J. STEPHEN GUFFEY, MEd, PT? DARYL R. GUFFEY, BS3

The Reliability of Selected Measures of Muscular Performance in Knee Flexion and Extension Using the Hydra-Fitness Omni Tron Total Power Unit: A Pilot Study' J. STEPHEN GUFFEY, MEd, PT? DARYL R. GUFFEY, BS3 Thirty-one subjects were included in this investigation (19 female and 12 male). The subjects ranged in age from 79-38 years with a mean age of 25 years. The subjects performed a maximal strength test of knee flexion and extension using the Omni Tron Total Power Unit employing one resistance setting. Values were obtained for eight muscular performance indicators. An identical strength test was repeated the following day. Reliability coefficients were calculated using the two sets of data. Pearson product coefficients for the eight performance indicators ranged from 0.85 to 0.97. Values from test 1 were also compared to test 2 values for significant difference using the student t-test. No significant difference was found (p < 0.05). The authors concluded that, based on the data obtained in this pilot study, the Omni Tron Total Power Unit holds the potential to produce reliable data relating to muscular performance. The practice of physical therapy is rapidly evolving. In some areas of practice, highly sophisticated, computer interfaced equipment is routinely utilized. Specialized testing of motor function and joint range of motion is commonly performed in many of even the smallest clinics and departments. The use of isokinetic devices for testing and rehabilitation, which began approximately 15-20 years ago (4) has blossomed into quite a growth industry for medical equipment manufacturers. Competition may lead to improved design and function. Furthermore, price can be 'This research was supported in part by an equipment grant from Hydra-Fitness Industries. Inc.. Belton, TX. ' Instructor In the Physlcal Therapy Program at the Uliversity of Central Arkansas. Conway, AR when this research was performed. He is presently Academic Assistant Professor at Texas Tech University Health Sciences Center. Lubbock. TX. Address all conespondence to Mr. Guffey at Texas Tech University Health Sciences Center. School of Allled Health. Department of Phys~cal Therapy. Lubbock. TX 79430. Graduate assistant In the Department of Physlcal Education. Unwersity of Central Arkansas. Conway. AR. 0196-601 1/89/1010-0418$02.00/0 TnE JOURNAL OF ORTHOPAEDIC AND SPORTS PHYSICAL THERAPY Copyright Q 1989 by The Orthopaedii and Sports Physical Therapy Sect~ons of the American Phys~cal Therapy Association brought under some sort of realistic framework when healthy competition exists. As more manufacturers have entered the market, and as more clinicians have developed new protocols for equipment usage, the range of available functions associated with a given exercise/testing device has tended to increase. As appropriate as this may be, clinicians must keep various factors in mind. One of the factors is whether or not a device allows the collection of accurate, reliable data. No matter how impressive the various functions possible in the use of a given device, the value of these functions does not exceed the reliability of the measures obtained when the functions are employed. Hydra-Fitness Industries, Inc. (P.O. Box 599, Belton, TX 76513) has recently entered the exerciseltesting market with a device known as the Omni Tron Total Power Unit. The purpose of this pilot investigation was to determine if the Omni Tron Total Power Unit could be considered reliable in a testlretest setting for measures of torque, work, and power at a preset accommodating resistance during a 5 repetition maximum effort test of knee flexionlextension using healthy adult subjects. 418 GUFFEY AND GUFFEY JOSPT April 1989

REVIEW OF LITERATURE Strength testing devices employing the principle of isokinetic resistance were originally introduced to the physical medicine field by the Cybex Corporation (21 00 Smithtown Ave, Ronkonoma, NY 1 1779). Reliability of measures in a testlretest setting using the Cybexm and Cybex II" devices has been established by several investigators (1, 5, 7, 8, 11, 12). In these studies, correlation coefficients of reliability in excess of r = 0.90 have been reported at several commonly used speeds employed in testing motions such as knee flexion and extension. Burnett et al. (3) reported reliable measures of hip muscle strength measurement in young boys using the Cybex II when he presented his findings at the June 1987 American Physical Therapy Association Annual Conference. Other manufacturers have marketed equip ment which appears to have gained acceptance in the testing and rehabilitation areas. Lord et al. (1 0) presented findings that strongly supported the reliability of data obtained measuring knee flexion/extension torque in both males and females using the LIDO lsokinetic Rehabilitation System (Loredan Inc., 1632 Da Vinci Court, Davis, CA 95617). Lord reported interclass correlation coefficients ranging from 0.83 to 0.94 while using two test speeds of 60 and 240 /sec. The Biodex Corporation (P.O. Box S, Shirley, NY 11967), a relative newcomer to the testing market, has recently made the authors of this study aware of an unpublished manuscript by Grabiner (6) regarding the reliability of one Biodex device. Using this device, Grabiner reported test/ retest correlation coefficients ranging from 0.80 to 0.96 for measures of trunk flexion/extension strength at speeds of 60, 120, and 180 /sec. If not the reliability, certainly the validity of the Biodex equipment was supported by a recent Broward County Florida court case (2). In this litigation, functional capacity measures generated with the Biodex device were deemed admissible as evidence. If a new testing device, such as the Hydra- Fitness Omni Tron, is to gain acceptance in the physical medicine arena it seems apparent that reliability values on the magnitude of those mentioned above need to be established using the device in a testlretest procedure. As mentioned, this is precisely the issue we addressed in this pilot study. METHOD Subjects Thirty-one subjects were included in this investigation. Each was given all information pertaining to the research purpose and procedures. After being fully briefed as to exactly what their participation would entail, all subjects read and signed consent forms and were assured they could withdraw their participation at any time. Nineteen of the subjects were female, ranging in age from 19-38 years, with a mean age of 24.1 1 years. The remaining subjects were male, ranging in age from 22-29 years, and having a mean age of 25 years. The subject pool consisted of volunteers from the Physical Therapy and Physical Education departments of the University of Central Arkansas. All of the subjects were considered normal, healthy adults, none having any history or diagnosis of knee pathology. Equipment The instrument used for testing was the Omni Tron Total Power Unit manufactured by Hydra Fitness Industries, Inc. The instrument has the capability to measure various factors pertaining to strength and endurance of the contractile tissue associated with the knee, chest, and shoulder. Strength and endurance can also be tested with regard to the abdominals and hip flexors as well as the back extensors. The Omni Tron Total Power Unit was interfaced with an Epson (Epson, 23610 Telo Avenue, Torrance, CA 90505) personal computer using software for data collection devised by Hydra-Fitness. This system allows the collection of multiple measurements of muscle performance which include: 1 ) Torque (peak, average and total) 2) Peak torque recruitment time 3) Power (peak, average and total) 4) Work (peak, average and total) 5) Angle of peak torque attainment 6) Range of motion 7) Angular and linear velocities 8) Fatigue ratio The resistance used in the Hydra-Fitness equipment in general, and the Omni Tron in particular, is not well defined. While elements of isotonic and isokinetic resistance are involved, this resistance is not fixed with regard to velocity. The equipment is based on a hydraulic principle. Resistance is determined by setting the size of an aperture within a hydraulic cylinder. Fluid is forced through the aperture as the patient moves a lever arm which is attached to the hydraulic cylinder. The amount of resistance encountered is directly related to the rate at which the fluid moves through the aperture. The resistance settings are arbitrary numbers, 1-1 2 (a setting of 1 indicating a very large aperture opening and therefore little resistance; a setting of 12 indicating a very small aperture opening and therefore maximum resistance). The manufacturer suggests that this resistance is self-accommodating and variable. This JOSPT April 1989 MEASURING KNEE FLEXION AND EXTENSION 419

accommodation is said to occur at any joint angle throughout the range of motion at any speed the subject is capable of generating with maximal effort. It is also claimed that as the subject slows his movement speed, owing perhaps to fatigue, for example, the resistance encountered will continue to be a maximal overload as long as maximal effort is maintained (1 3). The validity of the device for testing the strength of the various muscle groups mentioned has been supported by one unpublished study (9). Procedure On the first day of testing each subject was introduced to the Omni Tron and the testing procedure was performed as outlined by the manufacturer of the device (13) (Figs. 1-5). Demographic data, sufficient to facilitate storage and retrieval of data for future analysis, were obtained. At this point each subject was allowed five warmup repetitions on the device at a resistance setting of 5. Another two warm-up repetitions were performed at the testing resistance setting of 10. A 15 sec rest period was interposed between the two warm-up trials and before the actual test run. Finally, the subject performed five repetitions at a resistance setting of 10 (i.e., a small aperture opening) employing maximal effort. The right knee Figure 1. Setup for knee testing: right knee. Figure 2. Stabilization at ankle. 420 GUFFEY Figure 3. Stabilization at thigh. Figure 4. Stabilization at waist. Figure 5. Start position for testing. was tested in extension and flexion in all cases. Values for the following indicators of performance were obtained; 1) peak torque in extension, 2) peak torque in flexion, 3) peak power in extension, 4) peak power in flexion, 5) peak work in extension, 6) peak work in flexion, 7) total work in extension, 8) total work in flexion. An identical testing protocol was performed on the following day and the same measurements were gathered. The testing protocol was administered by the same investigator for all 31 subjects in both testing situations so as to assure continuity. During both testing situations the investigator provided strong verbal encouragement. AND GUFFEY JOSPT April 1989

Analysis of Data Table 3 Potential of learning as influence (N = 31) A coefficient of correlation was developed for each of the eight measurements listed above. The subject's scores from test 1 were compared to scores from test 2 using Pearson Product Moment to establish testlretest reliability of the maximum muscular performance at the resistance setting employed. A student t-test was also ap plied to the data in order to determine if any significant difference existed between the scores obtained in test 1 versus test 2. No. Scoring No. Scoring No. Scoring Indicator Higher Tl Higher T2 Higher T2 Power (extension) Power (flexion) Work (extension) Work (flexion) Total work (extension) Total work (flexion) RESULTS Eight measures of muscular performance were compared in this investigation. A testlretest method was used to assess the reliability of these measures. Table 1 displays the correlation coefficients obtained. Only one resistance setting was employed in this protocol. Table 2 contains the results of the student t- test performed to assess the difference between means of test 1 and test 2 for each of the eight performance indicators listed. As can be seen from the t-ratios in Table 2, none of the differences between means in any of the indicator categories existed at a statistically significant level (i.e., p < 0.05). Table 3 deals with the concept of learning. If the subjects benefited on the second day from the previous day's exposure to the equipment and procedure, the values obtained would certainly be affected. If learning had occurred, one would expect the values of test 2 to exceed those Table 1 Testlretest reliability, Pearson product moment correlation (N = 31) Measurement Parameter Peak power (extension) Peak power (flexion) Peak work (extension) Peak work (flexion) Total work (extension) Total work (flexion) r value Table 2 Student t-test, Elght Performance Indicators (N = 31) Indicator mean TI mean T2 t-ratio p Power (extension) Power (flexion) Work (extension) Work (flexion) Total work extension Total work flexion of test 1 in a majority of the cases. Table 3 shows that this was not the case. DISCUSSION As was noted earlier, many of the more commonly used isokinetic testing devices have been proven reliable for values obtained in normal testing situations (2-8, 10, 11). It is important to note that this device is not isokinetic, but does have many of the characteristics of such units. A high degree of reliability is vital if one is to place confidence in data gathered in assessing patientlsubject performance so that clinical decisions pertaining to diagnosis and proper corrective measures can be made. As can be seen from Tables 1 and 2, the Omni Tron Total Power Unit did produce rc!iable measures in the setting used in this investigation. The issue of validity is not addressed by this data. Certainly more subjects should be tested before any final determination as to reliability can be made regarding this instrument. Additionally, multiple resistance settings, and therefore testing speeds, should be examined to assure complete reliability. The authors are presently in the process of completing these more detailed assessments. However, from a pilot study perspective, it does appear there is potential for this instrument to collect reliable data. An area that should be mentioned concerning the Omni Tron would include its functionality in the clinic setting. We found the device to be very simple to use. The time required to perform tests averaged approximately 5-1 0 minutes. The analysis program associated with the unit is quite detailed and affords a wide range of performance indicators. The unit, including computer and printer, requires only approximately 10 square feet of floor space. Hydra-Fitness Industries claim (1 3) that the resistance generated with the Omni Tron is totally accommodating at whatever speed the subject works. Owing to the hydraulic principles upon which the device is based, the subject is not bound to any preset speed for testing or rehabilitation. We feel this may hold the potential for adaptability to a very wide range of subjects and settings. More work must be done to address the true nature of the resistance that is actually JOSPT April 1989 MEASURING KNEE FLEXION AND EXTENSION 421

being employed before any final conclusions as to efficacy can be drawn. It may be incorrect to use the physiological terms presented since this device does not completely control velocity or resistance. One obvious shortcoming from which this device suffers is the lack of true isolated joint testing. The knee is the only joint which can be tested in an isolated fashion. The other testing procedures include multiple joint movements. Compared to many of the commonly used devices (e.g., Cybex 11, Kin-Com, Biodex), the Omni Tron is limited in the area of variability of testing possibilities of isolated joints. Conclusions Based on the data gathered on this subject pop ulation, the authors concluded that the Omni Tron Total Power Unit is a reliable instrument for assessing certain muscular performance indicators under the limited conditions employed in this pilot study. Further study needs to be performed in the area of resistance definition related to this type of exercise. As mentioned earlier, the question of validity has been addressed in an unpublished work (9). Further work in this area is warranted. More detailed examination must be done regarding reliability of measures obtained in testing situations and protocols not included in this investigation. Research should be done on the relationship between values obtained with the Omni Tron and more traditional isokinetic devices in a manner similar to the work reported by Wilk et al. (14). a REFERENCES 1. Alexander J. Mdner GE: Muscular strength In children: Preliminary report on objective standards. Arch Phys Med Rehabil 54:424-427. 1973 2. Beard vs. State Paving Co.. Case +el-1 2431 CH. Broward County Circuit Court. Ft. Lauderdale, FL, May 1986 3. Burnett CN. Filush EM. King WM: Reliability of lsokinetic Testlng of HIP Muscle Strength In Young Boys. Presented at the American Physlcal Therapy Association Annual Conference. San Antonio. TX. June 1987 4. Davles GJ: lsokinetic approach to the knee. In: Mangine R (ed). Physical Therapy of the Knee. Vol 19. pp 221-241. New York: Churchhill Llvingston. 1984 5. Gilliam TB. Villancci JF. Freedson PS. Sadv SP: lsokinetic tomue in boys and girls ages 7 to 13: Effect of age, height and weight. R& Q 50599-601......, 1979.. 6. Grab~ner ND: Rdiabiliity of lsokinetic trunk flaxion and extension performance. Cleveland. OH (unpublished manuscript) 7. Hart DL. Barber DC. Davis H: Cybex II data acquisition system. J OrMop Sports Phys Ther 2(4):177-179.1981 8. Johnson J. Selgel D: Reliability of an sok kinetic movement of the knee extensors. Res Q 49:88-90. 1978 9. LaGasse P: Validation of the total power Ornni Tron. Human Performance Research Laboratory. Laval University, Ste-Foy, Quebec, Canada. (unpublished manuscript) 10. Lord J. Aitkens S. McCrory M. Bemauer E: Reliability of the LIDO D~gltalsokinetlc System for the Measurement of Muscular Strength. Presented at the American Physical Therapy Association Annual C w ference. San Antonio. TX. June 1987 11. Moffrold M. Wh~pple R. Hofkosh J. Lowman E. Thistle H: A study of isoklnetlc exercse. Phys Ther 49:735-743. 1969 12. Molnar GE. Alexander J: Objective. quantitatlve muscle testing in children: A pilot study. Arch Phys Med Rehabil54:225-232, 1973 13. Omnikinetics Operat~ons Manual. Hydra-Fttness Industries. Inc., Belton, TX 14. Wilk KE. Johnson RD, Levine B: A Comparison of Psak Torque Values of Knee Extension and Flexors Muscle Groups Using Bix. Cybex, and Kin-Com lsokinetic Dynamometers. Presented at the American Physical Therapy Association Annual Conference. San Antonto. TX. June 1987 GUFFEY AND GUFFEY JOSPT April 1989