Acute ligamentous injuries to the lower extremity are pervasive in athletics and can have long-term negative health effects, putting an athlete at increased risk of reinjury in the short term and reduced quality of life in the long term. After injury, inflammation, instability, pain, and apprehension can result in changes in an athlete's movement mechanics. Consequential changes to movement mechanics are believed to be a primary cause for reduced performance and increased rates of reinjury. Traditional rehabilitation methods focus on local joint mechanical or muscle adaptations but do not address neuroplasticity associated with injury and motor recovery. Emerging evidence of neuroplasticity associated with injury recommends using motor learning strategies to bolster rehabilitation outcomes,1 reduce time loss from injury, improve functional performance, and promote the acquisition, retention, and transfer of motor skills.1,2 Herein we will review four key motor learning concepts: external focus of attention, implicit learning, differential learning, and self-controlled learning. Interested readers are encouraged to review Wulf and Lewthwaite3 for more motor learning applications and further background information.
External Focus of Attention
In rehabilitation, feedback and instructions are commonly given that direct the athletes' attention to various aspects of their movements. It has been generally assumed that athletes benefit from explicit verbal information on how to best perform a motor skill.4 In the motor learning domain, this type of attentional focus is defined as internal focus.5 Frequently given instructions are “keep your knee over the toe,” “land with a flexed knee,” “raise your knee to the level of your hip,” or “land with your feet shoulder-width apart.” Although there may be intuitive reasons that clinicians frequently give internal focus instructions, this approach may not facilitate the full potential to learn motor skills.6 Internal focus instructions induce conscious control of one's movements, which may interfere with the normal, automatic motor control processes and lead to a breakdown in the natural coordination of movements.3
To simplify, internal focus of attention is directed to the action itself, such as instructing athletes to focus on bending their knee more while performing a lunge task. External focus of attention is when the athlete's attention is directed to the effects of the action, such as instructing athletes to focus on touching their knee to the floor while performing the same task. External focus facilitates an automaticity during the movement, potentially shortening the time needed to learn the task.7,8 After anterior cruciate ligament reconstruction, athletes instructed to jump as far as possible during a single-leg hop task with an internal focus of attention (“concentrate on rapid knee extension”) had significantly less knee flexion angles on landing compared with athletes instructed with an external focus (“concentrate on pushing off the ground as hard as possible”).1 Providing athletes with an external focus of attention can improve performance,8 reduce task learning time, and potentially decrease risk factors for reinjury by accommodating an innate learning strategy.
Application: You want your athlete to perform drop landings off a box with more knee flexion.
Internal: “Jump off the box and try to bend your knees past 90 degrees when landing.”
External: “Jump off the box and try to touch your shorts to the top of the box.”
Explicit learning classically refers to a process of skill acquisition that begins with a verbal-cognitive phase in which the learner gains declarative knowledge of a movement before transitioning to an autonomous phase where movements are executed with little awareness or cognitive loading.9 Conversely, implicit learning refers to skill acquisition that capitalizes on more automatic processes that bypass the initial cognitive phase, leading to direct accumulation of procedural knowledge, often leaving the learner unable to describe the specific techniques of the skill.9
During the acute stages of rehabilitation, it may be necessary to provide more explicit, step-by-step instructions to athletes as they work to regain range of motion and neuromuscular control. When they transition to more complex tasks, it may be more beneficial to incorporate implicit learning strategies such as analogies, metaphors, or visual feedback to guide athletes through each exercise to promote more automatic processes. In a study by Benjaminse et al,10 men receiving visual feedback alone had improved skill acquisition and retention and adopted a landing strategy that included larger vertical ground reaction forces, knee flexion moment, knee range of motion, and ankle dorsiflexion angle.
Implicit learning has additionally been shown to reduce the load on working memory.11 Tasks that increase demand on working memory may be associated with increased risk of non-contact injuries.12 This is especially relevant to athletes returning to activity because the context of a sporting event elevates environmental distractors with increases in visual stimuli and unanticipated decision making, potentially increasing risk of injury. Training athletes to perform movements implicitly may reduce the risk associated with non-contact injuries brought on with elevated cognitive load during the injury event.
Application: Improve squat mechanics during a landing task.
Explicit: “Land with your head high, flat back, and knees over your toes.”
Implicit: “Land like a feather.”
Classic training approaches are based on the idea that “perfect practice makes perfect,” but differential learning challenges this by intentionally varying movement patterns with the goal of initiating self-organized learning. The principle of differential learning is to employ alternative methods for accomplishing a movement task, allowing athletes to find a motor solution that is individualized to their body type, environment, and sport. Rarely are tasks in sport performed repeatedly and without variability. Introducing differential learning strategies into exercise and rehabilitation may improve the transfer of skills from the clinical setting.1 Exposing an athlete to different environments, varying movement patterns after one or two repetitions, and exposing an athlete to as many different class-specific (eg, running, throwing, or jumping) combinations as possible are several easy to implement strategies.
Application: Improve kick mechanics in a soccer player.
Classic: “Perform 10 shots on goal from the top of the goal box, focusing on always hitting the same goal corner.”
Differential: “Perform 10 shots on goal, dribble before kick, run before kick, one arm to side, head sideways, vary the shot location, target location, surface (grass, turf), ball moving, ball stable, one-touch shot, dribble-shot, pass, and shoot.”
Typically, an athletic trainer will design a specific exercise routine that is suited to the stage of an athlete's rehabilitation. Athletes often have limited input on the tasks they perform, leading to poor compliance or low motivation. The goal of self-controlled learning is to allow athletes to take some ownership of their rehabilitation. Allowing athletes to select their own exercise routine for the day from a list of preapproved and stage-appropriate tasks will promote motivation and engagement. Additionally, giving athletes some control when they want to receive feedback optimizes the learning process by generating a reward structure that reinforces successful trials.13
Application: Improve ankle postural control.
Self-controlled learning: The athlete can choose three exercises from a list of five stage-appropriate balance tasks (eg, single leg squat 3 × 10; single leg stance, cup pick-ups 3 × 5; double leg stance on Bosu Ball with medicine ball toss 3 × 60 seconds; tandem stance on Airex pad with Virtual Reality (AIREX; Airex AG) 3 × 60 seconds; drop landing from 12-inch box on single leg 3 × 10).
Regaining full range of motion, strength, and cardiovascular endurance are important components of any rehabilitation program but may not be enough to address the neurological adaptations brought on through injury. The adoption of motor learning principles into current rehabilitation protocols may have a significant impact on athletes returning to participation, potentially reducing the risk of reinjury and improving quality of life.1
- Gokeler A, Neuhaus D, Benjaminse A, Grooms DR, Baumeister J. Principles of motor learning to support neuroplasticity after ACL injury: implications for optimizing performance and reducing risk of second ACL injury. Sports Med. 2019;49(6):853–865. doi:10.1007/s40279-019-01058-0 [CrossRef]
- Schmidt RA, Wrisberg CA. Motor Learning and Performance, 3rd ed. Human Kinetics; 2004.
- Wulf G, Lewthwaite R. Optimizing performance through intrinsic motivation and attention for learning: the OPTIMAL theory of motor learning. Psychon Bull Rev. 2016;23(5):1382–1414. doi:10.3758/s13423-015-0999-9 [CrossRef]
- Myklebust G, Engebretsen L, Braekken IH, Skjølberg A, Olsen O-E, Bahr R. Prevention of anterior cruciate ligament injuries in female team handball players: a prospective intervention study over three seasons. Clin J Sport Med. 2003;13(2):71–78. doi:10.1097/00042752-200303000-00002 [CrossRef]
- Wulf G, Höss M, Prinz W. Instructions for motor learning: differential effects of internal versus external focus of attention. J Mot Behav. 1998;30(2):169–179. doi:10.1080/00222899809601334 [CrossRef]
- Wulf G. Attentional focus and motor learning: a review of 15 years. Int Rev Sport Exerc Psychol. 2013;6(1):77–104. doi:10.1080/1750984X.2012.723728 [CrossRef]
- Wulf G, McNevin N, Shea CH. The automaticity of complex motor skill learning as a function of attentional focus. Q J Exp Psychol A. 2001;54(4):1143–1154. doi:10.1080/713756012 [CrossRef]
- Sherwood DE, Lohse KR, Healy AF. The effect of an external and internal focus of attention on dual-task performance. J Exp Psychol Hum Percept Perform. 2020;46(1):91–104. doi:10.1037/xhp0000698 [CrossRef].
- Kal E, Prosée R, Winters M, van der Kamp J. Does implicit motor learning lead to greater automatization of motor skills compared to explicit motor learning? A systematic review. PLOS ONE. 2018;13(9):e0203591. doi:10.1371/journal.pone.0203591 [CrossRef]
- Benjaminse A, Gokeler A, Dowling AV, et al. Optimization of the anterior cruciate ligament injury prevention paradigm: novel feedback techniques to enhance motor learning and reduce injury risk. J Orthop Sports Phys Ther. 2015;45(3):170–182. doi:10.2519/jospt.2015.4986 [CrossRef]
- Masters RS, Poolton JM, Maxwell JP, Raab M. Implicit motor learning and complex decision making in time-constrained environments. J Mot Behav. 2008;40(1):71–79. doi:10.3200/JMBR.40.1.71-80 [CrossRef]
- Herman DC, Barth JT. Drop-jump landing varies with baseline neurocognition: implications for anterior cruciate ligament injury risk and prevention. Am J Sports Med. 2016;44(9):2347–2353. doi:10.1177/0363546516657338 [CrossRef]
- Chiviacowsky S, Wulf G, Lewthwaite R. Self-controlled learning: the importance of protecting perceptions of competence. Front Psychol. 2012;3:458. doi:10.3389/fpsyg.2012.00458 [CrossRef]