1. Baseline Impact Reaction Forces in a Seated Downward Short-Pole Free-Drop:
A Biomechanical Investigation of Elbow Angle upon Impact in the Sport of Sledge Hockey
Gal, AM, Chan, ADC & Hay, DC
Understanding external reaction forces acting upon a dynamic system presents a difficult task
biomechanically; internal forces are complex and inexperienced scientifically.Baseline measures (BM)
enhance the depth into which results can be derived. BM can be investigated by isolating the point of
rotation using a solid-static systemto determine the minimum external force exerted onto the system;
this study’s focus was the effect of gravitational force acting on a solid limb upon impact. Using a test-
retestapproach,BMforimpactforces were determinedfrom adownwardpoling free-dropof avalidated
prototype mimicking an average male (80kg) solid-static single-armed sledge hockey player; retest
incorporatedset-upimprovementssuggestedfrompreviousstudies(*).Limbmorphologywas mirrored
using two 1.3kg wrist-weights (medial/lateral upper arm) and a single 1.2kg ankle-weight (medial
forearm). Elbow (E) and wrist-stick angles were fixed at 150o
, 135o
, 120o
and 45o
, respectively. Three
useable trials where collected for each E at above, below and horizon drop heights* (DH). Marker
trajectories were acquired by a Vicon motion capture system at 250Hz* and impact forces by a Kistler
force plate at 2000Hz* (no filter)*; initial impact to point of recoil. Trial lengths(TL) were consistent for
E120 and E150, 4.0x10-3
s and 5.0x10-3
s respectively;TL for E135 rangedbetweenthe two (TL135ave 4.4x10-3
s),
data was averaged by TL then combined providing two sets of results for E135 affecting ranking order in
some cases.Toprankingresultsindicatedthataveraged-peakreactionforce (RxtSum) was1637N fromTL4.0
with a maximal averaged-impulse (JtSum) of 3.94Ns from TL5.0; RxtAbove 1812N (TL4.0) with JtAbove 4.25Ns
(TL4.0),RxtHorizon 1469N (TL4.5) withJtHorizon 3.86Ns (TL4.5), and RxtBelow 1568N (TL5.0) withJtBelow 3.89Ns (TL4.5).
Combined TL resulted in a peak RxSum of 1567N (1511N+
including a single trial outlier) with an JSum of
3.87Ns (3.83Ns+
); RxAbove 1639N (1321N+
), RxHorizon 1454N, and RxBelow 1544N with JAbove 4.15Ns (3.31Ns+
),
JHorizon 3.53Ns and JBelow 3.72Ns. The highest ranking averaged-peak impact recorded for E was RxE135TL4.0
1709N andRxE135 1617N; above the horizon RxE150 1774N, horizon RxE135TL4.5 1485N and RxE120 1473N, and
below RxE135TL4.5 1715N andRxE135 1642N. BM indicatedthatEdoeseffectRx uponimpact suggestinga45o
forearmis not an optimal impactangle when concernedwithimpact-inducedtrauma;inversely,optimal
for force-produced locomotion (approximately 10ms-1
change in arm momentum). Elevated DH and
shorter TL indicated larger Rx and J, as hypothesized. Horizontal release and flexed E proved to be the
safest impact illustrating minimal Rx. Despite DH and/or TL Rx data presented analogous curves
throughouteachEindicatingasingularforce-transferpathwaybackontothe system;impactisconsistent.
Para-sports present difficultly in fundamental skill development, each participant provides unique
limitations/parametres. Understanding fundamental skillsets allows for educated advancement and
modificationsof the skillandall subsequentvariations.Doublepolingis locomotioninsledgehockey; this
research provides advancement to this scientifically deficit sport and is transferrable to other double
polingpara-sportssuchas alpinepush-starts.Para-athleteswhoare shoulder-dependentincrease the risk
of overuse and/or overloading injury; advancement in fundamental tasks can greatly amend this
inevitable outcome.
Acknowledgement M. Lamontagne (Human Movement Biomechanics Laboratory), B. Hallgrimsson
(Industrial Design) & M. Haefele (Research Assistant)

2. References:
Bernardi, M., Janssen, T., Bortolan L., Pellegrini, B., Fischer, G. & Schena, F. (2013). Kinematics of cross-
country sit skiing during a paralympic race. Journal of Electromyography and Kinesiology, 23, 94-101.
Gal AM, Chan ADC & Hay DC. (2015). Investigating the seated double poling cycle: Identifying baseline
measures for the preparation phase. A. Gal [et al.] (sciencesconf.org:isbs2015:59230).
Gal AM, Chan ADC & Hay DC. (2015). Validating a solid-static single-armed male prototype tasked to
produce dynamic movement from the shoulder through the preparation phase. IFMBE Proceedings.
Gal AM, Hay DC & Chan ADC.(2014) 2 and 3-dimensional analysisof the linearstrokingcycle inthe sport
of sledge hockey:Glenohumeraljointkinematic,kineticandsurface EMGmuscle modellingonandoff ice.
13th
3D AHM :108-111 ISBN 9782880748562.
Holmberg, H., Lindinger, S., Stoggl, T., Eitzlmair, E. & Muller, E. (2005). Biomechanical analysis of double
poling in elite cross-country skiers. Medicine & Science in Sports & Exercise, 37(5):807-818.
Lomond,K.& Wiseman,R.(2003). Sledge hockeymechanicstake toll onshoulders:Analysisof propulsion
technique can help experts designtraining programs to prevent injury. Journal of Bio-mechanics, 10(3):
71-76.
Veeger,H.E.J.,&vanderHelmF.C.T.(2007).Shoulderfunction:The perfectcompromise betweenmobility
and stability. Journal of Biomechanics, 40, 2119-2129.