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Biomedical subjects

J Altringham

Publications and source records attributed to J Altringham.

3 recordsLinked to original sources
PubMed1995

The effect of tendon compliance on in vitro/in vivo estimations of sarcomere length

The errors likely to result from using excised rigor muscles to determine in vivo sarcomere length ranges were calculated for mouse extensor digitorum longus muscle (EDL). This muscle was chosen because its very long tendon makes it particularly susceptible to errors arising from tendon compliance. By placing dissected limbs into different locomotory stances, and allowing them to go into rigor, the range of sarcomere lengths over which muscles operate in vivo can be determined, but it is subject to errors due to tendon compliance. A tendon compliance of 0.24 GPa and a muscle rigor stress of 35 kPa were determined, and these were used to correct the estimates of in vivo sarcomere length, under worst case conditions. The error introduced was very small: a reduction in sarcomere length of less than 0.5 %.

Journal Article↗
PubMed1995

Tuning in to fish swimming waves: body form, swimming mode and muscle function

Most fish species swim with lateral body undulations running from head to tail. These waves run more slowly than the waves of muscle activation causing them, reflecting the effect of the interaction between the fish's body and the reactive forces from the water. The coupling between both waves depends on the lateral body shape and on the mechanical properties of the tail. During steady swimming, the length of each myotomal muscle fibre varies cyclically. The phase relationship between the strain (muscle length change) cycle and the active period (when force is generated) determines the work output of the muscle. The muscle power is converted to thrust either directly by the bending body or almost exclusively by the tail, depending upon the body shape of the species and the swimming kinematics. We have compared the kinematics and muscle activity patterns from seven species of fish with different body forms and swimming modes and propose a model which yields a consistent pattern, with at least three extremes. Subtle tuning of the phase relationship between muscle strain and activation cycles can lead to major changes in the way muscles function in different swimming modes.

Journal Article↗