1. Designed to observe complex internal musculoskeletal
kinetic energy as a solid-static system.
Baseline measures provide gravitational potential
energy for the linked mechanical system.
Isolating the point of rotation (only dynamic
component) permits minimum external forces to be
determined for the system.
Elbow angle prescribes impact angle (pole-plant angle)
affecting force transfer for locomotion.
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 A.M. 1, Chan A.D.C.1 & Hay D.C.2
INTRODUCTION
FOCUS
Figure 1. Elbow angle range. Seated double poling introduces a third preparatory
phase, which begins at full arm extension to instantaneous moment prior to impact;
the phase’s direct biomechanical benefit to the complete cycle is unknown.
A validated 2-dimensional solid-static single arm
average male (80kg) prototype with fixed elbow angles
at 120O, 135O and 150O, and wrist-stick angle 45O was
dropped above, below and at the horizon 3xs per drop
height (DH) for each elbow angle within a motion
capture system (250Hz). Impact forces were recorded
from a force plate at 2000Hz. A tripod was used to
provide consistency throughout trial drop heights.
Para-sports present difficultly in fundamental skill
development; each participant provides unique
limitations/paramtres.
Understanding fundamental skillsets allows for
educated advancement and modifications of the skill
and all subsequent variations.
Double poling is locomotion in sledge hockey, which is a
scientifically deficit sport; results are transferrable to
other short-pole double poling para-sports.
Para-athletes who are shoulder-dependent increase the
risk of overuse and/or overloading injury; advancement
in fundamental tasks can greatly amend this inevitable
outcome.
RESULTS
CONCLUSION
The effect of gravitational force acting on a solid limb
upon impact.
METHODOLODY Figure 2. SLAM-80 (sledge left arm male 80kg) is a validated solid-static prototype
architecturally designed from US Marine Corp personnel data and standardized
musculoskeletal parameters. SLAM-80 was fastened to a sledge hockey sledge (fixed
hip angle +40o from the horizon) and weights placed in the bucket to allow free
stance. Two plastic washers (4.00cm in diameter) were used to decrease friction at
the dynamic joint. Two 1.30kg wrist-weights were attached to the upper arm in a
stretched out fashion with an overlap at CoG, and a 1.20kg ankle-weight was attached
to the forearm in a stretched out fashion mimicking arm morphology.
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 analysis of the linear stroking cycle in the sport of sledge hockey: Glenohumeral joint kinematic, kinetic and surface EMG muscle modelling on and off 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 hockey mechanics take toll on shoulders: Analysis of propulsion technique can help experts design training programs to prevent injury. Journal of Bio-mechanics, 10(3): 71-
76.
Veeger, H.E.J., & van der Helm F.C.T. (2007). Shoulder function: The perfect compromise between mobility and stability. Journal of Biomechanics, 40, 2119-2129.
Acknowledgement M. Lamontagne (Human Movement Biomechanics Laboratory), B. Hallgrimsson (Industrial Design) & M. Haefele (Research Assistant)
1 2
Baseline measures indicated elbow angle does effect reaction forces (Rx) upon impact suggesting a 45o
forearm is an not optimal impact angle when concerned with impact-induced trauma; inversely, optimal
for force-produced locomotion.
Horizontal release and 45o forearm proved to be the safest impact (minimal Rx and P).
Above horizon release and a flexed elbow to 45o forearm is the greatest power generation range.
DH and TL Rx data presented analogous curves throughout each trial indicating a singular force-transfer
pathway back onto the system; non-contractile impact is consistent.
Understanding baseline measures in this downward moving phase of the cycle will provide an evaluation
tool used in subsequent research comparing musculoskeletal produced shoulder-dependent locomotion in
the sport of sledge hockey.
Trauma to the shoulder joint is inevitable for these athletes, however, understanding weight-bearing
shoulder produced locomotion will reduce the risk of overloading this highly mobile joint in turn
reinforcing structural integrity.
From this evidence maximal force transfer and power generation producing sledge propulsion occurs
above the horizon with a 45o forearm promoting sport-specific advancement in a necessary but basic
skillset; the linear stroking cycle.
Figure 3. Averaged force trajectory (time normalized) for each elbow angle per TL
(combined DH); E120 had a single outlier (*). Black __ TL4.0, -- TL4.5, … TL5.0, Red (*)
REFERENCES & ACKNOWLEDGMENT
→ Figure 5. Peak force and its corresponding
impulse and power were determined for
each elbow angle for each DH. Averages
were computed for each DH. All trials were
combined and an average was taken (SUM).
Impact trial lengths (TL) were consistent for E120
4.5x10-3s and E150 4.0x10-3s, however, inconsistent for
E135 (TL135ave 4.4x10-3s) providing two sets of results
affecting ranking order in some cases; TLsum 4.3x10-3s.
Impulse (J) determines the effect of force through the
duration it was applied.
FORCE (N) IMPULSE (Ns) POWER (W) E
ABOVE
1575 7.088 2158 120
1859
1695
7.436
7.543
2497
2315
1354
1530 7.650 2128 1355
1774 7.096 1795 150
1639 7.171 2045 AVE
HORIZON
1473 6.629 1844 120
1408
1447
5.632
6.158
1990
1301
1354
1485 6.683 1128 13545
1469 5.876 1437 150
1454 6.543 1510 AVE
BELOW
1444 6.498 1680 120
1715
1642
7.718
7.78
1505
1525
13545
1568 7.840 1648 1355
1518 6.072 1645 150
1544 6.948 1623 AVE
1567 6.738 1746 SUM
↖ Figure 4. Averaged force for each elbow
angle per TL represented for each DH.
Averages per TL are represented in black.
DH Above had a single outlier; data was
computed with (*) and without it.
Power (P) determines the rate of doing work.
Average pick displacement trial lengths (PDTL) ranged from 0.4s
0.7s between all the trials slightly affecting power calculations; SUM
was averaged to produce a 0.544m drop in 0.517s. All trajectories
will be compared to determine exact TL of the preparation phase in
subsequent research.
TL (s) FORCE (N)
SUM 4.0 x 10-3 1637
Above 4.0 x 10-3 1812
Horizon 4.5 x 10-3 1469
Below 5 x 10-3 1568
→ Figure 6.
Peak force
determined for
each DH from
averaged TL. All
trials were
combined and
an average was
taken (SUM).