TABLE 2.

Heart rate variability outcomes.

	Time point
Parameter	Pre‐chamber	R1 Pre	R1 10 min	R1 20 min	R2 Pre	R2 10 min	R2 20 min	R2 Post	P‐value
R–R interval (ms)
PLA KME	991.9 ± 126.4 889.9 ± 144.9***	820.6 ± 112.1 756.8 ± 99.3***	433.3 ± 51.54 426.5 ± 41.6	417.6 ± 53.6 410.2 ± 40.6	609.7 ± 77.0 587.2 ± 56.0	420.2 ± 60.9 416.9 ± 45.8	411.1 ± 56.8 403.0 ± 41.3	608.0 ± 81.4 578.8 ± 71.7	Time, P < 0.001 Condition, P < 0.001 Interaction, P < 0.001
RMSSD (ms)
PLA KME	93.2 ± 43.8 69.9 ± 37.1***	49.1 ± 25.1 40.1 ± 28.1***	3.8 ± 2.3 3.8 ± 2.3	3.9 ± 2.7 3.6 ± 1.7	17.0 ± 12.5 22.2 ± 3.2	4.0 ± 2.3 3.7 ± 1.8	4.2 ± 2.9 3.6 ± 1.8	16.0 ± 10.8 12.4 ± 11.9	Time, P < 0.001 Condition, P = 0.009 Interaction, P = 0.002
Stress index (a.u.)
PLA KME	5.4 ± 2.3 7.0 ± 3.0	8.0 ± 2.9 10.5 ± 4.0	60.1 ± 30.2 60.9 ± 27.4	71.8 ± 25.8 81.3 ± 26.0	18.0 ± 7.1 19.0 ± 7.0	57.7 ± 28.9 62.5 ± 28.6	71.9 ± 28.2 82.5 ± 20.9	18.8 ± 8.9 21.7 ± 9.5	Time, P < 0.001 Condition, P = 0.043 Interaction, P = 0.213
SNS index (a.u.)
PLA KME	−0.89 ± 0.8 −0.15 ± 1.1	0.39 ± 1.0 1.19 ± 1.2	14.37 ± 6.1 14.69 ± 4.0	17.73 ± 6.3 19.73 ± 5.9	3.78 ± 2.0 4.17 ± 1.8	14.59 ± 6.3 14.76 ± 5.3	18.10 ± 6.9 20.17 ± 5.3	3.97 ± 2.4 4.81 ± 2.5	Time, P < 0.001 Condition, P = 0.09 Interaction, P = 0.58
PNS index (a.u.)
PLA KME	1.70 ± 1.5 0.59 ± 1.6***	−0.32 ± 1.1 −0.86 ± 1.2**	−3.58 ± 0.4 −3.67 ± 0.3	−3.91 ± 0.4 −3.97 ± 0.3	−2.24 ± 0.7 −2.52 ± 0.5	−3.77 ± 0.5 −3.79 ± 0.4	−3.97 ± 0.5 −4.02 ± 0.3	−2.29 ± 0.7 −2.56 ± 0.7	Time, P < 0.001 Condition, P = 0.54 Interaction, P = 0.87

Note: Data are presented as the mean ± SD, n = 16.

Abbreviations: a.u., arbitrary units; KME, ketone monoester; PLA, placebo; PNS, parasympathetic nervous system; RMSSD, root mean square of successive differences between normal heartbeats; SNS, sympathetic nervous system.

***P < 0.001, **P < 0.01 for KME versus PLA.