Beta-Alanine for Anaerobic Performance
Beta-alanine reliably gives a small-to-moderate boost to high-intensity efforts lasting roughly one to four minutes, but it does nothing for all-out sprints under 60 seconds and its overall payoff is modest. The grade is "preliminary" because the effect is small and one major regulator has refused to endorse any performance claim.
Why this grade7-layer evidence engine
The evidence base is consistent but unspectacular, which is why this lands at a B (preliminary) rather than a top grade. Three meta-analyses point the same direction: Hobson 2012 (PMID 22270875, n=360) found a significant edge over placebo (median effect size 0.374, ~2.85% improvement), Saunders 2017 (PMID 27797728, n=1461) reported an overall effect size of 0.18 that rose to 0.50 for 0.5-10 minute efforts, and a 2024 review (PMID 39032921, n=331) found 0.39 overall and 0.55 for 4-10 minute maximal work. A double-blind HIIT trial (PMID 31622158, n=18) and a transition-zone review (PMID 32824885) agree.
The catch is that the benefit is narrowly duration-specific. Hobson 2012 found no effect at all for efforts under 60 seconds (p=0.312), so beta-alanine will not help a single heavy lift or a short dash. The mechanism (muscle carnosine buffering acid build-up) explains why it only matters once efforts run long enough to accumulate fatigue. The 2024 data also came only from trained young men, limiting how far it extends to women and older athletes.
Authorities are split, which holds the grade down. Mayo Clinic supports it for high-intensity, repeated-burst activities like a quarter-mile run or interval workout, but the EU's EFSA twice rejected performance health claims, citing insufficient proof of cause and effect, and the US FDA lists it only as a food additive with no approved health claim. That regulator pushback is the counter-evidence behind the B rating.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.712
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高階證據未達主導 (1 positive vs 1 negative)，由 raw_score 決定
- tier_strict_requirement_check — | A→B 因 L4 有 ≥1 against
- detect_disputes — 偵測到 1 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status