VIDEO ANALYSIS HAS DIFFICULTIES WHEN RECONSTRUCTING IMAGES
Reis, A., Reis, V. M., Silva, A. J., Figueira, B., Louro, H., Marinho, D. A., & Barbosa, T. M. (2009). Comparison of 2d kinematical images reconstruction in breaststroke swimming: Dual media versus separated recording plans. ACSM 56th Annual Meeting, Seattle, Washington. Presentation number 2763.
This study compared two approaches for a 2D kinematical image reconstruction of breaststroke swimming: Dual media recording vs. separated recording plans. Male breaststrokers (N = 7) performed a 100-m maximal breaststroke swim in a 50-m pool. Two video cameras were placed in the sagittal plane at 25 m from the head wall to record a swimmer’s images under and above water. The images were subsequently reconstructed using two different procedures: dual media (DM) and separated recording plans (SP). A full stroke cycle was then analyzed twice for each S with Ariel Performance Analysis System. The following kinematic variables were compared: stroke cycle period, stroke frequency, stroke length, mean swimming velocity, stroking index, intra-cycle variation of the horizontal velocity of the centre of mass, and vertical displacement of the center of mass.
With the exception of the vertical displacement of the center of mass, kinematic variables did not differ when the two procedures of reconstruction were compared;. Vertical assessment using the separated digitization procedure may be influenced by different factors such as the light refraction phenomena, non-steady flow of the water around the S's body, higher difficulty to clearly determine air-water interface, and problems observing the head, trunk, and limb actions above the water.
Implication. The dual measurement procedure slightly underestimates water depth when compared with separated analyses. The dual measurement procedure seems better suited to digitize anatomic points especially when the air-water interface is critical for an analysis.
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