Effects of menthol gum versus control gum on dyspnoea and physiological variables at the end of exercise
| Variables | Menthol | Control | Condition effect | |||
| Baseline | End-exercise | Baseline | End-exercise | Adjusted mean difference# | p-value | |
| Dyspnoea, mBorg | 0.9±1 | 4.4±1.6*** | 1±1.0 | 4.7±1.7*** | −0.3 (−0.5–−0.0) | 0.058 |
| Leg discomfort, mBorg | 0.6±1.1 | 2.8±2.1*** | 0.6±1 | 2.9±2.3*** | −0.0 (−0.3–0.2) | 0.807 |
| SpO2, % | 92.6±3.7 | 85.7±7*** | 92.6±3.3 | 86.3±6.2*** | −0.4 (−1.0–0.3) | 0.255 |
| Lowest SpO2, % | 82.7±7.3 | 83.1±6.6 | −0.4 (−1.2–0.3) | 0.263 | ||
| Heart rate, beats per min | 91.4±17.8 | 115.3±15.2*** | 92.3±17.5 | 114.5.9±15.7*** | 4.4 (−1.2–9.9) | 0.124 |
| Respiratory rate, cycles per min | 18.6±4.6 | 24.1±9.5*** | 19±5.2 | 24.1±5.9 *** | 0.3 (−2.1–2.6) | 0.827 |
| Tidal volume, L | 0.8±0.3 | 1.1±0.5 *** | 0.8±0.4 | 1.1±0.5*** | 0.0 (−0.0–0.1) | 0.172 |
| Minute ventilation, L·min−1 | 13.9±5.1 | 25.6±9.3*** | 14.7±5.6 | 25.8±9*** | −0.1 (−1.5–1.3) | 0.924 |
| Inspiratory capacity, L | 1.8±0.6 | 1.7±0.6** | 1.9±0.7 | 1.8±0.7 | −0.0 (−0.2–0.1) | 0.449 |
| 6MWD, m | 461.1±124.2 | 458.7±124.9 | 2.6 (−4.1–9.4) | 0.447 | ||
| 6MWD, % pred | 73.1±20.7 | 72.8±20.7 | 0.37 (−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.