Blood levels of hypoxanthine (HX) have been suggested as potential biomarkers associated with intramuscular metabolic dynamics in response to exercise. This pilot randomized crossover trial (UMIN000036520) aimed to investigate the changes in plasma HX after whole-body vibration exercise (WBVE) and their relationships with body composition and muscle-related parameters, enrolling eighteen healthy male volunteers. In the WBVE-alone intervention, the study subjects performed 20-min of WBVE. In the OGTT → WBVE intervention, a 75-g oral glucose load (OGL) was administered 30 min prior to the start of the WBVE intervention. Blood samples were collected before the start and 10 min after the end of WBVE in both interventions. WBVE resulted in a significant increase in plasma HX levels, which was accompanied by increased blood ammonia, pyruvic acid, and lactic acid levels. The HX increase following WBVE was suppressed by prior OGL. In the WBVE-alone intervention, there were no significant correlations between the post-WBVE changes in plasma HX (ΔHX) levels and any of the clinical parameters. On the other hand, in the OGTT → WBVE intervention, ΔHX showed significant negative correlations with muscle mass (ρ = -0.62, p = 0.01), strength (ρ = -0.71, p = 0.005), and muscle quality (ρ = -0.81, p = 0.0007) in the legs. In conclusion, these findings suggest possible associations between post-WBVE increases in plasma HX levels and muscle status, particularly under the glucose-supplemented condition. The measurement of plasma HX concentrations following WBVE may have clinical applications in the identification of high-risk populations for sarcopenia.
