Effects of pre-sleep protein supplementation on plasma markers of muscle damage and inflammatory cytokines resulting from sprint interval training in trained swimmers

Figures & data

Table 1. Training history two months prior to participation in this study.

	Swimming				Endurance					Other
	PRO		CHO	p	PRO		CHO			PRO		CHO
	Training history
Duration (h wk^−1)	8.3 ± 4.3		7.8 ± 3.2	0.71	3.9 ± 2.8		2.4 ± 2.3			2.1 ± 1.9		3.4 ± 3.1
Distance (km wk^−1)	26 ± 11		23 ± 9	0.64

Data were based on questionnaires and logs. Statistical analysis for training history was based on actual swimming sessions only. Endurance training covers a range of disciplines (i.e. running and cycling).

Table 2. Characteristics of the participants.

		Characteristics
	PRO	CHO	ALL
Age (years)	23.7 ± 2.5	22.6 ± 2.9	23.1 ± 2.7
Body mass (kg)	81.4 ± 3.3	81.9 ± 2.9	81.6 ± 3.1
Body fat (%)	10.9 ± 1.5	11.6 ± 1.6	11.2 ± 1.5
Height (cm)	180.7 ± 5.9	180.8 ± 6.7	180.7 ± 6.3
Energy (Mj day^−1)	12.6 ± 0.3	12.8 ± 0.4	12.8 ± 0.4
Protein (%energy)	13.3 ± 1.1	13.4 ± 0.8	13.4 ± 0.8
Protein (g kg^−1 day^−1)	1.26 ± 0.05	1.36 ± 0.07	1.36 ± 0.07
Carbohydrate (%energy)	51.3 ± 4.6	52.6 ± 2.5	52.6 ± 2.5
Fat (%energy)	35.3 ± 1.0	33.8 ± 1.4	33.8 ± 1.4

Values are means ± SD.

Figure 1. Overview of experimental protocol.

Table 3. Standardized diet.

	Groups		p
	PRO	CHO
Energy (Mj day^−1)	10.3 ± 0.2	10.2 ± 0.3	0.95
Protein (%energy)	17.1 ± 0.2	17.2 ± 0.3	0.51
Protein (g day^−1)	105.8 ± 4.3	106.7 ± 3.8	0.67
Carbohydrate (%energy)	56.3 ± 0.7	56.1 ± 0.3	0.18
Carbohydrate (g day^−1)	346.3 ± 7.1	349.0 ± 17.4	0.92
Fat (%energy)	20.0 ± 0.0	20.0 ± 0.0	1.00
Fat (g day^−1)	54.2 ± 1.0	54.9 ± 1.3	0.26

Values are means ± SD.

Table 4. Physiological and performance adaptations to interventions.

	PRO				CHO
	Pre-test	Post-test	P	ES	Pre-test	Post-test	P	ES
$\mathrm{V}$O2peak (ml kg^−1 min^−1)	53.0 ± 4.7	§55.0 ± 3.7	.002	0.51	51.1 ± 5.0	§52.5 ± 5.2	.007	0.37
v$\mathrm{V}$O2peak (km min^−1)	1.27 ± .06	§1.30 ± .05	.011	0.54	1.24 ± .04	§1.28 ± .03	.007	0.61
$\mathrm{V}$O2/HR (ml beat^−1 min^−1)	2.9 ± 2.7	21.1 ± 2.1	.676	0.08	21.4 ± 2.5	21.8 ± 1.7	.283	0.18
HR at $\mathrm{V}$O2peak (%max)	88.7 ± 2.3	89.1 ± 1.9	.612	0.18	88.0 ± 3.5	88.6 ± 2.3	.329	0.21
VT1 (%$\mathrm{V}$O2peak)	75.4 ± 3.4	75.9 ± 2.5	.516	0.16	78.0 ± 4.3	78.6 ± 4.2	.529	0.14
VT2 (%$\mathrm{V}$O2peak)	87.6 ± 2.5	88.0 ± 2.7	.874	0.15	86.7 ± 3.2	87.2 ± 3.0	.407	0.16
PPO (W)	212.0 ± 22.2	§218.6 ± 19.7	.024	0.31	219.6 ± 22.2	§23.5 ± 26.4	.008	0.44
MPO (W)	141.0 ± 13.4	§145.7 ± 15.8	.013	0.32	146.1 ± 1.6	§15.0 ± 1.5	.022	0.37
200-m swimming (s)	129.3 ± 13.7	129.0 ± 13.8	.100	0.07	128.2 ± 11.6	127.9 ± 12.2	.711	0.02

Values are means ± SD.

$V$O₂peak, peak oxygen uptake; v$V$O₂peak, velocity at $\mathrm{V}$O₂ peak, peak oxygen uptake; VT₁, first ventilatory threshold; VT₂, second ventilatory threshold; HR, heart rate; PPO, peak power output; MPO, mean power output.

§Significantly greater than pre-training value (P < 0.05).

Figure 2. Creatine kinase concentrations after the first and last training sessions. N = 10 for each group. *Significantly greater than resting values. ‡ Significantly higher than all other time points (p < 0.05).

Figure 3. Concentrations of (a) Interleukin-6 (IL-6), (b) IL-10, (c) IL-6/IL-10 ratio, and (d) tumor necrosis factor alpha (TNFα) in both PRO and CHO groups. *Significantly greater than resting values. ‡ Significantly higher than all other time points. #Significantly lower than rest and immediately after SIT in the first session. †Significantly lower than rest and immediately after SIT in the last session (p < 0.05).