Elevated plasma lactate levels via exogenous lactate infusion do not alter resistance exercise-induced signaling or protein synthesis in human skeletal muscle.

• Lactate has been implicated as a potential signaling molecule. In myotubes, lactate incubation increases mTORC1- and ERK-signaling and induces hypertrophy, indicating that lactate could be a mediator of muscle adaptations to resistance exercise. However, the potential signaling properties of lactate, at rest or with exercise, have not been explored in human tissue. In a cross-over design study, 8 men and 8 women performed one-legged resistance exercise while receiving venous infusion of saline or sodium lactate. Blood was sampled repeatedly, and muscle biopsies were collected at rest and at 0, 90,180 min and 24 h after exercise. The primary outcomes examined were intracellular signaling, fractional protein synthesis rate (FSR), and blood/muscle levels of lactate and pH. Post-exercise blood lactate concentrations were 130% higher in the Lactate trial (3.0 vs 7.0 mmol×l-1, p<0.001) whereas muscle levels were only marginally higher (27 vs 32 mmol×kg-1 d.w., p=0.003) compared to the Saline-trial. Post-exercise blood pH was higher in the Lactate-trial (7.34 vs 7.44, p<0.001), with no differences in intramuscular pH. Exercise increased the phosphorylation of mTORS2448 (~40%), S6K1T389 (~3-fold), and p44T202/T204 (~80%) during recovery, without any differences between trials. FSR over the 24-h recovery period did not differ between the Saline (0.067 %/h) and Lactate (0.062 %/h) trials. This study does not support the hypothesis that blood lactate levels can modulate anabolic signaling in contracted human muscle. Further in vivo research investigating the impact of exercised versus rested muscle and the role of intramuscular lactate is needed to elucidate its potential signaling properties.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Hälsovetenskap -- Idrottsvetenskap (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Health Sciences -- Sport and Fitness Sciences (hsv//eng)

Keyword

Deuterium oxid

Metabolites

Sodium lactate

mTORC1

p44/ERK

Medicin/Teknik

Medicine/Technology

Publication and Content Type

ref (subject category)

art (subject category)