©Journal of Sports Science and Medicine (2008) 7, 67-77 http://www.jssm.org Research article Searching for criteria in evaluating the monofin swimming turn from the perspective of coaching and improving technique Marek Rejman and Grazyna Borowska Department of Swimming,, University School of Physical Education, Wroclaw, Poland distance, and by approximately 7%, over a 1500m dis- Abstract tance. This study aims to analysise the selected kinematic parameters The swimming result consists of the start, the cov- of the monofin swimming turn. The high complexity of per- ering of distance and the turn. The analysis of monofin forming turns is hindered by the large surface of the monofin, swimming technique focuses on establishing its evalua- which disturbs control and sense of the body in water. A lack of tion criteria as per kinematics, (Gautier et al., 2004; Re- objective data available on monofin swimming turns has re- jman et al., 2003; Shuping, 1989; Tze Chung Luk et al., sulted in field research connected with the specification of pa- rameters needed for the evaluation of the technique. Therefore, 1999), dynamics (Rejman, 1999), and modelling (Re- turns observed in elite swimmers contain underlying conclusions jman and Ochman, 2007; Wu, 1971). The specific char- for objective criteria, ensuring the highest level of coaching and acter of monofin swimming also constitutes the basis for the improving of turns in young swimmers. Six, high level, male interpretation of mechanisms explaining the nature of swimmers participated in the study. The subject of the analysis locomotion in water (Arellano, 1999; Colman et al., was the fastest turn, from one out of three trial turns made after 1999; Ungerechts, 1982). The lack of an objective analy- swimming a distance of 25 m. Images of the turns were col- sis of monofin swimming turn results in the undertaking lected from two cameras located under water in accordance with of studies on the issue of technique evaluation. At the the procedures of the previous analyses of freestyle turns. The ® same time, the novel character of the research under- images were digitized and analysed by the SIMI - Movement Analysis System. The interdependency of the total turn time and taken, calls for interpretation of the results obtained on the remaining recorded parameters, constituted the basis for the basis of the analysis of freestyle turns. analysis of the kinematic parameters of five turn phases. The It is assumed that the structure of the turn tech- interdependency was measured using r-Pearson’s correlation nique in monofin swimming does not differ much from coefficients. The novel character of the subject covered in this the turn technique in freestyle swimming (Figure 1). Con- study, forced interpretation of the results on the basis of turn sequently, there is the same phase division in both types analyses in freestyle swimming. The results allow for the crea- of turn: swimming-in, rotation, wall contact, push-off, tion of a diagram outlinig area of search for an effective and glide and commencement of stroking (Costill et al., efficient monofin swimming turn mechanism. The activities 1992). The total turn time in freestyle swimming is ap- performed from the moment of wall contact until the com- mencement of stroking seem to be crucial for turn improvement. proximately 8 sec. In monofin swimming the total turn A strong belief has resulted that, the correct monofin swimming time is shorter. Within the space of a few seconds the turn, is more than just a simple consequence of the fastest per- swimmer must (apart from swimming-in and swimming- formance of all its components. The most important criteria in out from the wall) make a rotation around the transverse evaluating the quality of the monofin swimming turn are: striv- axis, push off the wall and turn the body around the longi- ing for the optimal extension of wall contact time, push-off time tudinal axis during the impulse and first meters of the and glide time. gliding phase. The large surface of the monofin addition- ally hinders the control of the sense of body in the space. Key words: Monofin, turn, kinematics, technique evaluation. The high complexity of a turn, which is to be made in a relatively short time, requires the full automation of movements by the swimmer. It has been well proven that Introduction the correct turn may help in improving the results of swimming performance. Assuming that the turns take The technique of monofin swimming consists of the approximately 36% of freestyle race time in a short oscillatory movements of the trunk and legs in the sagit- course (Thayer and Hay, 1984), and 31% in a 50m pool tal plane, while in a prone position. The scope of move- (Arellano et al., 1994), it has been proven that the reserve ment increases, from the shoulders in the direction of the gained due to correct turns, results in a clear difference in centre of the swimmer’s mass and feet, which transfer preformance time. The time needed to cover the distance torque to the monofin’s surface. This being approxi- of 1500m in 50m-long pool (29 turns), may be reduced by mately twenty times greater than on the surface of feet, even 5.4 sec. (Chow et al., 1984). producing propulsion, in swimming without fins. The Within the scope of the arguments formulated, dimension of the monofin and the structure of the swim- there is a well-grounded need to specify factors determin- ming movements are the reasons why average speed in ing the quality of the monofin swimming turn. Therefore monofin swimming exceeds the speed of crawl swim- the aims of this study have been formulated in a direction ming by approximately 24%, on average over a 50m outlined by the analysis of the chosen kinematic Received: 14 June 2007 / Accepted: 20 November 2007 / Published (online): 01 March 2008 68 Evaluation of the turn technique in monofin swimming Figure 1. The illustration of assumption that the structure of the turn technique in the monofin swim- ming does not differ much from the turn technique in freestyle swimming. The particular phases of free- style (Ungerechts, 2002) and monofin (stick figure) were compared: swimming-in (I), rotation (II,III,IV), push-off (V,VI) glide (VII) and commencement of stroking (VIII). parameters of the monofin turn. A biomechanical analysis are a source of information for facilitating a training proc- served to formulate the criteria for turn quality in respect ess, which can then be addressed to swimmers at a lower to its efficiency, measured through minimizing the per- stage of their sporting career. Within the context pre- formance time of the turn. Generalisation of the obtained sented, the didactic aspects of this study, by realization of results allowed creation of a diagram describing the basic the aims of the application, dominates the sporting aspects contributing factors to turn technique in monofin swim- outlined through the realization of typical cognitive aims. ming. The awareness of objective assessment of turn Information obtained in this way, should establish areas technique elements is essential in order to precisely for- of search regarding a mechanism for effective and effi- mulate the goal of learning and perfecting this important cient monofin swimming turns. Thus, this information element of swimming performance. The subject of analy- provides basis for more detailed description of the turn sis in this study is the turn technique performed by evaluation criteria in the future. swimmers of the highest level, and the results obtained 5 m MARKER 0,8 m CAM1 CAM2 1,5m 3 m 25 m Figure 2. The cameras arrangement and schema for equipment set-up The stick figures diagram is inserted in the schema. Rejman and Borowska 69 I VII II III IV V VI 1 2 3 Figure 3. Illustration outlining temporal parameters of the fin swimming turn, based on division into phase and sequence. Methods tracking of relocation of particular segments of the body, were applied to the bodies of the subjects. The points Six male swimmers - members of the Polish Monofin were located on both sides in the axes of the ankle, knee, Swimming Team -volunteered for the study. The average thigh and shoulder joints (Plagenhoef, 1971). The distal age of the participants was 17.2 ± 1.2 and they constituted part of the foot was also marked. The turns were analyzed a homogeneous group as per their somatic construction in two dimensions as is a standard in the analysis of (average body mass – 76.33 ± 6.25; average body height – monofin swimming technique (Rejman, 1999). The film- 1.84 ± 0.04). All the subjects represented the highest ing procedure was in accordance with the experiments international level. In a manner similar to the experiments carried out by other authors and applied repeatedly for carried out in the research on freestyle turns (e.g. analyses of turns in freestyle swimming (e.g., Blanksby et Blanksby et al., 1995), the research task consisted of three al., 1996a; 1996b; Mason and Pilcher, 2002; Takahashi et trial turns after swimming 25m. An analysis was made on al., 1983). The video material was obtained at a frequency one turn performed by each swimmer. This turn was se- of 50 Hz. The samples were analyzed based on digitaiza- lected based on the shortest total turn time. The swimmers tion of image, using the SIMI®-Germany system of were instructed to put maximum effort, into both the movement analysis. The procedure for recording video swimming speed and the speed of performing the turn. material and its analysis was in accordance with the ISO The turns were recorded by two digital video cam- 9001 standard (Figure 3).