching on passive stiffness and postural balance in healthy, elderly men.

OBJECTIVES: This study aimed to examine the acute effects of straight-leg raise (SLR) static stretching on passive stiffness and postural balance in healthy, elderly men. An additional aim of this study was to examine the relationships between stiffness and balance at baseline (prior to stretching) and the relationships between the stretch-induced changes in these variables. METHODS: Eleven elderly men (age = 69 ± 6 years; height = 177 ± 7 cm; mass = 83 ± 13 kg) underwent postural balance and passive stiffness assessments before and after: 1) a stretching treatment consisting of four, 15-s SLR static stretches performed by the primary investigator and 2) a control treatment consisting of no static stretching. Passive stiffness was calculated from the slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curve. Unilateral postural balance was assessed on the right leg using a commercially designed balance testing device, which provides a measurement of static stability based on the overall stability index (OSI). RESULTS: The slope coefficients and OSI values decreased from pre- to post-treatment for the stretching intervention (P = 0.015 and 0.018, respectively); however, there were no changes for the control (P = 0.654 and 0.920). For the stretching intervention, a significant positive relationship was observed between OSI and the slope coefficient of phase 1 at baseline (r = 0.619; P = 0.042). A significant positive relationship was also observed between the stretched-induced changes in OSI and the slope coefficient of phase 1 (r = 0.731; P = 0.011). No relationship was observed between OSI and the slope coefficient of phase 2 at baseline (r = 0.262; P = 0.437) nor was there a relationship between the changes in these variables (r = 0.419; P = 0.200). CONCLUSION: A short, practical bout of SLR static stretching may be an effective intervention for reducing passive stiffness and improving postural balance in healthy, elderly men.