Daily Myofibrillar Protein Synthesis Rates Do Not Differ During Interval Compared to Continuous Exercise Training Matched for Duration and Work in Healthy Young Men.

Plain-language summary

This study compared two cardio styles for building muscle when matched for total work and time: HIIT (high-intensity interval training, short bursts of hard effort with rests between) and MICT (moderate-intensity continuous training, steady moderate cardio held for a stretch). In an unusual single-leg design, ten young men trained one leg with HIIT and the other with MICT on a cycle machine over two weeks, with muscle biopsies measuring myofibrillar protein synthesis (the rate at which muscle fibers rebuild). Both legs gained power equally, and neither style rebuilt muscle faster than the other over this short window.

Key findings

• HIIT and MICT increased single-leg maximal power output similarly.
• No difference in daily myofibrillar protein synthesis rates between HIIT and MICT.
• Protein synthesis rates did not change significantly from the habituation period through training.