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The effect of lateral banking on the kinematics and kinetics of the lower extremity during lateral cutting movements
Human Movement Science 33 (2014) 97–107
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Human Movement Science journal homepage: www.elsevier.com/locate/humov
The effect of lateral banking on the kinematics and kinetics of the lower extremity during lateral cutting movements John W. Wannop ⇑, Eveline S. Graf, Darren J. Stefanyshyn Human Performance Lab, University of Calgary, Canada
a r t i c l e
i n f o
Article history: Available online 26 September 2013 PsycINFO classification: 3720 Keywords: Joint loading Banking Kinematics Kinetics Lower extremity
a b s t r a c t There are many aspects of cutting movements that can limit performance, however, the implementation of lateral banking may reduce some of these limitations. Banking could provide a protective mechanism, placing the foot and ankle in orientations that keep them out of dangerous positions. This study sought to determine the effect of two banking angles on the kinematics and kinetics of the lower extremity during two athletic maneuvers. Kinematic and kinetic data were collected on 10 recreational athletes performing v-cuts and side shuffle movements on different banked surfaces (0°, 10°, 20°). Each sample surface was rigidly attached to the force platform. Joint moments were calculated and compared between conditions using a repeated measures ANOVA. Banking had a pronounced effect on the ankle joint. As banking increased, the amount of joint loading in the transverse and frontal planes decreased likely leading to a reduction in injury risk. Also an increase in knee joint loading in the frontal plane was seen during the 20° bank during the v-cut. Conversely loading in the sagittal plane at the ankle joint increased with banking and coupled with a reorientation of the ground reaction vector may facilitate a performance increase. The current study indicates that the 10° bank may be the optimal bank, in that it decreases ankle joint loading, as well as increases specific performance variables while not increasing frontal plane
⇑ Corresponding author. Address: Human Performance Laboratory, University of Calgary, Faculty of Kinesiology, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada. Tel.: +1 403 220 7119; fax: +1 403 284 3553. E-mail address: [email protected] (J.W. Wannop). 0167-9457/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.humov.2013.07.020
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knee joint loading. If banking could be incorporated in footwear it may be able to provide a protective mechanism for athletes. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction 1.1. Injury Some of the most common injuries in sports such as basketball occur in the lower extremity (35.9– 92%), with the ankle and foot accounting for majority of these injuries (16.6–44%), followed by the knee (5–20%) (Harmer, 2005; Hikey, Fricker, & McDonaled, 1997; Messina, Farney, & DeLee, 1999; Taylor & Attia, 2000; Zvijac & Thompson, 1996). A large percentage of ankle injuries are inversion ankle sprains (22–65%) (Harmer, 2005), with the primary cause thought to be an excessive inversion moment, which exceeds the internal eversion moment provided by the peroneal muscles when the ankle is in a plantarflexed and inverted position (Stacoff, Steger, Stussi, & Reinschmidt, 1996). Recently, footwear companies have considered incorporating lateral banking elements into their footwear, which raises the lateral aspect of the foot relative to the medial aspect. In theory incorporating lateral banking elements has the potential to reduce inversion ankle sprains by reducing the amount of ankle inversion during plantarflexion, keeping the ankle joint further away from the limit of its range of motion where ankle ligaments may be prone to injury. Banking could also allow additional time for the peroneal muscles to react and provide lateral support to prevent ankle sprain at the crucial time immediately after foot strike (Simpson, Shewokis, Alduwaisan, & Reeves, 1992). Banking also has the potential of reducing the loading that the ankle joint experiences, specifically the inversion moment during athletic movements. During a side cut, loading is oriented on the medial aspect of the foot and forefoot (Queen, Haynes, Hardaker, & Garrett, 2007). Banking could invoke a lateral shift in the centre of pressure, reducing the ankle joint moment arm in the frontal plane, thereby reducing the inversion moment that potentially leads to ankle injury (Shelburne, Torry, Steadman, & Pandy, 2008). As well theoretical calculations by Greene (1987) clearly showed that banking can decrease the peroneal tendon force required to stabilize the ankle joint, and Alexander (1991) stated that aligning the resultant force vector with the leg generally leads to favorable minimization in joint moments and musculoskeletal stresses. The knee joint is also frequently injured in sport and while benefits to the ankle joint are plentiful, benefits to the knee joint may also result from banking. Patellofemoral pain is thought to occur when frontal plane moments are large (Stefanyshyn, Stergiou, Lun, Meeuwisse, & Worobets, 2006), and lateral wedging (banking) has been shown to reduce these frontal plane moments (Fisher, Dyrby, Mundermann, Morag, & Andriacchi, 2007; Kakihuna et al., 2005; Kerrigan et al., 2002; Mundermann, Nigg, Humble, & Stefanyshyn, 2003). However the direct influence of banking on knee injuries is not as clear as for the ankle joint. 1.2. Performance It has been shown that flat curved running is slower than straight running with a tighter turn leading to a greater decrease in performance. Cutting maneuvers can also be considered running with a very small radius of curvature (Chang & Kram, 2007; Jain, 1980). In sport, greater running speeds are achieved with a greater ground reaction force (Weyand, Sternlight, Bellizzi, & Wright, 2000). Recent studies examining curvilinear running have concluded that the same peak resultant force is present compared to straight running; however the direction of the resultant force changes due to the required centripetal acceleration providing a smaller vertical component and a greater horizontal component (Chang & Kram, 2007). A smaller vertical force vector requires an increase in ground contact time to generate vertical impulse to support body weight over
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the entire stride (Usherwood & Wilson, 2006), with this increase in contact time leading to a decrease in performance. Additionally, force generation by leg extensor muscles may be compromised when the joints are not aligned. A theoretical model has shown performance increases of up to 10% for banked situations with performance decreases of up to 10% seen with ankle eversion of only 30° (Greene, 1987). While curvilinear running will never be as fast as straight running, the addition of lateral banking may promote a reorientation of the ground reaction force vector leading to a more favorable combination of horizontal and vertical components. As well banking may be able to provide a protective mechanism for athletes if it can be incorporated in footwear, opening up a wealth of possibilities. However, no studies have determined how banking affects the kinematics and kinetics of the lower extremity during lateral sport movements. Therefore the purpose of this study was to determine how different lateral bank angles would affect kinematic and kinetic measures of the lower extremities during lateral sport movements.
2. Methods Data were collected on 10 recreational university athletes with a mean body weight of 750 ± 54 N and height of 1.79 ± 0.07 m. Before participating in the study, all volunteers were required to read and sign a consent form approved by the university ethics committee, as well as acknowledge that they had no lower extremity injury in the past year. Each subject performed both a v-cut as well as side shuffle movement on 3 different banked surfaces. The three different banks consisted of a flat surface (0° bank), a surface with a bank angle of 10° and a surface with a bank angle of 20° (Fig. 1). All surfaces were constructed of the same plywood material and were securely adhered to the force platform during testing. During each movement three dimensional force data was collected using a force platform (Kistler AG, Winterthur, Switzerland) mounted in the centre of a 30 meter lab runway. The force platform collected data at 2400 Hz and each subject was required to land with their right foot in the centre of the force platform (bank surface) during each movement. For the v-cut, the athlete performed the movement by running forward at a 45° angle relative to the force platform and lab runway, planting their right foot in the centre of the force platform and cutting out to their left at a 45° angle (Fig. 2). For the side shuffle, the athlete moved laterally to their right, planted with their right foot in the centre of the force platform and exited to their left, in the opposite direction with which they entered, all while facing the same forward direction (Fig. 2). The participants were instructed to perform each movement with maximal effort and were given practice before testing to ensure proper movement technique and confidence performing the movements on each banking surface. Three dimensional kinematic data of the right lower limb was collected during each movement. The forefoot, rearfoot and shank were defined by attaching retro-reflective markers, with a diameter of 19 mm to each segment using medical adhesive and glue (when the markers were attached to the shoe). Three markers per segment were used, attached to the following locations: head of the fibula, upper tibial crest, distal lateral lower leg, proximal shoe heel, distal shoe heel, lateral side of the shoe below the lateral mallelous, on the shoe at the location of the medial side of the first phalanx, distal side of the second phalanx and distal part of the fifth phalanx (Fig. 3). Eight high speed digital cameras (Motion analysis Corp, Santa Rosa, California) operating at a sampling frequency of 240 Hz were used to capture the motion of the markers during the trials, with the system being calibrated to an accuracy defined by a 3-D residual below 0.65.
Fig. 1. Photographs of the three banking conditions.
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Fig. 2. Diagram of the v-cut and side shuffle movements performed in the experiment.
Fig. 3. Photographs of the marker placement used during testing.
The metatarsophalangeal (MTP), ankle and knee joint centre were determined using a standing neutral trial with additional markers placed on the head of the first and fifth metatarsal (MTP), the medial and lateral malleolous (ankle) and the lateral knee and centre of patella (knee). The kinematic and kinetic data were imported in Kintrak 7.0.25 (University of Calgary, Calgary, Canada) for analysis and filtered using cutoff frequencies of 24 and 100 Hz respectively with a fourth order low pass butterworth filter. For joint moments, the internal resultant joint moments were calculated using an inverse dynamics approach. All comparisons were made between the two banking conditions (10° and 20° bank) and the neutral condition (0° bank) using a repeated measures ANOVA at a significance level of 0.05, with a post hoc analysis being employed to determine where any differences occurred. For kinematic data, peak ankle inversion, rearfoot eversion, forefoot eversion and torsion angle (forefoot relative to rearfoot) angle were calculated during the stance phase for both the v-cut and side shuffle. Knee and ankle angular impulse as well as the magnitude and orientation of the ground reaction force vector were also compared. 3. Results The effect of banking angle on the kinematics and kinetics of the lower extremity can be seen in Tables 1 and 2 for the v-cut and side shuffle respectively. 3.1. Kinematics Kinematic curves for the ankle joint, rearfoot, forefoot and foot torsion can be seen in Fig. 4. The ankle inversion angle was significantly reduced in both the 10° bank and the 20° bank for the v-cut (p = .014 and p = .001, respectively) and side shuffle (p < .001 for both bank angles) compared to the 0° bank angle. During the v-cut, the rearfoot eversion angle was significantly increased (p < .001 for both banks) and the forefoot eversion angle was significantly increased as the banking angle increased (p < .001 for the 10° bank and p = .006 for the 20° bank). Similarly during the side shuffle,
Table 1 Average data (standard deviation) values during the v-cut for the 0°, 10°, and 20° banking conditions. Bold values indicate a significant difference from the flat surface (0° bank). Bank
Ankle angular impulse (Nms)
Knee angular impulse (Nms)
Peak angles (deg)
Vertical
Horizontal
Transverse plane
Frontal plane
Sagittal plane
Transverse plane
Frontal plane
Sagittal plane
280(48) 287(57) 268(42)
166(21) 204(34) 219(20)
16.3(4.1) 15.4(3.8) 11.2(2.5)
12.6(2.9) 10.9(3.7) 10.2(3.2)
27.9(10.3) 32.0(11.5) 33.8(8.5)
5.0(3.4) 5.7(3.7) 4.6(2.8)
14.1(7.4) 16.8(9.3) 18.1(6.9)
13.4(9.6) 16.1(9.4) 13.4(8.5)
Ankle eversion 31.5(6.9) 26.8(6.5) 22.7(4.0)
Rearfoot eversion
Forefoot eversion
Torsion
1.0(4.9) 8.7(5.5) 15.4(5.1)
4.1(5.9) 6.7(4.9) 9.9(5.7)
13.0(3.6) 10.9(3.8) 8.3(4.0)
Table 2 Average data (standard deviation) values during the side shuffle for the 0°, 10o, and 20o banking conditions. Bold values indicate a significant difference from the flat surface (0o bank). Bank
0 10 20
Ground reaction impulse (Ns)
Ankle angular impulse (Nms)
Knee angular impulse (Nms)
Peak angles (deg)
Vertical
Horizontal
Transverse plane
Frontal plane
Sagittal plane
Transverse plane
Frontal plane
sagittal plane
386(50) 369(50) 325(43)
238(44) 263(29) 270(41)
25.1(7.8) 22.3(5.2) 16.7(5.1)
15.8(4.0) 11.5(4.0) 12.5(6.5)
41.4(13.1) 47.9(14.1) 46.7(15.7)
6.9(3.0) 7.8(4.4) 6.7(3.0)
15.3(10.4) 16.1(10.4) 16.5(8.8)
21.2(11.9) 17.4(11.7) 12.9(5.1)
Ankle eversion 31.6(3.7) 26.7(4.6) 21.0(4.5)
Rearfoot eversion
Forefoot eversion
Torsion
1.4(5.6) 8.7(5.2) 16.3(6.4)
10.8(6.2) 1.5(3.7) 10.9(5.3)
18.7(7.7) 17.5(5.4) 14.7(5.4)
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0 10 20
Ground reaction impulse (Ns)
101
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Fig. 4. Ankle eversion, rearfoot eversion, forefoot eversion and torsion angle during the (a) v-cut and (b) side shuffle movement. Data represent average values from all subjects normalized over stance phase.
the rearfoot eversion angle was also increased significantly (p < .001 for both banks) and the forefoot eversion angle was significantly increased as the banking angle was increased (p < .001 for both banking conditions). The result of changing rearfoot and forefoot angle with increasing bank angle led to a decrease in the amount of foot torsion (forefoot angle relative to rearfoot angle) for both bank angles during the v-cut (p = .007 for 10° bank and p = .003 for the 20° bank) and was significantly reduced for the 20° bank during the sideshuffle (p = .02). 3.2. Kinetics During the v-cut, the horizontal component of the ground reaction impulse was significantly increased in the 10° (p < .001) and 20° (p < .001) bank conditions, while the magnitude of the ground reaction force was not changed. For the side shuffle, the horizontal ground reaction impulse was significantly increased for the 10° (p = .008) and 20° (p < .001) bank conditions, as well the vertical component of the ground reaction impulse was significantly reduced in the 20° bank (p = .002). The magnitude of the ground reaction impulse was unchanged for both bank conditions. 3.3. Joint moments Ankle joint moment curves can be seen in Fig. 5. The transverse plane angular impulse was significantly reduced with the 20° bank during the v-cut (p = .02) and for the 10° and 20° bank for the side shuffle (p = .05 and p < .001). The frontal plane angular impulse was significantly reduced in both the 10° (p = .038) and 20° bank (p = .025) for the v-cut and for the 10o bank during the side shuffle (p < .001). In the sagittal plane an increase in angular impulse was seen for the 10° and 20° bank during the v-cut (p = .016 and p < .001) and during the side shuffle (p = .005 and p = .008). Knee joint moment curves can be seen in Fig. 6. During the v-cut, the 20° bank produced significantly greater angular impulse in the frontal plane compared to the flat surface (p = .02). No significant differences were seen between the flat surface and the two banks at the knee joint during the side shuffle. Using the kinematic data as well as the kinetic data, the moment arm during each movement was calculated as the perpendicular distance from the ground reaction force vector to both the ankle and knee joint center (Fig. 7). In the transverse and frontal plane the moment arm at the ankle joint were significantly reduced in the 10° (p < .001) and 20° (p < .001) bank angle during the v-cut. During the side shuffle, the 10° bank had a significantly lower ankle moment arm in the transverse (p < .001) and frontal (p = .001) plane while the 20° bank produced a smaller moment arm in the transverse
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Fig. 5. Ankle transverse, frontal and sagittal plane joint moments during the (a) v-cut and (b) side shuffle movement. Data represent average values from all subjects normalized over stance phase.
Fig. 6. Knee transverse, frontal and sagittal plane joint moments during the (a) v-cut and (b) side shuffle movement. Data represent average values from all subjects normalized over stance phase.
plane (p < .001). For the knee joint the only significant differences seen were during the v-cut, as the 20° bank produced a significantly greater moment arm in the frontal plane (p = .05).
4. Discussion One of the main goals of sport research is to examine methods to maximize performance, while minimizing the risk of injury to the athlete. There are many aspects of curvilinear running and cutting movements that can limit the performance of the athlete, however the implementation of banking
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Fig. 7. Average ankle (left column) and knee (right column) moment arm values for the v-cut (top row) and side shuffle (bottom row) for the three external banking angles. Data represent average values from all subjects. Solid black horizontal lines indicate a significant difference between conditions.
may reduce some of these limitations, maximizing athletic performance. Banking could also provide a protective mechanism, placing the foot and ankle in orientations that keep them out of dangerous orientations. This study sought to determine the effect of two banking angles on the kinematics and kinetics of the lower extremity during two athletic cutting maneuvers. 4.1. Injury The risk of ankle injury is one of primary concern during sports that involve cutting, stopping and rotating movements since these movements are high risk in terms of ankle sprains (Stacoff, Steger, & Stussi, 1993). It has been estimated that 90% of all ligamentous injury to the ankle are caused by internal rotation and inversion of the ankle joint (Stacoff et al., 1993). Implementation of both the 10° and 20° lateral bank, reduced the amount of ankle inversion which could cause a reduction in ankle sprain injury risk by preventing the ankle joint from entering into ranges of motion where ankle ligaments may be prone to injury. In addition to limiting the amount of ankle inversion, a reduction of ankle joint angular impulse in the transverse and frontal plane during cutting movements may lead to a reduction in these ankle joint injuries. When examining the ankle joint loading during the cutting movements, banking resulted in reductions of the ankle angular impulse by up to 31% in the transverse plane and up to 19% in the frontal plane for the v-cut, with reductions of angular impulse of up to 33% in the transverse plane and 27% in the frontal plane during the side shuffle. While it is not known how much load is passed on to the ligament structures in the ankle joint during these cutting movements, it is safe to assume that as the joint angular impulse decreases, the likelihood of joint injury also decreases. The addition of the bank angle also reduced the amount of torsion of the foot (forefoot inversion with reference to the rearfoot). Little is known about the relevance of torsion in the context of injuries; it is assumed that an increase in torsion during landing and cutting movements decreases the ankle inversion and therefore the risk of ankle injuries (Stacoff, Kaelin, Stuessi, & Segesser, 1990; Stacoff et al., 1993). In the current study, for both movements the peak torsion angle decreased with
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increasing banking angle while the ankle inversion angles also decreased. The midfoot, where torsion occurs, and the ankle are the two ‘‘joints’’ that determine the position of the shank relative to the forefoot, which is the main contact point between body and ground for the analyzed movements. A decrease in both ankle and torsion angle indicated that with increased banking, the forefoot is more aligned with the shank through the bank. Therefore, less torsion is required to keep the ankle in a position safe from injuries. During the side shuffle maximal torsion was reached at approximately 10% of stance which was just slightly before the maximal ankle inversion occurred. Therefore, torsion could be protecting the ankle from extreme inversion angles. For the v-cut, however, the peak torsion angle occurred after 50% of stance while the peak ankle eversion angle was within the first 25%, indicating that the ankle protection through torsion is not available for this movement. In terms of the knee joint, plant and cut movements similar to the movements used in this study have been proposed as possible mechanisms of ACL injury (Baker, 1990; Myklebust, Maehlum, Engebretsen, Strand, & Solheim, 1997; Myklebust, Maehlum, Holm, & Bahr, 1998). It was initially thought that the bank angles utilized in the study could potentially led to a reduction in knee joint loading, specifically in the frontal plane, due to many studies that have shown a reduction in frontal plane loading by utilizing lateral shoe wedges (Crenshaw, Pollo, & Calton, 2000; Kerrigan et al., 2002; Mundermann et al., 2003; Fisher et al., 2007; Kakihuna et al., 2005). However in the present study it was somewhat concerning that impulses in the frontal plane increased 28% during the v-cut with the 20° bank. The different effect that the banking platforms had on the knee joint compared to the in-shoe wedges may be due to the greater bank angles used in the present study or the different cutting movements employed. The studies incorporating the lateral wedges mainly use wedges with much smaller angles usually around 5°, with a maximum angle of 10°. Also most studies using wedges had their subjects walking or running in a straight line, so it may be the fact that the athletes in the present study were performing cutting movements at maximal effort which caused the increase in loading. The reduction of the ankle joint loading in the transverse and frontal planes was due to the alignment of the foot and shank during touchdown. When comparing the magnitude of the ground reaction impulse vector across conditions no significant differences were seen, therefore the changes in moment and angular impulse were due to the positioning of the limbs. The ankle inversion angle was reduced by adding a bank angle in both the v-cut and side shuffle which caused a reduction in the moments by reducing the moment arm, causing the ground reaction force vector to pass closer to the ankle joint center. This re-alignment of joints and thus reduction of moment arms was enhanced with the larger bank angle. While the addition of banking caused a reduction in the ankle joint moment arm, changes in the knee joint moment arm were not as clear. During the side shuffle the knee joint moment arm stayed constant, while during the v-cut an increase in moment arm only occurred in the frontal plane with the 20° bank. This increase in moment arm during the v-cut with the 20° bank caused the loading at the joint to increase, leading to an increase in joint loading while keeping the ground reaction force constant.
4.2. Performance In sport, athletes will always strive to attain maximal performance, and incorporation of banking elements may assist in attaining increases in performance. The horizontal ground reaction impulse was significantly increased with bank angle for both movements. The increase in horizontal impulse also came with a reduction of vertical ground reaction impulse, re-orienting the ground reaction vector to a much more advantageous position. The reorientation of the ground reaction force has been seen in previous studies (Chang & Kram, 2007) and would allow the athlete to perform quicker horizontal movements. An increase in angular impulse in the sagittal plane was also seen with the addition of the banks for the ankle joint and remained unchanged for the knee joint for both movements. This plane has been thought to be the plane associated with performance and this increased impulse could assist in dorsi and plantar flexion of the foot, leading to an increase in performance.
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4.3. Bank angle As bank angle increased, systematic changes in injury and performance specific variables were seen. The general trend was that these changes were amplified with the 20° bank compared to the 10° bank. This raises the question as to whether further increases in bank angle will result in further decreases in ankle joint loading and increases in variables associated with performance. It is important to also address that the 20° bank resulted in significant increases in knee joint loading in the frontal plane. Further increases in bank angle will likely lead to even larger knee joint loading, possibly raising the risk of knee injury. From the data in the current study it appears as though the 10° bank may be the optimal bank, in that it decreases ankle joint loading, as well as increases specific performance variables while not increasing frontal plane knee joint loading. As well only two movements were tested in the current investigation. Further studies should be conducted on the effect that bank angle has on other common athletic movements such as a straight run as well as pivoting motions.
5. Conclusion Banking had a pronounced effect, notably on the ankle joint. As banking angle increased the amount of joint loading in the transverse and frontal planes decreased likely leading to a reduction in risk of injury. This reduction of joint loading was caused by an altered alignment of the foot and shank, placing these segments in positions less likely for injury. There was an increase in knee joint loading in the frontal plane which may lead to an increase in knee injury, but this was only with the 20° bank during the v-cut. Conversely loading in the sagittal plane at the ankle joint increased with banking and coupled with a reorientation of the ground reaction vector may facilitate a performance increase.
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Contents lists available at ScienceDirect
Human Movement Science journal homepage: www.elsevier.com/locate/humov
The effect of lateral banking on the kinematics and kinetics of the lower extremity during lateral cutting movements John W. Wannop ⇑, Eveline S. Graf, Darren J. Stefanyshyn Human Performance Lab, University of Calgary, Canada
a r t i c l e
i n f o
Article history: Available online 26 September 2013 PsycINFO classification: 3720 Keywords: Joint loading Banking Kinematics Kinetics Lower extremity
a b s t r a c t There are many aspects of cutting movements that can limit performance, however, the implementation of lateral banking may reduce some of these limitations. Banking could provide a protective mechanism, placing the foot and ankle in orientations that keep them out of dangerous positions. This study sought to determine the effect of two banking angles on the kinematics and kinetics of the lower extremity during two athletic maneuvers. Kinematic and kinetic data were collected on 10 recreational athletes performing v-cuts and side shuffle movements on different banked surfaces (0°, 10°, 20°). Each sample surface was rigidly attached to the force platform. Joint moments were calculated and compared between conditions using a repeated measures ANOVA. Banking had a pronounced effect on the ankle joint. As banking increased, the amount of joint loading in the transverse and frontal planes decreased likely leading to a reduction in injury risk. Also an increase in knee joint loading in the frontal plane was seen during the 20° bank during the v-cut. Conversely loading in the sagittal plane at the ankle joint increased with banking and coupled with a reorientation of the ground reaction vector may facilitate a performance increase. The current study indicates that the 10° bank may be the optimal bank, in that it decreases ankle joint loading, as well as increases specific performance variables while not increasing frontal plane
⇑ Corresponding author. Address: Human Performance Laboratory, University of Calgary, Faculty of Kinesiology, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada. Tel.: +1 403 220 7119; fax: +1 403 284 3553. E-mail address: [email protected] (J.W. Wannop). 0167-9457/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.humov.2013.07.020
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knee joint loading. If banking could be incorporated in footwear it may be able to provide a protective mechanism for athletes. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction 1.1. Injury Some of the most common injuries in sports such as basketball occur in the lower extremity (35.9– 92%), with the ankle and foot accounting for majority of these injuries (16.6–44%), followed by the knee (5–20%) (Harmer, 2005; Hikey, Fricker, & McDonaled, 1997; Messina, Farney, & DeLee, 1999; Taylor & Attia, 2000; Zvijac & Thompson, 1996). A large percentage of ankle injuries are inversion ankle sprains (22–65%) (Harmer, 2005), with the primary cause thought to be an excessive inversion moment, which exceeds the internal eversion moment provided by the peroneal muscles when the ankle is in a plantarflexed and inverted position (Stacoff, Steger, Stussi, & Reinschmidt, 1996). Recently, footwear companies have considered incorporating lateral banking elements into their footwear, which raises the lateral aspect of the foot relative to the medial aspect. In theory incorporating lateral banking elements has the potential to reduce inversion ankle sprains by reducing the amount of ankle inversion during plantarflexion, keeping the ankle joint further away from the limit of its range of motion where ankle ligaments may be prone to injury. Banking could also allow additional time for the peroneal muscles to react and provide lateral support to prevent ankle sprain at the crucial time immediately after foot strike (Simpson, Shewokis, Alduwaisan, & Reeves, 1992). Banking also has the potential of reducing the loading that the ankle joint experiences, specifically the inversion moment during athletic movements. During a side cut, loading is oriented on the medial aspect of the foot and forefoot (Queen, Haynes, Hardaker, & Garrett, 2007). Banking could invoke a lateral shift in the centre of pressure, reducing the ankle joint moment arm in the frontal plane, thereby reducing the inversion moment that potentially leads to ankle injury (Shelburne, Torry, Steadman, & Pandy, 2008). As well theoretical calculations by Greene (1987) clearly showed that banking can decrease the peroneal tendon force required to stabilize the ankle joint, and Alexander (1991) stated that aligning the resultant force vector with the leg generally leads to favorable minimization in joint moments and musculoskeletal stresses. The knee joint is also frequently injured in sport and while benefits to the ankle joint are plentiful, benefits to the knee joint may also result from banking. Patellofemoral pain is thought to occur when frontal plane moments are large (Stefanyshyn, Stergiou, Lun, Meeuwisse, & Worobets, 2006), and lateral wedging (banking) has been shown to reduce these frontal plane moments (Fisher, Dyrby, Mundermann, Morag, & Andriacchi, 2007; Kakihuna et al., 2005; Kerrigan et al., 2002; Mundermann, Nigg, Humble, & Stefanyshyn, 2003). However the direct influence of banking on knee injuries is not as clear as for the ankle joint. 1.2. Performance It has been shown that flat curved running is slower than straight running with a tighter turn leading to a greater decrease in performance. Cutting maneuvers can also be considered running with a very small radius of curvature (Chang & Kram, 2007; Jain, 1980). In sport, greater running speeds are achieved with a greater ground reaction force (Weyand, Sternlight, Bellizzi, & Wright, 2000). Recent studies examining curvilinear running have concluded that the same peak resultant force is present compared to straight running; however the direction of the resultant force changes due to the required centripetal acceleration providing a smaller vertical component and a greater horizontal component (Chang & Kram, 2007). A smaller vertical force vector requires an increase in ground contact time to generate vertical impulse to support body weight over
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the entire stride (Usherwood & Wilson, 2006), with this increase in contact time leading to a decrease in performance. Additionally, force generation by leg extensor muscles may be compromised when the joints are not aligned. A theoretical model has shown performance increases of up to 10% for banked situations with performance decreases of up to 10% seen with ankle eversion of only 30° (Greene, 1987). While curvilinear running will never be as fast as straight running, the addition of lateral banking may promote a reorientation of the ground reaction force vector leading to a more favorable combination of horizontal and vertical components. As well banking may be able to provide a protective mechanism for athletes if it can be incorporated in footwear, opening up a wealth of possibilities. However, no studies have determined how banking affects the kinematics and kinetics of the lower extremity during lateral sport movements. Therefore the purpose of this study was to determine how different lateral bank angles would affect kinematic and kinetic measures of the lower extremities during lateral sport movements.
2. Methods Data were collected on 10 recreational university athletes with a mean body weight of 750 ± 54 N and height of 1.79 ± 0.07 m. Before participating in the study, all volunteers were required to read and sign a consent form approved by the university ethics committee, as well as acknowledge that they had no lower extremity injury in the past year. Each subject performed both a v-cut as well as side shuffle movement on 3 different banked surfaces. The three different banks consisted of a flat surface (0° bank), a surface with a bank angle of 10° and a surface with a bank angle of 20° (Fig. 1). All surfaces were constructed of the same plywood material and were securely adhered to the force platform during testing. During each movement three dimensional force data was collected using a force platform (Kistler AG, Winterthur, Switzerland) mounted in the centre of a 30 meter lab runway. The force platform collected data at 2400 Hz and each subject was required to land with their right foot in the centre of the force platform (bank surface) during each movement. For the v-cut, the athlete performed the movement by running forward at a 45° angle relative to the force platform and lab runway, planting their right foot in the centre of the force platform and cutting out to their left at a 45° angle (Fig. 2). For the side shuffle, the athlete moved laterally to their right, planted with their right foot in the centre of the force platform and exited to their left, in the opposite direction with which they entered, all while facing the same forward direction (Fig. 2). The participants were instructed to perform each movement with maximal effort and were given practice before testing to ensure proper movement technique and confidence performing the movements on each banking surface. Three dimensional kinematic data of the right lower limb was collected during each movement. The forefoot, rearfoot and shank were defined by attaching retro-reflective markers, with a diameter of 19 mm to each segment using medical adhesive and glue (when the markers were attached to the shoe). Three markers per segment were used, attached to the following locations: head of the fibula, upper tibial crest, distal lateral lower leg, proximal shoe heel, distal shoe heel, lateral side of the shoe below the lateral mallelous, on the shoe at the location of the medial side of the first phalanx, distal side of the second phalanx and distal part of the fifth phalanx (Fig. 3). Eight high speed digital cameras (Motion analysis Corp, Santa Rosa, California) operating at a sampling frequency of 240 Hz were used to capture the motion of the markers during the trials, with the system being calibrated to an accuracy defined by a 3-D residual below 0.65.
Fig. 1. Photographs of the three banking conditions.
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Fig. 2. Diagram of the v-cut and side shuffle movements performed in the experiment.
Fig. 3. Photographs of the marker placement used during testing.
The metatarsophalangeal (MTP), ankle and knee joint centre were determined using a standing neutral trial with additional markers placed on the head of the first and fifth metatarsal (MTP), the medial and lateral malleolous (ankle) and the lateral knee and centre of patella (knee). The kinematic and kinetic data were imported in Kintrak 7.0.25 (University of Calgary, Calgary, Canada) for analysis and filtered using cutoff frequencies of 24 and 100 Hz respectively with a fourth order low pass butterworth filter. For joint moments, the internal resultant joint moments were calculated using an inverse dynamics approach. All comparisons were made between the two banking conditions (10° and 20° bank) and the neutral condition (0° bank) using a repeated measures ANOVA at a significance level of 0.05, with a post hoc analysis being employed to determine where any differences occurred. For kinematic data, peak ankle inversion, rearfoot eversion, forefoot eversion and torsion angle (forefoot relative to rearfoot) angle were calculated during the stance phase for both the v-cut and side shuffle. Knee and ankle angular impulse as well as the magnitude and orientation of the ground reaction force vector were also compared. 3. Results The effect of banking angle on the kinematics and kinetics of the lower extremity can be seen in Tables 1 and 2 for the v-cut and side shuffle respectively. 3.1. Kinematics Kinematic curves for the ankle joint, rearfoot, forefoot and foot torsion can be seen in Fig. 4. The ankle inversion angle was significantly reduced in both the 10° bank and the 20° bank for the v-cut (p = .014 and p = .001, respectively) and side shuffle (p < .001 for both bank angles) compared to the 0° bank angle. During the v-cut, the rearfoot eversion angle was significantly increased (p < .001 for both banks) and the forefoot eversion angle was significantly increased as the banking angle increased (p < .001 for the 10° bank and p = .006 for the 20° bank). Similarly during the side shuffle,
Table 1 Average data (standard deviation) values during the v-cut for the 0°, 10°, and 20° banking conditions. Bold values indicate a significant difference from the flat surface (0° bank). Bank
Ankle angular impulse (Nms)
Knee angular impulse (Nms)
Peak angles (deg)
Vertical
Horizontal
Transverse plane
Frontal plane
Sagittal plane
Transverse plane
Frontal plane
Sagittal plane
280(48) 287(57) 268(42)
166(21) 204(34) 219(20)
16.3(4.1) 15.4(3.8) 11.2(2.5)
12.6(2.9) 10.9(3.7) 10.2(3.2)
27.9(10.3) 32.0(11.5) 33.8(8.5)
5.0(3.4) 5.7(3.7) 4.6(2.8)
14.1(7.4) 16.8(9.3) 18.1(6.9)
13.4(9.6) 16.1(9.4) 13.4(8.5)
Ankle eversion 31.5(6.9) 26.8(6.5) 22.7(4.0)
Rearfoot eversion
Forefoot eversion
Torsion
1.0(4.9) 8.7(5.5) 15.4(5.1)
4.1(5.9) 6.7(4.9) 9.9(5.7)
13.0(3.6) 10.9(3.8) 8.3(4.0)
Table 2 Average data (standard deviation) values during the side shuffle for the 0°, 10o, and 20o banking conditions. Bold values indicate a significant difference from the flat surface (0o bank). Bank
0 10 20
Ground reaction impulse (Ns)
Ankle angular impulse (Nms)
Knee angular impulse (Nms)
Peak angles (deg)
Vertical
Horizontal
Transverse plane
Frontal plane
Sagittal plane
Transverse plane
Frontal plane
sagittal plane
386(50) 369(50) 325(43)
238(44) 263(29) 270(41)
25.1(7.8) 22.3(5.2) 16.7(5.1)
15.8(4.0) 11.5(4.0) 12.5(6.5)
41.4(13.1) 47.9(14.1) 46.7(15.7)
6.9(3.0) 7.8(4.4) 6.7(3.0)
15.3(10.4) 16.1(10.4) 16.5(8.8)
21.2(11.9) 17.4(11.7) 12.9(5.1)
Ankle eversion 31.6(3.7) 26.7(4.6) 21.0(4.5)
Rearfoot eversion
Forefoot eversion
Torsion
1.4(5.6) 8.7(5.2) 16.3(6.4)
10.8(6.2) 1.5(3.7) 10.9(5.3)
18.7(7.7) 17.5(5.4) 14.7(5.4)
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0 10 20
Ground reaction impulse (Ns)
101
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Fig. 4. Ankle eversion, rearfoot eversion, forefoot eversion and torsion angle during the (a) v-cut and (b) side shuffle movement. Data represent average values from all subjects normalized over stance phase.
the rearfoot eversion angle was also increased significantly (p < .001 for both banks) and the forefoot eversion angle was significantly increased as the banking angle was increased (p < .001 for both banking conditions). The result of changing rearfoot and forefoot angle with increasing bank angle led to a decrease in the amount of foot torsion (forefoot angle relative to rearfoot angle) for both bank angles during the v-cut (p = .007 for 10° bank and p = .003 for the 20° bank) and was significantly reduced for the 20° bank during the sideshuffle (p = .02). 3.2. Kinetics During the v-cut, the horizontal component of the ground reaction impulse was significantly increased in the 10° (p < .001) and 20° (p < .001) bank conditions, while the magnitude of the ground reaction force was not changed. For the side shuffle, the horizontal ground reaction impulse was significantly increased for the 10° (p = .008) and 20° (p < .001) bank conditions, as well the vertical component of the ground reaction impulse was significantly reduced in the 20° bank (p = .002). The magnitude of the ground reaction impulse was unchanged for both bank conditions. 3.3. Joint moments Ankle joint moment curves can be seen in Fig. 5. The transverse plane angular impulse was significantly reduced with the 20° bank during the v-cut (p = .02) and for the 10° and 20° bank for the side shuffle (p = .05 and p < .001). The frontal plane angular impulse was significantly reduced in both the 10° (p = .038) and 20° bank (p = .025) for the v-cut and for the 10o bank during the side shuffle (p < .001). In the sagittal plane an increase in angular impulse was seen for the 10° and 20° bank during the v-cut (p = .016 and p < .001) and during the side shuffle (p = .005 and p = .008). Knee joint moment curves can be seen in Fig. 6. During the v-cut, the 20° bank produced significantly greater angular impulse in the frontal plane compared to the flat surface (p = .02). No significant differences were seen between the flat surface and the two banks at the knee joint during the side shuffle. Using the kinematic data as well as the kinetic data, the moment arm during each movement was calculated as the perpendicular distance from the ground reaction force vector to both the ankle and knee joint center (Fig. 7). In the transverse and frontal plane the moment arm at the ankle joint were significantly reduced in the 10° (p < .001) and 20° (p < .001) bank angle during the v-cut. During the side shuffle, the 10° bank had a significantly lower ankle moment arm in the transverse (p < .001) and frontal (p = .001) plane while the 20° bank produced a smaller moment arm in the transverse
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Fig. 5. Ankle transverse, frontal and sagittal plane joint moments during the (a) v-cut and (b) side shuffle movement. Data represent average values from all subjects normalized over stance phase.
Fig. 6. Knee transverse, frontal and sagittal plane joint moments during the (a) v-cut and (b) side shuffle movement. Data represent average values from all subjects normalized over stance phase.
plane (p < .001). For the knee joint the only significant differences seen were during the v-cut, as the 20° bank produced a significantly greater moment arm in the frontal plane (p = .05).
4. Discussion One of the main goals of sport research is to examine methods to maximize performance, while minimizing the risk of injury to the athlete. There are many aspects of curvilinear running and cutting movements that can limit the performance of the athlete, however the implementation of banking
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Fig. 7. Average ankle (left column) and knee (right column) moment arm values for the v-cut (top row) and side shuffle (bottom row) for the three external banking angles. Data represent average values from all subjects. Solid black horizontal lines indicate a significant difference between conditions.
may reduce some of these limitations, maximizing athletic performance. Banking could also provide a protective mechanism, placing the foot and ankle in orientations that keep them out of dangerous orientations. This study sought to determine the effect of two banking angles on the kinematics and kinetics of the lower extremity during two athletic cutting maneuvers. 4.1. Injury The risk of ankle injury is one of primary concern during sports that involve cutting, stopping and rotating movements since these movements are high risk in terms of ankle sprains (Stacoff, Steger, & Stussi, 1993). It has been estimated that 90% of all ligamentous injury to the ankle are caused by internal rotation and inversion of the ankle joint (Stacoff et al., 1993). Implementation of both the 10° and 20° lateral bank, reduced the amount of ankle inversion which could cause a reduction in ankle sprain injury risk by preventing the ankle joint from entering into ranges of motion where ankle ligaments may be prone to injury. In addition to limiting the amount of ankle inversion, a reduction of ankle joint angular impulse in the transverse and frontal plane during cutting movements may lead to a reduction in these ankle joint injuries. When examining the ankle joint loading during the cutting movements, banking resulted in reductions of the ankle angular impulse by up to 31% in the transverse plane and up to 19% in the frontal plane for the v-cut, with reductions of angular impulse of up to 33% in the transverse plane and 27% in the frontal plane during the side shuffle. While it is not known how much load is passed on to the ligament structures in the ankle joint during these cutting movements, it is safe to assume that as the joint angular impulse decreases, the likelihood of joint injury also decreases. The addition of the bank angle also reduced the amount of torsion of the foot (forefoot inversion with reference to the rearfoot). Little is known about the relevance of torsion in the context of injuries; it is assumed that an increase in torsion during landing and cutting movements decreases the ankle inversion and therefore the risk of ankle injuries (Stacoff, Kaelin, Stuessi, & Segesser, 1990; Stacoff et al., 1993). In the current study, for both movements the peak torsion angle decreased with
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increasing banking angle while the ankle inversion angles also decreased. The midfoot, where torsion occurs, and the ankle are the two ‘‘joints’’ that determine the position of the shank relative to the forefoot, which is the main contact point between body and ground for the analyzed movements. A decrease in both ankle and torsion angle indicated that with increased banking, the forefoot is more aligned with the shank through the bank. Therefore, less torsion is required to keep the ankle in a position safe from injuries. During the side shuffle maximal torsion was reached at approximately 10% of stance which was just slightly before the maximal ankle inversion occurred. Therefore, torsion could be protecting the ankle from extreme inversion angles. For the v-cut, however, the peak torsion angle occurred after 50% of stance while the peak ankle eversion angle was within the first 25%, indicating that the ankle protection through torsion is not available for this movement. In terms of the knee joint, plant and cut movements similar to the movements used in this study have been proposed as possible mechanisms of ACL injury (Baker, 1990; Myklebust, Maehlum, Engebretsen, Strand, & Solheim, 1997; Myklebust, Maehlum, Holm, & Bahr, 1998). It was initially thought that the bank angles utilized in the study could potentially led to a reduction in knee joint loading, specifically in the frontal plane, due to many studies that have shown a reduction in frontal plane loading by utilizing lateral shoe wedges (Crenshaw, Pollo, & Calton, 2000; Kerrigan et al., 2002; Mundermann et al., 2003; Fisher et al., 2007; Kakihuna et al., 2005). However in the present study it was somewhat concerning that impulses in the frontal plane increased 28% during the v-cut with the 20° bank. The different effect that the banking platforms had on the knee joint compared to the in-shoe wedges may be due to the greater bank angles used in the present study or the different cutting movements employed. The studies incorporating the lateral wedges mainly use wedges with much smaller angles usually around 5°, with a maximum angle of 10°. Also most studies using wedges had their subjects walking or running in a straight line, so it may be the fact that the athletes in the present study were performing cutting movements at maximal effort which caused the increase in loading. The reduction of the ankle joint loading in the transverse and frontal planes was due to the alignment of the foot and shank during touchdown. When comparing the magnitude of the ground reaction impulse vector across conditions no significant differences were seen, therefore the changes in moment and angular impulse were due to the positioning of the limbs. The ankle inversion angle was reduced by adding a bank angle in both the v-cut and side shuffle which caused a reduction in the moments by reducing the moment arm, causing the ground reaction force vector to pass closer to the ankle joint center. This re-alignment of joints and thus reduction of moment arms was enhanced with the larger bank angle. While the addition of banking caused a reduction in the ankle joint moment arm, changes in the knee joint moment arm were not as clear. During the side shuffle the knee joint moment arm stayed constant, while during the v-cut an increase in moment arm only occurred in the frontal plane with the 20° bank. This increase in moment arm during the v-cut with the 20° bank caused the loading at the joint to increase, leading to an increase in joint loading while keeping the ground reaction force constant.
4.2. Performance In sport, athletes will always strive to attain maximal performance, and incorporation of banking elements may assist in attaining increases in performance. The horizontal ground reaction impulse was significantly increased with bank angle for both movements. The increase in horizontal impulse also came with a reduction of vertical ground reaction impulse, re-orienting the ground reaction vector to a much more advantageous position. The reorientation of the ground reaction force has been seen in previous studies (Chang & Kram, 2007) and would allow the athlete to perform quicker horizontal movements. An increase in angular impulse in the sagittal plane was also seen with the addition of the banks for the ankle joint and remained unchanged for the knee joint for both movements. This plane has been thought to be the plane associated with performance and this increased impulse could assist in dorsi and plantar flexion of the foot, leading to an increase in performance.
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4.3. Bank angle As bank angle increased, systematic changes in injury and performance specific variables were seen. The general trend was that these changes were amplified with the 20° bank compared to the 10° bank. This raises the question as to whether further increases in bank angle will result in further decreases in ankle joint loading and increases in variables associated with performance. It is important to also address that the 20° bank resulted in significant increases in knee joint loading in the frontal plane. Further increases in bank angle will likely lead to even larger knee joint loading, possibly raising the risk of knee injury. From the data in the current study it appears as though the 10° bank may be the optimal bank, in that it decreases ankle joint loading, as well as increases specific performance variables while not increasing frontal plane knee joint loading. As well only two movements were tested in the current investigation. Further studies should be conducted on the effect that bank angle has on other common athletic movements such as a straight run as well as pivoting motions.
5. Conclusion Banking had a pronounced effect, notably on the ankle joint. As banking angle increased the amount of joint loading in the transverse and frontal planes decreased likely leading to a reduction in risk of injury. This reduction of joint loading was caused by an altered alignment of the foot and shank, placing these segments in positions less likely for injury. There was an increase in knee joint loading in the frontal plane which may lead to an increase in knee injury, but this was only with the 20° bank during the v-cut. Conversely loading in the sagittal plane at the ankle joint increased with banking and coupled with a reorientation of the ground reaction vector may facilitate a performance increase.
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