Effects of menthol gum versus control gum on dyspnoea and physiological variables at the end of exercise

VariablesMentholControlCondition effect
BaselineEnd-exerciseBaselineEnd-exerciseAdjusted mean difference#p-value
Dyspnoea, mBorg0.9±14.4±1.6***1±1.04.7±1.7***−0.3 (−0.5–−0.0)0.058
Leg discomfort, mBorg0.6±1.12.8±2.1***0.6±12.9±2.3***−0.0 (−0.3–0.2)0.807
SpO2, %92.6±3.785.7±7***92.6±3.386.3±6.2***−0.4 (−1.0–0.3)0.255
Lowest SpO2, %82.7±7.383.1±6.6−0.4 (−1.2–0.3)0.263
Heart rate, beats per min91.4±17.8115.3±15.2***92.3±17.5114.5.9±15.7***4.4 (−1.2–9.9)0.124
Respiratory rate, cycles per min18.6±4.624.1±9.5***19±5.224.1±5.9 ***0.3 (−2.1–2.6)0.827
Tidal volume, L0.8±0.31.1±0.5 ***0.8±0.41.1±0.5***0.0 (−0.0–0.1)0.172
Minute ventilation, L·min−113.9±5.125.6±9.3***14.7±5.625.8±9***−0.1 (−1.5–1.3)0.924
Inspiratory capacity, L1.8±0.61.7±0.6**1.9±0.71.8±0.7−0.0 (−0.2–0.1)0.449
6MWD, m461.1±124.2458.7±124.92.6 (−4.1–9.4)0.447
6MWD, % pred73.1±20.772.8±20.70.37 (−0.76–1.5)0.495

Continuous data are presented as mean±sd and as mean (95% CI) for the difference between the two conditions. Mean differences were calculated using a mixed model adjusted for baseline values, and the sequence (order of conditions) was used to assess the carry-over effect, with participants as random effects. Within-condition changes (before-after test) were compared using a paired t-test. *: p<0.05; **: p<0.01; and ***: p<0.001 for before–after analysis of a condition. mBorg: modified Borg scale from 0 to 10 (0: no fatigue or dyspnoea, 10: maximal fatigue or dyspnoea). For leg discomfort, there was evidence for a period or cross-over effect (p=0.050), this result should be taken with caution. There was no evidence of a period or cross-over effect on the other outcomes. SpO2: oxygen saturation measured by pulse oximetry; 6MWD: 6-min walking distance. #: difference for menthol − control.