Effect of a Lace Locking Device on Skate Lace Tension

ABSTRACT

Ice hockey skate boots traditionally use laces to secure the foot inside the boot, limit slippage, customize fit and enhance performance. A lace locking device was proposed to enhance the role of laces, maintain lace tension and customize tension zones throughout the lacing pattern. Applied sport research is often challenged by the lack of portable measurement instrumentation that can quantitatively assess the merits of athletic equipment and the effectiveness of specific equipment components. With a measurement apparatus developed in the previous research¹, the merits of skate laces can be easily assessed. The purpose of the study was to investigate the effect of without versus with the lace locking device installed on lace tension pre-post a bout of skating in two skating conditions: on a skating treadmill and on real ice. No significant differences were revealed with the lace locking device installed, potentially suggesting that lace tension was maintained by the device (p<0.05). Outcomes of the study suggested that the lace locking device provided a resistance to lace slippage, had the ability to maintain pre-established tension specific to the location where the device was installed, and further supported the athletes in customizing their skate setup.

Keywords: footwear, lace tension, lace locking device

INTRODUCTION

Athletic footwear is the vehicle by which mechanical function is translated to human motion and sport performance. The athlete-equipment interaction in gliding and sliding sports has been recognized as a fundamental component of performance success^2–5. However, 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, reliable, and sensitive research instrumentation that can be used in a real-world sport environment.

Previous research has provided proof of concept that laces can help limit foot-shoe movement and achieve better fit⁶. Different lacing patterns are often employed in an attempt to address anatomical differences in individual foot morphology⁷ and customize tension preferences in footwear. In the sport of ice hockey, skate boots traditionally use laces to secure the foot inside the boot and further enhance fit and comfort. It is common for an athlete to customize their skate lacing setup by using different types of laces or lacing strategies to create varying tension zones at different locations along the lacing pattern to optimize fit, comfort and ultimately support skating performance. Some practices have included using different materials of laces (e.g., waxed versus non-waxed), different lacing patterns (e.g., skipping or doubling up on eyelets), or by installing ad hoc lace locking devices. These practices are somewhat temporary band-aid solutions since laces are continuous; tension may disperse across the length of the laces and lacing pattern. Furthermore, the material properties of the laces allow for stretch¹ and as a result, lace tension loosens. All these factors may result in changes in the original or intended effect of securing and customizing footwear setup.

A novel practice that has emerged recently to enhance lace tension and secure footwear is the use of a self-lacing technology. One innovative method utilizes a motorized cable instead of the traditional lace permitting automated and precise control of lace tension. A recent study by Myers et al. (2022)⁸ investigated the impact of self-lacing technology on foot containment during dynamic motion. Results revealed significantly less movement of the foot within the footwear that potentially translates to related improvements in athletic performance and reduced injury potential, with the technology at low (-10% preferred), preferred, and high (+10% preferred) tensions. A subjective measure of athlete’s perception also revealed an increase in the athlete’s confidence level when performing dynamic motion with higher tension. However, the technology described above is currently unavailable in specialized footwear, such as ice skates.

Previous research has established relationships between lacing practices, tension and athletes’ confidence and performance^7–9. Quantitatively assessing the merits of lace locking practices is technically challenging. A portable apparatus was designed, built and reliability assessed previous research¹, specifically for the purpose of quantifying lace tension parameters [applied force (N) and displacement from skate tongue (mm)] while the footwear is secured on the foot. The apparatus included a customizable platform to accept different types of footwear (e.g., running shoes, hiking boots, ski boots, ice skates), allowing lace tension to be assessed when the footwear was secured on the foot, pre and post a bout of activity in both the controlled environment of a laboratory and when subjected to a sport-specific, real-world environment.

The current study proposed an alternative lace locking device to maintain lace tension during activity and to further support comfort and fit of the athletes’ equipment in sport-specific environments. The piece of equipment under investigation was a patented and commercially available after-market lace locking device (Figure 1). The lace locking device can be installed on the existing lace of athletic footwear with the intention to reduce lace slippage, permit the user to create distinct zones of lace tension, and reduce the need of retying the footwear during extended use. Therefore, the purpose of the study was to confirm these claims by comparing lace tension pre and post a bout of skating without and with the lace locking device both in a lab environment on a skating treadmill and in a real-world environment on ice.

Figure 1

Note. Illustrations of the lace locking device in three positions (a) the Lace Locking Device, (b) Device open with laces, (c) Device closed with laces secured.

METHODS

Study Design

The study was a mixed methods experimental design including two interventions, namely without and with the lace locking device installed on the skate boot laces. The intervention was repeated in two experimental environments; (i) in a controlled laboratory environment on a skating treadmill, and (ii) in the real-world sport environment, on the ice during game play. Ethical clearance was obtained from the Office of Research Ethics Board at Brock University (File #21-251).

Instrumentation

A portable apparatus (Figure 2) designed and built specifically for the purpose of quantifying lace tension parameters¹ was used for the current study. Data collection procedures and data analyses were consistent with procedures developed in the previous study¹.  Output measures of the apparatus included force (N) and displacement (mm) collected by the load cell and the calliper when a force is applied to the lace. To facilitate this, the hook secured to the end of the cable was attached to the lace at the desired eyelet location. Once a force was applied to the lever, the force was transferred to the lace via the cable and pulled the lace away from the tongue of the footwear¹.

Figure 2

Note. Different views of the apparatus. (a) View at 45 degrees (b) Frontal view. The base of the apparatus was designed to secure all types of footwear including ice skates. There are adjustable stoppers located at the front and the two sides of the base. There is a slot in the middle of the base plate which can allow skate blade to fit in to provide constrain to footwear movement. The lever on the top coming out of the back provided a loading mechanism through the cable while the load cell and calliper attached at the other end measure force and displacement of the force applied respectively. The microcontroller was used to initiate and stop the data collection while recording measurements from the load cell and the calliper.

Phase 1 – Investigation of lace locking device installed on a skate boot in a controlled laboratory environment while skating on a skating treadmill

The purpose of Phase 1 was to investigate the effect of without the lace locking device installed versus with the lace locking device installed on lace tension pre and post a bout of skating on a skating treadmill.

Participants

A total of eight participants (n=8) were recruited (four males and four females). The eligibility criteria included: participants were treadmill trained defined by having completed a minimum of eight sessions of previous skating treadmill training, participants were self-reported as injury free, and participants were actively playing hockey at a competitive level.

Equipment

Participants wore their own skates. Skates were sharpened to game play conditions and a new pair of non-wax laces (Howies Hockey Tape, MI, USA) were installed in all skates. A previous study suggested that laces stretch under tension loads and depending on the material of the laces, some stretches more than the other¹. For the purpose of consistency across all participants, non-waxed laces were selected for the study. The lacing pattern was consistent. Each participant tied their own skates to their own preferred tension for game-like conditions. Plantar pressure insoles (XSENSOR® Technology Corporation, AB, Canada) were inserted into the skate boots prior to lacing the skates. The insoles were used in the study to provide a baseline measure of fit of the skate and lace tension for each intervention. Baseline pressure measures (psi) were defined as the pressure exerted on the insoles from the foot due to the tension of the laces securing the foot to the footbed. The baseline pressure measures were collected prior to the skating bout in both interventions. Participants were required to sit on a bench with knees extended and feet lifted from the ground to unweight the skates for five seconds. The baseline pressure measures were calculated as the average pressure over five seconds for each section of the foot (forefoot, midfoot, heel and total foot). Paired samples t-tests of the baseline pressures (psi) recorded by the insoles at the forefoot, midfoot, heel and total foot were conducted between interventions. An analysis of the pressure data revealed consistent pre skate baseline pressures for each section of the foot and total foot between interventions. This consistency in the pressure data can be interpreted as a consistent fit of the skate and lace tension prior to the bout of skating in both interventions. 

Warmup

A skating treadmill in a controlled laboratory environment was used for the purpose of this study. The surface of the treadmill is 3.6 m² (200cm by 180cm) covered by a series of parallel polyethylene slats prepared with silicon to simulate the frictionless surface of real ice. A harness was fit and secured to each participant and connected to an overhead track system as a safety measure. A standardized and supervised warm up protocol consisted of three 20-second skates at a speed of 7.5mph (12.07km/h) and an incline of 5° on the skating treadmill.

Treadmill Skating Protocol

Participants completed a standardized protocol of moderate intensity consisting of five 30-second bouts of skating at 7.5mph (12.07km/h) speed and 5° incline, followed by three 30-second bouts of skating at 7mph (11.27km/h) speed and 10° incline. Moderate intensity was dictated by participant’s previous treadmill training experience and calibre of play and was consistent and repeated for both interventions. A work-to-rest ratio of 1:3 was implemented to control for the effect of fatigue while skating on the treadmill.

Without lace locking device – pre and post lace tension measurement procedures

Pre: Following the warmup and prior to the skating protocol described above, participants were instructed to sit in a chair to loosen and retie the laces of the skates to ensure the pre skate tension measures were not influenced by any skating prior to the start of the skating bout. The lace tension apparatus (Figure 2) was used to measure the force (N) required to pull the lace as well as its displacement (mm) away from the tongue of the skate boot (Figure 3). Lace tension measurements were recorded at the second (below the lace locking device hold zone), the fourth (between the lace locking device hold zone), and the sixth (above the lace locking device hold zone) eyelet of the left skate.

Post: Following the skating protocol described above, participants were again required to sit in a chair and lace tension measurements were repeated at the same eyelet locations (two, four, and six) as the pre measurement on the left skate.

With lace locking device

Participants were instructed to loosen their laces so that the lace locking device could be installed. Lace locking devices were installed on the laces aligned with the third and the fifth eyelets on the left skate during the retying process. The hold zone referred to the space between the two lace locking devices (Figure 3). The skating protocol and measurement procedures were consistent with those performed for the previous condition, without the lace locking device.

Figure 3

Note. Locations for the lace locking devices in Phase 1 with the red box indicating hold zone.

Figure 4

Note. Setup of the apparatus during data collection of Phase 1.

Phase 2 – Investigation of lace locking device installed on a skate boot in a real-world environment while skating on the ice

The purpose of Phase 2 was to investigate the effect of without the lace locking device installed versus with the lace locking device installed on lace tension pre and post a bout of skating on the ice.   

Participants

A total of 14 female participants (n=14) were recruited. Eligibility criteria included; participants were self-reported as injury free and were actively playing competitive hockey. All participants were instructed to wear their own skates sharpened for game like conditions.

On Ice Skating Protocol

Participants warmed up with their own choices of movements for the first 5 minutes of the skate. A 45-minute bout of on ice skating simulated the movement patterns, speeds, and intensities of competitive game play.

Pre and post lace tension measurement procedures

Pre: Participants were required to sit in a chair with their knees flexed at 90°. The lace locking device was installed on the seventh eyelet from the toe of each participant’s left skate. No lace locking device was installed on the right skate. The measurement apparatus was used to collect force (N) and displacement (mm) of a pull on both left (representing with) and right (representing without) skates of each participant at the sixth eyelet (one eyelet below the lace locking device).

Post: Following the on-ice bout of skating, participants were required to sit in a chair with their knees flexed at 90° in order to repeat tension measurements (force (N) required to pull the lace and lace displacement (mm) away from the tongue of the skate boot) at the same eyelet location (eyelet 6).

Figure 5

Note. Apparatus setup during Phase 2 data collection.

DATA ANALYSIS & RESULTS

Phase 1 – Results of lace tension with lace locking device installed on a skate boot in a controlled laboratory environment while skating on a skating treadmill

At each of the measurement sites (eyelets 2, 4, and 6), a force (N) versus displacement (mm) plot was generated for both pre and post skate data. A linear line of best fit was generated for each data set; the slope of the line represents the stiffness property of the lace materials and the translation value represents the shift in displacement (mm) for pre and post measurements. The shift in displacement (mm) was compared and used as a quantitative metric for lace tension. Paired-comparison t-tests were performed to compare means of the lace tension parameter between pre and post skate measurements without and with lace locking device.

Results revealed significant differences in lace tension parameter pre and post a bout of treadmill skating for both interventions (without and with the lace locking device) at the fourth and the sixth eyelets, but no significant differences at the second eyelet (Table 1). An observation of graphs revealed less change was observed between pre and post measurements for the second (see Figure 6) and the fourth eyelet (Figure 7) with the lace locking device equipped, but not in the sixth eyelet (Figure 8). Measured displacements were negative as they reflected the direction the calliper was moving when the lever of the apparatus was pulled. Less magnitude in the displacement measured by the apparatus indicates that there was less “give” in the lace which means there was less likelihood of foot shift and discomfort caused by loosening of the lace.

Table 1

Paired comparison t-test results for treadmill data collection.

Compared Pair	Mean ± SD	p-value
Without Eyelet 2 Pre – Post	0.56 ± 0.97	0.076
With Eyelet 2 Pre – Post	1.30 ± 2.84	0.119
Without Eyelet 4 Pre – Post	0.63 ± 0.69	0.018
With Eyelet 4 Pre – Post	2.16 ± 2.74	0.031
Without Eyelet 6 Pre – Post	1.44 ± 1.33	0.009*
With Eyelet 6 Pre – Post	3.01 ± 1.90	0.001*

*p<0.05 for indication of statistical significance.

Figure 6

Note. Pre and post skate comparison of force – displacement plots for in-lab skating session at eyelet 2. (a) Result without the lace locking device equipped (b) Result with the lace locking device equipped. X and Y axis of the plots were scaled to the same values. There is a larger change in displacement measurements pre versus post skate without the lace locking device equipped meaning there is more change to lace tension without the device equipped at eyelet 2.

Figure 7

Note. Pre and post skate comparison of force – displacement plots for in-lab skating session at eyelet 4. (a) Result without the lace locking device equipped (b) Result with the lace locking device equipped. X and Y axis of the plots were scaled to the same values. There is a larger change in displacement measurements pre versus post skate without the lace locking device equipped meaning there is more change to lace tension without the device equipped at eyelet 4.

Figure 8

Note. Pre and post skate comparison of force – displacement plots for in-lab skating session at eyelet 6. (A) result without the lace locking device equipped (B) result with the lace locking device equipped. X and Y axis of the plots were scaled to the same values. There is a larger change in displacement measurements pre versus post skate with the lace locking device equipped meaning there is more change to lace tension with the device equipped at eyelet 6.

Phase 2 – Results of lace tension with lace locking device installed on a skate boot in a real-world environment while skating on the ice

The change in displacement of the lace tension measurements were plotted and statistically compared pre and post skate without and with lace locking device using the same analysis performed in phase 1. Pre and post skate measurement differences were used as a comparative lace tension metric between the right (without lace locking device) and left (with lace locking device) skate.

Results revealed significant differences in lace tension on the right skate (without lace locking device installed) pre and post a bout of simulated game play skating on ice. However, no significant difference in lace tension was seen on the left skate (with the lace locking device) (see Table 2). Force-displacement plots provide a graphical representation of the collected data (Figure 9) where the slope of the line represents the stiffness property of the lace materials and the translation value represents the shift in displacement (mm) for pre and post measurements. The shift in displacement (mm) was then used as a quantitative metric for lace tension.

Table 2

Paired comparison t-test results for on-ice data collection.

Compared Pair	Mean ± SD	p-value
Without Pre – Post	2.76 ± 4.30	0.016*
With Pre – Post	1.43 ± 4.29	0.116

*p<0.05 for indication of statistical significance.

Figure 9

Note. Pre and post skate comparison of force – displacement plots for on-ice skating session. (a) result without the lace locking device equipped (b) result with the lace locking device equipped. X and Y axis of the plots were scaled to the same values. There is a larger change in displacement measurements pre versus post skate without the lace locking device equipped meaning there is more change to lace tension without the device equipped during on-ice skating session.

DISCUSSION

The study provided a comparative analysis of lace tension parameters without the lace locking device versus with the lace locking device installed in the controlled environment of a laboratory on a skating treadmill and in a sport-specific real-world environment on the ice. The behaviour of the laces is governed by their material properties, and as such, the lace locking device is an add-on device with the specific purpose of adding value to the role of laces. By maintaining tension established by the athlete, the lace locking device could potentially help reduce friction induced injuries, increase athlete confidence, and footwear comfort.

Results revealed more change in pre and post lace tension measurements without the lace locking device versus with the lace locking device installed. These results were consistent across both environments, on skating treadmill and on ice. This potentially implies that the lace locking device consistently maintains tension at the location where it is installed in both a controlled lab and a real-sport environment.  

Through improving the fit of the footwear and foot containment, maintaining lace tension at preferred tension or higher lace tension can provide athletes with confidence in their equipment while performing dynamic movements. The lack of shifting of the lace tension with the lace locking device throughout the skate has multiple implications for a user. By holding lace tension, the lace locking device made it easier for athletes to customize their skate lacing setup knowing that the setup would maintain tension, providing athletes with the confidence to perform dynamic movements required throughout their performance.

Limiting the movement of the foot inside the footwear can also further reduce the potential for friction related injuries, such as lace bite, heel spurs and bunions. Treatment for these friction related injuries involve reducing contact force and friction between the footwear and the foot or ankle¹⁰. The lace locking device achieved that objective by holding lace tension at its optimal tension to prevent further irritation due to overly tight skate. The lace locking device may potentially be used as preventative measures for friction induced injuries as well.

FUTURE RESEARCH

It is a logical progression to extrapolate and implement assessment methodologies across athletic footwear in different sports requiring footwear models consisting of 2-15 eyelets. Funding has been secured to investigate the generalization of the lace locking device across different footwear models consisting of 2-15 eyelets. Further investigation is needed to provide insight on how different configurations and quantity of the lace locking device on the laces could potentially impact the tension results. Further investigation is also needed to help eliminate friction-based injury in footwear with the lace locking device. This will build upon the current academic-industrial relationship established and generalize the effectiveness of the device across a variety of athletic footwear.

REFERENCES