The VHP and MAT tests were performed within the 2 testing days, evaluating the left and right sides separately. Additionally, the VHP was compared between sessions. Because fatigue would likely affect the results of multiple trials of the VHP test, intrasession results were calculated between 3 of the jumps performed in 1 trial. For both the power and jump height of the VHP test, the first 3 consecutive hops that reached at least 70% of the jump height of the initial jump were evaluated for reliability. For intersession results, the first 3 consecutive hops that reached at least 70% of the initial jump of the first day were compared to the first 3 jumps that met the same criteria on the second day. Means and standard deviations were calculated from the data collected for each test and intraclass correlation coefficients (within ICC [3,k], between ICC [3,1]) were calculated with statistical software. ICC values less than 0.4 were reported as poor, from 0.4 to 0.75 were fair to good, and greater than 0.75 were considered excellent (38).
The mean age of the subjects was 20.8 ± 3.8 years. The subjects weighed 68.9 ± 43.3 kg and measured 172.21 ± 9.12 cm in height. The mean power measured during the VHP test was 28.05 ± 3.58 W in this population. The mean jump height measured during the VHP test was 13.06 ± 3.04 cm (Table 1). Separately, the left mean power was 28.47 ± 3.75 W and the right was 27.62 ± 3.40 W. The left mean jump height was 13.08 ± 2.88 cm and the right was 13.04 ± 3.23 cm.
The VHP test had excellent within-session reliability for peak power of both the right (ICC = 0.942) and left (ICC = 0.895) sides. Jump height showed excellent within-session reliability for both the right (ICC = 0.963) and left (ICC = 0.940) sides.
The between-session reliability for peak power between jumps was good for the right (ICC = 0.748) and left (ICC = 0.834) sides. Jump height showed excellent between-session reliability on the right (ICC = 0.794) and left (ICC = 0.909) sides.
The mean time to complete the MAT test in this population was 9.59 ± 0.57 seconds. The subjects performed the right MAT test in a mean time of 9.55 ± 0.57 seconds and the left MAT test in a mean of 9.63 ± 0.59 seconds. The MAT test also showed excellent reliability between days (ICC = 0.825).
The purpose of this report is to provide objective field-testing methodology designed to isolate lower-extremity asymmetry and to demonstrate the potential for these tests to provide reliable measures. Quantitative measurements, such as functional assessment tests, can be used to document the progression of a patient's strength, tolerance, and performance abilities during rehabilitation (5,29,32,36). Highly reliable functional assessment tests are required to compare results from multiple testing sessions during the progression of rehabilitation protocols. The current findings indicate that the VHP and MAT tests provide good to excellent reliability as lower-extremity functional assessment tests. One major hypothesis was accepted because the VHP and the MAT tests provide high within-session, but not between-session, test-retest reliability (ICC > 0.75) in athletes tested. These tests may be useful measures of determining an athlete's readiness to return to sport following lower-extremity injury.
Athletes who have experienced a significant lower-extremity injury such as an ACL rupture are likely at an increased risk of injury for both the injured and contralateral limbs (2,34,39,40). Paterno et al. demonstrated that female athletes who have completed rehabilitation and returned to sports following ACL reconstruction continued to have significant asymmetries in landing, cutting, and jumping more than 2 years after surgery (36). Mattacola et al. and Kobayashi et al. found that significant asymmetry in strength measures were present 18 months after ACL reconstruction (22,25). Because side-to-side asymmetries may increase risk for injury in healthy subjects (15), residual side-to-side deficits may be important risk factors to consider before allowing an athlete to return to sports activities and should be targeted during the rehabilitation process (22,25,29,36). Functional assessment tests may help identify deficits in strength, coordination, landing kinetics, and power that may increase an athlete's risk of injury when returning to sports activities (5,19,22,25,29,32,36).
Current functional assessment tests, such as performance during shuttle run tests and force measurements during landing from a jump or side-step tasks may not effectively evaluate movement performance or contributions of a single limb (6,16,18,19,29,35). Functional hop tests such as the single-leg hop, crossover hop, triple hop, and timed hop have been used to evaluate ACL injury rehabilitation progress (32). However, many of these functional hop tests have a low sensitivity and specificity for determining lower-extremity asymmetries (16), and these movements do not take into account other high-risk multi-planar movements, such as perpendicular cutting and challenging lateral motions (7,29). Thus, additional tests may be required to further evaluate the functional readiness of an athlete to return to sport following ACL reconstruction or other lower-extremity injury.
The VHP and MAT tests used in this study may provide alternative methods to evaluate lower-extremity symmetry during functionally demanding tasks. In the past, power hops on a force plate and functional hop tests for subjective analysis of lower-extremity function have been used to evaluate single-limb symmetry (29,32). However, in sporting activities, athletes must make multiple single-footed ground contacts safely, while controlling the landing forces and takeoff power. Therefore, a VHP test was developed to integrate these parameters into a functional assessment test. At the same time, the MAT test was developed to evaluate perpendicular cutting tasks. Pauole et al. reported that the T-test (Figure 4), typically used in football conditioning, is a useful tool for determining sports-related measures of speed, power, and agility (37). The T-test incorporates perpendicular cuts in both right and left directions during the timed test. To identify limb function asymmetries, the T-test was modified to isolate right and left directional cuts into 2 different test measures (Figure 3).
Both the VHP and MAT tests are challenging tasks that require sufficient strength and neuromuscular control. Although these tests may be excellent tools for evaluating patient progress following injury and readiness to return to sport, using a single test in isolation may not adequately simulate all of the challenging movements an athlete may encounter on the playing field. Thus, incorporation of several different types of functional assessment tests are important when evaluating an athlete's readiness to return to sport (29).
Clinicians should be especially aware of the possible gap between an athlete's perceived vs. actual functional readiness to return to sport (29). Objective, quantitative functional assessment tests, such as the VHP and MAT, may help clinicians justify why sports restriction may be important, despite an athlete's perceived readiness to return to sport. At the same time, fear of reinjury is a major concern of many athletes and their fear may hinder performance and return to sports activity (23). Kvist and colleagues reported that 24% of athletes who sustained ACL injury did not return to their pre-injury level of activity because of fear of reinjury (23). Functional assessment tests may help athletes gain confidence in their rehabilitated limbs because quantitative measures allow the athlete to see progressive improvement during the rehabilitation process and show the athlete that they are within sufficient ranges of function compared to their noninjured limb before returning to sport.
Functional assessment tests may also be useful as pre-screening tools to identify risks for lower-extremity injury, particularly tools that identify lower-extremity asymmetry. Hewett and colleagues prospectively measured biomechanical factors predictive of ACL injury in healthy female athletes (15). Uninjured athletes who later sustained an ACL injury after biomechanical testing demonstrated significant side-to-side differences in knee load compared to control athletes. Side-to-side knee abduction movement was 6.4 times greater in athletes who sustained ACL injury compared to control athletes. In addition, knee abduction movements predicted ACL injury with high sensitivity and specificity (15). If effective screening tools can be developed to identify athletes at risk for potential lower-extremity injury, these at-risk athletes can be placed in injury prevention programs (12,13,24,30).
Functional assessment tests that measure functional ability provide clinicians with useful tools to monitor the rehabilitation progress of athletes. The VHP test and the MAT tests are objective, quantitative, and reliable functional field assessment tests that may help clinicians evaluate patient rehabilitation progress and readiness to return to sport after lower-extremity injury. The VHP and MAT tests may also be useful on-site screening tools to help identify athletes who may be at increased risk for lower-extremity injury. Future studies should evaluate the validity, sensitivity, and specificity of the MAP and VHP test for identifying lower-extremity asymmetries in patients recovering from lower-extremity injury and in healthy populations. If the VHP and MAT tests are found to be valid, sensitive, and specific measures for identifying lower-extremity asymmetries, these tests may be useful tools to determine the readiness of an athlete to safely return to sport following injury, to predict risk for lower-extremity injury, and to guide prevention programs.
1. Adirim, TA and Cheng, TL. Overview of injuries in the young athlete. Sports Med
33: 75-81, 2003.
2. Arendt, E and Dick, R. Knee injury patterns among men and women in collegiate basketball and soccer. NCAA data and review of literature. Am J Sports Med
23: 694-701, 1995.
3. Baumhauer, J, Alosa, D, Renstrom, A, Trevino, S, and Beynnon, B. A prospective study of ankle injury risk factors. Am J Sport Med
23: 564-570, 1995.
4. Boden, BP, Dean, GS, Feagin, JA, and Garrett, WE. Mechanisms of anterior cruciate ligament injury. Orthopedics
23: 573-578, 2000.
5. Brosky, JA Jr, Nitz, AJ, Malone, TR, Caborn, DN, and Rayens, MK. Intrarater reliability of selected clinical outcome measures following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther
29: 39-48, 1999.
6. Cascio, BM, Culp, L, and Cosgarea, AJ. Return to play after anterior cruciate ligament reconstruction. Clin Sports Med
23: 395-408, ix, 2004.
7. Ernst, G, Moore, J, VanLunen, B, and Ball, D. Pondering plyometrics. J Orthop Sports Phys Ther
25: 350-352, 1997.
8. Ferretti, A, Papandrea, P, Conteduca, F, and Mariani, PP. Knee ligament injuries in volleyball players. Am J Sports Med
20: 203-207, 1992.
9. Ford, KR, Myer, GD, Smith, RL, Vianello, RM, Seiwert, SL, and Hewett, TE. A comparison of dynamic coronal plane excursion between matched male and female athletes when performing single leg landings. Clin Biomech
21: 33-40, 2006.
10. Giza, E, Fuller, C, Junge, A, and Dvorak, J. Mechanisms of foot and ankle injuries in soccer. Am J Sports Med
31: 550-554, 2003.
11. Hawkins, RD and Fuller, CW. A prospective epidemiological study of injuries in four English professional football clubs. Br J Sports Med
33: 196-203, 1999.
12. Heidt, RS Jr, Sweeterman, LM, Carlonas, RL, Traub, JA, and Tekulve, FX. Avoidance of soccer injuries with preseason conditioning. Am J Sports Med
28: 659-662, 2000.
13. Hewett, TE, Lindenfeld, TN, Riccobene, JV, and Noyes, FR. The effect of neuromuscular training on the incidence of knee injury in female athletes. A prospective study. Am J Sports Med
27: 699-706, 1999.
14. Hewett, TE, Myer, GD, Ford, KR, Heidt, RS Jr, Colosimo, AJ, and Divine, JG. Pre-season Football combine testing to isolate neuromuscular deficits predictive of ACL injury and reinjury risk. Cincinnati Children's Hospital Medical Center, NFL Charities, 2007.
15. Hewett, TE, Myer, GD, Ford, KR, Heidt, RS Jr, Colosimo, AJ, McLean, SG, van den Bogert, AJ, Paterno, MV, and Succop, P. Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes: A prospective study. Am J Sports Med
33: 492-501, 2005.
16. Hewett, TE, Paterno, MV, and Myer, GD. Strategies for enhancing proprioception and neuromuscular control of the knee. Clin Orthop
402: 76-94, 2002.
17. Hootman, JM, Dick, R, and Agel, J. Epidemiology of collegiate injuries for 15 sports: Summary and recommendations for injury prevention
initiatives. J Athl Train
42: 311-319, 2007.
18. Jamshidi, AA, Olyaei, GR, Heydarian, K, and Talebian, S. Isokinetic and functional parameters in patients following reconstruction of the anterior cruciate ligament. Isokinet Exerc Sci
13: 267-272, 2005.
19. Keays, SL, Bullock-Saxton, JE, Newcombe, P, and Keays, AC. The relationship between knee strength and functional stability before and after anterior cruciate ligament reconstruction. J Orthop Res
21: 231-237, 2003.
20. Klein, KK. Asymmetries in the pelvis and legs and their implications in knee injury. Am Correct Ther J
24: 93-95, 1970.
21. Knapik, JJ, Bauman, CL, Jones, BH, Harris, JM, and Vaughan, L. Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes. Am J Sports Med
19: 76-81, 1991.
22. Kobayashi, A, Higuchi, H, Terauchi, M, Kobayashi, F, Kimura, M, and Takagishi, K. Muscle performance after anterior cruciate ligament reconstruction. Int Orthop
28: 48-51, 2004.
23. Kvist, J, Ek, A, Sporrstedt, K, and Good, L. Fear of re-injury: A hindrance for returning to sports after anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc
13: 393-397, 2005.
24. Mandelbaum, BR, Silvers, HJ, Watanabe, D, Knarr, J, Thomas, S, Griffin, L, Kirkendall, DT, and Garrett, WJ. Effectiveness of a neuromuscular and proprioceptive training program in preventing the incidence of ACL injuries in female athletes: Two-year follow up. Am J Sport Med
33: 1003-1010, 2005.
25. Mattacola, CG, Perrin, DH, Gansneder, BM, Gieck, JH, Saliba, EN, and McCue, FC. 3rd Strength, functional outcome, and postural stability after anterior cruciate ligament reconstruction. J Athl Train
37: 262-268, 2002.
26. McKay, GD, Goldie, PA, Payne, WR, and Oakes, BW. Ankle injuries in basketball: Injury rate and risk factors. Br J Sports Med
35: 103-108, 2001.
27. McKay, GD, Goldie, PA, Payne, WR, Oakes, BW, and Watson, LF. A prospective study of injuries in basketball: A total profile and comparison by gender and standard of competition. J Sci Med Sport
4: 196-211, 2001.
28. Mikkelsen, C, Werner, S, and Eriksson, E. Closed kinetic chain alone compared to combined open and closed kinetic chain exercises for quadriceps strengthening after anterior cruciate ligament reconstruction with respect to return to sports: A prospective matched follow-up study. Knee Surg Sports Traumatol Arthrosc
8: 337-342, 2000.
29. Myer, GD, Paterno, MV, Ford, KR, Quatman, CE, and Hewett, TE. Rehabilitation after Anterior cruciate ligament reconstruction: Criteria based progression through the return to sport phase. J Orthop Sports Phys Ther
36: 385-402, 2006.
30. Myklebust, G, Engebretsen, L, Braekken, IH, Skjolberg, A, Olsen, OE, and Bahr, R. Prevention of anterior cruciate ligament injuries in female team handball players: A prospective intervention study over three seasons. Clin J Sport Med
13: 71-78, 2003.
31. NFHS. High School Participation Survey. Indianapolis: National Federation of State High School Associations, 2007.
32. Noyes, FR, Barber, SD, and Mangine, RE. Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture. Am J Sports Med
19: 513-518, 1991.
33. Olsen, OE, Myklebust, G, Engebretsen, L, and Bahr, R. Injury mechanisms for anterior cruciate ligament injuries in team handball: A systematic video analysis. Am J Sports Med
32: 1002-1012, 2004.
34. Orchard, J, Seward, H, McGivern, J, and Hood, S. Intrinsic and extrinsic risk factors for anterior cruciate ligament injury in Australian footballers. Am J Sports Med
29: 196-200, 2001.
35. Paterno, MV, Ford, KR, Myer, GD, Heyl, R, and Hewett, TE. Biomechanical limb asymmetries in female athletes 2 years following ACL reconstruction. Clin J Sport Med
17: 258-262, 2007.
36. Paterno, MV, Ford, KR, Myer, GD, Heyl, R, and Hewett, TE. Limb asymmetries in landing and jumping 2 years following anterior cruciate ligament reconstruction. Clin J Sport Med
17: 258-62, 2007.
37. Pauole, K, Madole, K, Garhammer, J, Lacourse, M, and Rozene, R. Reliability and validity of the T-test as a measure of agility, leg power, and leg speed in college-aged men and women. Journal of Strength and Conditioning Research
14: 443-450, 2000.
38. Portney, LG and Watkins, MP. Foundations of Clinical Research
. Norwalk, CT: Appleton & Lange, 2000.
39. Salmon, L, Russell, V, Musgrove, T, Pinczewski, L, and Refshauge, K. Incidence and risk factors for graft rupture and contralateral rupture after anterior cruciate ligament reconstruction. Arthroscopy
21: 948-957, 2005.
40. Wright, RW, Dunn, WR, Amendola, A, Andrish, JT, Bergfeld, J, Kaeding, CC, Marx, RG, McCarty, EC, Parker, RD, Wolcott, M, Wolf, BR, and Spindler, KP. Risk of tearing the intact anterior cruciate ligament in the contralateral knee and rupturing the anterior cruciate ligament graft during the first 2 years after anterior cruciate ligament reconstruction: A prospective MOON cohort study. Am J Sports Med
35: 1131-1134, 2007.