Measuring maximum oxygen uptake with an incremental swimming test and by chasing rainbow trout to exhaustion inside a respirometry chamber yields the same results
Yangfan Zhang, Matthew J. H. Gilbert, Anthony P. Farrell
Abstract
Abstract This study hypothesized that oxygen uptake ( Ṁ O 2 ) measured with a novel protocol of chasing rainbow trout Oncorhynchus mykiss to exhaustion inside a static respirometer while simultaneously monitoring Ṁ O 2 ( Ṁ O 2chase ) would generate the same and repeatable peak value as when peak active Ṁ O 2 ( Ṁ O 2active ) is measured in a critical swimming speed protocol. To reliably determine peak Ṁ O 2chase , and compare to the peak during recovery of Ṁ O 2 after a conventional chase protocol outside the respirometer ( Ṁ O 2rec ), this study applied an iterative algorithm and a minimum sampling window duration ( i.e. , 1 min based on an analysis of the variance in background and exercise Ṁ O 2 ) to account for Ṁ O 2 dynamics. In support of this hypothesis, peak Ṁ O 2active (707 ± 33 mg O 2 h −1 kg −1 ) and peak Ṁ O 2chase (663 ± 43 mg O 2 h −1 kg −1 ) were similar ( P = 0.49) and repeatable (Pearson's and Spearman's correlation test; r ≥ 0.77; P < 0.05) when measured in the same fish. Therefore, estimates of Ṁ O 2max can be independent of whether a fish is exhaustively chased inside a respirometer or swum to fatigue in a swim tunnel, provided Ṁ O 2 is analysed with an iterative algorithm and a minimum but reliable sampling window. The importance of using this analytical approach was illustrated by peak Ṁ O 2chase being 23% higher ( P < 0.05) when compared with a conventional sequential interval regression analysis, whereas using the conventional chase protocol (1‐min window) outside the respirometer increased this difference to 31% ( P < 0.01). Moreover, because peak Ṁ O 2chase was 18% higher ( P < 0.05) than peak Ṁ O 2rec , chasing a fish inside a static respirometer may be a better protocol for obtaining maximum Ṁ O 2 .