spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online March 28, 2008
Journal of Experimental Biology 211, 1211-1220 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.013227
This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in JEB
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Nelson, F. E.
Right arrow Articles by Roberts, T. J.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Nelson, F. E.
Right arrow Articles by Roberts, T. J.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati   Add to Twitter  
What's this?

Task-dependent force sharing between muscle synergists during locomotion in turkeys

Frank E. Nelson* and Thomas J. Roberts

Ecology and Evolutionary Biology Department, Brown University, Box GB205, Providence, RI 02912, USA


Figure 1
View larger version (4K):
[in this window]
[in a new window]

  		Fig. 1. Swing duration for unloaded (open circles) running and for running with added limb weights of 30 g (solid gray circles) and 60 g (solid black circles). Values significantly different (P<0.05) from the unloaded value at each speed are indicated with an asterisk. The symbols for swing duration with limb weights of 30 g and 60 g are offset from their measured speed to the right and left, respectively.

 

Figure 2
View larger version (42K):
[in this window]
[in a new window]

  		Fig. 2. Values of peak force, time to peak force and impulse produced by the lateral head of the gastrocnemius (red bars) during swing phase were not different from the values required to generate the extension moment at the ankle joint (gray bars) across speed and weighting conditions. The force and impulse required did not change with added mass (P>0.09) and were not significantly different (P>0.31) than the force produced by the LG. For speeds 1–2 m s–1, Ni=5 for all variables; for 2.5 m s–1, Ni=4 for all variables.

 

Figure 3
View larger version (27K):
[in this window]
[in a new window]

  		Fig. 3. A representative trace of joint moments (A) and forces (B,C) developed by the MG (blue lines) and LG (red lines) for the right limb of a turkey running at 2 m s–1. A positive then negative joint moment is required at the ankle joint during swing as the joint flexes and extends. The black line (B,C) is the force required from the gastrocnemius, calculated from the moment measured by inverse dynamics and the muscle moment arm. Only forces during swing phase were calculated from inverse dymanics (required force). The muscular force required to produce the measured joint extension moment is closely matched by the force produced by the lateral head of the gastrocnemius, while the medial head produces almost no force. The exclusive force production by the LG ends at the beginning of stance (gray shaded region in C).

 

Figure 4
View larger version (49K):
[in this window]
[in a new window]

  		Fig. 4. An equal amount of force is produced in the two heads of the gastrocnemius during stance. Peak force significantly (P<0.05) increases in both the lateral head (red) and the medial head (blue) with speed. With increasing speed, the time of peak force occurs consistently later in the medial head. Other timing variables were unchanged across changes in mass and speed. For speeds 1–2 m s–1, Ni=5 for LG and Ni=4 for MG variables. For 2.5 m s–1, Ni=4 for LG variables and Ni=3 for MG variables.

 

Figure 5
View larger version (17K):
[in this window]
[in a new window]

  		Fig. 5. Reduced major axis regressions of MG peak force against LG peak forces shows that for all speed and loading conditions, forces in the LG and MG are similar during stance phase (A), but not during swing phase (B). Black triangles, bird 1; red triangles, bird 2; green triangles, bird 3. The slopes of both regression lines through the pooled data of all three birds were significant (P<0.05). Solid lines, slopes for measured data; broken line, hypothetical slope=1.0.

 

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati   Add to Twitter Twitter    What's this?



© The Company of Biologists Ltd 2008