Introduction: Sporting events lasting 1 to 4 minutes require intensities that exceed the limits of the aerobic capacity; fatigue is partly due to metabolite accumulation caused by substrate-level phosphorylation and insufficient aerobic energy supply. Thus, improving the response time and maximal rate of aerobic energy production and increasing the ability to counteract metabolite accumulation are two physiological mechanisms by which supramaximal exercise performance of this type may be improved. Our aim was to manipulate these mechanisms in a two-part intervention, in ways that might improve supramaximal performance. We hypothesized that 1) β-alanine supplementation would increase intramuscular carnosine and buffering capacity and dampen pH disturbance during supramaximal cycling exercise, 2) that high-intensity interval training (HIT) would enhance aerobic energy contribution during supramaximal cycling exercise, and 3) that HIT would have greater benefits on supramaximal performance mechanisms when performed directly after β-alanine supplementation.
Methods: Sixteen active men performed an incremental cycling test for aerobic capacity and peak power output (PPO) and a 90-second supramaximal (110 % PPO) cycling test at three time points: before and after oral supplementation with 3.2 g/d β-alanine (n=7) or placebo (n=9), and after an 11-d HIT block (9 sessions, 4 × 4 min maximal cycling), which followed supplementation directly. Aerobic energy contribution was estimated from the ratio of O2 consumption to the O2 deficit, while biopsies from m. vastus lateralis were taken before and immediately after the 90-s cycling test to address metabolic mechanisms. Carnosine in 4 leg muscles was assessed via MR-spectroscopy. Subjects also completed stress-recovery questionnaires weekly and logged all training throughout the study.
Results:Supplementation with β-alanine, but not placebo, increased leg muscle carnosine (mean of 4 muscles: 2.2 ± 0.7 mmol/kg w.w., 32 ± 13%), improved stress-recovery balance and other psychological parameters, especially during the HIT block. Buffering capacity and incremental cycling parameters were unaffected, but during 90 s cycling at 110% PPO, β-alanine increased aerobic energy contribution slightly (1.4 ± 1.3 %, d=0.53), concurrent with moderately reduced oxygen deficit (-5 ± 5 %, d=0.63) and muscle lactate accumulation (-13.9 ± 16.4 mmol/kg d.w., -23 ± 30 %, d=0.87), but had no effect on pH disturbance. The HIT block improved buffering capacity (8 ± 11 %, d=0.57) and glycogen storage moderately (30 ± 47%, d=0.56), but did not affect VO2max or aerobic energy contribution during supramaximal cycling exercise. There was no difference in the effects of HIT between β-alanine and placebo groups. Conclusions: Contrary to our hypothesis, β-alanine did not affect buffering capacity but had minor positive effects on supramaximal exercise metabolism and psychological parameters, whereas HIT increased buffering capacity and glycogen storage, but had no effect on aerobic energy provision. In conclusion, β-alanine may benefit psychological state, especially during intense training phases, as well as energy balance, while HIT blocks are probably most useful in sports involving repeated sprints, where glycogen depletion and acidosis limit performance.
