John William Wannop

Footwear traction and lower extremity joint loading.

Background: Traction is influenced by the sole architecture and playing surface, with increases in traction potentially leading to injury. The mechanism as to how or why increased traction could lead to injury remains unknown. Purpose: This study was undertaken to determine how shoes of different sole designs and traction influence knee and ankle joint moments. Study Design: Controlled laboratory study. Methods: Traction testing was performed on 2 shoes of varying sole designs (tread vs smooth) using a robotic testing machine. All testing was conducted on a 60-cm × 90-cm piece of sample track surface. Kinematic and kinetic data were then collected on 13 recreational athletes performing running V-cuts in the 2 different shoe conditions. Five trials per condition were collected with reflective markers placed on the right shank and shoe of each participant. Kinematic and kinetic data were collected using an 8–high-speed camera system and force plate. Results: The coefficient of translational traction and the peak moment of rotation were both significantly higher in the tread shoe compared with the smooth shoe (1.00 vs 0.87 and 23.87 N·m vs 16.12 N·m, respectively). The high-traction shoe had significantly higher peak ankle external rotation moments (89.58 N·m vs 80.17 N·m), peak knee external rotation moments (36.23 N·m vs 32.02 N·m), peak knee adduction moments (224.0 N·m vs 186.8 N·m), and knee adduction angular impulse (2.10 Nms vs 1.83 Nms) compared with the low-traction shoe. Conclusion: Increased shoe traction significantly increased ankle and knee joint moments during a V-cut. Despite the significant difference in traction, no difference in performance was observed. These changes could have an effect on ankle and knee joint injury. Clinical Relevance: Shoes with decreased traction could be used in sports to reduce the joint moments in the knee and ankle and potentially reduce injury without a loss in performance.

Footwear traction and lower extremity noncontact injury

PURPOSE Football is the most popular high school sport; however, it has the highest rate of injury. Speculation has been prevalent that foot fixation due to high footwear traction contributes to injury risk. Therefore, the purpose of the study was to determine whether a relationship exists between the athletes specific footwear traction (measured with their own shoes on the field of play) and lower extremity noncontact injury in high school football. METHODS For 3 yr, 555 high school football athletes had their footwear traction measured on the actual field of play at the start of the season, and any injury the athletes suffered during a game was recorded. Lower extremity noncontact injury rates, grouped based on the athletes specific footwear traction (both translational and rotational), were compared. RESULTS For translational traction, injury rate reached a peak of 23.3 injuries/1000 game exposures within the midrange of translational traction, before decreasing to 5.0 injuries/1000 game exposures in the high range of traction. For rotational traction, there was a steady increase in injury rate as footwear traction increased, starting at 4.2 injuries/1000 game exposures at low traction and reaching 19.2 injuries/1000 game exposures at high traction. CONCLUSIONS A relationship exists between footwear traction and noncontact lower extremity injury, with increases in rotational traction leading to a greater injury rate and increases in translational traction leading to a decrease in injury. It is recommended that athletes consider selecting footwear with the lowest rotational traction values for which no detriment in performance results.

Softer and more resilient running shoe cushioning properties enhance running economy

Purpose: Several studies have investigated whether shoe cushioning properties have an effect on running economy. However, the findings have not been unanimous. Studies have shown both increases and decreases in running economy with soft shoes, while other studies have shown participant specific differences. Therefore, the purpose of this study was to add to the body of knowledge describing the effects of shoe cushioning properties on running economy. Methods: This study was comprised of two experiments; one using a stationary metabolic analysis system to measure oxygen consumption during treadmill running, and one using a portable metabolic analysis system to measure oxygen consumption during over-ground running. Twelve aerobically fit athletes participated in each experiment. Two professionally constructed pairs of prototype running shoes were provided by adidas AG for this experiment (Soft shoe and Control shoe). The shoes were identical in construction with the only differences being the midsole material and corresponding stiffness and energy return. Results: For both the treadmill and over-ground experiments, the Soft shoe condition was associated with statistically significantly decreased oxygen consumption compared to the Control shoe condition (Treadmill p = 0.044, Over-ground p = 0.028). In the treadmill experiment, 10 of the 12 subjects consumed less oxygen while wearing the more compliant/resilient condition, with an average decrease for all subjects of 1.0%. In the over-ground experiment 9 of the 12 subjects consumed less oxygen while running in the more compliant/resilient condition, with an average decrease for all subjects of 1.2%. Conclusion: Running shoes with softer and more resilient midsoles were found to influence running economy by 1.0% on average during treadmill and over-ground experiments.

Shoe traction and surface compliance affect performance of soccer-related movements

Purpose: To determine how shoe-surface interaction, specifically traction and compliance, affects performance and biomechanics of soccer-related movements. Methods: Third generation artificial turf was installed in the laboratory to allow for kinetic and kinematic data collection both on the turf and on a laboratory surface (Pulastic sports surface). Twelve male athletes performed five 5 m sprint accelerations and five 180° sprint turns in three different shoe-surface conditions (indoor soccer shoe on the laboratory surface, indoor soccer shoe on the turf surface, soccer cleat on turf surface). Comparisons between the indoor shoe across surfaces indicated compliance effects and comparisons between the cleat and indoor shoe on turf indicated traction effects. Results: Performance increased for the sprint acceleration in the indoor shoe on the turf compared to the laboratory (1.04 s vs. 1.08 s); however, no further increase in acceleration performance occurred with the soccer cleat. For the turn movement, no change in performance occurred comparing the indoor shoe across surfaces however an increase in turn performance was seen when using the soccer cleat on turf compared to the indoor shoe (2.67 s vs. 2.56 s). The cleat had both increased utilised translational and rotational traction compared to the indoor shoe on turf for the turn movement. The cleat also resulted in increased ankle eversion moments as well as increased knee abduction and external rotation moments compared to the indoor shoe on the turf surface for the turn movement. Conclusion: Both compliance and traction shoe-surface characteristics affect performance; however, the effects of the different characteristics are different depending on the movement type.

Wear influences footwear traction properties in Canadian high school football

Primary objective: To determine the range of translational and rotational traction that exists in cleated footwear of athletes, on the surface of play in Canadian high school football. Research design: Field study. Methods and procedures: The shoes of 106 athletes were tested on the field of play using a portable robotic testing machine. The machine measured translational and rotational traction on all shoes. Shoes were compared based on their shape, wear and cleat arrangement; fin, edge, stud. Main outcome and results: Translational and rotational traction ranged from 0.49 to 1.01 and 15.1 to 57.2 Nm, respectively. Fin shoes had significantly lower rotational traction compared to both the edge and stud shoe. Wear resulted in large variability of the cleated traction. Conclusions: The influence of wear has been shown to affect footwear traction, and must be taken into account. Therefore more accurate estimates of traction may occur when testing is completed using players’ actual footwear.

The effect of normal load, speed and moisture on footwear traction

Background: Numerous studies have tested footwear traction using various normal loads and movement speeds, and on different surfaces. However, because of the divergence from Amontons’ laws of friction, the results of studies that tested footwear traction using different normal loads or movement speeds are difficult to compare. The purpose of this study was to investigate how alterations of normal load, speed of testing and surface moisture affect footwear traction. Method: Data were collected on three types of footwear using a portable traction tester on the field of play of a natural grass and an artificial turf football field. Testing was conducted with different normal loads (335, 433, 580, 678 and 776 N), movement speeds (50, 100, 150 and 200 mm s−1, and 30, 60, 90° s−1) and amounts of moisture added to the field to determine the effect each variable had on traction. Results: Surface moisture had a large effect on traction and was shoe and surface specific. Normal load had a linear effect on traction with the ranking of the footwear staying consistent, indicating that testing at small normal loads may be sufficient. Movement speed had a linear relationship for translational traction but was constant for rotational traction, with the ranking of the footwear staying consistent again, indicating that slow speeds may be sufficient for testing. Conclusions: The relationships found are only valid for the method of testing used in this study, and for the range of loads and speeds tested. The relationship may fail to remain linear at higher or lower loads or speeds. Future studies should continue to examine the effect that moisture has on footwear traction to better understand how shoes react to changing conditions.

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.

Running shoe cushioning properties can influence oxygen consumption

adidas have recently launched a new running shoe midsole material. Termed ‘Boost’, these midsoles are comprised of expanded thermoplastic polyurethane (TPU) pellets. Compared to ethylene vinyl acetate (EVA), Boost material is claimed to be more compliant and have less energy loss. It has been hypothesised and theoretical studies have shown that energy return in footwear can have an influence on running performance (Nigg and Segesser 1992, Shorten 1993, Stefanyshyn and Nigg 2000). Therefore, the reduced energy loss of TPU midsoles may provide runners with a functional benefit. However, this remains to be verified experimentally.

Influence of Compression and Stiffness Apparel on Vertical Jump Performance.

Abstract Wannop, JW, Worobets, JT, Madden, R, and Stefanyshyn, DJ. Influence of compression and stiffness apparel on vertical jump performance. J Strength Cond Res 30(4): 1093–1101, 2016—Compression apparel alters both compression of the soft tissues and the hip joint stiffness of athletes. It is not known whether it is the compression elements, the stiffness elements, or some combination that increases performance. Therefore, the purpose of this study was to determine how systematically increasing upper leg compression and hip joint stiffness independently from one another affects vertical jumping performance. Ten male athletes performed countermovement vertical jumps in 8 concept apparel conditions and 1 control condition (loose fitting shorts). The 8 apparel conditions, 4 that specifically altered the amount of compression exerted on the thigh and 4 that altered the hip joint stiffness by means of elastic thermoplastic polyurethane bands, were tested on 2 separate testing sessions (one testing the compression apparel and the other testing the stiffness apparel). Maximum jump height was measured, while kinematic data of the hip, knee, and ankle joint were recorded with a high-speed camera (480 Hz). Both compression and stiffness apparel can have a positive influence on vertical jumping performance. The increase in jump height for the optimal compression was due to increased hip joint range of motion and a trend of increasing the jump time. Optimal stiffness also increased jump height and had the trend of decreasing the hip joint range of motion and hip joint angular velocity. The exact mechanisms by which apparel interventions alter performance is not clear, but it may be due to alterations to the force-length and force-velocity relationships of muscle.

Influence of basketball shoe mass, traction and bending stiffness on athletic performance

cal regions vulnerable to injuries. While the average and peak pressure are important parameters that can identify the pressure distribution and injury potential, the ratio of peak to average plantar pressure may reveal other aspects of the of tissue breakdown. Furthermore this will be a useful outcome measure for the influence of footwear and orthotics while investigating footwear biomechanics. Acknowledgement