Abstract
Background:
Although upper extremity (UE) closed kinetic chain (CKC) exercises have become commonplace in most rehabilitation programs, a clinically meaningful UE CKC functional test of unilateral ability has continued to be elusive.
Objectives:
To examine reliability of the Upper Quarter Y-Balance Test (UQYBT), evaluate the effects of arm dominance on UQYBT performance, and to determine how the UQYBT is related to specific components of the test (trunk rotation, core stability and UE function and performance) in a college-aged population.
Methods:
A sample of healthy college students performed the UQYBT and a series of 6 additional dynamic tests designed to assess trunk rotation, core stability, and UE performance. The relationship of these tests compared to the UQYBT was assessed. The effect of upper limb dominance for the UQYBT was also explored. Finally, test re-test reliability was established for the UQYBT.
Results:
Thirty subjects (24 males, 6 females, mean ages 19.5 6 1.2 and 18.8 6 0.8 years) were assessed during the study. The test re-test reliability was excellent for UQYBT measurements (intraclass correlation coefficient > 0.9). A significant (p <0.05) fair to moderate association was observed between the UQYBT and several core stability and UE functional tests. There was no significant difference in UQYBT performance between dominant and non-dominant limbs.
Discussion:
The UQYBT is a reliable UE CKC test that can be used to assess unilateral UE function in a closed chain manner. The UQYBT appears to be most related to dynamic tests involving core stability and UE performance. Similarity on the UQYBT between dominant and non-dominant limbs indicates that performance on this test using a non-injured UE may serve as a reasonable measure for “normal” when testing an injured UE. Future research is needed to determine the clinical applicability of the UQYBT.
Level of Evidence:
2b
Keywords: upper extremity functional testing, Upper quarter Y-Balance test
INTRODUCTION
Over a decade ago, Goldbeck and Davies highlighted the need for reliable and clinically relevant upper extremity (UE) functional testing as they reported reliability of the Closed Kinetic Chain UE Stability Test (CKCUEST).1 Over a decade later, the CKCUEST remains the only dynamic closed kinetic chain (CKC) test described in the literature to identify deficits in the UE.1 Because the CKCUEST essentially requires both UEs to function simultaneously, the primary limitation of this test is the inability to differentiate performance for a single limb. Therefore, a limb to limb comparison is not possible with the CKCUEST. A clinically viable and meaningful UE functional test has continued to be elusive.
For theoretically positive reasons, UE CKC exercises have become commonplace in most rehabilitation programs and have been described abundantly in the literature.2–13 Proposed benefits of these exercises include increased shoulder stability and proprioception. Inclusion of CKC exercises may also add specificity of training for many sports such as wrestling and football. Despite the general agreement that these exercises are beneficial, there is no universally accepted clinical assessment of upper body closed-chain ability.1,6,14–16
Tests such as the push-up test14,17,18 are simple and can be used to assess UE function in a closed chain manner. However, a limitation of this type of test may be the inability to sufficiently assess the upper quarter relevant to many sporting activities, because they do not require the subject to move beyond a limited base of support. Similarly, tests of the upper quarter, such as planks and side bridging are purely static tests, which require no dynamic movement of the UE.14,15,19
Tests and measures are an essential prerequisite for the development of rehabilitation and training programs.7,10,14 A well designed assessment gauges a person's ability and should provide a measurement that does not require extensive interpretation.15 Because the body operates as a dynamic unit in sports and activities of daily life, isolated clinical assessments of muscular strength and joint mobility do not adequately provide the information needed to assess functional ability or performance.8 CKC assessments of the UE have been appropriately described as testing the entire “upper quarter”.15,20 Testing of the core and extremities as quadrants can be an efficient and comprehensive method to identify performance, strength, or mobility deficits in the body region being tested.15,20
The upper quarter Y-balance test (UQYBT) has been proposed as a CKC assessment of upper quarter mobility and stability using a functional testing device (Figure 1).15,20 The assessment is performed with the subject stabilizing his or her body weight with the upper extremity being tested while performing maximal reaching in three directions. Recently, Gorman and colleagues reported good reliability using the UQYBT to measure upper quarter performance.20
Figure 1.
Upper Quarter Y-Balance Test - Direction of reach is named relative to the stationary upper extremity. A. Medial Reach Direction, B. Superior Lateral Reach Direction, C. Inferior Lateral Reach Direction.
A similar test of the lower quarter has been shown to be reliable21 with the ability to predict lower extremity injury in high school basketball players.22 It is possible that the UQYBT may provide similar information regarding performance, strength, and mobility deficits of the upper quarter.
Because of the limited knowledge regarding the UQYBT, the primary purpose of this study was to explore several objectives related to the use of the UQYBT. The first objective was to examine reliability of the UQYBT in a college-aged population. The second objective was to determine how the UQYBT related to specific components of the test (primarily trunk rotation, core stability and UE function and performance). The final objective was to evaluate the effects of arm dominance on performance on the UQYBT, which might assist the clinician in interpreting the results of an injured UE relative to the uninjured UE for an individual patient.
MATERIALS AND METHODS
Design and Setting
A convenience sample of thirty healthy, college-aged subjects was recruited from the United States Military Academy at West Point. Exclusion criteria included any UE or spine pain or injury within the previous 6 months, history of shoulder surgery, or current illness or disease process affecting physical performance. Subjects were provided written and verbal explanation of the testing procedures and provided written informed consent prior to testing. The Institutional Review Board at Keller Army Community Hospital approved the study protocol.
Procedures and Protocols
Primary testing was completed in one session for each subject. Subjects completed a general information questionnaire, the Shoulder Pain and Disability Index (SPADI), and the Disability of the Arm, Shoulder, and Hand (DASH) outcome measure to establish general health, UE dominance (defined as the arm preferred for throwing), and overall shoulder ability. Descriptive data measured for all subjects included age, weight, height, upper limb length, hand length, and torso length. Army Physical Fitness Test (APFT) 2-minute push-up and 2-minute sit-up scores were also recorded.
Upper limb length was measured with the shoulder abducted to 90 degrees with the elbow extended and the wrist and hand in neutral. The measurements were taken from the spinous process of C7 to the tip of the longest digit. Torso length was measured from the spinous process of C7 to a horizontal line corresponding to the iliac crest height. Hand length was measured from the distal wrist crease to the tip of the longest digit.
The Upper Quarter Y-Balance Test (UQYBT) and a series of 6 additional dynamic tests were assessed in addition to shoulder active range of motion (AROM) and isometric strength testing. The sequence of testing order was randomized into 3 testing sequences to mitigate an order effect. The subjects rested for two minutes between trials of dynamic tests to prevent effects of fatigue. Standardized instructions and demonstrations of the tests were provided to subjects prior to each test.
UQYBT
The UQYBT was performed as suggested by previous authors.15,20 While maintaining a pushup position with the feet no more than twelve inches apart, the subject performed maximal effort reaches with the free hand in three directions (medial, superolateral, and inferolateral) named in relation to the stationary hand (Figure 1). The distance reached in each direction was recorded. Each subject was allowed 3 practice trials prior to testing. The average of 3 trials was used for analysis. The sum of the 3 reach directions was calculated for a total excursion score. To normalize for limb length, a composite score was calculated taking the total excursion distance and dividing it by 3 times the upper limb length.
Closed Kinetic Chain Upper Extremity Stability Test
The CKCUEST has been described as a reliable clinical tool allowing functional assessment of a subject's UE in a CKC.1,14 The CKCUEST begins in the traditional push-up position with the hands placed just inside athletic tape markers placed 36 inches apart. During the CKCUEST, subjects reached with alternating hands across their body to touch the athletic tape under the opposing hand. The number of cross-body touches performed in 15 seconds was recorded. The average of 3 trials was used for analysis.
Shoulder Active Range of Motion and Isometric Strength Testing
Shoulder AROM was measured for flexion, abduction, internal rotation and external rotation using a standard goniometer. Shoulder isometric strength testing was measured using a handheld dynamometer (MODEL #01163, Lafayette Instrument Company, Lafayette, IN) in an upright-seated position for flexion, abduction, internal and external rotation, as well as internal and external rotation at 45 degrees of abduction in supine. The average of 3 trials was used for analysis. Intrarater reliability values in this study for hand-held dynamometer isometric testing ranged from good to excellent (ICC= 0.86 left shoulder IR to ICC=0.98 right shoulder flexion).
Shoulder Mobility Reach Test
The Shoulder Mobility Reach Test (SMRT) assesses combined extension, internal rotation and adduction on one shoulder while simultaneously assessing combined flexion, external rotation, and abduction in the other.19 To perform the SMRT the subjects reached as far as possible behind their neck with one hand, while reaching behind the back with the opposite hand. The distance between the hands was recorded. The SMRT was intended to evaluate thoracic spine and scapular mobility as well as actual shoulder motion. The average of 3 trials was used for analysis. SMRT intrarater reliability in this study was the same for both sides (ICC=0.99).
Trunk Rotation Test
Side-lying trunk rotation measurements (STRM) were conducted as described by Iveson et al.24 The subject was positioned side-lying with hips and knees bent to 90 degrees (90/90 position). The subjects rotated their trunk back onto the treatment table posteriorly to approximate the scapulae to the table. Measurements for this study were taken using a digital inclinometer (Model: 12-1057, Baseline, Elmsford, NY) positioned across the medial clavicles. The average of 3 trials was used for analysis. Intrarater reliability for the STRM in this study was similar for right and left rotation (ICC=0.94 left, ICC=0.95 right).
Lateral Trunk Endurance Test (Side Bridge)
The Lateral Trunk Endurance Test (LTET) was included to assess the endurance of the shoulder and lateral trunk musculature.19 The subjects were positioned side-lying with their legs extended. The top foot was placed in front of the lower foot for support and the free hand was placed on the shoulder of the stance limb with the arm across the chest. Subjects lifted their hips off the surface to maintain a straight line over their body while supporting themselves with the stance limb and the sides of the feet. The test was terminated when the subject was no longer able to maintain position after one warning or 240 seconds (actual test not to exceed 240 seconds).
Trunk Extensor Endurance Test
The Trunk Extensor Endurance Test was used to assess the endurance of the trunk extensor muscles.19 Subjects were positioned prone with their torso off the edge of a treatment table/plinth. The anterior superior iliac spine (ASIS) was positioned as close to the edge of the plinth as possible but still supported by the plinth. A 6” foam bolster was placed under subjects' ankles for comfort and 2 padded belts were used to secure the subject at the mid-thigh and mid-leg. Subjects were required to maintain a horizontal position of the torso for as long as possible. The test was terminated when the subject was unable to maintain position after one warning or 240 seconds (actual test not to exceed 240 seconds).
Trunk Flexor Endurance Test
The Trunk Flexor Endurance Test was used to assess the endurance of the trunk and hip flexor muscles.19 Subjects were placed in a sit-up position on a treatment table/plinth. A padded belt was used to secure the subject at the proximal ankles. Subjects were required to maintain a 45 degree flexed position of the trunk for as long as possible. The test was terminated when the subject was unable to maintain position after one warning or 240 seconds (actual test not to exceed 240 seconds).
Reliability
To assess test re-test reliability of the UQYBT, half of the subjects (n=15) were contacted for retesting a minimum of 2 weeks following the initial assessment. Testing procedures mirrored those during initial testing. To be included in this portion, subjects had to report no musculoskeletal injury since the initial testing and that general health was unchanged.
Statistical Analysis
Descriptive statistics were calculated including means, standard deviations, and 95% confidence intervals (CI) for all tests and measures. Limb Symmetry Index (LSI) was calculated using the furthest distance reached on the UQYBT as the reference limb (i.e., percentage of the lesser distance reached divided by the furthest distance reached). Test re-test reliability of the UQYBT was determined using the intraclass correlation coefficient (ICC) statistic. The association between the various performance tests and the UQYBT scores were analyzed using the Pearson Correlation. Potential differences between dominant UE and non-dominant UE performance on the UQYBT were assessed using the independent t-Test.
Results
Thirty subjects (24 males, 6 females, mean ages 19.5 ± 1.2 and 18.8 ± 0.8 years; mean height 174.4 cm ± 4.9 and 164.8 cm ± 5.3; mean weight 73.9 kg ± 6.0 and 56.3 kg ± 7.5; mean upper limb length 89.5 cm ± 2.9 and 82.4 cm ± 2.0) were assessed during the study. No subject reported any UE disability on the SPADI or DASH questionnaires. Descriptive variables and demographic data are presented in Table 1.
Table 1.
Demographics.
| Males (N = 24) | Females (N = 6) | |
|---|---|---|
| Age (yrs) | 19.5 (1.2) | 18.8 (0.8) |
| Height (cm)* | 174.4 (4.9) | 164.8 (5.3) |
| Weight (kg)* | 73.9 (6.0) | 56.3 (7.5) |
| Upper Limb Length (cm)* | 89.5 (2.9) | 82.4 (2.0) |
Significant difference between males and females (p<.001)
Abbreviations: yrs, years; cm, centimeters; kg, kilograms.
Reliability
Thirteen of the fifteen subjects contacted were retested on the UQYBT an average of 28 days following initial testing (range 19–47 days). One subject was unable to return due to scheduling conflicts and another reported having injured his shoulder two weeks prior and was therefore excluded from the reliability analysis. The UQYBT test re-test reliability values were similar for both dominant (ICC=0.91) and non-dominant (ICC=0.92) UE measurements.
Performance Test Correlations
There was a significant relationship observed between the UQYBT and core stability measures (i.e., Dominant side LTET; p=0.04, r=0.38; Non-dominant LTET; p=0.01, r=0.45) and UE CKC performance measures (i.e., CKCUEST p=0.01, r=0.49 and APFT pushups p=0.02, r=0.41) (Table 2). There was not a significant relationship observed between the UQYBT and measures of trunk rotation, trunk flexor and extensor endurance tests, APFT sit-ups, shoulder AROM, or shoulder isometric strength.
Table 2.
Performance test correlations.
| Dominant Side UQYBT Total Excursion |
Non-dominant Side UQYBT Total Excursion |
|||
|---|---|---|---|---|
| Performance Test | Pearson's | p value | Pearson's | p value |
| Push-Ups* | 0.34 | 0.07 | 0.41 | 0.02 |
| Sit-Ups | 0.25 | 0.19 | 0.33 | 0.08 |
| Trunk Flexor Endurance | 0.21 | 0.26 | 0.23 | 0.24 |
| Trunk Extensor Endurance | 0.27 | 0.15 | 0.23 | 0.23 |
| Dominant LTET* | 0.35 | 0.06 | 0.38 | 0.04 |
| Non-dominant LTET* | 0.40 | 0.03 | 0.45 | 0.01 |
| CKCUEST* | 0.43 | 0.02 | 0.49 | 0.01 |
| STRM (dominant side) | 0.17 | 0.37 | 0.14 | 0.48 |
| STRM (non-dominant side) | 0.19 | 0.31 | 0.25 | 0.19 |
Significant association observed at p < 0.05*
Abbreviations: UQYBT, Upper Quarter Y-Balance Test; LTET, Lateral Trunk Endurance Test; CKCUEST, Closed Kinetic Chain Upper Extremity Stability Test; STRM, side-lying trunk rotation measurement.
Limb Dominance and Limb Symmetry Index
Reach distances for the medial, superolateral, and inferolateral directions, the total excursion, and the composite score as well as limb symmetry indices are presented in Table 3. There was no statistically significant difference between dominant and non-dominant limbs on any of the measures (p value range=0.39-0.76); however, performance in each direction of the UQYBT was greater when the non-dominant UE was being tested as the stabilizing limb. The LSI was above 98% for the medial, inferolateral, and total excursion measurements and approximately 95% for the superolateral measurement.
Table 3.
UQYBT Performance by upper extremity dominance.
| Performance Test | Dominant UE | Non-Dominant UE | LSI |
|---|---|---|---|
| UQYBT Medial Reach (cm) | 86.0 (8.0) | 86.5 (7.8) | 99.4% |
| UQYBT Superolateral Reach (cm) | 58.2 (8.5) | 61.2 (9.3) | 95.1% |
| UQYBT Inferolateral Reach (cm) | 82.5 (12.2) | 83.5 (12.1) | 98.8% |
| UQYBT Total Excursion (cm) | 226.8 (22.7) | 231.2 (23.3) | 98.1% |
| UQYBT Composite Score | 85.7 (8.3) | 87.6 (8.3) | 97.9% |
Abbreviations: UQYBT, Upper Quarter Y-Balance Test; UE, Upper Extremity; LSI, Limb Symmetry Index; cm, centimeters.
A post hoc analysis comparing genders revealed that while males consistently demonstrated higher performance levels on each of the performance tests, there was no statistical difference between the genders on the CKCUEST, trunk flexor and extensor endurance tests, and the normalized UQYBT composite score (Table 4).
Table 4.
Performance test values.
| Performance Test | Males (n = 24) | Females (n = 6) |
|---|---|---|
| Push-ups§ | 77 (17) | 41 (9) |
| Sit-ups* | 78 (11) | 62 (11) |
| Trunk Flexor Endurance (sec) | 139.7 (54.5) | 119.0 (50.2) |
| Trunk Extensor Endurance (sec) | 151.5 (52.0) | 138.2 (63.3) |
| Dominant LTET (sec)* | 129.0 (52.4) | 76.0 (26.7) |
| Non-dominant LTET (sec)* | 124.2 (47.7) | 70.5 (30.4) |
| CKCUEST | 18.8 (3.3) | 15.9 (4.5) |
| Dominant Side UQYBT Excursion (cm)* | 232.3 (20.0) | 205.5 (21.9) |
| Dominant Side UQYBT Composite | 86.5 (8.1) | 82.9 (9.20) |
| Non-dominant Side UQYBT Excursion (cm)* | 236.1 (18.6) | 210.5 (30.1) |
| Non-dominant Side UQYBT Composite | 88.1 (7.4) | 85.2 (11.7) |
Significant difference between males and females at p<.05.
Significant difference between males and females at p<.001.
Abbreviations: LTET, Lateral Trunk Endurance Test; CKCUEST, Closed Kinetic Chain Upper Extremity Stability Test; UQYBT, Upper Quarter Y-Balance Test; sec, seconds; cm, centimeters.
DISCUSSION
The UQYBT was found to be a reliable assessment of unilateral UE CKC excursion ability in healthy college-aged subjects, confirming the reliability reported by Gorman et al.20 Results also indicated there is a significant, albeit moderate relationship between performance on the UQYBT and the LTET, CKCUEST, and push-ups. This suggests that the tests are interrelated but do not necessarily assess equal components of UE CKC ability. Finally, there was no difference in UQYBT performance between dominant and non-dominant limbs. The symmetry between limbs indicates that non-injured UE performance may serve as a reasonable baseline measure when testing an injured UE, regardless of dominance.
The UQYBT is the first reliable test designed to assess unilateral UE dynamic function in a purely CKC manner.20 While the CKCUEST has been reported to be a reliable assessment of UE performance,1 the greatest limitation with this test is the inability to account for the degree of unilateral limb difference due to injury or other factors. The UQYBT enables independent upper limb assessments, which would allow for comparisons to be made between injured and non-injured limbs. Calculating the LSI using such unilateral assessments is appealing in the clinical setting. Based on the results of this study, UQYBT performance of a non-injured limb appears to be an appropriate reference for “normal” within an individual.
One of the objectives of this research was to understand more fully what the UQYBT measures. Ultimately, the UQYBT appears to be most related to dynamic tests involving core stability (i.e., LTET) and UE CKC performance (i.e., CKCUEST and pushups) and does not appear to be related to trunk rotation, shoulder AROM, or shoulder isometric strength. There was a statistically significant fair (dominant side) to moderate (non-dominant side) correlation between the UQYBT and the CKCUEST. These results suggest that the two tests are interrelated but measure different components or functions. Because both tests require stabilization from being in the push-up position, one would expect some relationship between the two tests. However, during the UQYBT the stance limb is held in-place and the subject moves around that limb to reach with the opposite extremity. The performance on the UQYBT in reference to the stance limb is purely CKC with a fixed external load. In contrast, the CKCUEST does not appear to solely measure CKC ability. During the CKCUEST the subject's hands are repeatedly shifted back and forth from the ground while simultaneously lifting the contralateral limb to reach a target, for a total of 15 seconds. The CKCUEST is a rapid bilateral reaching test requiring the subject to essentially perform a combined OKC and CKC task. When observing subjects who score highest on the CKCUEST (greater than 25), the task appears to assess primarily UE plyometric ability.
There is conflicting information in the literature regarding upper limb dominance as it relates to strength and task performance.25–30 Sainburg proposed the dynamic dominance hypothesis in 2002,27 suggesting that neither upper limb is dominant, but that each is specialized for different aspects of sensorimotor performance. Goble and Brown25,28 suggested most individuals use the preferred arm to perform trajectory-dependent activities and prefer the “non-dominant” arm to stabilize objects. Cortez et al30 did not find a difference between dominant and non-dominant upper extremities using an isometric testing device. Westrick et al31 did find differences between shoulder isometric tests although the differences were not consistent in all positions. Finally, Kovaleski and colleagues26 reported a 12% CKC strength difference between dominant and non-dominant upper extremities using an isokinetic CKC testing device with the dominant limb being stronger than the non-dominant limb.
In the current study, no significant differences were observed between UQYBT performance in regards to limb-dominance, yet review of the mean values revealed the non-dominant limb performed better (as the stance limb) in each of the reach directions and subsequently achieved higher total excursion and composite scores as well. Similar to the dynamic dominance hypothesis that Sainburg27 proposed, these results suggest that while neither upper limb reach distance was statistically greater than the other, the non-dominant limb may be specialized somewhat for an aspect of sensorimotor performance that includes stabilization in some fixed external load CKC tasks. The relationship between functional UE dominance in OKC tasks and potential differences from CKC tasks warrants further investigation.
Limitations associated with this study should be addressed. The study was performed using a relatively small sample size and included only healthy individuals. Because these results are representative of a young, healthy population without UE or trunk pathology, conclusions should not be extrapolated to those with injuries or in older populations. A single tester collected all data during this study, including reliability measurements; therefore no information is available regarding interrater agreement. Gorman and colleagues reported excellent interrater reliability (ICC=1.00) in their test population.20
The authors have anecdotally noted side-to-side differences in performance on the UQYBT in patients with various UE musculoskeletal injuries as well as post-operative shoulder patients in later phases of rehabilitation. Additional research is necessary to establish the responsiveness of the UQYBT to wrist, elbow, and shoulder pathology. Further research is also needed to determine which muscles or muscle groups are recruited during performance on the UQYBT.
CONCLUSION
The UQYBT is a reliable UE CKC test that can be used to assess unilateral UE performance in a closed chain manner. There was a significant fair to moderate association between performance on the UQYBT and the CKCUEST, LTET, and push-ups. These results suggest the tests are interrelated but do not necessarily assess equal components of UE CKC ability. Similarity in performance bilaterally indicates that reach distances on this test using a non-injured UE (whether dominant or not) may serve as a reasonable baseline measure when comparing an injured and uninjured UE. Future research is needed to determine the clinical applicability of the UQYBT.
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