Does the Hip Reflect the Centre of Mass Swimming Kinematics?

Abstract

The purpose of this study was to determine the relationship between the hip point and the centre of mass for kinematical parameters (displacement, velocity and acceleration) in the three axes of motion. One complete stroke cycle was analyzed in eight swimmers performing a 25 m front crawl swim test at high intensity. Within-subject correlation coefficients were computed between the centre of mass and both hips, as well as mean of the errors, RMS error and a paired sample t-test. High correlation coefficients were found for the displacement in the horizontal direction (r=1.00 for both hips) and low to moderate correlation coefficients (r=−0.01 to r=0.54) were found for all other studied variables. Moreover, moderate to large RMS errors were observed: (i) between 0.05 and 0.15 for the displacement; (ii) between 0.16 and 0.30 for the velocity and (iii) between 5.28 and 7.86 for the acceleration. Complementarily, RMS errors for the intracyclic velocity variation were between 0.07 and 0.18. Considering the centre of mass and hip values statistical differences were found in velocity in x, acceleration in x and y, and intracyclic velocity variation in y axes. Therefore, results suggest that the hip point does not represent most kinematical parameters of the estimated centre of mass in front crawl swimming.

Key words

biomechanics - digitization - three-dimensional - front crawl

References

• 1 Abdel-Aziz YI, Karara HM. Direct linear transformation from comparator coordinates into object space coordinates in close range photogrammetry. In: Proceedings of the American Society of Photogrammetry Symposium on Close Range Photogrammetry. Falls Church: American Society of Photogrammetry. 1971: 1-18
• 2 Barbosa T, Santos Silva JV, Sousa F, Vilas-Boas JP. Comparative study of the response of kinematical variables from the hip and the centre of mass in butterfliers. In: Chatard JC (ed) Biomechanics and Medicine in Swimming IX. St Etienne: University of St Etienne Publications. 2003: 93-98
• 3 Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement.  Lancet. 1986;  1 307-310
• 4 Bland JM, Altman DG. Calculating correlation coefficients with repeated observations: Part 1 – correlation within subjects.  BMJ. 1995;  310 446
• 5 De Leva P. Adjustments to Zatsiorsky-Seluyanov's segment inertia parameters.  J Biomech. 1996;  29 1223-1230
• 6 Kolmogorov S, Duplischeva O. Active drag, useful mechanical power output and hydrodynamic force coefficient in different swimming strokes at maximal velocity.  J Biomech. 1992;  25 311-318
• 7 Maglischo C, Maglischo E, Santos T. The relationship between the forward velocity of the centre of gravity and the forward velocity of the hip in the four competitive strokes.  J Swim Res. 1987;  3 11-17
• 8 Mason B, Tong Z, Richards R. Propulsion in the Butterfly stroke. In: MacLaren D, Reilly T, Lees A (eds) Biomechanics and Medicine in Swimming VI. London: E & EF Spon 1992: 81-86
• 9 Payton C, Bartlett R. Estimating propulsive forces in swimming from three- dimensional kinematic data.  J Sports Sci. 1995;  13 447-454
• 10 Plagenhoef SC. Methods for obtaining kinetic data to analyze human motions. In: Martin TP (ed) Biomechanics of Sport - Selected Readings. New York: State University of New York 1976: 124-133
• 11 Psycharakis SG, Sanders RH. Validity of the use of a fixed point for intracycle velocity calculations in swimming.  J Sci Med Sport. 2009;  12 262-526
• 12 Schnitzler C, Seifert L, Ernwein V, Chollet D. Arm coordination adaptations assessment in swimming.  Int J Sports Med. 2007;  28 1-7
• 13 Takagi H, Sugimoto S, Nishijima N, Wilson B. Differences in stroke phases, arm-leg coordination and velocity fluctuation due to event, gender and performance level in breaststroke.  Sports Biomech. 2004;  3 15-27
• 14 Winter D. Biomechanics and Motor Control of Human Movement (3^rd ed). Waterloo: Wiley 2005

Correspondence