Sprint training effects on trout (Oncorhynchus mykiss) white muscle structure

In mammals, sprint-type exercise protocols induce muscular adaptation different from that caused by endurance training. Although there are many published studies on endurance training in fish, few have examined sprint (anaerobic) training. This study is an examination of whether sprint-training changes white muscle morphology in addition to its previously shown ability to improve trout fast-start acceleration performance. Rainbow trout (Oncorhynchus mykiss) white muscle was sampled following 4, 8, and 12 weeks of sprint training (30 s duration, every 2nd day). White muscle fiber cross-sectional area and perimeter were unchanged by the sprint-training regimen. The volume density of terminal cisternae, T-tubules, mitochondria, and lipid droplets were also not significantly different following training. A formula relating muscle fiber perimeter and area, derived from trout white muscle, appears to describe accurately the perimeter-area relationship for muscle fibers, regardless of species or fiber type.