Underweight and overweight men have greater exercise-induced dyspnoea than normal weight men

Figures & data

Table I. Mean (± SD) anthropometric and lung function variables for all subjects in underweight, normal weight, and overweight groups (n = 37).

	Underweight (n = 13)	Normal (n = 12)	Overweight (n = 12)	P value^a
Age (years)	21.4 ± 4.2	22.0 ± 4.3	21.7 ± 5.3	0.953
BMI (kg m^-2)	17.4 ± 1.1	22.3 ± 2.1	28.7 ± 2.9	<0.0001
Height (cm)	174 ± 6	173 ± 4	175 ± 9	0.809
Weight (kg)	52 ± 5	66 ± 8	89 ± 15	<0.0001
FVC (L)	4.13 ± 0.65	4.15 ± 0.61	5.10 ± 1.18	0.010
FEV1 (L)	3.32 ± 0.60	3.48 ± 0.61	4.12 ± 0.88	0.020
FEV1/FVC % ratio (%)	79.4 ± 7.8	83.7 ± 6.3	80.9 ± 3.1	0.226
PEF (L min^-1)	511.8 ± 123.5	556.9 ± 103.5	588.0 ± 103.4	0.238
MVV (L min^-1)	136.2 ± 29.8	143.7 ± 32.0	170.6 ± 41.6	0.048
PImax (cmH2O)^b	79.8 ± 34.0	106.3 ± 36.8	144.9 ± 66.4	0.010
PEmax (cmH2O)^b	80.4 ± 24.3	107.3 ± 19.6	111.9 ± 25.7	0.006
RMS (cmH2O)^b	80.1 ± 23.5	106.9 ± 25.6	128.5 ± 43.4	0.004

^aDifference between three groups.

^b n = 12, 12, and 10 per group, respectively.

BMI = body mass index; FEV₁ = forced expiratory volume in 1 s; FEV₁/FVC % ratio = ratio of FEV₁ to FVC; FVC = forced vital capacity; MVV = maximum voluntary ventilation; PEF = peak expiratory flow; P_Emax = maximum static expiratory mouth pressure; P_Imax = maximum static inspiratory mouth pressure; RMS = respiratory muscle strength.

Table II. Comparison of mean (± SD) indices of the breathlessness/ventilation relationship and exercise variables between underweight, normal weight, and overweight groups (n = 37).

	Underweight (n = 13)	Normal (n = 12)	Overweight (n = 12)	P value^a
r^2 value	0.94 ± 0.03	0.97 ± 0.02	0.96 ± 0.03	<0.050
VAS/VI slope (mm min L^-1)	2.73 ± 2.99	2.05 ± 1.40	1.96 ± 1.04	0.575
VAS/VI intercept (L min^-1)	16.1 ± 5.84	22.7 ± 7.54	17.1 ± 3.96	0.022
Wmax (W)	113.9 ± 25.0	120.0 ± 29.5	126.7 ± 27.4	0.510
Wmax per kg (W/kg)	2.17 ± 0.53	1.80 ± 0.36	1.46 ± 0.39	0.001
VImax (L min^-1)	48.0 ± 12.0	45.3 ± 11.2	48.6 ± 8.9	0.725
fC1min (beats min^-1)	91.8 ± 12.9	88.0 ± 13.5	91.9 ± 13.6	0.711
fC60 (beats min^-1)	123.7 ± 15.4	116.8 ± 12.3	113.8 ± 16.3	0.239
fCmax (beats min^-1)	153.0 ± 22.0	145.7 ± 18.8	144.7 ± 19.1	0.533

^aDifference between three groups.

f_C1min = heart rate after 1 min of exercise; f_C60 = heart rate at 60 watts of exercise; f_Cmax = maximum heart rate; r² = coefficient of determination; VAS/V_I = relationship of visual analogue scale against inspired ventilation; V_Imax = maximum ventilation; W_max = maximum work-load; W_max per kg = W_max per kg body mass.

Figure 1. A representation of the mean changes in the VAS/V_I relationship for all subjects in the three BMI groups. There were no differences in the slope values, but the NW intercept value was significantly greater relative to values for UW and OW subjects.

Table III. Linear correlation coefficients for selected correlations, using data from all subjects.

Correlations	r value (correlation coefficient)	P value
BMI versus RMS	+0.448	0.008
BMI versus MVV	+0.419	0.009
BMI versus FVC	+0.454	0.004
BMI versus PEF	+0.333	0.044
BMI versus fC60	–0.339	0.040
PImax versus FVC	+0.409	0.018
PImax versus Wmax per kg	–0.373	0.030
VAS/VI slope versus RMS	–0.377	0.028
VAS/VI slope versus r^2	–0.407	0.012
fC60 versus MVV	–0.453	0.005
fC60 versus PImax	–0.378	0.027
fC60 versus FVC	–0.490	0.002

BMI = body mass index; f_C60 = heart rate at 60 watts of exercise; FVC = forced vital capacity; MVV = maximum voluntary ventilation; PEF = peak expiratory flow; P_Imax = maximum static inspiratory mouth pressure; r² = coefficient of determination; RMS = respiratory muscle strength; VAS/V_I = relationship of visual analogue scale against inspired ventilation; W_max per kg = maximum work-load per kg body mass.

Table IV. Multiple regression analysis of the VAS/V_I slope and intercept, showing significant predictor variables.

Dependent variable	Independent variable (predictor)	Standardized beta coefficient	P value
VAS/VI slope	FEV1/FVC % ratio	2.684	<0.00001
	VImax	–1.184	0.004
	PEmax	–0.811	0.029
VAS/VI intercept	VAS/VI r^2 value	0.932	<0.00001

FEV₁/FVC % ratio = ratio of FEV₁ to FVC; P_Emax = maximum static expiratory mouth pressure; r² = coefficient of determination; VAS/V_I = relationship of visual analogue scale against inspired ventilation; V_Imax = maximum ventilation.