Linear Models
Linear models were constructed to test the hypothesis that flight
training (H1), dietary fat (H2), and dietary antioxidants (H3)
influenced antioxidant capacity and lipid damage in the plasma at
discrete timepoints (i.e., BG, PF, AF, RC), over the course of the
experiment (calculated as RC-BG), during an acute flight (calculated as
AF-PF), and in the liver and pectoralis at Recovery sampling. We used a
global model without interaction terms that best matched this hypothesis
and included possible explanatory covariates (i.e., cohort, sex, and
wing chord), however, these covariates were not included in the global
linear models.
To test the hypothesis that flight-training, dietary fat, and dietary
antioxidants had an interactive effect on oxidative status, we compared
our global models to models including a 3-way interaction between
dietary fat, antioxidants, and training treatment. These models also
tested the 2-way interactions between covariates. The models with the
3-way interactions were not among the best fit models, thus we report
results for only the main effects.
To determine if energy expenditure during flight influenced antioxidant
capacity or oxidative damage, we included energy consumed (kJ/min)
during the acute flight as a fixed effect in linear models that compared
both plasma oxidative status measured After-flight and the change in
these measures during the acute flight (calculated as AF-PF) among diet
groups across timepoints. The best fit models for AF oxidative status
included energy expenditure, whereas those for change in oxidative
status during the acute flight included energy expenditure x diet
interaction term.