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PubMed2004

Resolving conflicts in task demands during balance recovery: does holding an object inhibit compensatory grasping?

The ability to reach and "grasp" (grip or touch) structures for support in reaction to instability is an important element of the postural repertoire. It is unclear, however, how the central nervous system (CNS) resolves the potential conflict between holding an object and the need to release the held object and grasp alternative support, particularly if the held object is perceived to be relevant to the task of stabilizing the body, e.g. an assistive device. This study examined whether compensatory grasping is inhibited when holding an object, and whether the influence differs when holding an assistive device (cane) versus a task-irrelevant object (top handle portion of a cane). We also investigated the influence of preloading the assistive device, to determine whether conflicting demands for arm-muscle activation (requiring disengagement of ongoing agonist or antagonist activity) would influence the inhibition of compensatory grasping. Unpredictable forward and backward platform translations were used to evoke the balancing reactions in 16 healthy young adults. A handrail was mounted to the right and foot motion was constrained by barriers, with the intent that successful balance recovery would (in large-perturbation trials) require subjects to release the held object and contact the rail with the right hand. Results showed that grasping reactions were commonly used to recover equilibrium when the hand was free (rail contact in 71% of large-perturbation trials). However, holding either the cane or canetop had a potent modulating effect: although early biceps activation was almost never inhibited completely (significant activity within 200 ms in 98% of trials), the average activation amplitude was attenuated by 30-64% and the average frequency of handrail contact was reduced by a factor of two or more. This reduced use of the rail occurred even though the consequence often involved falling against a safety harness or barriers. Handrail contact occurred least frequently when holding the cane during forward loss of balance: subjects persisted in pushing on the cane (failing to use the rail) in 93% of trials, even when the perturbations were too large to allow this strategy to be successful. Prior contraction (preloading the cane) did not influence any of these findings. Complex strategies (e.g. partial release of object) were often adopted to allow balance to be recovered without dropping the held object. Remarkably, it appears that the CNS may give priority to the ongoing task of holding an object, even when it has no stabilizing value (cane during backward falls) or any intrinsic value whatsoever (canetop).

Adaptation, Physiological↗
PubMedDate not supplied

Meeting the challenge of new fatherhood during the early weeks.

OBJECTIVE: To explore new/subsequent Australian fathers' perspectives on the experiences, processes, and life changes in the early weeks of fatherhood. DESIGN: Interpretive study using in-depth interviews and grounded theory analysis techniques, based on a symbolic interactionist framework. SETTING: Participants were recruited from the postnatal wards of a major public hospital, early discharge program, and early childhood centers in southeast Queensland, Australia. PARTICIPANTS: Eighteen first-time/subsequent fathers interviewed 6 to 12 weeks after the birth. RESULTS: Although rewarding, fathers found new or expanding fatherhood to be a significant challenge and time of change. Major themes included making a commitment, taking responsibility, negotiating responsibilities, developing and maintaining relationships, maintaining family integrity, balancing activities, and perceiving the self as father. Work had a major impact on fathers' ability to participate with their family and newborn. To manage, fathers sought to balance the demands of work and home, deal with stressors, manage their time, develop routines, and reprioritize. Fathers developed a sense of themselves as fathers over time, building confidence and deriving satisfaction from their fathering role. CONCLUSIONS: A range of competing factors affected fathers' ability to participate in the home with their newborn in the early weeks after birth.

Adult↗
PubMed1988

Kinesthetic awareness in subjects with multiple ankle sprains.

The purposes of this study were 1) to determine whether decreased kinesthetic awareness occurs in individuals with recurrent ankle sprains and 2) to determine whether the one-legged standing balance test can be used to differentiate between ankle instability in injured and uninjured ankles. Thirty athletes between 18 and 24 years of age with multiple sprains of one ankle and no reported sprains of the other ankle were tested to compare their ability to detect passive plantar flexion and standing balance in each ankle. Luce's choice theory was used to analyze subjects' responses. Subjects had significantly greater difficulty detecting passive motion in the ankle with sprains as compared with the uninjured ankle. Subjects also performed a one-legged standing balance test on both the injured and uninjured legs. In 20 subjects, either the subject or observer reported balance deficits on the injured side as compared with the uninjured side. The results of this study demonstrate the need for clinicians to evaluate kinesthetic deficits and to design exercise programs to improve kinesthetic awareness and decrease ankle instability in individuals with multiple ankle sprains.

Adolescent↗
PubMed2005

Creatine supplementation reduces muscle inosine monophosphate during endurance exercise in humans.

INTRODUCTION: Creatine (Cr) supplementation has been shown to attenuate increases in plasma ammonia and hypoxanthine during intense endurance exercise lasting 1 h, suggesting that Cr supplementation may improve muscle energy balance (matching of ATP resynthesis to ATP demand) during such exercise. We hypothesized that Cr supplementation would improve muscle energy balance (as assessed by muscle inosine monophosphate (IMP) accumulation) during intense endurance exercise. METHODS: Seven well-trained men completed two experimental trials involving approximately 1 h of intense endurance exercise (cycling 45 min at 78+/-1% & OV0312;O2 peak followed by completion of 251+/-6 kJ as quickly as possible (performance ride)). Subjects ingested approximately 42 g.d dextrose for 5 d before the first experimental trial (CON), then approximately 21 g Cr monohydrate plus approximately 21 g.d dextrose for 5 d before the second experimental trial (CREAT). Trials were ordered because of the long washout time for Cr. Subjects were blinded to the order of the trials. RESULTS: Creatine supplementation significantly (P< 0.05) increased muscle total Cr (resting values: CREAT: 138.1+/-7.9; CON: 117.7+/- 6.5 mmol.kg dm). No difference was seen between treatments in any measured muscle or blood metabolite after the first 45 min of exercise. Despite the performance ride completion time being similar in the two treatments ( approximately 13.5 min, approximately 86% & OV0312;O2 peak), IMP at the end of the performance ride was significantly (P<0.05) lower in CREAT than in CON (CREAT: 1.2+/- 0.6; CON: 2.0+/- 0.7 mmol.kg dm). CONCLUSION: Raising muscle total Cr content before exercise appears to improve the ability of the muscle to maintain energy balance during intense aerobic exercise, but not during more moderate exercise intensities.

Adult↗
PubMedDate not supplied

Costing neonatal care alongside the Collaborative ECMO trial: how much primary research is required?

Researchers working on economic evaluations alongside trials have to balance minimising data collection with maximising the ability to measure differences in costs. Using existing data sources may keep the costs of research down, but these data may not be entirely appropriate to the evaluation question. When evaluating technologies in intensive care it is particularly important to be able to classify patients correctly by their resource requirements especially when those requirements vary considerably from day to day. This paper describes and justifies methods for costing the care provided for babies in (one arm of) an on-going multi-centre trial, the Collaborative ECMO trial. This trial is evaluating alternative policies of life support for mature (full term) newborn babies with severe respiratory failure. The most reliable cost information on neonatal intensive care is available from a study, conducted independently from the trial, which has used simple cost apportionment on a large sample of units. By drawing on clinical opinion and carrying out a case note exercise we assessed whether this available information was appropriate to estimate 'baseline' costs for the control group during their initial 'acute' phase of illness. We concluded that the available cost estimates would need to be weighted to reflect the additional costs of drugs and investigations for this group of babies during the acute phase. Multidisciplinary collaboration on trials can help economists and other researchers to balance the requirement for simple cost measurements with more detailed primary research.

Cost-Benefit Analysis↗
PubMed1987

[Possible molecular mechanisms of limited or infinite division of cells].

A new approach to the possible molecular mechanisms which determine the ability of cells to the infinite or limited division is presented. The ideas proposed are based on the experimentally demonstrated premise that the realization of DNA reparation and replication depends on the maintenance of a strict balance between the growth rate of replication forks and SSB-protein synthesis within the cells. The limited ability of cells to the division is considered to be a result of the disorganization of DNA reparation and replication processes when the above-mentioned balance is disturbed. The infinite ability of cells to the division is interpreted as a result of the absence of the disorganization of the above-mentioned processes with disturbance of the same balance. The molecular mechanisms which determine either the presence or absence of the cell response to the disturbed balance between the growth rates of replication forks and SSB-protein synthesis are discussed in detail. The conclusion is drawn that the ssb-gene is a protooncogene converted into an oncogene as a result of the dotted mutation manifesting in the functional inactivation of the third domain of the SSB-proteins.

Bacterial Proteins↗
PubMed1985

Cardiovascular adrenoreceptor balance during hemorrhagic hypotension and shock.

The primary aim of this study was to examine the hypothesis that the ability of the cardiovascular system to compensate for hemorrhagic hypotension is controlled by a balance between the relative influence of the alpha 1 and extrasynaptic alpha 2 adrenoreceptors. Previous studies have implied that, although both receptors participate in the baroreceptor response to hypotension, only the extrasynaptic alpha 2 receptors are able to maintain the compensatory vasoconstrictor effort for a prolonged period of time. In each experiment two Sprague-Dawley rats were anesthetized and subjected to a modified Wiggers hemorrhagic shock protocol. One rat in each pair was pretreated with either 25 mg/kg of the cyclooxygenase inhibitor sodium meclofenamate or 0.5 mg/kg of the selective alpha 1 antagonist prazosin. The results indicate that neither drug interfered with the normal maximum compensatory effort as defined by the maximum blood loss (ie, reduced total vascular capacitance) when mean arterial pressure (MAP) was reduced to 30 mmHg by hemorrhage. In fact, when normalized for pre-hemorrhage MAP, it was apparent that prazosin, which lowered pre-hemorrhage MAP, may have actually improved the compensatory response. Sodium meclofenamate increased the time to reach the maximum compensatory effort (comp time), while prazosin increased the time to reach 20% uptake from the blood reservoirs (decomp time). Since both drugs enhanced the total time (comp + decomp) and both are known to interfere with alpha 1 function, these studies support the hypothesis stated above.

Animals↗
PubMed1989

Ratings of surgical residents by self, supervisors and peers.

Ratings by self, supervisors and peers of surgical residents were compared and contrasted, and the correlation between these ratings and the scores on the American Board of Surgery In-Training Examination (ABSITE) were studied. In addition, comparisons were made between ratings by residents of their peers (n = 32) and of attending surgeons (n = 61) with whom they had worked. The ratings consisted of scores from 1 to 5 in each of ten areas of clinical competence. Results indicated that over-all ratings by peers and supervisors were highly intercorrelated (r = 0.92; p less than 0.001) and that the average of over-all ratings by peers and supervisors correlated moderately with the total raw score on ABSITE (r = 0.58; p less than 0.01). Factor analyses suggested that the dimensions underlying the three sets of ratings differed considerably. It appeared that ratings by supervisors were influenced primarily by the interpersonal skills of the residents and secondarily by ability. In contrast, self-ratings by the residents were apparently mainly influenced by their perceptions of their own ability, followed by interpersonal skills and effort. Ratings by peers, on the other hand, seemed to reflect the over-all impression of the peers of the resident being rated. Comparisons between ratings of peers and attending surgeons by residents revealed that residents view attending surgeons as having a more balanced level of competence, across areas of both ability and interpersonal skills. Ratings of peers were lower than were the ratings of attending physicians by the residents in the areas of technical ability, knowledge of basic science and clinical knowledge.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

[Development of cognitive strategies and self control strategies in 8 to 14-year-old children].

This study examines the interaction between the development of cognitive strategies and self-monitoring abilities in children aged 8 to 14. Children were tested individually on eight proportionality problems presented with the balance-scale task. Cognitive development was assessed by the strategy used and the performance on each problem. The indicators of self-monitoring were: latencies before and after the solution of a problem, self-evaluation of one's ability to make the balance scale stay level, proportion of oriented moves on the balance scale, and persistence on a problem. Children's self-monitoring reactions to failure were assessed by changes in strategies, verbal explanations, self-evaluation of performance, and latencies. Results showed an interaction between the complexity of the items and cognitive level. On more complex items, children of lower cognitive levels had shorter latencies, made more (but less oriented) moves on the balance scale, persisted less in their activity, and had more difficulty to evaluate properly their performance. Following failure, children of lower cognitive levels did a less accurate evaluation of their performance, modified their strategy, and did not change their verbal justification, whereas children of higher cognitive levels did a good evaluation of their performance, did not change their strategy, and had the tendency to change their verbal justification. Following failure, all children took less time planning their activity. The results suggest that self-monitoring abilities develop according to the development of cognitive strategies and are mediated by the complexity of the task.

Achievement↗
PubMed2004

Nitrogen balance and delta15N: why you're not what you eat during pregnancy.

Carbon (13C/12C) and nitrogen (15N/14N) stable isotope ratios were longitudinally measured in human hair that reflected the period from pre-conception to delivery in 10 pregnant women. There was no significant change in the delta13C results, but all subjects showed a decrease in delta15N values (-0.3 to -1.1 per thousand) during gestation. The mechanisms causing this decrease in hair delta15N have not been fully elucidated. However, since the delta15N values of dietary nitrogen and urea nitrogen are significantly lower compared to maternal tissues, it is hypothesized that the increased utilization of dietary and urea nitrogen for tissue synthesis during pregnancy resulted in a reduction of the steady state diet to a body trophic level effect by approximately 0.5-1 per thousand. An inverse correlation (R2 = 0.67) between hair delta15N and weight gain was also found, suggesting that positive nitrogen balance results in a reduction of delta15N values independent of diet. These results indicate that delta15N measurements have the ability to monitor not only dietary inputs, but also the nitrogen balance of an organism. A potential application of this technique is the detection of fertility patterns in modern and ancient species that have tissues that linearly record stable isotope ratios through time.

Adult↗
PubMed1989

The dynamics of rooting in Triplochiton scleroxylon cuttings: their relation to leaf area, node position, dry weight accumulation, leaf water potential and carbohydrate composition.

Single-node, leafy stem cuttings of Triplochiton scleroxylon K. Schum. were collected from successive nodes down the uppermost shoot of 2-shoot stockplants. The leaves were trimmed to 10, 50 and 100 cm(2) before the cuttings were set under intermittent mist to root. Batches of cuttings were harvested after 0, 14, 28 and 42 days to assess leaf water potential, dry weight and carbohydrate content of their leaf and stem portions. Cuttings with leaf areas of 10, 50 and 100 cm(2) increased in total dry weight by 29, 61 and 90%, respectively, during the 6-week period. The increase in dry weight was accompanied by increases in reflux-extracted soluble carbohydrates (RSC), water-soluble carbohydrates (WSC) and starch. By contrast, increase in leaf area reduced leaf water potential of cuttings before root emergence. Fewer large-leaved cuttings rooted than smaller-leaved cuttings, suggesting that rooting ability is at least partially determined by the balance between photosynthesis and transpiration. Fewer roots per cutting were produced on cuttings with 10 cm(2) leaves than on cuttings with larger leaves. Node position affected increments in dry weight, carbohydrate content and leaf water potential, with differences between nodes on day 0 generally being lost or slightly reversed by day 14. Rooting ability was not related to initial (day 0) carbohydrate content, suggesting that rooting is dependent on carbohydrates formed after severance. During the rooting period, the proportions of total non-structural carbohydrate as WSC and starch were reversed, from mostly WSC on day 0 to mostly starch by day 42. These changes in WSC and starch occurred most rapidly in large-leaved cuttings.

Journal Article↗
PubMed2005

An intensive massed practice approach to retraining balance post-stroke.

BACKGROUND AND PURPOSE: Falls are highly prevalent and a significant source of complications post-stroke. This study tested the efficacy of standard physical therapy (based on the task-oriented approach) delivered in a massed practice paradigm. The purpose of this study was to test if the intensive massed practice intervention (6h/day for 2 consecutive weeks) could significantly improve balance function post-stroke. METHODS: A single-subject multiple baseline design across subjects with probes was utilized with ten subjects with chronic stroke disability. Clinical tests and time to stabilization (TTS) of the center of pressure in response to a platform perturbation were calculated during baseline, intervention, and the maintenance phases. RESULTS: The ability of the subjects to recover from a balance threat improved, with mean TTS decreasing from 2.35 +/- .51 s during baseline, to 1.58+/-.23s during training, and further still to 1.45 +/- .29 s during the maintenance phase, ending 3 months post-intervention. Clinical findings demonstrated improvements in anticipatory and steady-state balance control. In addition weight-bearing symmetry improved and the number of falls sustained reduced. CONCLUSIONS: Intensive massed practice of standard physical therapy produced significant results in balance retraining with patients post-stroke. Our finding support the need to offer additional practice to maximize the efficacy of physical therapy sessions.

Adolescent↗
PubMed2000

The effect of age-related declines in proprioception and total knee replacement on postural control.

BACKGROUND: An experiment was designed to examine the effects of a decrease in threshold joint position sense (TJPS) at the knee and ankle and of total knee replacement (TKR) on postural control in older adults. It was hypothesized that older adults with a decrease in TJPS and those who had undergone TKR would display increased center of pressure (COP) variance during quiet stance and late onsets for muscle responses to balance threats. METHODS: Older adult subjects (> or = 70 years) were evaluated and grouped according to the status of their ankle and knee threshold joint position sensation as well as their surgical history. COP data were collected while subjects stood on a force plate with feet together under eyes-open and -closed conditions. Threats to balance were given using a platform that moved forward and backward. RESULTS: Older subjects with poor knee extension TJPS had significantly increased COP variance, although those with very poor knee flexion and extension TJPS demonstrated even greater increases. Similarly, subjects with decreased ankle TJPS demonstrated increased COP variance. However, reduced TJPS did not affect the ability of subjects to respond to threats to balance. Post-TKR subjects showed no reductions in any aspect of postural control. CONCLUSIONS: This study showed that the task of standing quietly has a direct relationship to threshold JPS, although the task of recovering from an abrupt perturbation does not. Older adult TKR results suggest that there is no negative effect on balance from elective joint replacement.

Aged↗
PubMed1999

Inter-segmental co-ordination in sit-to-stand: an age cross-sectional study.

BACKGROUND AND PURPOSE: Being able to sit-to-stand (STS) effectively is an important functional skill, but there is little information available on the changes that occur with growth and maturity. This study aimed to investigate the inter-segmental co-ordination of STS in three different age groups (12-18 months, 4-5 years and 9-10 years). METHOD: The children studied wore reflective markers and were videotaped as they stood up from a height-adjustable seat that straddled a forceplate. Segmental kinematics and vertical ground reaction force were determined from the co-ordinate and forceplate data. RESULTS: Even at the earliest developmental stage the children had mastered the basic inter-segmental pattern observed in adults. The youngest children, however, were not able to end the movement in quiet standing; rather they raised up on their toes or took a step forward. Performance varied both within and between subjects. Although there was a similarity in the motor pattern used by the younger subjects to that of the older subjects, developmental trends were evident on the videotapes and on examination of the kinematic and kinetic variables. Movement time, amplitude and peak angular velocity of trunk flexion increased with age. Whereas the children in the older age groups displayed a pattern of vertical ground reaction force similar to that reported for adults, the youngest children tended to reach peak force gradually, often with fluctuations. Although there were characteristic trajectories in the phase-plane plots for each group, the overall trend was for the percentage of smooth plots representing a co-ordinated movement, to increase with age. CONCLUSIONS: Differences in inter-segmental co-ordination between the ages studied may relate to the child's ability to control horizontal momentum and to balance.

Age Factors↗
PubMed1996

Characterization of sensorimotor performance, reproductive and aggressive behaviors in segmental trisomic 16 (Ts65Dn) mice.

In the present study, segmental trisomy 16 (Ts65Dn) mice, an animal model of Down Syndrome (DS), were examined for sensorimotor, reproductive, and aggression abnormalities associated with DS. The Ts65Dn mice exhibited no sensorimotor deficits in olfactory sensitivity, visual abilities, orientation reactions, forelimb strength, postural skills, balance/ coordination, climbing, or locomotion compared to genetically matched control B6EiC3HF1 mice. In mating tests, the percentage of Ts65Dn mice displaying intromissions when paired with estrous females was significantly less than that in controls. Although the percentage of Ts65Dn mice that mounted and ejaculated with an estrous female was marginally less than in controls, there were no significant differences on the other measures of reproductive behavioral performance. In aggression tests, Ts65Dn males showed increased offensive aggression in a neutral arena both when paired and among grouped males. Conversely, Ts65Dn mice exhibited less offensive aggression against an intruder in their home cage than control males. In sum, these mice possess some of the adaptive behavior abnormalities observed in DS patients; however, because the Ts65Dn mice do not have any observed sensorimotor deficits that could interfere with behavioral assessments, they may serve as a useful model for the study of behavioral impairments associated with DS.

Aggression↗
PubMedDate not supplied

Premedication for upper gastrointestinal endoscopy.

Premedication is not essential to endoscopy but patient tolerance is clearly improved and, thus, ease of examination. Although comparable results can be achieved through nonpharmacologic means, the time and effort involved precludes their widespread use. Despite near universal utilization of premedication in endoscopy, the associated risk is difficult to determine from the available literature. The reported data reveal nominal risk yet must be viewed as minimums. The ideal drug with predictable clinical effects, minimal postprocedure impairment, little respiratory compromise, and proven antagonist is not yet available. Although midazolam seems to represent an advance, recent emphasis on respiratory depression is particularly troublesome. Studies evaluating various agents have suffered from lack of quantitation of such parameters as patient tolerance, ease of examination, and postprocedure impairment. Development of proven standards for these parameters would have to occur before a definitive double-blind randomized trial could be undertaken. Suggested means of assessing these parameters are listed in Table I. Improvement in major morbidity would be difficult in light of its low incidence. As the search for the ideal drug continues, endoscopists must continue to use drugs whose full effects are incompletely understood. The ability to increase patient comfort must be balanced with the small, but ever present, risk of morbidity and mortality.

Anesthesia, Local↗
PubMed1998

The role of the monocyte in the generation and dissolution of arterial and venous thrombi.

Monocyte infiltration into forming thrombus has been demonstrated in experimental models of venous thrombosis developed in our laboratories. These cells produce and release plasminogen activators as the thrombus organises and resolves. Monocytes are also capable of assembling and releasing procoagulant factors and the evidence for their importance in thrombogenesis is reviewed. The ability of monocytes to maintain this fibrinolytic balance suggests that they may have a role in both thrombosis and thrombus resolution. Control of the mechanisms which regulate these activities may therefore be important in preventing thrombus formation or stimulating its resolution.

Animals↗