营销话术证据 A · 指南级
低强度心率 = 燃脂区
真相
脂肪供能的比例高，不等于烧掉的脂肪总量多；总能量消耗和运动后的额外耗氧（EPOC）在高强度下更大。
机制速览
Zone 2 是一种你能边动边正常说话的中低强度有氧：心跳上来了、有点出汗，但还能完整说完一句话不喘。慢跑、骑车、快走都算，通常一次 30-90 分钟。
来源（3）
- Hawley, J. A., Lundby, C., Cotter, J. D., & Burke, L. M. (2018). Maximizing cellular adaptation to endurance exercise in skeletal muscle. Cell Metabolism, 27(5), 962-976. Narrative review of strategies athletes use to amplify endurance adaptation in skeletal muscle, on the premise that a greater metabolic load and larger perturbations of cellular homeostasis, repeated over months and years, amplify training adaptation. The abstract does not rank training intensities and does not claim that low-intensity (Zone 2) work is the main driver of mitochondrial biogenesis (abstract, PMID 29719234).
- Coyle, E. F. (1995). Substrate utilization during exercise in active people. The American Journal of Clinical Nutrition, 61(4 Suppl), 968S-979S. Classic dataset on the fat/carbohydrate oxidation cross-over with intensity — the empirical basis for the Zone 2 'fat-burning' framing (and the limits of that framing).
- Brooks, G. A. (2018). The science and translation of lactate shuttle theory. Cell Metabolism, 27(4), 757-785. Definitive modern review establishing lactate as fuel rather than waste; the 'lactic acid burn' framing is anatomically and biochemically incorrect.