Application of Attention Focus in Rehabilitation to Promote Motor Performance and Motor Learning

Abstract

Attention focus plays an essential role in promoting motor performance and motor learning. There are two types of attention focus: internal focus and external focus. Internal focus refers to direct attention inside the body while external focus refers to direct attention outside the body. Several studies have reported that external focus positively affects motor performance and motor learning by promoting automatic control. The mechanisms of attention focus have been examined using electromyography (EMG), electroencephalography (EEG), and functional magnetic resonance imaging (fMRI). During rehabilitation, therapists promote patients’ movement acquisition and motor learning. This chapter reviews the application of attention focus in rehabilitation to promote motor performance and motor learning in patients.

1. Introduction

When a person exercises, their attention is somewhere else. Attention focus describes a change in behavior depending on the focus of one’s attention. Attention focus can be divided into internal focus and external focus. Internal focus is defined as “instructions related to the learner’s own body movements.” External focus is defined as “instructions related to the effects of the performer’s actions on the environment, for example, the experimental apparatus” [1]. Several studies have reported that external focus is more effective for performance and motor learning than internal focus. The positive effects of external focus are explained by the constrained action hypothesis (CAH). The CAH states that “trying to consciously control one’s movements constrains the motor system by interfering with automatic motor control processes that would “normally” regulate the movement” [2]. Based on the CAH, internal focus promotes conscious control of movement by directing attention to inside the body, inhibiting the automatic control of movement, resulting in a negative effect. In contrast, external focus positively inhibits conscious control of movements and promotes automatic control of movements by directing the individual’s attention externally. In this chapter, the effects of internal focus and external focus on changes in performance and motor learning are summarized. In addition, the application of attention focus in the field of rehabilitation is discussed.

1.1 The origin of attention focus

The first study regarding attention focus was reported by Wulf et al. [1] who examined the effects of internal focus and external focus on motor learning during a slalom movement using a ski simulator. The participants moved rhythmically to the left and right with as wide amplitude as possible. The study was divided into three groups: internal focus, external focus, and a control group who did not receive instructions regarding attention focus. Participants in the internal focus group were instructed to “try to exert force on the outer foot.” Participants in the external focus group were instructed to “try to exert force on the outer wheels as long as the platform moved in the respective direction.” Therefore, the attention of the participants in the internal focus group was directed to their feet and that in the external focus group was directed to the ski simulator. The amplitude of the movements increased with task performance, and greater learning retention was observed in the external focus group than in the internal focus and control groups. The task performance was the worst in the internal focus group. Although changes in performance due to attention had been examined previously, the classification of attention focus as internal focus and external focus led to the development of studies regarding attention focus. This inaugural study also reported the positive effects of paying attention to the outside of the body (external focus) and the negative effects of paying attention to the inside of the body (internal focus). Subsequently, the effects of attention focus during various tasks have been examined.

1.2 Attention focus during balance control and sports activities

The effects of attention focus on healthy participants have been examined during several tasks that require accuracy, including balance tasks and sports activities. Several studies have examined the effects of attention focus on performance and motor learning during center of pressure sway (COP) control using a stabilometer. As it is difficult to observe the effect of attention focus during simple tasks [3], studies that include healthy young participants often include difficult postural tasks or tasks performed on rough surfaces. For example, previously-used tasks include posture maintenance while grasping an object [4, 5] and maintaining a single leg standing position on a rough surface [6, 7]. During these tasks, the attention focus can be directed externally via showing the participant the COP cursor measured by the stabilometer or instructing the participant to keep the object as still as possible. In contrast, the attention focus can be directed internally by focusing the grasping hand or the entire body during posture control. A previous study that examined the effects of attention focus during balance tasks reported the positive effects of external focus [8]. The effects of attention focus during postural control tasks have also been examined in elderly participants [9], in which the same positive motor learning effects are observed. Elderly people often suffer fractures due to falls and require rehabilitation [10]. Therefore, it is expected that external focus can promote the improvement of postural control during rehabilitation for fall prevention.

The effects of internal focus and external focus have also been examined during sports activities that do not require open skill, such as golf putting, dart shooting, and basketball free throws. In golf putting, internal focus directs attention to the arm or the putting motion and external focus directs attention to the golf club or the course of the ball. Several studies have reported more favorable motor learning via external focus than when internal focus or control conditions are used [11, 12]. External focus improves putting accuracy, kinematic parameters [13], and muscle activity as measured by electromyography (EMG) [14], as it smooths the putting motion and decreases muscle activity in the lower extremities. Less muscle activity is required to complete efficient movements. These results indicate that external focus promotes accurate and efficient golf putting. Similar results have been reported regarding the effects of external focus on motor learning during dart shooting and basketball free throws. Internal focus was directed to the participant’s wrists and hands, while external focus was directed to the dart trajectory (during dart shooting) or the basket (during basketball free throws). External focus increased movement accuracy, improved kinematic parameters, and decreased muscle activity in both activities [15, 16, 17], suggesting that external focus is efficient for motor learning of sports movements that require accuracy and may contribute to the acquisition of more accurate movements. Therefore, verbal instructions regarding external focus may be effective for the rehabilitation of athletes.

1.3 The effects of attention focus on muscle strength and endurance

The effects of attention focus on muscle strength [18], muscular endurance [19], and tasks requiring accuracy have been reported. Several studies have reported short-term gains in muscle strength when external focus is used. External focus increased muscle strength during grip strength [20] and squat and deadlift [21] activities. In addition to muscle strength, changes in muscle activity (measured using EMG) have also been reported [22], suggesting that unnecessary muscle activity during movement is reduced by external focus, promoting more efficient movements. These findings also indicate that the use of external focus results in efficient exercises that encourage selective participation of the muscle groups necessary for the movement. Therefore, muscle strengthening training should be conducted using external focus. However, a previous study reported decreased muscle activity but no improvement in muscle strength when the same muscle force was exerted [23]. No study has reported the positive effects of consistent external focus, and there is no clear difference between internal focus and external focus when examining the long-term effects of training. However, when limited to the lower limb, muscle strength training using external focus has resulted in more favorable outcomes. One study [24] reported the positive effects of internal focus. Therefore, although there is currently no evidence to actively recommend external focus, there is a high possibility that the use of external focus provides more favorable muscle strengthening than internal focus. Patients undergoing rehabilitation due to orthopedic, cardiovascular, or other medical diseases often suffer muscle weakness due to disuse, and require efficient muscle strengthening training. Training using external focus is preferred for muscle strengthening training during rehabilitation.

The positive effects of external focus on muscular endurance have also been reported in several studies. Studies including repetitive exercises using the upper extremities, such as push-ups [20] and bench presses [25], and repetitive exercises using the lower extremities, such as squats and deadlifts [22, 26] have been reported. External focus is used to direct attention to the object during tasks that require the use of heavy objects, such as bench presses and squats. For tasks that do not require the use of an object, such as push-ups, the participants’ attention is directed to the external environment, and the participants are instructed to “push on the floor.” External focus has been reported to decrease the perception of fatigue and muscle tiredness [27] and it decreases muscle activity when the same muscle force is exerted [22], allowing for more efficient exercise. Increased efficiency prolongs the time to muscle fatigue. The long-term effects of attention focus on improving muscle endurance have not been examined and remain unclear. However, the short-term improvement in muscle endurance when external focus is used allows for more training sessions, resulting in more efficient training for the improvement of muscle strength and endurance. Patients undergoing rehabilitation often have weakened muscular endurance and strength. Therefore, the use of external focus is an efficient method for improving muscle strength and endurance during rehabilitation.

1.4 Dominance of attention focus

The dominance of attention focus has been reported recently as some individuals are internal focus-dominant and others are external focus-dominant. The relationships between abilities and the dominance of attention focus have been examined. Perkins-Ceccato et al. [28] reported that the dominance of attention focus depends on performance during a golf putting task, as a highly-skilled group had a better performance using external focus and a low-skill group had a better performance using internal focus. These results may be due to the fact that the low-skill group must pay attention to each step of the movement to perform it accurately. While beginners need to pay attention to the movement, external focus diverts their attention to the external environment. Participants in the low-skill group may have had insufficient attentional capacity to perform unfamiliar movements when external focus was used, resulting in a worse performance than that of the external focus group. Therefore, internal focus is effective in low-skill groups. Sakurada et al. [29] reported that the dominance of attention focus depends on the motor imagery ability in upper limb tracking tasks. The modality of motor imagery ability includes motor sensory imagery ability and visuomotor imagery ability. Participants with high motor-sensory imagery ability (motor-sensory dominant group) had more favorable motor learning using internal focus while participants with high visual imagery ability (visual dominant group) had more favorable motor learning using external focus. The modality of motor imagery ability and the dominance of attention focus are correlated. Therefore, the effects of internal focus were improved when the polarity of motor sensory dominance was increased. In contrast, the effects of external focus were improved when the polarity of visual dominance was increased. The cortical localization required in motor imagery and attention focus tasks is similar, which may account for the association between the modality of motor imagery ability and the dominance of attention focus. In the previous study, the motor-sensory dominant group had experience in sports that required closed skill, such as swimming and track and field. The visual dominant group had experience in sports that required open skill, such as volleyball and basketball. Therefore, the results of the study may be influenced by the participants’ experiences with motor learning and sports training. The visual-dominant group was much larger than the motor-sensory-dominant group [30], suggesting that the observed positive effects of external focus may be due to the difference in group size. Performing tasks with optimal attention strategies leads to better performance, improvement, and promotes motor learning effects. During rehabilitation, therapists are required to tailor interventions to individual patients, and interventions that consider the patient’s dominance of attention focus may improve the efficiency of rehabilitation. However, few studies regarding the dominance of attention focus have been reported and the results are inconsistent. Therefore, factors that determine the dominance of attention focus should be identified in future studies, and a scale to assess the dominance of attention focus should be developed.

1.5 Summary

The definitions of internal focus and external focus and the effects of attention focus during various movements based on previous studies that included healthy participants have been described. External focus is thought to be effective to promote the automaticity of movement during rehabilitation. However, the dominance of attention focus requires additional research. The consideration of the optimal attentional focus for patients during rehabilitation interventions will lead to effective and individualized rehabilitation services.

2. Neural basis of internal focus and external focus

Several studies have reported that brain function is related to performance [31, 32, 33] and motor learning [33, 34, 35]. Similarly, attention focus, which influences performance and motor learning, is expected to be related to brain function. Recently, encephalography (EEG), functional magnetic resonance imaging (fMRI), and functional near-infrared spectroscopy (fNIRS) have been used to examine the neural basis of attention focus. An understanding of the neural basis will not only clarify the existence of attention focus but will also be useful to consider new intervention methods for the modulation of brain activity via neuromodulation and other techniques.

2.1 Neural basis of attention focus

The neural basis of attention focus remains unclear. However, several reports have considered differences in brain functions as related to information processing and cognitive control. Raisbeck et al. [36] used fMRI to examine the effects of attention focus and the differences between internal focus and external focus during knee flexion and extension movements and found that internal focus activates motor-related areas (primary motor cortex and primary somatosensory cortex) and the cerebellar folium vermis. The use of internal focus increases the processing of somatosensory information and the activation of motor-sensory areas. The cerebellar folium vermis is active in internal cognition [37]. The activation of the cerebellar folium vermis may indicate increased cognitive demands. Internal focus increases cognitive demands as it promotes conscious control of the body. In contrast, activation of the anterior part of the lingual gyrus, occipital pole, occipital spindle gyrus, and parahippocampal gyrus was observed when external focus was used. The lingual gyrus and occipital pole are located in the occipital lobe and are involved in the processing of visual information [38]. The occipital spindle gyrus is involved in object recognition. The activation of these three regions indicates an increase in visual information due to the use of external focus. Furthermore, the parahippocampal gyrus is associated with visual memory [39], indicating visually dominant control with external focus. Another study that used EEG reported that external focus activates visual areas [40]. However, additional studies [40, 41] have reported that external focus activates motor-sensory areas, which is inconsistent with the results of the study by Raisbeck et al. [36]. The activation of motor-sensory areas by external focus is caused by the integration of visual and somatosensory information. The increase in visual information due to the use of external focus further increases the somatosensory information, activating the motor-sensory area during the processing of this information. This effect is related to the improvement of performance. Another area associated with this cognitive control is the activity of the frontal region. High theta wave activity in the frontal region of the EEG (FMθ) has been observed during concentration in cognitive tasks [42]. FMθ is also observed when external focus is used [40] and may reflect the effects of attention focus.

The neural basis of attention focus is based on previous studies that have considered the brain regions activated by internal focus and external focus to support function. However, several studies have suggested that the inactivation of brain regions or brain activity similar to that at rest may be efficient. Kuhn et al. [43] used transcranial magnetic stimulation (TMS) to examine the effects of attention focus and the intracortical inhibition of the primary motor cortex and found that external focus improves performance and activates inhibitory circuits in the primary motor cortex. The activity of the intracortical inhibitory circuits indicates the suppression of cortical activity, which may indicate that the suppression of unnecessary brain activity when external focus is used leads to the efficient execution of locally-activated cortical movements. Intracortical inhibition has also been shown to affect motor control, including coordinated movements [44]. Intracortical inhibition may represent the difference in motor control during internal focus and external focus. Therefore, both the activation and inactivation of brain regions may represent the neural basis of attention focus.

2.2 Neural basis of the dominance of attention focus

The neural basis of the dominance of attention focus has also been studied as differences in brain activity due to differences in optimal attention focus existing among individuals. Brain activity in participants using internal focus and those using external focus differed in a study in which participants were divided into internal focus-dominant and external focus-dominant groups based on their performance during an attention-focused task. The neural basis for the dominance of attention focus is related to information processing, cognitive processes, and the neural basis for attention focus. In a study using fNIRS, Sakurada et al. [45] reported that the right dorsolateral prefrontal cortex and somatosensory association cortex were less active in the internal focus-dominant and external focus-dominant groups when performing tasks at optimal attention focus (Figure 1). Participants with higher motor skills are able to perform movements with less neural activity than those with lower motor skills [46]. The dorsolateral prefrontal cortex and somatosensory association cortex are responsible for the integration of information and had low activity in this study, suggesting that the optimal attentional strategy enabled movement with less neural activity and less information processing, which indicate efficient brain activity. Furthermore, validation studies regarding event-related potentials using tactile and visual stimuli [47] and fNIRS [48] reported a relationship between the dominance of attention focus and processing of visual and tactile information, supporting the association between information processing and attention focus. In another study [49], EEG was used to examine the neural basis of the dominance of attention focus during a standing, postural control task (Figure 2). When internal focus was used, the left parietal lobe of participants in the internal focus-dominant group had higher theta wave activity. In contrast, the left frontal lobe of participants in the external focus group had higher theta wave activity when external focus was used. High theta wave activity in the parietal lobe has been reported to be associated with the processing of proprioceptive and superficial sensory information [50] and with attentional control [51]. Therefore, the internal focus-dominant group may have increased superficial sensory processing when internal focus is used and may have higher attentional control when directing attention to the inside of the body. In contrast, high theta wave activity in the frontal lobe has been reported to be associated with error detection [52] and cognitive control [53]. Therefore, the external focus-dominant group is more likely to selectively pay attention to the outside of the body when external focus is used and may perform postural control by error detection based on visual information. Studies regarding the neural basis of the dominance of attention focus indicate that sensory processing and cognitive processes are involved.

Figure 1.

Differences in brain activity in the optimal attentional strategy [45]. The red area in the parietal lobe, indicated by 4, is the somatosensory association cortex. The red area in the frontal lobe, indicated by 11, is the right dorsolateral prefrontal cortex. These two regions showed inactivity during optimal attentional focus.

Figure 2.

Differences in EEG activity between the internal focus-dominant group and the external focus-dominant group [49]. The red area is activated in participants in the internal focus-dominant group, while the blue area is activated in participants in the external focus-dominant group. When internal focus is used, the left parietal lobe is hyperactive in the internal focus-dominant group (a). When external focus is used, the left frontal lobe is highly active in the external focus-dominant group (b).

The results of these studies are contradictory as to whether higher or lower brain activity is more favorable. Some studies have reported that higher brain activity improves information processing [54] and cognitive control [55] by activating more neurons. However, during motor learning [56] and movement mastery [46], lower brain activity has been reported to imply more efficient neural activity. These studies also reported that optimal attentional strategies generated less brain activity and efficient neural activity, while greater neural activity resulted in better performance. Although it is clear that there is a difference in brain activity, further research is needed.

2.3 Summary

The neural bases of attention focus and attention focus dominance involve sensory information processing and cognitive processes. Changes in performance and motor learning due to attention focus occur in the same environment. Therefore, performance and brain activity change based on how information is processed and perceived. The ability to process information and cognitive control may determine the effects of attentional focus.

3. Attention focus during rehabilitation

The use of attention focus to improve performance and promote motor learning does not require specific equipment, making it extremely easy to implement in clinical trials. However, there is a high induction to internal focus during stroke rehabilitation [57], especially with feedback to patients, which is mainly internal focus [58, 59]. Therefore, attention focus may not be considered during rehabilitation. In addition to basic research regarding attention focus, clinical research has shown how rehabilitation can be conducted more effectively via the incorporation of attention focus. In this section, the effects of attention focus on patients with specific diseases are described.

3.1 Attention focus in patients with stroke

The effects of attention focus in patients with stroke have been examined during tasks such as upper limb movement, gait, and postural control. These tasks are related to movements that are impaired by stroke and that impede the return to home and social reintegration. The effects of attention focus have been examined during some accuracy-requiring tasks. More clinical studies have been conducted in patients with stroke with impaired dexterity than in patients with other diseases, and external focus has been reported as effective for patients with stroke. Gomes et al. [60] examined the effects of attention focus during upper limb tasks performed by patients with stroke. The temporal data acquisition instrument (TDAI) [61], an upper limb function test for patients with stroke, was used. The patients’ upper limb movements were captured using a camera, and the upper limb movement time, speed, and peak speed were calculated. The results indicate that internal focus and external focus promote motor learning compared to no instructions regarding attention focus in these patients. However, there were no differences in motor learning effects when internal focus or external focus were used. Patient performance is improved when external focus is performed after internal focus as patients with stroke are more likely to exercise conscious control of their movements [62]. Conversely, there was no improvement in performance when internal focus was used after external focus. This indicates that external focus suppresses conscious control of movement and improves performance. A negative correlation between conscious control and motor function has been reported in patients with stroke, and patient function improves when the patients depart from conscious control. As internal focus promotes the conscious control of movements [63, 64], it may be effective during early rehabilitation in patients with stroke who tend to exercise conscious control. Therefore, no differences in motor learning were found when internal focus or external focus were used. However, no reports regarding the relationship between the stage and severity of stroke and the dominance of attention focus have been reported. As the benefits of verbally instructing patients with stroke to pay attention during upper limb movements are clear, these patients should be instructed to pay attention to their upper limbs and the environment, instead of simply performing repetitive movements.

Kim et al. [65] reported that external focus increased step and stride lengths, walking speed, and load on the paralyzed leg when employed during walking in stroke patients. In this study, the subjects’ attention was directed to their lower limbs in the internal focus condition and to a line drawn on the floor in the external focus condition. The results indicate that external focus not only improves gait parameters such as step length, but also promote loading of the paralyzed lower extremity. This may be due to the fact that external focus promotes automatic gait control, resulting in a gait pattern similar to normal gait, which in turn promotes loading of the paralyzed lower limb. This is also important for the acquisition of symmetrical and stable gait [66], and the gait speed may have been improved by adopting a gait pattern similar to normal gait. In the rehabilitation of stroke patients, walking ability is an important factor that determines the outcome [67] and the patient’s level of living [68]. In addition, it has been reported that gait training for chronic stroke patients does not produce sufficient evidence for functional recovery [69], and efficient improvement of walking ability during the recovery phase is required. Furthermore, it is necessary to acquire automaticity of movements by various tasks for walking in stroke patients [68], and we believe that automating movements with external focus based on the restricted action hypothesis (CAH) is effective. Based on the above, we recommend an efficient intervention with external focus to improve walking ability in stroke patients.

Aloraini et al. [70] compared kinematic data obtained via motion capture and physiological data obtained via EMG during a step postural control task performed by patients with stroke using attention focus. The step task was performed under various step distance and step landing area conditions. When external focus was used, the body movement time, higher peak velocity, and time to peak velocity were shorter and the sway in the final position was smaller. The timing of muscle contraction was faster and the muscle contractions were smaller when external focus was used. Smaller muscle contractions indicate more efficient movements. These results indicate that external focus is effective for postural control in patients with stroke.

The effects of attention focus on motor learning during postural control tasks have also been reported. Kal et al. [71] examined the long-term effects of attention focus during postural control tasks in patients with stroke and found that although external focus improves performance in the short term, there were no significant differences between the long-term effects of internal focus and external focus. However, external focus was effective for patients with stroke who had improved balance, good sensory function, and a small attention capacity, indicating that the interventions should be tailored to individuals based on their optimal attention focus. These results agree with those of Perkins-Ceccato [28], who reported that external focus is effective in patients with high ability, and in an additional study [49] that reported that an internal focus-dominant group has high attentional control ability based on EEG activity. However, few studies have examined the long-term effects of attention focus, and sufficient evidence has not been obtained. More research is necessary. In addition, the symptoms of stroke vary according to the location of the lesion, and the effects and dominance of attention focus may differ based on the stroke symptoms. Therefore, more studies regarding the effects of attention focus in patients with different stroke symptoms are needed. Patients with stroke often suffer from impaired balance due to trunk dysfunction [72], and rehabilitation often includes interventions to improve balance ability [73]. Recently, virtual reality (VR) training [74, 75, 76] and electrical stimulation [77] have been investigated as new intervention methods for postural control in patients with stroke. Although these new intervention methods have been reported as effective, they require specific equipment and are difficult to implement in some situations. In comparison, attention focus can improve the postural control using only verbal instruction from therapists and requires no equipment or cost. Therefore, attention focus is clinically useful, and interventions should be conducted to promote performance and motor learning while seeking the optimal attention focus for postural control in patients with stroke.

The effects of attention focus on patients with stroke are not consistent. However, no studies have reported more favorable results without the use of attention focus compared to with the use of attention focus. Therefore, not considering the patient’s attention focus may impede performance improvement. The use of the patient’s optimal attention focus may lead to improved performance during the rehabilitation of patients with stroke.

3.2 Attention focus in patients with Parkinson’s disease

The effects of attention focus in patients with Parkinson’s disease have been examined during postural control and gait tasks. The main symptoms of Parkinson’s disease are tremors, rigidity, immobility, and impaired postural reflexes [78]. Impaired postural reflexes lead to decreased gait ability, resulting in decreased activities of daily living (ADL) [79]. Therefore, effective treatment methods for postural control and gait are essential for patients with Parkinson’s disease. Paradoxical gait [80] triggered by auditory or visual information is a well-known characteristic of Parkinson’s disease. Therefore, the performance of patients with Parkinson’s disease can be improved via exercises based on information from the environment. The use of external focus has positive effects in patients with Parkinson’s disease. Wulf et al. [81] studied the effects of attention focus during a standing posture control task on an unstable surface performed by patients with Parkinson’s disease and found that the use of external focus reduced postural sway compared to the control condition and the use of internal focus. Patients with Parkinson’s disease may have impaired endogenous regulation derived from the basal ganglia [82], resulting in poor performance during the use of internal focus. Therefore, the use of external focus is recommended for postural control training in patients with Parkinson’s disease during rehabilitation.

Beck et al. [83] also examined the effects of attention focus on gait during a dual-task in patients with Parkinson’s disease. The use of external focus decreased the step time, while the use of internal focus decreased the step length and gait speed, suggesting that external focus promotes automaticity during dual-task gait and that internal focus impairs the dual-task gait. The unified Parkinson’s disease rating scale motor section (UPDRS subsection III) was lower when external focus was used, indicating that external focus improves motor dysfunction caused by Parkinson’s disease. However, another study [84] reported increase in walking speed and stride length when internal focus was used, and that these improvements occurred without compromising the performance of the dual-task. The positive effects of internal focus are related to the pathogenesis of Parkinson’s disease. Parkinson’s disease causes a loss of automaticity in learned movements due to damage to the basal ganglia. Therefore, the use of external focus is less effective as it attempts to use reduced automaticity to perform movements, and conscious control (the use of internal focus) may be effective as a compensation for the loss of automaticity. In summary, both internal focus and external focus have been reported to be effective to improve gait in patients with Parkinson’s disease, even when the pathophysiology of Parkinson’s disease is considered. However, it is interesting to note that performance is changed by attention focus. It is necessary to clarify whether attention focus should be used to improve lost abilities or to promote the compensatory use of remaining abilities in patients with Parkinson’s disease.

The effects of attention focus on patients with Parkinson’s disease remain unclear. The relationship between attention focus and brain function requires further research. The effects of attention focus on patients with Parkinson’s disease may be revealed via future basic research as Parkinson’s disease is a neurodegenerative disease.

3.3 Attention focus in patients with orthopedic diseases

The effects of attention focus on patients with orthopedic diseases have been examined mainly in patients with anterior cruciate ligament (ACL) injuries [85]. ACL injuries are classified into contact and non-contact types. The non-contact type is caused by the force exerted on the knee joint during movements such as landing a jump or stepping [86, 87, 88, 89] and accounts for 70–75% of ACL injuries [90]. In patients with non-contact ACL injuries, safe landing is effective in preventing re-tears. The appropriate motor acquisition through motor learning is necessary after a non-contact ACL injury, and improving the efficiency of motor learning using attention focus is of great significance in the rehabilitation of patients with ACL injuries. Gokeler et al. [91] investigated the effects of attention focus on kinematic indices for single-leg jumping movements in patients after ACL reconstruction (ACLR) and found that safe landing movements (including the knee flexion angle at contact; peak knee flexion angle; total range of motion of the hip, knee, and ankle joints in the sagittal plane; and time to peak knee flexion angle) were significantly higher when external focus was used. However, this study examined temporary performance, and the motor learning effects are not clear. Appropriate movements are necessary for motor learning, and these movements are acquired through repetition. Therefore, movement training with the use of external focus is recommended during the rehabilitation of patients after ACLR.

Attention focus can also be used for ACL injury prevention [92, 93]. ACL injury prevention training reduces the risk of ACL injury [94] and improves the training of soccer players. The effects of attention focus on ACL injury prevention can be inferred from the kinematic effects of squatting in healthy participants. Benjaminse et al. [95] recommended interventions using external focus during single-leg squat and lunge movements. External focus has been shown to result in less knee joint eversion that can lead to ACL injuries. The use of repetitive movements that do not cause knee joint eversion may contribute to ACL injury prevention.

The effects of external focus are clearer in patients with musculoskeletal diseases than in patients with neurological diseases [96]. The contradictory findings regarding the use of attention focus in patients with neurological diseases may be related to brain function in attention focus. The lack of direct brain damage in patients with orthopedic injuries may account for similar effects of attention focus in these patients and in healthy participants. Although the effects of attention focus should be carefully examined and implemented in clinical practice, interventions using external focus are recommended, especially for patients with musculoskeletal disorders.

3.4 Attention focus in patients with developmental disabilities

The effects of attention focus in patients with developmental disabilities have been examined mainly in patients with developmental coordination disorder (DCD). DCD cannot be explained by general intellectual disabilities or specific congenital or acquired neurological disorders alone [97, 98]. Although several studies have shown the effectiveness of exercise therapy for patients with DCD [99, 100, 101, 102], there are reports of a lack of automaticity in movement [103], and additional intervention methods are needed. Jarus et al. [104] examined the effects of attention focus on motor learning effects in patients with DCD and in normally-developing children and found that normally-developing children had good retention of learning when external focus was used, though no significant difference was found between the use of internal focus and external focus in patients with DCD. These findings may be due to the fact that patients with DCD are unable to follow instructions accurately and have a lack of concentration and interest and do not indicate that attention focus is ineffective for patients with DCD. Internal focus and external focus may not be used appropriately in these patients as it is difficult for them to pay attention to a forced motor learning task, and patients with DCD are more likely to experience decreased concentration and effort due to repeated failures [105]. Therefore, experimental tasks such as repetitive movements may not be performed appropriately, and the effects of attention focus are difficult to study. Additional studies [106, 107] have reported that the use of external focus is as effective in patients with DCD as in normally-developing children. However, the data of patients DCD and normally-developing children were combined in these studies and were not verified using the data of patients with DCD alone. Therefore, the effects of attention focus on patients with DCD remain unclear and should be reexamined in future studies. The effects of attention focus on motor learning that can improve the motor skills of patients with DCD must also be investigated.

3.5 Summary

The effects of attention focus on patients with various disease have been studied. During rehabilitation, it is necessary to improve the movement ability and to promote motor learning. The clinical usefulness of attention focus to change those abilities is apparent. However, the study findings were inconsistent and should be interpreted with care. Further research is needed to clarify whether attention focus is disease-dependent or homeostatic.

4. Conclusion

In this chapter, the effects of internal focus and external focus on brain activity, performance, and motor learning are summarized. The effects of attention focus are unclear. However, the use of attention focus has the potential to improve patient performance during rehabilitation without the need for special equipment. Based on conflicting findings, both internal focus and external focus should be implemented during rehabilitation, and the most optimal attention focus for individual patients should be considered. The inclusion of attention focus during rehabilitation will make physical therapists’ interventions more effective.

Acknowledgments

We would like to thank Editage (www.editage.com) for English language editing. This work was supported by the Yuumi Memorial Foundation for Home Health Care and JSPS KAKENHI Grant Number JP20K11173.

Conflict of interest

The authors declare no conflicts of interest.

Appendices and nomenclature

EMG

electromyography

EEG

electroencephalography

fMRI

functional magnetic resonance imaging

CAH

constrained action hypothesis

COP

center of pressure

fNIRS

functional near-infrared spectroscopy

TMS

transcranial magnetic stimulation

TDAI

temporal data acquisition instrument

VR

virtual reality

ADL

activity of daily living

UPDRS

unified Parkinson’s disease rating scale

ACL

anterior cruciate ligament

ACLR

anterior cruciate ligament reconstruction

DCD

developmental coordination disorder