Dynamic Lactate Detection in Skeletal Muscle Using DQF at 7T: Post-Exercise Clearance and T2 Relaxation Analysis

Motivation: Quantitative data on intramuscular lactate and its dynamics is important for improving models of exercise physiology, which can help improve the understanding of metabolic diseases. Goal(s): Investigate dynamics of lactate clearance and T2 relaxation in muscle after exercise. Approach: Four healthy subjects performed toe-rise exercise until fatigue. Intramuscular lactate was quantified by localized double-quantum-filtered (DQF) MRS, interleaving constant and varying evolution time during post-exercise recovery. Results: Lactate clearance rate was 175 ± 39 s⁻¹, T2 = 145 ± 21 ms (mean ± SD). Muscle fiber orientation-dependent apparent J ranged from 15.8 - 17.1 Hz. Impact: Accurate in vivo data on intramuscular lactate T2 and clearance are essential for quantitative understanding of human muscle metabolism. Disentangling the roles of muscle lactate in exercise is relevant for understanding exercise physiology and various metabolic diseases.