Active women demonstrate acute autonomic and hemodynamic shifts following exercise in heat and humidity: A pilot study

Figures & data

Table 1. Demographic and Baseline Measurements Prior to Each Trial

	Variable	Mean ± SD
Demographic	Age (years)	31.7 ± 7.6
	VO2Peak (mL/kg/min)	43.9 ± 5.1
	BF %	25.7 ± 5.6
	FFM (kg)	50.8 ± 1.8
	FM (kg)	17.8 ± 4.9
Hot Trial Baseline	Body Mass (kg)	67.5 ± 4.4
	Resting HR (bpm)	61 ± 9.4
	Resting SBP (mmHg)	108.6 ± 8.6
	Resting DBP (mmHg)	72.0 ± 4.0
Moderate Trial Baseline	Body Mass (kg)	67.7 ± 4.5
	Resting HR (bpm)	60 ± 11.0
	Resting SBP (mmHg)	109.1 ± 8.8
	Resting DBP (mmHg)	72.7 ± 3.4

VO₂peak = peak volume of oxygen consumption; mL/kg/min = milliliter of oxygen per kilogram body mass per minute; BF% = body fat percentage; FFM = fat-free mass; FM = fat mass; kg = kilograms; HR = heart rate; bpm = beats per minute; SBP = systolic blood pressure; DBP = diastolic blood pressure; mmHg = millimeters of mercury

Figure 1. Changes in LnRMSSD before exercise and during 60 min of recovery. Horizontal bar indicates mean for a condition at a given time point *Indicates significant pairwise difference between temperatures at the given time point

Figure 2. Changes in LnHF before exercise and during 60 min of recovery. Horizontal bar indicates mean for a condition at a given time point

*Indicates significant pairwise difference between temperatures at the given time point.

Figure 3. Changes in LF before exercise and during 60 min of recovery. Horizontal bar indicates mean for a condition at a given time point

*Indicates significant pairwise difference between temperatures at the given time point.

Figure 4. Changes in LnLF:HF before exercise and during 60 min of recovery. Horizontal bar indicates mean for a condition at a given time point

*Indicates significant pairwise difference between temperatures at the given time point.

Table 2. Baseline and Supine Recovery Hemodynamics

Variable	Recovery Time	Heat	Control	Difference (95% CI)	Effect Size (d)		p
						Time	Temp	I
HR (bpm)	Pre-Exercise	61.1 ± 9.4	59.7 ± 10.6	1.4 (−3.4, 6.3)	0.14	<0.001	0.002	0.007
	0 Min	101.1 ± 12.6	81.1 ± 13.4	20.0 (2.9, 37.1)*	1.54
	10 Min	89.7 ± 12.0	72.6 ± 13.9	17.1 (10.2, 24.1)*	1.32
	20 Min	80.6 ± 11.6	68.0 ± 12.2	12.6 (5.04, 20.1)*	1.06
	30 Min	81.7 ± 10.8	69.7 ± 10.0	12.0 (7.2, 16.8)*	1.15
SBP (mmHg)	Pre-Exercise	108.6 ± 8.6	109.1 ± 8.8	−0.6 (−2.9, 1.7)	−0.06	<0.001	0.967	0.013
	0 Min	118.6 ± 4.4	112.9 ± 8.6	5.7 (−2.1, 13.52)	0.83
	10 Min	108.9 ± 4.5	112.3 ± 6.7	−3.4 (−6.7, −0.3)*	−0.60
	20 Min	106.3 ± 7.1	108.6 ± 7.6	−2.3 (−6.3, 1.8)	−0.31
	30 Min	106.3 ± 7.8	105.4 ± 9.4	0.9 (−5.3, 7.0)	0.10
DBP (mmHg)	Pre-Exercise	72.0 ± 4.0	71.4 ± 5.9	0.6 (−6.8, 7.9)	0.12	0.001	0.016	0.011
	0 Min	57.1 ± 8.4	67.1 ± 6.9	−10.0 (−20.3, 0.3)	−1.30
	10 Min	55.4 ± 11.3	70.0 ± 2.0	−14.6 (−23.7, −5.5)*	−1.80
	20 Min	63.4 ± 6.6	69.1 ± 4.7	−5.7 (−13.3, 1.9)	−0.99
	30 Min	68.3 ± 2.1	69.7 ± 5.7	−1.4 (−6.5, 3.7)	−0.32

Data is presented as Mean ± SD.

*Statistically significant difference between heat and control in Bonferroni-adjusted pairwise comparison.

CI = confidence interval; Time = main effect for time; Temp = main effect for temperature (heat/control); I = temperature x time interaction; HR = heart rate; bpm = beats per minute; SBP = systolic blood pressure; mmHg = millimeters of mercury; DBP = diastolic blood pressure.

Table 3. Hemodynamics during Orthostatic Challenge

Variable	Time Point	Heat	Control	Difference (95% CI)	Effect Size (d)		p
						Time	Temp	I
HR (bpm)	30 Min Supine Recovery	81.7 ± 10.8	69.7 ± 10.0	12.0 (7.224, 16.8)	1.15	< 0.001	0.011	0.992
	1 Min	92.6 ± 16.6	82.3 ± 11.5	10.3 (−2.0, 22.5)	0.72
	3 Min	98.4 ± 16.4	85.7 ± 11.3	12.7 (−0.2, 25.6)	0.90
	5 Min	95.4 ± 14.6	85.6 ± 17.0	9.9 (−3.8, 23.5)	0.62
	10 Min	93.7 ± 14.6	82.9 ± 10.3	10.9 (−6.2, 27.9)	0.85
SBP (mmHg)	30 Min Supine Recovery	106.3 ± 7.8	105.4 ± 9.4	0.9 (−5.3, 7.0)	0.10	< 0.001	0.152	0.378
	1 Min	95.1 ± 11.4	98.3 ± 6.0	−3.1 (−16.8, 10.5)	−0.35
	3 Min	93.4 ± 5.1	97.1 ± 8.3	−3.7 (−11.4, 3.9)	−0.54
	5 Min	93.4 ± 5.3	99.4 ± 9.0	−6.0 (−14.5, 2.5)	−0.85
	10 Min	90.9 ± 5.5	98.0 ± 7.9	−7.1 (−11.3, −3.0)	−1.04
DBP (mmHg)	30 Min Supine Recovery	68.3 ± 2.1	69.7 ± 5.7	−1.4 (−6.5, 3.6)	−0.33	0.072	0.064	0.08
	1 Min	72.6 ± 4.1	74.6 ± 8.3	−2.0 (−3.7, 5.4)	−0.31
	3 Min	71.4 ± 5.3	74.3 ± 4.4	−2.86 (−9.7, 0.04)	−0.60
	5 Min	71.4 ± 5.6	74.6 ± 4.9	−3.1 (−6.3, 0.35)	−0.61
	10 Min	69.4 ± 7.0	78.3 ± 4.4	−8.9 (−14.4, −3.2)	−1.52

Data is presented as Mean ± SD.

*Statistically significant difference between heat and control in Bonferroni-adjusted pairwise comparison

CI = confidence interval; Time = main effect for time; Temp = main effect for temperature (heat/control); I = temperature x time interaction; HR = heart rate; bpm = beats per minute; SBP = systolic blood pressure; mmHg = millimeters of mercury; DBP = diastolic blood pressure.

Table

ACSM	American College of Sports Medicine
ANOVA	Analysis of Variance
BP	Blood Pressure
DBP	Diastolic Blood Pressure
DEXA	Dual-Energy X-ray Absorptiometry
HF	High Frequency Power
HIIT	High-Intensity Interval Training
HR	Heart Rate
HRV	Heart Rate Variability
LF	Low Frequency Power
LF:HF	Ratio of Low Frequency Power to High Frequency Power
MAP	Mean Arterial Pressure
RER	Respiratory Exchange Ratio
RH	Relative Humidity
RMSSD	Root Mean Square of the Successive Difference
RPE	Rating of Perceived Exertion
SBP	Systolic Blood Pressure