Trade-offs between speed and endurance in the frog Xenopus laevis
:
a multi-level approach
Robbie S. Wilson1,*,
Rob S. James2 and
Raoul Van Damme1
1 Laboratory of Functional Morphology, Department of Biology, University of
Antwerp, Universiteitsplein 1, Wilrijk B-2610, Belgium
2 School of Science and the Environment, Coventry University, D Block,
Priory Street, Coventry CV1 5FB, UK
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Fig. 1. Relationship between body mass (M) and (A) maximum burst swimming
velocity (Umax)
(logUmax=1.78+0.20logM, N=55;
r=0.30; P<0.05) and (B) the time taken to reach
exhaustion whilst swimming at a constant velocity (endurance,
Emax) (logEmax=2.57+1.4logM,
N=55; r=0.46; P<0.01) for 55 juvenile
Xenopus laevis.
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Fig. 2. Relationship between mass residuals of maximum burst swimming velocity
(Umax) and the time taken to reach exhaustion whilst
swimming at a constant velocity (endurance) for 55 juvenile Xenopus
laevis.
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Fig. 3. Changes in (A) force, (B) work-loop shape and (C) net power output per
cycle for a representative Xenopus laevis peroneus muscle during a
continuous set of cycles at 2 Hz using the work-loop technique.
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Fig. 4. Correlations between measures of maximum power output at 6 Hz and
fatigue-resistance of the peroneus muscle at 2 Hz for 18 juvenile Xenopus
laevis. There was a significant negative correlation between maximum
instantaneous power output and fatigue-resistance of force (% of maximum force
at cycle 30) (A). `Cycles to 5% of maximum power' is the number of cycles
taken to reduce net power to 5% of the initial value at cycle 1. NS,
non-significant Pearson's product moment correlation.
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© The Company of Biologists Ltd 2002
