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Deceleration affects anticipatory and reactive components of triggered postural responses
Mark G Carpenter1, Alf Thorstensson, Andrew G Cresswell
1Department of Neuroscience, Karolinska Institutet, Box 5626, 114 86, Stockholm, Sweden.
Experimental Brain Research
|July 26, 2005
Summary
Balance control is affected by how quickly surfaces move. Short, rapid surface translations trigger immediate reactions, while predictable ones allow for anticipatory adjustments in posture and muscle activity.
Area of Science:
- Biomechanics
- Human Physiology
- Motor Control
Background:
- Assessing balance control is challenging due to confounding effects of perturbation methods.
- Understanding how different perturbation profiles influence postural responses is crucial for accurate balance assessment.
Purpose of the Study:
- To investigate the impact of acceleration-deceleration intervals in horizontal surface translations on postural responses.
- To differentiate between reactive and anticipatory mechanisms in balance control under varying perturbation conditions.
Main Methods:
- Twelve adult males participated in a study involving unexpected forward and backward surface translations.
- Two distinct acceleration-deceleration intervals (SHORT and LONG) were used, with serial and random presentation orders.
- Measurements included surface electromyography (EMG), motion analysis, and force plate data to record postural and muscle activity.
Main Results:
- Longer perturbations (LONG) resulted in greater trunk displacement and later muscle activation (500-800 ms) compared to shorter ones (SHORT), especially in random presentation.
- During SHORT perturbations, antagonist muscle activity correlated with deceleration, not initial acceleration.
- Predictable SHORT perturbations enabled anticipatory mechanisms, reducing early EMG, ankle torque, and trunk displacement, unlike predictable LONG perturbations.
Conclusions:
- The acceleration-deceleration interval significantly influences triggered postural responses, affecting both reactive and anticipatory mechanisms.
- Short acceleration-deceleration intervals can elicit reactive responses and, with predictability, facilitate anticipatory postural adjustments.
- This highlights the importance of perturbation characteristics in studying human balance control.