Meeting Abstract

P2.80  Monday, Jan. 5  A Swimming Muscle with a Novel Function CARR, J.A.*; MARSH, R.L.; Northeastern University; Northeastern University carr.je@gmail.com

During swimming muscles must shorten and produce positive work to generate thrust to balance the drag on the body and it is generally assumed that most major active muscles will contribute to this function. The goal of this study was to use sonomicrometry and electromyography to determine whether the function of the flexor cruris lateralis (FCL) was to produce positive work during swimming in the mallard. We chose to measure the function of the measure the function of the FCL in the mallard for several reasons. Based on blood flow and anatomical studies, the FCL appears to play an important role during swimming. The FCL, is a large muscle with a complex origin and insertion in cursorial locomotors. However, the FCL appears to have been significantly modified in birds that employ swimming as a primary form of locomotion. Based on our results, the FCL of the mallard appears to function in both terrestrial locomotion and during swimming. During terrestrial locomotion, the FCL actively shortens by approximately 10-15% during stance, correlating with a large knee flexion at low speeds and increased hip extension at high speeds. During swimming the FCL is largely isometric during the power stroke and shortens by 3-7 % during the return stroke. We hypothesize that the major role of the FCL during the power stroke in swimming is to counteract the reaction force produced by ankle extension, thus holding the knee and hip in a fixed position, decreasing the amount of drag and increasing the effectiveness of the power produced by the ankle extensors. Supported by NIH AR47337 and NSF IOB-0542795 to RLM.