Participant demographics and physical characteristics.

<p>Participant demographics and physical characteristics.</p

Average values of F_ENO₅₀ on both control and experimental days.

<p>Error bars indicate standard error.</p

Raw values of F_ENO₅₀ on control and experimental days for extended protocol.

<p>Dashed black lines indicate water control day and solid grey lines indicates experimental day.</p

Cardiovascular, respiratory, and psychological measurements over time.

<p>Cardiovascular, respiratory, and psychological measurements over time.</p

Means ± standard deviations of respiration-uncorrected and respiration-corrected RSA indices, respiration measures, and HR for Still-Face Test episodes.

<p><i>Note:</i> HR = heart rate; V_T = tidal volume; RSA = respiratory sinus arrhythmia; T_TOT = total respiratory cycle time; HR = heart rate; RSA/V_T = RSA normalized by V_T; c = adjusted for T_TOT; logRSA = logarithm(RSA+1); logRSA/V_T = logarithm(RSA/V_T)+1.</p

Individual trajectories of RSA uncorrected and corrected for respiration (both tidal volume and respiration rate) across the three episodes of the first Still-Face Test (n = 23).

<p>Individual trajectories of RSA uncorrected and corrected for respiration (both tidal volume and respiration rate) across the three episodes of the first Still-Face Test (n = 23).</p

Overall ANOVA time effects (df = 4,66 or 2,44) for changes in physiological parameters across Still-Face Tests and paired t-tests (df = 15 or 22) testing changes from Play to Still-Face episodes 1 and 2.

<p><i>Note</i>: P = Play episode; SF1 = Still-Face episode 1; SF2 = Still-Face episode 2; T_TOT = total respiratory cycle time; V_T = tidal volume; RSA = respiratory sinus arrhythmia; logRSA/V_Tc = logarithm of RSA normalized by V_T (logarithm(RSA/V_T)+1), adjusted for T_TOT; HR = heart rate.</p>†<p><i>p</i>-level of both <i>t</i>-tests for each index are Bonferroni-adjusted in this subgroup.</p

ANOVA time effects (<i>df</i> = 4,60 or 2,44) and paired <i>t</i>-tests (<i>df</i> = 15 or 22) measuring reduction in additional respiration-uncorrected and corrected RSA indices during Still-Face Test 1 and 2.

<p><i>Note:</i> V_T = tidal volume; RSA = respiratory sinus arrhythmia; T_TOT = total respiratory cycle time; HR = heart rate; RSA/V_T = RSA normalized by V_T; c = adjusted for total respiratory cycle time; logRSA = logarithm(RSA+1); logRSA/V_T = logarithm(RSA/V_T)+1.</p><p><i>p</i>-level of both tests Bonferroni-adjusted for all indices.</p

Percentages of breaths too short to allow extraction of two inter-beat intervals for peak-valley RSA calculation in infants.

<p><i>Note:</i> RSA = respiratory sinus arrhythmia; Frequencies across episodes (as % of analyzed breaths) and ANOVA time effects for infants with one Still-Face Test (<i>n</i> = 23, <i>df</i> = 2,44) and two Still-Face Tests (<i>n</i> = 16, <i>df</i> = 4,60).</p>†<p><i>p</i><.10.</p

RSA, respiration, and heart rate across Still-Face Test episodes controlled for physical activity: Linear mixed model overall <i>F</i> tests (<i>df</i> = 2 or 4, 50.0 to 67.7), time-varying covariate activity effect <i>F</i>-tests (<i>df</i> = 1, 25.7 to 77.8) and <i>t</i>-tests (<i>df</i> = 52.4 to 77.7) testing changes from Play to Still-Face episode 1 and 2.

<p><i>Note:</i> V_T = tidal volume; RSA = respiratory sinus arrhythmia; T_TOT = total respiratory cycle time; HR = heart rate; RSA/V_T = RSA normalized by V_T; c = adjusted.</p><p>for total respiratory cycle time; logRSA = logarithm(RSA+1); logRSA/V_T = logarithm(RSA/V_T)+1.</p