13:30
Use of IMU's in motion analysis I
Chair: James Sherwood
13:30
20 mins
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ACCURACY OF POSTURAL HUMAN-MOTION TRACKING USING MINIATURE INERTIAL SENSORS
Daniel Dinu, Martin Fayolas, Marine Jacquet, Elsa Leguy, Jean Slavinski, Nicolas Houel
Abstract: Balance control in upright position has direct impact on shooting performance in various competitive activities like archery, rifle shooting, etc. Feet positions and global posture of the athlete change between each shooting activities. Information and short time feedback about the variation of the centre of mass of the athlete during the time before the shoot appears essential for learning and developing skills in shooting sports. In this aim, the purpose of the study was to explore the accuracy and reliability of a motion analysis system which uses the technology of inertial sensors (MVN Biomech system, Xsens). The MVN Biomech system is composed of 17 miniature inertial centrals attached to the full body. The validation procedure consisted in comparing the data of twenty subject’s centre of mass directly extracted from the MVN Biomech system with those given by an optoelectronic system (Vicon) composed of 8 infrared camcorders. The centre of mass computed by both system was calculated using the same anthropometric model. For each subject, the comparison of mean position of the centre of mass was performed in three quiet standing of 30 s. Paired t-test, r correlation coefficient test and root mean square (RMS) were used to compare the accuracy between both devices. The results of paired t-test showed a significant difference between the measurements (p < 0.0001) in each component of the mean centre of mass position. Correlation between the tool’s measurements was significant and better than r > 0.99 on each component. RMS computation shows mean difference between tools equal to 5.45 mm on X component, 3.25 mm on Y component and 0.73 mm on Z component. The result of the MVN Biomech system appears accurate comparing to the optoelectronic system. The small differences could be explained by the relative motion of the respective sensors and markers of both systems on the soft tissues of the subject. If the MVN Biomech system was preliminary developed to explore the subject’s motion, the result of the present study showed that this system could also be used in order to estimate posture or micro-movements like postural sway during shooting activities
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13:50
20 mins
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HIGH ACCELERATION MOVEMENT PROFILES IN RECREATIONAL SMALL SIDED ASSOCIATION FOOTBALL
Jim Emery, Heather Driscoll, Andrew Barnes, David James
Abstract: Small sided football is the most popular area of adult football in the UK, with an estimated 1.5m adults playing every week. Matches are played on smaller pitches using different rules to the 11-a-side game; this results in less stoppage time and a higher volume of ball activity per player. Despite these established differences in playing style and the increase in participation, the types and frequencies of movements performed are not fully understood due to the time consuming nature of current notational analysis methods.
Understanding movements is of particular interest to researchers and developers seeking task representative protocols and products for small sided football. The importance of movement type, specifically those with high horizontal plane accelerations, has been demonstrated by recent findings linking traction and shoe stiffness to injury and performance in a number of team sports.
In this paper we introduce a new motion analysis technique that uses a combination of inertial sensors and manual notational analysis to describe high acceleration movements in a repeatable and more time effective manner than previously published. A recreational 5-a-side team (mean ± SD: age 17.8 ± 0.26 years, body height 1.77 ± 0.05 m, body mass 74.23 ± 16.25 kg) were observed during one season at a commercial football centre. Player mounted sensors were used to identify 1824 high acceleration movements from three players in seven matches. These movements were then classified using operational definitions adapted from notational analysis literature.
This paper outlines a high acceleration movement analysis technique, provides normative high acceleration movement profiles for three individual 5-a-side players, and suggests comparisons to published 11-a-side data. These movement profiles provide a foundation for footwear researchers and product designers to re-align their current practice or products from the 11-a-side game to this more popular style of football.
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14:10
20 mins
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OUTDOOR TESTS FOR THE VALIDATION OF AN INERTIAL SYSTEM ABLE TO DETECT ILLEGAL STEPS IN RACEWALKING
Giuseppe Di Gironimo, Teodorico Caporaso, Giuseppe Amodeo, Antonio Lanzotti, Stephan Odenwald, D.M. Del Giudice
Abstract: Race walking rules dictate that no visible loss of contact should occur during the whole race
and the athlete’s knee must be straightened until the vertical upright position. No visible loss
of contact means that at least one athlete´s foot must be in contact with the ground at all times
otherwise the athlete makes an illegal step and receive a warning. At present, during
competitions, the control of this rule is committed to several judges present on the racing
track, that can rely only on their eyes and therefore are not able to detect events shorter than
0,040 s (near the limit of human eyes). Basing the control of a rule on a subjective human
observation represents a significant problem, especially thinking that after 3 warnings the
walker is disqualified.
Aim of this study was to validate an inertial system capable to detect and to assess the loss of
contact event in race walking competitions. In a preliminary laboratory study an inertial
sensor (sample frequency of 200 Hz) was used by an Italian elite race walker, member of
national team, to acquire timing measurements of the loss of contact. The response of the
sensor, placed at L5/S1 of the vertebral column, was encoded and processed on an external
device and then was optimized by a specific protocol (filtering and correlation between
acceleration and the temporal events). The validation of the sensor measurements was realized
by 8 integrated platforms of force (680 Hz, accurate and direct system). Later the same athlete
performed long sequences of legal and illegal steps on the road in real conditions (like
competition events) at different velocities. The setting of a specific bicycle with a high-speed
camera (with a frame rate of 240 fps) allowed to acquire a video of the test following the
athlete and to validate the sensor measurements through video analysis tools.
Results of the study indicate that an inertial sensor can improve the accuracy in detecting
illegal steps. The wrongful identification are less than what could be detected by the unaided
human eyes. In conclusion the system, with the development and optimization of the
processing, could be a valuable tool to assist judges during race walk events.
Main References
[1] IAAF Competition Rules 2014-15
[2] Lee, J.B. , Mellifont R.B., Burkett B.J., James D.A. : “Detection of illegal race
walking: a tool to assist coaching and judging. (Article) “ Journal Sensors Volum 13,
Issue 12, 2013, Pages 16065-16074
[3] Knicker A., Loch M. (1990) , “Race walking technique and judging – The final report
of the International Athletic Foundation research project” National Study Athletic,
[4] Claypool M., Claypool K., Damaab F. (2006).” The Effects of Frame Rate and
Resolution on Users Playing First Person Shooter Games” . Proceedings of SPIE
[5] Loschky L.C. , McConkie G.W., Yang J., Miller M.E. “The limits of visual resolution
in natural scene viewing” Visual Cognition Volume 12, Issue 6, August 2005, Pages
1057-1092
[6] Esser P., Dawes H., Collett J., Howells K., :”Inertial sensing of vertical CoM
movement”, Journal of Biomechanics 42 (2009) 1578–1581
[7] Karie´ V.A.,Knezevic J.M., et al., : “Application-oriented comparison of the methods
for AC/DC converter harmonics analysis” IEEETrans.Ind.Electron.50 (6), 1100–1108,
2003
[8] Justin J. Kavanagh, Hylton B. Menz :” Accelerometry: A technique for quantifying
movement patterns during walking”, Science Direct, Gait & Posture 28 (2008) 1–15
[9] Wiebren Zijlstra, At L. Hof: “Assessment of spatio-temporal gait parameters from
trunk accelerations during human walking”, Science Direct, Gait & Posture 18 (2003)
1–10
[10] Little, C., Lee, J.B. , James, D.A., Davison, K. : “An evaluation of inertial sensor
technology in the discrimination of human gait ” Journal of Sports Sciences Volume
31, Issue 12, August 2013, Pages 1312-1318
[11] Wixted A.J., Billing D.C.,James D.J. : “Validation of trunk mounted inertial sensors
for analyzing running biomechanics under field conditions, using synchronously
collected foot contact data”, Sports Eng (2010) 12:207–212
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