Prophylactic ankle stabilizers affect ankle joint kinematics during drop landings STEVEN T. McCAW and JAMES F. CERULLO

Department of Health, Physical Education and Recreation, 5120 Illinois Stare University, Normal, IL 61790-5120

ABSTRACT

McCAW. S. T. and J. F. CERULLO Prophylactic ankle stabilizers affect ankle joint kinematics during drop landings. Med. Sci. Sporrs Exerc., Vol. 31. No. 5, pp. 702-707, 1999. Purpose: Ankle joint dorsiflexion contributes to energy absorption during landing, but wearing ankle stabilizers is known to resuict passive measures of dorsiflexion. This study compared the effects of various ankle stabilizers on ankle joint kinematics during soft and stiff landings. Methods: Subjecrs (iV = 14) performed two-legged landings off a 0.59-m platform. Kinematics of the right ankle were calculated from a sagittal plane video recording (120 Hz). Five soft and five stiff landings were performed in five ankle stabilizer conditions (no stabilizer, taping, Swede-0. AirCast, and Active Ankle), a total of 50 trials per subject. Style and stabilizer conditions were randomized across subjects. Each subject's five-trial mean value of selected kinematic variables for each landing style/stabilizer condition was entered into a two-way repeated MANOVA (a = 0.05). Results: Differences between soft and stiff landing conditions were similar to those reported in the literature. Compared with the No stabilizer condition, most stabilizer conditions significantly reduced ankle dorsitlexion ROM and angular velocity during landing. Conclusions: The results indicate that some ankle stabilizers adversely affect ankle joint kinematics during landing. Key Words: TAPING. BRACES, ORTHOTICS, ROM. SHOCK ABSORPTION

A

common mechanism of ankle ligament injury is an applied inversion stress while the ankle is in a plantarflexed position. Such loading may damage the lateral structures of the joint, specifically the anterior talofibular and calcaneofibular ligaments (2). To decrease the risk of an inversion sprain. traditional ankle taping or various commercially available ankle stabilizers have been used to provide functional stabilization to the joint (1,13,14,17,23). Although the mechanism of prophylaxis with ankle stabilization is not clear (I l,l7), epidemiological evidence suggests the use of ankle stabilizers is cost effective for reducing the frequency of ankle injuries (6,13,18,21). A restriction of inversion and eversion ranges of motion (ROM) with ankle stabilization has been reported in several studies (3,1622.23). After several minutes of activity, the measured ankle joint ROM approaches the ROM measured in a nonstabilized condition (7-9,16). Authors typically interpret the results as indicative of a loss of support from the stabilizer (16) and suggest that loosened stabilizers are 0195-9 131/99/3 105-070210 MEDICINE S( SCIENCE IN SPORTS & EXERCISE, Copyright O 1999 by the American College of Sports Medicine Submitted for publication December 1997. Accepted for publication July 1998.

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ineffective for protecting the joint. However, over 20 years ago Garrick and Requa (6) proposed that an ideal stabilizer would not impinge on the usual ROM of the ankle joint. Restriction should occur only at the anatomical limits of joint motion, the position beyond which joint capsule or ligament damage begins to occur. This concept of the ideal brace recognizes the importance of an unimpeded ankle joint ROM to the generation and absorption of energy during skill performance. Several studies have demonstrated the importance of eccentrically controlled ankle dorsiflexion to energy absorption during landing (4,5,10). DeVita and Skelly (4) reported alterations in the relative contribution of the ankle, knee, and hip joints to energy absorption between soft and stiff landings. In soft landings the hip, knee, and ankle joints contributed 25, 37, and 37%, respectively, to the total energy absorbed by the lower extremity. During stiff landings. in addition to less total energy absorption by the lower limb, the relative contributions of the hip, knee, and ankle joints were altered to 20, 31, and 50%. respectively, of the total energy absorbed. As landing stiffness increased, the posterior ankle musculature contributed more to relative energy absorption while the contribution of the posterior hip and anterior knee musculature decreased. Practitioners recognize the importance of unimpeded h~p: knee, and ankle flexion to shock absorption. Kareem Abdul

J'abbar attributed his long career in the National Basketball Association to the use of low cut basketball shoes, stating ((19). p. 90): "Your skeletal system was built to absorb shock. If you bind your ankles, the stress is going to get transferred to the next available joint-your knee." In spite of the acknowledged importance of the ankle to energy absorption, quantification of an altered contribution to energy absorption during conscious restrictions of ankle motion, widespread use of prophylactic ankle stabilizers, and the reported impingements of ankle joint range of motion when wearing ankle stabilizers, no published studies compare ankle kinematics during landing with different conditions of ankle stabilization. The purpose of this study was to compare the effects of landing style and ankle stabilizers on ankle joint kinematics during landing. The ankle joint kinematic variables quantified were (a) angular displacement (plantarflexion and dorsiflexion) and (b) angular velocity.

METHODS Subjects. Fourteen college students (five female: age, 20 t 1 yr; height, 1.66 f 0.05 m; mass, 60 2 5 kg; and nine male: age, 21 t 2 yr; height, 1.77 f 0.07 m; mass, 83 5 16 kg) volunteered as subjects. As determined by a questionnaire, all subjects were experienced in landing (history of participation in basketball or volleyball) and free of any acute or chronic injuries for 1 yr before data collection. Before participating, all subjects read and signed an informed consent form in accordance with the policy statements of ACSM and approved by the Institutional Review Board of the University. Ankle stabilization. In addition to the condition with no stabilizer, data were collected from four ankle stabilized conditions, including tape and three commercially available stabilizers. Manufacturers provided the stabilizers in different sizes. Stabilizers were applied to both ankles of each subject by the same certified athletic trainer according to recommendations of the manufacturer. Details of each stabilized condition are described below. For the tape condition. the shaved foot and ankle were sprayed with a tape adherent (Cramer Tuffskin. Gardner, KS) and wrapped with a foam prewrap. Gel-lubed heel 2nd lace gauze pads were applied before ankle taping. The certified athletic trainer applied bleached white tape (Coach Athletic Tape, Johnson & Johnson, Skillman, NJ) using a modified Gibney closed basketweave, with two heel locks and two figures-of-eight (2). Stabilizer 1 was a lace-up, boot style stabilizer (Swede0-Universal, North Branch, MN) recommended as a cost reducing alternative to taping of the ankle joint. The stabilizer was included in the study because it covers the medial/ lateral and anterior/posterior surfaces of the ankle joint from above the rnalleoli to the base of the metatarsals, similar to ankle taping. Stabilizers 2 and 3 consisted of two semirigid plastic outer shells hinged to a plastic stirrup at the malleoli. The stabilizers are held in place by two self-stick straps spaced ANKLE STABILIZERS DURING LANDING

approximately 0.02 m apart encircling the distal shank superior to the malleoli. Stabilizer 2 was lined with inflatable air cells (Aircast Sport Stirrup, Summit, NJ) while stabilizer 3 was lined with foam (Cramer Active Ankle, Gardner, KS). These stabilizers were included in the study because they both provide medial and lateral support while leaving open the anterior and posterior surfaces of the ankle joint, making them mechanically different from tape and stabilizer I. Experimental protocol. Before the actual data collection. each subject was fitted with a pair of standard low cut laboratory running shoes and practiced both soft and stiff landings from the required height. Collection of landing data used a technique similar to that of DeVita and Skelly (4). T o control vertical speed to approximately 11.6 m.s-' at landing, subjects stepped off a 0.59 m high wooden platform placed 0.1 1 m behind the back edge of the landing target. The take-off technique was conrrolled by having each subject assume a position on the top step of the platform with both arms flexed to shoulder height and the heel of the right foot resting against the front edge of the platform. The subject then leaned forward to step off the platform. The technique allowed the subject to minimize horizontal motion and land equally balanced on both feet, with the right foot closest to the video camera. Subjects were instructed to land with maximum knee fleltion during soft landings and minimum knee flexion during stiff landings. Five landing trials of each subject were recorded within each of the 10 landing conditions (two landing styles (soft and stiff) and five stabilized conditions (nonstabilized. taped, Stabilizer I (Swede-0), Stabilizer 2 (X~rCast).Stabilizer 3 (Active Ankle)). All conditions were performed during a single test session of approximately 3 h duration. Ankle stabilized conditions were randomized across all subjects. and landing style was randomized within each ankle stabilized condition. T o maximize any effect of ankle stabilization, landings were performed immediately after application of the orthotic. Video recording. A sagittal plane recording was made of each landing trial in each condition using a high speed (17-0 Hz) video system (Peak Performance Technologies Inc.. Englewood. CO). The camem was set at a height of 0.8 In and positioned approximately 7.0 m from the lanciinf area to provide a sagittal plane field of view approximately 1.5 m wide and 2.2 m high. To track and digitize anatomical landmarks definlng the foot and shank of the right lower extremity. reflective tape markers approximately 2 cm in diameter were placed on: a) the lateral shoe upper at the base of the fifth metatarsal; b) the lateral heel of the shoe just superior to the seam between the sole and heel cup; c) the lateral malleolus; and d) the knee joint center. After fitting for each stabilizer condition. the lateral malleolus was carefully palpated and the marker replaced over the stabilizer. The ankle was defined (Fig. I) as the relative angle between the foot (heel and fifth metatarsal) and the shank (lateral malleolus and knee joint center). The two segments did not share a common vertex. The Peak5 software was Medicine & Science in Sports & Exercise

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Figure 2--Typical ankle joint position curves for stiff (dashed line) and soff (solid line) landings. Positive values are plantarflexion, negative values are dorsiflexion. Ground contact occurs at time 0. The curves for the ankle stabilized landings followed the same general pattern.

O

Plantarflexion

Figure 1-Convention

used to measure ankle joint position.

used to calculate the ankle angle, with plantarflexion and dorsiflexion measured in degrees from the anatomical (0") position. Digitization. Following time-coding of the video tape. the four anatomical landmarks were automatically digitized (Peak5 Performance Technologies Inc.. Video and Analog Motion Measurement Systems Software Version 5.3). Digitizing began 20 fields before initial toe contact (touch down). a period including the last 0.1 s of the descent phase. plus eight extra fields. Successive fields were digitized until at least 16 fields following observed maximum knee flexion, the end of the shock absorption phase. Additional fields were digitized to improve the accuracy of data smoothing with a digital Filter. The x and y coordinate data of each landmark were smoothed using the optimized Butterworth Filter option of the Peak5 software. The cut-off frequencies, determined using the Jackson "knee" method (12) with the preferred level set at 0.1, varied within the range of 5 to 9 Hz. Representative curves for soft and stiff landings are presented in Figure 2. The dependent variables defining ankle 704

Gfficial Journal of the American College of Sports Medicine

joint lunematics included joint angle at touch down (degrees plantarflexion), angle at maximum knee flexion (degrees dorsiflexion), ankle joint ROM (degrees). maximum ankle angular velocity (degrees per second), and time to maximum ankle angular velocity (s). Statistics. For each subject. a five-trial mean vahe of each dependent variable was calculated for each of the 10 landing styles by stabilizer conditions and used in the statistical analysis. The measurement of multiple dependent variables during multiple conditions necessitated the use of a doubly multivariate 2 X 5(landing style by stabilizer) MANOVA (20). with a: = 0.05. Since ROM is a linear combination of joint angle at touch down and angle at maximum knee flexion, ROM was not included in the MANOVA. To identify the source of a significant omnibus F-ratio, univariate repeated measure ANOVA were conducted on each dependent variable, including the ROM. When appropriate, the Tukey-b procedure (a = 0.05) was utilized to identify which stabilizer mean values were significantly different. Post-hoc power analyses indicated multivariate power values of 0.61 for the landing style by stabilizer interaction, and 0.89 and 1 .OO for style and stabilizer main effects, respectively.

RESULTS The repeated-measures MANOVA indicated no significant interaction (Wilks h = 0.68. F = 1.14, P = 0.241). but both style (Wilks h = 0.29. F = 6.01. P = 0.010) and stabilizer (Wilks h = 0.20, F = 6.40, P < 0.0005) main effects were identified. Figures 3 to 7 present the descriptive statistics of landing style-stabilizer conditions for each dependent variable in graphic format. The presentation of results will focus only on identified main effects, interpreting the outcome of the univariate repeated measures ANOVA conducted for each independent variable. Ankle joint angle at touch down. There was no significant landing style effect ( F , , . , 3 , = 0. I I , P = 0.748). but there was a significant stabilizer effect (F ,,,52, = 13.38.

Figure &Ankle joint position (degrees of plantarflexion) at initial floor contact during a drop landing.

p

< 0.0005). The Tukey post-hoc analysis revealed 2-4"

plantarflexion in the Swede-0 (1 1.0 5 6.4"), Aircast 1 1.1 f 5.0"). and tape (12.5 5.7") conditions compared with the Active Ankle (13.4 + 6.4") and no stabilizer (15.2 f 6.7") conditions. Ankle angle at maximum knee flexion (end of shock absorption). There were significant main effects = 17.27, P < 0.0005) and stabilizer of landing style ( F (F = 10.71, P < 0.0005). Group means indicate about 5' difference in dorsiflexion between soft (25.5 + 4.2") and stiff (19.0 f 4.4") landings. The Tukey post-hoc analysis ievealed approximately 1-3" less dorsiflexion in the tape (20.0 f 3.5"). Aircast (20.6 + 3.7"). and Swede-0 (21.0 f 4.5") conditions compared with the no stabilizer (23.2 2 4.9") and Active Ankle (24.3 + 3.3") conditions. Ankle joint ROM (plantarflexion and dorsiflexion combined). There were significant main effects of landing = 24.91, P < 0.0005) and stabilizer (F ,,.j2, style ( F = 21.74 P < 0.0005). Group means revealed approximately 6" difference between soft (38.3 ? 6.5") and stiff (3 1.9 -+ 6.3") landing styles. This value is similar to the 5' difference between soft and stiff landings that has been associated with significant changes in energy absorption by the ankle joint S 'S

+

,,,,-),

,,.,,,

Figure %Ankle joint range of motion during the landing phnse.

(4). The Tukey post-hoc analysis indicated 5-6" less ankle joint ROM in the Aircast (32.6 5.8"), Swede-0 (32.8 f 6.6"), and tape (32.9 5.2") conditions compared with the Active Ankle (38.0 + 7. I") and no stabilizer (39.4 -+ 7.0") conditions. Maximum ankle angular velocity. There was no significant main effect of landing style (F = 1.43, P = 0.253). but there was a significant main effect of stabilizer ' ( F ,A,,2, = 28.68, P < 0.0005). The maximum ankle angular velocity was lower during each stabilizer condition compared with the nonstabilized condition. The Tukey post-hoc analysis revealed that angular velocity in the Swede-0 (526.7 C 91.5O.s-I) and Aircast (5 17.4 + 7 1.7"-s-I) con- ' ditions was 70-1200.s-' slower than the Active Ankle (590.2 + 101.3".s-~)and no stabilizer (639.7 f 95.20.~-I) conditions. Angular velocity in the Active Ankle (590.7- 2 10 1.3"s-I) and tape (546.6 f 69.1".sC1) conditions was 50-90O.s-' slower than the no stabilizer condition (639.7 2 95.2O.s- I). Time to maximum angular velocity. There was no = significant main effect for either landing style ( F 0.17, P = 0.683) or stabilizer ( F (4.52) = 1.90. P = 0.125).

+

+

,,,,,,

DISCUSSION

Figure 4-Ankle joint position (degrees of dorsiflexion) at the end of the landing phase during a drop landing. ANKLE STABILIZERS DURING LANDING

The purpose of this study was to compare the effects of landing style and ankle stabilizers on ankle joint kjnematics during landing. Different methods of stabilizing the ankle, including commercially available ankle braces. were compared. This study did not investigate the effects of the ankle stabilizers on the prevention of ankle inversion sprains. No evaluations of subject comfort or stabilizer preference were made. As a result, the results should not be interpreted as suggesting that one method of stabilization is preferable to any ocher method of stabilization. In fact, since the data were collected for this study. each of the manufacturers who donated a model for testing have brought to market new models of the stabilizers. The results of this study suggest that some prophylactic ankle stabilizing techniques commonly used to prevent inversion sprains impinge on the normal kinematics of the Medicine & Science in Sports & Exercise

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Tape

Figure 6-Maximum phase.

SwedO

Aircast

ActAuk

ankle joint angular velocity during the landing

ankle joint during drop landings. Compared with the unstabilized control condition, some stabilizers restricted the ankle joint range of motion during landing. reflecting a combination of reduced ankle plantarflexion at contact and reduced dorsiflexion during the impact phase of ground contact. The finding of a reduced range of sagittal plane motion during landing with ankle stabilization is counter to the report of no effect of stabilization on sagittal plane motion during running by Lindley and Kemozek ( 1.5).However. the range of motion when running is less than that used in landing, and any restriction from ankle stabilization may not interfere with the measured range of motion. The implication of a reduced ankle range of motion during landins is that less energy may be absorbed by the soft tissues controlling the ankle motion. especially the eccentric action of the posterior ankle musculature. DeVita and Skelly (4) demonstrated a change in the relative contribution of the ankle, knee, and hip joints to energy absorption between soft and stiff landing styles. They determined that the hip, knee, and ankle absorbed 25. 37, and 37%, respectively, of the total energy absorbed during soft landings. When subjects consciously reduced joint range of motion to land stiff. the relative contribution of the lower extremity joints to total energy absorption was changed to 20, 3 1, and 50% for the hip, knee. and ankle joints. respectively. In the present study, the change from soft to stiff

NS

Figure 7-Time landing phase.

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Tape

SwedO

Aircart

ActAnk

to maximum ankle joint angular'velocity during the

Official Journal of the American College of Sports Medicine

landings was characterized kinematically by a 5" reduction in ankle joint range of motion, similar to that presented by DeVita and Skelly (4). The 5" decrease in dorsiflexion range of motion from soft to stiff landings is similar to the quantified change between the unstabilized landing condition and some of the stabilizing techniques used in the cun-ent ~ t u d y ,specifically ankle taping and stabilizers 1 and 2 . A subsequent project that arises from the present study is to quantify whether knee and hip joint kinematics are altered when ankle stabilizers are used. Of greater importance is to determine, using an inverse dynamic analysis. whether the 5" decrease in dorsiflexion ROM when landing with ankle stablizers is accompanied by alterations in the energy absorption patterns of the ankle, knee, and hip joints similar to those reported by DeVita and Skelly (4) for soft and stiff landings. Although energy absorption was not measured in this study, there were measured changes in the maximum iingular velocity of dorsiflexion during landing. For the three stabilized conditions that exhibited significantly less dorsiflexion range of motion than the unstabilized condition, the maximum dorsiflexion angular velocity was. on average, about I 10O.s-' less than that in the unstabilized condition. A reduction in angular velocity could retlect a decrease in energy absorption based on the work-energy relationship. Changes in the angular component of kinetic energy of a body occur when work, in the form of an unbalanced torque over a range of motion, is done on the body. In landing, the angular velocity of the joints is reduced to zero at the end of the descent phase. A higher peak angular velocity retlkcts a greater angular kinetic energy of the rotating bodies. Greater negative work, in the form of a torque upplied opposite to the direction of rotation, must be done to reduce the angular kinetic energy to zero. The source of the torque to decrease angular velocity at the ankle is the eccentric activity in the posterior muscles of the ankle. Thus. it may be hypothesized that greater eccentric activity was needed to reduce the higher dorsiflexion angular velocity exhibited during a landing with unstabilized ankles compared with a landing with stabilized ankles. Since eccentric activity of muscles reflects absorption of energy (24), greater energy absorption by the posterior ankle muscles would occur during landings with ankles unstabilized compared with landings with ankles stabilized. Conversely. reduced energy absorption by the ankle musculature while wearing stabilizers would mean greater energy transfer up the leg, increasing the demand on knee and hip musculature to absorb energy if the same total energy is to be absorbed by the lower estremity in stabilized and unstabilized landings. Support of this interpretation will require application of an inverse dynamics analysis to measure the energy absorption during landings with and without ankle stabilization. The stabilizing techniques that significantly reduced ankle joint range of motion either wrap completely around the footlankle complex (tape and stabilizer I) or grip the medial and lateral malleolus in air cells (stabilizer 2 ) . The single stabilizer tested that did not significantly affect ankle kinematics was characterized by a hinge support intended to

, ,ovidz Crontul planc strtbility whlle

not tightly binding to he malleoli. No measures were made of pressure exerted on the ankle joint by the different stabilizing techniques used, but the manufacturer's guidelines for use of the stabilizers were followed during application. Also, testing was conducted immediately after application of the stabilizing technique, and no activity time, known to cause loosening of the stabilizer, was provided. With regard to the limitations described, it is concluded that design features of the different mbilizers affect the extent to which a stabilizer interferes with the usual ankle joint kinematics. Future refinements in design must consider the potential for the stabilizer to interfere with the desired range of motion during dynamic activities such as landing. In this way, the design of the

"ideal bracc" as proposcd by Garrick and Requa (6) will be closer to being realized, and protection from inversion ankle sprains will be provided without compromising the petiormance of the lower extremity when landing. h e authors gratefully acknowledge support from the National Science Foundation Instrumentation and Laboratorv lm~rovement prodram (DUE-935 1660); the Illinois Assoclatlon fo; ~ e s l t h ,Physlcal Education, Recreation, and Dance Jump Rope for Heart program; and the lllinols State University research grant program. Stablllzers used In the study were contributed by the manufacturers, and use of a particular model of stabilizer In the study does not constitute endorsement by the authors. Address for correspondence: Dr. Steve McCaw, Dept of HPER, 5120 lllinols State Un~versity, Normal, IL 61790-5120. e-mall: [email protected].

REFERENCES I. ALVES.J. W., R. V. ALD.AY.D. L. KETCHAM, and G. L. LENTELL. A comparison of the passive support provided by various ankle braces. J. Ortliop. Sporrs Phys. Ther: 15: 10- 18. 1992. 2. ARNHEIRI.D. D. Moe/~rttPriti~.ipIeso f AtItI~ricTr~lining.St. Louis. MO: Mosby College Publishing, 1993. pp. 283-284. 3. BRUNS.J.. J. SCHERLLTZ. and S. LUESSENHOP. The stabilizing effect of orthotic devices on plantar flexionJdorsa1 extension and horizontal rotation of the ankle joint. Int. J. Sports Med. 17:614-618, 1996. 1. DEVITA,P. and W. A. SKELLY.Effect of landing stiffness on joint kinetics and energies'in the lower extremity. Med. Sci. Sports Exert. 24: 108-1 15. 1992. 5, FEUERRACH. J. W.. T. M. LUNDIN. and M. D. CRABINER. Effect of ankle support on leg muscle activation. kinematics and kinetics during drop landings. In: Conjerence Proceeclings. Americcm Society uj' Siomecl~nnics,A. A. Biewener and V. K. Goel (Eds.). Iowa City. Iowa: University of Iowa, 1993. pp. 33-24. 6. CARKICK.J. C. and R. K. REQUA.Role of external support in the prevention of ankle sprains. ~MedSci. Sporrs 5:300-203. 1973. T. A. and C. R. WIGHT. A comparative support evaluation 7. GREENE. of three ankle orthoses before. during, and after exercise. J. Or[hop. Sports Plivs. Tlter. 1 1 :453-466. 1990. 8. GROSS.M. T.. C. L. B.ALLARD, H. G. PIEARS.and E. J. WATKINS. Comparison of Donjoy ankle ligament protector and Aircast sportstirrup orthoses in restricting foot and ankle motion before and after exercise. J. Ortlrop. 5port.r P11y.s. Tlier. 16:60-67. 1992. 9: GROSS. M. T.. A. L. BAITEN.A. L. LA~ILI. et al. Comparison of Donjoy ankle ligament protector and subtalar sling ankle taping in restricting foot and ankle motion before and after exercise. J. Ort/io/~. Sl~ortsfh!,s. Tlirr. 19:33-4 1 . 1994. 10. GROSS. T. S. and R. C. NELSON. The shock attenuation role of the ts ankle during landing from a vertical jump. Meci. Sci. S ~ ~ o rExerc. 20:506-5 14, 1958. I I. HEIT. E. J.. S. 34. LEPHART. and S. L. Rozzr. The effect of ankle bracing and taping on joint position sense in the stable ankle. J. Sporr. Rehrrbil. 5:306-2 1 3. 1996.

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13. JACKSON. K. M. Fitting of mathematical ti~nctionsto biomechanicnl data. IEEE Trcrrrs. Biometl. E1r.q. BME 26: 122-124. 1979. 15. JEROSCH. J.. L. THORWESTHN, H. BOKK.and M. BISCHOF.IS prophylactic bracing of the ankle cost effective. Orrl~opcdics19:405414. 1996. 14. KARLSSON. J.. L. SWARD.and G. 0. ANDREASSON. Tlie effect of taping on ankle stability: practical implications. Sports Mecl. 16: 210-215. 1993. 15. LINDI-EY, T. R. and T. W. KERNOZEK. Taping and semirigid bracing may 11otaffect ankle functional range of motion. J. Atltl. Trniftitlg 30:109-112, 1995. 16. MARTIN. N. and R. A. HARTER. Comparison of inversion restraint provided by ankle prophylactic devices before and after exercise. J. At111. Trczirrittg 35:321-33-8. 1993. 17. SHAPIRO.M. S.. J. M. L\Ro. P. W. MITCHELL.G. LOREN. and M. TSENTER. Ankle sprain prophylaxis: an analysis of the stabilizihg effects of braces and tape. /\rn. J. Sports Meif. 22:78-82. 1994. IS. SITLER,M.. J. RYAN.B. WHEELER. et ;\I. The efficacy of a semirigid ankle stabilizer to reduce acute ankle injuries in basketball. A I ~ J. I . Sports Merl. 2 4 5 4 - 4 6 1 . 1994. 19. S~IITH,G. NOW,more than ever. a winner. Sports Nllrstr. December 30. 1985: 78-82. 84-85. 90-94. 20. STEVENS. J. Applirrl iW~iltivrlrictte St~lti.stic~j>)r the Socirrl Scic*ric.es. Mahwah. NJ: L. El-lbaurn Associates. 1996. pp. 500-503 21. SURVE.I.. 1M. P. SCHWELLN~S. T. NOAKES.and C. L ~ M I ~ A RAD . fivefold reduction in the incidence of'recurrent ankle spr:~i~isin soccer players using the sport-stirrup orthosis. /\/ti. J . Sl>orr.sMccl. 2260 1-605. 1994. 21. WILEY,J. P. and B. M. NIGG. Tlie effect of an ankle orthosis on ankle range of motion and performance. J. Ortltop. Sl~ot.f.P/I,Ys. Tlrer. 33:362-369. 1996. 33. WILKERSON. G. B. Comparative biomechanical effects of the stnndard nlethod of ankle taping and a taping method designccl to enhance subtalar stability. Aln. J. sport.^ Merl. 19:588-595. I99 I. 24. WINTER,D. A. Biomechutiic~atld Motor Corltrol of H~tntcrnM o ~ v ~nrnt.New York: Wiley-Interscience. 1990. pp. 10.1-1 1 I.

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