Body movements are activities that are continuous, rhythmic, and patterned phenomena. They are unique to the individual and are influenced by interaction with the environment, which also displays rhythmic phenomena such as seasonal changes, day-night changes, and wave patterns of light, sound, and fluids.
Balance is critical to effective and efficient movement and posture. This sensorimotor activity requires the integration of numerous sensory stimuli, which are the basis for the patterning of motor activity. When effective and appropriate, the motor activity minimizes body sway and prevents falling. Among the elderly, anatomic and physiologic changes interfere with these processes, reduce sensory input, and interfere with balance. This study focuses on movement as a therapeutic intervention. It is hypothesized that elderly people who receive vestibular stimulation produced by rocking in a rocking chair will demonstrate larger balance scores than elderly persons who do not receive vestibular stimulation.
With increasing age, an adult experiences changes in tissue structure and cellular function that interfere with the ability to perceive and function within the environment. In elderly people, the extent of these changes may interfere with the ability to perform coordinated body movements, may increase the risk of injury and disability, and may reduce the quality of life. Limitations in behavior involving sensory and motor function often occur during the sixth and seventh decades.
Changes occur in the sense organs and nervous system with increasing age. The function of each is altered as aging progresses. Initially, some aspects of altered function are compensated for effectively by changes in the environment or by increasing utilization of stimuli from various sensory modalities. As compensation becomes less effective, serious limitations in behavior may appear. Within the sensory and nervous systems, these limitations are not compensated for adequately in the sixth and seventh decades of life.1
The anatomic and physiologic changes associated with aging are responsible for alterations in tissue structure and cellular function. Within the sensory and nervous system, these changes are manifested in diminished sensory input and diminished central integration of afferent and efferent stimuli.1-3
Reduction in sensory input occurs in several ways. The sensitivity of the sense organs is reduced by structural and cellular function changes. These changes increase the threshold necessary to evoke an afferent stimulus and result in diminished visual acuity, proprioceptive sensation, tactile sensation, and vestibular sensory input. Even though the elderly continue to interact with the environment, these alterations reduce the sensory input to the central nervous system.
Of particular importance to this study are changes within the vestibular system. According to van derLaan and Oosterveld, vestibular excitability decreases after the age of 20. 4 They propose that these changes are related to diminishing blood supply to the semicircular canals, saccules, and utricles, and a reduction in neural excitability. Dissolution of the otoliths occurs after the age of 50 with almost complete destruction by age 70.5'6 Therefore, after age 60, there is a significant decrease in vestibular sensory input.4'7
Vestibular sensory stimuli and proprioceptive sensory stimuli also are diminished by a reduction in movement. Several investigators have demonstrated a decrease in body activity in the elderly. This reduction in activity begins at the age of 50 and is progressive.8
Motor acts such as locomotion and balance require central integration of sensory input and motor output. In the elderly, there is a reduction of sensory input, which interferes with sensory perception by limiting the amount of sensory information.9 Therefore, the coordination of a motor act is based on less detailed sensory information that may interfere with the effectiveness and appropriateness of the motor act. The impairment of sensorimotor acts in the elderly is reflected by alterations in locomotion and balance. The elderly display abnormal gait and loss of arm movement, which adversely affect balance.3 In addition, the elderly have an increase in the amount of body sway.10
Optimal levels of sensory stimulation are required for effective mental and motor activity. Adequate sensory stimuli are an important requirement in maintaining the integrity and function of the neurosensory and neuromuscular systems. Without adequate and meaningful sensory stimuli, alterations in mental and physical function occur that impede effective and appropriate interaction with the environment.
With limited body movement there is a reduction in vestibular, tactile, and proprioceptive sensory input, which is associated with mental and physical dysfunctions of sensory deprivation."'12 Zubek demonstrated that the manifestations of sensory deprivation precipitated by limited body movement can be prevented by periods of physical exercise." The integrity of the neurosensory and neuromuscular systems is dependent on sufficient sensory input associated with body movement."'13
Numerous forms of movement have been related significantly to positive changes in mental function,14-16 growth and development,17-19 and motor activity.13'20"23 Movement has many forms and evokes various sensory inputs. Movement that requires muscle activity provides proprioceptive, vestibular, and tactile sensory input but also produces changes in the cardiovascular and respiratory systems and muscle tissue.13 The presence of these physiologic changes or the combination of these changes and movement may be responsible for the demonstrated effects of movement, and not the movement itself.
To delineate the effects of movement from the physiologic effects of muscle activity, attention must be focused on the effects of movement without muscle activity. Rotation and rocking are two forms of passive movement.
Rotation and rocking stimulate the afferent neurons of the semicircular canals, the utricle, and the saccule. The mechanisms by which this vestibular stimulation affects motor function, motor development, arousal, and language is uncertain.
Several investigators propose that vestibular stimulation integrates various sensory stimuli,17'24'27 activates the reticular formation,"'25'28 and organizes the efferent outflow necessary for motor activity.24'26 Researchers have postulated that vestibular activity organizes and integrates sensory stimuli into meaningful patterns.24'26'27 Such integration of visual, proprioceptive, and tactile stimuli into meaningful patterns provides the foundation upon which motor activity is organized. Not only may vestibular activity integrate sensory input, it also may activate the reticular formation.
This system increases the level of arousal and modulates motor activity by facilitatory and inhibitory effects upon motor neurons.27 This modulation of activity is one requirement for coordinated motor activity.9 In fact, researchers involved in studying sensory and perceptual deprivation postulate that optimal levels of sensory input into the reticular formation are required for its effective function."'12'29
The increased level of arousal associated with reticular formation activation is also important in motor activity. With increasing arousal, there is a reciprocal increase in awareness of the environment. With increased levels of awareness, sensitivity to sensory stimulus also is increased. By increasing sensitivity, greater amounts of sensory input are available. Besides increasing information for sensory integration, there is an increased readiness for action, which reduces the neurological reaction time necessary to respond to changes in the environment.30
Rocking does evoke vestibular stimulation but the amount is less than that produced by rotary movement.14 Since minute changes in head position activate the vestibular system, strong stimulation that results in nystagmus may not be necessary to provide adequate vestibular stimulation needed to affect mental and motor function.31
Research studies that investigate rocking and its effects are limited. Significant relationships between rocking and growth and development, levels of arousal,32'33 and visual tracking22 have been demonstrated. These studies suggest that the gentle movement of rocking does have an effect on mental and physical functions. Neal investigated the relationship of rocking and the development of motor, auditory, and visual responses of premature infants.18 These infants were rocked in a motorized cradle for 30 minutes, three times a day until the gestational age and infant age reached a total of 252. When compared with a control group of infants at this same age, those who were rocked achieved significantly greater development of motor, auditory, and visual responses. Other researchers also rocked infants.22 Pederson and Ter Vrugt conducted several research studies involving the rocking of infants.32"34 The effects of rocking on levels of arousal as determined by crying, wakefulness, and motor activity were studied. Various amplitudes and frequencies were used. When compared with levels of arousal before rocking, there were significant differences at all frequencies and amplitudes. The combination associated with the greatest change in level of arousal was an amplitude of five inches and a frequency of 60 per minute.
Since rocking evokes vestibular stimuli, it is possible that this stimulation may be related to changes in physical and mental function. Even with the paucity of research studying the effects of rocking, there is some empirical evidence that suggests a significant relationship between rocking and mental and physical function in infants. Further study is necessary to determine if there is this same relationship in an elderly population.
ANALYSIS OF COVARIANCE FOR DIFFERENCES BETWEEN GROUPS WITH PRETEST SCORES AS COVARIATE
MAN N-WHITNEY ANALYSIS OF PRETEST BALANCE AND POSTTEST BALANCE BY GROUP
Therefore, this pilot study was undertaken with a sample of 36 women, whose average age was 80 years. These women were selected randomly from a population of elderly people who were independent in activities of daily living and were not institutionalized at the time of data collection. Persons then were assigned randomly to either an experimental or control group. Excluded from this sample were persons who had central nervous system damage, Meniere's Syndrome, or motor neuron diseases of multiple sclerosis or amylotrophic lateral sclerosis, and persons who participated in calisthenics or rocking within the last 24 hours.
After obtaining written consent from the subjects, the balance of the subjects was measured using the Balance Instrument (BI) and Balance Perception Questionnaire (BPQ). Subjects of the experimental group then rocked in a rocking chair continuously for one-half hour. In contrast, the subjects in the control group sat in a chair for one-half hour. The investigator was present during this period and verbally interacted with the subjects in both groups. The balance of all subjects was tested again using the BI and BPQ.
Stances incorporated into the Balance Instrument used in this study were from the Functional Ambulation Profile (FAP) developed by Nelson,35 the Quantitative Examination of Neurological Function (QUENF) developed by Tourtellotte, Haerer, Simpson, Kuzman and Sikorski,36 and instruments of other researchers.20'37 Measurement is of the subject's ability to maintain a stance over time with the eyes opened and closed.
Several researchers established validity of their instruments by determination of coefficients of variation that measure the extent to which the scores congregated together.35'36'38 These researchers concluded that the high variability of scores of subjects with impaired motor function and low variability in healthy young adults reflected quantitative changes in neurologic function that impaired balance.
Reliability of various instruments that measure ability to maintain a stance over time has been established by both the test-retest method and the inter-rater method.20'35 The balance scores of six subjects were determined simultaneously at the pretest or post-test measurement by two raters. Reliability determined by this inter-rater method was .99 using the Pearson product moment correlation coefficient.
Additional data on the subjects' perception of their balance were obtained using a questionnaire, Balance Perception Questionnaire ( BPQ), which has a seven-point scale. Scores from one to seven were assigned to each space on the scale. A total score for the instrument was obtained by adding the scores of the spaces in which the responses were placed.
Since initial differences of BPQ scores in the two groups may not have been compensated for by random sampling and random assignment, analysis of covariance was used to adjust for these pretest scores. The results of the analysis were not significant at the .05 level but the subjects in the experimental group demonstrated a trend toward perceiving an improvement in their balance after rocking for 30 minutes (see Table 1).
ANCOVA was not used in evaluating the BI scores since several outlyers were present in both groups. Therefore, the Mann-Whitney test was used instead. No significant relationship was found between balance and rocking (see Table 2).
The results of the study did not demonstrate significant improvement in balance scores associated with the experimental intervention. Therefore, rocking may not evoke changes in balance, or its effects may have been altered or masked by factors related to the experimental design, the instruments, or physiologic or psychologic factors associated with the subjects.
The physiologic changes associated with aging may have diminished the effects of rocking. Researchers have demonstrated and described the dissolution of otoliths in the elderly. Destruction of these structures is almost complete by the age of 70. Since the average age of the control and experimental groups was 80 years, extensive destruction of otoliths probably was present in all subjects. Also, a progressive decrease in the threshold of excitability of vestibular neurons was demonstrated by van derLaan and Oosterveld.4 These changes diminish vestibular excitation and output associated with movement.
Physiologic changes in the central nervous system also may have been a contributing factor. Central integration of afferent and efferent stimuli is impaired in the elderly.2'3 Therefore, the change in sensory input required to alter central nervous system integration and the output necessary to produce changes in neuromuscular functions associated with balance may not have been achieved by the movement used in this study.
Movement has been demonstrated to increase neuromuscular coordination significantly in the elderly.13'14'21 The movement in these studies was not rocking. Investigations of the effects of rocking have been done only with infants. The frequency and amplitude of rocking and the type of movement used in this study may not be the most effective in an elderly population. The physiologic changes associated with aging may have altered its effectiveness. This possibility suggests that changes in mental and physical functioning may be dependent on an interaction between the age of the subject and the type and characteristics of the movement used.
Even if the rocking produced sufficient and appropriate changes in vestibular input, the duration of rocking may have been insufficient for measurable changes in balance to occur. Repeating the period of rocking throughout the day and/ or over several days or weeks may have demonstrated a cumulative effect on balance scores.
In this study, balance was measured by the Balance Instrument. This may not have been precise or sensitive enough to detect small changes in balance that may have occurred. Instruments utilizing computers and electronics have greater sensitivity and precision than the BI. Use of these instruments would have permitted the investigator to identify smaller changes in balance. The short, single duration of rocking was a limitation in the experimental design. Other factors associated with the physiologic changes of aging and the characteristics of the movement also must be considered. Whether these factors altered or masked the effects of rocking on balance scores, or whether rocking is not related to improvements in these scores remains uncertain.
This study explores the effectiveness of motion in evoking neuromuscular changes associated with balance in an elderly population. Since this study was derived from previous research that demonstrated the significant effects of movement, questions remain regarding possible reasons for the nonsignificant results of this study. Even though several factors that may account for these results have been discussed previously, further research is required to answer many of the questions.
The therapeutic effectiveness of movement as a nursing intervention is a significant area for clinical application and for research. Previous research has demonstrated that movement is related to positive changes in mental and physical functioning. There is paucity of research focused on the effects of movement on neuromuscular function in the elderly. Therefore, these studies not only need to be replicated but additional clinical applications identified.
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ANALYSIS OF COVARIANCE FOR DIFFERENCES BETWEEN GROUPS WITH PRETEST SCORES AS COVARIATE
MAN N-WHITNEY ANALYSIS OF PRETEST BALANCE AND POSTTEST BALANCE BY GROUP