Journal of Sport Rehabilitation, 2015, 24, 62-67 http://dx.doi.org/10.1123/jsr.2013-0117 © 2015 Human Kinetics, Inc.
www.JSR-Journal.com ORIGINAL RESEARCH REPORT
Association of Ankle Kinematics and Performance on the Y-Balance Test With Inclinometer Measurements on the Weight-Bearing-Lunge Test Min-Hyeok Kang, Dong-Kyu Lee, Kyung-Hee Park, and Jae-Seop Oh Context: Ankle-dorsiflexion range of motion has often been measured in the weight-bearing condition in the clinical setting; however, little is known about the relationship between the weight-bearing-lunge test (WBLT) and both ankle kinematics and performance on dynamic postural-control tests. Objective: To examine whether ankle kinematics and performance on the Lower Quarter Y-Balance Test (YBT-LQ) are correlated with results of the WBLT using an inclinometer and tape measure. Design: Cross-sectional. Setting: University motionanalysis laboratory. Participants: 30 physically active participants. Interventions: None. Main Outcome Measures: The WBLT was evaluated using an inclinometer and a tape measure. The reach distances in the anterior, posteromedial, and posterolateral directions on the YBT-LQ were normalized by limb length. Ankle dorsiflexion during the YBT-LQ was recorded using a 3-dimensional motion-analysis system. Simple linear regression was used to examine the relationship between the WBLT results and both ankle dorsiflexion and the normalized reach distance in each direction on the YBT-LQ. Results: The WBLT results were significantly correlated with ankle dorsiflexion in all directions on the YBT-LQ (P < .05). A strong correlation was found between the inclinometer measurement of the WBLT and ankle dorsiflexion (r = .74, r2 = .55), whereas the tape-measure results on the WBLT were moderately correlated with ankle dorsiflexion (r = .64, r2 = .40) during the anterior reach on the YBT-LQ. Only the normalized anterior reach distance was significantly correlated with the results for the inclinometer (r = .68, r2 = .46) and the tape measure (r = .64, r2 = .41) on the WBLT. Conclusions: Inclinometer measurements on the WBLT can be an appropriate tool for predicting the amount of ankle dorsiflexion during the YBT-LQ. Furthermore, WBLT should be measured in those who demonstrate poor dynamic balance. Keywords: ankle joint, biomechanics, dynamic postural control, range of motion
Clinicians often emphasize the importance of measuring ankle-dorsiflexion (DF) passive range of motion (PROM) because limited ankle-DF PROM is associated with lower-extremity injuries and decreased functional performance.1,2 Ankle-DF PROM can be measured under either a non-weight-bearing or a weight-bearing condition.3,4 Compared with the non-weight-bearing condition, however, it has been suggested that measurement of ankle-DF PROM in the weight-bearing condition, such as during the weight-bearing-lunge test (WBLT), is more convenient for measurement and easier in terms of applying greater force to the ankle.3–5 Moreover, it is expected that the WBLT is appropriate for assessing
Kang, Lee, and Park are with the Dept of Rehabilitation Science, and Oh, the Dept of Physical Therapy, INJE University, Gimhae, South Korea. Address author correspondence to Jae-Seop Oh at [email protected]
functional requirements, as most functional activities including walking, running, and jumping are performed under weight-bearing conditions4,5; thus, measurement of ankle-DF PROM under the weight-bearing condition is preferred in the clinical setting. The WBLT is conducted using an inclinometer and a tape measure or goniometer.5–7 A previous study showed strong intrarater and interrater reliability of WBLT measurements using an inclinometer or tape measure, suggesting that these are reliable measurement tools for the WBLT.5 Although the goniometer is regarded as a cost-effective measurement tool, it requires skill to align the fulcrum and 2 arms of the goniometer.7,8 Konor et al7 reported higher intrareliability in the WBLT using an inclinometer (.96–.97) or tape measure (.98–.99) than when using a goniometer (.85–.96). The WBLT is reportedly associated with performance on dynamic postural-control tests such as the Star Excursion Balance Test (SEBT).9,10 Hoch et al10 found that tape measurements of the WBLT are significantly
Weight-Bearing-Lunge Test and Y-Balance Test 63
correlated with the anterior reach distance on the SEBT in individuals both with and without chronic ankle instability. This finding suggests that tape-measurement results of the WBLT may be associated with the anterior reach distance on dynamic postural-control tests. However, previous studies did not identify a relationship between inclinometer measurements of the WBLT and performance on dynamic postural-control tests. In the clinical setting, the newly developed Lower Quarter Y-Balance Test (YBT-LQ) is used to assess dynamic postural control.11–13 During the YBT-LQ, in contrast to the SEBT, individuals align the distal aspects of the toes of their stance foot with a starting line on the stance platform and push a reach indicator at the point of touchdown to measure the reach distance.11,13 This test may reduce the possibility of misinterpretation of measurements on the SEBT due to ambiguous definitions of the amount of support acquired through touchdown11 and alignment of the stance foot.14–16 In addition, the YBT-LQ includes only anterior, posteromedial, and posterolateral excursions, which minimizes the time requirement.13,17 Plisky et al11 reported good to excellent intrarater (.85–.91) and interrater (.99–1.00) reliability for YBT-LQ and suggested that the YBT-LQ can be a reliable dynamic postural-control test. Although previous studies have suggested that ankle DF-PROM measured under a weight-bearing condition may reflect the functional requirements of the ankle during weight-bearing activities,4,5 there is a lack of evidence supporting this assumption. The current information on the association between ankle-DF PROM under a weight-bearing condition and ankle kinematics during weight-bearing activities is limited. Furthermore, to our knowledge, no study has reported the relationship between results on the WBLT and ankle kinematics during dynamic postural-control tests, especially during the YBT-LQ. Furthermore, previous studies demonstrated a significant correlation only between the tape-measure results of the WBLT and performance on a dynamic postural-control test,9,10 although measurement by inclinometer has been identified as a reliable and convenient tool in the WBLT.7 Identification of the relationship between performance on the YBT-LQ and inclinometer and tape measurements on the WBLT will be helpful in understanding the relationship between ankle-DF PROM and weight-bearing performance during dynamic postural-control tests. Therefore, the aim of the current study was to examine the relationship between ankle kinematics in the sagittal plane during the YBT-LQ and WBLT performance and the relationship between the reach distance on the YBT-LQ and WBLT results as measured using both an inclinometer and a tape measure. Based on previous findings, we hypothesized that ankle kinematics during the YBT-LQ would be significantly correlated with the WBLT results and that performance on the YBT-LQ would be significantly correlated with both the inclinometer and tape measurements of the WBLT.
Methods Design Cross-sectional design was used to identify the relationship between results of the WBLT (inclinometer and tape measurements) and both ankle kinematics (DF angle at maximal reach on each direction) and performance (normalized reach distance at maximal reach on each direction) on the YBT-LQ.
Participants For this study, a total of 30 physically active participants (20 men and 10 women, mean age 22.57 ± 2.30 y, height 171.77 ± 7.21 cm, weight 65.90 ± 10.41 kg) volunteered and signed informed-consent forms approved by the Inje University Ethics Committee for Human Investigations. All participants engaged in sports activities 3 or more times a week, and individuals with a history of ankle sprains, surgery of the lower extremity, or vestibular disorders were excluded.
Procedures To acquire ankle kinematic data during the YBT-LQ, a Vicon MX-T10 motion-capture system (Vicon Motion Systems Ltd, Oxford, UK) with 8 cameras at a sampling rate of 100 Hz was used. A total of 16 reflective markers were placed bilaterally on the anterosuperior and posterosuperior iliac spines, lateral thighs, lateral knees, lateral tibias, lateral malleoli, second metatarsal heads, and posterior calcanei.18 The shank segment comprised the lateral knee, tibia, and malleolus, and the foot segment comprised the lateral malleolus, second metatarsal head, and posterior calcaneus. Ankle DF was defined as the relative motion of the foot segment with respect to the shank segment in the sagittal plane using Cardan angles.19 In this study, ankle DF in the stance limb at the maximal reach in the anterior, posteromedial, and posterolateral directions during the YBT-LQ was recorded for data analysis. To determine the point of maximal reach, 3 reflective markers were attached to each reach indicator, and the time point at which the velocity of the marker on the indicator reached zero was determined to be the point of maximal reach. The mean ankle DF during 3 test trials in each direction was calculated for data analysis. Participants performed the YBT-LQ using a Y-Balance test kit (Move2Perform, Evansville, IN, USA), which involves a stance platform, 3 plastic pipes, and reach indicators corresponding to the anterior, posteromedial, and posterolateral directions. Participants placed the tested limb on the stance platform and put their hands on their hips. The tested limb was determined as the nondominant limb,20 that is, the side opposite the preferred kicking limb, because previous studies showed no significant differences in performance on the dynamic postural-control test between limbs in healthy participants.21 Participants were instructed to push the reach
64 Kang et al
indicator as far as possible along the pipe without heel-off (Figure 1).13 Six practice trials were given to minimize learning effects,22 and 3 successive test trials were then performed in each direction. The order of directions was randomized. Participants were asked to try again if they placed the reach foot on the reach indicator for support, kicked the reach indicator for further reaching distance, lost their balance before returning to the start position (eg, contacting the ground with the reach foot or removing hands from hips), or did not maintain contact between the heel of the stance limb and the stance platform.12,13 For normalization of the reach distance, the reach distance in each direction was divided by the limb length from the anterosuperior iliac spine to the medial malleolus and then multiplied by 100.11–13 The mean value of the normalized reach distance in the 3 test trials in each direction was determined for data analysis. Measurement during the WBLT was performed using an inclinometer and tape measure as described by Bennell et al5 For the WBLT, participants placed the tested foot on the floor with the great toe and center of the heel perpendicular to the wall. Participants were instructed to lunge forward so that their knee contacted a line drawn on the wall. Foot position was moved progressively backward in 1-cm increments until the knee could not touch the wall without heel lift. Smaller increments of 0.1 mm were subsequently applied to achieve maximal ankle-DF PROM without heel lift. For the WBLT, the examiner placed the inclinometer (Zebris Medical GmbH, Isny, Germany) 15 cm below the tibial tuberosity and read the inclination of the tibia relative to vertical from the ground, and the distance from the wall to the great toe was recorded using a tape measure (Figure 2). During the WBLT, the opposite limb was placed behind the tested limb with 1 foot length,6 and the hands were allowed to
be placed on the wall for balance. Three practice trials were given, and 3 test trials were then performed for the WBLT. The mean value of the 3 trials was calculated for data analysis.
Statistical Analyses The assumption of normality of all variables was verified using the Kolmogorov–Smirnov test. The means and standard deviations of the normalized reach distances and ankle kinematics in each direction during the YBT-LQ and WBLT were determined. The correlation coefficient (r) and the proportion of variance (r2) explained by the relationship between results on the WBLT and both ankle dorsiflexion and the normalized reach distance in each direction on the YBT-LQ were examined using simple
Figure 2 — Weight-bearing-lunge test using (A) inclinometer and (B) tape measure. The arrow indicates distance from wall to great toe using tape measure.
Figure 1 — (A) Anterior, (B) posteromedial, and (C) posterolateral reach directions on the Lower Quarter Y-Balance Test using the Y-Balance test kit.
Weight-Bearing-Lunge Test and Y-Balance Test 65
linear regression. A correlation coefficient of £.39 was considered weak, .40–.69 moderate, and ≥.70 strong.10 Statistical analysis was performed using PASW statistics version 18.0 (SPSS, Inc, Chicago, IL, USA), and the alpha level was set at .05.
Results The assumption of normality was not violated in any data set (P > .05). Descriptive statistics for the normalized reach distance and ankle DF corresponding to each direction on the YBT-LQ and for the WBLT are shown in Table 1. In the anterior reach direction on the YBT-LQ, ankle DF showed a significant and strong correlation with the inclinometer measurement on the WBLT (r = .74, r2 = .55, P < .001) (Figure 3[A]), whereas there was only a moderate correlation between ankle DF and the tape measurement on the WBLT (r = .64, r2 = .40, P < .001) (Figure 3[B]). A moderate correlation was found between ankle DF during the posteromedial reach and the inclinometer measurement (r = .69, r2 = .48, P < .001), as well as the tape measurement (r = .64, r2 = .41, P < .001) on the WBLT. During the posterolateral reach on the YBT-LQ, there was a moderate correlation between
ankle DF and the inclinometer measurement of the WBLT (r = .46, r2 = .22, P = .010), but only a weak correlation was found between ankle DF and the tape measurement on the WBLT (r = .36, r2 = .13, P = .050). The normalized anterior reach distance on the YBT-LQ was significantly correlated with the inclinometer measurement (r = .68, r2 = .46, P < .001) and the tapemeasurement (r = .64, r2 = .41, P < .001) results of the WBLT. No significant correlations were found between the normalized reach distance during the posteromedial and posterolateral reaches on the YBT-LQ and both of the WBLT measurements (P > .05). The inclinometer measurement on the WBLT was significantly correlated with the tape measurement of the WBLT (r = .92, r2 = .84, P < .001).
Discussion Our primary findings revealed that the amount of explained variance in ankle DF during the anterior reach on the YBT-LQ was 15% greater when performing WBLT measurements using an inclinometer than with a tape measure, although the inclinometer measurements and tape measurements of the WBLT showed similar
Table 1 Normalized Reach Distance and Ankle Dorsiflexion in Each Direction on the Lower Quarter Y-Balance Test and Weight-Bearing-Lunge Test Variables
Mean ± SD
Normalized anterior reach distance on the Lower Quarter Y-Balance Test (%)
59.58 ± 5.26
Normalized posteromedial reach distance on the Lower Quarter Y-Balance Test (%)
100.44 ± 7.98
Normalized posterolateral reach distance on the Lower Quarter Y-Balance Test (%)
98.79 ± 10.00
Ankle dorsiflexion at anterior reach on the Lower Quarter Y-Balance Test (°)
39.29 ± 4.82
Ankle dorsiflexion at posteromedial reach on the Lower Quarter Y-Balance Test (°)
35.15 ± 5.96
Ankle dorsiflexion at posterolateral reach on the Lower Quarter Y-Balance Test (°)
36.13 ± 6.39
Weight-bearing-lunge test (cm)
13.48 ± 2.97
Weight-bearing-lunge test (°)
48.11 ± 5.20
Figure 3 — Simple linear regression between ankle dorsiflexion on the anterior reach portion of the Lower Quarter Y-Balance Test and the (A) inclinometer and (B) tape measurement of the weight-bearing-lunge test.
66 Kang et al
correlations with the normalized anterior reach distance on the YBT-LQ. In this study, ankle DF during anterior reach on the YBT-LQ was strongly correlated with the inclinometer measurement (r = .74, r2 = .55) but not with the tape measurement (r = .64, r2 = .40) of performance on the WBLT. Considering the strong relationship between these 2 measurement tools for the WBLT in the current study (r = .92, r2 = .84), it is interesting that there was a 15% difference between the 2 in the amount of explained variance in ankle DF during the anterior reach on the YBT-LQ. We considered that a potential limitation of the tape-measurement protocol of the WBLT influenced our results. Bennell et al5 showed that 1-cm tape measurement on the WBLT translated to a 3.6° inclinometer measurement, and findings by Konor et al7 suggested that a 1-cm tape measurement on the WBLT was approximately equal to a 4.1° inclinometer measurement. The differences in the findings of these previous studies may result from certain factors that influence the tape measurements of the WBLT. During the WBLT, the inclinometer measures the tibia inclination relative to vertical from the ground, which is not affected by other factors such as limb length or foot length. On the other hand, the tape measurement on the WBLT may have been influenced by limb or foot length because it was defined as the distance from the wall to the great toe. Therefore, it was inferred that the inclinometer measurement of the WBLT may be appropriate to acquire relatively constant ankle-DF PROM without any influences of foot or limb length. This may better explain the variance in ankle DF during the anterior reach on the YBT-LQ in relationship to the tape measurement of the WBLT. The current findings showed that the WBLT could explain 41% to 48% of the variance in ankle DF during the posteromedial reach, whereas it accounted for only 13% to 22% of the variance in ankle DF during the posterolateral reach of the YBT-LQ. The normalized posterolateral reach distance during the SEBT was reportedly greater in participants with a supinated foot than in participants with a pronated foot because of the greater limit on stability in the lateral direction.23 Conversely, it is inferred that the reach in the medial direction may require a foot-pronation movement to improve the limited stability in the medial direction. Previous studies have stated that motion of the full ankle–foot complex, including talocrural DF and subtalar pronation, is reflected in ankle DF as measured by the WBLT5,7; however, no attempt was made to restrict pronation of the foot during the WBLT in this study. Thus, we assume that the WBLT has a greater correlation with ankle DF during the posteromedial reach than during the posterolateral reach of the YBT-LQ due to foot pronation during WBLT. Although the amount of explained variance in ankle kinematics during the anterior reach of the YBT-LQ differed depending on the measurement tool used in the WBLT, similar correlations were found between the normalized anterior reach distance and both the inclinometer (r = .68, r2 = .46) and the tape measurements (r = .64, r2
= .41) on the WBLT. Furthermore, the normalized reach distance in the posteromedial and posterolateral directions was not significantly associated with WBLT (P > .05) results despite a significant correlation between the WBLT and ankle kinematics during the posterior reach (P < .05). These findings indicate that the normalized reach distance during dynamic postural-control tests can be influenced by other factors, as well as by ankle kinematics. Previous findings by Robinson and Gribble20 showed that a combination of hip and knee flexion could explain 78% of the variance in the normalized anterior reach distance and that hip flexion could account for 88% and 94% of variance in the normalized reach distance in the posteromedial and posterolateral directions, respectively, during the SEBT. In addition, it was found that hip-extensor and -abductor strength were significantly correlated with the normalized posteromedial and posterolateral reach distances on the SEBT.24 Based on these previous findings, the kinematics of other joints and/or the strength of the lower extremity influences performance on the YBT-LQ, leading to significant and similar correlations between the normalized reach distance and the 2 measurement tools of the WBLT in the anterior direction only, and not the posteromedial or posterolateral direction on the YBT-LQ.
Limitations Some limitations should be considered in this study. First, our findings cannot be generalized to injured patients because all participants were physically active and uninjured. Second, we did not suggest a technique for standardization of tape measurement in the WBLT. A future study should establish standardization methods to minimize the influence of limb and foot length on tape measurement for the WBLT. In addition, the relationship between limb length and reach distance during the YBT-LQ needs to be considered in the future study. Finally, we did not include data of other joint kinematics, because our preliminary purpose was to demonstrate the relationship between the WBLT and ankle kinematics and performance on the YBT-LQ.
Clinical Implications We demonstrated that ankle-DF PROM in the weightbearing condition such as the WBLT is significantly correlated with ankle kinematics and performance on the dynamic postural-control tests. These findings will provide researchers and clinicians with useful information supporting the assumption that measurement of ankle-DF PROM in weight-bearing may reflect functional requirements of ankle. In addition, most previous studies preferred tape measurements of the WBLT6,10 despite validity issues due to length of limb and foot.5 Based on the current findings, clinicians should consider the influences of potential factors on the distance value when assessing WBLT using a tape measure, although tape measurement of WBLT has been reported as a reliable method. Furthermore, WBLT needs to be measured in
Weight-Bearing-Lunge Test and Y-Balance Test 67
individuals with poor dynamic posture control for identifying possible causes and determining interventions to improve dynamic postural control.
Conclusions Performance on the WBLT was significantly correlated with ankle kinematics and performance on the YBT-LQ. These findings support the notion that measurement of ankle-DF PROM under a weight-bearing condition may be indicative of the functional requirements of the ankle during weight-bearing activities. In particular, measurement of the WBLT using an inclinometer can be a convenient means of predicting ankle kinematics during dynamic postural-control tests. Clinicians should also consider the importance of ankle-DF PROM under the weight-bearing condition when designing training programs to improve dynamic postural control.
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