Fig 4. Visual representation of measures related to muscle work assessed during the study.

Data are presented as average and standard deviation. Panel a) peak work rate (WRpeak); b) mechanical efficiency (ΔVO₂/ΔWR). The Airflow obstruction group is presented by dots and a black line, the smoking control group is presented by squares and a dark grey line and the never smoking control group is presented by triangles and a light grey line.