Cambridge Centre for Sport and Exercise Sciences, Anglia Ruskin University, East Road, Cambridge, UK.
Kings College, University of Cambridge, Cambridge, UK.
J Int Soc Sports Nutr. 2017 Nov 21;14:44. doi: 10.1186/s12970-017-0201-z. eCollection 2017.
Dietary protein intakes up to 2.9 g.kg.d and protein consumption before and after resistance training may enhance recovery, resulting in hypertrophy and strength gains. However, it remains unclear whether protein quantity or nutrient timing is central to positive adaptations. This study investigated the effect of total dietary protein content, whilst controlling for protein timing, on recovery in resistance trainees.
Fourteen resistance-trained individuals underwent two 10-day isocaloric dietary regimes with a protein content of 1.8 g.kg.d (PRO) or 2.9 g.kg.d (PRO) in a randomised, counterbalanced, crossover design. On days 8-10 (T1-T3), participants undertook resistance exercise under controlled conditions, performing 3 sets of squat, bench press and bent-over rows at 80% 1 repetition maximum until volitional exhaustion. Additionally, participants consumed a 0.4 g.kg whey protein concentrate/isolate mix 30 min before and after exercise sessions to standardise protein timing specific to training. Recovery was assessed via daily repetition performance, muscle soreness, bioelectrical impedance phase angle, plasma creatine kinase (CK) and tumor necrosis factor-α (TNF-α).
No significant differences were reported between conditions for any of the performance repetition count variables ( > 0.05). However, within PRO only, squat performance total repetition count was significantly lower at T3 (19.7 ± 6.8) compared to T1 (23.0 ± 7.5; = 0.006). Pre and post-exercise CK concentrations significantly increased across test days ( ≤ 0.003), although no differences were reported between conditions. No differences for TNF-α or muscle soreness were reported between dietary conditions. Phase angle was significantly greater at T3 for PRO (8.26 ± 0.82°) compared with PRO (8.08 ± 0.80°; = 0.012).
When energy intake and peri-exercise protein intake was controlled for, a short term PRO diet did not improve markers of muscle damage or soreness in comparison to a PRO approach following repeated days of intensive training. Whilst it is therefore likely that moderate protein intakes (1.8 g.kg.d) may be sufficient for resistance-trained individuals, it is noteworthy that both lower body exercise performance and bioelectrical phase angle were maintained with PRO. Longer term interventions are warranted to determine whether PRO intakes are sufficient during prolonged training periods or when extensive exercise (e.g. training twice daily) is undertaken.
饮食蛋白质摄入量高达 2.9g/kg/d，在抗阻训练前后摄入蛋白质可能会促进恢复，从而实现肌肉肥大和力量增长。然而，目前尚不清楚蛋白质的数量还是营养时机对适应有重要影响。本研究旨在调查在控制蛋白质时机的情况下，总饮食蛋白质含量对抗阻训练者恢复的影响。
14 名抗阻训练者接受了两种 10 天等热量饮食方案，蛋白质含量分别为 1.8g/kg/d（PRO）或 2.9g/kg/d（PRO），采用随机、交叉对照设计。在第 8-10 天（T1-T3），参与者在受控条件下进行抗阻运动，以 80%的 1 次重复最大强度进行 3 组深蹲、卧推和俯身划船，直到达到自愿力竭。此外，参与者在运动前后 30 分钟内摄入 0.4g/kg 的乳清蛋白浓缩物/分离物混合物，以标准化特定于训练的蛋白质时机。通过每日重复表现、肌肉酸痛、生物电阻抗相位角、血浆肌酸激酶（CK）和肿瘤坏死因子-α（TNF-α）来评估恢复情况。
在任何性能重复计数变量方面，两种条件之间均无显著差异（ > 0.05）。然而，仅在 PRO 中，深蹲运动的总重复计数在 T3（19.7 ± 6.8）时显著低于 T1（23.0 ± 7.5； = 0.006）。在整个测试日中，运动前后 CK 浓度均显著升高（ ≤ 0.003），但两种条件之间没有差异。两种饮食条件之间的 TNF-α或肌肉酸痛没有差异。与 PRO 相比，PRO 时的相位角在 T3 时显著更大（8.26 ± 0.82°）与 PRO（8.08 ± 0.80°； = 0.012）。
当控制能量摄入和运动前后的蛋白质摄入时，与重复多天高强度训练后的 PRO 方案相比，短期 PRO 饮食并不能改善肌肉损伤或酸痛的标志物。虽然对于抗阻训练者来说，中等蛋白质摄入量（1.8g/kg/d）可能已经足够，但值得注意的是，在 PRO 时，下肢运动表现和生物电阻抗相位角都得到了维持。需要进行更长期的干预来确定在长时间训练期间或进行大量运动（例如每天训练两次）时，PRO 摄入量是否足够。
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