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1 One-Arm Hop Test: Reliability and Effects of Arm Dominance Susan A. Falsone, PT, ATC, MS 1 Michael T. Gross, PT, PhD 2 Kevin M. Guskiewicz, ATC, PhD 3 Robert A. Schneider, PT, ATC, MS 4 Journal of Orthopaedic & Sports Physical Therapy Study Design: Test-retest reliability analysis and 2-factor ANOVA contrast of athletic group and limb dominance. Objectives: To determine the reliability of the one-arm hop test and the effects of upper-extremity dominance on test scores for 2 athletic groups. Background: Limited information is available regarding functional performance tests of the upper extremity that involve axial loading. Methods and Measures: Thirteen male collegiate wrestlers (mean age, 20.3 ± 1.6 years) and 13 male collegiate football players (mean age, 20.0 ± 1.7 years) without upper-extremity pathology participated in the study. Subjects were trained to perform the one-arm hop test, starting from a one-arm push-up position and then hopping as quickly as possible onto and off of a 10.2-cm platform 5 times. Subjects returned to the test site 1 to 2 days later and were timed for 2 trials of the one-arm hop test for each upper extremity. Results: Within-session ICC 2,1 reliability values were 0.78 for the football players and 0.81 for the wrestlers. Mean absolute differences between trials were 0.64 seconds for the football players and 0.47 seconds for the wrestlers. Trial 2 performance times were significantly faster than trial 1 times for the wrestlers. Although performance time for the nondominant side was on average 4.4% slower than that of the dominant side, performance times for the dominant side were not significantly different from those of the nondominant upper extremities. Conclusions: The results provide preliminary evidence that the one-arm hop test may be a reliable upper-extremity functional performance test with sufficient training of the subject. Uninjured upper-extremity performance for the one-arm hop test may be useful as a basis for comparing performance of an injured contralateral upper extremity. J Orthop Sports Phys Ther 2002;32: Key Words: functional performance test, upper extremity 1 Physical therapist, Athletes Performance, Tempe, AZ. 2 Professor, Program in Human Movement Science, Division of Physical Therapy, University of North Carolina at Chapel Hill, Chapel Hill, NC. 3 Assistant professor, Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, NC 4 Physical therapist and athletic trainer, Student Health Service, University of North Carolina at Chapel Hill, Chapel Hill, NC. Ms. Falsone completed this research in partial fulfillment for her Master s of Science degree in the Program in Human Movement Science at the University of North Carolina at Chapel Hill. Approved by the Committee for the Protection of the Rights of Human Subjects at the University of North Carolina at Chapel Hill. Send correspondence to Michael T. Gross, CB #7135, University of North Carolina at Chapel Hill, Chapel Hill, NC mtgross@med.unc.edu Recently, the effects of weight-bearing exercises for upperextremity joint instability have been under examination. 1,8,9,15,25,27 Sports such as gymnastics, football, wrestling, and rowing involve an axial load imposed on the hands. For sports such as these, it is difficult to determine when athletes are ready for sport-specific drills following injury and prior to returning to competition. Many conventional physical examination techniques are performed without imposing axial loads on the hands, such as range of motion, manual muscle testing, joint position tests, and isokinetic testing of shoulder joint musculature. For the athlete who competes with axial loads imposed on the upper extremities, these examination techniques may not provide information sufficiently accurate to determine return-toplay status. Athletes such as wrestlers, gymnasts, and football players may benefit from performance testing that involves upperextremity axial loading. Dynamic functional performance testing using axial loading evaluates the patient in functional situations under varying degrees of stress, allowing a clinician to measure the patient s performance objectively Journal of Orthopaedic & Sports Physical Therapy

2 Functional performance testing has been widely advocated for clinical assessments that follow lowerextremity injuries. 4,5,8,14,16,20 Although these tests have been described by many investigators, few authors have reported reliability for their measurements. 2 4,17,18,20 22,25,27 There is limited information on functional performance testing of the upper extremity. Wilson et al 29 have described a functional test for the hemiparetic upper extremity that involves activities of daily living. Ubinger et al 25 used a FASTEX device (Cybex, Ronkonkoma, NY) to test the ability of physically active subjects to balance in a single-arm push-up position. Neither group of investigators reported the reliability of their test results. 25,29 These studies did not involve tasks that required forceful propulsive axial loading of the upper extremity (ie, pushing away from a support surface or other object), or tasks that required strenuous deceleration loading of the upper extremity (ie, falling onto an outstretched upper extremity). We were unable to identify any literature, other than the study by Ubinger et al, 25 that describes a weightbearing functional performance test for the upper extremity. The one-arm hop test in this research study is a functional performance test designed by the University of North Carolina Sports Medicine staff for preseason screening examinations. The one-arm hop test requires the athlete to be in a one-arm push-up position on the floor. The athlete then uses his arm to hop onto a 10.2-cm step and back onto the floor. The time required to perform 5 repetitions of this movement as quickly as possible is recorded. The one-arm hop test requires concentric and eccentric muscle strength and control while the distal portion of the upper extremity has a considerable external load placed upon it. Similar demands are placed upon the upper extremities of wrestlers and football players while they participate in their sport. The test was developed to simulate functional axial-loading movements of the upper extremity and to assist in making return-to-play decisions. Many unanswered questions exist regarding the one-arm hop test. The reliability of the test and the effects of upper-extremity dominance on test performance have not been documented. Clinicians often use test performance of the contralateral extremity as a basis for comparing test results for the upper extremity concerned (eg, undergoing rehabilitation). Such comparisons for the one-arm hop test would be valid if test scores between dominant and nondominant upper extremities were similar. The purpose of this study was to assess the reliability of the one-arm hop test and to determine the effects of upper-extremity dominance on test performance for 2 athletic groups. METHODS Subjects Thirteen wrestlers and 13 football players (4 linebackers, 4 offensive linemen, and 5 defensive linemen) without current upper-extremity pathology were tested. An additional football player enrolled in the study did not meet the criteria for acceptable testing (described later). Subjects reported through a written questionnaire that they had no upperextremity injury currently limiting their athletic participation and no history of upper-extremity trauma or injury having limited their activity for more than 2 consecutive days during a period of 6 weeks prior to testing. Each subject signed a statement of informed consent prior to participation, and the study was approved by the Committee for the Protection of the Rights of Human Subjects at the University of North Carolina at Chapel Hill. Testing Procedure Testing procedures took place over 2 days for each subject. On the first day, subjects completed a questionnaire pertaining to past and present upperextremity injuries and current athletic participation status. Descriptive data measured and recorded for all subjects included age, height, weight, upperextremity dominance (defined as the hand reported to be preferred for throwing a ball), percentage of body fat, sport, and sport position. Skinfold thickness was measured at the chest, abdomen, and thigh using Lange skinfold calipers (Cambridge Medical Instruments, Ossining, NY). 24 Chest measurements were taken on a diagonal fold halfway between the axilla and the nipple. Abdomen measurements were taken on a vertical fold 2.5 cm to the right of the umbilicus. The thigh measurement was taken using a vertical fold on the front of the thigh, midway between the hip and the knee. Percentage of body fat estimates were then determined using tabled data for men under 40 years of age. 12 The subjects warmed up on the Schwinn Air-Dyne (Boulder, CO) for 4 minutes at 30 revolutions per minute (RPM), using only their upper extremities, and then performed 10 standard 2-hand push-ups. A 5-minute rest period followed. Each subject then performed the procedures to get familiar with the onearm hop test. The subject first watched an instructional video depicting the one-arm hop test. After instruction, subjects practiced the one-arm hop test for each upper extremity. Verbal cues were given during this practice session if necessary. Each subject practiced the one-arm hop test by assuming a onearm push-up position with his back flat, his feet and shoulders apart, and his weight-bearing upper ex- RESEARCH REPORT J Orthop Sports Phys Ther Volume 32 Number 3 March

3 tremity positioned perpendicular to the floor (Figure 1). The subject placed his non weight-bearing hand on the posterior aspect of the low back. A 10.2-cm step ( The Step, Sports Step Group, Marietta, GA) was placed immediately lateral to the subject s test hand (Figure 1). The step has a rubber upper surface and the test was performed on a carpeted floor to help prevent slipping. After the subject was in the proper start position, the investigator said, Ready, set, go, to signal the beginning of the trial. The subject used the weight-bearing arm to hop onto the step and landed on the rubber portion of the step with the entire hand. The subject then used the weight-bearing arm to hop off of the step and return his hand to the start position next to the step. Subjects repeated this movement 5 times as quickly as possible. If the subject performed the test with improper technique, he rested for 1 minute, and then performed another practice test. An acceptable test was defined as a test in which the subject fully hopped onto the rubber portion of the step, did not use the other hand, did not touch down with a knee, and kept his back flat and his feet in the same position. Subjects continued to practice the test until they demonstrated 1 trial using acceptable technique. After a 1-minute rest, the same maneuver was then performed with the contralateral upper extremity. The order for practicing dominant and nondominant upper extremities was randomized. The investigators did not record the number of practice trials needed by each subject to demonstrate proper technique. Each subject returned 1 2 days after the first test day for data collection for the one-arm hop test. Subjects performed the same 4-minute warm-up on the Schwinn Air-Dyne at 30 RPM, followed by 10 standard push-ups. The subject again watched the instructional video depicting the one-arm hop test. FIGURE 1. Anterior view of subject positioned for the one-arm hop test. Subjects performed the one-arm hop test with their dominant and nondominant upper extremities in random order, with a 1-minute rest between the testing for each upper extremity. Timing with a standard stopwatch began when the subject s hand left the floor on the first hop and stopped when the hand landed back onto the floor after the fifth hop. The time taken to perform the test for each upper extremity was recorded to the nearest one-hundredth of a second. The subject rested for 5 minutes, and then performed the test a second time using the same order of dominant-nondominant upperextremity testing as the first testing sequence, with a 1-minute rest between the testing for each upper extremity. Data from trial 2 were compared with trial 1 data to assess test-retest reliability. Only data from the first trials were used to assess the effects of arm dominance on test performance. This reflects the type of single-trial testing that might occur in the clinic. Therefore, each subject was represented only once in the data analysis. If a subject performed a trial with any of the previously identified performance errors, he was given a 5-minute rest period and another trial. If the subject could not complete a successful trial in 2 attempts, he was disqualified from the study. If a subject reported pain during the test or immediately following testing procedures, his data were excluded from the study. Data Analysis Independent t-tests were used to assess differences between the two groups with regard to age, height, mass, and percentage of body fat. An intraclass correlation coefficient (ICC 2,1 ) 23 and mean absolute difference values were computed to assess test-retest reliability of the two trials of the one-arm hop test for each subject group. Absolute difference values were also computed as a percentage difference between trials: trial 1 trial 2 trial 1 100% Absolute differences were normalized as a percentage of the trial 1 data, which were used to assess the effects of upper-extremity dominance. Differences between the two trials for each subject group also were assessed using paired t-tests. A 2-way ANOVA with repeated measures on 1 factor (subject s upper extremity) was conducted to assess the effects of upper-extremity dominance on one-arm hop test scores for each subject group. An alpha level of 0.05 was used for the t-tests and the ANOVA. Differences between dominant-upper-extremity performance and nondominant-upper-extremity performance were also assessed by computing differences 100 J Orthop Sports Phys Ther Volume 32 Number 3 March 2002

4 between limb performance, and were expressed as a percentage of dominant-upper-extremity performance: dominant nondominant 100% dominant All analyses were conducted using SAS Statistical Software (Cary, NC). RESULTS Descriptive statistics for the two subject groups appear in the Table. The two subject groups were similar with regard to age and percentage of body fat. The football players, however, were significantly taller and had significantly more mass than the wrestlers. Eleven of the wrestlers were right-upper-extremity dominant and 2 were left-upper-extremity dominant. Eleven of the football players were right-upperextremity dominant and 2 were left-upper-extremity dominant. All of the wrestlers performed the onearm hop test correctly on the second test day. Three of the football players performed the one-arm hop test with errors on their first attempt and had to repeat the first data collection trial. One football player experienced shoulder pain when he performed the one-arm hop test and was dismissed from the study. The test-retest reliability results for the two trials of the one-arm hop test were ICC 2,1 = 0.81 for the wrestlers, and ICC 2,1 = 0.78 for the football players. The mean absolute difference between the two test trials was seconds for the wrestlers, and seconds for the football players. These mean values corresponded to an average of 9% change in performance for the wrestlers, and an average of 11% change in performance for the football players. Descriptive statistics for the first and second trials for each subject group appear in Figure 2. Paired t-test results indicate that the wrestlers mean trial 1 time (4.72 ± 1.10 seconds) for the one-arm hop test was significantly greater than (t = 4.31, df = 25, P 0.05) the mean trial 2 time (4.29 ± 0.87 seconds). The football players mean trial 1 time (5.69 ± 1.31 seconds) for the one-arm hop test was not significantly different (t = 1.37, df = 25) from their mean trial 2 time (5.44 ± 1.49 seconds). Descriptive statistics for one-arm hop test scores by subject group and upper-extremity dominance are graphically represented in Figure 3. The ANOVA results indicate that subject group and upper-extremity dominance did not interact significantly to affect one-arm hop test scores (F = 0.63; df = 1,24). Onearm hop test scores did not differ significantly between dominant and nondominant upper extremities (F = 1.92; df = 1,24). Performance time for the nondominant side was on average 4.4% slower than for the dominant side. Differences between dominant and nondominant upper extremities ranged from the nondominant upper extremity being 32.8% slower to 23.8% faster than the dominant upper extremity. The 95% confidence interval results indicate that clinicians might expect nondominant-upperextremity performance to range from 1.1% faster to 9.8% slower than dominant-upper-extremity performance. DISCUSSION TABLE. Descriptive statistics for subject groups (values are means standard deviations). The range of one-arm hop test performance for the wrestlers (2.95 to 7.07 seconds) and the football players (3.24 to 9.95 seconds) represents a fairly restricted range of scores. Additionally, a manual stopwatch was used to record the time taken by subjects to perform the one-arm hop test. For the two testretest trials, the stopwatch was started and stopped a total of 4 times. Considering the human error involved in manipulating the stopwatch and the restricted range of measurements, the ICC and the absolute difference values compare favorably with previous reports of reliability for lower-extremity functional tests. 7,10,11,19 Descriptive statistics for the two trials of the test and the paired t-tests, however, indicate that for the wrestlers, times for trial 2 were significantly faster than those for trial 1. On average, times for trial 2 were 0.42 seconds less than times for trial 1. This difference corresponds to an average change in performance of 9% for the wrestlers and 11% for the football players. We did not record the number of practice trials performed by each subject. The contrast between first- and second-trial performance times for the subjects, however, suggests that performance times may not have stabilized. Investigators Athletic Groups Age (y) Height (cm) # Mass (kg) Body Fat (%) Wrestlers (n = 13) Football Players (n = 13) # Football players significantly taller than wrestlers (t = 9.90, P 0.05) Mass of football players significantly greater than wrestlers mass (t = 7.76, P 0.05) RESEARCH REPORT J Orthop Sports Phys Ther Volume 32 Number 3 March

5 One-Arm Hop Test Time (sec) Wrestlers Athlete Group Football Players Trial 1 Trial 2 FIGURE 2. Mean one-arm hop test-retest results for two trials performed by wrestlers and football players. Trial 1 and trial 2 times did not differ significantly for the football players, but trial 2 times were significantly faster (P 0.05) than trial 1 times for the wrestlers. One-Arm Hop Test Time (sec) Wrestlers Football Players Athlete Group Dominant Nondominant FIGURE 3. Mean one-arm hop test results for dominant and nondominant upper extremities of wrestlers and football players. Performance times for the dominant upper extremities were not significantly different than times for the nondominant upper extremities. and clinicians who use the one-arm hop test may wish to have subjects or patients practice the task until a level of consistency has been demonstrated (eg, with a maximum difference between successive scores of no more than 5%). The second major objective of this study was to determine the effects of upper-extremity dominance on one-arm hop test performance. The ANOVA results showed no significant difference in one-arm hop test scores attributable to upper-extremity dominance. Conclusions regarding the effects of limb dominance must be tempered by the possibility that performance times may not have stabilized. The descriptive statistics, however, indicate that nondominant-upper-extremity performance times were on average only 4.4% slower than dominantupper-extremity performance times. The confidence interval results also show that there were comparable performance times between dominant- and nondominant-upper-extremity performance for the one-arm hop test. A clinical application for results of the effects of limb dominance may be the use of test performance of an uninjured upper extremity for postinjury rehabilitation contrasts. If no preinjury data exist for the injured upper extremity, clinicians may use the uninjured extremity as a baseline for performance. The range of differences between dominant- and nondominant-upper-extremity performance does, however, include outliers in both directions, as dominant-limb performance has been observed to be both appreciably faster and slower than nondominant-limb performance. Clinicians might consider, therefore, gathering test data for both limbs during preseason screening procedures and at regular intervals during the sport season. The one-arm hop test may not fully represent all upper-extremity axial-loading activities for athletes who participate in sports that require this type of upper-extremity function. This study involved an initial effort to standardize and assess the reliability of the one-arm hop test. An initial practice session may be helpful to familiarize athletes with the proper procedure for performing the test. Future research might be directed at analyzing the amount of practice needed to obtain more stable observations of the test. The one-arm hop test in a preseason screening might also serve the dual purpose of teaching athletes this functional performance test, while providing preinjury baseline scores for the test. In the present study, ensuring proper performance of the one-arm hop test was important. The video helped to standardize the instructions given to each subject and to provide visual cues for the test requirements. In all cases, verbal feedback was necessary to remind the subject to keep his feet shoulder width apart and his back flat. Additional motion analysis of this movement may be helpful to identify common substitutions and ways to correct them. Finally, the subjects in this study were considered healthy, collegiate varsity athletes with no significant upper-extremity pathology at the time of testing. Threats to the external validity of the results include sample representation of the population, sample size, and the extent to which the test simulates axial loads 102 J Orthop Sports Phys Ther Volume 32 Number 3 March 2002

6 imposed on the upper extremity during functional activities. Fitness levels of these subjects also varied, and may be different than high school, college, or professional athletes. Future research might assess the validity of this test for subjects with functional limitations. CONCLUSION The results of this preliminary study indicate that with sufficient training of the subject, the one-arm hop test may be a reliable upper-extremity performance test. The results also show that nondominantupper-extremity performance averaged 4.4% slower than dominant-upper-extremity performance. Clinicians, therefore, may be able to use this test to compare a patient s uninjured-upper-extremity test results to the patient s injured-upper-extremity test results. ACKNOWLEDGMENTS We thank Philip L. Witt, PT, PhD, for his critical review of the research proposal and manuscript; and William B. Ware, PhD, for his excellent consultation on the statistical analyses. REFERENCES 1. 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