Immediate response of glenohumeral abduction range of motion to a caudally directed translational mobilization: a fresh cadaver simulation

OBJECTIVE: To investigate the immediate effect of caudal glide translational mobilization on the range of motion (ROM) of passive glenohumeral abduction with a fresh cadaver model to simulate the mobilization movement performed by a physical therapist treating patients with glenohumeral hypomobility. DESIGN: Mechanical simulation of caudal glide mobilization and abduction torque range of motion (TROM) measurement of the glenohumeral joint with 2 material testing systems. Mobilizations were conducted with the glenohumeral joint positioned at a resting position (IGR) and at the end range of abduction (IGE). SETTING: Biomechanics laboratory. CADAVERS: Twenty fresh shoulder specimens from 10 cadavers (mean age, 68 +/- 8 yr). MAIN OUTCOME MEASURE: Changes in TROM of the glenohumeral abduction in response to 5 bouts of caudal glide mobilization. RESULTS: At least 3 repetitions of TROM were required to attain consistent measurements on glenohumeral abduction ROM. Significant differences were found among changes in TROM because of rest, IGR, and IGE (Kruskal-Wallis statistics, (chi2 = 14.58, p = .001). A greater increase in glenohumeral abduction TROM was found after IGE (mean +/- standard error of the mean, 4.38 degrees +/- 0.95 degrees) compared with the rest control (0.03 degrees +/- 0.07 degrees; Mann-Whitney test, p = .001, alpha = .017) or its IGR counterpart (0.26 degrees +/- 0.46 degrees, p = .001, alpha = .017). CONCLUSION: This simulation of caudal glide translational mobilization at the end range using cadaver models improved passive glenohumeral abduction ROM but was ineffective when performed with the shoulder placed in a resting position. The mechanical responses of the glenohumeral joint to translational mobilization in a live patient may be similar, but some caution should be used in generalizing these findings.     

Forces applied during manual therapy to patients with low back pain

BACKGROUND: To date, there is little information available regarding the forces used during mobilization treatment of patients with low back pain (LBP). OBJECTIVE: This study measured such forces and investigated whether the force characteristics could be predicted on the basis of physical therapist and patient characteristics. SUBJECTS: Ten physical therapists applied a central posteroanterior (PA) mobilization treatment to 80 patients with LBP, providing data on treatment of 123 lumbar levels. METHODS: Physical therapists were required to treat their patients while the patients lay on an instrumented couch. This couch has been shown to be highly accurate in its measurement of force in 3 directions (error <2%) and has demonstrated high test-retest reliability (ICC [2, 1], 99% CI = 0.99-1.00). The forces applied by the physical therapists were recorded over a 10-second period. Data on the characteristics of the physical therapists and patients were collected by means of questionnaires. RESULTS: The force used by physical therapists related not only to patient characteristics but also to physical therapist characteristics. Interestingly, current pain intensity and nature of symptoms did not affect the forces used. The overall patterns of the force characteristics were generally consistent with previous studies performed in asymptomatic subjects. However, the magnitude of the force applied and the frequency of each grade used in the present study are relatively higher than in earlier studies. CONCLUSION: These preliminary data provide some useful quantitative information about the forces used during mobilization treatment of patients with LBP. Also, the force characteristics described here may provide useful data for both teaching and research in manual therapy.     

Reliability of stiffness measured in glenohumeral joint and its application to assess the effect of end-range mobilization in subjects with adhesive capsulitis

End-range mobilization techniques are recommended for the treatment of patients with hypomobile joints. The purposes of this study were (1) to assess the reliability of a glenohumeral (GH) stiffness measurement technique and (2) apply the measurement technique on subjects with adhesive capsulitis to compare the GH end-range stiffness and rotational range of motions (ROMs) before and immediately after the application of end-range translational mobilization techniques. Fifteen normal subjects were recruited for assessment of test–retest reliability. Four men and two women with adhesive capsulitis in the glenohumeral joint (mean disease duration=6.5 months, SD=2.7) were treated with end-range mobilization by an experienced physical therapist. The passive abduction angles, rotational ROM and GH joint stiffness were measured by the same observer before and immediately after end-range mobilization treatment. The test–retest reliability was assessed and revealed good to excellent reliability in anterior–posterior glenohumeral joint stiffness and fair to excellent reliability of GH stiffness in posterior–anterior direction. The GH joint stiffness decreased and passive abduction range of motion increased immediately after end-range mobilization of the shoulder joint. The use of intensive mobilization techniques may help to decrease the risk of further stiffness or joint contracture progression in patients with adhesive capsulitis.     

Changes in abduction and rotation range of motion in response to simulated dorsal and ventral translational mobilization of the glenohumeral joint

BACKGROUND AND PURPOSE: Translational mobilization techniques are frequently used by physical therapists as an intervention for patients with limited ranges of motion (ROMs). However, concrete experimental support for such practice is lacking. The purpose of the study was to evaluate the effect of simulated dorsal and ventral translational mobilization (DTM and VTM) of the glenohumeral joint on abduction and rotational ROMs. METHODS: Fourteen fresh frozen shoulder specimens from 5 men and 3 women (mean age=77.3 years, SD=10.1, range=62-91) were used for this study. Each specimen underwent 5 repetitions of DTM and VTM in the plane of scapula simulated by a material testing system (MTS) in the resting position (40 of abduction in neutral rotation) and at the end range of abduction with 100 N of force. Abduction and rotation were assessed as the main outcome measures before and after each mobilization procedure performed and monitored by the MTS (abduction, 4 N m) and by a servomotor attached to the piston of the actuator of the MTS (medial and lateral rotation, 2 N m). RESULTS: There were increases in abduction ROM for both DTM (mean=2.10 , SD=1.76 ) and VTM (mean=2.06 , SD=1.96 ) at the end-range position. No changes were found in the resting position following the same procedure. Small increases were also found in lateral rotation ROM after VTM in the resting position (mean=0.90 , SD=0.92 , t=3.65, P=.003) and in medial rotation ROM after DTM (mean=0.97 , SD=1.45 , t=2.51, P=.026) at the end range of abduction. DISCUSSION AND CONCLUSION: The results indicate that both DTM and VTM procedures applied at the end range of abduction improved glenohumeral abduction range of motion. Whether these changes would result in improved function could not be determined because of the use of a cadaver model.     

Effect of prior experience and task stability on the intrinsic muscle activity of the thumb

Manual techniques involving the use of the thumb are commonly employed by physical therapists for treating patients with vertebral disorders. The demands on the intrinsic muscles of the thumb in these manual tasks are very different from those of the pinch tasks. The aim of this study was to investigate the influence of clinical experience and different mobilization techniques on the electromyographic activity (EMG) of thumb intrinsic muscles. Fifteen participants without exposure to manual techniques (the Novice Group) and fifteen physical therapists with at least 3 years of orthopaedic experience (the Experienced Group) participated. Each participant exerted thumb tip forces with 3 different posterioanterior (PA) glide techniques including unsupported, with digital support and with thumb interphalangeal joint supported by the index finger. The exerted force was increased from 25% to 100% maximum force at 25% increments on a 6 component load cell. The thumb tip force and EMG activity of four intrinsic muscles (flexor pollicis brevis, adductor pollicis, abductor pollicis brevis, first dorsal interosseus) were recorded with surface electrodes. Both experience and technique influenced intrinsic muscle activity of the thumb. While participants of both groups generated the same magnitude of force, experienced participants generated less intrinsic muscle activity while performing PA glide through practice. However, novice participants increased activity of the intrinsic muscles in accordance with the stability status of the technique. PA glide with thumb interphalangeal joint supported by the index finger was a more stable technique as evidenced by smallest relative errors of thumb tip force.     

Development of an instrumented couch to measure forces during manual physiotherapy treatment

This paper reports on an instrumented couch developed to measure the forces applied during posteroanterior (PA) mobilization to the lumbar spine. The couch was evaluated for reliability by applying known weights to the empty couch, while accuracy was investigated by applying weights both to the empty couch and to a human subject lying on the couch. The equipment appears highly reliable when measuring forces in three directions (ICC(2,1); 99% CI=0.99-1.00) and also demonstrates acceptable accuracy; a maximum error of less than 2% being obtained when measuring forces applied to human subjects. The results demonstrate a highly linear relationship (r2=0.99) between the force readings and the known weights. In conclusion, the instrumented couch demonstrates suitable accuracy and reliability for measuring the force applied to a subject during the application of PA mobilization to the lumbar spine.     

Alternative Methods for Measuring Scapular Muscles Protraction and Retraction Maximal Isometric Forces

Background

The importance of the scapular stabilizing muscles has led to an increased interest in quantitative measurements of their strength. Few studies have measured isometric or concentric isokinetic forces. Additionally, limited reports exist on the reliability of objective measures for testing scapular protraction and retraction muscle strength or scapular testing that does not involve the glenohumeral joint.

Objective

To determine the reliability of four new methods of measuring the maximal isometric strength of key scapular stabilizing muscles for the actions of protraction and retraction, both with and without the involvement of the glenohumeral (GH) joint.

Methods

The Isobex® stationary tension dynamometer was used to measure the maximal isometric force (kg) on thirty healthy females (ages 22–26 years). Three measures were taken for each method that was sequentially randomized for three separate testing sessions on three nonconsecutive days.

Results

Intraclass correlations (ICC2,3) for intrasession reliability and (ICC3,3) for intersession reliability ranged from 0.95 to 0.98, and 0.94 to 0.96 respectively. The standard errors of measurement (95% confidence interval [CI]) were narrow. Scatter grams for both protraction and retraction testing methods demonstrated a significant relationship, 0.92 for protraction (95% CI 0.83 to 0.96) and 0.93 for retraction (95% CI 0.87 to 0.97). Bland-Altman plots indicated good agreement between the two methods for measuring protraction strength but a weaker agreement for the two methods measuring retraction strength.

Discussion/Conclusion

The four new methods assessed in this study indicate reliable options for measuring scapular protraction or retraction isometric strength with or without involving the GH joint for young healthy females.     

Effectiveness of two forms of feedback on training of a joint mobilization skill by using a joint translation simulator

BACKGROUND AND PURPOSE: Joint mobilization is a complicated task to learn and to teach and is characterized by great intersubject variability. This study's purpose was to investigate whether quantitatively augmented feedback could enhance the learning of joint mobilization and, more specifically, to compare the effects of training with concurrent or terminal feedback by using a joint translation simulator (JTS). SUBJECTS: Thirty-six undergraduate physical therapist students were randomly assigned to control (no feedback), concurrent feedback, and terminal feedback groups. METHODS: The JTS was designed to simulate tissue resistance based on load-displacement relationships of glenohumeral joint specimens. Subjects applied specific mobilization grades of force on the JTS while quantitative feedback was given to the feedback groups either during a trial (ie, concurrent feedback) or after a trial (ie, terminal feedback). The skill acquisition phase lasted a total of 40 minutes, and a total of 75 repetitions were performed for each grade of each joint model. Pretest and no-feedback retention tests were conducted. RESULTS: During acquisition and retention, both feedback groups performed more accurately than did the control group. No obviously superior performance was shown by the terminal feedback group compared with concurrent feedback group during retention testing. DISCUSSION AND CONCLUSION: Subjects who trained with augmented feedback had less variability, and thus more consistency, than the control group subjects who received no feedback. Augmented feedback provides the student with a reference force and the status of his or her performance. The effectiveness of the JTS feedback compared with no feedback was clearly demonstrated. Skill acquisition in mobilization can be enhanced by either concurrent or terminal feedback.     

Muscle force measured using "break" testing with a hand-held myometer in normal subjects aged 20 to 69 years

OBJECTIVE: To measure the strength of 17 muscle groups in the upper and lower extremities in a large group of healthy subjects using "break" testing with a hand-held myometer, and to examine the intrasession and intersession reliability of the testing protocol. SUBJECTS AND INSTRUMENTATION: A convenience sample of 20 men and 20 women in each decade of age from 20 to 69 years (n = 200) was tested using a Penny & Giles hand-held myometer. RESULTS: Reliability coefficients were >.85 for both intrasession and intersession reliability, except for the ankle dorsiflexors. Men exerted a significantly greater force than women for all muscle groups. Age, weight, and side of testing were significant predictors of force in the majority of muscle groups. The fifth percentile values, as the lower limit of normal, are reported separately for gender and side of testing for each decade of age. CONCLUSION: Using the testing protocol specified in this study, data from patients with various neuromuscular diseases may be compared with the appropriate gender- and age-matched normal data to accurately identify the presence of weakness.     

Joint position during anterior-posterior glide mobilization: its effect on glenohumeral abduction range of motion

OBJECTIVE: To investigate the effect of joint position during an anterior-posterior glide (APG) procedure on the range of motion (ROM) of glenohumeral abduction in cadaver specimens. DESIGN: Mechanical simulation of APG mobilization and abduction torque ROM measurement of the glenohumeral joint with a material testing system. The immediate mechanical efficacy of APG was compared in two groups of specimens at two different joint positions: midrange (n = 5) and end range (n = 6) of glenohumeral abduction. SETTING: Biomechanics laboratory. SPECIMENS: Eleven fresh cadaver shoulder specimens (mean age, 66.9+/-2.5 yrs). MAIN OUTCOME MEASURE: Improvement in glenohumeral abduction torque ROM obtained before and after APG procedure. RESULTS: Glenohumeral abduction improved significantly, as indicated by a significant increase (Kruskal-Wallis statistics, chi2 = 7.50, p = .006) in the torque ROM of the end range group (mean +/- standard error of the mean, 2.02 degrees +/- .20 degrees) over the midrange group (.64 degrees +/- .08 degrees). A significant difference in the magnitude of peak displacement of the humeral head between midrange (14.44+/-3.56 mm) and end range (3.19+/-.81 mm) groups was also found (Mann-Whitney test, p < .030). CONCLUSION: This study demonstrated that APG technique performed at close to the end of the range of abduction is more effective in improving glenohumeral abduction ROM than that performed at the middle of the range of abduction.     

Inter-clinician and intra-clinician reliability of force application during joint mobilization: A systematic review

Joint mobilizations are commonly used by clinicians to decrease pain and restore joint arthrokinematics following musculoskeletal injury. The force applied during a joint mobilization treatment is subjective to the individual clinician but may have an effect on patient outcomes. The purpose of this systematic review was to critically appraise and synthesize the studies which examined the reliability of clinicians' force application during joint mobilization. A systematic search of PubMed and EBSCO Host databases from inception to March 1, 2013 was conducted to identify studies assessing the reliability of force application during joint mobilizations. Two reviewers utilized the Quality Appraisal of Reliability Studies (QAREL) assessment tool to determine the quality of included studies. The relative reliability of the included studies was examined through intraclass correlation coefficients (ICC) to synthesize study findings. All results were collated qualitatively with a level of evidence approach. A total of seven studies met the eligibility and were included. Five studies were included that assessed inter-clinician reliability, and six studies were included that assessed intra-clinician reliability. The overall level of evidence for inter-clinician reliability was strong for poor-to-moderate reliability (ICC = −0.04 to 0.70). The overall level of evidence for intra-clinician reliability was strong for good reliability (ICC = 0.75–0.99). This systematic review indicates there is variability in force application between clinicians but individual clinicians apply forces consistently. The results of this systematic review suggest innovative instructional methods are needed to improve consistency and validate the forces applied during of joint mobilization treatments. This is particularly evident for improving the consistency of force application across clinicians.     

Reliability of clinical measurements of forward bending using the modified fingertip-to-floor method

The purpose of this study was to examine the intratherapist and intertherapist reliability of measurements obtained with a modified version of the fingertip-to-floor method of assessing forward bending. With the modified fingertip-to-floor (MFTF) method, patients stand on a stool and forward bend so that measurements can be taken on patients who are able to touch the floor or reach beyond the level of the floor. Randomly paired physical therapists took repeated MFTF measurements on 73 patients with low back pain. Intraclass correlation coefficients (ICCs) were calculated for intratherapist and intertherapist reliability. The ICC value for intratherapist reliability was .98, and the ICC value for intertherapist reliability was .95. The results of this study suggest that measurements of forward bending obtained on patients with low back pain using the MFTF method are highly reliable.     

Untersuchung zur Reliabilität und Validität der dreidimensionalen Funktionsanalyse des Kiefergelenks

Background

Movement disorders are concluded responsible for pain and temporomandibular dysfunction. No uniform standards have been established yet for functional analysis of the temporomandibular joint. Especially, there is a lack of evidence in terms of psychometric criteria of such measurements. The aim of this study was to evaluate the reliability and validity of a three-dimensional motion analysis of temporomandibular joint in healthy subjects.

Material and methods

30 healthy subjects (15 females and 15 males) aged between 18 and 40 years volunteered for the study. A physical examination as well as three repetitions of a 3D motion analysis of the temporomandibular joint were performed using ultrasound-propulsion based Zebris equipment. The whole procedure was repeated after seven days. ICC was calculated for reliability and Pearsons correlation coefficient for convergent validity of the apparative procedure as compared with the manual examination.

Results

Intrasession as well as intersession reliability was found very good (greater 0.8) for all movement directions. No substantial differences were found between the intra- and intersession reliability. Further high correlation’s were found between the manual examination and the 3D motion analysis in all parameters with exception of the maximal opening distance.

Discussion

Due to unique equipment used the results are barely comparable with other results reported yet. Motivation of the volunteers as well as pain avoidance strategy during maximal mouth opening performed very rarely in the daily living could be responsible for the low validity of this parameter.

Conclusions

The 3D movement analysis is a highly reliable and valid instrument for evaluating function of the temporomandibular joint. The measurement objectivity seems to be also high as indicated by the low difference between the intrasession and intersession reliability. Further research is needed to evaluate the psychometric quality of the method in patients suffering from temporomandibular dysfunction.     

Anterior glenohumeral force/translation behavior with and without rotator cuff contraction during clinical stability testing

OBJECTIVE: Measure stiffness of the glenohumeral joint during clinical laxity testing with and without muscular contraction of the Internal rotators. DESIGN: Cross-sectional study of normal shoulders. BACKGROUND: Clinical examination for shoulder instability is based on subjective impression, and is only performed passively. Our study presents a method for quantitative clinical examination of the shoulder under both passive and active muscle contraction conditions. We hypothesized that in a normal shoulder, contraction of the internal rotators will increase the stiffness of the glenohumeral joint, effectively constraining the head of the humerus against anterior directed forces. METHODS: Ten subjects were instrumented with electromagnetic sensors to record glenohumeral linear displacements. A mini-force transducer recorded forces applied to subjects during anterior drawer testing (forced anterior glenohumeral displacement), which was performed passively, and during isometric contraction of internal rotators. RESULTS: Only mild contraction of the internal rotators is needed to significantly increase the stiffness to anterior directed forces. Greater muscular activation does not result in further increased stiffness. CONCLUSION: Objective measurement of glenohumeral stiffness during passive and active muscular contraction may be useful for evaluating the capacity of rotator cuff muscles to stabilize the shoulder. The concept of more strength is better, for rotator cuff strengthen programs is questioned.     

Test-retest reliability of isokinetic muscle strength of the lower extremities in patients with stroke

OBJECTIVE: To i the test-retest reliability of isokinetic strength measurements of 3 muscle groups of the lower extremities in stroke patients. DESIGN: Isokineth tests of bilateral hip flexors, knee extensors, and ankle plantarflexors at 2 angular velocities, performed during 2 sessions scheduled 1 week apart for each subject. SETTING: Outpatilitation clinic of a local hospital in Taiwan. PARTICIPANTS: Nts with mild spastic hemiparesis secondary to stroke and with poststroke onset time of at least 6 months. All subjects could communicate and voluntarily move the affected lower extremity. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The maximal peak torque, total work, and average power of the 3 muscle groups on the affected side examined during each test were quantified by using the normalization and the deficit methods. The normalization method divides the measured strength value by the patient's body weight, whereas the deficit method divides the difference between the strengths of the unaffected and affected extremities by the strength of the unaffected extremity. RESULTS: The normalized strength measures for muscles on the affected side showed good to excellent test-retest reliability (intraclass correlation coefficient [ICC] range,.62-.94; P<.05), whereas the deficit strength measures did not always show good reliability (ICC range,.13-.91). The knee extensors and ankle plantarflexors, but not the hip flexors, on the affected side showed better test-retest reliability of isokinetic strength generated at faster velocity (ICC range,.73-.94) than that generated at slower velocity (ICC range,.62-.88). The normalized peak torque (ICC range,.76-.94) and total work (ICC range,.83-.91) were more reliable than the normalized average power (ICC range,.62-.90) for all 3 muscle groups on the affected side. CONCLUSIONS: Quantitative assessment of muscle strength of the affected lower extremity in patients with mild spastic hemiparesis secondary to stroke is feasible using isokinetic testing. However, the test-retest reliability of isokinetic strength measures is affected by the quantifying method, testing velocity, and strength measures.     

Displacement of the head of humerus while performing "mobilization with movements" in glenohumeral joint: a cadaver study

The purpose of this study was to compare the displacement of the center of the humeral head (CHH), in a cadaveric glenohumeral joint model, during an experimental abduction simulation with and without the application of a mobilization with movement (MWM) maneuver in an anteroposterior direction. Ten physiotherapists performed passive abduction and a posteriorly directed MWM technique on a fresh cadaveric shoulder joint. The applied forces and joint angles were monitored and displacement of the CHH was calculated. In the abduction only trial, displacement of the humeral head was less than 0.9 mm in posterior, inferior, and lateral directions. During the MWM trial there were significant increases in the displacement of the humeral head posteriorly (7.7 mm), inferiorly (2.7 mm), and laterally (0.5 mm) below 52 degrees of abduction. We suggest that the MWM technique may be effective in changing the joint kinematic characteristics during glenohumeral abduction. This hypothesis, however, would need to be tested in vivo with abduction performed actively.     

The test-retest reliability of the child-initiated pretend play assessment.

OBJECTIVE: The purpose of this study is to establish the test-retest reliability of the Child-Initiated Pretend Play Assessment (ChIPPA) (Stagnitti, 2002a; Stagnitti, Unsworth, & Rodger, 2000). METHOD: The first author rated 38 preschool children ages 4 and 5 years (4 with developmental delay and 34 typically developing) on the ChIPPA. The ChIPPA employs conventional play materials and unstructured play materials to assess three qualities of a child's play ability: elaborateness of play action, ability to substitute objects during play, and the child's need to imitate the modelled actions of the examiner. The ChIPPA was administered twice, at a 2-week interval, to each participant. RESULTS: Test-retest intraclass correlation coefficients (ICCs) (Type 2,1) calculated for each of the three elaborate play measures ranged from .73 to .84. A test-retest ICC of .56 was obtained for object substitution with unstructured play materials. The test-retest ICC obtained for the combined score for unstructured and conventional play materials was .57. Percentage agreement figures ranging from 63.2% to 84.2% were obtained on test-retest of the object substitution with conventional toys and imitated actions measures. There was no significant difference between test and retest scores for these measures based on a Wilcoxon Matched Pairs Signed-Ranks Test (Wilcoxon Sign Test). CONCLUSION: Elaborate play scores, object substitution with conventional toys score, and imitation scores on the ChIPPA showed stability over time. Object substitution scores using unstructured materials were the least stable play measures and appeared to be related to the child's play themes. Since play is the primary occupation of children, it is essential that therapists have a reliable measure of play behavior. The test-retest reliability results from the ChIPPA provide evidence that this assessment produces a stable measure of play behavior that can then guide therapists when planning intervention strategies for children.     

Reliability of Center of Pressure Measures for Assessing the Development of Sitting Postural Control

Kyvelidou A, Harbourne RT, Stuberg WA, Sun J, Stergiou N. Reliability of center of pressure measures for assessing the development of sitting postural control.

Objectives

To determine the reliability of linear and nonlinear tools, including intrasession and intersession reliability, when used to analyze the center of pressure (COP) time series during the development of infant sitting postural control.

Design

Longitudinal study.

Setting

University hospital laboratory.

Participants

Typically developing infants (N=33; mean ± SD age at entry in the study, 152.4±17.6d).

Interventions

Not applicable.

Main Outcome Measures

Infants were tested twice in 1 week at each of the 4 months of the study. Sitting COP data were recorded for 3 trials at each session (2 each month within 1 week). The linear COP parameters of root mean square and range of sway for both the anterior-posterior and the medial-lateral directions, and the sway path, were calculated. The nonlinear parameters of approximate entropy, Lyapunov exponent, and correlation dimension for both directions were also calculated. Intrasession and intersession reliability was quantified by the intraclass correlation coefficient (ICC).

Results

The nonlinear tool of approximate entropy presented high intrasession and intersession ICC values compared with all other parameters evaluated. Generally, intrasession and intersession reliability increased in the last 2 months of the data collection and as sitting posture matured.

Conclusions

Our results showed that the evaluation of COP data is a reliable method of investigating the development of sitting postural control. The present study emphasizes the need for establishing COP reliability before using it as a method of examining intervention progress directed at improving the sitting postural abilities in infants with motor developmental delays.