Life-span development in functional tasks.

Life-Span Development in Functional Tasks

A Life-Span Concept of

Motor Development

Developmentalists bring to the study of human movement unique sets of assumptions that influence their approach to research. Although theoretical diversity exists within developmental science and among motor development researchers, [1] there is a unifying interest in age-related change in motor behavior. Physical therapy practice has been influenced by classic motor development theory [2, 3] through the writing of Stockmeyer, [4, 5] the Bobaths, [6] Knott and Voss, [7] and Voss. [8] These individuals brought to the forefront of our profession the notions of developmental sequences, and they incorporated behaviors that are the product of early motor development into treatment programs. Integral to these sequences are the theoretical underpinnings that explained the process of motor skill acquisition early in the life span. According to classical theory, [2, 3[ motor development is primarily caused by the process of maturation of the central nervous system (CNS). As a corollary to this theory, when neural maturation is complete, the developmental process terminates. [2, 3]

In contrast to classical theory, a life-span concept of motor development is emerging. [9-11] A life-span theory of motor development assumes that age-related change in motor behavior is a lifelong phenomenon. The assumption of lifelong change requires reexamination of the concept of neurological maturity as the marker of completion of the developmental process and consideration of additional processes and factors that cause age-related change in behavior.

Traditionally, theorists have portrayed maturity as the pinnacle of the developmental process. [12, 13] According to these theorists, the mature behaviors of young adulthood comprise the standard against which older and younger individuals are judged. To be "immature" or "past your peak" is to be devalued. From a life-span perspective, maturity is just a passing point it time, to be valued no more than infancy, the middle-aged years, adolescence, or any other age period. [14]

Most contemporary motor development theories explain change in behavior as the result of interactions among intrinsic factors, such as physical growth or neural maturation, and extrinsic factors, such as supportive and rich environments. Interactions among intrinsic and extrinsic factors also explain motor development from a life-span perspective. A different focues, however, results when the theory is expanded to include processes of change for the old, the young, and all ages in between.

The effect of this different viewpoint can be illustrated by considering physical growth, which is almost synonymous with the traditional concept of development. We grow taller and heavier as we move from infancy through childhood. Growht, like development, is classically portrayed as a progressive process, characterized by increases in size, or, in the case of development, advancement in some realm. Yet, during adolescence, body shapes also change, and in the middle adult years body shape may change again. Later in the life span, height and weight typically decrease. Although even early in life, declines, losses, and regressions are natural means of developmental change, [15] we traditionally ignore these trends. A life-span concept of development encompasses all changes: those that are progressive, those that are regressive, and those that result in reorganization. I believe the process that explain why some motor behaviors are lost are just as interesting as those that explain why new actions are acquired and those that reveal how other behaviors remain stable from infancy through old age, despite intrinsic and extrinsic change.

Motor development researchers often look to intrinsic factors to explain age-related change in motor behavior. [2,3,16] Yet, extrinsic factors also vary systematically with age. For example, retirement brings about age-related changes in life style and activity patterns that affect motor behaviors. Early in life, children in our culture make a transition from sleeping in a crib to sleeping in a bed. Although the specific reasons and timing of transitions may vary, such changes foster development of different motor behaviors. Thus, extrinsic factors that effect age-related change in motor behavior are as dynamically related to age as intrinsic factors.

A life-span perspective offers the opportunity to examine a broad range of change processes. Some change processes may abide by an overriding principle that might only be discovered by studying a broad range of the life span. Maturation, learning, and aging are processes that may have common features and adhere to common principles of lifelong change.

In this article, I will use a life-span perspective to review a series of studies that my graduate students and I have undertaken. At the end of this review, I will offer a perspective on how this research might affect the way physical therapy is practiced.

Righting Task--An Overview

Righting behaviors constitute those body actions that move the individual from recumbency to erect bipedal stance. Righting behaviors hold practical and theoretical significance for physical therapists. From a purely practical viewpoint, righting tasks are major components of functional physical independence. To move from a supine to a sitting position, to roll over, and to get to a standing position are all expressions of physical independence. Although we often emphasize walking as a key ingredient for independence, those who cannot perform righting tasks lack a full measure of self-reliance.

Traditionally, early-appearing righting movements have been thought to be under the control of subcortical nuclei. [2] As a result of CNS maturation, the cerebral cortex is believed to exert control over the primary forms of righting, and "mature" and "integrated" behaviors are evidenced. [2,12] Furthermore, as an aftermath of CNS damage, righting abilities are often lost [4,12,17,18] and the individual may be incapable of rising to a standing position or may use primitive patterns of righting.

McGraw [2] interpreted change in the form of righting movements as a reflection of cortical maturation. The tasks she studied included rolling from a supine to a prone position, moving from a supine to a sitting position, and moving from a supine position to erect stance. When individuals are able to move from a supine position, through sitting to squatting, and on up to a standing position, righting is said to have reached an advanced, mature form. [12]

I decided to study the righting task of rising from a supine to a standing position for several reasons. First, I was concerned with selecting movement patterns for patients to use when moving from recumbency to standing. Second, my observations of healthy young adults performing this task revealed a seemingly inordinate amount of variability in the form of movements used to stand from a supine position. Young adults did not universally demonstrate what had been characterized as "mature" form, and I was not sure why this was so. Finally, rising from a supine position was an ideal task for study from a life-span developmental perspective because the capacity to move from a supine to a standing position appears early in the life span and is present thereafter.

Beginning with my doctoral dissertation work, I will illustrate how the research questions developed by my colleagues and me have evolved with time. The method we have used to collect data is relatively simple and will only be reviewed briefly. Those wishing further information on data-collection procedures may consult previous detailed descriptions. [19,20]

Studies of Rising from

Supine--A Life-Span

Perspective

The assumptions underlying VanSant's [19] study of rising from the floor were that age-related changes in motor behavior occur across the life span and that change in motor behavior occurs within components of body action. A component represents a part of body action. In the research discussed in this article, three components were studied: action of the upper extremities (UEs), movements of the axial region (AX), and movements of the lower extremities (LEs). When selecting these components, I was influenced by the writings of Lawrence and colleagues [20-22] and Kuypers, [23] who identified different systems of descending control over axial and limb movements. Their model of descending control provides a framework for asking developmental questions concerning the relationship among neural systems that control body movements. For example, do limb movements dissociate from axial patterns early in the life span? Does developmental change in the AX trigger change in the limbs?

In an initial study of young adults, [19] VanSant was concerned with describing the movement patterns used by young adults in rising from the floor. The first question was: Is the variety of UE, AX, and LE movements small enough to allow formation of descriptive categories for each component? The main purpose of that study was to propose a developmental order of movement patterns for each component of body action. First, however, the movement patterns used to perform the task had to be identified.

Each of the young adults participating in that study [19] were videotaped performing 10 consecutive trials of rising from a supine to a standing position. A single video camera was used to collect the data. The camera was positioned to obtain a side view of the subject, who was lying on an exercise mat at the start of each trial.

The method of data reduction and analysis was somewhat unique. No kinematic data were generated; rather, a written description of component action was created for each trial while reviewing the videotapes. The trial-by-trial descriptions were then compared and arranged into groups comprising similar action patterns. A set of more general descriptions were written that encompassed the groups of similar action. These more general descriptions were validated by using them to classify the actions of all subjects on all trials. The Table presents examples of the categories that describe AX movements in the task of rising from a supine to a standing position.

Having formed a set of descriptive categories for each component of body action, the main question was addressed concerning the movement patterns as developmental steps. Do the movement pattern categories meet specific criteria for developmental stages? The method of data analysis used to propose developmental sequences was predicated on formal stage-theory constructs. [25] Specifically, if one assumes that the developmental process is characterized by progression through an ordered series of stages, then at any point in the developmental process an individual's behavior reflects the developmental stage attained. If development is assumed to be a life-span process, individuals of all ages demonstrate their developmental stages. Furthermore, if an individual is in transition between stages, the motor behavior should reflect those adjacent stages. Identification and validation of stages according to formal stage-theory criteria is a complex and involved process. [25,26] It is possible, however, to use stage-theory assumptions to identify developmental sequences of behaviors.

The process of ordering the categories into a developmental sequence requires analysis of the performance of all individuals across a set of trials. [25] The data from a subject who uses more than one movement pattern within a component across the trials of a task can be used to identify adjacent steps of the sequence. For example, if a subject demonstrated two different movement patterns during a set of 10 trials, the two patterns would be hypothesized to be successive developmental steps. By carefully inspecting the patterns of variability of the subjects, developmental sequences can be proposed for each component of body action. Thus, a single age group can be used to identify the movement patterns used to perform a task and to propose developmental sequences for each component of body action.

The next study of VanSant [27] was designed to determine whether the movement patterns identified in young adults were "developmental." Did the patterns vary with age? Did they vary in a way that lent support to the sequences proposed for each component of body action? Before these questions could be asked, I first had to determine whether the movement patterns developed in the study of young adults [19] adequately described the movement patterns of young children.

Children ranging in age from 4 to 7 years were the subjects (N=120) of VanSant's study. [27] The data-collection methods were the same as those used with young adult subjects, [19] with the exception that two cameras, placed perpendicular to each other, were used to film the subjects. One camera obtained a lateral view and the other obtained a view of the soles of the feet of the subject, who lay supine at the start of each trial.

As a result of that study of children, [27] two new movement-pattern categories were formed and the original movement-pattern categories were broadened to include some variations in form that had not been observed in the young adults. [19] Because the children demonstrated two new movement-pattern categories, the proposed developmental sequences for the AX and LE components were expanded to include those new patterns as early steps before examining the relationship between age and the incidence of each pattern. I proposed that younger children would demonstrate a greater proportion of the early steps and that older children would demonstrate a greater proportion of later steps. [27] The children's data were then analyzed by determining the incidence of each movement-pattern category in each of four age groups (ie, ages 4, 5, 6, and 7 years). For each component, the incidence of each pattern was graphed with respect to age. This study of children demonstrated that the movement patterns varied with age. Patterns proposed as early steps were more common in younger children than in older children; conversely, patterns proposed as later steps were more common in older children than in younger children.

In concluded that the study of young adults [19] was very useful for identification of developmental movement patterns for the task of rising from a supine position. After studying both adults [19] and children, [27] the descriptions of the movement patterns had become sufficiently general to enable study of the rising task from a broadened life-span perspective. A complementary theme, however, was beginning to surface. Among the patterns of movement observed across the ages, there were subtle details that were unique to specific age groups. As the general descriptions of the patterns of movement used to rise from a supine position became increasingly refined, the differences among the age groups became increasingly apparent. I believe a heightened awareness of these similarities and differences is a result of the wide range of ages and the numbers of subjects studied in each age group.

To understand the types of similarities and differences I am referring to, an example will be helpful. As a result of studying the young adults, [19] a trunk pattern termed "Symmetrical Interrupted by Rotation" had been identified. This pattern was characterized by symmetry early in the process of flexing the trunk toward sitting. That symmetry was commonly interrupted by trunk rotation to the right or left when weight was transferred from the buttocks onto the feet. Although some children demonstrated initial symmetry, most began rising by flexing with a slight degree of rotation. [27] This rotation was corrected with a counter-rotation that brought them back toward a symmetrical flexion pattern as they moved toward sitting. Some children demonstrated several reversals of rotation prior to transferring weight from their buttocks to their feet. The children and adults both demonstrated a trunk pattern that brought the trunk predominantly forward with a slight degree of rotation. The children seemed to be seeking a midline orientation, whereas the young adults exhibited that orientation but were unable to preserve it at the time of weight transfer. The category was broadened to include the children's variation of the movement pattern, and the title of the category was changed from Symmetrical Interrupted by Rotation to "Forward with Rotation." There are other examples of differences between children's and adults' movements within a single movement-pattern category. In the process of identifying the similarities, one becomes increasingly cognizant of the differences.

The rising task has since been studied by Sabourin [28] in adolescent subjects; by VanSant et al [29] in adults in their thirties, forties, and fifties; and by Luehring [30] in older adults. Leuhring, [30] as a result of studying older subjects, formed a new LE category to describe a bilateral kneeling action common among her older subjects. She also identified UE patterns that involved the action of pushing on the thighs in the process of rising. She redefined two UE categories to include the thigh push. Believing that the pushing patterns represent distinctive developmental steps seen in older adults, I have recently developed two new categories and added them as later steps to the original sequence of UE movement patterns for this task. [31]

The five studies [19,27-30] that have been completed provided data for a lifespan graph of movement patterns for the rising task. [31] The patterns of each body region demonstrate a varying incidence across the range of ages studied. I have found that some patterns are most commonly seen in children, others are typical of teens and young adults, and still others are most frequently observed in the elderly. It is therefore quite likely that the patterns represent developmental steps for this task.

To the best of my knowledge, the graphs illustrating age differences in component patterns in the righting task represent the first life-span model of movement-pattern development for any task. The studies discussed previously lend support to the hypothesis that developmental change in motor behavior occurs across the life span and not just as a phenomenon of the younger years. The sequences of development that can be proposed from the graphs of age differences in righting movements have yet to be validated in longitudinal studies. Two studies by VanSant that are currently in progress are following some of the elderly subjects of Leuhring's study [30] and individuals, 6 through 24 years of age, over several years.

Through inspection of life-span graphs for the rising task, it appears that advanced form in rising movements occurs during the teenage years. Sabourin's study [26] indicated the highest incidence of symmetrical rising occurred in 15-year-olds. A symmetrical form of rising, previously promoted as the mature form of rising, [12] seems to require the greatest control of direction and force production. Small deviations in force production result in corrective movements of the trunk and compensatory UE and LE actions that in turn affect the distribution of weight over the base of support. Having observed thousands of trials of this task across a wide range of age groups, I am impressed with the degree to which the task reflects dynamic balance ability.

In older subjects and in young children, transitional postures, as points for attaining balance, are more common. It is as though the task of rising is broken down by those with less balance ability into discrete segments--sitting up, getting onto all fours, moving to a kneeling or a squatting position and then to a standing position. On the other hand, teenagers and young adults tend to move to a standing position in one motion, evidencing only two transitory postures: sitting and squatting.

The cross-sectional data obtained from the studies of rising reveal a period of progression toward an advanced form, occurring across the childhood and early teenage years, followed by a slow rate of regression to the use of patterns common in early childhood. Yet, as mentioned previously, within those patterns that are seen in both older and younger subjects, there are age differences that our descriptive categories currently obscure. Because these subtle age differences are evident within small segments of our sample (ie, the patterns of the old and the young), the further refinement of these descriptive categories is a subject for future study.

Studies of Other

Righting Tasks

We have used this method of data collection and analysis to study other tasks of practical significance to physical therapists: rolling from back to stomach, rising from a chair, and rising from a bed.

Rolling

Richter [20,32] studied the task of rolling from a supine to a prone position. He asked the question: Will categories, developed from observable differences in adults' rolling movements, be validly hypothesized as developmental steps according to stage-theory criteria? [32] He was able to identify a set of four movement patterns for each of the three components of body action, but encountered some difficulty using stage theory to order his movement-pattern categories into developmental sequences. He could not identify a sequence in which all subjects varied between adjacent steps. Richter [32] turned to McGraw's [2] classical descriptions of infants' rolling patterns and proposed an ordering for each component that was in accord with her findings regarding the development of infants' rolling movements. Richter's proposed developmental sequences for each component were subsequently examined by Lewis [33] in her study of children and by Boucher [34] in a study of adolescents performing the rolling task.

Lewis [33] and Boucher [34] first asked if the movement pattern categories developed by Richter [32] were accurate and comprehensive descriptors of rolling movements for the populations they were studying. The movement pattern categories identified by Richter [32] in his study of young adults were found to be descriptive of both the children's [33] and adolescents' [34] rolling movements.

Although no new movement-pattern categories were added, both Lewis [33] and Boucher [34] observed a stepping form of leg action in which first one and then the other LE was on the support surface to assist the roll through a pushing action. Richter [32] identified two LE patterns that involved pushing: (1) a bilateral, but simultaneous, pushing pattern and (2) a unilateral pushing pattern. The alternate stepping action during the roll was seen in one child and in two adolescents. Roberton (MA Roberton, PhD; personal communication) has cautioned not to form a categorical description to portray the action of one child. She points out the need to observe several individuals demonstrating an action pattern prior to writing a categorical description; otherwise, the essential features of the movement pattern may be obscured by idiosyncratic characteristics. This is particularly the case when the pattern is more common in a different age group. As an example, a seemingly idiosyncratic pattern was observed in a young adult subject in VanSant's [35] study of rising from a supine to a standing position. That subject moved from a side-sitting to a squatting position by pushing with the UEs and lifting both LEs off the surface to jump and land in a squatting pattern. Not until the pattern was repeatedly observed in a group of 4-year-old children was a movement-pattern category developed that specifically characterized this form of LE action. This example suggests that the lifespan developmental perspective has much to offer to the study of variable performance of adults and any other restricted age group.

After categorizing the UE, AX, and LE action of their subjects' rolling movements, Lewis [33] and Boucher [34] also asked whether age differences in the incidence of movement patterns within each component corresponded to the developmental sequences proposed by Richter. [32] Are the patterns proposed to represent early-appearing steps more common in younger subjects than in older subjects, and, conversely, are the patterns proposed as later steps more common in older subjects than in younger subjects?

Combining results of Lewis's [33] and Boucher's [34] investigations indicated that two of Richter's [32] hypothesized developmental sequences were apparently misordered. [36] Figure 1 presents the incidence of each UE pattern in each of the age groups studied in the rolling task. Inspecting the order in which UE patterns predominated in increasingly older age groups, the developmental order of UE patterns from early childhood into adulthood appears to be what Richter [32] hypothesized as step 4, then step 1, then step 3, and finally step 2. Figure 2 indicates that the order of predominance of LE patterns appears to be step 3, followed by step 2 in later childhood. Then either step 3 or 4 predominates, because both were equally common in the 13-year-old subjects. Step 3 may predominate again in the later teenager and young adult years. The finding that step 3, the "Unilateral Push" pattern, is prevalent in early childhood and then again in the teenage years raises the following questions: (1) Why would a pattern predominate at different points in the life span? and (2) What factors might be operating at those times to influence motor behavior in rolling? Traditional models of development as a progression to maturity would suggest that a second period of dominance represents "regression" to an earlier form of behavior following maturity. Have we identified what represents mature form in rolling? Would mature form be evidenced in the performance of 8- and 10-year-old children who demonstrate the unilateral lifting pattern? Is one pattern more efficient than another? Movement patterns used for rolling, unlike those of rising to a standing position, are relatively "value-free." We do not know what characterizes mature rolling and are therefore not hampered by a value system that would suggest which pattern is best or requires the greatest degree of control. We only have evidence that different patterns are common at different points of the life span; the reasons why are unexplored.

Figure 3, depicting the incidence of AX patterns in each age group, reveals a better outcome for Richter's [32] hypothesis of order of development of AX movement patterns. The order of predominance across the childhood, teenage, and young adult years appears to be step 2, then step 3, and finally step 4. Although the AX pattern step 1 was not predominant in any of the age groups studied thus far, its greatest incidence was seen in the youngest subjects. Because this pattern also demonstrated a progressively decreased incidence in increasingly older age groups, it is likely that the pattern may be more common in children younger than those we have studied.

Rising from Bed

Sarnacki [37] studied the task of rising from a bed, first describing the movement patterns of young adults performing this task and then using stage-theory constructs to propose developmental sequences of movement patterns for components of body action. Because both UEs could not be seen throughout the movement using a single foot- or side-view camera, the UE component was separated into two components: the near upper extremity (NUE) and the far upper extremity (FUE). If a subject turned toward the right side in the process of rising, the right UE was designated the NUE and the left UE was designated the FUE. The AX and LE components were defined as in VanSant and colleagues' previous studies. [19,20] Sarnacki's [37] component sequences have been examined both in younger subjects [38] and in adults in their thirties, forties, and fifties. [39] In McCoy's [38] study of teenagers, a new UE pattern was defined and the description of a trunk pattern more common in teenagers than in young adults was refined. McCoy concluded that the age range she studied was not broad enough to identify developmental trends, and she questioned whether the movement patterns described by Sarnacki [37] were developmental steps. By comparing the incidence of movement patterns observed in teenagers with that reported by Sarnacki [37] for young adults, McCoy [38] was able to document age differences in the movement patterns for the task of getting out of bed.

Ford-Smith [39] asked the following questions: Do adults in their middle years demonstrate developmental regression in the task of rising from a bed? Are movement patterns proposed by Sarnacki [37] as early-appearing developmental steps more common in older adults than in younger adults? Conversely, are later developmental steps seen less often in older adults than in younger adults? Ford-Smith [39] studied individuals in their thirties, forties, and fifties and found evidence that movement patterns used to get out of bed vary with age across the adult years. She was unable, however, to find evidence of regression. The Ford-Smith study [39] was confounded by the fact that McCoy's [38] study of younger subjects was undertaken concurrently. Thus, Sarnacki's [37] proposed developmental sequences had yet to be validated by examining younger subjects. With study of both younger and older subjects complete, Sarnacki's [37] proposed sequences are now ready for examination from a life-span perspective.

Rising from a Chair

Francis and VanSant [40] have described component movement patterns for the task of rising from a chair. They suggested that the variability reported in kinematic studies [41-47] of the sit-to-stand movement is due to developmental differences in the movement patterns used. Their study was designed differently from those that hypothesized developmental steps using stage-theory criteria. Francis and VanSant included both children and adults in their study. They had the subjects come to a standing position from a chair that was appropriately sized to allow a sitting posture of approximately 90 degrees of hip and knee flexion. After defining movement-pattern categories for the UEs, the AX region, and the LEs, they plotted age-group differences in order to propose developmental sequences. [48] They concluded that movement patterns used to get up from a chair are age-related. Thus, developmental differences can be used to explain variability in performance of the sit-to-stand task.

Factors Related to Movement

Patterns Used to Perform

Righting Tasks

Body Dimensions

Rising from a bed and getting up from a chair require that the individual execute movements that are shaped by the relative size of the bed or chair and one's body. Small children can "drop down" off the bed onto the floor, extending their LEs, whereas adults "get up from sitting" by flexing forward and then extending to the vertical. When considering the need to execute movements that are congruent with objects such as beds and chairs, it is easy to see how the size and dimensions of the body might influence developmental change. It is somewhat more difficult to predict relationships among body dimensions and movement patterns when one thinks of a task that is a bit more environmentally neutral, such as rolling on a flat surface or rising from the floor.

McGraw [2] originally proposed that the body dimensions might influence the developmental change in body movements used to stand up from the floor. She specifically proposed that the ratio between leg length and body length might be a meaningful factor contributing to the change in movement patterns. My colleagues and I have followed up this lead by obtaining a set of body measurements on all of the subjects who have participated in our studies [19,27-30] of rising from the floor.

The findings of VanSant and colleagues [49] indicate there is a relationship between body dimensions and movement patterns in the task of rising from the floor. The strength of the relationship varied with age and gender within each component. In subjects 4 through 25 years of age, a ponderal index accounted for 20% to 30% of the variability in the female subjects' component patterns and for 25% to 35% of the variability in the male subjects' component patterns. Specifically, the taller and lighter subjects demonstrated more advanced patterns compared with the shorter and heavier subjects. In the older female subjects, an androgyny index and age accounted for 30% to 40% of the variability in component patterns. Those women with more masculine body builds, wider biacromial widths, and narrower bicristal widths were more likely to demonstrate advanced movement patterns. Age was also a significant factor in the adult women, with younger women more likely than older women to demonstrate advanced patterns. In men, only age was found to be a significant variable, accounting for approximately 20% of the variability in component patterns. As with the female subjects, youth was also associated with the more advanced patterns in the male subjects.

Kugler (P Kugler, personal communication, October 1988) has suggested that body topography, rather than body mass, might be a factor affecting movement patterns in the rising task. His suggestion seems most plausible if one considers, for example, an individual who is overweight. When attempting to flex the LEs to bring the feet to the buttocks and to flex the trunk to move toward sitting, the calves may abut the thighs and prevent the feet from approaching the buttocks, and the abdomen may approximate the thighs and prevent forward progression of the trunk toward the feet. The individual must then use a different pattern of movement that involves rotating the trunk toward one side in order to transfer weight to the LEs.

We (AF VanSant, P Verma, J McDonald, L Dehadrai; unpublished data) have recently asked the question: Does adding weight to the body affect the movement pattern used to rise to a standing position from a supine position? We videotaped young adults, first while they were loaded with two different percentages of their body weight and then without the weights. Our preliminary results suggest that carrying an extra 10% of body weight does affect the rising pattern. In those subjects who demonstrated a symmetrical form of rising, the added weight resulted in asymmetrical patterns. In those subjects with asymmetrical patterns, the effect was less obvious and represented a more subtle change within a movement-pattern category. Thus, we have begun to explore the factors that are related to righting movements and that might help explain age-related change in these movements.

Activity Level

Another factor that researchers are beginning to explore is the individual's level of physical activity. Luehring [30] asked the question: Does activity level affect the movement patterns used to stand up from a supine position? She videotaped both active and inactive elderly subjects. Those subjects who were active had a history of participating three or more times per week in physical activity classes offered at the University of Missouri (St Louis, Mo). Luehring found the two groups used different movement patterns to get up from the floor. Those subjects who were active used patterns that represented later-appearing developmental steps, as compared with the inactive group, who demonstrated a greater degree of regression to earlier patterns of rising.

Green [50] has extended Luehring's [30] line of research by asking whether physically active adults would demonstrate more developmentally advanced movement patterns than less physically active adults. She studied individuals in their thirties who were grouped according to their level of physical activity: (1) those who exercised daily, (2) those who exercised once or twice a week, and (3) those who rarely exercised. Green found that the more active subjects, who exercised daily or once or twice a week, demonstrated more developmentally advanced movement patterns than those who rarely exercised. She suggested that general activity level may be a factor that causes the differences in movement patterns observed among healthy adults.

Clinical Considerations

and Summary

As a physical therapist, this newfound knowledge profoundly affects the way I think about patients. First, I assess the movement patterns my patients use to perform these tasks and compare the observed patterns with the expected patterns for their age groups. I am reluctant to prescribe a single set of movement patterns to be used in the performance of a task. I consider age, gender, body size, and body shape as well as activity level when selecting a set of movement patterns to teach.

I am concerned with the selection of each set of movement patterns, because I have also developed a strong appreciation for variability in human performance. With the exception of adults who tend to perform consistently, other age groups vary their performance by using various combinations of UE, AX, and LE movement patterns. Although adults may be consistent in their performance, they can vary the patterns they use if asked or if the situation demands the use of an alternate form of movement in order to accomplish the task. It is the potential for variability that characterizes normalcy. Varying the situational demands seems a most natural way to introduce variability into patient performance. I search the environment for objects that might be used to bring out a specific pattern. Varying the heights of objects, such as chair seats, is just one example of the creative ways in which we are able to assist patients in adding to their behavioral repertoire.

Through this research program, the movement patterns used to perform common righting tasks are being described and defined. Age differences in the incidence of movement patterns used to perform the tasks are being documented, and sequences of development of movement patterns within body regions are beginning to be revealed and examined in longitudinal studies. I have begun to study atypical populations, beginning with a study of head-injured patients. Again, the first question is: Are the movement-pattern categories accurate and comprehensive descriptors of the movement patterns used by head-injured individuals to perform the task? It is possible that new descriptive categories might evolve in the study of patient populations to characterize their unique patterns of movement.

We are also beginning to identify factors that are related to movement patterns in various age groups and to manipulate them in quasi-experimental and experimental studies. Two of these factors are body dimension and activity level. These factors hold a great deal of promise for further understanding of lifelong change in motor behavior.

In summary, the life-span approach to motor development provides a theoretical framework to examine the continual development of motor abilities. The broadened perspective provided by life-span theory suggests factors that have not traditionally been considered to cause age-related change in behavior. The component approach to movement-pattern description has been a very useful initial step in describing tasks of interest to physical therapists and in identifying what appear to be developmental sequences of movement patterns for these tasks. The component approach also reveals the natural variability in movement patterns among and between individuals, both at a single point in and across developmental time.

A VanSant, PhD, PT, is Associate Professor, Department of Physical Therapy, College of Allied Health Professions, Temple University, 3307 N Broad St, Philadelphia, PA 19140 (USA).

References

[1] Williams K. What is motor development? Quest. 1989;41:179-182.

[2] McGraw MB. The Neuromuscular Maturation of the Human Infant. New York, NY: Hafner; 1962.

[3] Gesell A. The ontogenesis of infant behavior. In: Carmichael L, ed. Manual of Child Psychology. 2nd ed. New York, NY: John Wiley & Sons Inc; 1954:335-373.

[4] Stockmeyer SA. An interpretation of the approach of Rood to the treatment of neuromuscular dysfunction. Am J Phys Med. 1967;46:900-956.

[5] Stockmeyer SA. A sensorimotor approach to treatment. In: Pearson PH, Williams CE, eds. Physical Therapy Services in the Developmental Disabilities. Springfield, Ill: Charles C Thomas, Publisher; 1972:186-222.

[6] Bobath K, Bobath B. Cerebral palsy, parts I and II. In: Pearson PH, Williams CE, eds. Physical Therapy Services in the Developmental Disabilities. Springfield, Ill: Charles C Thomas, Publisher; 1972:31-185.

[7] Knott M, Voss DE. Proprioceptive Neuromuscular Facilitation. New York, NY: Harper & Row, Publishers Inc; 1968.

[8] Voss DE. Proprioceptive neuromuscular facilitation: the PNF method. In: Pearson PH, Williams CE, eds. Physical Therapy Services in the Developmental Disabilities. Springfield, Ill: Charles C Thomas, Publisher; 1972:223-282.

[9] Haywood KM. Lifespan Motor Development. Champaign, Ill: Human Kinetics Publishers Inc; 1986.

[10] Payne VG, Isaacs LD. Human Motor Development: A Lifespan Approach. Mountain View, Calif: Mayfield Publishing Co; 1987.

[11] Woollacott MH, Shumway-Cook A. Development of Posture and Gait Across the Life Span. Columbia, SC: South Carolina Press; 1989.

[12] Schaltenbrand G. The development of human motility and motor disturbances. Arch Neurol Psychiatry. 1928;20:720-730.

[13] Wyke B. The neurological basis of movement: a developmental review. In: Holt KS, ed. Movement and Child Development. Philadelphia, PA: JB Lippincott Co; 1975:19-33.

[14] VanSant AF. A life span concept of motor development. Quest. 1989;41:224-235.

[15] Oppenheim RW. Ontogenetic adaptions and retrogressive processes in the development of the nervous system and behaviour: a neuroembryological perspective. In: Connolly KJ, Prechtl HFR, eds. Maturation and Development: Biological and Psychological Perspectives. Philadelphia, Pa: JB Lippincott Co; 1981:73-109.

[16] Shirley MM. The First Two Years: A Study of Twenty-Five Babies. Volume 1, Postural and Locomotor Development. Minneapolis, Minn: University of Minnesota Press; 1931.

[17] Bobath B. Abnormal Postural Reflex Activity Caused by Brain Lesions. London, England: William Heinemann Medical Books Ltd; 1965.

[18] Paine RS. The evolution of infantile postural reflexes in the presence of chronic brain syndromes. Dev Med Child Neurol. 1964;6:345-361.

[19] VanSant AF. Rising from a supine position to erect stance: description of adult movement and a developmental hypothesis. Phys Ther. 1988;68:185-192.

[20] Richter RR, VanSant AF, Newton RA. Description of adult rolling movements and hypothesis of developmental sequences. Phys Ther. 1989;69:63-71.

[21] Lawrence DG, Kuypers HGJM. The functional organization of the motor system in the monkey, I: the effects of bilateral pyramidal lesions. Brain. 1968;91:1-14.

[22] Lawrence DG, Kuypers HGJM. The functional organization of the motor system in the monkey, II: the effects of lesions of the descending brainstem pathways. Brain. 1968;91:15-36.

[23] Lawrence DG, Hopkins DA. The development of motor control in the rhesus monkey: evidence concerning the role of corticomotoneuronal connections. Brain. 1976;99:235-254.

[24] Kuypers HGJM. Anatomy of the descending pathways. In: Brooks VB, ed. Handbook of Physiology: Motor Control. Bethesda, Md: American Physiological Society; 1981;2:597-666.

[25] Roberton MA. Stability of stage categorizations across trials: implications for the "stage theory" of overarm throw development. Journal of Human Movement Studies. 1977;3:49-59.

[26] Roberton MA. Stages in motor development. In: Ridenour MV, ed. Motor Development: Issues and Applications. Princeton, NJ: Princeton Book Co Publishers; 1978:63-81.

[27] VanSant AF. Age differences in movement patterns used by children to rise from a supine position to erect stance. Phys Ther. 1988;68:1330-1338.

[28] Sabourin PT. Rising from a Supine to a Standing Position: A Study of Adolescents. Richmond, Va: Virginia Commonwealth University; 1989. Master's thesis.

[29] VanSant AF, Cromwell S, Deo A, et al. Rising from supine to standing: a study across middle adulthood. Presented at the Joint Congress of the American Physical Therapy Association and the Canadian Physiotherapy Association; June 12-16, 1988; Las Vegas, Nev.

[30] Luehring SK. Component Movement Patterns of Two Groups of Older Adults in the Task of Rising to Standing from the Floor. Richmond, Va: Virginia Commonwealth University; 1989. Master's thesis.

[31] VanSant AF. A life-span perspective of age differences in righting movements. In: Roberton MA, ed. Advances in Motor Development Research, Volume 4. New York, NY: AMS Press Inc. In press.

[32] Richter RR. Developmental Sequences for Rolling from Supine to Prone: A Prelongitudinal Study. Richmond, Va: Virginia Commonwealth University; 1985. Master's thesis.

[33] Lewis AM. Age-related Differences in Component Action During Rolling in Children. Richmond, Va: Virginia Commonwealth University; 1987. Master's thesis.

[34] Boucher JS. Age-related Differences in Adolescent Movement Patterns During Rolling from Supine to Prone. Richmond, Va: Virginia Commonwealth University; 1988. Master's thesis.

[35] VanSant AF. Developmental Sequences for Righting from Supine to Erect Stance: A Prelongitudinal Screening. Madison, Wis: University of Wisconsin; 1983. Doctoral dissertation.

[36] VanSant AF, Richter RR, Lewis AM, Boucher JS: Age differences in rolling from supine to prone in children, adolescents and young adults. Poster presentation at the 63rd Annual Conference of the American Physical Therapy Association; June 28-July 2, 1987; San Antonio, Tex.

[37] Sarnacki SJ. Rising from Supine on a Bed: A Description of Adult Movement and Hypothesis of Developmental Sequences. Richmond, Va: Virginia Commonwealth University; 1985. Master's thesis.

[38] McCoy JO. Age-related Differences in the Movement Patterns of Adolescents 11, 14, and 17 Years of Age Rising to Standing from Supine on a Bed. Richmond, Va: Virginia Commonwealth University; 1989. Master's thesis.

[39] Ford-Smith CD. Age Differences in Movement Patterns Used to Rise from a Bed: A Study of Middle Adulthood. Richmond, Va: Virginia Commonwealth University; 1989. Master's thesis.

[40] Francis ED, VanSant AF. Description of the sit-to-stand motion in children and young adults: hypothesis of developmental sequences. Poster presentation at the Joint Congress of the American Physical Therapy Association and the Canadian Physiotherapy Association; June 12-16, 1988; Las Vegas, Nev.

[41] Nusik S, Lamb RL, VanSant AF, Hirt S. Sit-to-stand movement pattern: a kinematic study. Phys Ther. 1986;11:1708-1713.

[42] Jones FP. The influence of postural set on pattern of movement in man. Int J Neurol. 1963;4:60-71.

[43] Jones FP, Gray FE, Hanson JA, et al. An experimental study of the effect of head balance on patterns of posture and movement in man. J Psychol. 1959;47:247-258.

[44] Jones FP, Hanson JA. Time-space pattern in a gross body movement. Percept Mot Skills. 1961;12:35-41.

[45] Kelley DL, Dainis A, Wood GK. Mechanics and muscular dynamics of rising from a seated position. In: Komi PV, ed. International Series of Biomechanics, V-B. Baltimore, Md: University Park Press; 1976:127-133.

[46] Wheeler J, Woodward C, Ucovich RL, et al. Rising from a chair: influence of age and chair design. Phys Ther. 1985;65:22-26.

[47] Burdett RG, Habasevich R, Pisciotta J, Simon SR. Biomechanical comparison of rising from two types of chairs. Phys Ther. 1985;65:1177-1183.

[48] Roberton MA, Williams K, Langendorfer S. Prelongitudinal screening of motor development sequences. Research Quarterly. 1980;51:724-731.

[49] VanSant AF, Sabourin PT, Luehring SK, et al. Relationships among age, gender, body dimensions and movement patterns in a righting task. Poster presentation at the 64th Annual Conference of the American Physical Therapy Association; June 11-15, 1989; Nashville, Tenn.

[50] Green LN. The Relationship Between Activity Level and the Movement Patterns of Supine to Standing. Manhattan, Kan: Kansas State University; 1989. Master's thesis.