Effect of a Lateral Step-up Exercise Protocol

Transcription

1 Effect of a Lateral Step-up Exercise Protocol on Quadriceps and Lower Extremity Performance Teddy W. Worrell, EdD, PT, SCS, ATC' Bonnie Borchert, MS, PT, ATC2 Kristi Erner, MS, PT2 /die Fritz, MS, PT, ATC2 Pam Leerar, MS, PT2 Copyright All rights reserved. A trophy and strength loss of the extensor mechanism are major concerns following knee injury or surgery (2,.5,8,14,23). Weakness of the quadriceps femoris contributes to instability and functional losses (2,5). Recovery of quadriceps strength is, therefore, of primary concern to the clinician during the rehabilitation process. Open kinetic chain rehabilitation and assessment are performed with the distal segment (foot and lower leg) free, as in isotonic and isokinetic exercise modes (22). More recent protocols have incorporated closed kinetic chain (CKC) activities (distal segment is fixed) such as squats, step-ups, and the leg press (9,22,26) for quadriceps strengthening. Frequently, the lateral step-up exercise is used during rehabilitation of lower extremity injuries (1,6,10, 11,13,16,25,26). Several limitations of open kinetic chain exercises exist, including isolated knee motions and lack of cocontraction at the knee (22), increased patellofemoral compression (15). increased anterior shear forces, and elongation of the anterior cruciate ligament (12). Proposed benefits of CKC exercises are cocontrac- Closed kinetic chain exercises have been promoted as more functional and more appropriate than open kinetic chain exercises. limited research exists demonstrating the effect of closed kinetic chain exercise on quadriceps and lower extremity performance. The purpose of this study was to determine the effect of a lateral step-up exercise protocol on isokinetic quadn'ceps peak torque and the following lower extremity activities: I) leg press, 2) maximal step-up repetitions with body weight plus 25%, 3) hop for distance, and 4) 6-m timed hop. Twenty subjects participated in a 4- week training period, and 18 subjects served as controls. For the experimental group, a repeated measure ANOVA comparing pretest and posttest values revealed significant improvements in the leg press (p I.05), step-ups (p r.05), hop for distance (p r.05), and hop for time (p r.05) and no significant increase in isokinetic quadriceps peak torque (p r.05). Over the course of the training period, weight used for the step-up exercise increased (p I.05), repetitions decreased (p r.05), and step-up work did not change (p r.05). For the control group, no significant change (p r.05) occurred in any variable. The inability of the isokinetic dynamometer to detect increases in quadriceps performance is important because the isokinetic values are frequently used as criteria for return to functional activities. We conclude that closed kinetic chain testing and exercise provide additional means to assess and rehabilitate the lower extremity. Key Words: hop tests, lateral step-up, muscle strength ' Assistant Professor, Director of Research, Krannerf Graduate School of Physical Therapy, University of Indianapolis, 1400 East Hanna Ave., Indianapolis, IN Student, Krannerf Graduate School of Physical Therapy, University of Indianapolis, Indianapolis, IN. This study was performed in partial requirement for the master of science degree in physical therapy. tion of quadriceps and hamstring muscles; functional lower extremity movement using eccentric and concentric contractions at the hip, knee, and ankle; decreased anterior translation of the tibia on the femur; and decreased elongation force on the anterior cruciate ligament (1-3, 6,7,9,22). After reviewing the literature, we have been unable to locate reports of significant strength gains using a step-up exercise protocol. Moreover, Reynolds et al (24) reported that a progressive step-up protocol without resistance did not increase quadriceps isokinetic peak torque measures. They suggested that their training method was not of sufficient intensity to provide a train- Volume 18 Number 6 December 1993 JOSPT

2 Copyright All rights reserved. ing effect and that CKC testing may be a more valid method for assessing lower extremity function. Therefore, the purpose of this study was to determine the effect of a.2-m (8-in) lateral step-up exercise protocol on isokinetic quadriceps peak torque and CKC performance defined as 1) one repetition leg press, 2) maximal step-up repetitions with body weight plus 25%, 3) hop for distance, and 4) hop for time. METHODS Subjects Thirty-eight healthy university physical therapy students with no history of knee pathology or surgery volunteered for participation. Subjects were instructed not to begin or increase the intensity of any lower extremity strengthening program during the training period of this study. Activity level varied from sedentary to very active among both groups. Twenty subjects participated in the experimental group (9 male, 1 1 female), and 18 subjects (6 male, 12 female) participated in the control group (Table 1). Subjects were informed of the purpose of the study, testing procedures, and exercise protocol prior to participation. Fach subject also read and signed a consent form approved by a university human subjects committee. Testing Procedures All subjects were familiarized with the testing procedures 4 days prior to pretesting. During the familiarization session, each subject performed all of the testing procedures. Subject testing order and exercised leg were randomly determined. Only Age f SD Weight f SD Height f SD Group (years) (kz) (cm) Conlrol 24.4 f f f f f f 9.2 TABLE 1. Description of subjects. one leg of the control group was tested. lsokinetic Knee Extension A Biodex isokinetic dynamometer (Biodex, Shirley, NY) was used to measure peak torque in Nm. Calibration was performed prior to testing. Concentric knee extension was tested between 90" and 0" of knee flexion at 1.02 rad/sec (60 /sec). Subjects were tested in a seated position with the waist and distal thigh strapped for stabilization. The tibia1 Appropriate lateral step-up technique was defined as maintaining a horizontal pelvis throughout the motion and keeping the nonexercised ankle in dorsiflexion to ensure that all motion was initiated by the tested leg. pad was placed approximately 2.5 cm proximal to the medial malleolus. The dynamometer's axis was aligned with the anatomical axis of rotation of the knee. To determine gravity effect torque, each extremity was weighed according to the manufacturer's recommendation (knee at full extension). The testing protocol consisted of a warm-up in which the subject performed two repetitions each at perceived exertions of 50, 75, and 100%. This was followed by a 1 -minute rest period and then two more repetitions at 100% perceived effort. After a 1-minute rest, three maximal repetitions were recorded. The largest peak torque value for the three test curves was used in the data analysis. Standardized verbal encouragement was provided for all subjects. Lateral Step-up Test Maximum number of lateral step-up repetitions performed while holding 25% body weight was recorded. Subjects were instructed to stand on the tested leg on a.2-m (8-in) step. The nonexercised ankle was actively maintained in a dorsiflexed position and slowly lowered to the ground by flexing the hip and knee of the tested leg. The nonexercised heel lightly touched the ground and was immediately raised to the starting position. Each repetition required approximately 2 seconds, which was monitored by the researchers. Subjects held a weighted dowel rod (2.5- or 3.2-cm diameter) in the ipsilateral hand of the tested leg (Figure 1). A hole was drilled 2.5 cm from the dowel end, in which one end of a tied rope was secured. The other end of the dowel was notched to allow the other end of the tied rope to be quickly removed when changing weights. Appropriate lateral step-up technique was defined as maintaining a horizontal pelvis FIGURE 1. lateral step-up exercise test for maximal repetitions with body weight plus 25%. Wooden dowel has rope attached to secure weights. JOSPT Volume 18 Number 6 December 1993

3 Copyright All rights reserved. throughout the motion and keeping the nonexercised ankle in dorsiflexion to ensure that all motion was initiated by the tested leg. Subjects performed a warm-up consisting of three repetitions holding 25% body weight followed by a 1-minute rest. Testing was terminated when the subject fatigued or failed to maintain proper technique. Leg Press Test A leg press machine (Paramount, Los Angeles, CA) was used to determine a unilateral, one-repetition maximum leg press. Seat position was set at 90" of hip and knee flexion, and hands were allowed to grip the handles adjacent to the seat. Prior to testing, subjects performed a warm-up that included five repetitions at the lowest weight setting and two repetitions with 30 kg. Weight was progressively increased according to the subject's perceived exertion until a one-repetition maximum was obtained to the nearest kg. Subjects rested 30 seconds between test repetitions. Single-Leg Hop Test for Distance Each subject performed a maximal hop for distance using only one leg for propulsion and landing. Distance was measured from the starting point to the landing position of the heel of the tested leg. Two warm-up hops were allowed. After a 1-minute rest period, two hops were performed and the average score was recorded. During pilot testing (N = 36), it was determined that the average of two test repetitions was required for reliable single-hop test scores (hop for distance ICC =.99; hop for time ICC =.77). Single-Leg Hop Test for Time Six meters were measured on a gymnasium floor with start and stop lines designated by a 0.5-m strip of athletic tape. Subjects were in- structed to assume a crouched position on one leg. The researcher stood next to the finish line with a stopwatch (accuracy.0 1 second). Timing began when the subject sprang from the crouched position and ended when the subject crossed the finish line. Two warm-up efforts were performed. After a 1-minute rest period, two trials were taken and the average score was recorded. Training Program Subjects in the training group performed lateral set-up exercises 3 days per week for 4 consecutive weeks. The Daily Adjusted Progressive Resistance Exercise (DAPRE) protocol (Table 2) was used to determine exercise resistance (1 7.18). Four sets were performed daily with a 1-minute rest period between sets. The first two sets were warm-up rep etitions and the final two sets were maximal effort repetitions. During the training period, subjects held weighted dowels in both hands to maintain balance while performing lateral step-ups as previously described (Figure 2). Statistical Analysis A one-way repeated measure analysis of variance (ANOVA) was 1. Determine working weight (WW) 6 repetition maximum 2. Set 1: 10 repetitions of 50% WW 3. Set 2: 6 repetitions of 75% WW 4. Set 3: Maximum repetitions of WW 5. Set 4: Maximum rc!petltlons " ot ' the ' 'adjusted - '. ' working weight" (! iee below) Number of Reps Performed in - Adjustments to Working Weight* Set 3 Set4 Next Day 0-2 Decrease 2-5 Repeat set 3-4 Decrease 0-2 Same weight 2-7 Same weight Increase lncrease 2-5 lncrease lncrease 5-7 lncrease 5-10 'All weights in kilograms. TABLE 2. Daily adjustable progressive resistance exercise (DAPRE) (18). FIGURE 2. lateral step-up exercise for training period. used to compare pretest and posttest data for all five dependent variables: isokinetics at 1.02 rad/sec (60 "/set), maximum lateral step-ups, one-repetition maximum leg press, hop for distance, and hop for time. A oneway repeated measure ANOVA was used to compare step-up force (F = M X A; M = body mass + holding mass, A = m/sec2), step-up repetitions, and step-up work (W = F X D; D = step-up repetitions X.2 m (8 in) performed in the fourth set of the DAPRE (Session 1 vs. Session 12). The significance level was set at p Daily attendance was recorded to determine compliance with the exercise program. RESULTS Significant improvements occurred in four of the five dependent variables in the experimental group (Table 3): 1) hop for time (p 5.05, Figure 3), 2) hop for distance (p 5.05, Figure 4), 3) leg press (p r.05, Figure 5), and 4) maximal step-up repetitions with body weight plus 25% (P 5.05, Figure 6). No significant increase occurred in isokinetic Volume 18 Number 6 December 1993 *JOSPT

4 R Posttest Copyright All rights reserved Posttest Difference TABLE 3. Control and experimental group pretest and posttest values for the five dependent variables. peak torque in the experimental group (p r.05, Figure 7). No significant increase occurred in any of the five dependent variables for the control group (p 2.05, Table 3). For the experimental group, in comparing Session 1 with Session 1 2, a significant increase (p r.05) occurred in the force developed during the fourth set of the lateral step-up protocol (Figure 8), but no significant change (p r.05) occurred in the work produced (Figure 9). A significant reduction ( p 5.05) occurred in lateral step-up repetitions during the fourth set (Session 1 vs. Session 12) (Figure 10). Attendance records revealed that all 20 subjects attended all 12 exercise sessions. Two members of the control group were eliminated from the study because they increased their activity level during the course of the study. (Initially there were 20 members in the control group.) Control FIGURE 3. Six-meter single-leg hop test for time. r indicates standard deviation. 60 Distance 50 (cm) n Control FIGURE 4. Single-leg hop test for d~stance. r indicates standard deviation. H Posttest DISCUSSION We conclude that this aggressive, 4-week, lateral stepup exercise protocol improved lower extremity performance as measured bv CKC activ- Control FIGURE 5. Single-leg one repetition maximum leg press. r indicates standard deviation. JOSPT Volume 18 e Number 6 December

5 Copyright All rights reserved. Step-up Reps Control FIGURE 6. Lateral step-up exercise test for maximal repetitions with body weight plus 25%. T indicates standard deviation. Posttest 200 Nm a Posttest n " Control FIGURE 7. lsokinetic peak torque at 1.02 radlsec (6O0/sec). indicates standard deviation. ities. The DAPRE protocol is a daily adjusted (adjusted three times per week in this study) aggressive exercise program. The overload principle of the DAPRE protocol is illustrated by I) the increase in force developed (Figure 8), 2) no change in work produced (Figure 9), and 3) the decrease in the repetitions in the fourth set of the exercise protocol (Figure 10). Because the DAPRE protocol (Table 2) ad-justed the "working weight" each exercise day based on the number of repetitions performed, the force increased, but the number of repetitions decreased because of the increasing resistance (weight). Consequently, the work (W = F x D) did not significantly change because the distance (repetitions) decreased while the force increased. Therefore, the DAPRE meets the requirement of a strengthening protocol (ie., low repetitions, high resistance, and significant increases in nluscle performance). Improvements in lower extreniity performance as revealed by the two hop tests, leg press, and lateral step-up test indicated that significant strength gains occurred in a relatively short time. Strength gains achieved during the 4 weeks probably represented an increase in neural adaptation. Moritani and DeVries (20) reported that neural factors (increased motor unit recruitment) were responsible for initial strength gains and that muscle hypertrophy became more dominant after the first 3-5 weeks of training. Direct comparison of this study with others is not possible because of the paucity of CKC training studies. Reynolds et al (24), however, reported that a progressive, 6-week, lateral stepup protocol (4-14 in) Strength gains achieved during the weeks probably represented an increase in neural adaptation. without resistance failed to demonstrate significant quadriceps strength gains as measured by an isokinetic dynamometer. These authors did not evaluate lower extremity function in the CKC. Lack of statistically significant pre-post changes in isokinetic scores indicates that isokinetic testing was not sensitive enough to detect actual improvements in lower extremity performance and strength in this study (and possibly in the Reynolds et al study). Predicting CKC function following anterior cruciate ligament injury from isokinetic dynamometry has recently been questioned (1 9). Because of the exercise mode (lateral step-up) of this study, one could expect a learning effect in the testing mode, ie., the CKC. Since most ath- Volume 18 Number 6 December 1993 JOSPT

6 Copyright All rights reserved. Exercise Sessions FIGURE 8. lateral step-up force developed during the fourth set of the DAPRE protocol (Session I vs. Session 12). T indicates standard deviation. Joules Exercise Sessions FIGURE 9. Lateral step-up work produced during the fourth set of the DAPRE protocol (Session I vs. Session 12). T indicates standard deviation. letes and nonathletes function in a CKC mode, rehabilitation and assessment should be performed in a CKC. Therefore, any learning effect JOSPT Volume 18 Number 6 December 1993 would have a beneficial carryover to functional activities. During the testing sessions, subjects held a single wooden dowel that secured the weights (Figure 1). During the training sessions, however, subjects were required to hold two dowels in order to balance the weights (Figure 2). As the length of the training program increased, several subjects experienced difficulty holding the heavier weights and maintaining their balance. Wrist straps were used to help secure the dowels and assistance was provided as needed for balance. As the load increased, difficulty holding the weight and maintaining balance became problematic during the third and fourth training weeks. Initially, a 6-week training period was planned. The training study, however, was terminated after 4 weeks because the subjects had difficulty holding the weights and balancing. The.2-m (8-in) lateral stepup was chosen because minimal equipment is needed and, theoretically, patients can exercise at their convenience using a step or a stack of books at home. However, caution should be used when recommending using books because of the possibility of falling. We recommend that the patient first demonstrate this procedure in the clinic. Patients can place weights in a purse or secure them using a rope, dowel, or barbell. There is a limit to the amount of weight that a patient can lift and balance during a resistive stepup. Since injured patients have a decreased capacity to perform resistive stepup exercises, the difficulties of holding and balancing the weights have not been as problematic in the clinical setting. Use of a weighted vest that allows insertion of various weights eliminates the difficulty of holding heavy weights. Caution must be used in generalizing this specific protocol to the patient population. Though the increases in the CKC tests were statistically significant, the absolute changes were small to moderate (Table 3). One would anticipate such small to moderate increases because the subjects were young, healthy, and active. In

7 step-up Reps 6 Posttest strengthening as presented in this paper be used as a component of the rehabilitation. When generalizing this aggressive lateral stepup protocol to the patient population caution should be used. We recommend that a pain-free, progressive stepup protocol without resistance be used prior to the initiation of the resistive phase. Clinically, we gradually increase step height to.2 m (8 in) and repetitions from 40 to 100 depending on the patient's response before a resistive protocol is initiated. Progression rate is determined by the patient's individual response. Copyright All rights reserved. FIGURE 10. Lateral step-up repetitions during the fourth set of the DAPRE protocol (Session I vs. Session 12). T indicates standard deviation. addition, the training period was short. Patients with a knee injury or reconstructive surgery will present with significant quadriceps weakness and will have a much greater response to a strengthening protocol (1 8). During pilot testing, we determined the reliability of the two, single-leg hop tests: hop for time and hop for distance. We used a practice repetition and then two test repetitions. The mean of the two test repetitions was stable when compared to a retest session 1 week later [hop for time ICC (2, 1) =.77 and hop for distance ICC (2, 1) =.99]. However, the individual test repetitions were significantly different for each testing session and between testing sessions, indicating a learning effect. Two practice trials and two test repetitions (mean of two test repetitions) were required for reliable values in this study. Limitations exist in predicting functional ability using single-hop tests in the anterior cruciate ligament deficient population (4,2 1.27). Hop tests, as performed in this study, were used to assess changes in lower extremity performance as a result of the training protocol. No studies support that single-leg hop tests will predict a patient's ability to return to activities of daily living or sport. Hop tests will, however, allow comparisons to be made between injured or noninjured extremities. Because of the demands of the singleleg hop tests, their use in the nonathletic population is not indicated. Moreover, these tests should only be used in individuals who require high demands on their daily living or sport activities. In summary, hop tests allow comparison of noninjured and injured extremities but they do not predict functional outcomes at the present time. Clinical Implications The inability of the isokinetic dynamometer to detect strength gains related to CKC training and increases in lower extremity performance has significant clinical implications. For example, isokinetic quadriceps muscle performance has been one criterion that clinicians use to allow athletes to return to activity following anterior cruciate reconstruction (26). Open chain testing can better isolate a weakened muscle for assessment and rehabilitation, while during CKC testing, many muscle groups can influence the test results. Nevertheless, we recommend that CKC testing and lower extremity SUMMARY Results of this study demonstrated that a 4-week closed kinetic chain (CKC) exercise protocol in healthy subjects provided sufficient overload to increase lower extremity performance as measured by two, one-leg hop tests, the leg press, and maximal stepup repetitions with body weight plus 25%. No significant increase occurred in isokinetic quadriceps peak torque for the exercised group. For the control group, no significant increase occurred in any variable. We conclude that CKC testing and exercise provide additional insights into lower extremity performance. JOSPT ACKNOWLEDGMENTS The authors thank Kris Ingersoll, PhD, ATC, and Ken Knight, PhD, ATC, both with Indiana State University, Terre Haute, IN, for their critical comments and recommendations concerning this manuscript. REFERENCES I. Antich TH, Brewster C: Rehabilitation of the nonconstructed anterior cruciate ligament-deficient knee. Clin Sports Med 7(4): , Antich TH, Brewster CE: Modification of the quadriceps femoris muscle exercises during knee rehabilitation. Volume 18 Number 6 December 1993 JOSPT

8 Copyright All rights reserved. Phys Ther 66(8): , Baratta R, Solomonow M, Zhou BH, Letson D, Chuinard R, D'Ambrosia R: Muscle coactivation, the role of the antagonist musculature in maintaining knee stability. Am / Sports Med l6(2): , Barber SD, Noyes FR, Mangine RE, McCloskry /W, Hartmand W: Quantitative assessment of functional limitation in normal and anterior cruciate ligament deficient knees. Clin Orthop 255: , Baugher WH, Warren RH, Marshall 11, loseph A: Quadriceps atrophy in the anterior cruciate insufficient knee. Am / Sports Med 12(3): , Blair DF, Willis RP: Rapid rehabilitation following anterior cruciate ligament reconstruction. / Athl Train 26(1):32-43, Brask B, Lueke RH, Soderberg CL: Electromyographic analysis of selected muscles during the lateral step-up exercise. Phys Ther 64(3): , Brunet ME, Stewart CW: Patellofemoral rehabilitation. Clin Sports Med 8(2): , Case /C, DePalma BR, Zelco RR: Knee rehabilitation following anterior cruciate ligament repair/reconstruction: An update. / Athl Train 26:22-3 1, Codfrey 1, Abramowski E, Tice B, Reese B: The lateral step-up. In: Scriber K, Burke 1 (eds), Relevant Topics in Athletic Training, pp Ithaca, NY: Mouvement Publications, 1978 I 1. Harrelson CL: The lateral step-up box. Sports Med 6(2):23-24, Henning CE, Lynch MA, Click KR: An in vivo strain gauge study of elongation of the anterior cruciate ligament. Am I Sports Med 13(1):22-26, Hirschberg CC: The use of stand-up and step-up exercises in rehabilitation. Clin Orthop 12:30-46, Huegel M, lndelicato PA: Trends in rehabilitation following anterior cruciate ligament reconstruction. Clin Sports Med 7(4): , Hungerford D, Barry M: Biomechanics of the patellofemoral joint. Clin Orthop 144:9-15, Kegerreis S: The construction and implementation of functional progression as a component of athletic rehabilitation. / Orthop Sports Phys Ther 5(1):26-3 1, Kisner C, Colby LA: Therapeutic Exercise Foundation and Techniques (2nd Ed), pp Philadelphia: F. A. Davis Company, Knight KL: Quadriceps strengthening with the DAPRE technique: Case studies with neurological implications. Med Sci Sports Exerc 17(6): , Lephart SM, Perrin DH, Fu FH, Cieck lh, McCue FC, lrrgang I/: Relationship between selected physical characteristics and functional capacity in the anterior cruciate ligament insufficient athlete. I Orthop Sports Phys Ther 16(4): , Moritani T, DeVries HA: Neural factors vs. hypertrophy in time course of muscle strength gain. Am I Phys Med Rehabil58: , Noyes FR, Barber SD, Mangine RE: Abnormal lower limb symmetry determined by functional hop tests after anterior cruciate ligament rupture. Am I Sports Med 19(5): , Palmitier RA, An K-N, Scott SC, Chao EYS: Kinetic chain exercise in knee rehabilitation. Sports Med 1 1 (6):4O2-412, Paulos 1, Noyes FR, Crood E, Butler DL: Knee rehabilitation after anterior cruciate ligament reconstruction and repair. Am / Sports Med 9(3): , Reynolds NL, Worrell TW, Perrin DH: Effect of a lateral step-up exercise protocol on quadriceps peak torque values and thigh girth. I Orthop Sports Phys Ther 15(3): , Seto /L, Brewster CE, Lombardo SH! Tibone /E: Rehabilitation of the knee after anterior cruciate ligament reconstruction. / Orthop Sports Phys Ther 11(1):8-18, Shelbourne KD, Nitz P: Accelerated rehabilitation after anterior cruciate ligament reconstruction. Am / Sports Med 18(3): , Tegner Y, Lysholm I, Lysholm M, Cillquist I: A performance test to monitor rehabilitation and for evaluation of anterior cruciate ligament injuries. Am I Sports Med l4(2): , 1986 JOSPT Volume 18 Number 6 December 1993