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Research Report

Movement Characteristics of Persons with Prader-Willi Syndrome Rising from Supine

Belt, Anne B., MSPT; Hertel, Thomas A., MSPT; Mante, Jennifer R., MSPT; Marks, Ted, MSPT; Rockett, Veronica L., MSPT; Wade, Christine, PhD, PT; Clayton-Krasinski, Debra, PhD, PT

Author Information

Abstract

INTRODUCTION

In 1956, the Swiss physicians Prader, Labhart, and Willi first described what is now known as Prader-Willi syndrome (PWS). 1 PWS is characterized by hypotonia, size variation in types 1 and 2 muscle fiber composition (type 2 fiber atrophy; decreased numbers of type 2B fibers; and increased numbers of type 2C fibers), skeletal variations (coxa and genu valga; and scoliosis with a structural change of at least 10 degrees or more in 62%–68%), decreased metabolic rate, decreased physical activity, decreased energy expenditure, obesity (weight at or above the 95th percentile) small statue (height at or below the fifth percentile), and small hands and feet (Table 1). 2–6 Global developmental delay in a child younger than six years of age and mild to moderate mental retardation or learning problems in older children characterize the cognitive impairments. 2 It has been estimated that the incidence of PWS ranges from one in 10,000 to one in 25,000 live births. 3,7

Table 1
Table 1:
Major Diagnostic Criteria for Prader-Willi Syndrome 2

PWS has two distinct clinical stages. The first stage, occurring in the neonatal period and early infancy, is characterized by varying degrees of hypotonia, weak cry, hypothermia, hypogonadism, and a poor suck reflex. 3 Developmental delay in reaching motor milestones is evident in virtually all affected and may be severe. The average age of sitting and walking in individuals with PWS is 12 months and 24 months, respectively. 8 The children are often referred for habilitative services for motor delay and oral-motor difficulties. Psychomotor delay and early onset of childhood obesity characterize the second stage, which usually occurs between the ages of one and two years. 3,9 One of the most distinctive features of PWS is a change in feeding behavior. Infants with PWS show a significant decrease in muscle tone and a poor or absent suck reflex leading to decreased food intake and inadequate nutrition. Hyperphagia occurs between one and six years of age contributing to obesity. Improvement in motor skills occurs between two and five years of age and motor delays becomes less conspicuous. 8

The degree to which individuals with PWS can function in society varies depending on the number and severity of the impairments, medical management, and the prevention of secondary problems associated with obesity, including diabetes, hypertension, and respiratory compromise. The major focus of management of individuals with PWS has included dietary intervention, behavioral control, and hormone replacement therapy. The delays in the development of motor skills during infancy have been described but there is a lack of information on the movement characteristics of older individuals with PWS. Individuals with PWS are referred to physical therapy for an evaluation of notable impairments, motor abilities, and level of participation in societal roles. PT interventions are directed toward increasing strength, aerobic endurance, postural control, movement efficiency, and function. Obesity management, minimizing cardiovascular risk factors, and osteoporosis are important for youths and adults with PWS. 11

Component Approach to Movement Pattern Description

The ability to rise independently from supine to standing has been described in toddlers, young children, young adults, and in the elderly. 12–17 VanSant 14 detailed the components of the rising movement and provided descriptors for three body regions: upper extremity (UE), axial region (AX), and lower extremity (LE). VanSant 18 found that age-related differences in the rising task occur across the life-span in individuals without disability. The frequency of the movement patterns of each body region vary between specific age groups. 15 From the studies on rising, the progression toward an advanced form, occurring across the childhood and early teenage years, is followed by a slow rate of regression to the use of patterns common in early childhood. 18 Young teenagers display a more developmentally advanced rising pattern with the greatest frequency. The pattern is characterized by symmetry in the UE reach and axial movement with the LE narrow-based squat. 14 A symmetrical form of rising seems to require the greatest control of direction and force production. 18 Young adults (mean age = 28.6 years) use primarily symmetrical component actions whereas older adults (mean age = 35.5 years) use primarily asymmetrical actions. 15,19 Young children (ages four–seven years) and older adults use less developmentally advanced asymmetrical movement patterns relying on transitional postures for balance. 15,18 The task of rising is broken down into discrete segments (sitting up, getting onto all fours, moving to a kneeling or a squatting position, and then to a standing position) in older subjects and young children. Teenagers and young adults tend to move in one motion with only two transitory postures—sitting and squatting. 18

Body Dimension and Activity Level

Factors other than age-related differences such as body shape and lifestyle including the amount of exercise can impact the movement patterns used for the rising task. In 1940, McGraw 12 proposed that body dimension, the ratio between leg length and body length, might influence an individual’s method of movement. VanSant 18 addressed the question of body dimension in relationship to the rising task, correlating body weight and topography with the chosen movement pattern. VanSant 18 found that taller and lighter subjects demonstrated more advanced patterns compared with shorter and heavier subjects in rising from supine.

Green and Williams 19 studied the influence of physical activity levels with the chosen movement pattern in the rising task. The results of their study suggest that lifestyle patterns of activity of middle-aged adults, 30 to 39 years of age, influence the degree of sophistication of movement patterns used in the rising task. Active subjects (daily or one/twice week exercisers) consistently displayed the more developmentally advanced movement patterns. The least active group displayed the reverse tendency.

Movement Patterns in Children with Neuromuscular Involvement

The descriptors as described by VanSant 15 have been applied successfully to children with neuromuscular involvement. Boswell et al 20 studied the movement patterns of the rising task in 12 children, between four and seven, with mild to moderate hemiplegic and diplegic cerebral palsy (CP). They found that the established movement for the rising task could be applied to children with CP with some minor modifications. Across all age groups and within each body region, the group with CP demonstrated less developmentally advanced movement patterns and demonstrated less variability in the UE and AX regions when compared with the findings by VanSant 15 in children four to seven years of age. The children with CP were likely to repeat movements within a pattern and divide the movements into phrases or segments. 20

Complementing Gowers’ whole body description of rising, descriptors as described by VanSant were also successfully used among nine children with Duchenne muscular dystropy (DMD). 21 The most frequent UE (47.4%), AX (65.8%), and LE patterns (60.5%) were “push and reach to bilateral push followed by pushing on leg,” “full rotation abdomen up,” and “pike,” respectively. The movement patterns of children with DMD reflected the least developmentally advanced pattern in each body region and were found to be most similar to those asymmetrical movements of toddlers. Substantial between-subject variability was observed; however, within-subject variability was less, inasmuch as 44% of the children exhibited complete consistency across all trials. 21

Unrau et al 22 used VanSant’s movement pattern descriptors to classify the rising task of 15 adults (mean age = 37.5 years) with Down syndrome. Results of their study indicated that the subjects predominately used either less developmentally advanced asymmetrical movement patterns or the movement could not be classified. Sixty-four percent of the UE movements, 14.6% of the AX movements, and 33.8% of the LE movements could not be categorized. 22 Unrau et al 22 did not publish descriptors of the unclassified movement patterns most frequently observed in this population nor did they speculate why the movements could not be categorized. It is unclear as to whether the researchers correctly applied VanSant’s component analysis because they seem to describe whole-body action profiles. Furthermore, reliability statistics were not reported and the 22- to 65-year-old age span used in the Unrau et al 22 study may not be directly comparable with the 20- to 35-year-old subjects in the study by VanSant. 14

We examined the applicability of the categorical descriptors as described by Marsala and VanSant 17 to the movements of children and adults with PWS. We also assessed the movements that occur in the UE, AX, and LE among children and adults with PWS and compared these with the patterns of individuals without PWS when performing the rising task. We hypothesized that persons with PWS would exhibit less developmentally advanced movement patterns than their age-, gender-, and size-matched control. If the movement descriptors are found to be applicable for persons with PWS, component analysis can be used when examining the rising task in persons with PWS and directed PT intervention strategies can be proposed.

METHOD

Subjects

A convenience sample of subjects with PWS was recruited from the pediatric cholesterol clinic at Columbia-Presbyterian Medical Center, New York City. A primary physician diagnosed PWS. Control subjects were recruited from a local community center and were free of any known neurological, genetic, or musculoskeletal disorders. All subjects were able to stand from a supine position without an assistive device, were medically stable, and understood verbal instructions. The Institutional Human Subject Review Committee approved the study and informed consent was obtained for all subjects. Subjects were matched on age, gender, and body size. Body size was measured on the basis on the body mass index (BMI) calculated by dividing the subject’s body weight (kilograms) by their height (meters squared). BMI represents relative body fat and provides a good estimate of obesity. 23 An attempt was made to match subjects with PWS and controls within 10% of their BMI. VanSant 18 demonstrated a change in rising pattern among subjects, without disability, from a developmentally advanced symmetrical rising pattern to an asymmetrical rising pattern in association with a 10% increase in body weight.

Instrumentation

The equipment used in this study included: one six′ wide × eight′ long, two-inch-thick exercise mat; two Panasonic VHS recorders (Models AG-180 and AG-450), one three-panel mirror placed at the head of the mat; one color monitor with video cassette recorder with frame by frame capability; and a Detecto weight scale (model 3P7044). The two cameras were used to record a side view and a foot view of each subject. The side view camera was approximately 160 inches from the center of the mat and the foot view was approximately 170 inches from the center of the mat. The cameras were on tripods, and the zoom lens was adjusted to maximize the subject yet provide a full view of the mat and subject throughout the rising task. Researchers were trained during a one-day session with Dr. VanSant on the data collection and data reduction procedures.

Procedures

Subjects, or their guardians, completed an oral questionnaire regarding school placement, employment, recent injuries, physical activity level, and current use of PT or OT. Body weight and height were recorded. Subjects were asked to lie on their back in the center of the mat. Each subject rose from supine to standing on the verbal command “Ready, go.” After one practice run, the procedure was repeated until ten trials were completed. No instruction or demonstration on how to rise was given. Subjects were allowed to rest as needed. All subjects were able to complete all ten rising trials independently without verbal cues.

Data Reduction and Analysis

Movement patterns were classified for the videotaped performances viewed on a videocassette recorder with a color monitor using slow motion and stop action as needed. The foot view videotape was initially used to classify all data. The side-view videotape was used to clarify any obscured movement. The movement patterns of the UE, AX, and LE for each performance were classified using modified descriptors developed by Marsala and VanSant (Appendix). 17 One investigator viewed the first trial for each of the 18 subjects, and the movement patterns of the UE were categorized. Following this, the second trial for each subject was viewed, and the same investigator categorized the UE movement patterns. This procedure was followed for each successive trial until all trials had been categorized for all subjects. Other investigators followed the same procedure to categorize the movement patterns of the AX and the LE regions. Each investigator recorded movements that did not match the given descriptors and modifications were formulated. The frequency of occurrence of each movement pattern in the three body regions was recorded. Since the descriptors were ranked in a developmental sequence for each body region and since each subject performed the rising task 10 times, it was possible to generate a body region movement score that reflected a subject’s performance across all ten trials for each body region. Multiplying the movement pattern number by the number of occurrences across the trials generated the score. The lowest possible movement score in any body region would be achieved if movement pattern one was exhibited across all ten trials; yielding a score of 10 × 1 or ten. The highest possible movement score in any body region would be achieved if the most developmentally advanced movement pattern for that region were exhibited across all ten trials. The highest movement score for the UE, AX, and LE are 60, 50, and 70, respectively. The total score for each body region of the subjects was recorded.

A body action profile (BAP), a combination of UE, AX, and LE movement patterns demonstrated in a single execution, was generated. It provided a picture of the subject’s overall approach of the rising task. Frequency of the BAP was recorded for each subject and was considered a measure of the subject’s variability across trials.

Time to complete the rising task (duration) was tabulated for each subject across all trials from the videotaped performance and the average calculated. The videocassette recorder’s counter was used to measure the time elapsed from the moment the subject initiated the task to the moment the subject completed the task. The relationships between body region movement score and a) age, and b) BMI, were assessed with Spearman rank correlation co-efficients stratified by diagnosis.

Interrater and Intrarater Reliabilty

Thirty randomly selected trials of each body region were classified by a second examiner to determine interrater reliability and reclassified by the same investigator to determine intrarater reliability. A minimum interval of two days was required between the original classification and reclassification. The percent of exact agreement and kappa statistics were calculated for the UE, AX, and LE. When there was 90% or higher exact agreement and kappa values equal to 0.75 or greater, investigators were considered to be reliable. 24 Interrater and intrarater reliability data are presented in Table 2.

Table 2
Table 2:
Interrater and Intrarater Reliability of Classifying the UE, AX, and LE Movement Patterns

RESULTS

Subjects

Eighteen subjects between seven and 36 years of age including nine subjects with a diagnosis of PWS and nine age-, gender-, and size-matched individuals without PWS, participated in this descriptive study. Subject characteristics are presented in Table 3. The sample had two distinct age groups: 1) six children between seven and 14 years of age and 2) three adults between 18 and 36 years of age. Five children subject pairs were matched within one year of age and one child subject pair was matched within two years of age. Two adult subject pairs were matched within two years of age however, one adult pair had an 18-year age difference. Larger age variance in adult pair seven was not ideal but was tolerated since the most developmentally advanced form of rising occurs in the early teenager years followed by the slow regression toward the less developmentally advanced form of rising. 14 Six subject pairs were matched within 10% of their BMI and three subject pairs were matched within 20%. Five subjects with PWS had a larger BMI in comparison with their control.

Table 3
Table 3:
Subject Characteristics

Movement Descriptors

All UE, AX, and LE rising movement patterns of subjects with PWS (n = 90 per body region) and controls (n = 80 per body region) were successfully categorized, with minor modifications, using the categorical descriptors of Marsala and VanSant. 17

Upper extremity.

The most common UE movement pattern used by the individuals with PWS was pattern two, “push and reach to bilateral push followed by pushing on leg.” Control subjects most commonly used pattern four, “asymmetrical push and reach.” As a group, control subjects’ UE movement patterns were more advanced on the developmentally sequenced scale than the movement patterns used by the individuals with PWS (Figure 1). Because there were 6 UE movement pattern categories, UE body region movement scores could range from a low of 10 to a high of 60. UE body region scores for subjects with PWS ranged from 11 to 38 (mean = 24.2) and for controls ranged from 11 to 46 (mean = 35.8) (Table 4).

Fig. 1
Fig. 1:
Frequency of upper extremity movement patterns (%) for subjects with PWS and controls. Movement patterns: 1, push and reach to bilateral push followed by pushing on leg; 2, push and reach to bilateral push; 3, asymmetrical push followed by pushing on leg; 4, asymmetrical push and reach; 5, symmetrical push; 6, symmetrical reach. Higher movement pattern number reflects a more developmentally advanced movement pattern.
Table 4
Table 4:
Body Region Movement Scores for the UE, AR, and LE for Subjects with PWS and Controls*

Axial Region.

The most common AX movement pattern used by individuals with PWS was pattern two, “full rotation abdomen up” followed closely by pattern three, “partial rotation,” explaining 91.1% of all AX movements. The most common AX movement pattern used by control subjects was pattern four, “forward with rotation.” As a group, control subjects’ AX movement patterns were more advanced than the movement patterns used by the individuals with PWS (Figure 2). Possible AX body region movement scores can range from a low of 10 to a high of 50. AX body region scores for subjects with PWS ranged from 20 to 37 (mean = 26.0) and ranged from 30 to 47 (mean = 35.4) in controls (Table 4).

Fig. 2
Fig. 2:
Frequency of axial movement patterns (%) for subjects with PWS and controls. Movement patterns: 1, full rotation abdomen down; 2, full rotation abdomen up; 3, partial rotation; 4, forward with rotation; 5, symmetrical. Higher movement pattern number reflects a more developmentally advanced movement pattern.

Lower extremity.

The most common LE movement pattern used by subjects with PWS was pattern one, “pike,” however, the choice of movement pattern was scattered among non-adjacent categories, pattern three “kneel” and pattern six “asymmetrical and/or wide-based squat.” The most common LE movement pattern used by control subjects was pattern five “half kneel.” As a group, control subjects’ LE movement patterns were more advanced and clustered among adjacent categories than were the movement patterns used by the individuals with PWS (Figures 2 and 3). Possible LE movement scores could range from a low of 10 to a high of 70. LE body region scores for subjects with PWS ranged from 10 to 60 (mean = 30.56) and in controls ranged from 50 to 56 (mean = 52.78) (Table 4).

Fig. 3
Fig. 3:
Frequency of lower extremity movement patterns (%) for subjects with PWS and controls. Movement patterns: 1, pike; 2, jump to pike; 3, kneel; 4, jump to squat; 5, half kneel; 6, asymmetrical and/or wide-based squat; 7, narrow-based squat. Higher movement pattern number reflects a more developmentally advanced movement pattern.

Body Action Profile

The first three developmentally sequenced movement patterns for each of the body regions comprised the typical Body Action Profile (BAP) of the subjects with PWS (Table 5). These profiles occurred in 67.8% of all the BAPs. The two most common BAPs (UE, AX, LE) used by subjects with PWS were patterns two, two, and one and patterns three, three, and one. The typical BAP of the control subjects were comprised of the more developmentally advanced movement patterns across all body regions. These profiles constituted 65.6% of all the BAPs demonstrated by the control group. The two most common BAPs were patterns four, four, and five and three, four, five. Within subject variability in performance of the rising task was observed in both groups. In general, the subjects with PWS were more likely to use the same movement patterns, as indicated by high frequency of occurrence of a single BAP. A 100% occurrence indicates the subject used the identical three UE, AX, and LE movement patterns for all 10 trials. Variability in the rising task for subjects with PWS ranged from 40% to 100 (mean = 75.55), although variability in control subjects ranged from 30% to 100% (mean = 62.22). Figure 4 illustrates the overall approach to the rising task for subjects with PWS and controls.

Table 5
Table 5:
Frequency (%) of Occurrence of BAP for Subjects with PWS and Controls
Fig. 4
Fig. 4:
Side view of a common movement pattern profile in subjects with PWS (left) and controls (right) rising from a supine position to a standing position. Subjects with PWS used “push and reach to bilateral push followed by pushing on the leg” pattern of the upper extremity, “full rotation, abdomen up” pattern of the axial region, and “pike” pattern of the lower extremity (movement pattern 1,2,1). Controls used “asymmetrical push and reach” pattern of the upper extremity, “forward with rotation” pattern of the axial region, and “half kneel” pattern of the lower extremity (movement pattern 4,4,5). Julia Anastasia Levitina, illustrator.

Duration

The average elapsed time for completion of the rising task was 5.4 and 2.86 seconds for subjects with PWS and control subjects, respectfully. For each matched pair, the control subject was able to rise quicker than the subject with PWS (Fig. 5).

Fig. 5
Fig. 5:
Comparison of subject pairs average duration to complete the rising task (seconds) across all 10 trials.

Age-Related and BMI-Related Effects on Movement Patterns

The correlations between body region movement score and age for subjects with PWS were rho = 0.15 UE, −0.25 AX, and −0.09 LE and rho = −0.17 UE, −0.18 AX, 0.09 LE for control subjects. As age increased, scores neither increased nor decreased noticeably for either subject group. Regardless of diagnosis, there was a poor correlation between body region movement score and age (rho = 0.01). No discernible relationship appeared between age and any of the three body movement scores. However, the small sample size and wide age range makes it difficult to accurately assess the effects of age on the rising task.

The correlations between body region movement score and BMI for subjects with PWS were rho = 0.09 UE; −0.30 AX, −0.15 LE and for control subjects rho = −0.17 UE, −0.18 AX, 0.09 LE. Regardless of diagnosis, there was a poor correlation between body region movement score and BMI (rho = 0.01). Again, no relationship was found between BMI and any of the three body region scores.

DISCUSSION

Application of Movement Descriptors

One of VanSant’s original contributions was categorizing movement descriptors for the rising task. 14 A limited number of published and unpublished works have applied these categories to individuals with disabilities such as CP, DMD, and Down syndrome. 20–22 We extended these observations to individuals with PWS. The movement descriptors as described by Marsala and VanSant 17 were accurate and sufficiently comprehensive to describe the movements used by individuals with PWS when rising from supine. The descriptors provided a reliable, systematic, and objective system for examining the rising task. A degree of sophistication of the rising task was captured by the component analysis of the UE, AX, and LE body regions and was linked with quantifiable measures of within subject and between subject variability as well as performance duration. Our findings concur with other investigators on the usefulness of the descriptors in individuals with and without neuromuscular impairments. 21,22

Within the group of subjects with PWS, Marsala and VanSant’s movement pattern descriptors were not always as effective in illustrating the qualitative differences within each movement pattern category. The LE movement patterns provide a solid example of this issue. Subjects six and eight with PWS both performed LE movement pattern six, “asymmetrical and/or wide-based squat,” 100% of the time, but the technique and quality of their movement were remarkably different. In all 10 trials, subject eight crossed her ankles, brought both feet simultaneously toward her buttocks, and rose smoothly to an erect stance from this narrow-asymmetrical base. Subject six rose from a wide-based squat with considerable UE and AX repositioning and movement. This first example is one of control, efficiency, and coordination of movement, while the second example is not. Pattern six, “asymmetrical and/or wide-based squat,” encompasses both these very distinct LE strategies. Clarification and modifications were necessary in several of the movement descriptors for all three body regions.

Upper extremity.

In pattern one of the UE, “push and reach to bilateral push followed by pushing on leg” there was a discrepancy in both the title and description. The title specifies a “push” on the knee, whereas the description (“one or both hands are placed on the knee”) stipulates that the hand is “placed” on the knee. Additionally, we felt it would be more comprehensive to change the descriptor to read “some part of one or both upper extremities are placed on the knee.”

UE movement patterns one, “push and reach to bilateral push followed by pushing on leg” and pattern two, “push and reach to bilateral push” stipulate that one arm reaches “across” the body. It was found that some subjects reached forward to a bilateral push, but did not necessarily reach across the body to arrive at the bilateral hand placement on the support surface. We felt that the description as written is too explicit and masks extraneous movements used before reaching bilateral push.

Axial region.

During data reduction of the AX region, the only difficulties encountered were in establishing clear boundaries between pattern three, “partial rotation” and pattern four, “forward with rotation.” A decision rule was used whereby “partial rotation” was defined as shoulder girdle rotation beyond 45 degrees in relation to the pelvis. “Forward with rotation” was defined as including all rotation less than 45 degrees from perfect symmetry. We determined that the “forward with rotation” category was too broad because an individual who rose symmetrically with only slight rotation at the end of the rising task shared the same classification as a subject who clearly struggled and could not have risen without rotating up to 45 degrees throughout the entire task. We found that 71% of all control subjects clearly fell within this classification and felt it represented too wide a range of ability. The abundance of subjects classified “forward with rotation” could have been compounded by the excessively stringent criteria needed to qualify for the most advanced category, pattern five, symmetrical,“ as demonstrated by the dearth of subjects classified in this category.

Lower extremity.

Two movement patterns needed additional clarification. None of the subjects, with or without PWS, performed the “pike” with fully extended legs, as stipulated in the movement pattern descriptors. Therefore, in this study, we amended the criteria for “pike” to include the hips above the height of the shoulders with the knees at 90 degrees or less of flexion. If both criteria were not satisfied, the movement was not considered “pike.” Marsala and VanSant 17 also redefined the “pike” description category to read “characterized by the position of the LE’s with respect to the trunk during the process of rising. . .the knees were relatively extended as the hips assumed an acute angle of flexion.” This redefinition agrees with our decision rule clarifying the same pattern. The other pattern clarified was the “asymmetrical and/or wide-based squat.” We determined that a wide-based squat was achieved if the feet were placed greater than, or equal to, hip width apart. A second criterion was that the hips remained below shoulder height.

Intergroup Comparisons of Rising Movement Patterns

The determination that descriptors were applicable to persons with PWS allowed us to compare the movement patterns to those of control subjects. There were clear performance differences in the rising task between the subjects with and without PWS. Subjects with PWS consistently demonstrated less developmentally advanced movement patterns in the UE, AX, and LE body regions, took longer to rise, and showed less within subject variability than those exhibited by the control subjects. The subject differences held true, even among the subject pairs that were not ideally matched for BMI and age. Regardless of the parameters used to organize the data or to group the subjects, the decisive distinction between those who demonstrated less developmentally advanced and those who demonstrated more developmentally advanced patterns, in this study, was the diagnosis of PWS.

When reviewing group data, the movement pattern most frequently demonstrated by subjects with PWS was at least two patterns less advanced on Marsala and VanSant’s developmentally sequenced scale than that chosen by the control subject. This was true for each body region. Overlap was noted between the subject groups for each body region, meaning that for every body region some movement patterns were exhibited by subjects with and without a diagnosis of PWS. However, for each region the most developmentally advanced pattern chosen was used solely by the control group, with two notable exceptions.

The pair-eight subject with PWS differed from other PWS subjects and her matched control in her markedly superior fitness appearance and reported participation in a vigorous exercise program. This subject exhibited variability similar to that of her matched pair and demonstrated movement patterns that were closer aligned for her age on the developmentally sequenced scale. The predominant body action profile (UE, AX, LE) performed in this subject with PWS was patterns two, four, and six (50% occurrence rate across 10 trials) and four, four, and five in the control subject (90% occurrence rate across 10 trials). Perhaps the improved fitness or training contributed to the more developmentally advanced rising performance. In pair nine, the control subject had received physical therapy six years prior for a back injury. At that time, she was instructed in a safe and pain-free rising method that consisted of less developmentally advanced movement patterns. The predominant body action profile (UE, AX, LE) performed by the pair-nine subject with PWS was patterns three, three, and three and by the control subject was one, three, and five. Both subjects demonstrated a 90% occurrence rate across all 10 trials. It is possible that because of the PT instruction she received, she was not rising in a spontaneous matter, rather she opted to perform what she believed was the “correct” technique. Subjects with prior PT interventions that stipulate a specific rising method may need to be added to the exclusion criteria of future studies. Interestingly, when comparing matched pairs, including these two notable exceptions, control subjects were still shown to rise more quickly than the subjects with PWS. Duration data may add an additional, sensitive, quantitative measure, along with the movement descriptions, in discriminating between rising performances of subjects with and without disability.

Rising movement patterns of persons with PWS.

Two body action profiles described the majority of rising patterns found in subjects with PWS: 1) push and reach to bilateral push (UE), full rotation abdomen up (AX), and pike (LE); and 2) asymmetrical push followed by pushing on leg (UE), partial rotation (AX), and pike (LE). These profiles used the earlier and asymmetrical developmental patterns most similar to those described by healthy toddlers. 17 The rising patterns of subjects with PWS were performed in a rather slow manner and were characterized by multiple transitional postures, four-point arm and leg contact against the surface throughout the rising motion, placement or pushing of the arms on the thighs to assist with upright stance, minimal dissociation of the UE and LEs, and substantial trunk rotation. The selected rising patterns may be explained partially by the impairments frequently associated with PWS including decreased muscle strength, skeletal variations, decreased metabolic rate, decreased physical activity, decreased energy expenditure, and obesity. Hyman and Mehta 21 found that strength had a direct impact on the movement patterns selected in children with DMD; the child with the lowest strength score used less developmentally advanced movement patterns in comparison with the child with the greatest strength. Transitional postures were seen in healthy older subjects and in young children as points for attaining balance. 18

Subjects with PWS averaged 5.4 seconds to rise. This duration was slower than control children and adults (mean = 2.86 seconds) used in this study but faster than the rising time reported for children with DMD (mean = 7.29 seconds). The longer duration for rising could alter the selected movement pattern and require an increased demand for postural control. Hyman and Mehta 21 found a significant, inverse relationship (rho = −0.96) between strength and time to complete the rising task in children with DMD.

Rising movement patterns of control subjects.

Two body action profiles of the UX, AX, and LE region described the majority of rising patterns found in control subjects: 1) asymmetrical push and reach push, forward with rotation, and kneel; and 2) asymmetrical push followed by pushing on leg, forward with rotation, and half kneel. The profiles are most similar to those described by VanSant 15 for healthy four- to seven-year-old children. In general, control subjects retained the asymmetrical, wide-based rising pattern rather than exhibit the more symmetrical, narrow-based rising pattern seen in teenagers and young adults. Direct age comparisons of subjects in this study to published descriptors of healthy subjects for rising is difficult given the changes in movement descriptors and wide variations in ages studied. It seems that seven of the nine control subjects’ rising performances were less developmentally advanced for their age in comparison with published descriptors. Six of these seven control subjects were classified as obese when compared with normal values for age and/or gender. These finding correspond to these of Gillon et al 25 who found that children (seven to 12 years of age) with a BMI at or above 85th percentile for their age differed from previously reported movement patterns of the same age who were not obese performing asymmetrical and rotational movements. Obesity alone, however, does not account for all the less developmentally advanced movement patterns in this study. Perhaps impairment measures, such as activity level and strength, in combination with obesity, determine the selected movement patterns.

PT Implications

Component analysis studies of the rising task in individuals with and without disability provide a framework for PT interventions. The qualitative (movement descriptors of the UE, AX, LE; body action profiles) and quantitative (duration, body region scores, variability) nature of the rising task can be assessed and successful rising strategies demonstrated to persons with PWS who have difficulty rising.

CONCLUSIONS AND LIMITATIONS

Limitations of this study include the small sample size, the wide age range, imperfect matching, and the use of a nonspecific questionnaire for gathering data on activity level and PT intervention. Minor modifications in the movement descriptors by Marsala and VanSant 17 allowed the rising movement patterns of persons with PWS to be categorized successfully. The rising strategies of individuals with PWS differ from those without PWS. The movement strategies of children with PWS in this study are less developmentally advanced than their age- , gender- , and BMI-matched peers.

ACKNOWLEDGMENTS

The authors thank Dr. Ronald Demeersman for use of his laboratory space and equipment; Drs. Morris Angelo, Thomas Starc, and Sarah Couch and the Fresh Youth Initiatives Community Center for assistance in recruiting participants; and Dr. Ann VanSant for generously giving of her time and expertise in training the authors in component analysis of the rising task. Most importantly, we thank the participants and their families.

FOOTNOTES

*Boldtext depicts modifications from Marsala and VanSant17published descriptors.
Cited Here

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APPENDIX

Modified Movement Pattern Descriptors

Upper Extremity Movement Categories

  1. PUSH AND REACH TO BILATERAL PUSH FOLLOWED BY PUSHING ON LEG
  2. One or both hands are placed on the supporting surface beside the pelvis. After an initial push, one arm reaches across the body and the hand is placed on the surface. Both hands push against the surface to an extended arm position. Some part of one or both upper extremities* are placed on the knee, and then the arms are lifted and used for balance.
  3. PUSH AND REACH TO BILATERAL PUSH
  4. One hand is placed on the support surface beside the pelvis. The other arm reaches across the body and the hand is placed on the surface. Both hands push against the surface to an extended elbow position. The arms are then lifted and used for balance.
  5. ASYMMETRICAL PUSH FOLLOWED BY PUSHING ON LEG
  6. One or both arms are used to push against the support surface, or to reach. Pushing and reaching movements give way to single arm push against the support surface. Some part of one or both upper extremities are placed on the knee, and then the arms are lifted and used for balance.
  7. ASYMMETRICAL PUSH AND REACH
  8. One or both arms are used to push against the support surface. If both arms are used, there is an asymmetry or asynchrony in the pushing action or a symmetrical push gives way to a single push pattern.
  9. SYMMETRICAL PUSH
  10. Both hands are placed on the surface. Both hands push symmetrically against the surface prior to the point when the arms are lifted synchronously and used to assist with balance.
  11. SYMMETRICAL REACH
  12. The arms reach forward leading the trunk and are used as balance assists throughout the movement.

Axial Region Movement Categories

  1. FULL ROTATION ABDOMEN DOWN
  2. The head and trunk flex and rotate until the ventral surface of the trunk contacts the support surface. The pelvis is elevated to or above the level of the shoulder girdle. The back extends up to the vertical, with or without accompanying rotation of the trunk.
  3. FULL ROTATION ABDOMEN UP
  4. The head and trunk flex and/or rotate until the ventral surface of the trunk faces, but does not contact the support surface. The pelvis is then elevated to or above the level of the shoulder girdle. The back extends from this position up to the vertical, with or without accompanying rotation of the trunk.
  5. PARTIAL ROTATION
  6. Flexion and rotation bring the body to a side facing position of shoulder girdle rotation beyond 45 degrees in relation to the pelvis, with the shoulders remaining above the level of the pelvis. The back extends up to the vertical, with or without accompanying rotation.
  7. FORWARD WITH ROTATION
  8. The head and trunk flex forward with or without a slight degree of rotation, less than 45 degrees from perfect symmetry. Symmetrical flexion is then interrupted by rotation or extension with rotation. Flexion with slight rotation is corrected by counter-rotation in the opposite direction. One or more changes in the direction of the rotation occur. A front or slightly diagonal facing is achieved before the back extends to the vertical.
  9. SYMMETRICAL
  10. The head and trunk move symmetrically forward past the vertical; the back then extends symmetrically to the upright position.

Lower Extremity Movement Categories

  1. PIKE
  2. The legs are flexed toward the trunk and may be rotated to one side with knees or a knee and foot in contact with the ground. Both feet then contact the support surface. The legs are extended with the hips greater than the height of the shoulders with the knees at 90 degrees or less of flexion, into a pike position. Slight flexion of the legs is followed by extension during the rise to erect stance.
  3. JUMP TO PIKE
  4. The legs are flexed toward the trunk and rotated until both knees contact the support surface. The feet are then placed in contact with the support surface while the legs remain flexed. Next, the legs may be fully extended to a pike position. Both feet are then lifted simultaneously off the support surface. The feet land back on the support surface in closer proximity to the hands, with the hips and knees flexing to squat position. The legs are then extended during rise.
  5. KNEEL
  6. The legs are flexed toward the trunk and rotated to one side with both knees contacting the support surface. Half kneeling may be assumed or a squat pattern. When the legs extend, one or more balance steps may be taken.
  7. JUMP TO SQUAT
  8. The legs are flexed and/or rotated to one side. Both legs are then lifted simultaneously off the support surface and may be derotated. The feet land back on the support surface with the hips and knees flexing to a squat or semi-squat position. The legs then extend to the vertical.
  9. HALF KNEEL
  10. Both legs are flexed toward the trunk as one or both legs are rotated to one side. One leg is then flexed forward to assume half kneeling in which the top knee never touches the support surface. The forward leg pushes into extension as the opposite leg moves forward and extends.
  11. ASYMMETRICAL AND/OR WIDE-BASED SQUAT
  12. One or both legs are flexed toward the trunk assuming an asymmetrical, crossed-leg or wide-based squat. Wide based is defined as the feet placed greater than or equal to hip width apart. A squat requires that the hips remain below shoulder height. The legs push into an extended position. Crossing or asymmetries may be corrected during extension by stepping action.
  13. NARROW-BASED SYMMETRICAL SQUAT
  14. The legs are brought into flexion with the heels approximating the buttocks in a narrow-based squat. Stepping action may be seen during assumption of the squat or balance steps (or hops) may follow the symmetrical rise.
Keywords:

adult; child behavior disorders; child development/classification; movement/physiology; comparative study; Prader-Willi Syndrome/complications

Copyright © 2001 Academy of Pediatric Physical Therapy of the American Physical Therapy Association