Quantification of control: a preliminary study of effects of neurodevelopmental treatment on reaching in children with spastic cerebral palsy.

Many children with cerebral palsy receive physical therapy services throughout their childhood and adolescence, yet few data exist to support the effectiveness of therapy for these children. (1-3) Research on the effectiveness of physical therapy in individuals with cerebral palsy has focused primarily on measuring the attainment of functional or gross motor skills; however, few studies have demonstrated measurable change using these variables. Alternative measures are necessary to determine the nature of change in cerebral palsy.

Older children with spastic cerebral palsy are more likely to exhibit a change in quality of movement than to acquire new functional skills. (4) These qualitative changes may include improvements in biomechanical alignment during voluntary movement and postural maintenance, improved gradation of movement with increased eccentric muscular control, and improved stability at proximal body parts to allow distal body parts to move with greater control. Following treatment, movement may be easier to initiate, faster, smoother, and more efficient (decreased energy cost).

These qualitative changes in the movement pattern are often not detected because of the lack of methods of systematically defining and recording the qualitative aspects of movement. Therapists often use gross observation, anecdotal reporting, and imprecise descriptive terminology to assess movement quality. These methods may limit objectivity, accuracy, and reproducibility. Recording motion for later analysis provides therapists with a means for repeated review of patient movement, allows others to review the same movements, and affords a potential method for precise and systematic definition of qualitative aspects of movement.

We have used both kinematic and videotape recording and analysis to describe the pretreatment and post-treatment reaching abilities of preadolescent-children with cerebral palsy. These two methods offer systematic and reproducible means for describing change in the reaching pattern following treatment even before functional changes become evident. (5) The present study thus had two objectives. The first objective was to develop a means for the systematic description of some of the qualitative aspects of movement. The second objective was to investigate the effectiveness of physical therapy, specifically neurodevelopmental treatment (NDT), on the reaching abilities of children with cerebral palsy.

Reaching is a necessary component of many daily functional tasks and is representative of well-learned, highly skilled movements. Children with spastic cerebral palsy might be expected to have problems with the components of reaching. Faulty postural control mechanisms, abnormal muscle tone, excessive co-contraction during attempted movement, and abnormal reflex activity contribute to movement problems such as difficulty initiating movement, impaired smoothness and efficiency of the reach, and limited range of movement, thus affecting the accuracy of reach. (6-9)

Kinematic variables used to describe movement include movement time (MT), shape of the movement path, velocity, and acceleration. With treatment, the ability to initiate reaching may improve, resulting in a shorter reaction time and overall duration of reach. if control has improved, the hand path may be shorter and less variable. Movement may become smoother with improved muscle coordination, which may be reflected in the velocity and acceleration profiles.

A movement unit (MU) has been defined as the portion of a reach between one acceleration and one deceleration (10,11) and as the portion of the reach between subsequent points in a curvature-speed relationship. (12) Both definitions enable systematic description of the stop-start action or jerkiness of a reach. Infant reaches initially include multiple MUs, with the number of MUs decreasing with maturity. As reaching patterns mature, the first MU accounts for an increasing percentage of the total duration of the reach. (10) The jerky stop-start action gives way to one smooth, continuous acceleration followed by a single deceleration. A mature reach consists of a single MU with only one stop-start action.

These findings suggest that a lower number of MUs reflects greater control of the reaching movement. Thus, counting the number and relative timing of MUs may offer a useful operational definition for control or coordination. Children with cerebral palsy often have difficulty producing smooth movement. Movement units offer a method for quantifying the "amount of smoothness" in a reach. If treatment has affected the smooth quality of the reach, this change can be quantified by counting the number of MUs before and after treatment.

In kinematic analysis, specific body parts are chosen for identification, with other body parts indirectly involved in the movement ignored. Videotape analysis can be used to evaluate body movement not directly recorded for kinematic analysis. For instance, the nonreaching hand may pull into a flexor synergy with the effort of reaching. This type of response should decrease following treatment because movement then requires less effort, muscle tone is decreased, and postural stability is increased.

The primary purpose of this study was to determine whether reaching movement skills of children with spastic cerebral palsy are amenable to change following one session of NDT. In addition, we sought to determine whether changes in reaching movements can be observed and systematically described using kinematic and videotape methods of recording and analysis. We hypothesized that improvements in reaching patterns would be reflected in shorter, decreased movement durations; decreased associated reactions in the nonreaching hand; increased directness of the reach as measured by the length of the path of the hand toward the target; and increased smoothness of reach in terms of the number and quality of MUs in the acceleration profiles.

Method

Subjects

Five children, each with a diagnosis of spastic quadriplegic cerebral palsy, participated in the study. The children ranged in age from 7 to 12 years ([.bar.over.]X = 9.2, s = 2.2). Background information regarding each subject is presented in Table 1 [omitted]. Muscle tone was evaluated as increased or decreased from normal or fluctuating. The degree of deviation from normal tone was classified as mild, moderate, or marked. Interrater reliability for this method of muscle tone assessment was determined by having each subject evaluated separately by two physical therapists. The therapists used the descriptors of muscle tone shown in Table 1 [omitted]. The level of agreement between the two therapists was 80%. All subjects demonstrated increased muscle tone in all four extremities.

Subjects were selected from the Cotting School (Lexington, Mass), an academically oriented school for children with physical handicaps. Each subject met the following criteria: 1) have ability to understand and carry out the verbal directions included in the reaching task, 2) have sufficient visual skill to localize an object with both eyes, 3) have sufficient passive range of motion to be able to reach the target, and 4) have a letter of informed consent signed by his or her parent(s). The project received approval from the Sargent College of Allied Health Professions Research Review Board.

Procedure

Subjects reached to touch a 2-in*-tall plastic toy man. The target was securely positioned on top of a box that was fastened to a tabletop. The target was placed in front of the subject at midline. The child was seated at the table in his or her wheelchair or in another chair appropriately fitted to provide postural stability. The target was located so that the child's hand easily touched it when the child's arm was passively placed at 90 degrees of shoulder flexion with full elbow extension. In this way, target distance could be scaled for each subject.

Subjects performed the reaching task with their preferred hand . Each trial of the reaching task began with both hands placed directly in front of the subject on hand-shaped colored paper taped to the tabletop. The subject was asked to touch the target when the examiner gave the command "go." Each child was allowed two or three practice reaches before recording and filming began.

Each subject participated in one testing session during which performance of the reaching task was recorded immediately before and following a 35-minute NDT-oriented therapy session. Reaching movements were recorded both before and following the treatment session for comparison. The number of trials of the reaching task performed at one time depended on the child's level of fatigue and motivation. Each therapy session was conducted by a pediatric NDT-certified physical therapist (JK). Although specific treatment activities varied for each subject, overall goals for all subjects were the same, Goals included improved trunk and shoulder-girdle control during reaching, improved smoodiness and efficiency of movement, and improved ability to initiate movement. All sessions incorporated handling techniques that attempted to alter muscle tone during movement and to facilitate appropriate weight shifting and postural reactions. A brief description of the goals and activities of each treatment session is included in the Appendix.

Instrumentation

Reaching movements were recorded using the WATSMART [TM] (Waterloo Spatial Motion Analysis and Recording Technique).+ infrared light-emitting diodes (IREDs) were attached to the skin over the styloid process of the ulna and the target. This distal limb point was used to represent the arm in space. Two cameras, sensitive to the infrared light spectrum, recorded the position of the arm at a sampling rate of 100 Hz. The single IRED was attached to the distal limb point by taping a small Velcro [R]++ hooktape strip to the skin and gluing the Velcro [R] touch fastener to the back of the IRED. Thus, the IRED could be easily removed for treatment and reattached at exactly the same place after treatment. The position of the IRED on the child's wrist, therefore, was kept constant preceding and following treatment. The position of the IRED during each reach was stored as numerical coordinates, which were later converted to three-dimensional numerical values. A PC Limited 286 computer @ was used for data collection, storage, and analysis of the positional data.

The reliability values for reproducing a fixed target length (ruler) rotated in three-dimensional space in our laboratory were below 2 mm. That is, the WATSMART [TM] system reproduced the absolute length of the moving ruler with errors of 2 mm or less. The validity and reliability of the WATSMART [TM] system have been reported previously. (4)

Reaching movements were also recorded on videotape. A Panasonic Model NB-8950 video recorder, ~~ with frame-by-frame analysis capability, was coupled with a Panasonic Model WJ-time-date 810 generator ~~ to isolate the precise reaching motions to be used for study. Time, in 0.01-second intervals, was displayed and recorded on the videotape. Video and WATSMART [TM] data systems were activated simultaneously by the examiner as the command "go" was given to the subject.

Data Reduction

Video data. Movement time and the extent to which associated reactions occurred during each reach were determined by analyzing the videotapes. Movement time was defined as the period of time between visible movement initiation and actual contact with the target. As previously mentioned, MT was recorded from the time generator on the video screen. if a subject was unable to touch the target within the 5-second period for which data were collected, then 5 seconds was recorded as the end of the reach and used to calculate MT.

The extent to which associated reactions occurred was determined by calculating the amount of time the nonreaching hand remained on the table and dividing that amount by the sum of the MT and the reaction time. Interrater reliability for coding video data was high, ranging from complete agreement to maximum disagreement of 0.1 second (1 1/2 frames) when determining MTs and reaction times and occurrence of associated reactions in the nonreaching hand. Video data were collected for a total of 139 reaches of which 105 were used for data analysis. Reaches were excluded from the data analysis if movement preceded onset of data collection (false starts), if the child was not looking at the target, if the child did not make any response to the command, if the timer was not initiated by the examiner, or if it was difficult to determine on videotape at what point the target was actually touched.

Kinematic data. Of the 139 reaches for which data were collected, 87 were used in the kinematic data analysis. Data were eliminated if the wrist IRED was obscured from camera view for more than 10% of the MT during one reach. Data were extrapolated with a linear spline if fewer than 10% of the data were missing. This careful elimination, as opposed to extrapolation of missing data, contributed to the unequal number of trials per subject. The difficulty of the reaching task, particularly for Subject C, also contributed to the unequal number of trials.

Numerical data were filtered at 5 Hz using a second-order Butterworth filter with forward and reverse passes. The three-dimensional displacement data from the x, y, and z planes were combined to produce a single displacement coordinate for each frame of movement. From this information, the distance the IRED traveled during the reaching motion was calculated by determining the distance the IRED moved between each frame of recorded motion. Accelerations were calculated as the second-order derivatives of the position coordinates. Acceleration data were graphed and visually analyzed. The number of MUs was counted from these graphs.

A movement unit was defined as one acceleration and one deceleration, with a minimum rate of change of speed of 5 mm/sec[.sup.2] to qualify as an acceleration or a deceleration. (11) The percentage of the reach during which the first MU occurred was determined by dividing the total MT by the duration of the first MU and multiplying by 100.

Data Analysis

Data were analyzed in two ways. First, data from all subjects' reaches were pooled and two-way analyses of variance (ANOVAs) for repeated measures (treatment x trial) were performed. Analyzing the aggregate data allows for the more conventional study of treatment effects across a group of children with cerebral palsy. A problem in studying children with cerebral palsy, however, is the heterogeneity of the group. (1,3,4) Each child is unique in specific movement skills and problems, as well as in responses to treatment. Some subjects may benefit from treatment, whereas others do not. Each subject's graphed data, therefore, were analyzed by visual inspection and by the two-standard-deviation band method, a method designed for single-subject data. (13)

When using the two-standard-deviation band method of analysis, two horizontal lines are drawn across the graphed baseline and post-treatment data. These lines are located two standard deviations above and below the mean of baseline data. Statistical significance is demonstrated if two successive data points occur outside the two-standard-deviation band. This method may be used when a limited number of baseline data points are available and when there is wide variability in the baseline data. This method, however, is sensitive to serial dependency, which occurs when one performance correlates with and predicts the next performance. An autocorrelation coefficient can be calculated to determine whether data are serially dependent. In this study, none of the baseline data were found to be significantly serially dependent. Therefore, the two-standard-deviation band method was applied to the data.

We chose the .10 level of significance for data analysis. This choice was made to avoid the chance of committing a Type II error, that is, assuming no significant difference posttreatment when a significant difference actually does exist. This level of significance is a reasonable choice with a small sample size such as that in this study and in light of the data that will be presented. (14)

Results

Aggregate Data

Movement time decreased significantly following treatment (F = 12.18; df = 1,4;p < .025). The number of MUs per reach also decreased significantly following treatment (F = 5.71; df = 1,4; P < 075). The duration of the first MU in relation to the entire MT was significantly greater following treatment (F = 17.71 1 df = 1,4; p < .025).

The length of the path that the hand traveled (straightness) (F = 0.48; df = 1,4) and the extent to which associated reactions occurred (F = 0.29; df = 1,4) did not differ significantly with treatment. Results of the ANOVA for all variables are shown in Table 4.

A trial-effect analysis was performed on the pretreatment and posttreatment data for the variables of MT, number of MUs, and percentage of the total MT accounted for by the first MU. In this way, we could determine whether changes occurred as a function of practice during the testing session. Because there were an unequal number of trials per subject, we performed the trial-effect analysis by including the maximum number of trials for each subject, then excluding the subject data with the fewest trials and conducting the analysis again. For example, Subject C had only three reaches that could be used in the kinematic analysis. The trial analysis was first run for all subjects using only three trials. As a second step, Subject C's data were eliminated and the analysis was repeated for six trials because Subject B had the next limiting number of trials. Each variable was analyzed in this way. Table 4 represents a typical analysis, rather than all the values generated from these analyses. There were no significant trial effects for either pretreatment or posttreatment reaches for MT (F = 0.21; df = 6,24), the number of MUs (F = 0.02; df = 6,24), or the percentage of the total MT accounted for by the first MU (F = 0.02; df = 6,24).

Single-Subject Data

The results of this analysis are similar to those of the grouped data, with a decrease in MT and a longer duration of the first MU relative to the entire MT of the reach for most subjects. Important individual differences among the subjects, however, were found. Subjects A and E demonstrated the greatest changes following treatment, whereas Subject B did not demonstrate significant changes on the chosen variables. Single-subject data are graphed in Figures 4 through 7 [omitted].

Baseline and posttreatment reaches made by Subject A differed significantly using the two-standard-deviation band method of analysis, with a decrease in MT, an increase in the duration of the first MU relative to the total MT, and a decrease in the distance of the path of the hand. This subject also demonstrated a decrease in the number of MUs per reach, although no posttreatment data points fall outside the two-standard-deviation band. Prior to treatment, each of this subject's reaches consisted of more than one MU. Following treatment, half of her reaches consisted of only one MU, indicating a more mature reaching pattern.

Subject E's reaches appeared to be faster (decreased MT) following treatment, but not significantly. The number of MUs per reach did not appear to change with treatment. The duration of the first MU relative to the total MT, however, did appear to increase following treatment, although not significantly. The

two-standard-deviation band method of analysis revealed significant increases following treatment in the distance the hand traveled.

Subject C made the greatest observable gain in ability to touch the target accurately with reduced MT following treatment. This subject never touched the target before treatment; therefore, graphing her data and computing a standard-deviation band was not possible. However, it is clinically important that, although prior to treatment she was unable to touch the target, following treatment she was able to accurately touch the target in seven out of eight trials. Subject C demonstrated an increase in the degree of associated reactions following treatment. This increase may be a reflection of the effort necessary for this subject to actually touch the target. only three baseline and three posttreatment reaches of this subject met the criteria for coding acceleration data and for determining the distance of the path of the hand. This was an insufficient number of data points for comparing pretreatment and posttreatment reaches using single-subject data analysis.

Movement time of Subject D's reaches decreased following treatment, though not significantly. Subject D demonstrated a significant reduction in the occurrence of associated reactions in his nonreaching hand following treatment. Prior to treatment, Subject D was able to keep his nonreaching hand on the table throughout the entire reach only once out of 10 attempts. Following treatment, he was able to keep his nonreaching hand on the table during the entire reach for 10 out of 11 trials. Movement unit data did not differ significantly between baseline and posttreatment reaching trials for this subject.

Discussion

When data from the individual subjects were pooled, three of the variables chosen for study changed following treatment. Movement time and the number of MUs decreased. In addition, the duration of the first MU relative to the total MT increased after treatment, suggesting a more controlled reach. The distance of the path the reaching hand traveled remained stable across treatment for four subjects. This finding suggests that decreased MT following treatment is related to an actual change in speed of movement as opposed to the hand simply moving across a shorter distance. Muscle pattern activation may not have changed posttreatment because a straighter path might require such a change. Instead, the speed of activation of the available pattern may have increased. This possibility could be confirmed by the use of electromyography in future studies. Practice during testing does not account for the changes observed. The trial analysis suggests that the subjects' reaching ability did not improve merely because they practiced the task. A change occurred between testing sessions that we attribute to factors other than practice. Clearly, in order to attribute these changes to therapy, we need to have additional experimental conditions, that is, alternatives to therapy or alternative therapies.

Reaching movements became significantly faster following treatment. Movement times for subjects in the present study, however, were still longer than those reported for reaching tasks performed by healthy 5- to 9-month-old infants (12) or healthy 1.5-to 8-year-old children (15) (Tab. 5). In addition, our subjects demonstrated wider variability in their MT than 5-to 9-month-old infants (12) or 1.5- to 8-year-old children. (15)

In this study, the number of MUs decreased and the duration of the first MU relative to the total MT increased following treatment. These findings suggest that a lower number of MUs reflects smoother movement and that the smoothness of movement can be quantified and is amenable to change with intervention.

There was a period at the end of many of the reaches characterized by numerous small accelerations and decelerations, which were too small to be considered MUs. Figure 8 [omitted] is an example of this prolonged period at the end of a reach. These periods coincided with the hand placement near, but not yet on, the target. Apparently, the subjects were getting the hand to the target in one of the first two MUs and then taking additional time orienting the hand to touch the target.

Jeannerod suggests a dual system of upper extremity movements. (16) Reach (limb projection) is separate from hand-orienting movements and subject to different control strategies and stimulus properties. With maturation, the hand-orienting and limb-projection phases are timed appropriately for the stimulus requirements. Our subjects appeared to demonstrate both of these unique strategies, with the clear limb-projection phase followed by hovering at the target, characterized by the small-amplitude accelerations and decelerations. This "tail" on the acceleration profile at the end of the reach decreased in length following treatment for four of the five subjects. This finding, coupled with the decreased number of MUs and the increased duration of the first MU relative to the total MT following treatment, suggests that the ability to simultaneously reach with the arm while orienting the hand to the target improved following treatment.

Conclusions

We are encouraged by the results of this study for two reasons. First, kinematic data analysis is sensitive to change and offers operational definitions for heretofore casual descriptors. Second, the type of treatment used in this study produced measurable and functional results. Some of our subjects reached faster and used a more mature pattern following treatment.

The logical next step in our research is to increase the sample size and to include additional types of treatment and control groups in each study. The NDT approach used in this study may have benefited the subjects for a variety of reasons, and the specific reasons need to be clarified. In addition, we want to investigate how long the treatment effects last. Future research will control these added possibilities utilizing the kinematic definitions developed in this study.

Acknowledgments

We thank the children and families who participated in this study and Martha Carr for her assistance with data collection.

Footnotes

* 1 in= 2.54 cm

+ Northern Digital inc, 415 Phillip St, Waterloo, Ontario, Canada N21 3X2.

++ Velcro USA Inc, PO Box 5218, 406 Brown Ave, Manchester, NH 03108.

@ Dell Computer Corp, 9505 Arboretum Blvd, Austin, TX 78759.

~~ Panasonic Industrial Co, One Panasonic Way, Secaucus, NJ 07904.

References

1 Henderson A: Research in occupational and physical therapy with children. Advances in Behavioral Pediatrics 2:33-59, 1981

2 Ottenbacher KJ, Biocca Z, DeCremer G, et al: Quantitative analysis of the effectiveness of pediatric therapy: Emphasis on the neurodevelopmental treatment approach. Phys Ther 66:1095-1101, 1986

3 Parette HP, Hourcade JJ: A review of therapeutic intervention research on gross and fine motor progress in young children with cerebral palsy. Am J Occup Ther 38:462-468, 1984

4 Scherzer AL, Tscharnuter I: Early Diagnosis and Therapy in Cerebral Palsy: A Primer on Infant Developmental Problems. New York, NY, Marcel Dekker Inc, 1982

5 Scholz JP: Reliability and validity of the WATSMART [TM] three-dimensional optoelectric motion analysis system. Phys Ther 69:679-&9, 1989

6 Bobath B: The treatment of neuromuscular disorders by improving patterns of coordination. Physiotherapy 55:18-22, 1969

7 Bobath K, Bobath B: Cerebral palsy. in Pearson PH, Williams CE (eds): Physical Therapy Services in the Developmental Disabilities. Springfield, IL, Charles C Thomas, Publisher, 1972, pp 37-185

8 Bobath B, Bobath K: Motor Development in the Different Types of Cerebral Palsy. London, England, William Heinemann Ltd, 1975

9 Erhardt RP: Developmental Hand Dysfunction: Theory Assessment Treatment. Laurel, MD, Ramsco, 1982

10 von Hofsten C: Development of visually directed reaching: The approach phase. Journal of Human Movement Studies 5:160-178, 1979

11 Brooks VB: Some examples of programmed limb movement. Brain Res 71:2991--308, 1974

12 Fetters L, Todd J: Quantitative assessment of infant reaching movements. journal of Motor Behavior 19:147-166, 1987

13 Ottenbacher KJ: Evaluating Clinical Change: Strategies for occupational and Physical Therapists. Baltimore, MD, Williams & Wilkins, 1986

14 Stevens J: Applied Multivariate Statistics for the Social Sciences. Hillsdale, NJ, Lawrence Erlbaum Associates Inc, 1986

15 Brown JV, Sepehr MM, Ettlinger G, et al: The accuracy of aimed movements to visual targets during development: The role of visual information. J Exp Child Psychol 41:443-460, 1986

16 Jeannerod M: The timing of natural prehension movements. journal of Motor Behavior 16:235-254, 1984

Table 4. Two-Way Analysis-of-Variance Results for Repeated Measures
(Treatment x Trial)
Source                           F[.sup.a]     p
Movement time (MU)
   Treatment                      12.18       <.025
   Trials                          0.62       NS
   Treatment x trials              0.21       NS
Reaction time
   Treatment                       0.34       NS
   Trials                          0.59       NS
   Treatment   x trials            1.15       NS
Associated reactions
   Treatment                       0.29       NS
   Trials                          1.13       NS
   Treatment   x trials            1.81       NS
Distance
   Treatment                       0.48       NS
   Trials                          0.85       NS
   Treatment   x trials            0.49       NS
Total MUs
   Treatment                       5.71       <.075
   Trials                          0.50       NS
   Treatment   x trials            0.02       NS
Ratio of 1 st MU/
   movement time
   Treatment                       17.71      <.025
   Trials                          0.26       NS
   Treatment x trials              1.61       NS
 (a) Treatment (df = 1,4); trials (df = 6,24).
Table 5. Comparative Movement Times of Children with Cerebral Palsy
(CP) and Healthy Infants and Young Children
                   Movement Time (msec)
                   _______________________
Subjects           [.bar.over]X      s
__________________________________________
Children with CP
  (7-12 yr)
  Pretreatment     1,216-5,000   267-1,266
  Posttreatment      879-4,054
Infants
  (5-9 mo) (12)      548-868     233-286
Children
  (1.5-8 yr) (15)    515-725     103-109

Appendix. Treatment Goals and Treatment Provided to Each Subject

Primary Goal: Improve the quality of reaching skills, including improved control, smoothness. and efficiency of reaching and improved ability to initiate reaching.

Specific Goals:

1.a. Decrease muscle tone in upper extremities.

b. Decrease muscle tone in lower extremities.

c. Decrease overflow of increased muscle tone with effort.

2.a. Increase scapulohumeral dissociation.

b. Increase range of motion in shoulders.

c. Increase ROM in elbows.

d. increase ROM in trunk.

e. Increase pelvic mobility and hip ROM.

3.a. Improve active shoulder flexor antigravity control.

b. improve active elbow extension.

c. Improve active wrist extension.

d. improve ability to reach to and across midline.

4.a. Improve active lengthening control of scapulohumeral muscles.

b. Improve ability to bear and shift weight on forearms.

c. Improve ability to bear and shift weight on extended arms.

5.a. Improve trunk lateral righting.

b. Improve trunk flexor control.

c. Improve active trunk rotation.

J Kluzik, MS, PT, is Therapy Department Coordinator, Cotting School, 453 Concord Ave, Lexington, MA 02173 (USA). She was a graduate student, Department of Physical Therapy, Sargent College of Allied Health Professions, Boston University, Boston, MA, when this study was completed in partial fulfillment of the requirements for her master's degree. Address all correspondence to Ms Kluzik.

L Fetters, PhD, PT, is Assistant Professor, Department of Physical Therapy, Sargent College of Allied Health Professions, Boston University, 1 University Rd, Boston, MA 02215.

J Coryell, PhD, PT, is Associate Professor, Department of Physical Therapy, Sargent College of Allied Health Professions, Boston University.

This study was partially supported by funds from the National Institutes of Health biomedical research grant awarded by Boston University to Dr Fetters and by funds from the Moriah Foundation.

The first and second authors contributed equally to the preparation of this manuscript.

This article was submitted February 28, 1989; was with the authors for revision for four weeks: and was accepted Septemer 21, 1989.

Commentary

Kluzik, Fetters, and Coryell are to be commended for their process-oriented approach to the study of movement control in children with cerebral palsy. Their article continues a growing shift away from attempts to document motor performance in these patients using traditional methods such as surveys of motor skill attainment. Instead, the authors attempt to identify and to quantify important features of reaching behavior, features that are more likely to shed light on the short-term effects of therapeutic intervention.

What is most encouraging about this work is not that the authors have used quantitative measures of reaching per se. Many studies of the gait patterns and other behaviors of this population have measured kinematic and electromyographic variables. Rather, the use of measures derived from theoretical work on basic processes underlying voluntary movement is of greatest significance. An example in this study is the movement unit (MU), which may reflect indirectly the stability of coordination of the joints of the upper extremity in approaching a target. The importance of measuring variables that derive from work on fundamental motor processes cannot be overemphasized, a point to which I will return shortly.

With respect to the data, the results show the importance of examining both group and single-subject data in studies of this kind when the number of subjects is small. Ironically, it is often in the latter case that one extreme score washes out a treatment effect, leading to an insignificant result. In the present study, on the other hand, the group analyses reveal significant treatment effects for the variables movement time (MT), number of MUs, and relative duration of the first MU . When one examines the individual data, however, the picture is not so clear . The authors, therefore, should be applauded for presenting the individual data as well.

Using Ottenbacher's criterion, (1) only Subject A exhibited a significant decrease in MT (although Subject C touched the toy after treatment, whereas she could not do so previously--an important improvement--the pretreatment and posttreatment MTs are not directly comparable), no subjects demonstrated a significant decrease in the number of MUs per reach, and only Subject A exhibited a significant increase in the relative time occupied by the first MU, although Subjects D and E exhibited strong trends in that direction. Moreover, trial-to-trial variability of the posttreatment measures does not, in general, appear smaller than before treatment. Decreased variability itself might be indicative of improved performance.

Despite this variability and the lack of clear individual effects (except for Subject A), significant differences in the group analyses suggest that something positive, albeit subtle, has resulted from the intervention. Expecting a more dramatic improvement in the reaching performance of this population following only one treatment is probably too much to ask in the first place. Future work should focus on the evaluation of long-term effects. Moreover, it will be important to determine whether treatment leads to an improvement in hand function as well; the ability to manipulate the object after transporting the limb to its spatial location has even greater functional significance. The use of control groups in future work is also imperative, as the authors have recognized. The present results might be more convincing if there were data showing that a matched control group exhibited none of the same trends in performance.

In general, the authors' conclusions seem reasonable and properly tempered. Their discussion about improvement in the hand's orientation to the target following treatment, however, is extremely speculative. The authors present no data that have a direct bearing on hand orientation. Moreover, although the reported change in acceleration profiles may be related to hand orientation in normal reaches, those reaches typically end with grasping the object. In the present experiment, grasping, and consequently hand orientation, was not part of the task requirement. No constraints on how the toy should be touched are apparent from the article. The long tail at the end of the acceleration profile in Figure 8 [omitted] may have resulted instead from the subjects' attempt to "fine-tune" the reach itself so as to hit the target.

Trends toward improved reaching behavior occurred along different dimensions of motor performance for different subjects. Many factors could account for this fact, including differences in the exact nature of the underlying lesion or slight differences in treatment emphasis, among others. Given the limited data set and length of treatment, it is unwise to make too much of this fact. Nonetheless, this finding does provide an opportunity to raise an important question, namely, When interested in measuring change in motor behavior, what are the most appropriate variables to measure? The answer will depend, at least in part, on the specific problem being studied (eg, postural control, walking, or reaching). But within any one context, there is a plethora of potential variables that could be measured. Which among the possibilities will maximize one's chances of finding a difference should one exist? Unfortunately, given our current state of understanding of motor-control processes, distinguishing between the motor system's essential and nonessential variables is a nontrivial problem. if the problem of interest in this population is abnormal coordination, as is often the case, the variables selected for measurement must reflect the processes underlying that coordination. Measuring variables that fail to meet this criterion will thus provide little likelihood of finding a significant effect. The upshot of this digression is that 1) researchers must look to process-oriented theories of motor control that are closely tied to experimentation for clues to identifying the essential variables, and 2) at this point in time, experimental work to discover the motor system's essential variables and studies directed toward documentating therapeutic effectiveness are equally important for the advancement of our profession. Without the appropriate variables, the latter endeavor will be fruitless.

The present study appears to have been carried out in this spirit. Whether the authors have found the most appropriate measures remains an open question. Certainly, the MU has a firm grounding in recent theoretical approaches to reaching behavior. It is less likely that MT is an essential variable if one's interest is in the coordination of reaching, although it may be useful in other contexts. For example, while an increased speed of reaching may have functional significance, it would be of limited value if not achieved in a controlled manner.

A number of other variables that derive from theoretical models of motor control may have value in this context. For example, mean squared jerk (the third derivative of displacement) has shown promise as a means of quantifying the smoothness of a reaching trajectory and has been considered theoretically as a variational principle underlying the motor control of reaching. (2) One might also attempt to quantify directly the coordination of the upper extremity joints in reaching, (3) providing a means for evaluating the effect of treatment on this coordination. The stability of reaching patterns might also be obtained with the appropriate measures. (4) Improved pattern stability should be expected if therapy is effective. Despite the wider possibilities, however, Kluzik et al have taken an important step in the right direction.

John P Scholz, PhD, PT

Assistant Professor

Program in Physical Therapy School of Life and Health Sciences

University of Delaware

009 McKinly Laboratory

Newark, DE 19716

References

1 Ottenbacher KJ: Evaluating Clinical Change: Strategies for Occupational and Physical Therapists. Baltimore, MD, Williams & Wilkins, 1986

2 Hogan N, Flash T: Moving gracefully: Quantitative theories of motor coordination. Trends in Neuroscience 10:170-174, 1987

3 Soechting JF, Lacquaniti F: Invariant characteristics of a pointing movement in man. J Neurosci 1:710-720, 1981

4 Scholz JP, Kelso JAS: A quantitative approach to understanding the formation and change of coordinated movement patterns. journal of Motor Behavior 21:122-144, 1989

Author Response

Our sincere thanks to Dr Scholz for his elegant commentary. We would like to reiterate his emphasis on the importance of both theoretical and clinical research for the advancement of knowledge regarding the neuromuscular system and the advancement of physical therapy. As Scholz points out, meaningful clinical research must stem from a conceptual or theoretical basis if it is to truly guide us in understanding the complexities of the motor system. The myriad of possible variables to study may be overwhelming unless we are conceptually guided toward the essential variables. We should be long past the debate as to whether theoretical or clinical research is the most valuable. Clinical research must be guided and shaped from theoretical work in the same way that clinical practice should be guided and shaped by clinical research.

The effects of neurodevelopmental therapy (NDT) have been "hotly" debated. To date, the research literature has not been supportive of NDT for children with cerebral palsy. Positive results have been modest, if demonstrated at all. (1-3) There are at least two ways of interpreting this literature. The first is that it is accurate and NDT is not very effective in making change. As difficult as this interpretation may be to accept, we must at least entertain the possibility. However, an additional possibility is that previous research has not utilized the best method or the most important variables for study. Our line of research was undertaken because we embrace the latter opinion. Our continued process-oriented approach will build on this pilot study. We are adding two additional treatment types in our current study, and we are lengthening the time of treatment. Scholz suggests that a matched control group would make the results more compelling. We agree. We did, in fact, test an age-matched control group, but we did not include those data in this article. Kinematic data on infants (4,5) and adults (for examples, see the articles by Fisk and Goodale (6) and Jeannerod (7) and the references cited by Scholz) are available, but we found no data on the pre-adolescent group. Our five age-matched controls had kinematic data that were comparable to those of adults. The control group children used a single movement unit and had movement times that were as fast as those of adults, with minimal variation. As a consequence, we believed that measuring change after an hour (the time interval between pretreatment and posttreatment measurement) would have been meaningless.

Two additional classes of variables may assist us in understanding movement and the changes in movement following treatment: 1) muscle pattern activation and 2) changes in pattern of activation in patients with movement dysfunction before and after intervention and postural set changes. These variables will be investigated in future work. We hope that step by step we will be able to sort out the important variables of change in the neuromuscular system following physical therapy, realizing, as Dr Scholz highlights, that this is a nontrivial problem.

JoAnn Kluzik

Linda Fetters

Jane Coryell

References

1 Ottenbacher KJ, Biocca Z, DeCremer G, et al: Quantitative analysis of the effectiveness of pediatric therapy: Emphasis on the neurodevelopmental treatment approach. Phys Ther 66:1095-1101, 1986

2 Parette HP, Hourcade JJ: A review of therapeutic intervention research on gross and fine motor progress in young children with cerebral palsy. Am J Occup Ther 38:462-468, 1984

3 Palmer FB, Shapiro BK, Wachtel RC, et al: The effects of physical therapy on cerebral palsy. N Engl J Med 318:803-808, 1988

4 von Hofsten C: Development of visually directed reaching: The approach phase. journal of Human Movement Studies 5:160-178, 1979

5 Fetters L, Todd J: Quantitative assessment of infant reaching movements. journal of Motor Behavior 19:147-166, 1987

6 Fisk JD, Goodale NIA: The organization of eye and limb movements during unrestricted reaching to targets in contralateral and ipsilateral visual space. Exp Brain Res 60:159-178, 1985

7 Jeannerod M: The timing of natural prehension movements. journal of Motor Behavior 16:235-254, 1984