1. Differences between sagittal plane static start and mid-cycle stroke biomechanics
during skating for the sport of sledge hockey: Task naïve population
A.M. Gal, A.D.C. Chan, and D.C. Hay
Knowledge to improve repetitive cyclical weight-bearing locomotion can be provided by
identifying differences between movement production from 1) rest, and 2) continuous
motion, if they exist [1]. Skating in sledge hockey is the foundational skillset and only
mechanical method for motion production. Biomechanically, skating is the product of
muscular force produced from the torso and each arm, which is transmitted along the
respective stick to the pick-surface interface, where muscular energy is transferred into
forward propulsion as a result of the picks digging into the ice surface. Typically, a task
naïve population displays greater observable differences in areas of difficulty than elite
populations [2]. Bilateral forward skating in elite sledge hockey is typically produced with a
flexed torso creating the possibility for a more horizontal pick plant, mechanically
producing greater forward force transfer [3], [4]. The ability to flex the torso during skating
is predicted to be proportional to skill level, which implies that optimal pick plant is more
likely to be achieved in elite players. The objective of this study was to identify sagittal
plane biomechanical difference(s) between a 1) start cycle (SC), and 2) mid-cycle (MC)
stroke at peak impact and push-off during skating off-ice, if they exist.
Five adult male able-bodied athletes propelled themselves in a study-specific indoor, off-ice
sledge (two wheels per youth sized chassis replaced the blades, and a front wheel) through
a Vicon motion capture system equipped with five bilateral upper torso/limb BTS-wireless
surface electromyography (sEMG) electrodes [5], [6]; sEMG were not analyzed for this
study. Participants were sledge hockey and poling sport naïve; asymmetrical bilateral
skating was predicted. Left, right, and sledge-body ground reaction forces were acquired in
a study-specific 4-force plate design [7], [8]. Three useable trials (good force plate contact)
were collected per i) submaximal, and ii) maximal effort test for both the 1) SC, and 2) MC.
Two participants performed an additional MC maximal effort test adding variation to the
protocol. Data were processed offline using MATLAB [10]. A low pass zero-lag 2nd order
Butterworth filter (12 Hz) was applied to motion capture raw signals.
SC torso (𝑇𝑆𝐶 )flexion (parallel to ground upwards) was 85° ± 4° with left (𝐿 𝑆𝐶) and right
(𝑅 𝑆𝐶) pick plants equalling 83° ± 3° and 84° ± 3, respectively. The difference between
MC and SC angles at pick plant were 𝑇 𝑀𝐶−𝑆𝐶 = 1° ± 3°, 𝐿 𝑀𝐶−𝑆𝐶 = 2° ± 1° and 𝑅 𝑀𝐶−𝑆𝐶 =
−1° ± 0°. MC torso flexion was 67° ± 9° with push-off pick angles equalling 𝐿 𝑀𝐶 = 80° ±
10°and 𝑅 𝑀𝐶 = 83° ± 4°. The difference between MC and SC angles at push-off were
𝑇 𝑀𝐶−𝑆𝐶 = 18° ± 5°, 𝐿 𝑀𝐶−𝑆𝐶 = 1° ± 3°, and 𝑅 𝑀𝐶−𝑆𝐶 = 3° ± 2°.
From these results, increased stability within skating was predicted to exist at pick off,
especially during MC. Increasing on and off-ice practice improving stability in the sledge is
recommended, with heightened focus creating torso flexion during arm extension. By
improving the SC, skating as a whole may improve in turn creating a more valuable player.
Increased momentum was suggested to be a product of improved MC skating. Further
biomechanical investigations are currently being implemented concerning skating as a
whole for sledge hockey.

2. References:
[1] A. Tözeren, Human body dynamics: classical mechanics and human movement. New
York: Springer, 2000.
[2] Chris Kirtley, Clinical gait analysis theory and practice. Edinburgh: Churchill
Livingstone, 2006.
[3] A. M. Gal, D. C. Hay, and A. D. C. Chan, “2 and 3-dimensional biomechanical analysis of
the linear stroking cycle in the sport of sledge hockey (Glenohumeral joint kinematic,
kinetic and surface EMG muscle modeling on and off ice),” in 13th International
Symposium on 3D Analysis of Human Movement, 2014, pp. 108–111.
[4] Hockey Canada, “Sledge hockey coaching resource.” 2009.
[5] Vicon Motion Systems Ltd., Nexus. U.K.: Vicon Motion Systems Ltd.
[6] BTS Bioengineering, “BTS Wireless sEMG,” BTS Bioengineering, 2016. [Online].
Available: http://www.btsbioengineering.com/.
[7] Bertec Corp., “Bertec Force Plate,” Bertec, 2016. [Online]. Available:
http://bertec.com/products/force-plates/.
[8] Kistler Instrument Corp., “Kistler Force Plate,” Kistler: measure. analyze. innovate., 2016.
[Online]. Available: https://www.kistler.com/ca/en/.
[9] J. R. Potvin and S. H. . Brown, “Less is more: high pass filtering, to remove up to 99% of
the surface EMG signal power, improves EMG-based biceps brachii muscle force
estimates,” J. Electromyogr. Kinesiol., vol. 14, no. 3, pp. 389–399, Jun. 2004.
[10] MathWorks, MATLAB. The Mathworks Inc., 1994.