Shoe-surface Interface Research Articles

Biomechanical Demand during 90° and 135° Cutting Manoeuvres: Implications for Anterior Cruciate Ligament Injury

Background: Anterior cruciate ligament (ACL) injuries in athletes have financial and health consequences and are considered career-threatening. The current study aimed to shed light on biomechanical differences between various change of direction (COD) manoeuvres. Understanding such differences is important, given their association with the incidence of non-contact ACL injuries. Methods: Thirty-six male recreational soccer players participated and performed 90° and 135° COD manoeuvres. For gait analysis, the Vicon system was used. The speed and shoe-surface interface were standardized in the COD manoeuvres. Paired sample t-tests were used to compare conditions. Results: A Greater peak external knee abduction moment (PEKAM) (p<0.001) and knee abduction angle at initial contact (IC) (p<0.001) in the 135° COD manoeuvre compared to the 90° COD manoeuvre were observed, highlighting the increased injury risk potential at greater COD angles. In addition, the hip sagittal plane range of motion (RoM) from IC to peak knee valgus angle was higher in the 135° COD manoeuvre than 90° COD manoeuvre (p<0.001). Conclusion: The results of the current study support the idea that ACL biomechanical risk factors are angle-dependent. A sharper cutting angle showed a higher risk of ACL injury due to the increase in the PEKAM and the knee abduction angle at initial contact. Therefore, players should be trained to reduce high PEKAM and the knee abduction angle by using different strategies.

Injury risk among athletes on artificial turf: a review of current literature

Artificial turf is used commonly as an alternative to natural grass for athletic playing surfaces, primarily for its ease of maintenance, multi-use capability year-round, and cost. Prior studies have demonstrated increased biomechanical stresses at the shoe-surface interface on artificial turf when compared to natural grass. However, there is debate whether the altered shoe-surface interface confers additional risk for injury to athletes. The purpose of this study was to review the current literature on injury risk associated with artificial turf among various sports played on turf. The present study was a clinical review of the current literature regarding injury risk on artificial and natural turf. While playing surface generally does not appear to impact overall injury risk in soccer and rugby players, data is inconclusive among American football athletes. Lower-extremity injuries, in particular knee and ankle injuries, more commonly occur on artificial turf in comparison to natural grass. Surface and sport-specific shoes, third-generation artificial turf, and routine monitoring and maintenance have all been shown to reduce the risk of injury on artificial turf. When athletes must play on artificial turf, surface-specific strategies may be implemented to reduce their risk of injury. Future studies should be conducted to evaluate further these risk reduction strategies. Level of Evidence: Level V.

The Interaction of Cognitive Interference, Standing Surface, and Fatigue on Lower Extremity Muscle Activity

BackgroundPerforming cognitive tasks and muscular fatigue have been shown to increase muscle activity of the lower extremity during quiet standing. A common intervention to reduce muscular fatigue is to provide a softer shoe-surface interface. However, little is known regarding how muscle activity is affected by softer shoe-surface interfaces during static standing. The purpose of this study was to assess lower extremity muscular activity during erect standing on three different standing surfaces, before and after an acute workload and during cognitive tasks.MethodsSurface electromyography was collected on ankle dorsiflexors and plantarflexors, and knee flexors and extensors of fifteen male participants. Dependent electromyography variables of mean, peak, root mean square, and cocontraction index were calculated and analyzed with a 2 × 2 × 3 within-subject repeated measures analysis of variance.ResultsPre-workload muscle activity did not differ between surfaces and cognitive task conditions. However, greater muscle activity during post-workload balance assessment was found, specifically during the cognitive task. Cognitive task errors did not differ between surface and workload.ConclusionsThe cognitive task after workload increased lower extremity muscular activity compared to quite standing, irrespective of the surface condition, suggesting an increased demand was placed on the postural control system as the result of both fatigue and cognitive task.

Six different football shoes, one playing surface and the weather; Assessing variation in shoe-surface traction over one season of elite football.

IntroductionAn optimal range of shoe-surface traction (grip) exists to improve performance and minimise injury risk. Little information exists regarding the magnitude of traction forces at shoe-surface interface across a full season of elite football (soccer) using common football shoes.ObjectiveTo assess variation in shoe-surface traction of six different football shoe models throughout a full playing season in Qatar encompassing climatic and grass species variations.MethodsFootball shoes were loaded onto a portable shoe-surface traction testing machine at five individual testing time points to collect traction data (rotational and translational) on a soccer playing surface across one season. Surface mechanical properties (surface hardness, soil moisture) and climate data (temperature and humidity) were collected at each testing time point.ResultsPeak rotational traction was significantly different across shoe models (F = 218, df = 5, p <0.0001), shoe outsole groups (F = 316.2, df = 2, p < .0001), and grass species (F = 202.8, df = 4, p < 0.0001). No main effect for shoe model was found for translational traction (F = 2.392, p = 0.07).ConclusionsThe rotational (but not translational) traction varied substantially across different shoe types, outsole groups, and grass species. Highest rotational traction values were seen with soft ground outsole (screw-in metal studs) shoes tested on warm season grass. This objective data allows more informed footwear choices for football played in warm/hot climates on sand-based elite football playing surfaces. Further research is required to confirm if these findings extend across other football shoe brands.

Neuromechanical adaptations to slippery sport shoes

Although shoe friction has been widely studied in occupational ergonomics, information was lacking about friction in sport shoes. The purpose of the study was to examine the neuromechanical adaptations to different shoe-surface interface in an aerobic-gym specific movement. Sixteen females performed 10 change of direction movements in two shoe conditions differing by their outsoles (ethyl-vinyl-acetate: EVA and rubber: RB) to ensure significant differences in mechanical coefficients of friction (EVA = 0.73 ± 0.07 and RB = 1.46 ± 0.15). The kinematics, kinetics and muscle activities of the right lower-limb were analysed. Statistical parametric mapping was used to investigate the kinematics and kinetics adaptation to the different shoe-surface coefficients of friction. The participants had a longer stance duration in the EVA compared to the RB condition (526 ± 160 ms vs. 430 ± 151 ms, p < .001). The ankle and knee joints powers and works were lower during both the braking and the push-off phases in the EVA as compared to the RB condition. Preactivation of the agonist muscles (soleus, gastrocnemius medialis and vastus medialis) decreased in the EVA compared to the RB condition (−28.5%, −26.5% and −49.0%, respectively). Performing a change of direction movement with slippery shoes reduced the ankle and knee joints loadings, but impaired the stretch-shortening cycle performance. Participants demonstrated thus a different neuromechanical strategy to control their movement which was associated with a reduced performance.

The role of shoe design on the prediction of free torque at the shoe–surface interface using pressure insole technology

The goal of the current study was to expand on previous work to validate the use of pressure insole technology in conjunction with linear regression models to predict the free torque at the shoe–surface interface that is generated while wearing different athletic shoes. Three distinctly different shoe designs were utilised. The stiffness of each shoe was determined with a material’s testing machine. Six participants wore each shoe that was fitted with an insole pressure measurement device and performed rotation trials on an embedded force plate. A pressure sensor mask was constructed from those sensors having a high linear correlation with free torque values. Linear regression models were developed to predict free torques from these pressure sensor data. The models were able to accurately predict their own free torque well (RMS error 3.72 ± 0.74 Nm), but not that of the other shoes (RMS error 10.43 ± 3.79 Nm). Models performing self-prediction were also able to measure differences in shoe stiffness. The results of the current study showed the need for participant–shoe specific linear regression models to insure high prediction accuracy of free torques from pressure sensor data during isolated internal and external rotations of the body with respect to a planted foot.

The Development of a Translational Traction Rig to Investigate the Mechanisms of Traction in 3G Turf

During football specific movements a high translational traction is desired at the shoe-surface interface to facilitate player movement. Translational traction is commonly assessed through bespoke mechanical test devices which provide a more repeatable tool for characterising the shoe-surface interaction compared to player testing. Following development, application of the rig is demonstrated through an initial investigation into the effect of the number of studs and stud orientation on translational traction. The translational rig consists of a tray attached to two trails, with surface samples of varying specification placed in the tray. A number of stud configurations were chosen and tested on a 3G artificial turf sample. The initial stiffness response of the surface as well as larger displacements were considered to help inform the mechanisms of traction. The study showed the increasing force as the number of studs increased and how the positions of the studs also relate to the forces produced in the infill and the effect on the mechanism of traction.

Risk of Anterior Cruciate Ligament Injury in Athletes on Synthetic Playing Surfaces

Background: The effect of synthetic playing surfaces on the risk of injury in athletes is frequently debated in the orthopaedic literature. Biomechanical studies have identified increased frictional force at the shoe-surface interface, theoretically increasing the risk of injury relative to natural grass. This increase in frictional force is potentially relevant for the risk of anterior cruciate ligament (ACL) rupture, where noncontact mechanisms are frequent. However, clinical studies examining this issue have shown mixed results. Hypothesis/Purpose: The purpose of this study was to systematically review the available literature on risk of ACL rupture on natural grass versus artificial turf. We hypothesized that the risk of ACL rupture on synthetic playing surfaces would not be higher than that of natural grass playing surfaces. Study Design: Systematic review. Methods: A systematic keyword search was performed of OVID, EMBASE, the Cochrane Library of Systematic Reviews, and the PROSPERO International Prospective Register of Systematic Reviews. Candidate articles were included if they reported the risk ratio of ACL rupture on natural grass versus synthetic playing surfaces, were of level 3 evidence or better, and included only ACL injuries sustained during organized athletic events. Exclusion criteria included a study with non-field-related sports and the use of historical cohorts for calculating risk ratios. Results: A total of 10 studies with 963 ACL injuries met criteria for inclusion, all of which reported on soccer and football cohorts. Among these, 4 studies (753 ACL injuries) found an increased risk of ACL injury on artificial playing surfaces. All 4 of these articles were conducted using American football cohorts, and they included both earlier-generation surfaces (AstroTurf) and modern, 3rd-generation surfaces. Only 1 study in football players found a reduced risk of ACL injury on synthetic playing surfaces. No soccer cohort found an increased risk of ACL injury on synthetic surfaces. Conclusion: High-quality studies support an increased rate of ACL injury on synthetic playing surfaces in football, but there is no apparent increased risk in soccer. Further study is needed to clarify the reason for this apparent discrepancy.

Footwear traction and three-dimensional kinematics of level, downhill, uphill and cross-slope walking

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 three-dimensional 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 19° 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 cross-slope walking which could place the hiker at risk of injury with a misstep or if there was a slight slip.

Effect of Varying the Volume Infill Sand on Synthetic Clay Surfaces in Terms of the Shoe-surface Friction

The friction developed by the shoe-surface interface on artificial clay has not been widely studied, and can influence player's performance and injury risk. The aim of this research was to investigate the effect of varying the quantity of infill sand on shoe- surface friction on an artificial clay court tennis surface. A laboratory-based mechanical test rig was used to measure the friction force developed at the shoe-surface interface. Additionally, the perception of a group of participants, performing a turning movement on the same surface under dry conditions, was collected in order to compare against the mechanical results. The relationship between the normal force and friction generated by the shoe-surface interaction was examined for surfaces with different sand in-fill volumes. The mechanical testing was performed under dry and wet conditions, showing strong and significant differences. Results indicated that the normal force significantly influenced the static and dynamic frictional forces. For lower sand infill volumes, as normal loading increased, the dry condition was found to exhibit the lowest peak static friction force and highest average dynamic friction force. However, for higher sand infill volume conditions, the opposite behaviour was observed. Strong and significant positive linear relationships were found between peak friction force and average dynamic friction force for all infill sand volumes and conditions. The mechanical results were in agreement with the perception data, which suggests that the participants were sensitive to the small changes in sand infill volumes.The findings of this study will therefore aid the understanding of tennis players’ perceived response to a tennis court surface. In order to get a better understanding of friction behaviour, further testing needs to be performed, and once the mechanisms involved are understood, surface properties could be modified to increase performance and reduce injury risk.

Influence of Clay Properties on Shoe-kinematics and Friction During Tennis Movements

Tennis is a sport characterised by being played on different surfaces: hard court, grass and clay. These surfaces influence the style of play and tennis specific movements. Specifically on clay, most of the common movements performed by players (e.g. accelerating, side stepping and braking), are performed with some level of controlled sliding. In order to reduce the player's injury risk, and assess the shoe-surface requirements on clay surfaces, there is a need for a scientific understanding of the player's kinematics and tribological mechanisms occurring at the shoe-surface interface. The purpose of this study was to identify the kinematics of the shoe during the sliding phase, and to assess the friction that is present. Baseline areas of both ends of a clay court were prepared with two different mixes of clay, varying the particle size. Eight experienced clay players participated in this study which took place during the Conde de Godó tennis tournament in Barcelona, Spain. 3D kinematic data data was collected using two synchronised high speed video cameras, and after the tests, perception questionnaires were applied to the players. Additionally, three different mechanical devices were utilised to measure the friction of the two clay surfaces. Displacement and velocity data of the shoe in contact with the surface were correlated with the friction measurements from both clay surfaces. Results indicated that significant differences occurred between the two clay surfaces for some shoe kinematic data, and mechanical friction. However, the perception scores suggest the opposite behaviour stated by the mechanical test and shoe-kinematic data. The present study has provided evidence that shoe kinematics and friction of the shoe-surface interaction are affected by the surface conditions, specifically particle size.

Torque prediction at the shoe–surface interface using insole pressure technology

Excessive rotational traction between the foot and the playing surface has been shown to increase the risk of athletic injuries to ligaments in the knee and ankle. It is not currently feasible to accurately determine the free torque generated at the shoe–surface interface utilizing live participants without an embedded force plate. The goal of the current research was to predict the free torques that developed at the shoe–surface interface during voluntary internal and external rotations of the body relative to a planted foot using an insole pressure measurement system. Six participants fitted with a shoe containing an insole pressure measurement device performed trials on an embedded force plate. A pressure sensor mask of specific sensors was determined based on the degree of linear correlation between sensor pressure and the free torque. Linear regression analyses were utilized to develop a General Linear Regression Model and Participant-Specific Linear Regression Models. The results of this study indicated that insole pressure technology, in conjunction with linear regression models, can be utilized to predict free torques generated at the shoe–surface interface during isolated rotational motions of the body with respect to a planted foot. Furthermore, Participant-Specific Linear Regression models may be more accurate in these predictions than a general model, based on a group of participants. When used with computational modeling, this technique might allow the investigation of strains produced in ligaments of the ankle and knee that are generated during internal and external rotations of the body with a planted foot on various turf surfaces outside a laboratory setting.

The effect of normal load force and roughness on the dynamic traction developed at the shoe–surface interface in tennis

During tennis-specific movements, such as accelerating and side stepping, the dynamic traction provided by the shoe–surface combination plays an important role in the injury risk and performance of the player. Acrylic hard court tennis surfaces have been reported to have increased injury occurrence, partly caused by increased traction that developed at the shoe–surface interface. Often mechanical test methods used for the testing and categorisation of playing surfaces do not tend to simulate loads occurring during participation on the surface, and thus are unlikely to predict the human response to the surface. A traction testing device, discussed in this paper, has been used to mechanically measure the dynamic traction force between the shoe and the surface under a range of normal loading conditions that are relevant to real-life play. Acrylic hard court tennis surfaces generally have a rough surface topography, due to their sand and acrylic paint mixed top coating. Surface micro-roughness will influence the friction mechanisms present during viscoelastic contacts, as found in footwear–surface interactions. This paper aims to further understand the influence micro-roughness and normal force has on the dynamic traction that develops at the shoe–surface interface on acrylic hard court tennis surfaces. The micro-roughness and traction of a controlled set of acrylic hard court tennis surfaces have been measured. The relationships between micro-roughness, normal force, and traction force are discussed.

Traction of clogged golf footwear

Purpose: In the game of golf, players are constantly moving into and out of many different terrains as well as playing on different ground conditions, which may cause the shoe-surface interface to become contaminated with solid debris. The addition of this debris will no doubt alter the shoe-surface interface, potentially altering the golfer's traction and performance during the swing. Therefore, the purpose of this study was to compare the traction of two different types of golf cleats on wet and dry surfaces, while the traction elements were both clean and clogged with debris. Methods: The traction of footwear with two different cleat combinations on wet and dry natural grass, while the traction elements were unclogged and clogged with debris was tested. A robotic testing machine that encompassed six degrees of freedom was used for all traction testing. A normal load of 500 N was applied to the shoe, after which the platform moved at a speed of 75 mm/s, with the horizontal and vertical forces being measured by the load cell during the duration of the movement. Results: Clogging of the cleats significantly reduced traction (F = 63.823, p < 0.001) as did wetting the surface (F = 9.964, p = 0.002). Testing location of the shoe caused a difference in traction measurements with the forefoot having significantly higher traction values than the rearfoot (F = 49.617, p < 0.001). Cleat type did not have a significant effect on traction (F = 1.364, p = 0.247). Conclusion: If footwear is clogged with course contaminants, significant reductions in traction could occur, which may lead to slipping and result in altering the timing or motion of the swing as well as the ability to transfer the required force through the body to the ball.

Biomechanical analysis of traction at the shoe-surface interface on third-generation artificial turf

The existing knowledge of traction on artificial turf is based almost exclusively on mechanical devices. While most attention has traditionally been concentrated on rotational traction, sports such as soccer predominantly involve translational movements. The aim of the study was to investigate whether translational traction at the shoe-surface interface differed between various third-generation artificial turf systems in combination with different cleat configurations in vivo. Twenty-two male soccer players performed five short sprints with a 90° cut over a turf-covered force plate for each combination of three turf systems and three cleat configurations. The results showed that, despite various differences in other traction measures, traction coefficients were almost identical across turf systems and cleat configurations.

The development of an apparatus to understand the traction developed at the shoe–surface interface in tennis

The traction developed at the shoe–surface interface can have a significant influence on a player’s injury risk and performance in tennis. The purpose of this study was to investigate shoe–surface traction on a dry acrylic hard court and two artificial clay court tennis surfaces in dry and wet conditions. A laboratory-based mechanical test rig was developed to measure the traction force developed at the shoe–surface interface. Linear regression analysis was used to examine the relationship between normal force and three measures of traction: initial stiffness, peak traction force and average dynamic traction force. The normal force did not significantly influence the initial stiffness for the shoe–surface system on the acrylic hard court but did on the artificial clay surfaces. The infill particle size and the addition of moisture influenced the traction developed on the artificial clay surfaces. Small, dry particles developed greater traction and with a sufficiently high applied normal force will provide traction comparable to that on an acrylic hard court. However, increased particle size and/or the presence of moisture generally reduced traction. Strong and significant positive linear relationships were found between peak traction force and average dynamic traction force for all surface types and conditions. This study improves the understanding of the influence surface characteristics have on shoe–surface traction mechanisms. Once traction mechanisms are understood, surface properties and/or footwear can be effectively changed to maximise performance and/or minimise injury risk.

A Review of Synthetic Playing Surfaces, the Shoe-Surface Interface, and Lower Extremity Injuries in Athletes

The evolution of synthetic playing surfaces began in the 1960s and has had an impact on field use, shoe-surface dynamics, and the incidence of sports-related injuries. Modern third-generation turfs are being installed in recreational facilities and professional stadiums worldwide. Currently, > two-thirds of National Football League teams,> 100 National Collegiate Athletic Association Division I football teams, and > 1000 high schools in the United States have installed synthetic playing surfaces. Those in favor of such playing surfaces note their unique combination of versatility and durability; they can be used in both ideal and inclement weather conditions. However, the more widespread installation and use of these surfaces have raised questions and concerns regarding the impact of artificial turf on the type and severity of sports-related injuries. There appears to be no question that the shoe-surface interface has a significant impact on such injuries. Independent variables such as weather conditions, contact versus noncontact sport, shoe design, and field wear complicate many of the results reported in the literature, thereby preventing an accurate assessment of the true risk(s) associated with certain shoe-surface combinations. Historically, studies suggest that artificial turf is associated with a higher incidence of injury. Furthermore, reliable biomechanical data suggest that both the torque and strain experienced by lower extremity joints generated by artificial surfaces may be more than those generated by natural grass fields. Recent data from the National Football League support this theory and suggest that elite athletes may sustain more injuries, even when playing on the newer artificial surfaces. By contrast, some reports based on data collected from lower-level athletes suggest that artificial turf may protect against injury. This review discusses the history of artificial surfaces, the biomechanics of the shoe-surface interface, and some common turf-related lower extremity injuries.

Understanding the influence of surface roughness on the tribological interactions at the shoe–surface interface in tennis

The traction provided by shoe–surface interactions in tennis can have an impact on player safety, performance and overall enjoyment of the sport. There is a requirement for an improved scientific understanding of the tribological interactions at the shoe–surface interface and the effects that footwear and surface characteristics have on the traction developed. The aim of this study was to investigate the influence surface roughness has on traction present during a sliding contact between a shoe and an acrylic hard court tennis surface. The substrate of acrylic hard court tennis surfaces are formed from a coating of a silica sand and acrylic paint mix, giving them variations in surface roughness characteristics. Mechanical traction tests were performed on five surfaces of varying roughness at normal forces of between 400 N and 800 N with a commercially available acrylic hard court tennis shoe (with a herringbone outsole pattern) and a shoe with a flat outsole. Significant linear relationships were found between dynamic traction force and normal force. A trend for decreased dynamic traction with increased roughness was found. When examined under a microscope after testing evidence of contact between the shoe and the surface decreasing with increased surface roughness was found. With the flat shoe, surface roughness affected the relationship between the coefficient of traction and the normal load. As roughness increased the coefficient of dynamic traction becomes less dependent on normal force. Evidence of a sudden increase in traction with the flat shoe when tested on the roughest surface suggests other friction mechanisms caused by the outsole overcoming the roughness of the surface, such as abrasive wear, had a significant effect on dynamic traction force.

Rotational Stiffness of Football Shoes Influences Talus Motion during External Rotation of the Foot

Shoe-surface interface characteristics have been implicated in the high incidence of ankle injuries suffered by athletes. Yet, the differences in rotational stiffness among shoes may also influence injury risk. It was hypothesized that shoes with different rotational stiffness will generate different patterns of ankle ligament strain. Four football shoe designs were tested and compared in terms of rotational stiffness. Twelve (six pairs) male cadaveric lower extremity limbs were externally rotated 30 deg using two selected football shoe designs, i.e., a flexible shoe and a rigid shoe. Motion capture was performed to track the movement of the talus with a reflective marker array screwed into the bone. A computational ankle model was utilized to input talus motions for the estimation of ankle ligament strains. At 30 deg of rotation, the rigid shoe generated higher ankle joint torque at 46.2 ± 9.3 Nm than the flexible shoe at 35.4 ± 5.7 Nm. While talus rotation was greater in the rigid shoe (15.9 ± 1.6 deg versus 12.1 ± 1.0 deg), the flexible shoe generated more talus eversion (5.6 ± 1.5 deg versus 1.2± 0.8 deg). While these talus motions resulted in the same level of anterior deltoid ligament strain (approxiamtely 5%) between shoes, there was a significant increase of anterior tibiofibular ligament strain (4.5± 0.4% versus 2.3 ± 0.3%) for the flexible versus more rigid shoe design. The flexible shoe may provide less restraint to the subtalar and transverse tarsal joints, resulting in more eversion but less axial rotation of the talus during foot∕shoe rotation. The increase of strain in the anterior tibiofibular ligament may have been largely due to the increased level of talus eversion documented for the flexible shoe. There may be a direct correlation of ankle joint torque with axial talus rotation, and an inverse relationship between torque and talus eversion. The study may provide some insight into relationships between shoe design and ankle ligament strain patterns. In future studies, these data may be useful in characterizing shoe design parameters and balancing potential ankle injury risks with player performance.

The influence of surface characteristics on the tribological interactions at the shoe-surface interface in tennis

During dynamic tennis specific movements, such as accelerating and side stepping, the traction provided by a shoe-surface combination plays an important role in the injury risk and performance of the player. Acrylic hard court tennis surfaces have been reported to have increased injury occurrence due to an increased traction coefficient. There is a requirement for an improved scientific understanding of the tribological interactions at the shoe surface interface and the effects footwear and surface parameters have on the friction mechanism developed. Often mechanical test methods used for the testing and categorisation of playing surfaces do not tend to simulate loads occurring during participation on the surface, and thus are unlikely to predict human response to the surface. A new traction testing device, discussed in this paper, has been developed to mechanically measure the traction force between the shoe and the surface under appropriate loading conditions. Acrylic Harcourt tennis surfaces generally have a rough surface topography, due to a sand and acrylic paint mixed top coating, and have a deformable under layer to provide impact attenuation. Surface micro-roughness has been found to influence the friction mechanisms presents during viscoelastic contacts, as found in footwear-surface interactions. This paper aims to further understand the influence of micro-roughness on tennis surfaces. The micro-roughness and traction of a controlled set of acrylic hard court tennis surfaces have been measured. The influence of roughness on tennis surfaces traction is discussed.