Abstract
BackgroundDietary protein intakes up to 2.9 g.kg−1.d−1 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.MethodsFourteen resistance-trained individuals underwent two 10-day isocaloric dietary regimes with a protein content of 1.8 g.kg−1.d−1 (PROMOD) or 2.9 g.kg−1.d−1 (PROHIGH) 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−1 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).ResultsNo significant differences were reported between conditions for any of the performance repetition count variables (p > 0.05). However, within PROMOD only, squat performance total repetition count was significantly lower at T3 (19.7 ± 6.8) compared to T1 (23.0 ± 7.5; p = 0.006). Pre and post-exercise CK concentrations significantly increased across test days (p ≤ 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 PROHIGH (8.26 ± 0.82°) compared with PROMOD (8.08 ± 0.80°; p = 0.012).ConclusionsWhen energy intake and peri-exercise protein intake was controlled for, a short term PROHIGH diet did not improve markers of muscle damage or soreness in comparison to a PROMOD approach following repeated days of intensive training. Whilst it is therefore likely that moderate protein intakes (1.8 g.kg−1.d−1) may be sufficient for resistance-trained individuals, it is noteworthy that both lower body exercise performance and bioelectrical phase angle were maintained with PROHIGH. Longer term interventions are warranted to determine whether PROMOD intakes are sufficient during prolonged training periods or when extensive exercise (e.g. training twice daily) is undertaken.
Highlights
Dietary protein intakes up to 2.9 g.kg−1.d−1 and protein consumption before and after resistance training may enhance recovery, resulting in hypertrophy and strength gains
Dietary intakes By standardising the representative of the moderate protein condition (PROMOD) condition this resulted in an 18.4% reduction in daily protein intake compared to habitual levels, whereas the representative of the high protein condition (PROHIGH) condition resulted in a 26.5% increase in typical protein intake for this cohort
Energy intake was comparable across both intervention periods (PROMOD: 2262.64 ± 495.78 kcal.d−1 and PROHIGH: 2377.14 ± 509.97 kcal.d−1; p > 0.05)
Summary
Dietary protein intakes up to 2.9 g.kg−1.d−1 and protein consumption before and after resistance training may enhance recovery, resulting in hypertrophy and strength gains. It remains unclear whether protein quantity or nutrient timing is central to positive adaptations. Several factors are advantageous for recovery and enhanced athletic performance in the following training sessions. Exercise-induced muscle damage that results in muscle soreness, reduces the ability to train and is potentially detrimental for the performance of a strength athlete [3]. Previous research has suggested that peri-exercise protein ingestion is beneficial for muscle hypertrophy, strength gains and recovery after intense training sessions [8,9,10]
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