Visual Feedback and its effects on Biomechanics by Christopher Connelly

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[Christopher Connelly earned his Masters Degree in Exercise Science and Nutrition from Sacred Heart University where he competed for the D-I Track & Field / Cross Country team. Chris is currently an Athletic Development Intern at Athletic Lab]

There are many ways in which coaches try to help their athletes improve certain skills or movement patterns. There are many athletes that will struggle to learn new skills or motor patterns but there are certain tools that can be used to help this process. One tool that can be used to help skill acquisition and motor learning in athletes is visual feedback.

Visual feedback can be anything from a video of the athlete performing a task, a marker of distance or height achieved for a task such as vertical or broad jumps, or a time achieved for  a sprint or timed drill.  These pieces of information give the athlete knowledge of an executed task that they would not have had otherwise. This is also known as knowledge of results, and this information can be used to give them a better understanding of their performance to hopefully improve in the proceeding repetitions. There is research that has investigated the effect of knowledge of results on motor learning in athletes (Salmoni et al, 1984).  Knowledge of results has been found to help provide guidance, motivation, and help the formation of associations for the athlete’s performance. This can help guide the athlete towards the target behavior, which when combined with other processes such as simple repetition of a task can aid motor learning, skill acquisition and improve performance (Salmoni et al, 1984).

Video feedback is useful when trying to help the athlete associate how a movement or task felt while performing it to what it actually looked like (Liebermann et al, 2002). Many athletes struggle with being able to accurately feel what their body is doing in free space; this is called kinesthetic awareness. When athletes have access to seeing what their performance looked like and being able to relate that to what it felt like, they can make changes by thinking about what a better performance should feel like in comparison. For example, if a sprinter is shown a video of a sprint during practice and they need to improve their knee drive and posture, they can think about feeling the knees higher and torso more erect during their next sprint.

This information can be taken to the next level with video-based motion analysis (Liebermann et al, 2002) and electromyography (EMG) in real time. This involves equipment and software that is very expensive but can provide instantaneous information on joint movements and muscle activations during a given task. This allows the athlete to make more specific changes to their movements to hopefully aid in motor learning and improve performance. These resources allow the athlete to know if they need to use a specific muscle group more or less, along with certain joint movements they should achieve or avoid. For example, an athlete returning from an ACL surgery could be provided with EMG and 3D motion analysis to assess their frontal plane movement at the knee. If the athlete has dysfunction in their hip and core stability, they may lack the muscle activity needed from the gluteal muscles to keep the hips stable which would allow for increased femoral internal rotation and medial movement of the knee. These movements are considered to increase injury risk and would be shown during the analysis along with insufficient activation of the gluteal muscles. Now the athlete can see this and can consciously work on improving gluteal activation and knee frontal plane mechanics until their movement patterns are no longer showing increased risk for injury. This is achieved by motor learning of these new movement and neuromuscular patterns that was aided by the knowledge of what their body was previously doing.

There is also some evidence that skill or movement training in a virtual environment can also help improve motor learning and skill acquisition. This is accomplished through similar factors that would be experienced on the field, track, or whatever environment the athlete performs in, but without actually having to be in that environment (Liebermann et al, 2002).

An example of this kind of visual feedback can be seen in a study by Lim et al (2017). They had a group of runners that ran on a treadmill while stabilizing their gaze on a virtual target that was ahead of them. They used seven different sized boxes that the runners had to keep their gaze within during the running trials. Lim et al (2017) found that the runners had to adapt their running mechanics to provide the head stability needed to keep a consistent gaze. They increased their stride frequency and changed their levels of hip, knee and ankle flexion through the trials to meet the needs of head stability. These are important qualities, which through this type of training can improve running mechanics when running on complex terrain and allow adjustments to be made to make the motor patterns more efficient and attenuate any additional impact loading.

References:

Ford KR, Nguyen A-D, Hegedus EJ, Taylor JB. Vertical Jump Biomechanics Altered with Virtual Overhead Goal. J Appl Biomech. December 2016:1-22. doi:10.1123/jab.2016-0179.

Liebermann DG, Katz L, Hughes MD, Bartlett RM, McClements J, Franks IM. Advances in the application of information technology to sport performance. J Sports Sci. 2002;20(10):755-769. doi:10.1080/026404102320675611.

Lim J, Busa MA, Emmerik REA van, Hamill J. Adaptive changes in running kinematics as a function of head stability demands and their effect on shock transmission. J Biomech. 2016;0(0). doi:10.1016/j.jbiomech.2016.12.020.

Salmoni AW, Schmidt RA, Walter CB. Knowledge of results and motor learning: A review and critical reappraisal. Psychol Bull. 1984;95(3):355-386. doi:10.1037/0033-2909.95.3.355.

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