Use of Mental Imagery to Limit Strength Loss after Immobilization

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Abstract

Objective:

To assess whether mental imagery of gripping prevents the loss of grip strength associated with forearm immobilization.

Design:

Pretest–posttest randomized-group design.

Setting:

Laboratory.

Participants:

13 female and 5 male university students, age between 17 and 30 years, randomly assigned into 2 groups—1 control and 1 experimental.

Interventions:

Both groups had their nondominant forearms immobilized for 10 days. The experimental group undertook three 5-min mental-imagery sessions daily, during which they imagined they were squeezing a rubber ball.

Main Outcome Measures:

Wrist-flexion and -extension and grip strength before and after immobilization.

Results:

There was no significant change in wrist-flexion or -extension strength in the mental-imagery group. The control group experienced a significant decrease in wrist-flexion and -extension strength during the period of immobilization ( P < .05).

Conclusions:

Despite study limitations, the results suggest that mental imagery might be useful in preventing the strength loss associated with short-term muscle immobilization

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Most cited references 11

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Neural adaptations with chronic physical activity.

Roger Enoka (1997)

Chronic activity patterns, such as strength training, limb immobilization, and aging, produce marked adaptations in both the muscular and nervous systems. In this brief review, some of the involved mechanisms are examined as they are revealed through studies on the maximality, specificity, and pattern of the neural drive to muscle. The studies on maximality indicate that it is difficult to activate maximally a muscle by voluntary command, the capacity varies across muscles, tasks, and training, and the maximum discharge rates of motor neurons decreases with immobilization and increases with strength training. The data on specificity demonstrate that: strength can be increased by training with imagined contractions; the velocity specificity of isokinetic training is evident with intended contractions; the strength training influences the untrained homologous muscle in the contralateral limb; the bilatral deficit can become a bilateral facilitation with appropriate training; and that eccentric contractions appear to involve a different activation scheme compared to isometric and concentric contractions. Finally, the literature on the pattern of the neural drive suggests that: coactivation varies with training and often decreases as skill level increases; measures of motor-unit synchronization reveal changes in neuronal connectivity with physical training; the reflex potentiation varies across muscles, individuals, and activity patterns; the modulation of the H-reflex amplitude with training involves changes in the motor neuron; and the motor neurons exhibit a bistable, excitability property that may be influenced by exercise. Despite the breadth of this evidence, there remain substantial gaps in our knowledge, particularly regarding the symmetry of adaptations with increased and decreased chronic physical activity.

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Motor imagery: perception or action?

John Annett (1995)

Motor imagery has been studied using subjective, behavioural and physiological methods and this paper reviews theoretical and practical issues from all three viewpoints. Attempts to measure motor imagery on a subjective scale have met with limited success but alternative methods are proposed. Research on mental practice suggests a number of different processes may be needed to explain the variety and variability of effects obtained. Recent studies of spatial and motor working memory signify the importance of a primarily visuo-spatial component in which actions are consciously represented together with a more properly motoric component which must be activated to generate either images or overt actions. Finally the question of whether motor imagery is primarily perceptual or motoric in character does not have a simple neurophysiological answer due to the highly distributed nature of motor control. Nevertheless some of the key mechanisms serving both spatial and motoric components have been provisionally identified.

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Dynamic changes in corticospinal excitability during motor imagery.

Ryota Hashimoto, Nancy J Rothwell (1999)

We investigated temporal changes in the amplitudes of motor-evoked potentials (MEPs) induced by transcranial magnetic stimulation over the left motor cortex during motor imagery. Nine subjects were instructed to imagine repetitive wrist flexion and extension movements at 1 Hz, in which the flexion timing was cued by a tone signal. Electromyographs (EMGs) were recorded from the first dorsal interosseous, flexor carpi radialis and extensor carpi radialis muscles of the right hand, and magnetic stimulation was delivered at 0, 250, 500 and 750 ms after the auditory cue. On average, the evoked EMG responses were larger in the flexor muscle during the phase of imagined flexion than during extension, whilst the opposite was true for the extensor muscle. There were no consistent changes in the amplitudes of MEPs in the intrinsic hand muscle (first dorsal interosseous). The EMG remained relaxed in all muscles and did not show any significant temporal changes during the test. The H-reflex in the flexor muscle was obtained in four subjects. There was no change in its amplitude during motor imagery. These observations lead us to suggest that motor imagery can have dynamic effects on the excitability of motor cortex similar to those seen during actual motor performance.

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Author and article information

Journal

Title: Journal of Sport Rehabilitation

Publisher: Human Kinetics

ISSN (Print): 1056-6716

ISSN (Electronic): 1543-3072

Publication date Created: August 2003

Publication date (Print): August 2003

Volume: 12

Issue: 3

Pages: 249-258

Article

DOI: 10.1123/jsr.12.3.249

SO-VID: 2e9a9a19-bacc-4711-a03b-0811fa6c4021

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Use of Mental Imagery to Limit Strength Loss after Immobilization

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Abstract

Objective:

Design:

Setting:

Participants:

Interventions:

Main Outcome Measures:

Results:

Conclusions:

Related collections

Music and Mental Imagery

Most cited references 11

Neural adaptations with chronic physical activity.

Motor imagery: perception or action?

Dynamic changes in corticospinal excitability during motor imagery.

Author and article information

Journal

Article

History

Comments

Comment on this article

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Cited by 10

Most referenced authors 76