November 20, 2020

Jeremy Cohen, MSc Student, and Chris Pignanelli, PhD Student

Human Performance and Health Research Lab, Department of Human Health and Nutritional Science University of Guelph, Guelph, Ontario, Canada

Take home message

• This study explored whether experimentally increasing blood lactate increased muscle protein synthesis, an important process that contributes to an increase in muscle mass.
• Short-term elevation of lactate levels in the blood and muscle during resistance exercise did not increase skeletal muscle protein synthesis in young men and women.
• This study suggests that increasing lactate levels in the blood higher than what naturally occurs during resistance exercise will not promote greater accretion of muscle mass with training.

Background 

• At the fundamental level, gaining muscle mass depends upon a net positive protein turnover over time – such that muscle protein synthesis is greater than muscle protein breakdown.
• Resistance exercise is effective for increasing muscle protein synthesis and, when paired with sufficient nutrient intake, results in a net positive protein turnover.
• How muscle protein synthesis is increased following resistance exercise is not fully understood. Cell culture and animal models suggest lactate, a product of anaerobic metabolism during exercise, may play an important role, but this has not been directly studied in humans.

How the study was done

• Sixteen young adults (8 male, 8 female) were recruited for a randomized, cross-over study with two conditions separated by one week. In one condition lactate was administered intravenously before and during resistance exercise; in the other participants performed resistance exercise with a placebo infusion containing no lactate.
• Participants performed 6 sets of knee extension exercise to muscular fatigue, using 75% of their 1-repetition maximum with the muscular work matched between trials.
• Blood samples and muscle biopsies were collected before, during and after exercise for up to 24-hours to measure blood lactate levels, muscle protein synthesis and associated signaling pathways related to protein turnover.

What the researchers found

• In both trials, blood and muscle lactate increased following resistance exercise.
• Compared to the placebo trial, lactate infusion increased blood and muscle lactate concentrations by 130% and 20%, respectively; however, muscle acidification (pH) was not different between trials.
• Despite a higher lactate concentration in the blood and muscle during exercise, muscle protein synthesis and signaling pathways associated with protein turnover were not different between trials up to 24-hours following exercise.

Conclusion

Acutely increasing blood lactate levels during resistance exercise does not seem to play an obligatory role in altering the 24-hour muscle protein synthesis response.

Liegnell R, Apro W, Danielsson S, Ekblom B, van Hall G, Holmberg HC, Moberg M. Elevated plasma lactate levels via exogenous lactate infusion do not alter resistance exercise-induced signaling or protein synthesis in human skeletal muscle. Am J Physiol – Endocrinol Metab : 8–10, 2020. doi: 10.30906/1999-5636-2020-7-8-10.

If you cite any information from this, please consult the original article and cite that source. This summary was written for the Canadian Society for Exercise Physiology and it has been reviewed by the CSEP Knowledge Translation Committee.