Exercise intensity-dependent lactate elevation in skin interstitial fluid and its long-lasting effect

Regular exercise promotes various anti-ageing adaptations in skin tissue. Although the underlying mechanisms of that might associate to the acute exercise-induced lactate signaling in the skin, it remains uncertain the profile of skin interstitial fluid (ISF) lactate dynamics during and following acute exercise. Here, we investigated whether the skin ISF lactate level increases in association with blood lactate during acute incremental exercise using a single microneedle perfusion system. The rats were acclimated to treadmill running exercise and underwent external jugular vein cannulation. Following comprehensive recovery, a 1 mm single microneedle was implanted into the back skin. Skin ISF lactate progressively increased in tandem with blood lactate during the incremental exercise but did not decrease to baseline levels until 30 minutes following the exercise unlike blood. Moreover, lactate threshold (LT), is a crucial marker of athletic aerobic performance during acute exercise, extrapolated from skin ISF showed significant alignment with blood LT. Our findings reveal that the skin ISF lactate increases associated with blood lactate and the long-lasting elevation state following acute exercise. Moreover, lactate dynamics in skin ISF can predict LT. These findings would be a milestone for elucidating regular exercise-induced physiological adaptations in the skin and evaluating athletic performance. Graphical Abstract Lactate levels in rat skin interstitial fluid (ISF) increased in association with blood lactate during acute incremental exercise, but the increase in skin ISF lactate lasted 30 min following acute exercise. Lactate threshold (LT), a crucial marker of aerobic athletic performance, can be predicted from skin fluid dynamics during acute exercise. These findings would be a milestone for elucidating regular exercise-induced physiological adaptations in the skin and evaluating athletic performance.