Jul 20, 1987 - increasing the rate of skill acqu6ition during a novel motor task. ... is a consultant, ladd Center, School Land Rd, Exeter, RI 02852, and Trudeau.
Effects of Mental Practice on Rate of Skill Acquisition
7i3epurpose of this study was to investgate the effectiveness of mental practice in increasing the rate of skill acqu6ition during a novel motor task. Twenty-sixsubjects were random& assgned to two groups The Control Group (n = 13)performed only p@sicul practice; the Eqerimmal Group (n = 13)p@ormed both mental and pbysicul practice. The task was to toss, by flexing the elbow, a PingPong ball held in a cup on a forearm splint to a target. 7i3e biceps bracbii muscle and the long and lateral head of the mcqs brachii muscle were monitored electromyographically to determine any changes occum'ng during skill acquisition. The Experimental Group S accuracy improved at a sign@cantlygreater rate than that of the Conlrol Group. In addition, the E3cperimerual Group demonsh-ated changes in timing z)uriablesthat led to a more eficient movement. 7i3e.e changes included a decrease in timepom the onset of muscle activity t o p e d activity and an increase in the time e l a p e d m the onset of agonist contraction to the onset of antagonist contraction. These results suggest that mental practice may be a n important tool in facilitating the acqutkition of a new motor skill. [MaringJK: Effects of mentalpractice on rate of skill acqubition. Pbys Ther 70:165-172, 19901
Joyce R Maring
Key Words: Electromyograpby, Mentalalpresses, Motor skills, Movement.
Physical therapists and occupational therapists play a major role in teaching their patients new motor skills. In most cases, it is physiologically, emotionally, and economically advantageous for the patient to acquire the skill as rapidly as possible. Mental practice may be an important clinical tool in assisting patients to rapidly learn a motor task.In addition, when fatigue makes physical repetition of a motor ask undesirable, mental practice may be an effective aid to mastery of a slull without the expenditure of significant energy.
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The facilitating effect of mental practice on slull acquisition has been well documented.'-5 Changes have been shown to take place on electromyographical recordings as a result of physical practice."'G No previous research can be found, however, to document whether the use of mental practice can accelerate the EMG changes found following physical practice. Schmidt indicated that mental practice is an area of research with many unanswered questions but with practical applications.17
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J Maring, MSPT, is a consultant, ladd Center, School Land Rd, Exeter, RI 02852, and Trudeau Memorial Center, Post Rd, Warwick, RI 02886. She was a student in the hlaster of Science in Physical Therapy Program, Department of Physical Therapy, Sargent College of Allied Health Professions, Boston Universiry, Boston, MA, when this study was completed in partial fulfillment of the requiremena for her master's degree. Address correspondence to Ms Maring at 17 Old Pine Rd, Narragansett, RI 02882 (LISA). 7b6 arlicle urn sz~hmit!edJuly 20, 1987; way u ~ f the h author for ra~istonfor 78 uleeh; and ulas accepted Oclober 23, 1989.
2 8 / 165
Most therapists tend to emphasize the role of peripheral sensory input while teaching their patients new slalls. This tendency is especially true with patients who have a developmental disability or brain injury. The ultimate goal is often an "automatic" correction of the movement via peripheral sensory input.18 Brunnstrom has stated that for the execution of voluntary movements, the entire sensory pathway from the periphery to the cortex must be funaioning.19 A deafferentation study performed on animals20 and the study of ballistic movement in humans,21 however, seem to indicate that much movement may be preprogrammed by the central nervous system. Granit has urged scientists to stop polarizing discussions of motor control around two mutually exclusive alternatives.22 In reality, central and peripheral mechanisms must be closely intertwined and operate
Physical TherapyNolume 70, Number 3/March 1990
together for smooth, skilled movements. Therapists must also consider treatment approaches that utilize more of the tenets associated with central control. Mental practice may be an important central to01 for accelerating gross motor learning. Athletes have been aware of the benefits of mental practice for some time.23 Rawlings et a1 demonstrated that mental practice o r covert rehearsal increases the speed and retention of skill acquisiti0n.l Fansler et a1 found that mental practice enhanced unilateral balance in elderly women.2-'Granit suggested that conscious awareness plays a role in stamping in engrams, serving as an activator capable of selecting cells and circuits and keeping them in focus to the exclusion of others via the use of both excitation and inhibition22 Richardson refers to mental practice as the symbolic rehearsal of a physical activity without gross muscular movement.3 Exactly what the subject does during "mental practice" unfortunately has not been clearly defined. Jones believes that the most essential element of mental practice is the formation of a kinesthetic image; the subject must be able to conjure up what it feels like to perform a rn0vement.~5Once an attempt of the movement has been made, proprioceptive feedback enhances the chance of completing the image. Some controversy exists in the literature rega.rding the effect of physical practice on muscle activity. There is little agreement as to whether the electrical activity of the agonist and antagonist increases or decreases, as determined by analysis of integrated electromyographic data following physical practice.7-16q26DBerences in the amount of electrical activity may be a function of uncontrolled variables rather than a result of practice. For instance, it has been documented that an increase in velocity of movement is associated with an increase in
EMG acti~ity.~7 Although many studies mention changes in velocity, there was no attempt to correlate these changes with the changes in electrical activity. The differences in electrical activity recorded also likely depend on which muscles are being examined. The results of a study by Lamb et a1 indicate that a difference may exist between the changes in electrical activity of the prime movers versus accessory muscles as a result of practice.12
learning a new task, as demonstrated in the physical practice studies, would appear more quickly in an individual incorporating the use of mental practice. These changes would include a selective inhibition of unnecessary muscular activity, resulting in a reciprocal relationship of the agonist and antagonist as described by Person,l4 and timing features indicative of central programming or motoneuron recruitment.
Method Several authors do agree on the effect that practice has on the activity of agonists and antagonists. Basmajian and Blumenstein summarized this relationship well when they stated that there is a selective inhibition of unnecessary muscular activity.28 If the EMG recording demonstrated a lot of antagonist movement, they determined it to be a signal of either abnormality or ineptitude. Hobart described an increase in the antagonist burst at the end of the movement to slow down the moving part at the end point.1° During most of the movement, the antagonist was silent. Person, in describing the EMG reading, observed a concentration of excitation and rest periods following practice of a chiseling task and a reciprocal relationship of the agonist and antagonist that was not observed before practice.l4 Fisher and Merhautova observed a gradual increase in electrical activity during the entire movement of untrained subjects, whereas trained subjects demonstrated bursts at the "proper" m~ments.~ The purpose of this study was to investigate the effect of mental practice on skill acquisition during a novel motor task. Electromyography was used to provide evidence of the changes that occur in muscle activity secondary to the learning of a novel task. I hypothesized that mental practice could accelerate the acquisition of a new motor skill. I also proposed that the EMG changes associated with
'Parker Brothers, 50 Dunharn Rd, Beverly, MA 01915
Physical 'TherapyNolume 70, Number 3/March 1990
Subjects
The subjects in this study (N = 26) were selected on a volunteer basis from the students of Sargent College of Allied Health Professions at Boston University, the students of the University of Rhode Island, and the employees of the Ladd Center in Rhode Island. The subjects, whose ages ranged from 22 to 40 years (X = 30 years), were randomly divided into two groups. The Experimental Group (10 women, 3 men; X age = 31 years) performed a task involving a combination of mental practice and physical practice to determine the effect of the addition of mental practice on motor skill acquisition. The Control Group (1 1 women, 2 men; X age = 29 years) performed the task using physical practice only for the purpose of comparison. All subjects were free of known neuromuscular disease processes. Informed consent was obtained from all subjects, and the study protocol was approved by Boston University's Human Research Review Board. Procedure
In order for learning to occur and be measurable, the subject must be unfamiliar with the movement task to be performed. The task selected was to throw a Ping-Pong ball* by flexing the elbow from a position of extension. The elbow was positioned in extension on a forearm splint. The ball was thrown to a horizontally placed target located 1.5 m in front of the subject. The subjects were seated in an armless, straight-backed chair. The fore-
arm was in the neutral position, thumb facing anteriorly (Fig. 1). The Ping-Pong balls were covered with strips of Velcromhooktape,+and the target was constructed from a Velcro@-adherentmaterial. Beckman miniature silversilver-chloride electrode$ were placed on the belly of the biceps brachii muscle and the long and lateral heads of the triceps brachii muscle of the nondominant arm. The position of the electrodes was verified by palpation during manual muscle testing and by comparison to Basmajian and Blumenstein's anatomical drawings.28 A ground ear-clip electrode was applied to the ipsilateral ear. The medial head of the triceps brachii muscle was not monitored because evidence suggests its output is unchanged with learning.5 The biceps brachii muscle was selected as the prime mover of the task requiring elbow flexion. Bouisset et a1 found that in a variety of elbow flexion tasks, during which the elbow flexors were monitored, the onset of EMG activity appeared first and generally was greatest in the biceps brachii muscle.29 The EMG activity of the other flexor muscles demonstrated a linear relationship to the biceps brachii muscle, regardless of velocity of movement and inertia. The selected electrode sites were prepared by cleansing the area with alcohol, abrading the skin with Omni~ r e p , b n dforcing a conductive medium into the slun with a stiff brush. Adequate skin resistance was verified with a Grass impedance meterll and ranged from 2 to 8 kR with a mean of 4 kR. The electrical output was processed by three 7P3 AC preamplifiers and three 7P10 cumulative integrators of a Grass Model 7 polygraph. I' The
Fig. 1. Subject executing ball toss zoithfoream splint. preamplifiers were calibrated with a 0.5-A frequency range of 3 to 75 Hz and the cumulative integrators with a 0.5-A frequency range of 3 to 40 kHz. The sensitivity was adjusted to 200 @/2 cm peak to peak. The paper speed was 100 mm/sec. The movement was tracked with an electrogoniometer mounted on the lateral aspect of the subject's arm, with the axis of motion at the elbow joint. This movement was recorded using a 7P1 DC preamplifier over a linearly calibrated range. Each subject first performed maximal voluntary contractions (MVCs) of the biceps brachii and triceps brachii muscles in the midrange position using manual resistance to obtain baseline data, thereby reducing intersubject variability. Next, members of the Control Group were given a task that demanded their mental attention. They were given a poem, which they were instructed to memorize for two minutes.30 They were then asked to toss the Ping-Pong ball to the target
'Velcro USA Inc, PO Box 5218, 406 Brown A V ~Manchester, , NH 03108. *Beckman lnstrumenn Inc, 3900 River Rd, Shiller Park, IL 60176.
% 0 Weaver & Co, 565-C Nucla Way, Aurora, CO 80C)ll. ' I ~ r a s sInstrument Co,101 Old Colony Ave, PO Box 516, Quincy, MA 02169
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using elbow flexion. They repeated the toss 10 times. Each subject was again distracted for two minutes and the trials repeated. Five repetitions of this sequence were performed. Members of the Experimental Group followed the same procedure for all five repetitions except that during the two-minute period that the Control Group was distracted, the Experimental Group was told to visualize the movement mentally. Cues were given, such as "Look at the target. I want you to visualize your arm moving the ball to the target. Feel this movement in your mind; picture it." During this period of mental practice, the subject was not allowed to physically move the arm.
Data Acquisition The accuracy of the ball toss was assessed for all 50 tosses of each subject. The distance (in centimeters) from the midpoint of the ball to the center of the target was measured for each toss. The total electrical activity was also calculated for all subiecrs from the three sets of electrodes for trials 1 to 3, 8 to 10, 18 to 20, 28 to 30, 38 to 40, and 48 to 50. The sample analyzed was from onset of movement to ball
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Table 1. Means and Standard Deviations of Slopes for Dependent Variables Control Group (n = 13)
Variable
X
Accuracya
-0.31
TI-biceps brachii muscleb
-2.1 x
TI-lateral head of triceps brachii muscleb
1x
TI -long head of triceps brachii muscleb
1x
T2-ateral head of triceps brachii muscleC
2x
T2-long head of triceps brachii muscleC
Experimental Group (n = 13) X s
s
5x
0.26
lo-4 lo-4 lo-4 lo-4 lo-3
9.6 x 16 x 14 x 11 x 15 x
-0.43
lo-4 lo-4 lo-4 lo-4 lo-3
-7 x -12 x -10 x 19 x 2x
0.24
lo-4 lo-4 lo-4 lo-4 lo-3
18 x 8x 13 x 1.6 x
Biceps brachii muscled
0.03
0.21
0.04
0.22
Lateral head of triceps brachii muscled
0.01
0.21
0.03
0.22
0.27
0.27
0.28
Long head of triceps brachii muscled
-0.15
lo-4
11 x 1 0 - ~
lo-4 lo-3
"Measured in centimeters per trial. b ~ n s eof t rnuscle activity to peak activity measured in seconds per trial. 'Onset of agonist to onset of antagonist measured in seconds per trial. d ~ o t aintegrated l electromyographic activity expressed as percentage of maximal voluntary contraction per trial
release, as determined by the deviation of the electrogoniometer from the baseline to the furthest point of flexion and as verified with a signal marker. 'fie data were normalized for time and intervening variables by. expressirlg the electrical output of each electrode of each subject as a percentage of the MVC. Timing features were also believed to be impo~tantbecause they were valuindications in changing of motor recruitment and the relationship of the agonist and antagonist. The first timing feature measured was the time elapsed from the onset of muscle activity to the peak of motor recruitment f i r all three sets of electrodes. The second timing feature measured was the time elapsed between the onset of the biceps brachii muscle (agonist) activity to the onset of the triceps brachii muscle (antagonist) activity. All timing features were measured for each of the six series of trials cited previously. Data Analysis The primary research question was whether mental practice can accelerate the rate of motor slull acquisition. A linear regression appeared to be an
appropriate model for this data. The correlation coefficients of the linear regressions of the dependent variables versus trials were either greater than or not significantly different from those derived via another functional form (eg, exponential, logarithmic, polynomial). In addition, scatter plots of the residuals of the linear regres-
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sions of individual subject data showed no systematic pattern, as would have been evident if the data were better modeled by another functional form. The slope of the linear regressions of the dependent variables versus trials, therefore, should be indicative of the rate of skill acquisition.
Table 2. Results of r Test for slopes of Dependent Varhbles of Control Croup
(n
=
13)
Varlable
t
df
7
Accuracy TI-biceps brachii muscleb TI -lateral head of triceps brachii muscleb TI-long head of triceps brachii muscleb T2-lateral head of triceps brachii muscleC T2-long head of triceps brachii muscleC Biceps brachii muscled Lateral head of triceps brachii muscled Long head of triceps brachii muscled
"Probability that slope is not different from zero. b ~ n s eof t muscle activity to peak activity per trial. 'Onset of agonist to onset of antagonist per trial "Total integrated electromyographic activity expressed as percentage of maximal voluntary contraction per trial.
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168/31
The slopes of the linear regressions and their associated standard errors were determined for each dependent variable versus trials, individually and then by group. Student's t tests were performed to determine whether the slopes of the individuals and then groups differed significantly from zero. Student's t tests were also performed to determine whether the slopes, and therefore the rate of sktll acquisition, differed significantly between the Control and Experimental Groups.
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Table 3. Results of
t Testfor Slopes of Dependent Variables of Eqerimental Group
(n = 13)
Variable
P'
df
t
Accuracy T1-biceps brachii muscleb T1-lateral head of triceps brachii muscleb T1-long head of triceps brachii muscleb T2-lateral head of triceps brachii musclec T2-long head of triceps brachii musclec Biceps brachii muscled
Results Because of technical problems or artifacts, we could not include all EMG data of all subjects in the data analysis. One subject of the Experimental Group had very high electrode impedance as measured by the impedance meter (greater than 20 kfl), despite three attempts to reduce resistance via skin preparation. Therefore, too much artifact was present to reliably reduce the data. One subject in each group had high electrode impedance in the lateral triceps brachii muscle's electrodes, and one subject of the Control Group had significant cable artifact in the EMG tracings of the long head of the triceps brachii muscle, probably attributable to brushing against the upp"er body during the tossing motion. The mean slopes and standard errors for both groups for all the variables tested are reported in Table 1. Tables 2 and 3 summarize the results of the t tests for the slopes of all the dependent variables for the groups separately to determine whether the performance of the group as a whole changed significantly on the variable being tested. Table 4 summarizes the results of the t tests for the group comparisons of the slopes of the variables tested to determine whether the groups differed significantly from each other in the rate of skill acquisition or change.
Lateral head of triceps brachii muscled Long head of triceps brachii muscled
"Probability that slope is not different from zero. 'Onset of muscle activity to peak activity per trial. 'Onset of agonist to onset of antagonist per trial. d ~ o t aintegrated l electromyographic activity expressed as percentage of maximal voluntary contraction per trial.
changes over the series of trials, which differed from those of the Control Group. Although both groups demonstrated an increase in accuracy, the Experimental Group's accuracy improved at a faster rate
40 Control n
E
0
30.
w
>
0 4 [r
20.
3
0 0
10.
*
1 I
10
Discussion
The Experimental Group demonstrated numerous significant
than that of the Control Group (Tab. 1, Fig. 2). This difference in skill acquisition was significant at the 95% confidence level (Tab. 4). A review of the data also revealed that 10 Experimental Group subjects
20
1
I
I
1
I
40
50
30
1
TRIAL Fig. 2.
Group mean linear regressions of ball toss accuracy uerszrs nial.
Physical TherapyNolume 70, Number 3IMarch 1990
showed significant improvement, whereas only 5 Control Group subjects demonstrated progress that differed significantly from zero. This finding w&ld appear to indicate that mental practice is indeed effective in increasing the rate of skill acquisition during a novel motor task. Several of the timing variables also revealed differences between the two groups. When the group results were examined separately, none of the timing features of the Control Group showed significant changes, whereas all of the timing variables of the Experimental Group with the exception of onset of muscle activity to peak activity of the biceps brachii muscle demonstrated signficant changes ([Tabs.2, 3). The Experimental Group's peak of antagonist muscle contraction occurred earlier and the antagonist also commenced firing later in the range of motion over the course of the trials, as compared with the Control Group. When the slopes of the two groups are compared with each other for timing variables, significant differences again become evident (Tab. 4). The rate of change for the time of initiation of muscle activity to peak activity was significantly different for both antagonists. The time that elapsed from the initiation of agonist activity to the initiation of antagonist activity increasecl for the Experimental Group at least for the lateral head of the triceps brachii muscle. The long head of the triceps brachii muscle also showed activity later in the ROM, but this finding was only significant at the 75th percentile. The changes in timing variables that occurrecl over the series of trials in the Experimental Group is consistent with the change in the agonistantagonist relationship described by ,~ Fisher and M e r h a u t o ~ aPerson,14 and Basrnajianzhs a result of physical practice. Bursts occur at the "proper ntoments," rather than gradually increasing during the movement.R Fbbartlo described, the antagonist burst increased at the
Table 4. Results of t Testfor Compankon of Control (n (n
=
=
13) and hperimentaf
13) Groups
Accuracy TI -biceps brachii muscleb 1-1-lateral head of triceps brachii muscleb TI -long head of triceps brachii muscleb T2-lateral head of triceps brachii muscleC T2-long head of triceps brachii muscleC Biceps brachii muscled Lateral head of triceps brachii muscled Long head of triceps brachii muscled "Probability that slopes of Control Group and Experimental Group are not different From each other. 'onset of muscle activity to peak activity per trial. 'Onset of agonist to onset of antagonist per trial *~otalintegrated electromyographic activity expressed as percentage of maximal voluntary contraction per trial.
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end of the movement to slow down the moving part at the end point; during most of the movement, the antagonist was silent (Figs. 3-5).
These changes may indicate that the movement was being programmed at a more central level in the Experimental Group than in the Control
I
Control Group
I
Experimental Group
TRIAL Fig. 3. Group mean linear regresions of timejFom movement onset to peak motjement (TI) of lateral bead of triceps brachii m d e i~ersusrial.
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Group. The concentration of excitation and rest periods is typical of movements believed to be preprogrammed by the CNS.21Although some researchers were able to report these changes as a result of physical practice, the 50 trials used in this experiment appeared insufficient to observe these changes in the Control Group. The Experimental Group, however, did demonstrate this changed relationship at a significant level, indicating that mental practice in conjunction with physical practice may be an important tool in improving the coordination and efficiency of a new motor task at a much faster rate than the use of physical practice alone. Changes in the total IEMG for the three sets of electrodes occurred at a significant level for the long head of the triceps brachii muscle only. These changes were consistent with Hobart's description of an overall increase in the electrical activity of the antagonist.I0 It is not clear why no systematic changes occurred in the other muscle groups recorded. Perhaps the number of trials was insufficient to observe a significant change. The subjects demonstrated great variation in elbow ROM used to toss the ball. The Control Group's ROM was 8 to 75 degrees, with an average excursion of 42.5 degrees. The Experimental Group's ROM was 15 to 80 degrees, with an average excursion of 44 degrees. Therefore, the ROM was not significantly different between the groups and probably did not contribute to the differences between groups. The elbow ROM of each subject also did not significantly change during the six trial sequences, indicating that the individual used the same tossing strategy throughout the trials. Because all subjects in this study were free from known neuromuscular involvement, the application of these results to patients whose physical dysfunction is related to a neuromuscular disorder cannot be ascertained at this time. In addition, mental practice as a therapeutic tool would appear to
-. Control Group
--
--Experimental
20
30
TRIAL Fig. 4. Group mean linear regressions of time from movement onset to peak movement ( T I ) of long head of triceps brachii muscie verszrs m i .
Experimental
.06
Fig. 5. Group mean linear regressions of time from onset of biceps brachii muscle (agonist) to onset of lateral bead of triceps brachii muscle (antagonist) (TZ) versus n-idl. require that the individual using it be capable of the cognitive processes necessary to form a kinesthetic image and rehearse that image.
Despite these limitations, the results of this study suggest that mental practice in addition to physical practice may be an extremely effective tool in assisting a patient to rapidly learn a
Physical TherapyNolume 70, Number YMarch 1990
new motor task. Mental practice is a technique that can be readily adapted by therapists for their patients because it requires no special facilities or equipment. Mental practice has the potential to reduce both the fatigue and the costs involved in conventional programs of physical recovery. Warner and McNeill concluded that mental imagery can be the beginning of a more inclusive treatment program involving cognitive, affective, and physical modes of expression.31
Conclusions The findings of this study showed that the subjem who used mental practice in conjunction with physical practice increased their accuracy for the task at a significantly faster rate than the subjects who used physical practice alone. In addition, the Experimental Group demonstrated changes in timing variables that led to a more eficient movement. These changes included a decrease in time from the onset of muscle activity to peak activity and an increase in the time elapsed from the onset of agonist contraction to the onset of antagonist contraction. These timing changes did not occur at a significant level for the Control Group. Overall, the total electrical activity changes were not significant for either group. More research is warranted to explore the application of mental practice as a treatment modality. Applicability to individuals with neuromuscular dyshnction should be investigated. Mental practice, however, may be an important therapeutic tool to encourage rapid acquisition of a new skill. Acknowledgments
and Leslie Portney, faculty members at Boston University's Sargent College of Allied Health Professions, for their suggestions and constructive criticisms; and Hal Maring, a member of the research staff at the University of Rhocle Island, for his assistance with the statistical analyses. References 1 Rawlings F1, Rawlings IL, Chen CS, et al: The facilitating effects of mental rehearsal in the acquisition of rotary pursuit tracking. Psychonomic Science 26:71-73, 1972 2 Richardson A: Mental practice: A review and discussion (Part 1). Research Quarterly 3 8 : 9 5 107, 1967 3 Richardson A: Mental practice: A review and discussion (Pan 2). Research Quarterly 3 8 2 6 5 273, 1967 4 Singer RN: Cognitive processes: Learner strategies of skilled motor behaviors. Can J Sports Sci 5325-32, 1980 5 Denis M: Visual imagery and the use of mental practice in the development of motor skills. Can J Sport Sci 10:416, 1985 6 Burns LB: Effects of Mental Practice o n the Acquisition of Skill in a Novel Motor Task. Master's Thesis. Boston, MA, Boston University, 1978 7 Finley FR, Wina RW, Cody KA: Muscle synergies in motor performance. Arch Phys Med Rehabil 49:655660, 1968 8 Fisher A, Merhautova J: Electromyographic manifestations of individual stages of adapted sports technique. In: Health and Fitness in the Modern World. Chicago, IL, Athletic Institute and American Collection of Sports Medicine, 1961, vol 13, pp 13G147 9 Herrnan R: Electromyographic evidence of some control factors involved in acquisition of skilled performance. Am J Phys Med 49:177191, 1970 10 Hobart DJ: Modifications occurring during acquisition of a novel throwing task. Am J Phys Med 54:l-24, 1975 11 Karnon E, Gormley J: Muscular aaivity pattern for skilled performance during learning of a horizontal bar exercise. Ergonomics 11:345-457, 1968 12 Lamb RL, Gross LD, Meydrech EF: Electrical and mechanical correlates of motor skill development: Triceps and anconeus as antagonists. In: Proceedings of the Seventh International Congress of the World Confederation for Physical Therapy, Montreal, Quebec, Canada, June 1974, pp 12G131
I thank the subjects for their participation in this study; Catherine Trombly
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13 Payton OD, Kelley DL: Electromyographic evidence of the acquisition of a motor skill: A pilot study. Phys Ther 52.261-266, 1972 14 Person RS: An electromyographic investigation o n coordination of the activity of antagonist muscles in man during the development of a motor habit. Journal of Higher Newous Activity 8 : 1 5 2 3 , 1958 15 Vorro J, Hobart D: Kinematic and myoelectric analvsis of skill acauisition: I. 90-cm subject gro"p. Arch Phys ~ e ~ehabil62:565574, d 1981 16 Vorro J, Hobart D: Kinematic and myoelectric analysis of skill acquisition: 11. 150-cm subject group. Arch Phys Med Rehabil 62:575582, 1981 17 Schmidt RA: Motor Control and Learning: A Behavioral Emphasis. Champaign, IL, Human Kinetics Publishers Inc, 1982, pp 12S335 18 O'Connell AL, Gardner EB: [Jnderstanding Scientific Basis of Human Movement. Baltimore, MD, Williams & Wilkins, 1972 19 Brunnstriim S: Movement Therapy in Hemiplegia. New York, NY, Harper & Row, Publishers Inc, 1970 20 Polit A, Bizzi E: Processes controlling arm movements in monkeys. Science 201:1235 1237, 1978 21 Brooks VB: Some examples of programmed limb movements. Brain Res 71:29S 308, 1974 22 Granit R: The Purposive Brain. Cambridge, MA, The MIT Press, 1977, pp 71-84, 191-212 23 Kane JE: Cognitive aspects of performance. Br J Sports Med 12:201-207, 1979 24 Fansler CL, Poff CL, Shepard KF: Effects of mental practice o n balance in elderly women. Phys Ther 65:1332-1338, 1985 25 Jones JG: Motor learning without demonstration of physical practice under two conditions of mental practice. Research Quarterly 36:27@-276, 1965 26 Basmajian JV: Motor learning and control: A working hypothesis. Arch Phys Med Rehabil 58:38411, 1977 27 Bigland B, Lippold OCJ: The relationship between force, velocity, and integrated electrical aaivity in human muscles. J Physiol (Lond) 123:21&224, 1954 28 BasmajianJV, Blumenstein R: Electrode Placement in Electromyographic Biofeedback. London, England, Williams & Wilkins, 1982 29 Bouisset S, Lestienne F, Maton H: The stability of synergy in agonists during the execution of a simple voluntary movement. Electroencephalogr Clin Neurophysiol 42:54+551, 1977 30 Cardinali N:Mental Practice for Accelerating Motor Learning. Master's Thesis. Boston, MA, Boston University, 1972 31 Warner L, blcNeill ME: Mental imagery and its potential for physical therapy. Phys Ther 68:516521, 1988
