Influence of moderate smoking on physical fitness and local muscle oxygenation profile during incremental exercise

To reveal the influence of chronic moderate smoking on physical fitness and local muscle oxygenation profile, we compared the oxygen uptake (VO2), CO2 output, respiratory rate, minute ventilation and blood lactate accumulation between six moderate smokers and ten non-smokers during incremental exercise. In order to know the difference of the peripheral oxygen supply to the muscles between the two groups, oxygenation profiles based on the changes of oxygenated hemoglobin (O2Hb) in the right vastus lateralis muscles were observed using near-infrared spectroscopy (NIRS). The intensity of incremental exercise using a bicycle ergometer was from 10 W to 80% of the maximum heart rate (80% HR(max)) of each subject. There were no significant differences between the two groups in VO2 and work rate at the level of 2 mmol/ l lactate or 80%HR(max) (P < 0.05). However, as to the local muscle oxygenation profile during exercise, 5 out of the 6 smokers showed a decrease of O2Hb throughout the incremental exercise, but 8 out of the 10 non-smokers showed a gradual increase of O2Hb throughout the exercise. In conclusion, our results suggest that chronic moderate smoking might cause a change of local muscle oxygenation profile during incremental exercise, even if the smokers have shown no decrease in physical fitness.