1. Anticipatory muscular activity during stable and unstable standing
David Conradsson
David Conradsson
20 juni 2018 1 1

2. Postural control Postural stability: the ability to control the
body Centre of Mass (CoM) in relation to the
base of support (BoS).
Postural orientation: maintenances of
a posture of the body that is appropriate for
performance of the specific task.
Sensory input (visual, vestibular, somatosensory).
Motor output
Horak FB, Macpherson, 1996

3. Postural adjustments Anticipatory mechanism (feed-forward)
- Prediction of disturbance of CoM in which preparatory responses is
produced.
- Precede the onset of the movement.
Aims to maintain postural stability – orientation, and to provide a dynamic
support to the chain of movement for improved performance (force,
velocity).
Compensatory/reactive mechanism (feedback):
- Initiated by sensory input that detect postural instability/perturbation.
- Occur after/during the movement.
(Bouisset 2008, Horak FB, Macpherson, 1996)

4. Unstable standing – MBT-shoes
Rounded sole = increased degree of instability
Based on qualitative/clinical experience…

5. Brief review…
Balance
Improvement of certain aspects of standing balance (CoP-parameters) in women (>50 years). (Ramstrand et al 2010)
Gait characteristics
Decreased hip and knee ROM, increased dorsiflexion during initial stand phase (Nigg et al 2006, Romkes et al 2006)
Decreased trunk flexion (New & Pearce 2007)
Disability
Decreased perceived LBP (VAS 23mm) in amateur golfers (Nigg et al 2009)

6. Aim
Study anticipatory muscular activity for ankle and trunk muscles during initial phase of voluntary arm movements in stable and unstable standing.
Proximal to distal compensatory adjustments on short base of support.
(Horak & Nashner 1986)

7. Method Subject: Wim! Healthy, athletic… Test procedure:
- Rapid bilateral arm flexion holding a weight in each
hand (2kg)
- Regular shoes (STABLE) vs unstable shoes (UNSTABLE)
- 3 trials for each condition
- Narrow stance width (0.2m)
- Instructions and test trials before measurement

8. Laboratory measurement
Kinematics: right wrist
Muscular activity, EMG:
Rectus
abdominus
Erector spinae
Gastrocnemius
lateralis
Tibialis
anterior

9. Data management and analysis
Onset for the arm movement
- kinematic marker on the wrist.
EMG records 150ms before and 200ms
after the onset of the arm movement were
analyzed.
Definition of muscular onset
Visual inspection.
EMG activity >3SD above mean baseline activity, EMG-burst >30ms.
Postural adjustments
- Anticipatory/preparatory: -150ms before and +50ms after the arm movement.
- Compensatory/reactive: >50ms after the arm movement.
(Aruin & Latash 1995)

10. Data management

11. Results

12. Discussion, questions…

13. References
Aruin AS, Latash ML. Directional specificity of postural muscles in feed-forward postural reactions during fast voluntary arm
movements. Exp Brain Res.03(2):
Horak FB, Macpherson JM, Shepard J, et al. Postural orientation and equilibrium. Handbook of Physiology: Section 12, Integration of
Motor, Circulatory, Respiratory and Metabolic Control During Exercise. New York: Oxford Univ. Press, 1996:47-9.
New P, Pearce J. The effects of Masai Barefoot Technology* footwear on posture: an experimental designed study. Physiotherapy
Research International. 12(4):
Nigg BM, Davis E, Lindsay D et al. The effectiveness of an unstable sandal on low back pain and golf performance. Clin J Sport Med.
19(6):
Nigg B, Hintzen S, Ferber R. Effect of an unstable shoe construction on lower extremity gait characteristics. Clin Biomech (Bristol,
Avon) (1):82-8.
Ramstrand N, Thuesen AH, Nielsen DB et al. Effects of an unstable shoe construction on balance in women aged over 50 years. Clin
Biomech (Bristol, Avon) Feb 20.
Romkes J, Rudmann C, Brunner R. Changes in gait and EMG when walking with the Masai Barefoot Technique. Clin Biomech
(Bristol, Avon) (1):75-81.