This study investigated the effects of passive warming on the biomechanical properties of the musculotendinous unit. Paired tibialis anterior (TA) and extensor digitorum longus (EDL) muscles in the rabbit hindlimb were passively heated to different temperatures and then subjected to controlled strain injury. The parameters examined were: 1) percent increase in length to failure, 2) force to failure, 3) energy absorbed by the musculotendinous unit to failure, and 4) site of failure. Warmed (39°C & p l u s m n ; 0.5°C) TA (P ≤ 0.01) and EDL (P ≤ 0.05) muscles achieved a greater increase in length from rest before failing than did their contralateral controls at 35°C ± 0.5°C. In both the TA and EDL the force at failure was greater at 35°C than at 39°C, although the difference was significant for only the EDL (P ≤ 0.05). The energy absorbed (area beneath the length-tension curve) by both the TA and EDL was greater at 39°C, but these differences were not significant. All muscles failed at the distal musculotendinous 'Presented at the 15th annual meetmg of the AOSSM,

The axial muscular system of Pontoporia blainvillei is described and compared with published reports of this system in other cetaceans. A comprehensive system for classification of axial muscles is presented, based on the studies of Slijper. A discrete obliquus capitis inferior is described for the first time in cetacea, and it is suggested that its absence in previous descriptions may have been due partly to dissection error. The major axial muscle-masses are organized in a similar way in most cetaceans, comprising a set of tail elevators and depressors, and a set of tendons with similar actions on the flukes. The anatomy of the axial musculature does not support the idea that the upstroke is the main propulsive stroke in cetaceans, but suggests similar roles of the upstroke and downstroke in propulsion.

No abstract

The purpose of this paper is to describe in detail the shoulder myology of the La Plata River Dolphin, Pontoporia blainvillei, and to review the literature on cetacean shoulder myology. Three fetal and one adult animal were used for the collection of morphological information. Pontoporia is less specialized in its shoulder anatomy that most delphinid cetaceans, and shares several characteristics with some mysticetes. The omohyoid and anterior serratus anterior muscles are found in both Pontoporia and the mysticete Balaenoptera, but are absent in most delphinids. The pectoralis abdominalis and three rhomboideus divisions are found in Pontoporia and Kogia, but in only a few delphinid species described in the literature. It is suggested that these characteristics are associated with a generalized use of the forelimb in Pontoporia.