Gait & Posture 40 (2014) 118–122
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Footwear traction and three-dimensional kinematics of level, downhill, uphill and cross-slope walking John W. Wannop *, Jay T. Worobets, Rodrigo Ruiz, Darren J. Stefanyshyn Human Performance Lab, University of Calgary, Canada
A R T I C L E I N F O
A B S T R A C T
Article history: Received 6 June 2013 Received in revised form 3 February 2014 Accepted 3 March 2014
Outdoor activities are a popular form of recreation, with hiking being the most popular outdoor activity as well as being the most prevalent in terms of injury. Over the duration of a hike, trekkers will encounter many different sloped terrains. Not much is known about the required traction or foot-floor kinematics during locomotion on these sloped surfaces, therefore, the purpose was to determine the threedimensional foot-floor kinematics and required traction during level, downhill, uphill and cross-slope walking. Ten participants performed level, uphill, downhill and cross-slope walking along a 198 inclined walkway. Ground reaction force data as well as 3D positions of retro reflective markers attached to the shoe were recorded using a Motion Analysis System. Peak traction coefficients and foot-floor kinematics during sloped walking were compared to level walking. When walking along different sloped surfaces, the required traction coefficients at touchdown were not different from level walking, therefore, the increased likelihood of heel slipping during hiking is potentially due to the presence of loose material (rocks, dirt) on hiking slopes, rather than the overall lack of traction. Differences in required traction were seen at takeoff, with uphill and cross-sloped walking requiring a greater amount of traction compared to level walking. Changes in sagittal plane, frontal plane and transverse plane foot-floor angles were seen while walking on the sloped surfaces. Rapid foot-floor eversion was observed during crossslope walking which could place the hiker at risk of injury with a misstep or if there was a slight slip. ß 2014 Elsevier B.V. All rights reserved.
Keywords: Hiking Sloped walking Traction Slip
1. Introduction Outdoor activities are an extremely popular form of recreation, with hiking being by far the most popular outdoor activity. Over the past two decades hiking popularity has grown substantially with over 73 million Americans hiking each year [1–3]. Relative to other outdoor activities, hiking appears to be the most prevalent in terms of injury occurrence. Many studies have reported hiking injury data, with hiking injuries accounting for up to 46.1% of all outdoor activity injuries [4,5]. Results from retrospective surveys indicate that between 68% and 82% of hikers suffer an injury or illness during a single hike [1,2,6]. The main acute injuries are ankle sprains, which affect between 11% and 47% of hikers, and lacerations/abrasions/fractures due to slip and fall accidents, which affect between 5% and 59% of hikers.
* Corresponding author at: Human Performance Laboratory, University of Calgary, Faculty of Kinesiology, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4. Tel.: +1 403 220 7003; fax: +1 403 284 3553. E-mail address: [email protected] (J.W. Wannop). http://dx.doi.org/10.1016/j.gaitpost.2014.03.004 0966-6362/ß 2014 Elsevier B.V. All rights reserved.
The high prevalence of ankle injuries in addition to slip and fall injuries are intuitively due to the fact that hikes are rarely performed on a level surface. Over the duration of a hike, trekkers will encounter many different sloped terrains including uphill and downhill, in addition to cross-sloped surfaces (which are defined as walking perpendicular with respect to the slope of the surface). While data on hiking on these different sloped surfaces is scarce, some studies have investigated the kinematic (step length, joint angles) and kinetic (ground reaction forces, ankle and knee joint loading, required coefficient of friction) differences between walking uphill and downhill compared to level ground locomotion. Most of this research has focused on downhill walking [7–9]; fewer articles are available on uphill walking [8,10,11] and cross-slope walking [12]. While these articles provided some biomechanical information on uphill and downhill walking, no information was provided on the kinematics of the shoe/foot relative to the floor. Additionally all of the above mentioned studies only investigated biomechanics in the sagittal plane, yet it is likely that the frontal and transverse planes are more important in terms of ankle injuries [13]. Therefore the purpose of this study was to determine the three-dimensional foot-floor kinematics and required traction during level, downhill, uphill and cross-slope walking.
J.W. Wannop et al. / Gait & Posture 40 (2014) 118–122
2. Methods Ten healthy male participants were recruited for this investigation. The participants had a mean SD height and mass of 1.77 0.08 m and 79.6 6.3 kg. In order to participate in the study, participants were required to be free from lower extremity injury and have a shoe size between US 9 and 11. Informed written consent in accordance with the University’s Ethics Board was obtained from all participants prior to participation. The shoe model used in this study was the Nike Kobe VII (US men’s size 9–11). Even though the test shoe was not an outdoor shoe, the calculated required traction was relevant for the tested hiking movements since no slippage occurred between the shoe and surface during trials. The hiking movements studied were uphill, downhill and crossslope walking. In order to capture motion and ground reaction force data, a ramp apparatus was built and installed in the laboratory. The apparatus consisted of two intersecting walkways: a 3.0 m long walkway inclined at 198 for uphill and downhill walking and a 3.3 m long walkway with a cross-slope inclination of 198 for cross-slope walking (Fig. 1). The intersecting portion of the two walkways was not attached to either walkway, but was instead rigidly bolted to a force platform embedded in the ground. For the uphill walking trials, the participant started from rest, off the ramp on the level ground, at a position such that when they began walking up the ramp, their 3rd footfall was with their right foot as it landed directly over the force platform. To help ensure that this step of interest occurred during constant walking speed, the subject then continued walking 3 more strides past the force platform up to the top of the ramp. For the downhill walking trials, the subject started from rest at the top of the ramp, at a position such that when they began walking down the ramp, their 3rd footfall (a right foot step) landed over the force platform. The subjects walked down the entire ramp during each trial, again to help ensure the step of interest occurred during a constant walking speed. For the cross-slope trials, the subject started from rest at one end of the ramp and walked to the other end of the ramp, ensuring that their 3rd footfall (a right foot step) landed directly over the force platform. The cross-slope procedure was used for two conditions: one where the step of interest occurred with the uphill foot and one where the step of interest occurred with the downhill
[(Fig._1)TD$IG]
119
foot. In addition, level ground walking trials were recorded for baseline comparisons. These trials were performed in a similar manner to the ramp trials but were done directly over the surface of the lab (as opposed to a level ramp). The subject started from rest at a position such that their 3rd footfall was with their right foot that landed directly over a force platform embedded in the floor and after this foot strike the subject continued walking for 3 more strides. Each subject performed five walking trials for each movement condition, all at a speed of 1.35 0.07 m/s. The walking speeds were monitored using two infrared timing light gates (Brower Timing Systems, Utah) spaced 1.2 m apart and mounted at hip height. The subjects were given as many practice trials beforehand as necessary to establish their starting position and the correct walking speed. During every trial, ground reaction force data were collected using a Kistler force platform operating at 2000 Hz (Kistler AG, Winterthur, Switzerland). Three retro-reflective markers with a diameter of 19 mm were attached with double sided tape to the rear portion of the right shoe on the posterior shoe heel, distal shoe heel and lateral shoe heel (Fig. 1). The 3D positions of each marker were recorded during trials using an eight camera Motion Analysis System (Motion Analysis Corp., Santa Rosa, California) operating at a frequency of 240 Hz. The motion capture system was calibrated to an accuracy defined by a 3D residual value below 0.6 mm. All data were analyzed using Matlab software (Mathworks, Natick, MA). For angle calculations, the foot angle relative to the floor was calculated, with a zero angle being defined as the shoe flat on the surface, with the shoe anterior–posterior axis aligned with the laboratory coordinate axis representing the direction of motion. Ground reaction force data were used to calculate traction coefficients over the stance phase for each walking condition. This was obtained by using the resultant horizontal force components and dividing them by the vertical force component. Due to the slope of the walking platform, transformations were applied to the raw force plate data by applying a rotation matrix that rotated the force data 198 around the long axis of the force plate in order to place the force data in a coordinate system that was aligned with the sloped platform. All data were compared to the level ground walking condition, with peak angles and traction coefficients at touchdown and toeoff being compared between conditions using a paired-samples ttests and a Holm–Bonferroni sequential correction [14] to account for multiple comparisons (a = 0.05). Therefore, after sequential correction was applied to the ranked p-values, significant differences were determined if a1 < 0.0125, a2 < 0.0167, a3 < 0.025 and a4 < 0.05. 3. Results
Fig. 1. Photograph of the walkway constructed in the laboratory in addition to the marker placement on the shoe.
The traction coefficients and foot-floor angles during level, downhill, uphill, and cross-slope walking are shown in Fig. 2. Touchdown and toe-off peak values are reported in Tables 1 and 2. During initial stance, there were no significant differences between level walking and any of the sloped walking conditions in regards to peak resultant utilized traction coefficients. The time at which these peaks occurred, however, was significantly increased during downhill walking compared to the level condition (p < 0.001). When the traction coefficient was broken into its anterior–posterior and medial–lateral components, significant increases (larger anterior traction) were seen during uphill walking (p < 0.001). All conditions had significant differences in traction in the medial–lateral direction, with the downhill, uphill and crossslope (downhill foot) requiring a greater amount of medial traction (p < 0.001 for all conditions), while the cross-slope (uphill foot) required a greater traction component in the lateral direction (p < 0.001).
[(Fig._2)TD$IG]
J.W. Wannop et al. / Gait & Posture 40 (2014) 118–122
120
Fig. 2. Coefficient of traction (top row) and shoe-floor kinematics (bottom row) during level and sloped walking. Data represent the average of all subjects, normalized from touchdown to toe-off. S-Down represents the lower foot during cross-slope walking, while S-Up represents the upper foot during cross slope walking.
into anterior–posterior components, downhill, side-downhill and side-uphill required significantly less anterior traction (p = 0.001, p = 0.002, p = 0.03) while uphill walking required significantly greater anterior traction (p < 0.001). In terms of medial–lateral traction, downhill, uphill and side-uphill required significantly greater lateral traction (p < 0.001, p = 0.01, p < 0.001) while sidedownhill walking required significantly greater medial traction values (p < 0.001). In terms of foot-floor angles, in the sagittal plane, uphill and side-downhill walking had significantly increased foot-floor plantarflexion angles (p = 0.008, p = 0.011), while in the transverse plane during side-uphill and side-downhill walking the foot was internally rotated (p = 0.018, p = 0.002). During uphill walking the foot was more externally rotated (p = 0.004). Lastly in the frontal plane, the foot was more everted during downhill, uphill and sidedownhill walking (p = 0.001, p < 0.001, p < 0.001).
In terms of foot-floor angles during initial stance, the peak footfloor dorsiflexion angle during uphill and side-uphill walking was significantly reduced compared to level walking (p < 0.001 and p = 0.009, respectively). In the transverse plane, side-uphill walking had an increased peak foot-floor internal rotation angle (p < 0.001), while uphill walking had the trend of an increase in the peak foot-floor external rotation angle (p = 0.043). In the frontal plane, during downhill and side-uphill walking, significant increases in the peak foot-floor inversion angles were present (p = 0.003 and p = 0.010), while during side-downhill walking there was the trend of a greater peak foot-floor eversion angle (p = 0.047). During final stance, traction coefficients were significantly higher during side-uphill walking (p = 0.007), while uphill walking had the trend of a greater required traction compared to the level condition (p = 0.023). When the traction coefficient was broken
Table 1 Peak traction and foot-floor angles during touchdown.
Peak traction coefficient Time at which peak traction occurred [ms] Average traction coefficient over stance AP peak traction coefficient ML peak traction coefficient Sagittal plane [deg] Transverse plane [deg] Frontal plane [deg]
Level
Downhill
Uphill
S-Down
S-Up
0.63 19.7 0.16 S0.50 S0.13 S35.9 S5.4 6.3
0.54 110.8 0.29 S0.51 0.11 S40.2 S9.7 9.1
0.62 22.5 0.37 0.57 0.15 S15.5 S11.9 5.1
0.82 19.5 0.38 S0.47 0.69 S32.1 2.2 S9.6
0.66 18.3 0.38 S0.58 S0.45 S25.9 11.1 10.5
Bold values represent a significant difference from level walking. In the sagittal, transverse and frontal plane positive/negative angles represent plantar/dorsi flexion, internal/ external rotation, inversion/eversion, respectively.
Table 2 Peak traction and foot-floor angles during toe-off.
Peak traction coefficient AP peak traction coefficient ML peak traction coefficient Sagittal plane [deg] Transverse plane [deg] Frontal plane [deg]
Level
Downhill
Uphill
S-Down
S-Up
0.61 0.61 0.09 54.2 S10.9 11.7
0.39 0.23 S0.12 58.7 S11.2 S0.7
0.81 0.87 0.06 73.2 S19.8 S10.5
0.57 0.38 0.50 61.4 5.4 S10.6
0.84 0.43 S0.70 60.0 12.8 15.8
Bold values represent a significant difference from level walking. In the sagittal, transverse and frontal plane positive/negative angles represent plantar/dorsi flexion, internal/ external rotation, inversion/eversion, respectively.
J.W. Wannop et al. / Gait & Posture 40 (2014) 118–122
Over the duration of stance, the average traction coefficient during downhill, uphill, side-downhill and side uphill walking was significantly higher than level walking (p < 0.001 for all conditions compared to the control, Table 1). 4. Discussion The main causes of acute injury in hiking are due to slip and fall injuries [1,2,6]. In general, slipping occurs when the available traction offered by a shoe-surface combination is less than the traction required to perform a given movement [7]. During heeltoe walking, the two points in time where the required traction is largest is immediately after touchdown, and immediately prior to takeoff; if the required traction at touchdown is not met, a heel slip results, if the required traction at takeoff is not met, a toe slip results. In terms of slip and fall accidents, heel slips are far more dangerous than toe slips. During a heel slip, the forward moving centre of mass must be supported by the slipping foot; if this does not happen (the individual is unable to ‘recover their balance’), a fall results. When walking along different sloped surfaces, the required traction coefficients at touchdown were quite similar to level walking. No Differences in the peak traction requirements during downhill walking were present, however, the peak traction value occurred much later in the stance phase (18% of stance) compared to all other movements (
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Footwear traction and three-dimensional kinematics of level, downhill, uphill and cross-slope walking John W. Wannop *, Jay T. Worobets, Rodrigo Ruiz, Darren J. Stefanyshyn Human Performance Lab, University of Calgary, Canada
A R T I C L E I N F O
A B S T R A C T
Article history: Received 6 June 2013 Received in revised form 3 February 2014 Accepted 3 March 2014
Outdoor activities are a popular form of recreation, with hiking being the most popular outdoor activity as well as being the most prevalent in terms of injury. Over the duration of a hike, trekkers will encounter many different sloped terrains. Not much is known about the required traction or foot-floor kinematics during locomotion on these sloped surfaces, therefore, the purpose was to determine the threedimensional foot-floor kinematics and required traction during level, downhill, uphill and cross-slope walking. Ten participants performed level, uphill, downhill and cross-slope walking along a 198 inclined walkway. Ground reaction force data as well as 3D positions of retro reflective markers attached to the shoe were recorded using a Motion Analysis System. Peak traction coefficients and foot-floor kinematics during sloped walking were compared to level walking. When walking along different sloped surfaces, the required traction coefficients at touchdown were not different from level walking, therefore, the increased likelihood of heel slipping during hiking is potentially due to the presence of loose material (rocks, dirt) on hiking slopes, rather than the overall lack of traction. Differences in required traction were seen at takeoff, with uphill and cross-sloped walking requiring a greater amount of traction compared to level walking. Changes in sagittal plane, frontal plane and transverse plane foot-floor angles were seen while walking on the sloped surfaces. Rapid foot-floor eversion was observed during crossslope walking which could place the hiker at risk of injury with a misstep or if there was a slight slip. ß 2014 Elsevier B.V. All rights reserved.
Keywords: Hiking Sloped walking Traction Slip
1. Introduction Outdoor activities are an extremely popular form of recreation, with hiking being by far the most popular outdoor activity. Over the past two decades hiking popularity has grown substantially with over 73 million Americans hiking each year [1–3]. Relative to other outdoor activities, hiking appears to be the most prevalent in terms of injury occurrence. Many studies have reported hiking injury data, with hiking injuries accounting for up to 46.1% of all outdoor activity injuries [4,5]. Results from retrospective surveys indicate that between 68% and 82% of hikers suffer an injury or illness during a single hike [1,2,6]. The main acute injuries are ankle sprains, which affect between 11% and 47% of hikers, and lacerations/abrasions/fractures due to slip and fall accidents, which affect between 5% and 59% of hikers.
* Corresponding author at: Human Performance Laboratory, University of Calgary, Faculty of Kinesiology, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4. Tel.: +1 403 220 7003; fax: +1 403 284 3553. E-mail address: [email protected] (J.W. Wannop). http://dx.doi.org/10.1016/j.gaitpost.2014.03.004 0966-6362/ß 2014 Elsevier B.V. All rights reserved.
The high prevalence of ankle injuries in addition to slip and fall injuries are intuitively due to the fact that hikes are rarely performed on a level surface. Over the duration of a hike, trekkers will encounter many different sloped terrains including uphill and downhill, in addition to cross-sloped surfaces (which are defined as walking perpendicular with respect to the slope of the surface). While data on hiking on these different sloped surfaces is scarce, some studies have investigated the kinematic (step length, joint angles) and kinetic (ground reaction forces, ankle and knee joint loading, required coefficient of friction) differences between walking uphill and downhill compared to level ground locomotion. Most of this research has focused on downhill walking [7–9]; fewer articles are available on uphill walking [8,10,11] and cross-slope walking [12]. While these articles provided some biomechanical information on uphill and downhill walking, no information was provided on the kinematics of the shoe/foot relative to the floor. Additionally all of the above mentioned studies only investigated biomechanics in the sagittal plane, yet it is likely that the frontal and transverse planes are more important in terms of ankle injuries [13]. Therefore the purpose of this study was to determine the three-dimensional foot-floor kinematics and required traction during level, downhill, uphill and cross-slope walking.
J.W. Wannop et al. / Gait & Posture 40 (2014) 118–122
2. Methods Ten healthy male participants were recruited for this investigation. The participants had a mean SD height and mass of 1.77 0.08 m and 79.6 6.3 kg. In order to participate in the study, participants were required to be free from lower extremity injury and have a shoe size between US 9 and 11. Informed written consent in accordance with the University’s Ethics Board was obtained from all participants prior to participation. The shoe model used in this study was the Nike Kobe VII (US men’s size 9–11). Even though the test shoe was not an outdoor shoe, the calculated required traction was relevant for the tested hiking movements since no slippage occurred between the shoe and surface during trials. The hiking movements studied were uphill, downhill and crossslope walking. In order to capture motion and ground reaction force data, a ramp apparatus was built and installed in the laboratory. The apparatus consisted of two intersecting walkways: a 3.0 m long walkway inclined at 198 for uphill and downhill walking and a 3.3 m long walkway with a cross-slope inclination of 198 for cross-slope walking (Fig. 1). The intersecting portion of the two walkways was not attached to either walkway, but was instead rigidly bolted to a force platform embedded in the ground. For the uphill walking trials, the participant started from rest, off the ramp on the level ground, at a position such that when they began walking up the ramp, their 3rd footfall was with their right foot as it landed directly over the force platform. To help ensure that this step of interest occurred during constant walking speed, the subject then continued walking 3 more strides past the force platform up to the top of the ramp. For the downhill walking trials, the subject started from rest at the top of the ramp, at a position such that when they began walking down the ramp, their 3rd footfall (a right foot step) landed over the force platform. The subjects walked down the entire ramp during each trial, again to help ensure the step of interest occurred during a constant walking speed. For the cross-slope trials, the subject started from rest at one end of the ramp and walked to the other end of the ramp, ensuring that their 3rd footfall (a right foot step) landed directly over the force platform. The cross-slope procedure was used for two conditions: one where the step of interest occurred with the uphill foot and one where the step of interest occurred with the downhill
[(Fig._1)TD$IG]
119
foot. In addition, level ground walking trials were recorded for baseline comparisons. These trials were performed in a similar manner to the ramp trials but were done directly over the surface of the lab (as opposed to a level ramp). The subject started from rest at a position such that their 3rd footfall was with their right foot that landed directly over a force platform embedded in the floor and after this foot strike the subject continued walking for 3 more strides. Each subject performed five walking trials for each movement condition, all at a speed of 1.35 0.07 m/s. The walking speeds were monitored using two infrared timing light gates (Brower Timing Systems, Utah) spaced 1.2 m apart and mounted at hip height. The subjects were given as many practice trials beforehand as necessary to establish their starting position and the correct walking speed. During every trial, ground reaction force data were collected using a Kistler force platform operating at 2000 Hz (Kistler AG, Winterthur, Switzerland). Three retro-reflective markers with a diameter of 19 mm were attached with double sided tape to the rear portion of the right shoe on the posterior shoe heel, distal shoe heel and lateral shoe heel (Fig. 1). The 3D positions of each marker were recorded during trials using an eight camera Motion Analysis System (Motion Analysis Corp., Santa Rosa, California) operating at a frequency of 240 Hz. The motion capture system was calibrated to an accuracy defined by a 3D residual value below 0.6 mm. All data were analyzed using Matlab software (Mathworks, Natick, MA). For angle calculations, the foot angle relative to the floor was calculated, with a zero angle being defined as the shoe flat on the surface, with the shoe anterior–posterior axis aligned with the laboratory coordinate axis representing the direction of motion. Ground reaction force data were used to calculate traction coefficients over the stance phase for each walking condition. This was obtained by using the resultant horizontal force components and dividing them by the vertical force component. Due to the slope of the walking platform, transformations were applied to the raw force plate data by applying a rotation matrix that rotated the force data 198 around the long axis of the force plate in order to place the force data in a coordinate system that was aligned with the sloped platform. All data were compared to the level ground walking condition, with peak angles and traction coefficients at touchdown and toeoff being compared between conditions using a paired-samples ttests and a Holm–Bonferroni sequential correction [14] to account for multiple comparisons (a = 0.05). Therefore, after sequential correction was applied to the ranked p-values, significant differences were determined if a1 < 0.0125, a2 < 0.0167, a3 < 0.025 and a4 < 0.05. 3. Results
Fig. 1. Photograph of the walkway constructed in the laboratory in addition to the marker placement on the shoe.
The traction coefficients and foot-floor angles during level, downhill, uphill, and cross-slope walking are shown in Fig. 2. Touchdown and toe-off peak values are reported in Tables 1 and 2. During initial stance, there were no significant differences between level walking and any of the sloped walking conditions in regards to peak resultant utilized traction coefficients. The time at which these peaks occurred, however, was significantly increased during downhill walking compared to the level condition (p < 0.001). When the traction coefficient was broken into its anterior–posterior and medial–lateral components, significant increases (larger anterior traction) were seen during uphill walking (p < 0.001). All conditions had significant differences in traction in the medial–lateral direction, with the downhill, uphill and crossslope (downhill foot) requiring a greater amount of medial traction (p < 0.001 for all conditions), while the cross-slope (uphill foot) required a greater traction component in the lateral direction (p < 0.001).
[(Fig._2)TD$IG]
J.W. Wannop et al. / Gait & Posture 40 (2014) 118–122
120
Fig. 2. Coefficient of traction (top row) and shoe-floor kinematics (bottom row) during level and sloped walking. Data represent the average of all subjects, normalized from touchdown to toe-off. S-Down represents the lower foot during cross-slope walking, while S-Up represents the upper foot during cross slope walking.
into anterior–posterior components, downhill, side-downhill and side-uphill required significantly less anterior traction (p = 0.001, p = 0.002, p = 0.03) while uphill walking required significantly greater anterior traction (p < 0.001). In terms of medial–lateral traction, downhill, uphill and side-uphill required significantly greater lateral traction (p < 0.001, p = 0.01, p < 0.001) while sidedownhill walking required significantly greater medial traction values (p < 0.001). In terms of foot-floor angles, in the sagittal plane, uphill and side-downhill walking had significantly increased foot-floor plantarflexion angles (p = 0.008, p = 0.011), while in the transverse plane during side-uphill and side-downhill walking the foot was internally rotated (p = 0.018, p = 0.002). During uphill walking the foot was more externally rotated (p = 0.004). Lastly in the frontal plane, the foot was more everted during downhill, uphill and sidedownhill walking (p = 0.001, p < 0.001, p < 0.001).
In terms of foot-floor angles during initial stance, the peak footfloor dorsiflexion angle during uphill and side-uphill walking was significantly reduced compared to level walking (p < 0.001 and p = 0.009, respectively). In the transverse plane, side-uphill walking had an increased peak foot-floor internal rotation angle (p < 0.001), while uphill walking had the trend of an increase in the peak foot-floor external rotation angle (p = 0.043). In the frontal plane, during downhill and side-uphill walking, significant increases in the peak foot-floor inversion angles were present (p = 0.003 and p = 0.010), while during side-downhill walking there was the trend of a greater peak foot-floor eversion angle (p = 0.047). During final stance, traction coefficients were significantly higher during side-uphill walking (p = 0.007), while uphill walking had the trend of a greater required traction compared to the level condition (p = 0.023). When the traction coefficient was broken
Table 1 Peak traction and foot-floor angles during touchdown.
Peak traction coefficient Time at which peak traction occurred [ms] Average traction coefficient over stance AP peak traction coefficient ML peak traction coefficient Sagittal plane [deg] Transverse plane [deg] Frontal plane [deg]
Level
Downhill
Uphill
S-Down
S-Up
0.63 19.7 0.16 S0.50 S0.13 S35.9 S5.4 6.3
0.54 110.8 0.29 S0.51 0.11 S40.2 S9.7 9.1
0.62 22.5 0.37 0.57 0.15 S15.5 S11.9 5.1
0.82 19.5 0.38 S0.47 0.69 S32.1 2.2 S9.6
0.66 18.3 0.38 S0.58 S0.45 S25.9 11.1 10.5
Bold values represent a significant difference from level walking. In the sagittal, transverse and frontal plane positive/negative angles represent plantar/dorsi flexion, internal/ external rotation, inversion/eversion, respectively.
Table 2 Peak traction and foot-floor angles during toe-off.
Peak traction coefficient AP peak traction coefficient ML peak traction coefficient Sagittal plane [deg] Transverse plane [deg] Frontal plane [deg]
Level
Downhill
Uphill
S-Down
S-Up
0.61 0.61 0.09 54.2 S10.9 11.7
0.39 0.23 S0.12 58.7 S11.2 S0.7
0.81 0.87 0.06 73.2 S19.8 S10.5
0.57 0.38 0.50 61.4 5.4 S10.6
0.84 0.43 S0.70 60.0 12.8 15.8
Bold values represent a significant difference from level walking. In the sagittal, transverse and frontal plane positive/negative angles represent plantar/dorsi flexion, internal/ external rotation, inversion/eversion, respectively.
J.W. Wannop et al. / Gait & Posture 40 (2014) 118–122
Over the duration of stance, the average traction coefficient during downhill, uphill, side-downhill and side uphill walking was significantly higher than level walking (p < 0.001 for all conditions compared to the control, Table 1). 4. Discussion The main causes of acute injury in hiking are due to slip and fall injuries [1,2,6]. In general, slipping occurs when the available traction offered by a shoe-surface combination is less than the traction required to perform a given movement [7]. During heeltoe walking, the two points in time where the required traction is largest is immediately after touchdown, and immediately prior to takeoff; if the required traction at touchdown is not met, a heel slip results, if the required traction at takeoff is not met, a toe slip results. In terms of slip and fall accidents, heel slips are far more dangerous than toe slips. During a heel slip, the forward moving centre of mass must be supported by the slipping foot; if this does not happen (the individual is unable to ‘recover their balance’), a fall results. When walking along different sloped surfaces, the required traction coefficients at touchdown were quite similar to level walking. No Differences in the peak traction requirements during downhill walking were present, however, the peak traction value occurred much later in the stance phase (18% of stance) compared to all other movements (
