Test-Retest Reliability of the Lateral Step-up Test in Young Adult Healthy Subjects

Transcription

1 Test-Retest Reliability of the Lateral Step-up Test in Young Adult Healthy Subjects Capt Michael Ross, MSEd, PT' linicians often assess muscular performance in order to determine an individual's level of function or evaluate progress made during a training or rehabilitation program. Assessment of lower extremity muscular performance has traditionally been performed in the open kinetic chain ( 1,7,9,20). Recently, however, closed kinetic chain assessment has been advocated, since it may offer a more effective means of determining an individual's level of function (10,11, 15,16,19,21). The step test is an example of a closed kinetic chain test that has been utilized to assess lower extremity muscular performance (17,21). There are several proposed benefits that closed kinetic chain assessment may offer compared with open kinetic chain assessment. Since many lower extremity training and rehabilitation programs have recently centered around closed kinetic chain exercises (4,13,15,2l), closed kinetic chain rather than open kinetic chain assessment, based upon the specificity of training principle (14), may be better suited to detect actual improvements in lower extremity performance. During movements in the closed kinetic chain, compression of the tibiofemoral joint and cocontraction of the quadriceps and hamstring musculature occurs, which may assist in decreasing anterior tibia1 translation and subsequent strain on the anterior cruciate ligament (1 2,14). Additionally, assessment in the closed kinetic chain will be more apt to pro- The lateral stepup test is ofien utilized by clinicians to assess lower extremity performance capabilities. Reliability of the lateral stepup test, however, is not available. Therefore, the purpose of this study was to determine the test-retest reliability of a 15-sec and a 50-repetition lateral step up test on a.15-m (6-inch) and.2-m (8-inch) step. For each of the 15-sec lateral stepup tests, subjects were asked to perform as many repetitions as possible during the 15-sec time frame, while for each of the 50-repetition lateral stepup tests, subjects were asked to perform 50 repetitions as quickly as possible. Eighteen healthy subjects were studied. Data were analyzed through a repeated measures analysis of variance, intraclass correlation coefficients (ICC) (2,1 ), and standard errors of measurement. The ICC values were.90 and.94 for the.15-m and.2-m 15-sec lateral stepup tests and.91 and.96 for the.15-m and.2-m 50-repetition lateral step-up tests, respectively, revealing test-retest reliability to be high for each of the tests. Significant differences, however, were noted between the testing days for each of the 50-repetition lateral stepup tests, indicating that the measures may not be stable. No significant differences were seen between testing days for either of the 15-sec lateral stepup tests. While the results support the use of each of the 15-sec lateral stepup tests as reliable, stable measures of lower extremity performance, caution should be used when interpreting the results of either of the 50-repetition lateral step-up tests if used as demonstrated in this study. Key Words: lateral step-up test, lower extremity, reliability ' Chief, Department of Physical Therapy, 39th Medical Croup, lncirlik Air Base, Turkey. At the time of this study, Captain Ross was a Staff Physical Therapist, Department of Physical Therapy, 74th Medical Croup, Wright-Patterson Air Force Base, OH. Address for correspondence: 39 MDG USAFE, PSC 94, Box 379, APO AE The opinions expressed herein are those of the author and do not necessarily reflect the opinions of the Department of Defense, the United States Air Force, or other federal agencies. mote functional movements that take an individual's strength, coordination, and balance into account (19). Recently, Worrell et al (21) studied the effects of an aggressive lateral stepup exercise protocol on isokinetic quadriceps peak torque and closed kinetic chain performance as measured by two hop tests, the leg press, and the lateral stepup test. They suggested that the training protocol provided sufficient overload to improve lower extremity performance as measured by the closed kinetic chain tests. Isokinetic testing, however, was unable to detect improvements in quadriceps performance that may have resulted from the training protocol. They concluded that a learning effect occurred with the closed kinetic chain training protocol that caused a beneficial carryover to the closed kinetic chain tests. Furthermore, the lateral stepup test has been recommended by Reynolds et al (15) and Rosenthal et al (17) as a clinical measure of lower extremity performance following a training protocol that emphasizes closed kinetic chain activities. Two ways in which the lateral stepup test may be utilized to assess lower extremity performance are by counting the number of repetitions performed at a specific step height over a specified period of time and Volume 25 Number 2 February 1997 JOSPT

2 TABLE 1. Descriptive data for the lateral step-up tests. by assessing the time necessary to complete a specified number of repetitions at a specific step height (6). Test-retest reliability data for either lateral step-up test, however, have not been able to be located. Therefore, the purpose of this study was to determine the test-retest reliability of a 15-sec and a 50-repetition lateral step-up test on a.15m (Cinch) and.2-m (&inch) step. METHODS Subjects Eighteen healthy subjects (14 males and four females) participated in this study (age = years; height = cm; weight = kg). Each subject signed a consent form a p proved by the Department of Clinical Investigation, 74th Medical Group, Wright-Patterson Air Force Base, OH. Subjects with a condition that prevented participation in vigorous physical activity or a history of lower extremity dysfunction or pain were excluded from participation in this study. Procedure All subjects were familiarized with the testing procedures of this study 7 days prior to their initial testing. During the familiarization session, subjects performed each of the testing procedures. For each lateral step-up test, the subjects were asked to stand with the extremity being tested on the step with their feet parallel and shoulder width apart. The hip and knee of the extremity being tested was then moved into full extension (extension phase), followed by flexion until the heel of the extremity not being tested touched the floor (flexion phase). To assist in the understanding of proper lateral step-up test technique, subjects were made aware of knee hyperextension, 10" of knee flexion through the use of a standard goniometer (Orthopedic Equipment Co., Bourbon, IN), and horizontal pelvic positioning. Appropriate lateral step-up test technique, therefore, was defined as achieving a position within 10" of knee extension for the tested extremity during the extension phase of the test while avoiding knee hyperextension, as well as keeping hands on hips and maintaining the pelvis in a horizontal position and the foot of the nontested extremity in a dorsiflexed position throughout the test. Repetitions were counted each time the heel of the extremity not being tested touched the floor. Repetitions were not counted if, during the flexion phase, any other part of the foot except the heel touched the floor. Following the command, "Ready, set, go," subjects started each test and timing began on a stopwatch accurate to.o1 sec. For the 15-sec lateral step-up tests, subjects were asked to perform as many repetitions as possible on each step during the 15-sec time frame. For the 50-repetition lateral step-up tests, subjects were asked to perform 50 repetitions on each step as quickly as possible. The extremities were randomly tested as determined by a coin toss. Both extremities were tested with the 15-sec lateral step-up tests followed by the 50-repetitifin lateral step-up tests. I the.15m step step for each allowed to pertitions per ex- 31 testing on the Subjects were lowing the practice repetitions and between tests. The subjects were tested during two sessions administered 4 days apart. Data Analysis Data gathered from both extremities were analyzed for each subject. An independent t test was performed to determine if significant differences existed between dominant and nondominant extremities for each of the four lateral step-up tests. Test-retest reliability for the test trials was determined through intraclass correlation coefficients (ICC) (2,l) (18). The ICC was based upon a repeated measures analysis of variance (ANOVA), which was done to compare the testretest trials for each of the four lateral step-up tests. In order to assess the amount of error associated with repeated measurements, the standard error of measurement (SEM) (SEM = SD m) was calculated. Probability values (P), determined from the repeated measures ANOVA, indicated whether significant differences existed between the test trials for each of the four lateral step-up tests. For the purpose of this study, p values less than or equal to.05 are indicative of significant differences between the test trials. RESULTS Means and standard deviations for each of the lateral step-up tests are presented in Table 1. Since results of the t test revealed no significant differences between the dominant and nondominant extremities for each of the tests, the data were pooled for further analysis. The results of the repeated measures ANOVA on the four lateral step-up tests are presented in Tables 2-5. JOSPT. Volume 25 Number 2 February 1997

3 Between subjects Within subjects Between trials I* Residual Total * No significant diiierence (p >.05) noted between test trials. TABLE 2. Repeated measures analysis of variance of. 15-m 15-sec lateral step-up test. The ICC and SEM for each of the lateral step-up tests are presented in Table 6. The ICC and SEM were.90 and 1.14 repetitions for the.15m 15sec lateral step-up test and.94 and.76 repetitions for the.2-m lhec lateral step-up test, respectively. No significant differences were noted between the test trials for either of the 15-sec lateral step-up tests (p >.05). The ICC and SEM were.91 and 1.58 sec for the.15m 50-repetition lateral step-up test and.96 and 1.32 sec for the.2-m 50-repetition lateral step-up test, respectively. Significant differences were noted between the test trials for each of the 50-repetition lateral step-up tests (p <.05). DISCUSSION High reliability has been demonstrated by an ICC >.75 (5). Based upon this scale, each of the lateral step-up tests as demonstrated in this study were shown to be highly reliable. For the.15m and.2-m 15sec lateral step-up tests, the absolute differences between the testing trials were.58 and.47 repetitions, respectively. Since the absolute differences and SEM for each of the 15-sec lateral step-up tests were small and no significant differences existed between the testing trials, it appears that these tests represent stable measures and may be used clinically. Furthermore, the results of this study suggest that following a familiarization session, one trial of the.15m and.2-m 15sec lateral step-up test on each testing day will provide a reliable, stable measure. By implementing only one trial of the lateral step-up test during each testing ses- sion, the effects of fatigue that may be associated with multiple tests are avoided. Significant differences were noted for the.15m and.2-m 50-repetition lateral step-up tests, even though the ICC values (.91 and.96, respectively) were acceptable and a b solute differences (1.64 sec and 1.57 sec, respectively) between testing days were small. The fact that the scores were improving and significant differences existed between test trials indicates that the measures were not stable and a learning effect took place (3). Therefore, the clinician is rec- ommended to use caution when interpreting the results of the 50-repetition lateral step-up tests if used as described in this study. The implementation of additional trials may eventually allow a stable measure to be reached. However, if multiple trials are performed during the same testing session, adequate recovery time should be provided to enable the individual to return to a physiological state that existed prior to the previous trial (8). The 15-sec lateral step-up tests assessed in this study evaluated an individual's short-term performance capabilities. The 50-repetition lateral step-up tests assessed an individual's ability to perform for a longer duration than the 15-sec lateral step-up tests. The 50-repetition lateral step-up tests were inherently more difficult than the 15sec lateral step-up tests since subjects were required to perform for a longer period of time. If subjects suspected increased difficulty Between subjects Within subjects Between trials * Residual Total * No signiiicant diiierence (p >.05) noted between test trials. TABLE 3. Repeated measures analysis of variance of.2-m 15-sec lateral step-up test. Between subjects Within subjects Between trials ,001* Residual Total * Significant dirierence (p <.05) noted between test trials. TABLE 4. Repeated measures analysis of variance of. 15-m 50-rep lateral step-up test. Between subjects Within subjects Between trials * Residual Total * Significant diference (p <.05) noted between test trials. TABLE 5. Repeated measures analysis of variance of.2-m 50-rep lateral step-up test. Volume 25 Number 2 Februa~ 1997 JOSPT

4 Lateral StepUp Test ICC SEM.15-rn 15-sec reps.2-m 1 Esec reps.15-rn 50-rep* sec.2-rn 50-rep* sec * Significant differences (p <.05) noted between test trials. ICC = lntraclass correlation coefficient (2,1). SEM = Standard error of measurement. TABLE 6. Test-retest reliability data for the lateral step-up tests. with the 50-repetition lateral step-up tests, they may have not given full effort during the familiarization session or first test trial, since their main goal may have been to simply complete the test. By the time of the second test trial, the subjects may have been more accustomed to the test and may have been able to give full effort, which subsequently resulted in the improvement and significant differences seen during the second test trial. Recently, Booher et al (3) determined that the test-retest reliability for three single-leg hop tests (hop for time, hop for distance, agility hop) was acceptable (ICC values ranged from.77 to.97). Significant differences, however, were seen between testing days for the agility hop, which was the most difficult of the three tests. The results of this study appear to be in agreement with those of Booher et al, in that scores improved and significant differences were seen between testing days for the more difficult tests. Since it may be difficult to determine what actually caused the improvement seen in the tests, the clinician should use caution when drawing conclusions about an individual's physical performance capabilities from the test-retest results of higher level unilateral functional tests. The SEM can be used to determine the range in which a subject's "true score" could be expected to lie when the amount of error associated with repeated measures is considered. For example, we can be 95% confident that the "true score" for subjects performing the.15m and.2-m 15sec JOSPT. Volume 25 Nr~mher 2 0 Fehn~ary IW7 lateral step-up test lies within f 2 SEM (22 repetitions). Thus, a change in a subject's performance of greater than two repetitions on either of the 15-sec lateral step-up tests most likely represent5 a real change that may not be attributed to measurement error. The majority of unilateral functional tests discussed in the literature (ie., hop tests, jump tests) places a high demand on the musculoskeletal system. For this reason, they are usually not performed early in the rehabilitation period or indicated for nonathletic individuals (4,21). Furthermore, the ability of unilateral functional tests to predict an individual's functional outcome has recently been questioned (2). While the lateral step-up tests as described in this study provide a reliable measure of lower extremity performance that may be indicated for nonathletic individuals and be used early in the rehabilitation period, the ability of the lateral step-up tests to predict functional outcomes and detect functional deficiencies must be determined. Additionally, it is recommended that lateral step-up tests be implemented with caution when assessing patients that complain of increased knee pain during stair climbing and squatting activities. One limitation of this studv is that the time frame between the testretest sessions was only 4 days apart. Therefore, the results of this study may not be generalized to longer time periods, such as those associated with training athletes or treating patients. Additionally, since the subjects in this study were without lower extremity pathology, the results may not be generalizable to patient populations. Despite these limitations, the lateral step-up tests as demonstrated in this study may be used as part of a screening examination for noninjured young adults. Further research is necessary to determine the reliability and ability of the lateral step-up test to detect functional deficiencies in patients recovering from lower extremity surgery or injury. However, future reliability studies that examine the lateral step-up test and other measures of lower extremity performance should use time frames of 4-6 weeks between the test-retest sessions, as these would better evaluate reliability as it is hoped to be used in the field/ clinical setting. A follow-up studv is also indicated to determine the effect of multiple within-session trials and subsequent fatigue on the reliability and stability of the 50-repetition lateral step-up tests. CONCLUSION This study demonstrates high reliability for the.15m and.2-m 15-sec and 50-repetition lateral step-up tests. Significant differences, however, existed between the testing days for each of the 50-repetition lateral step-up tests, indicating that the measures may not be stable. Therefore, while the.15m and.2-m 15sec lateral step-up tests may be recommended for clinical usage. caution should be used when interpreting the results of the.15m and.2-m 50-repetition lateral step-up tests. JOSPT ACKNOWLEDGMENT The author wishes to acknowledge Dan Cipriani, MEd, PT, for his assistance with the design of this study, and Ted Worrell, EdD, PT, SCS, ATC, FACSM, and Alisa Hurtle, MAPT, for their assistance with data interpretation and manuscript preparation. REFERENCES I. Antich TI, Brewster CE: Rehabilitation of the nonconstructed anterior cruciate ligament-deficient knee. Clin Sports Med 7: , Barber S, Noyes FR, Mangine RE, McCloskey ]W, Hartman W: Quantitative assessment of functional limitations in normal and anterior cruciate-deficient knees. Clin Orthop 225: , Booher LD, Hench KM, Worrell TW,

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