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Measures of Reliability in the Kinematics of Maximal Undulatory Underwater Swimming


Medicine & Science in Sports & Exercise: April 2010 - Volume 42 - Issue 4 - p 762-770
doi: 10.1249/MSS.0b013e3181badc68
Applied Sciences

Purpose: The purposes of this article were to establish the reliability of the kinematics of maximal undulatory underwater swimming (UUS) in skilled swimmers, to determine any requirement for familiarization trials, to establish the within-subject (WS) variability of the kinematics, and to calculate the number of cycles required to accurately represent UUS performance.

Methods: Fifteen male swimmers performed 20 maximal UUS trials (two cycles per trial) during four sessions. The magnitude of any systematic bias present within the kinematic variables was calculated between session, trial, and cycle. Random error calculations were calculated to determine the WS variation. An iterative intraclass correlation coefficient (ICC) process was used to determine the number of cycles required to achieve a stable representation of each kinematic variable.

Results: Significant differences were found between session 1 and all other sessions for several variables, indicating the requirement for a familiarization session. Results indicated a wide range of WS variation (coefficient of variation [CV] = 1.21%-12.42%). Reductions in WS variation were observed for all variables when the number of cycles of data used to calculate WS variation was increased. Using six cycles of data, including additional cycles of data, provided diminishing returns regarding the reduction of WS variation. The ICC analysis indicated that an average of nine cycles (mean ± SD = 9.47 ± 5.63) was required to achieve the maximum ICC values attained, and an average of four cycles (mean ± SD = 3.57 ± 2.09) was required to achieve an ICC of 0.95.

Conclusions: After determining the systematic bias and establishing the requirement for a familiarization session, six cycles of data were found to be sufficient to provide high levels of reliability (CVTE = 0.86-8.92; ICC = 0.811-0.996) for each of the UUS kinematic variables.

1School of Life Sciences, Edinburgh Napier University, Edinburgh, Scotland, UNITED KINGDOM; 2Centre of Aquatics Research and Education, University of Edinburgh, Edinburgh, Scotland, UNITED KINGDOM; 3Department of Physical Education, Sport and Leisure Studies, University of Edinburgh, Edinburgh, Scotland, UNITED KINGDOM; and 4Exercise Science Department, East Stroudsburg University, East Stroudsburg, PA

Address for correspondence: Chris Connaboy, M.Sc., Sport & Exercise Science, School of Life Sciences, Edinburgh Napier University, Edinburgh, Scotland, United Kingdom; E-mail:

Submitted for publication February 2009.

Accepted for publication August 2009.

©2010The American College of Sports Medicine