Master Marta Nogal^1
1Józef Piłsudski University of Physical Education in Warsaw, Faculty of Physical Education and Health in Biała Podlaska. Department of Sports Sciences, Poland

Keywords: training, verbal feedback, trampolining.

Introduction. The process of motor learning has fascinated scientists for many years. A lot of motor learning theories have been formulated over this period. A lot of researchers attempted to explain mechanism of motor skill acquisition and factors affecting its effectiveness [2, 4, 5, 8]. The cognitive theory is considered to be the most important theory related to the motor learning process. External feedback constitutes the basis of this process. From the very beginning, the process of learning in each sport ought to be aimed at enabling athletes to develop exercise-related movement habits that would allow them to perform more difficult and more complex motor skills at further stages of training. In particular, it can be related to trampolining, which is a highly complex and difficult sport.

When examining a learning process, simple skills were usually used. In sport, there are more difficult and complex motor skills that make it impossible to implement rules that refer to the learning of simple skills in sports training [9]. Attempts were made at identifying variables that contribute to fast and durable learning the most. The effects of the following variables were analysed first and foremost: verbal feedback, visual feedback and kinaesthetic feedback [3, 5].

The process of learning in sports with complex motor skills can be effective owing to extrinsic feedback. Two types of such feedback can be distinguished, i.e. knowledge of results (KR) and knowledge of performance (KP). KR refers to success in performance in relation to the goal both in quantitative and qualitative terms. KP is defined as kinematic or kinetic information that refers to aspects of the movement pattern. Verbal feedback is the type of KP commonly used in the process of motor learning [3]. A number of researchers claimed that instructions provided prior to, during and after motor skill performance played a significant role in making the learning process effective [6, 7, 8, 10]. Therefore, the question arises whether feedback on all errors or just on key elements should be provided. Despite numerous studies on both simple and complex skills, there is still a scarcity of data that would clearly indicate which type of feedback ought to be provided. It is noteworthy that not enough empirical research has been conducted on learning complex motor skills related to the so-called early sports (including trampolining) as well as to groups at early stages of training.

Objective. This study sought to extend the knowledge about the influence of verbal feedback related to errors in the performance of the whole motor skill, its phases and key elements on the effectiveness of learning complex motor skills performed on the trampoline.

Research methods and organization. The experiment and experts’ evaluation were applied as the research methods. Moreover, kinematic assessment of pike jump performance technique was carried out. The study included children aged 6-8 (n=45).

At the beginning of the research, a preliminary experiment that involved 24 training sessions was carried out. The sessions took place three times a week (90 minutes per session). At this stage, the goal was to provide comprehensive conditioning and coordination training. After the preliminary experiment, pike jump (PJ) performance technique was assessed (pre-test).

Next, the main experiment aimed at pike jump learning was performed. The task involved performing five trampoline jumps followed by a vertical jump with the body folding into a pike and both legs lifted off the trampoline to a horizontal position. During the vertical jump, the legs were parallel to or higher than the floor and the arms were extended towards the toes. Landing involved shock absorption using ankle, knee and hip joints.

In the case of the main experiment, the study participants were randomly assigned to one of the three groups. The person who assigned the subjects to the groups was not involved in conducting the main part of the study. In the first group (n=15) (126.7 cm ± 5.7 cm; 23.6 kg ± 1.4 kg), the subjects received verbal feedback on errors concerning the whole motor skill performance (EWS). In the second group (n=15) (126.1 cm ± 5.2 cm; 23.3 kg ± 1.6 kg), the participants were provided with verbal feedback on errors made in particular phases of the skill performance (EPS). In the third group (n=15) (125.8 cm ± 6.0 cm; 22.9 kg ± 1.5 kg), the subjects received verbal feedback on errors that occurred in key elements (EKE). The study involved 18 training sessions. The sessions took place three times a week (90 minutes per session). During each session, the subjects performed 3 sets of 5 repetitions. After each session, they received verbal feedback on errors. The experiment was conducted by one coach. Immediately after the learning process, pike jump performance technique was evaluated (post-test). Afterwards, re-evaluation was performed one week following the process completion (retention test). Also, the transfer test was carried out, during which the participants were asked to perform trampoline pike jump with the trampoline positioned on the ground level. During the pre-test, post-test, retention test and transfer test, the subjects were given no feedback at all.  

Technique was evaluated by experts (n=3), i.e. licensed FIG judges. Arithmetic mean was calculated from the three evaluations. The mean was used in the analysis of research results. Prior to rating the performance, the experts got acquainted with assessment criteria. For each minor error they deducted 0.1 pts, for a medium one – 0.2-0.3 pts, while for a major error they deducted 0.5 pts from the maximal score. The judges focused on errors that occurred during the take-off, flight and landing, e.g. horizontal displacement, pulling bent knees to the chest, pulling the legs to the chest at the end of the ascending phase, opening at the end of the descending phase, not standing upright after landing or uncontrolled movements in the out-bounce.

In addition, kinematic assessment of pike jump performance technique was conducted. The analysis included joint angles as well as resultant velocities of body biolinks and the centre of gravity. The APAS 2000 analysis system was applied to measure, record and analyse movement in three planes. One 100 Hz camera was used to record the jumps. The camera was positioned 8 m away at an angle of 45⁰ relative to the perpendicular line going through the centre of the trampoline, above the level of the trampoline surface. The films were recorded and analysed in AVI (Audio Video Interleave) format.

The normality of distribution and homogeneity of variances were tested with the Shapiro-Wilk test. One-way ANOVA was used to estimate statistically significant differences between the measurements. Statistical significance was set at p<0.05. The Fisher post-hoc test was applied to assess significance of differences between mean results. The results were analysed with the use of Statistica (STATISTICA, version 12) software.

Results and discussion. Kinematic analysis of pike jump performance technique

In order to identify key technical elements that mainly determine the effectiveness of learning complex motor skills, a kinematic analysis of the phases of movement structure was performed. Two indices were analysed, i.e. joint angles and resultant velocities. Sadowski et al.  [7] singled out the following phases in the movement structure: preparatory phase, main phase and final phase.

The so-called key elements of sports technique were identified in particular phases. In the preparatory phase, a launching body posture was distinguished (fig. 1 A), in the main phase involved multiplication of the body posture (fig. 1 B) and in the final phase, a landing body posture was distinguished (fig. 1 C).

Figure 1. Three key elements: A - Launching body posture when performing pike jump, B - Multiplication of the body postures when performing pike jump, C - Landing body posture when performing pike jump

The launching body posture  (fig. 1 A) involved standing with arms upward. The research results made it possible to distinguish the most characteristic kinematic indices of this posture. The following joint angle parameters were observed: shank-thigh angle – 175^o, thigh-trunk angle – 180^o, trunk-shoulder angle – 173^o. Resultant velocity of the gravity centre (GC) was 4.872m/s, whereas that of the ankle joint was 4.578m/s. Such kinematic indices of the launching body posture ensured proper performance of the jump and tucking.         

When it comes to the multiplication of the body postures (fig. 1 B), the following joint angle parameters were noted: shank-thigh angle – 178⁰, thigh-trunk angle – 46⁰, trunk-shoulder angle – 109⁰. Resultant velocity of the GC at the time of grabbing the ankle joints was 1.285m/s, while the velocity of the ankle joint was 1.780m/s.   

The landing body posture (fig. 1 C) when performing pike jump on the trampoline revealed the following joint angle parameters: shank-thigh – 176⁰, thigh-trunk – 179⁰, trunk-shoulder – 176⁰. Resultant velocity of the GC at the time of landing was 0.718m/s, while that of the ankle joint was  0.533m/s.

The influence of verbal feedback related to errors in the performance of the whole motor skill, its phases and key elements on the effectiveness of learning pike jump

In the pre-test, the differences noted were not significant – F(2.42)=.148, p=.863. The findings point to similar levels of motor skills in learners prior to commencing the process of learning pike jump (fig. 2).

Figure 2. Mean values of experts’ evaluation [pts] obtained for performing pike jump in the pre-test, post-test, retention test and transfer test

ANOVA confirmed that different types of feedback provided during the post-test resulted in statistically significant differences between groups EWS, EPS and EKE – F(2.42)=5.869, p=.006. In the post-test, the highest mean values were obtained by group EKE (8.46 pts), while the lowest scores were achieved by group EPS (8.12 pts). The differences between mean scores of groups EKE and EPS were statistically significant in favour of group EKE (p<.05). Significant differences were also noted between groups EKE and EWS (p<.05). In the retention test carried out one week after completing the process of learning, differences between mean scores of groups EWS, EPS and EKE were found – F(2.42)=3.445; p=.0411. Group EKE retained the highest mean score (8.36 pts), whereas the lowest one (8.08 pts) was noted in group EPS. The difference between these mean scores in these groups was statistically significant in favour of group EKE (p<.05). In the transfer test, differences between mean scores obtained by groups EWS, EPS and EKE were not statistically significant (F(2.42)=.949, p=.395) (fig. 2).

Based on the research results, it was stated that verbal feedback on errors in key elements was the most effective in the post-test and in the retention test. It may point to the fact that at an initial stage of learning, verbal feedback on the most important body positions may produce more effective outcomes. At this stage, learners may focus on correcting errors they were informed about. On the other hand, too general feedback may obstruct the process of learning. Similar observations were made by Tzetzis and Votsis [8]. Niźnikowski et al. [5] noted that providing feedback on key technical elements in the learning of complex motor skills is crucial in terms of performance quality. They also added that too much feedback may be overwhelming to the learner who, consequently, will be incapable of making full use of the received feedback. It is in line with the findings of the present study. In the transfer test, a decrease in the mean score was noted in the group that had obtained the highest mean values in the previous tests. Verbal feedback on errors in the whole motor skill performance helped to retain similar mean scores. It may indicate that feedback on key elements did not affect motor skill performance in changed conditions. On the other hand, feedback on errors in the whole motor skill performance provided during training sessions may disturb the process of learning. However, this type of feedback may lead to improved performance if motor skill performance conditions have been changed and if there is not any extrinsic feedback. In this case, the learner may make use of intrinsic feedback. Therefore, it is believed that future studies ought to include more and more complex skills, which may improve training processes considerably [1, 6, 9].

Conclusions. Effectiveness of learning complex motor skills is different depending on the type of verbal feedback (feedback on errors in the performance of either the whole motor skill or its phases or key elements). In the case of pike jump, feedback on errors in key elements results in more durable learning outcomes. Understanding the types of feedback may lead to better comprehension of its role in the process of learning complex motor skills. The study revealed that the effectiveness of pike jump learning depends on the type of verbal feedback concerning errors. The study does not exhaust this issue, so further research is needed to examine the effectiveness of various types of verbal feedback used in complex motor skills.

References

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Acknowledgements: The project was financed by Józef Piłsudski University of Physical Education in Warsaw within the research grant of the Department of Physical Education and Sport in Biała Podlaska No. MN II/2.

Corresponding author: marta.nogal@awf-bp.edu.pl

Abstract. The aim of this work was to broaden the knowledge about the influence of verbal feedback related to errors in the performance of the whole motor skill, its phases and key elements on the effectiveness of learning complex motor skills performed on the trampoline. The research included 45 children (n=45) aged 6-8. The experiment and experts’ evaluation were applied as the research methods and pike jump performance technique was assessed in terms of kinematics. The study participants were randomly divided into three groups. In the first group (n=15), the subjects received verbal feedback on errors concerning the whole motor skill performance. In the second group (n=15), the participants were provided with verbal feedback on errors made in particular phases of the skill performance. In the third group (n=15), the subjects received verbal feedback on errors that occurred in key elements. In the course of pike jump learning, an increase in mean scores was noted. Both in the post-test and the retention test, the highest mean score was observed in the third group (8.46 pts and 8.36 pts, respectively) (p<0.05). In the transfer test, a decrease in mean scores was noted in this group (8.18 pts). The effectiveness of learning complex motor skills is different depending on the type of verbal feedback. Feedback on errors made while performing key elements of the motor skill produces the longest lasting effects when it comes to pike jump learning.