Operating lung volumes are affected by exercise mode but not trunk and hip angle during maximal exercise

Despite VO₂peak being, generally, greater while running compared to cycling, ventilation (VE) during maximal exercise is less while running compared to cycling. Differences in operating lung volumes (OLV) between maximal running and cycling could be one explanation for previously observed differences in V E and this could be due to differences in body position e.g., trunk/hip angle during exercise.

We asked whether OLV differed between maximal running and cycling and if this difference was due to trunk/hip angle during exercise.

Eighteen men performed three graded maximal exercise tests; one while running, one while cycling in the drop position (i.e., extreme hip flexion), and one while cycling upright (i.e., seated with thorax upright). Resting flow-volume characteristics were measured in each body position to be used during exercise. Tidal flow-volume loops were measured throughout the exercise.

V E during maximal running (148.8 ± 18.9 L min(-1)) tended to be lower than during cycling in the drop position (158.5 ± 24.7 L min(-1); p = 0.07) and in the upright position (158.5 ± 23.7 L min(-1); p = 0.06). End-inspiratory and end-expiratory lung volumes (EILV, EELV) were significantly larger during drop cycling compared to running (87.1 ± 4.1 and 35.8 ± 6.2 vs. 83.9 ± 6.0 and 33.0 ± 5.7% FVC), but only EILV was larger during upright cycling compared to running (88.2 ± 3.5% FVC). OLV and V E did not differ between cycling positions.

Since OLV are altered by exercise mode, but cycling position did not have a significant impact on OLV, we conclude that trunk/hip angle is likely not the primary factor determining OLV during maximal exercise.