Serum Metabolic Signatures Induced By a Three-Day Intensified Exercise Period Persist After 14 h of Recovery in Runners

This study investigated changes in
the human serum metabolome elicited
by a 3-day period of intensified training. Runners (N = 15, mean ± SD age, 35.2 ± 8.7 years) ran for 2.5 h/day
on treadmills at ∼70% VO2max for 3 days in a row,
with blood samples collected pre-exercise, and immediately and 14
h post-exercise. Samples were analyzed using gas and liquid chromatography/mass
spectrometry (GC–MS, LC–MS), with compounds identified
based on comparison to more than 2800 purified standards. Repeated
measures ANOVA was used to identify metabolites that differed significantly
across time, with multiple testing corrected by the false discovery
rate (FDR) (q-value). Immediately following the 3-day
exercise period, significant 2-fold or higher increases in 75 metabolites
were measured, with all but 22 of these metabolites related to lipid/carnitine
metabolism, 13 to amino acid/peptide metabolism, 4 to hemoglobin/porphyrin
metabolism, and 3 to Krebs cycle intermediates (q-values < 0.001). After a 14 h overnight recovery period, 50 of
the 75 metabolites remained elevated, with 8 decreased (primarily
amino acid-related metabolites) (q-values < 0.05).
Among the top 20 metabolites, the mean fold changes were 12.4 ±
5.3 and 2.9 ± 1.3 immediately and 14-h post-exercise, respectively.
Significant decreases (40–70%, q < 0.01)
in 22 metabolites (primarily related to lysolipid and bile acid metabolism)
were measured post-exercise, with all but 4 of these still decreased
after 14 h rest recovery (q < 0.025). Runners
experienced a profound systemic shift in blood metabolites related
to energy production especially from the lipid super pathway following
3 days of heavy exertion that was not fully restored to pre-exercise
levels after 14 h recovery.