Performance Study: The Effect of a Lace Locking Device on Skate Lace Tension
An experimental approach to studying Panther Teeth conducted by Kelly Lockwood, Colin Dunne, Tzu-Ting Hsu, Ellingson, and John-Allan at Brock University and George Brown College.
INTRODUCTION
- The athlete-equipment interaction in gliding and sliding sports has been recognized as a fundamental component of performance success.
- Athletic footwear have traditionally used laces to secure the foot inside the boot and enhance fit, comfort and performance.
- Quantitatively assessing the merits of equipment, namely athletic footwear on the execution of technique, is technically challenging and has been handcuffed by the lack of portable and sensitive research instrumentation that can be used in a real-world competitive environment.
THE STORY
THE PROBLEM: Laces loosen over time and adversely affects the fit of the boot and the mechanics of the person wearing the boot.
THE NEED: Create consistent lace tension and enable the user to customize zones of lace tension.
THE SOLUTION: A lace locking device was proposed to maintain lace tension and customize tension zones throughout the lacing pattern.
PURPOSE
The purpose of the study was three-fold:
- To design, build and assess the reliability of a portable measurement apparatus to quantitatively measure lace tension.
- To investigate the stiffness properties of three different types of laces and assess their ability to maintain tension with and without a lace locking device installed in a non-human model.
- To compare lace tension pre-post a bout of skating with and without a lace locking device installed on the skate boot, as the athlete skated on a skating treadmill in a controlled lab environment and on the ice in a real-world sport environment.
Figure 1. Illustrations of the lace locking device in three positions: (A) the lace locking device, (B) device open with laces, and (C) device closed with laces secured.
EXPERIMENTAL PROTOCOL: DESIGN, BUILD & IMPLEMENT
PHASE 1: DESIGN & BUILD
- A portable measuring apparatus was designed, built and reliability assessed for the purpose of quantifying lace tension.
- The apparatus consisted of a load cell and a caliper. The load cell was calibrated with known weights to provide a measurement and a conversion factor from the unitless analog measurement to a digital force measurement with a meaningful unit (N).
- The apparatus was designed to accommodate both vertical and horizontal orientations and accept different types of footwear (e.g., skates).
- The apparatus measured displacement (mm) of the lace in response to an applied force (N).
RESULTS OF PHASE 1 concluded the build of a portable apparatus that could be used to reliability measure lace tension in footwear. Significant differences were revealed in lace stiffness across the three types of laces (p<0.05); suggesting that all laces stretch or elongate and as a result, can affect lace tension.
Figure 2. Different views of the lace tension measuring apparatus. (A) Sagittal view (B) Frontal view.
Figure 3. Three different types of laces, typically used in skate boots were used for stiffness testing. From left to right: a high-performance lace, a non-waxed lace, a waxed lace, and a steel cable used as a control.
Figure 4. Lace stiffness is represented as elongation (%) plotted in response to an applied force (N). Significant differences were revealed between the stiffness of the steel cable (control) and the stiffness of all three laces types (p<0.05). High-performance laces were significantly stiffer than non-waxed and waxed laces (p<0.05). Non-waxed and waxed laces performed in a similar manner.
PHASE 2: IN LAB – HUMAN MODEL
Lace tension was measured and compared pre-post a bout of treadmill skating with and without a lace locking (LL) device installed on the skate boot laces.
Participants wore their own skates with a new pair of non-wax laces installed and tied to their preferred tension.
Pressure distribution insoles were inserted into the skate boot to assist in confirming skate fit.
RESULTS OF PHASE 2 revealed significant differences in pre-post skate lace tension without the lace locking device (p<0.05), suggesting that laces loosen with wear. No significant differences in lace tension with the lace locking device installed, suggesting that the lace locking device provided a resistance to lace elongation.
Figure 5. Skate inserted into lace tension measuring apparatus.
Figure 6. Lace locking (LL) devices and measuring sites.
Figure 7a. Eyelet 2 with LL device.
Figure 7b. Eyelet 2 without LL device.
Figure 8a. Eyelet 6 with LL device.
Figure 8b. Eyelet 6 without LL device.
Pre-post skate comparison of force – displacement plots for two eyelet locations (2, 6) during the in-lab skating session; (a) Result with the lace locking device equipped; (b) Result without the lace locking device equipped.
The slope of the lines represent the material properties of the laces. The relatively parallel orientation of the lines reflects the same type
of lace being used.
The horizontal difference between the two lines is a result of the change in lace tension. There is a larger change in displacement measurements pre versus post skate without the lace locking device equipped, suggesting that there is more change in lace tension without the device equipped in comparison to with the lace locking device equipped.
PHASE 3: ON-ICE – HUMAN MODEL
Lace tension was measured and compared pre-post a bout of on-ice skating/game play with and without a lace locking (LL) device installed.
Participants wore their own skates with the lace locking device installed on the left skate and without the lace locking device installed on the right skate.
The portability of the apparatus permitted measurements to be obtained in a real-world sport environment.
RESULTS OF PHASE 3 revealed significant differences in pre-post skate lace tension without the lace locking device (p<0.05), suggesting that laces loosen with wear. No significant differences in lace tension with the lace locking device installed, suggesting that the lace locking device provided a resistance to lace elongation during a real-world sport application.
Figure 9. Skate inserted into lace tension measuring apparatus.
Figure 10a. Eyelet 6 with LL device.
Figure 10b. Eyelet 6 without LL device.
Pre-post skate comparison of force – displacement plots for one eyelet location (6) during the on-ice skating session. The slope of the lines represents the material properties of the laces. The relatively parallel orientation of the lines reflects the same type of laces being used. The horizontal difference between the two lines is a result of the change in lace tension. As seen in the lab, there is a larger change in displacement pre versus post a bout of on-ice skating without the lace locking device equipped, suggesting that there is more change in lace tension without the device equipped during on-ice skating condition.
CONCLUSIONS & PRACTICAL APPLICATION
The lace tension measuring apparatus was able to reliably quantify lace tension of footwear during use. The lace locking device: (i) provided resistance to elongation or slippage and had the ability to maintain pre established lace tension at the location where the device was installed, (ii) provided the users with the confidence in knowing that their customized lace tension will be maintained during use, and (iii) provided the users with the option of creating different zones of lace tension and customize the fit of the footwear.