Author(s): AUSSIEKER, T., KREDIG, N., WASSERFURTH, P., HARMSEN, J.F., SPITSCHAN, M., KOHLER, K., Institution: OWL UNIVERSITY OF APPLIED SCIENCES, Country: GERMANY, Abstract-ID: 1984

INTRODUCTION:
Pre-sleep protein supplementation can be a strategy of athletes to achieve daily protein requirements and to sustain amino acid supply during sleep. Among protein sources, casein has traditionally been regarded as the optimal choice for pre-sleep ingestion, in contrast, whey protein is rapidly digested, producing a faster but more transient aminoacidemia. Although whey and casein proteins have been directly compared with respect to overnight muscle protein synthesis, showing no differences between these milk protein fractions. Food intake before sleep can affect sleep quality, however, the effects of different milk protein fractions on sleep quality have not been directly compared.
METHODS:
In a randomized, double-blind, cross-over trial, 9 young, healthy and resistance trained men (n=5) and women (n=4) (age: 24±2 y; BMI: 24.4±2.9 kg/m2) performed resistance exercise sessions on 3 occasions followed by ingestions of either 40 g of whey (WHEY), casein (CASEIN) protein, or an isocaloric maltodextrin control (CON) 30 min before bedtime. Sleep quality was assessed using actigraphy, heart rate variability (HRV) and a subjective sleep questionnaire. Gastrointestinal symptoms were monitored, exercise performance and delayed onset of muscle soreness (DOMS) were evaluated the next day. Data are presented as median and interquartile range (IQR). Friedman tests were used to assess treatment differences between WHEY, CASEIN and CON, post-hoc comparisons were performed using Dunn’s multiple comparisons test. Effect sizes were estimated using Kendall’s coefficient of concordance (W), with values of ~0.1, ~0.3, and ≥0.5 indicating small, moderate, and large effects, respectively.
RESULTS:
Pre-sleep whey protein ingestion improved sleep-onset latency (9.0 [8.0–11.0]; 16.0 [10.0–19.0]; 19.0 [15.0–27.0] min in WHEY, CASEIN, and CON, respectively; W=0.51), sleep efficiency (96% [96–98]; 96% [94–96]; 93% [91–96]; W=0.42), total sleep time (400 [374–404]; 390 [365–412]; 363 [358–412] min; W=0.42) and subjective sleep rating (8.0 [7.0–9.0]; 7.0 [5.0–7.0]; 6.0 [5.0–7.0]; W=0.81) compared to CON (all P<0.05) but not CASEIN (all P>0.05). WHEY led to a significant reduction in DOMS 12 and 24 h post-training when compared to CON (P<0.05; both W=0.64). There were no differences in HRV variables, gastrointestinal symptoms and exercise performance between treatments (all P>0.05).
CONCLUSION:
Pre-sleep whey protein ingestion may enhance sleep quality after resistance training and reduce muscle soreness without affecting gastrointestinal symptoms and exercise performance in healthy young adults. Future research should consider extending the supplementation period to examine long-term effects on performance.