Presleep alpha-Lactalbumin Consumption Does Not Improve Sleep Quality or Time-Trial Performance in Cyclists

We tested the hypothesis that presleep consumption of a-lactalbumin (LA). a fraction of whey with a high abundance of tryptophan, would improve indices of sleep quality and time-trial (TT) performance in cyclists relative to an isonitrogenous collagen peptide (CP) supplement lacking tryptophan. Using randomized, double-blind, crossover designs. cyclists consumed either 40 g of LA or CP 2 hr prior to sleep. In Study 1, six elite male endurance track cyclists (age 23 t 6 years, (V)over dotO(2)peak 70.2 t 4.4 ml.kg(-1).min(-1)) consumed a supplement for three consecutive evenings before each 4-km TT on a velodrome track, whereas in Study 2, six well-trained cyclists (one female; age 24 t 5 years, (V)over dotO(2)peak 66.9 t 8.3 ml.kg(-1).min(-1)) consumed a supplement the evening before each 4-km TT on a stationary cycle ergometer. Indices of sleep quality were assessed with wrist-based actigraphy. There were no differences between the CP and LA supplements in terms of total time in bed, total sleep time, or sleep efficiency in Study 1 (LA: 568 +/- 71 min, 503 +/- 67 min, 88.3% +/- 3.4%; CP: 546 +/- 30 min, 479 +/- 35 min, 87.8% +/- 3.1%; p = .41, p = .32, p = .74, respectively) or Study 2 (LA: 519 +/- 90 min. 450 +/- 78 min, 87.2% +/- 7.6%; CP: 536 +/- 62 min, 467 +/- 57 min. 87.3% +/- 6.4%; p = .43, p = .44, p = .97. respectively). Similarly, time to complete the 4-km TT was unaffected by supplementation in Study 1 (LA: 274.9 +/- 7.6 s; CP: 275.5 +/- 7.2 s; p = .62) and Study 2 (LA: 344.3 +/- 22.3 s; CP: 343.3 +/- 23.0 s; p = .50). Thus, relative to CP, consuming LA 2 hr prior to sleep over 1-3 days did not improve actigraphy-based indices of sleep quality or 4-km TT performance in cyclists.