Consuming milk proteins (casein (CP) and whey (WP)) at night before sleep has been shown to positively influence next morning resting metabolic rate (RMR). No data exist regarding the effect of pre-sleep consumption of CP and WP on the ability to perform resistance exercise (RE) the following morning. The present study compared the effects of low (24 g) and high (48 g) doses of CP and WP and a non-energetic placebo (PLA) consumed 30 min before sleep on morning RMR, and RE performance. Nine active women participated in this randomized, double-blind, crossover study. Next morning RMR was measured via indirect calorimetry. RE was performed on six machines for 2 sets of 10 repetitions, and a 3rd set to failure at 60% of one-repetition maximum to calculate RE volume (weight lifted × sets × repetitions). Magnitude based inferences were used. Compared to the PLA, 48 g CP had a likely increase in RMR (4.0 ± 4.8%) and possibly trivial (1.1 ± 7.0%) effect on RE volume. There were no clear effects of 24 g CP, 24 g and 48 g of WP on RMR and RE volume. In conclusion, 48 g CP elicited favorable changes in morning RMR, with only trivial changes in RE performance.

To determine changes in appetite, affect and cortisol in response to an acute bout of resistance exercise (RE) the morning after consuming whey (WP) and casein (CP) protein and a non-caloric placebo (PLA) consumed pre-sleep, 14 active men (n = 5) and women (n = 9) consumed a single dose of 24 g WP, 48 g WP, 24 g CP, 48 g CP, or PLA 30 min pre-sleep. Prior to and immediately after RE, appetite, affect and cortisol were assessed. Significant time effects were observed for Energetic Arousal and Tense Arousal (p = 0.017) and Feeling Scale and Felt Arousal Scale (p < 0.001). Appetite did not change over time or condition. Cortisol levels increased after RE (p = 0.007). Pre-RE, Tense Arousal was correlated with hunger (r = 0.25, p = 0.047) and desire to eat (r = 0.35, p = 0.005). Post-RE, cortisol was found to be significantly related to Feeling Scale (r = 0.32, p = 0.018), Felt Arousal Scale (r = 0.33, p = 0.015) and Energetic Arousal (r = 0.32, p = 0.018). Varying doses of WP and CP pre-sleep did not have an effect on morning appetite and cortisol, but cortisol was found to be related to affect and appetite.

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