Research article summary (published 29 Sep 1996):

Muscle activity patterns altered during pedaling at different body orientations.

Full Abstract

Gravity is a contributing force that is believed to influence strongly the control of limb movements since it affects sensory input and also contributes to task mechanics. By altering the relative contribution of gravitational force to the overall forces used to control pedaling at different body orientations, we tested the hypothesis that joint torque and muscle activation patterns would be modified to generate steady-state pedaling at altered body orientations. Eleven healthy subjects pedaled a modified ergometer at different body orientations (from horizontal to vertical), maintaining the same workload (80 J), cadence (60 rpm), and hip and knee kinematics. Pedal reaction forces and crank and pedal kinematics were measured and used to calculate joint torques and angles. EMG was recorded from four muscles (tibialis anterior, triceps surae, rectus femoris, biceps femoris). Measures of muscle activation (joint torque and EMG activity) showed strong dependence on body orientation, indicating that muscle activity is not fixed and is modified in response to altered body orientation. Simulations confirmed that, while joint torque changes were not necessary to pedal at different body orientations, observed changes were necessary to maintain consistent crank angular velocity profiles. Dependence of muscle activity on body orientation may be due to neural integration of sensory information with an internal model that includes characteristics of the endpoint, to produce consistent pedaling trajectories. Thus, both sensory consequences and mechanical aspects of gravitational forces are important determinants of locomotor tasks such as pedaling.

Author information

Author/s: Brown, D A (DA); Kautz, S A (SA); Dairaghi, C A (CA);

Affiliation: VA Palo Alto Health Care System, Rehabilitation Research and Development Center, Palo Alto, CA 94304-1200, USA.

Journal and publication information

Publication Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S.

Journal: Journal of biomechanics (J Biomech), published in UNITED STATES. (Language: eng)

Reference: 1996-Oct; vol 29 (issue 10) : pp 1349-56

Dates: Created 1997/01/23; Completed 1997/01/23; Revised 2006/11/15;

PMID: 8884480, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult Ankle Joint - physiology Bicycling - physiology Biomechanics Electromyography Female Gravitation Hip Joint - physiology

Humans Knee Joint - physiology Male Models, Biological Muscle, Skeletal - physiology Orientation - physiology Posture - physiology Reference Values

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