Fig. 3. Net work per cycle as a function of cycle frequency (tail-beat frequency) from internal red muscle of skipjack tuna at anterior (ANT) and posterior (POST) locations. Filled symbols and solid lines show results using optimized stimulus conditions that maximize work (optimized) and are expressed as a percentage of the largest value recorded over the range of frequencies studied. Open symbols and broken lines are work done when the muscle was stimulated using conditions measured from swimming fish (in vivo) and are expressed as a percentage of the maximum (optimized) value at each of the frequencies indicated; they therefore show the performance of the muscle under in vivo conditions relative to the maximum (optimized) of which the muscle is capable at each frequency. The limited range of frequencies covered using in vivo conditions reflects the range over which fish actually swim using only red muscle. The strain for ANT muscle was ±5.5 % and that for POST muscle was ±8 %, reflecting strains used in vivo. Values are means ± S.E.M., N=3–6.
