Daily Myofibrillar Protein Synthesis Rates Do Not Differ During Interval Compared to Continuous Exercise Training Matched for Duration and Work in Healthy Young Men.
Level 2 - randomized trial
Randomized within-participant controlled trial
PubMed 41265429 · doi:10.1123/ijsnem.2025-0074
What was done
Ten healthy young men (age 20 ± 1 years) completed a two-week exercise intervention using a single-leg within-participant randomized design. One leg was assigned to high-intensity interval training (HIIT) and the other to work- and duration-matched moderate-intensity continuous training (MICT) for 6 to 8 sessions. Deuterated water was ingested to assess cumulative daily myofibrillar protein synthesis rates. Muscle biopsies were collected at rest from one leg before and after a 2-week habituation period, and from both legs after the 2-week training period.
What was found
Both HIIT and MICT increased single-leg maximal power output (main effect, p < .01) with no significant difference between legs (interaction p = .61). Daily myofibrillar protein synthesis rates did not differ significantly between the habituation period (1.39 ± 0.16% per day), MICT (1.24 ± 0.30% per day), or HIIT (1.42 ± 0.31% per day; p = .29).
Why it matters
When matched for total work and duration, short-term interval training does not stimulate higher cumulative daily myofibrillar protein synthesis rates than continuous training in healthy young men.
Limits
The sample size was very small (n = 10) and limited entirely to young, recreationally active men. The intervention was short (two weeks), and single-leg training may not reflect systemic responses to whole-body exercise.
Cited by
- supports In fit and healthy individuals, intensive sprint interval training does not produce substantial changes in muscle protein synthesis or muscle fiber size.