Daniel L. Eaves

Motor Imagery during Action Observation: A Brief Review of Evidence, Theory and Future Research Opportunities

Motor imagery (MI) and action observation (AO) have traditionally been viewed as two separate techniques, which can both be used alongside physical practice to enhance motor learning and rehabilitation. Their independent use has largely been shown to be effective, and there is clear evidence that the two processes can elicit similar activity in the motor system. Building on these well-established findings, research has now turned to investigate the effects of their combined use. In this article, we first review the available neurophysiological and behavioral evidence for the effects of combined action observation and motor imagery (AO+MI) on motor processes. We next describe a conceptual framework for their combined use, and then discuss several areas for future research into AO+MI processes. In this review, we advocate a more integrated approach to AO+MI techniques than has previously been adopted by movement scientists and practitioners alike. We hope that this early review of an emergent body of research, along with a related set of research questions, can inspire new work in this area. We are optimistic that future research will further confirm if, how, and when this combined approach to AO+MI can be more effective in motor learning and rehabilitation settings, relative to the more traditional application of MI or AO independently.

Motor imagery during action observation modulates automatic imitation effects in rhythmical actions

We have previously shown that passively observing a task-irrelevant rhythmical action can bias the cycle time of a subsequently executed rhythmical action. Here we use the same paradigm to investigate the impact of different forms of motor imagery (MI) during action observation (AO) on this automatic imitation (AI) effect. Participants saw a picture of the instructed action followed by a rhythmical distractor movie, wherein cycle time was subtly manipulated across trials. They then executed the instructed rhythmical action. When participants imagined performing the instructed action in synchrony with the distractor action (AO + MI), a strong imitation bias was found that was significantly greater than in our previous study. The bias was pronounced equally for compatible and incompatible trials, wherein observed and imagined actions were different in type (e.g., face washing vs. painting) or plane of movement, or both. In contrast, no imitation bias was observed when MI conflicted with AO. In Experiment 2, motor execution synchronized with AO produced a stronger imitation bias compared to AO + MI, showing an advantage in synchronization for overt execution over MI. Furthermore, the bias was stronger when participants synchronized the instructed action with the distractor movie, compared to when they synchronized the distractor action with the distractor movie. Although we still observed a significant bias in the latter condition, this finding indicates a degree of specificity in AI effects for the identity of the synchronized action. Overall, our data show that MI can substantially modulate the effects of AO on subsequent execution, wherein: (1) combined AO + MI can enhance AI effects relative to passive AO; (2) observed and imagined actions can be flexibly coordinated across different action types and planes; and (3) conflicting AO + MI can abolish AI effects. Therefore, combined AO + MI instructions should be considered in motor training and rehabilitation.

Automatic Imitation in Rhythmical Actions: Kinematic Fidelity and the Effects of Compatibility, Delay, and Visual Monitoring

We demonstrate that observation of everyday rhythmical actions biases subsequent motor execution of the same and of different actions, using a paradigm where the observed actions were irrelevant for action execution. The cycle time of the distractor actions was subtly manipulated across trials, and the cycle time of motor responses served as the main dependent measure. Although distractor frequencies reliably biased response cycle times, this imitation bias was only a small fraction of the modulations in distractor speed, as well as of the modulations produced when participants intentionally imitated the observed rhythms. Importantly, this bias was not only present for compatible actions, but was also found, though numerically reduced, when distractor and executed actions were different (e.g., tooth brushing vs. window wiping), or when the dominant plane of movement was different (horizontal vs. vertical). In addition, these effects were equally pronounced for execution at 0, 4, and 8 s after action observation, a finding that contrasts with the more short-lived effects reported in earlier studies. The imitation bias was also unaffected when vision of the hand was occluded during execution, indicating that this effect most likely resulted from visuomotor interactions during distractor observation, rather than from visual monitoring and guidance during execution. Finally, when the distractor was incompatible in both dimensions (action type and plane) the imitation bias was not reduced further, in an additive way, relative to the single-incompatible conditions. This points to a mechanism whereby the observed action’s impact on motor processing is generally reduced whenever this is not useful for motor planning. We interpret these findings in the framework of biased competition, where intended and distractor actions can be represented as competing and quasi-encapsulated sensorimotor streams.

Energetic Costs of Incidental Visual Coupling during Treadmill Running

PURPOSE To determine the role of visual-spatial information in stabilizing movement during treadmill locomotion. METHODS Physiological, biomechanical, and psychological indices of coordination stability were recorded while participants were visually coupled with a whole-body image of themselves during treadmill locomotion. Ten participants ran on a treadmill under three visual conditions: two dynamic images (symmetrical, mirror image; asymmetrical, reversed mirror image) and one static. Performance was examined at two speeds. RESULTS Participants ran more economically (mL x kg x min(-1)) when they were visually coupled with a symmetrical rather than with an asymmetrical or static image. An asymmetrical coupling resulted in increased variability in footfall position at the faster speed, in comparison to the symmetrical and static conditions. However, at slower speeds, footfall variability and frequency were higher under both dynamic visual conditions in comparison to the static control. Changes in metabolic economy (mL x kg x min(-1)) were only partially mediated by movement kinematics. CONCLUSION Visual information influences treadmill locomotion and associated measures of stability even when there is no intention to coordinate with external stimuli.

Motor imagery during action observation increases eccentric hamstring force: an acute non-physical intervention

Abstract Purpose: Rehabilitation professionals typically use motor imagery (MI) or action observation (AO) to increase physical strength for injury prevention and recovery. Here we compared hamstring force gains for MI during AO (AO + MI) against two pure MI training groups. Materials and methods: Over a 3-week intervention physically fit adults imagined Nordic hamstring exercises in both legs and synchronized this with a demonstration of the same action (AO + MI), or they purely imagined this action (pure MI), or imagined upper-limb actions (pure MI-control). Eccentric hamstring strength gains were assessed using ANOVAs, and magnitude-based inference (MBI) analyses determined the likelihood of clinical/practical benefits for the interventions. Results: Hamstring strength only increased significantly following AO + MI training. This effect was lateralized to the right leg, potentially reflecting a left-hemispheric dominance in motor simulation. MBIs: The right leg within-group treatment effect size for AO + MI was moderate and likely beneficial (d = 0.36), and only small and possibly beneficial for pure MI (0.23). Relative to pure MI-control, effects were possibly beneficial and moderate for AO + MI (0.72), although small for pure MI (0.39). Conclusions: Since hamstring strength predicts injury prevalence, our findings point to the advantage of combined AO + MI interventions, over and above pure MI, for injury prevention and rehabilitation. Implications for rehabilitation While hamstring strains are the most common injury across the many sports involving sprinting and jumping, Nordic hamstring exercises are among the most effective methods for building eccentric hamstring strength, for injury prevention and rehabilitation. In the acute injury phase it is crucial not to overload damaged soft tissues, and so non-physical rehabilitation techniques are well suited to this phase. Rehabilitation professionals typically use either motor imagery or action observation techniques to safely improve physical strength, but our study shows that motor imagery during observation of Nordic hamstring exercises offers a safe, affordable and more effective way to facilitate eccentric hamstring strength gains, compared with pure motor imagery. Despite using bilateral imagery and observation training conditions in the present study, strength gains were restricted to the right leg, potentially due to a left hemispheric dominance in motor simulation.

Exercising for the Pleasure and for the Pain of It: The Implications of Different Forms of Hedonistic Thinking in Theories of Physical Activity Behavior

This is an open-access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), https://creativecommons.org/licenses/by/4.0/.

The Nature, Measurement, and Development of Imagery Ability:

This introduction to a special issue of Imagination, Cognition and Personality discusses how imagery ability is conceptualized, measured, and developed within sport and exercise sciences. Drawing from the model of imagery ability in sport, exercise, and dance, we explain that imagery ability is best understood not as a single undifferentiated general ability but as a complex multiprocess, multisensory, and multidimensional set of capacities. We argue that a more nuanced way of understanding imagery ability and its subcomponents should guide the development and selection of appropriate measurement tools and training methods. Finally, we introduce the four articles that make up this special issue on imagery ability, which collectively present a range of approaches for progressing this area of research further.

Corticospinal excitability is facilitated by combined action observation and motor imagery of a basketball free throw

Objectives: This experiment investigated the extent to which independent action observation, independent motor imagery and combined action observation and motor imagery of a sport‐related motor skill elicited activity within the motor system. Design and method: Eighteen, right‐handed, male participants engaged in four conditions following a repeated measures design. The experimental conditions involved action observation, motor imagery, or combined action observation and motor imagery of a basketball free throw, whilst the control condition involved observation of a static image of a basketball player holding a basketball. In all conditions, single pulse transcranial magnetic stimulation was delivered to the forearm representation of the left motor cortex. The amplitude of the resulting motor evoked potentials were recorded from the flexor carpi ulnaris and extensor carpi ulnaris muscles of the right forearm and used as a marker of corticospinal excitability. Results: Corticospinal excitability was facilitated significantly by combined action observation and motor imagery of the basketball free throw, in comparison to both the action observation and control conditions. In contrast, the independent use of either action observation or motor imagery did not facilitate corticospinal excitability compared to the control condition. Conclusions: The findings have implications for the design and delivery of action observation and motor imagery interventions in sport. As corticospinal excitability was facilitated by the use of combined action observation and motor imagery, researchers should seek to establish the efficacy of implementing combined action observation and motor imagery interventions for improving motor skill performance and learning in applied sporting settings. HighlightsCombined action observation and motor imagery facilitates corticospinal excitability.Corticospinal excitability was not facilitated by independent observation or imagery.Sport psychologists should combine imagery interventions with action observation.