The purpose of this study is to quantitatively examine, via biomechanical analysis, the influence of orthotics on force transference in hockey skates. Orthotics have been successfully utilized as a remedy for several physical ailments. However, the actual biomechanical impact of orthotics has yet to be analyzed with regards to the skating stride. By examining both force application and joint motion throughout the skating stride, indications can be made as to whether orthotic implementation could significantly improve skating performance. Study 1 (n—18) occurred on acrylic ice in the Wilfrid Laurier University Biomechanics laboratory (Waterloo, ON) to analyze the kinetics of a skating stride, while Study 2 (n=7) used a skating treadmill (Zone Training Center, Waterloo, ON) that permitted constant skating velocity. Participants (n=18) ranged from 18 to 25 years old (mean = 21.3 years±1.8) and body mass ranged from 54.5 to 99.1 kg (mean = 80.9 kg ±10.5). The highest level of play ranged from intercollegiate teams to intramural leagues. The orthotics inserts that were used in both studies were semi-rigid medial-longitudinal arch cookies scaled to the participant's arch height. The three orthotic conditions included a control condition (O1 - no insert), a minimal condition (O1 - 33% of medial longitudinal arch height (MLAH)) and a moderate condition (O1 - 66% of MLAH). Study 1 participants (n=18) completed a skating stride and a skating start on top of a force plate embedded beneath acrylic ice for each of the orthotic conditions. Study 2 participants skated at 50% and 75% of their maximum attainable velocity for each orthotic condition.
A one way repeated measures ANOVA with a priori of p<0.05 and a Bonferroni post hoc was used to analyze the effect of orthotics for each of the testing conditions. During the acrylic ice trials, the ratio of plantar force to ground reaction force (or force transference ratio) was significantly improved with orthotic condition O3 over O1 (p<0.001) and O2 (p<0.001) (O1:1.327±0.23, O2 1.354±0.19, O3: 1.2061.21). Increased kinetic outputs (O1 tGRF impulse: 321.4 N/s ± 50.6, O3:333.6 N/s ± 62.4), (O1 shear impulse: 101.0 N/s ± 28.9, O3:105.1 N/s ± 30.7) and reduced maximum plantar forces (O1 total: 1438.0 N ± 372.8, 03 total: 1290.6 N ± 278.3) (p<0.001) were achieved via altered plantar surface loading rates and a reduced medio-lateral center of pressure range (O1:11.3mm ± 4.0, O3:10.0mm ± 3.4). O2 was not different than O1 in several categories and did not produce better results than O3, potentially due to the small size of the orthotic not being large enough to induce an altered plantar pressure interaction or support the medial longitudinal arch.
In the skating treadmill trials, at 50% of maximum velocity O2 and O3 elicited a significantly greater stride duration than O1 (O1:1.160s±0.18, O2:1.232s±0.19, O3:1.248s±0.16), which resulted in a reduced stride rate (O1:53.0 strides/min ±7.9, O2:49.8±7.7, O3:48.1±6.4), an increased normalized stride length (O1: 3.40%height ±0.82, O2: 3.66±0.88, O3: 3.77±0.80), and O3 exhibiting the most improved results. Knee and ankle kinematics were not different between orthotics.
In summary, during the acrylic ice trials, O3 altered the plantar surface interaction of the foot by improving the plantar force distribution, reducing the maximum plantar force and center of pressure range, resulting in an improvement in the force transference ratio. On the skating treadmill, O2 and O3 exhibited improved fundamental stride characteristics. Ultimately, O3 altered the plantar surface interaction which facilitated an increase in several kinetic outputs and improved vital skating characteristics over the control condition, O1. With the observed changes in several measures, the utilization of orthotic inserts in hockey skates has the potential to improve skating performance.