Pre-sleep protein supplementation in professional cyclists during a training camp: a three-arm randomized controlled trial

Figures & data

Figure 1. Schematic summary of the study design. Abbreviations: RESTQ-Sport, Recovery-Stress Questionnaire for Athletes.

Table 1. Total energy and macronutrient intake by group.

Outcome	Pre-sleep PRO	Afternoon PRO	Placebo	P-value for group effect	Effect size (ηp^2)
Total energy (Kcal/d)	3381 ± 409	3291 ± 520	3114 ± 273	0.436	0.076
Carbohydrates (g/d)	498 ± 212	458 ± 166	411 ± 74	0.564	0.053
Carbohydrates (g/kg/day)	7.74 ± 3.51	6.75 ± 2.82	6.49 ± 1.20	0.625	0.044
Carbohydrates (%)	59.8 ± 6.7	60.9 ± 5.4	62.1 ± 5.7	0.732	0.029
Protein (g/d)	231 ± 20*	223 ± 12*	164 ± 13	<0.001	0.816
Protein (g/kg/d)	3.57 ± 0.35*	3.26 ± 0.35*	2.59 ± 0.30	<0.001	0.626
Protein (%)	29.1 ± 4.9	29.7 ± 5.9	24.7 ± 1.8	0.079	0.214
Fat (g/d)	88.0 ± 37.2	89.9 ± 20.3	82.3 ± 21.1	0.846	0.016
Fat (g/kg/d)	1.35 ± 0.52	1.32 ± 0.34	1.31 ± 0.38	0.986	0.001
Fat (%)	10.8 ± 4.1	12.5 ± 2.3	12.8 ± 4.3	0.502	0.063

Data are shown as mean ± SD and expressed as units per day. Abbreviations: Afternoon PRO, protein supplementation in the afternoon; Pre-sleep PRO, protein supplementation before sleep. Symbol: * Significant post-hoc differences (p < 0.001) compared to Placebo.

Figure 2. Differences between study groups on the Hooper index sub-items and total score reported daily during the training camp. Abbreviations: Afternoon PRO: protein supplementation provided in the afternoon; DOMS, delayed-onset muscle soreness; Pre-sleep PRO, protein supplementation before sleep.

Figure 3. Differences between study groups on the height attained during a countermovement jump (CMJ). Abbreviations: Afternoon PRO, protein supplementation provided during the afternoon; Pre-sleep PRO, protein supplementation before sleep.

Table 2. Hooper index (average scores reported during the training camp) by group.

Hooper index scores	Pre-sleep PRO	Afternoon PRO	Placebo	P-value for group effect	Effect size (ηp^2)
Individual items (0 to 7)
Stress	2.5 ± 1.1	2.5 ± 1.2	2.2 ± 0.7	0.803	0.046
Sleep	2.7 ± 1.2	2.3 ± 0.8	2.9 ± 0.5	0.475	0.073
DOMS	3.6 ± 0.6	3.5 ± 0.7	2.8 ± 0.6	0.043*	0.385
Fatigue	3.7 ± 0.7	3.4 ± 0.8	3.2 ± 0.5	0.364	0.070
Total (0 to 28)	12.5 ± 2.9	11.8 ± 2.9	11.0 ± 2.0	0.564	0.071

Data are shown as mean ± SD. Although a significant group effect (p = 0.043) was observed for delayed-onset muscle soreness (DOMS), post hoc analyses revealed no specific between-group differences. Abbreviations: Afternoon PRO, protein supplementation in the afternoon; DOMS, delayed-onset muscle soreness; Pre-sleep PRO, protein supplementation before sleep. Symbol: * no between-group differences in post-hoc analyses

Table 3. Results of the Recovery–Stress Questionnaire for Athletes (RESTQ-Sport) by group.

Item	Pre-sleep PRO		Afternoon PRO		Placebo		P-value for time effect	P-value for group-by-time effect	Effect size (ηp^2)
	Baseline	Post	Baseline	Post	Baseline	Post
General_Stress	0.43 ± 0.69	0.34 ± 0.37	0.68 ± 0.57	1.25 ± 0.51	0.78 ± 0.57	0.71 ± 0.61	0.734	0.153	0.164
Emotional stress	1.03 ± 0.91	0.81 ± 0.81	1.09 ± 0.87	1.09 ± 0.87	1.21 ± 0.79	1.00 ± 0.81	0.535	0.906	0.009
Social stress	0.78 ± 0.93	0.65 ± 0.59	0.81 ± 0.76	0.65 ± 0.26	0.65 ± 0.56	0.50 ± 0.61	0.337	0.995	0.000
Conflicts pressure	2.03 ± 1.28	1.71 ± 1.19	2.12 ± 1.52	2.40 ± 0.54	1.87 ± 0.89	1.62 ± 0.75	0.686	0.517	0.061
Fatigue	1.28 ± 1.01	1.62 ± 0.66	1.18 ± 0.63	1.90 ± 0.80	1.53 ± 1.44	1.46 ± 0.86	0.085	0.247	0.125
Lack of energy	0.84 ± 0.85	1.00 ± 0.95	1.34 ± 1.01	1.15 ± 0.68	1.06 ± 0.82	1.18 ± 0.86	0.874	0.730	0.030
Physical complaints	0.78 ± 0.55	1.06 ± 0.54	0.75 ± 0.71	1.15 ± 0.70	1.12 ± 0.86	1.37 ± 1.03	0.057	0.910	0.009
Success	3.40 ± 1.00	2.40 ± 1.09	2.87 ± 1.15	2.31 ± 1.23	3.03 ± 0.82	2.81 ± 0.90	0.004**	0.243	0.126
Social recovery	3.25 ± 1.50	3.71 ± 0.60	2.96 ± 1.63	3.50 ± 1.25	3.00 ± 1.06	3.93 ± 1.09	0.034*	0.769	0.025
Physical recovery	2.93 ± 0.81	3.12 ± 1.12	3.00 ± 1.63	2.96 ± 1.27	3.28 ± 1.41	3.06 ± 1.03	0.932	0.794	0.022
General well being	3.65 ± 1.20	4.68 ± 1.03	3.75 ± 1.37	4.43 ± 0.99	4.21 ± 0.80	4.68 ± 1.72	0.016*	0.852	0.015
Sleep quaity	3.56 ± 0.88	3.59 ± 0.58	4.03 ± 0.93	3.68 ± 1.46	4.15 ± 0.37	3.46 ± 1.12	0.165	0.461	0.071
Disturbed breaks	0.84 ± 0.46	1.03 ± 0.77	0.59 ± 0.58	1.37 ± 2.32	0.84 ± 0.90	1.28 ± 1.85	0.159	0.753	0.027
Emotional exhaustion	0.68 ± 0.47	0.46 ± 0.66	0.84 ± 0.54	1.59 ± 2.12	0.81 ± 0.71	1.43 ± 1.19	0.229	0.401	0.083
Injury	1.28 ± 0.89	1.93 ± 0.88	1.87 ± 1.73	2.59 ± 1.42	1.65 ± 0.85	2.12 ± 0.98	0.007**	0.877	0.012
Being in shape	3.71 ± 1.04	3.59 ± 1.43	4.25 ± 1.19	3.90 ± 1.58	3.59 ± 1.36	3.84 ± 1.49	0.769	0.613	0.046
Personal accomplishment	3.12 ± 1.06	2.96 ± 1.31	2.93 ± 0.94	2.90 ± 1.28	3.15 ± 0.51	3.43 ± 0.41	0.887	0.701	0.033
Self efficacy	3.65 ± 1.48	3.87 ± 1.70	3.90 ± 1.31	3.90 ± 1.41	3.34 ± 1.15	4.03 ± 1.44	0.232	0.517	0.061
Sefl regulation	3.62 ± 1.24	3.68 ± 1.71	3.96 ± 1.29	3.90 ± 1.26	4.12 ± 1.14	4.25 ± 0.55	0.858	0.944	0.005

Data are shown as mean ± SD. Abbreviations: Afternoon PRO, protein supplementation in the afternoon; Pre-sleep PRO, protein supplementation before sleep. Symbols for significant time effect: *p < 0.05, **p < 0.01.

Table 4. Body composition by group.

Variable	Pre-sleep PRO		Afternoon PRO		Placebo		P-value for time effect	P-value for group-by-time effect	Effect size (ηp^2)
	Baseline	Post	Baseline	Post	Baseline	Post
Body mass (kg)	65.0 ± 6.3	65.3 ± 6.4	68.9 ± 5.8	70.2 ± 6.2	63.5 ± 4.9	64.3 ± 5.0	<0.001***	0.043^#	0.259
Fat mass (kg)	6.0 ± 1.0	6.2 ± 1.2	7.6 ± 1.5	7.2 ± 1.6	6.4 ± 1.1	6.4 ± 1.1	0.445	0.057	0.238
Fat-free mass (kg)	59.0 ± 6.4	59.1 ± 7.0	61.3 ± 5.2	63.0 ± 5.7	57.2 ± 4.4	57.9 ± 4.7	0.001**	0.018^#	0.318
Muscle mass (kg)	33.6 ± 4.0	33.6 ± 4.2	34.8 ± 3.1	35.8 ± 3.4	32.3 ± 2.7	32.7 ± 2.8	0.001**	0.008^##	0.367

Data are shown as mean ± SD. Abbreviations: Afternoon PRO, protein supplementation in the afternoon; Pre-sleep PRO, protein supplementation before sleep. Symbols for significant time effect: **p < 0.01, ***p < 0.001. Symbols for a significant group-by-time effect: ^#p < 0.05, ^##p < 0.01. There were no between-group differences in post-hoc analyses.

Table 5. Field-based cycling performance by group.

Outcome	Pre-sleep PRO		Afternoon PRO		Placebo		P-value for time effect	P-value for group-by-time effect
	Baseline	Post	Baseline	Post	Baseline	Post			Effect size (ηp^2)
1-min time trial (W)	646 ± 78	631 ± 74	665 ± 71	681 ± 79	624 ± 56	614 ± 74	0.729	0.233	0.129
5-min time trial (W)	418 ± 31	399 ± 17	445 ± 42	428 ± 50	411 ± 24	395 ± 41	0.002**	0.966	0.003
20-min time trial (W)	349 ± 27	344 ± 21	370 ± 31	344 ± 21	350 ± 22	345 ± 34	0.119	0.999	0.000
Critical power (W)	344 ± 24	334 ± 16	369 ± 33	355 ± 39	344 ± 20	335 ± 33	0.004**	0.858	0.015

Data are shown as mean ± SD. Abbreviations: Afternoon PRO, protein supplementation in the afternoon; Pre-sleep PRO, protein supplementation before sleep. Symbols for significant time effect: **p < 0.01.