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# Ground Reaction Forces and Lower Extremity Kinematics When Running With Suppressed Arm Swing

[+] Author and Article Information
Ross H. Miller1

Department of Kinesiology, University of Massachusetts, 30 Eastman Lane, Amherst, MA 01003rhmiller@kin.umass.edu

Graham E. Caldwell, Richard E. A. Van Emmerik, Brian R. Umberger, Joseph Hamill

Department of Kinesiology, University of Massachusetts, 30 Eastman Lane, Amherst, MA 01003

1

Corresponding author.

J Biomech Eng 131(12), 124502 (Nov 04, 2009) (5 pages) doi:10.1115/1.4000088 History: Received January 14, 2009; Revised June 10, 2009; Posted September 01, 2009; Published November 04, 2009; Online November 04, 2009

## Abstract

The role of arm swing in running has been minimally described, and the contributions of arm motion to lower extremity joint kinematics and external force generation are unknown. These contributions may have implications in the design of musculoskeletal models for computer simulations of running, since previous models have usually not included articulating arm segments. 3D stance phase lower extremity joint angles and ground reaction forces (GRFs) were determined for seven subjects running normally, and running under two conditions of arm restraint. When arm swing was suppressed, the peak vertical GRF decreased by 10–13% bodyweight, and the peak lateral GRF increased by 4–6% bodyweight. Changes in peak joint angles on the order of 1–5 deg were observed for hip flexion, hip adduction, knee flexion, knee adduction, and ankle abduction. The effect sizes (ES) were small to moderate $(ES<0.8)$ for most of the peak GRF differences, but large $(ES>0.8)$ for most of the peak joint angle differences. These changes suggest that suppression of arm swing induces subtle but statistically significant changes in the kinetic and kinematic patterns of running. However, the salient features of the GRFs and the joint angles were present in all conditions, and arm swing did not introduce any major changes in the timing of these data, as indicated by cross correlations. The decision to include arm swing in a computer model will likely need to be made on a case-by-case basis, depending on the design of the study and the accuracy needed to answer the research question.

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## Figures

Figure 1

Magnitude of GRF relative to bodyweight (BW, 756 N) during two-legged upright stance while standing quietly (dashed line), swinging the arms in a “walking” style (elbows straight, 1 Hz swing; thick line), and swinging the arms in a “running” style (elbows bent, 2 Hz swing; thin line)

Figure 2

Photograph of a subject demonstrating the restrained arm conditions: (a) arms restrained across the chest (condition RC), and (b) arms restrained behind the back (condition RB)

Figure 3

(a) Vertical, (b) anterior-posterior, and (c) medial-lateral GRF components, and (d) the vertical free moment during normal running (shaded), running with the arms held across the chest (RC, solid line), and running with the arms held behind the back (RB, dashed line). Shaded areas are ±2 within-subject standard deviations for condition N.

Figure 4

(ac) Hip, (df) knee, and (gi) ankle joint angles during normal running (shaded), running with the arms held across the chest (RC, solid line), and running with the arms held behind the back (RB, dashed line). Shaded areas are ±2 within-subject standard deviations for condition N. FL/EX=flexion/extension; AD/AB=adduction/abduction; IR/ER=internal/external rotation; DF/PF=dorsiflexion/plantarflexion; IN/EV=inversion/eversion.

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