No Effects Of High-intensity Interval Exercise On Muscle β-alanine Uptake And Carnosine Loading

Carnosine (L-histidyl-β-alanine) is an important buffer in the skeletal muscle. Increased muscle carnosine has been associated with improved exercise performance. Whilst β-alanine supplementation is an effective way to increase muscle carnosine, only ~6% of the ingested β-alanine is used to synthesise carnosine, indicating very low efficiency. Previous studies have suggested that exercise may optimise carnosine synthesis and β-alanine uptake into skeletal muscle, but the evidence is not conclusive yet. PURPOSE: to investigate whether high-intensity interval exercise (HIIE) improves β-alanine uptake into skeletal muscle and carnosine synthesis. METHODS: 13 healthy young males participated in this crossover, counterbalanced study (treatment order were randomised). They received β-alanine supplementation (20 mg·kg-1 body mass once per day) immediately after completing a HIIE session or no exercise, for 5 consecutive days. The washout period between treatments was 6 weeks. Training consisted of 10 set of 1-min cycling bouts at 150% of individual lactate threshold (Dmax method) with 1 min intervals at 50% of the Dmax. Muscle biopsies were collected on the first day, from the m. vastus lateralis, at rest and 150 following the completion of the exercise session. On the last day, another biopsy was collected 150 min following the 5th and last HIIE session. Muscle carnosine and β-alanine were quantified via HPLC-MS/MS. RESULTS:Muscle β-alanine increased ~3-fold 150 minutes following the ingestion of a single dose of β-alanine in both conditions (main effect of time, p < 0.0001), with no group-by-treatment interaction (p = 0.589) (figure 1). Muscle carnosine tended to increase after 5-days of treatment (p = 0.09 vs. rest; p = 0.04 vs. post-exercise, simple effect of time), with no group*time interaction (p = 0.69) (figure 1). CONCLUSIONS: HIIE did not increased β-alanine uptake and carnosine loading alongside β-alanine supplementation.