Acute metabolite responses to swimming exercise of different intensities in highly trained male and female swimmers

Abstract

We investigated metabolite responses to different swimming intensities in 16 highly trained swimmers (9 males, 7 females, aged 16-24 years). After determining critical swimming speed (CS) with a 12 × 25 m maximal effort test, participants completed three swimming trials at moderate (below CS), heavy (at CS), and severe (above CS) intensities on separate days. Capillary blood samples (1 mL) were collected before and after each trial for metabolite profiling via mass spectrometry. Orthogonal partial least squares analysis (OPLS-DA) revealed distinct metabolite changes between moderate and severe intensity trials [R²X (cum): 0.56; R²Y(cum): 0.95, pR²Y: 0.02, pQ²: 0.02]. Free fatty acids (FFAs) 18:0, 20:0, 20:4, and 22:4 showed higher log₂ fold changes (log₂FC) after moderate compared to heavy and severe trials (all p < 0.01). Plasma lactate, pyruvate, alanine, and HDL-4 cholesterol concentrations had greater log₂FC after heavy and severe trials than moderate (all p < 0.01). Males tended to show lower log₂FC in FFA than females in the severe trial, though this was not significant. These findings demonstrate that swimming intensity influences metabolite profiles, with reduced lipid metabolism and increased TCA cycle activity as intensity rises. A 1 mL capillary blood sample can effectively capture these metabolic shifts.

Keywords: biochemistry; energetics; metabolomics; phenotype.

FIGURE 1

Study design schematic. Participants performed a 12 × 25 m critical speed test approximately 1 week before the test week. During the testing week, participants performed three standardized swimming trials in the moderate, heavy, and severe exercise intensity domains, which were scheduled 1 day apart. To profile participants' metabolic and epigenetic responses to exercise, a capillary blood sample (1.0 mL whole blood) was collected from a fingertip after 5 min of hand warming before and immediately after each standardized swimming trial.

FIGURE 2

Eruption plot displaying Cliff's delta for key metabolites discriminating the pre‐ and post‐exercise time points within the moderate and severe intensity domain swimming trials.

FIGURE 3

Heavy intensity domain metabolite responses projected over the results of the OPLS‐DA model built for the log₂ fold changes in metabolites between the moderate and severe intensity domain swimming trials. A list of overlapping metabolites between each swimming trial are available in the Appendix S1.

FIGURE 4

Log₂ fold change (post‐exercise/pre‐exercise) for the top four metabolites from the OPLS‐DA model were followed up with a univariate linear mixed model. (a) Presents the top four metabolites that were higher in the moderate compared to the severe intensity domain swimming trial (all p < 0.01), and (b) the top four metabolites that were higher in the severe compared to the moderate swimming domain trial (all p < 0.001).

FIGURE 5

Log₂ fold change in plasma free fatty acid (FFA) concentration 1 h after swimming exercise performed within the moderate, heavy, severe intensity domains or males (blue triangle) and females (orange circle). Responses have been standardized to show deviation from the moderate intensity domain trial. We note that the log₂ fold change in FFAs after exercise in the severe domain is lower in males than females for all FFAs.