Intermittent Locomotor Activity That Increases Endurance Also Increases Metabolic Costs in the Desert Iguana (Dipsosaurus dorsalis)

Intermittent activity, alternating bouts of activity and rest, can extend endurance relative to continuous locomotion. Utilizing a rapid fatiguing activity intensity (1.08 m s−1),Dipsosaurus dorsalis( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $n=14$ \end{document} ) ran repeated bouts of varying durations (5, 15, or 30 s) interspersed with variable pause periods (100%, 200%, 400%, or 800% of the activity period) until exhausted. Total distance ran increased relative to continuous locomotion. The largest increases were seen when activity periods were limited to 5 s and pause periods were extended from 5 s to 20 s to 40 s (55, 118, and 193 m, respectively). To analyze these increases further, O2consumption was measured for six bouts of 5‐s activity separated by either 5, 20, or 40 s ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $n=8$ \end{document} ). The sum of elevated O2consumption during activity, pauses, and recovery increased significantly from 0.08 to 0.09 and 0.12 mL O2g−1as pause duration increased, primarily due to greater O2consumption during longer pause intervals. Postexercise recovery metabolism was a large cost (>57% of total) but did not differ among treatments. Overall, 40‐s pauses were most expensive (absolutely and per unit distance) but provided the greatest endurance, likely due to further repletion of metabolites or removal of end products during the longer pause. In contrast, the shortest pause period was most economical but exhausted the animal most rapidly. Thus, a pattern