Visual feedback to change rowing technique
Patria A Hume, Clara Soper and Jeroen Zeinstra provide the results of their review on the effectiveness of visual feedback on changing rowing technique
Visual and verbal feedback are methods of coaching in which the athlete is presented with visual and verbal cues. The aim of this review was to evaluate research on the effectiveness of visual feedback in improving motor skills - specifically in rowing. The review addresses the following questions:
Sports technique can have a large effect on performance. The technique of rowing has a great influence on the actual performance; therefore, much time is spent on improving the motor skills of rowers. The traditional method of training motor skills in rowing was a coach giving verbal cues during the rowing exercises. Lately motor skills are also trained by giving visual feedback through video images of expert rowers or images of the subject. Often the coach gives some verbal cues with the images. Recently a new feedback technique has been used by New Zealand rowing coaches - the AUT Goggles Training System (GTS ). The GTS consists of real-time video images projected on Sony Glasstron goggles from a telemetered video camera held by the coach. By using the GTS rowers can see themselves in action (see Figure 1) and receive some verbal feedback given by the coach through a communication system. Together with the 'traditional' motor skill training methods this type of training can hopefully contribute in the understanding of motor skills of a rower and subsequently performance will increase. Improved motor skills are believed to increase performance because of greater efficiency and a reduction of injuries through more controlled motor skills. The first step in this theory is to investigate whether visual and verbal cues really affect motor skill improvement and in what way motor skills can be measured and presented
The following questions were asked:
Thirteen original research articles, six review articles, one book chapter, and three masters theses were reviewed. The articles were located by searching Medline, SportsDiscus, Current Contents, Cihal, ABI/INFORM Global & ProQuest Direct databases and the internet (Journal of Biomechanics on line). Manual searches were performed looking through article reference lists. Key words were: visual feedback; verbal feedback; video feedback; sports; learning; teaching; and rowing.
What methods are currently used for technique feedback in sports?
Coaches use in most cases verbal cues to give their athletes direct feedback. In many cases verbal feedback is backed up by indirect visual feedback - images of training or competition are shown to the athletes afterwards. Verbal feedback by an expert can be added to the images when systems such as siliconCOACH® are used.
What biomechanics feedback techniques are used in rowing?
Since 2000, the Rowing New Zealand coaches and biomechanists have been using a method of presenting segmental interaction of the rowing stroke - the rowing segmental sequencing graph (Manning 2000). This graph, which presents the timing of the body and oar actions, is used in conjunction with slow motion video clips of the rowing technique. Improvements in the segmental sequencing have occurred during the two years of using this monitoring device at national training camps.
The effectiveness of visual feedback through the AUT Goggles Training System (GTS ) in changing ergometer rowing technique, and the resulting power output, was determined for the New Zealand junior men's rowing eight and a reserve. Pre- and post-training testing consisted of four one minute rowing trials at 25 strokes per minute with two minutes rest between trials:
Rowers trained with the goggles for 20 minutes a day for four days during ergometer rowing before being retested. Analysis of the rowing stroke was performed using siliconCOACH® and Rowperfect® software. Following four days of ergometer training with the GTS there was a 20 to 29% increase in power output across all four trials. There were no significant differences in stroke length, lumbo-pelvic angle or knee flexion angle for any trials. However, there was a trend for an increased pelvic angle at the catch (reduced lumbar flexion) in all trials (Reid et al. 2001).
A further study was conducted to assess the immediate and training effects of visual feedback through the GTS on lumbo-pelvic angle for eight female NZ national rowers during on-water rowing. A cross over design with alternate GTS and verbal feedback training sessions for five days was utilised. Testing before and after the training consisted of four one minute rowing trials at 28 strokes per minute with:
The GTS significantly reduced lumbo-pelvic angle for two scullers & three rowers (4.9 to 20.6% change in degrees) within one training session, however, there were no differences for ensembled averages for lumbo-pelvic angle. Verbal feedback changed lumbo-pelvic angle by 5.7 to 30.3% for two scullers and one rower. The results from these two studies support further use of the GTS as a tool for improving rowing technique (Soper et al. 2002).
Rowing technique can be made visible through different biomechanical parameters of which stroke smoothness is the most promising (Smith & Spinks 1995; Lu. et al. 1992)[4,5]. From a technical perspective, according to Smith & Spinks (1995) important biomechanical variables in rowing performance are mean propulsive power output per kilogram of body mass, propulsive work consistency, stroke-to-stroke consistency and stroke smoothness. Zatsiorsky (1991) calculated several indices to assess technique including effort coefficient, work efficiency, stroke efficiency, effort build-up gradient, maximal force build up gradient and efficient stroke force. Stuble et al. (1998) concluded the angle of the back plotted on the Y axis of a plot against the extension of the legs on the X axis provides good information about the technique of rowing.
Current research with Rowing New Zealand elite crews involves the use of an instrumented boat. Oar position, oar strain, foot stretcher force, boat velocity, and seat position information can be provided to the athletes and coaches.
What evidence is there that feedback methods actually improve performance?
There is evidence that verbal and visual feedback can improve performance. Tzetzis et al. (1999) randomly divided 75 students into three groups. Group A observed a video of a skilled model, group B viewed a video of their own performance with verbal instruction from a coach, and group C received traditional coach instruction. Motor skills were measured 24 hours after watching the video and practicing the skills. Motor skill improvement was largest in skiers as a result of both visual modelling and verbal feedback (Group B). Sanders et al. (1995) studied whether nine competitive swimmers could change their technique with video feedback given on two different sessions. Skilled performers made major technique changes in a modest period using both coaching and visual feedback.
Jambor (1995) saw an improvement in swimming skills for two 'college age' beginners who used the Interpersonal Process Recall method, which uses both visual and verbal cues, twice a week for 14 weeks. The technique is based on the students watching a video of their own performance with the teacher as a facilitator and asking questions to initiate the student to discuss the significance of certain movements. Through discussion between students, and between student and teacher, a better comprehension of technique was established. The students were in control of the video viewing - they could stop the video at any moment and start the discussion.
Video-computerized feedback combined with a video of an expert model has increased baseball hitting performance Leslie (1998). Swinnen et al. (1996) reported that real time visual feedback on five different training days was a good alternative to overcoming existing and thus preferred coordination modes for a cyclical elbow flexion-extension movement. Part of the changed coordination pattern was lost when the augmented feedback was removed.
Spinks (1994) examined the relationship between propulsive work, the propulsive work consistency and the mean propulsive power output per kilogram of body mass and kinetic feedback information for 9 novice, 23 good and 9 national male rowers. The rowers achieved a significant higher propulsive work consistency and mean propulsive power output per kilogram of body mass with the kinetic feedback information for a six-minute trial of maximal ergometer rowing. It was assumed that the rowers used the feedback information to maintain a more constant pattern of power output to increase propulsive output (Smith & Spinks 1995; Spinks 1994)[4,13].
How effective are coaching methods?
Knowledge of results or direct feedback in general, can contribute to the development of motor skills. Feedback is even more beneficial when the new motor skills are similar to known motor skills (Guadagnoli 2001; Darden 1997)[14-17]. New motor skills in rowing are an adaptation of existing motor skills. This means the subjects are reasonably familiar with the movement trajectory of the new motor skills. Darden (1997) examined the benefits of the demonstration of "wrong motor skills" together with some external feedback from a coach. The benefits proved to be greater than those of observing an expert model.
Darden (1997) also showed that both knowledge of result and watching an expert model contribute to developing motor skills. Tzetzis et al. (1999) produced the same result in the earlier mentioned research on skiers.
Vision provides a major input for developing coordination skills (Semmler 2001). Athletes seem to rely on vision for the coordination of movement more than on experience Semmler (2001). This conclusion was based on analysis of 83 acrobatic water jumps and a discussion with seven jumpers and their coaches who performed 51 other jumps. The jumps were recorded on video and the jumpers were interviewed. The analysis of the video was according to several criteria and the jumpers were asked to answer several questions and to discuss the answers with each other and the teacher.
Williams and Tannehill (1999) recommended that multimedia instruction could be used more as a supplement to traditional instruction instead of completely replacing it. They based their conclusion on a study on the effectiveness of a multimedia performance principle approach in training physical activity specialists to analyse and diagnose over-arm throwing movements. The discrimination, analytic and diagnostic response of six undergraduate physical education students was assessed. The students failed to interpret the instructional content of the multimedia presented to them, but they were able to distinguish correct from incorrect motor skills. Therefore, the use of verbal coaching added to direct visual feedback is possibly the most promising way of learning motor skills (Tannehill 1999).
With respect to rowing, Bompa (1980) has suggested that technique is in a certain way individual. Muscle force and productive yield should be considered in relation to a particular rowing style to conclude effectiveness. Isometric force output of certain movements is specifically related to the techniques of rowing (Bompa et al. 1990). Improved rowing technique of an individual does not automatically mean increased individual power output (Bompa 1980). A change in technique of one individual does not necessarily increase the total performance of the rowing crew automatically (Williams 1967). Greater performance in rowing through improved motor skills has to be analysed for the total crew. The crew has to be outbalanced to perform maximally (Williams 1967). This means solving possible wrong motor skills for one crewmember is not always responsible for an increase in performance of the whole crew. This suggests that the coach plays a vital role in adjusting the differences between the individual rowers.
The rate of learning is partially dependent upon of how familiar the subject is with the new movement pattern (Zanone 1992). Anderson et al. (2001) found that immediate knowledge of the result led to a significantly more accurate performance. However, immediate knowledge of the results also led to a significantly less accurate performance 24 hours later. In this study forty university students were asked to move a pen shaped stylus to a target whilst blindfolded. The knowledge of result dependency in motor skill learning was related to the familiarity with the task feedback - that is, the way in which subjects use knowledge of results depends on the way the subject is engaged before receiving knowledge of the results (Guadagnoli 2001). Guadagnoli (2001) divided 64 undergraduate students into four groups to perform a similar force production task. Two groups received 100% knowledge of the results with the other two groups receiving 20% knowledge of the results. One of each 20% and 100% groups had to estimate their error before receiving the knowledge of the results.
There is currently limited data on the effectiveness of various types of visual or verbal feedback on the improvement in rowing technique. Whether total performance of a crew increases through improved technique is uncertain. Further research should be conducted on the ability of an athlete to react to direct visual and verbal feedback.
Can too much feedback be confusing?
Too much visual feedback can also confuse participants. Franks et al. (1991) tested a training method that was intended to improve observational skills of soccer coaches. Twenty-eight licensed soccer coaches were tested prior and after a feedback training period. All coaches were incapable of remembering more than 40% of the information.
Knowledge of results or direct feedback in general, can contribute to the development of motor skills. Vision provides a major input for developing coordination skills. The use of verbal coaching added to direct visual feedback is possibly the most promising way of learning motor skills. Coaches should be encouraged to use real-time visual feedback.
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About the Author
Patria Hume is Director of the New Zealand Institute of Sport and Recreation Research at Auckland University of Technology, New Zealand. Patria`s research focuses on reducing sporting injuries and improving sport performance by investigating injury mechanisms, injury prevention methods, and biomechanics of sports techniques. Patria represented New Zealand in Rhythmic Gymnastics as a gymnast for six years. As a coach Patria`s gymnasts have competed at Olympics and have won medals at Commonwealth Games.
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