Feedback: Knowledge of Results

Early research conducted viewed that KR is essential for learning (Thorndike, 1931).  According to Schmidt (1982), performers cannot evaluate the outcome of skills without feedback information. Furthermore, it was stated that although KP is presented to signal movement patterns, performers do not have a reference against which to evaluate the feedback (KR), therefore no information about the success of the response. Work undertaken by Wulf & Shea (2004) identified KR as a key tool in improving motor skills and learning, but that the role of augmented feedback in the early stages of learning remains uncertain.

An analogy that is used often is that more precise, quantitative KR is in the main more effective than qualitative KR (Schmidt & Lee, 1999). Providing information about the magnitude of the error is beneficial to performers, but this can be enhanced if knowing that an error was made in a particular direction. This view was supported by Wulf & Shea (2004), stating that KR eliminates the need for error detection, and serves as error correction on subsequent trials. This was opposed by Kernodle & Carlton (1992) who found that the error correction cues group (KP) had the strongest learning effect compared to KR athletes when learning to throw a ball with the non dominant hand (p < 0.05). This suggests that combining KP with feedback specific to the task enhances skill acquisition more so than a form KR feedback. The timing of when feedback is administered was explored by Swinnen et al., (1990). Participants were given KR feedback instantaneously after task completion or after an eight second delay. After evaluation on several retention tasks, the investigation found that feedback given instantly after performance degraded learning. This could have been due to the feedback not being specific to the activity, and also the subjects did not have time to self reflect on certain aspects of the performance.

As previously stated, evidence exists that KR alone, and when combined with KP enhances performance (Viitasalo et al., 2001). It was reported in the investigation that KR alone improved target shooting outcome in novice shooters, which contrasts work by Amorose & Smith (2003) stating that less skilled performers may need more task specific KP feedback, as opposed to KR, as they do not have the necessary knowledge in order to perform effectively. However the findings of the investigation discuss that the skill of running target shooting is a complex skill and that KR alone is not the only way to facilitate learning.

According to Magill (1994) and Magill et al., (1991), performers do not benefit from feedback anymore than practicing the skill itself. In four experiments carried out by Magill et al., (1991), requiring sequential LED’s to be hit with a small bat upon illuminating, participants were administered verbal KR over different speeds of lighting. Results of all four experiments consistently showed that KR was not essential in learning the skill (p > 0.05), stating that the task itself provided the feedback necessary to perform the skill well, in a subconscious manner. This could have been due to the LED’s lighting up in order form left to right, so the participants were awaiting the same lighting sequence repeatedly, irrespective that the speed of illumination changed.

  • Overall, it appears that although KP and KR serve specific and differential functions within the learning process, both types of feedback adhere to the same principles in the way they affect the learning of motor skills (Wulf & Shea, 2004).

Feedback: Knowledge of Performance

One type of feedback most commonly used in skill acquisition studies is knowledge of performance (KP) and knowledge of results (KR).  KP refers to kinematic information about the actual execution of the movements performed (Gentile, 1972). The information provides a basis on which to assess the correctness of the movement, for example a sprinter sees a video replay of his or her performance during a training session.

There are two common forms of KP feedback; video or verbal feedback and self directed strategies (Schmidt and Lee, 2005). Video and self directed attentional focusing may be critical to actively involving athletes in the learning process, such as identifying errors that the teacher believes to be important (Cutton and Landin, 2007). Typical sport settings often limit the amount of instruction given due to participant numbers or time constraints, therefore if feedback is considered important in the learning process, performance could be enhanced through prompting athletes on task relevant movement cues.

With the improvement of video analysis software available, coaches have been increasingly using video as a method of administering feedback.  Early feedback research suggests that video analysis may be an ineffective means of presenting KP (Arnold and Rothstein, 1976). Explanations for the lack of effectiveness on skill acquisition may be due to overly complex information presented, failure to provide critical feedback about the skill and not providing enough information for error detection (Rucci and Tamporowski, 2010).

Video feedback can be more effective during movements which require interaction of various parameters than KR feedback to learn skills correctly. Gaudagnoli et al., (2002) reported that teachers provide video feedback to novice performers until they develop mental representations of skills as many cannot adequately evaluate errors on their own.  During the investigation, performed on amateur golf players, video feedback improved accuracy when learning the golf swing, measured as accuracy and distance on shots. There were two post-tests held, where on the first, the self guided group performed better than the KP with video group and the KP with verbal group (p < 0.001). However on the second post-test two weeks later, the two KP groups performed better, with KP with video feedback performing best (p < 0.001). These results suggest that video instruction had an initial negative impact on golf swing performance, but a long term effect on consistency and distance. This delayed improvement could have been due to learners becoming adjusted to a modified technique, although technique changes may well have been corrective, could have disrupted previously ingrained movements, and so therefore must be repeated over time in order to be successful.

In a study by Sanchez and Bampouras (2006) support the use of verbal feedback when undertaking complex motor skills. Recreational level participants who received verbal cues and KR when performing netball goal shooting significantly improved performance (p = 0.01) compared to the group which received KR alone. KP feedback was administered by an experienced qualified netball coach, so the coach was able to help athletes focus on specific flaws and provide appropriate correction than that of a less qualified coach. As a result, the feedback presented was of a high quality with regards to the skill of netball shooting, this would have allowed for more consistent content being delivered regarding error correction cues. This links in with work carried out by Amorose and Smith (2003) who examined the interpretation of feedback dependant upon experience of not only the teachers, but also the performers. It was hypothesised that lesser ability would require more feedback as they lack the task-specific knowledge in order to succeed hitting a softball whereas older subjects already possess this knowledge in order to self evaluate their performance and ignore the feedback provided by the coach. However the findings reported that there was no developmental difference between groups therefore both abilities interpreted the feedback as a cue of effort and ability.

Video feedback was supported by Viitasalo et al., (2001) when analysing the effects of feedback on the complex skill of running shooting in novice athletes. Performers that received video and graphic material about kinematics of their performance (KP) based on international shooters significantly improved shooting scores over 12 weeks (p < 0.05); however there was no significant difference when comparing feedback groups (p > 0.05). Of the two KP feedback groups, one received additional immediate and delayed video feedback with cues; this method of administering KP may have influenced its effects on motor learning. The extend of feedback was chosen on the experience of the shooting coaches without any scientific material available, due to lack of research in running target shooting, the feedback in the investigation may not have been optimal, which could have influenced the results.

The use of providing video and verbal feedback in order to benefit skill acquisition is in comparison with work by Kernodle and Carlton (1992) in a multiple-degree-of-freedom activity (overhand throw). In a similar investigation, the effects of self-controlled feedback were investigated by Janelle et al., (1997). Participants who received self-controlled feedback showed more improvements (p < 0.001) when learning to throw with their non dominant hand than those who received KR feedback, showing that information was retained for longer. The procedure of the investigation consisted of 100 trials with 10 blocks of 10 performed, it was implicated that from the protocol used, KR and KP video feedback indirectly focused learners as the trials progressed and participants may have become dependent on the feedback. Whereas when participants are placed in a self controlled environment, they are actively involved in the learning plan, and therefore must assume responsibility over their actions which may lead to increased motivation to perform well.

Support for this came from Cutton and Landin (2007) when investigating the effects of self talk on learning the tennis forehand in undergraduate students. Students were administered verbal cues to say upon execution of shots regarding critical components of the stroke, which resulted in self talk strategies enhancing the learning process of open skills (p < 0.001) even when KP was available from an external source, such as a coach. Three instructors were used within the investigation and although they were trained to use teaching scripts by tennis instructors, each could have interpreted the feedback statement given to their own. It may have been more reliable to use one instructor throughout the investigation to provide feedback on a more consistent basis than employing a number of coaches.

Not only do these results support the notion that self controlled  KP can be effective, but can also be used in addition to KR as an effective means to enhance skill acquisition, improve performance and motivate performers.

How To Increase Countermovement Jump & Spike Jump: Application to Volleyball Players

Volleyball is characterised by short and frequent explosive activities such as jumping, diving, and ball play. Considering the importance of jumping activities to the performance in volleyball, both countermovement jump (CMJ) and spike jump (SPJ) ability are considered important performance indicators and are the primary performance indicators that strength and conditioning programmes aim to enhance.

A study in the Journal of Strength and Conditioning Research examined changes in performance indicators relating to strength and speed-strength development over 2 years. Specific resistance training protocols weren’t recorded, however typical training schedules during training and international competitive periods were presented as athletes transitioned from U21 to senior international level. Typical training schedules consisted of 2-3 strength & power sessions per week during training and competitive periods. 1RM Clean, 3RM Squat, CMJ, depth jump (DJ), SPJ with approach, jump squat at bodyweight and plus 50% bodyweight, and anthropometric tests were conducted as performance variables.

Results showed that 1RM Clean increased by 15% and 3RM Squat by 29% over the 2-year period. There was a reduction in skinfold summation combined with large increases in lean mass ratio. Jump height for the CMJ, DJ, and SPJ increased significantly by 6-9 cm over the 2-year period. Bodyweight and 50% bodyweight jump squat performance increased significantly for measured parameters such as peak power, relative peak power, force, and jump height (8%).

The results of the study provide strength and conditioning coaches a rationale to prioritise increasing fat free mass, increasing stretch-load tolerance through depth jumping, and increasing strength and loaded speed-strength performance.

In a sport where relative power is of primary importance, training should be aimed at increasing strength and speed-strength, while maintaining very low fat mass. Low fat mass is not only important for jump and relative power, but also to reduce stress placed on the musculoskeletal system in the jump-landing. Fat mass places extra stress on the body when landing from a height, because the extra mass increases the kinetic stress upon landing and cannot contribute to absorption or deceleration in the landing activity.

Considerable improvements in the athletes support the justification of the CMJ and SPJ as key performance indicators for elite volleyball. Strength and conditioning coaches should focus on improving stretch load tolerance in DJ, showing a strong relationship between developing DJ ability and improving both CMJ and SPJ. Its is also important for athletes to apply force quickly and generate high power outputs, likely best developed through Olympic style lifting and jump squat methods.

Sheppard, J., et al. Changes in Strength and Power Qualities over Two Years in Volleyball Players Transitioning from Junior to Senior National Team. Journal of Strength and Conditioning Research 26(1): 152-157, 2012.