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Biomedical subjects

Karl S Rosengren

Publications and source records attributed to Karl S Rosengren.

11 recordsLinked to original sources
PubMed2006

Effect of Tai Chi on gait and obstacle crossing behaviors in middle-aged adults.

This study investigated whether long-term, habitual practice of Tai Chi (or Taiji) results in behavioral modifications during gait. Specifically, we examined whether Tai Chi (TC) experience alters gait behavior during normal and obstructed walking. Fifteen experienced TC practitioners and fifteen control subjects (average age 45 years, 23-66 year range) completed level walking trials with or without a stationary obstacle placed in their path. TC practitioners in this study had an average of 6.5 years (1.5-15 year range) of Chen-style Tai Chi experience. Kinematic analyses performed on their step-to-step gait characteristics over multiple steps revealed that TC practitioners used a more cautious strategy by using slower gait speeds and shorter and slower steps than controls (p <or= 0.003). TC practitioners also spent significantly longer time in single leg support while crossing the obstacle (p < 0.001). The deleterious effect of this typically risky behavior may be mitigated in TC practitioners because of their comfort with single leg stance due to continual practice in this posture. It has been suggested that TC may reduce the risk of falls in older adults. Future studies will need to determine whether these observed gait behaviors are found in older adults and are related to reductions in fall risk.

Accidental Falls↗
PubMed2006

Changing control strategies during standard assessment using computerized dynamic posturography with older women.

The goal of this investigation was to explore the use of spectral analysis to examine the data obtained during computerized dynamic posturography (CDP). In particular, we examined whether spectral analysis would provide more detailed information about underlying postural control strategies and potential learning across conditions and trials of the sensory organization test (SOT). Twenty older women between the ages of 60 and 72 (mean=65.2) were assessed using standard testing protocol. Participants showed significant improvements from the first to the second trials in their equilibrium scores in the more difficult conditions. This finding was reflected in the spectral analysis data by a shift in the frequency distribution towards greater power in the lower frequency range. This frequency change likely reflects a change in the ankle strategy used to maintain balance during the more difficult conditions.

Aged↗
PubMed2006

Generalizability of center of pressure measures of quiet standing.

Center of pressure (COP) measures are commonly used as indicators of balance and postural control. At present, there are no universally accepted standards in research investigating fluctuations in the COP with regard to the number of trials or the length of a given trial. The purpose of this study was to use the tools of Generalizability Theory (G-Theory) to investigate the reliability of COP measures of quiet standing and to establish an optimal measurement protocol. G-Theory provides a tool that allows us to break down the sources of variation, or facets, in a measurement procedure and ultimately design a protocol that provides optimal reliability. Fifteen participants completed 10 90-s trials with eyes open and closed. COP measures of anterior-posterior standard deviation (SD(AP)), medial-lateral SD (SD(ML)), average velocity (Vel), and 95% confidence ellipse area (Area) were calculated using the first 30, 60, and 90s of each trial. A G-study and follow-up D-studies were performed to estimate reliability coefficients (G-coefficients). The results of the G-Theory analysis suggest that these COP measures reached acceptable levels of reliability (G>or=0.70) with at least five 60s trials.

Adult↗
PubMed2005

Ultrasound of the calcaneus and bone mineral density differs in older black and white women but is not impacted by current physical activity.

Black women have lower fracture rates, primarily due to bone-dependent factors; however, the racial differences in quantitative ultrasound (QUS) for older black and white women are poorly characterized, especially in regard to the mediating effects of physical activity. The primary aim of this study was to determine if QUS measures differ in age- and body-size-matched older black and white women and to explore if the racial differences were mediated by differences in current habitual physical activity. We performed dual-energy X-ray absorptiometry (DXA) bone mineral density (BMD) measures and QUS measures [broadband ultrasound attenuation (BUA), speed of sound (SOS), quantitative ultrasound index (QUI)] of the calcaneus in 30 black and 30 white women matched in age (68.3 years) and body mass index (30.0 kg/m2). Black women had greater QUS measures of SOS (1,563.6+/-31.7 vs 1,541.2+/-23.4, p=0.003) and QUI (102.6+/-18.5 vs 90.4+/-15.4, p=0.008), with a strong trend for greater BUA (79.2+/-15.1 vs 71.9+/-15.1 m/sec, p=0.066) compared with white women. As expected, black women had greater BMD measures at all sites; whole body (6.8%, p<0.010), lumbar spine (10.4%, p=0.008), proximal femur (14.2%; p<0.001) and femoral neck (20.3%; p<0.001), compared with white women. Although white women reported expending 45% more energy (p=0.03) in moderate intensity physical activity than black women on a weekly basis, current physical activity did not attenuate the difference in QUS measures between the races. The relations between QUS and BMD measures were similar in black compared with white women. After controlling for BMD, the racial differences in QUS measures were not apparent, precluding the conclusion that bone quality independently contributes to the reduction in fracture risk in older black women. The impact of current physical activity on QUS measures in older black and white women is negligible.

Absorptiometry, Photon↗
PubMed2005

Children achieve adult-like sensory integration during stance at 12-years-old.

This study examined balance control in children to determine at what age the integration of sensory information in unperturbed stance is comparable to that of adults. In addition, it examined whether overall performance was related to age, gender and specific physical characteristics, such as height, weight and body mass index (BMI). Seventy-four female and 80 male children between the ages of 6 and 12 years participated in the study, as well as 20 adults, aged 20-22 years. The Sensory Organization Test (SOT), a component of computerized dynamic posturography, was used to assess overall balance as well as the use of specific sensory information in maintaining stability. Analyses of variance revealed significant differences between equilibrium scores of 7- and 8-year-old and 11- and 12-year-old (p < .01), with only the 12-year-old participants achieving scores comparable to those of the adult group. A repeated-measures analysis of variance comparing the use of different sensory information across age and gender groups revealed that while all groups demonstrated mature use of somatosensory information, children under 11 did not use visual information as effectively as adults, and only the 12-year-old group demonstrated adult-like use of vestibular information. Correlational analyses revealed a moderate correlation between composite balance scores and age, r(152) = .38, p < .001, but poor correlations between the composite equilibrium score and height, weight and BMI (r < .13, p > .15). Multiple regression analysis revealed that while physical characteristics accounted for approximately 20% of the variability in the composite equilibrium score, age alone accounted for the largest single contribution to the variance (16%). These results support recent findings suggesting that children do not demonstrate adult-like use of sensory information prior to age 12 years.

Adult↗
PubMed2005

Postural and eye-blink indices of the defensive startle reflex.

Postural and eye-blink reactions to acoustic startle probes were examined in 24 volunteers, who completed two blocked conditions (baseline, startle). A postural reaction during the startle condition demonstrated a reflexive movement in the anterior-posterior direction, which was not observed during the baseline condition. This reflexive response was positively associated with the eye-blink reflex, such that larger blink magnitude related to greater posterior movement. These findings were not observed for postural movements in the medial-lateral direction. The results suggest that a measurable postural reaction may be observed following a startling acoustic stimulus, which may reflect generalized bodily flexion associated with a preparatory behavioral response.

Acoustic Stimulation↗
PubMed2004

Scale errors offer evidence for a perception-action dissociation early in life.

We report a perception-action dissociation in the behavior of normally developing young children. In adults and older children, the perception of an object and the organization of actions on it are seamlessly integrated. However, as documented here, 18- to 30-month-old children sometimes fail to use information about object size and make serious attempts to perform impossible actions on miniature objects. They try, for example, to sit in a dollhouse chair or to get into a small toy car. We interpret scale errors as reflecting problems with inhibitory control and with the integration of visual information for perception and action.

Cerebral Cortex↗
PubMed2004

Emotion and motivated behavior: postural adjustments to affective picture viewing.

Thirty-six participants (18 female, 18 male) viewed affective pictures to investigate the coupling between emotional reactions and motivated behavior. Framed within the biphasic theory of emotion, the three systems approach was employed by collecting measures of subjective report, expressive physiology, and motivated behavior. Postural adjustments associated with viewing affective pictures were measured. Results indicated sex-differences for postural responses to unpleasant pictures; an effect not found for pleasant and neutral picture contents. Females exhibited increased postural movement in the posterior direction, and males exhibited increased movement in the anterior direction, for unpleasant pictures. Subjective report of valence and arousal using the self-assessment manikin (SAM), and the startle eye-blink reflex were collected during a separate session, which replicated previous picture-viewing research. Specifically, participants rated pleasant pictures higher in valence and exhibited smaller startle responses compared to unpleasant pictures. Females also reported lower valence ratings compared to males across all picture contents. These findings extend our knowledge of motivated engagement with affective stimuli and indicate that postural responses may provide insight into sex-related differences in withdrawal behavior.

Adolescent↗
PubMed2004

Anticipatory postural adjustments for altering direction during walking.

The authors examined how individuals adapt their gait and regulate their body configuration before altering direction during walking. Eight young adults were asked to change direction during walking with different turning angles (0 degree, 45 degree, 90 degree), pivot foot (left, right), and walking speeds (normal and fast). The authors used video and force platform systems to determine participants' whole-body center of mass and the center of pressure during the step before they changed direction. The results showed that anticipatory postural adjustments occurred during the prior step and occurred earlier for the fast walking speed. Anticipatory postural adjustments were affected by all 3 variables (turn angle, pivot foot, and speed). Participants leaned backward and sideward on the prior step in anticipation of the turn. Those findings indicate that the motor system uses central control mechanisms to predict the required anticipatory adjustments and organizes the body configuration on the basis of the movement goal.

Adaptation, Physiological↗
PubMed2003

Taiji training improves knee extensor strength and force control in older adults.

The purpose of this study was to examine the effects of Taiji training on knee extensor strength and force control in older individuals. Twenty-six healthy older adults (71.9 +/- 1.8 years) participated in the study. Sixteen of the older adults (70.2 +/- 1.8 years) underwent Taiji training for 20 weeks (experimental group), whereas the other 10 (74.6 +/- 1.2 years) served as the control group. For both groups, strength and force control of the knee extensors was assessed twice with an isokinetic dynamometer. Strength was assessed with a maximum voluntary isometric contraction (MVC). Force control was measured as the standard deviation (SD) and coefficient of variation (CV) of force during a constant isometric knee extension task at 2%, 30%, 60%, and 90% MVC. For the experimental group, MVC significantly increased (19.5 +/- 4.9%) and the CV of force decreased (18.9 +/- 3.3%) following Taiji training. Improvements in the CV of force were primarily due to decreases in the SD of force (R(2) =.86) rather than increases in strength (R(2) =.12). Furthermore, decreases in SD of force were independent of improvements in strength. For the control group, strength, SD, and CV of force were not different for the 2 tests. The overall findings suggest that Taiji training improves knee extensor strength and force control in older adults.

Aged↗