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Fig. 6. Representative work loops from the SUPRA and PECT muscles of a pigeon
(Columba livia) engaged in (A,B) level, (C,D) ascending and (E,F)
descending flight. Arrows indicate direction of contraction; bold lines
indicate EMG activity. The hatched areas feature artificial negative stress
(
m) due to compression of the SUPRA strain gauge by
cross-talk from PECT force that remained even after a correction factor was
applied; these areas were not included in the analysis.