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Title: Lower trunk muscle activity in butterfly swimming
Authors: Martens, Jonas
Lievens, Stijn
Einarsson, Ingi Thor
Fernandes, Ricardo
Staes, Filip
Daly, Daniel
Issue Date: Apr-2014
Publisher: Australian Institute of Sport
Conference: International Symposium on Biomechanics and Medicine in Swimming edition:12 location:Canberra date:28 April - 2 May 2014
Abstract: Introduction: The activation patterns of propulsive swimming muscles such as latissimus dorsi or triceps are well documented, especially in the crawl and breaststroke1, but the number of studies on the activity of lower trunk muscles in butterfly is limited. A clear rise in activity of the rectus abdominis “in the early stage of the stroke” was described2. A reciprocal activity in the rectus abdominis and erector spinae was noted and the cocontractions of these antagonistic muscles demonstrated their roles in trunk flexion and extension as well as in its stabilization3. The purpose of this study was to analyze lower trunk muscle activation in butterfly swimming and examine how this muscle activity is related to arm and leg synchronization.
Method: Two national level male swimmers (PB on 100m butterfly: 56.80s and 59.89s) swam 2x12.5m butterfly at maximal speed without breathing in 3 conditions: full technique with a 2-beat leg kick, arms action only and leg kick only. EMG was obtained with 4 wireless units (KINE, 1600Hz), with the electrodes placed on the left and right Obliquus Externus (OE) and on the left and right Erector Spinae (ES) following the guidelines of SENIAM. To prevent water from interfering with the EMG signal, the units were protected with a water resistant second skin and sport tape. KINE software was used for EMG analysis. Raw data was integrated and normalized to the dynamic maximum. Four 50Hz video cameras recorded the swims in synchronization with the EMG-signal. Dartfish Prosuite software was used to determine stroke phases and arm and leg synchronization.
Results: Figure 1 shows the average activation (full line) of the 4 investigated muscles in the 3 butterfly conditions ± SD (dotted lines) expressed as a % of the dynamic (y-axis) and related to the arm and leg synchronization (x-axis).
Introduction: The activation patterns of propulsive swimming muscles such as latissimus dorsi or triceps are well documented, especially in the crawl and breaststroke1, but the number of studies on the activity of lower trunk muscles in butterfly is limited. A clear rise in activity of the rectus abdominis “in the early stage of the stroke” was described2. A reciprocal activity in the rectus abdominis and erector spinae was noted and the cocontractions of these antagonistic muscles demonstrated their roles in trunk flexion and extension as well as in its stabilization3. The purpose of this study was to analyze lower trunk muscle activation in butterfly swimming and examine how this muscle activity is related to arm and leg synchronization.
Method: Two national level male swimmers (PB on 100m butterfly: 56.80s and 59.89s) swam 2x12.5m butterfly at maximal speed without breathing in 3 conditions: full technique with a 2-beat leg kick, arms action only and leg kick only. EMG was obtained with 4 wireless units (KINE, 1600Hz), with the electrodes placed on the left and right Obliquus Externus (OE) and on the left and right Erector Spinae (ES) following the guidelines of SENIAM. To prevent water from interfering with the EMG signal, the units were protected with a water resistant second skin and sport tape. KINE software was used for EMG analysis. Raw data was integrated and normalized to the dynamic maximum. Four 50Hz video cameras recorded the swims in synchronization with the EMG-signal. Dartfish Prosuite software was used to determine stroke phases and arm and leg synchronization.
Results: Figure 1 shows the average activation (full line) of the 4 investigated muscles in the 3 butterfly conditions ± SD (dotted lines) expressed as a % of the dynamic (y-axis) and related to the arm and leg synchronization (x-axis).
Publication status: published
KU Leuven publication type: IMa
Appears in Collections:Physical Activity, Sports & Health Research Group
Research Group for Musculoskeletal Rehabilitation

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