Purpose:
The aim of the study was to establish the respiratory response to unloaded cycling at different cadences.

Methods:
Eleven healthy participants performed a maximal graded exercise test on a cycle ergometer to assess aerobic fitness (maximal oxygen consumption: 46.27 ± 5.41 ml • min^–1 • kg^–1) and eight 10-min unloaded pedaling (0 W) bouts at a constant cadence (from 40 to 110 rpm). Respiratory data were measured continuously during each effort and then averaged over 30 s. Blood samples were collected before and 2 min after each effort to monitor changes in acid–base balance.

Results:
The efforts were performed at an intensity of 16.5–37.5% VO_2peak. Respiratory response was not differentiated in cadences of 40, 50, 60 rpm. From 70 rpm, an increase in cadence was significantly associated with increased minute ventilation (F = 168.11, p < 0.000) and oxygen consumption (F = 214.86 p < 0.000) and, from 80 rpm, respiratory frequency (F = 16.06, p < 0.001) and tidal volume (F = 54.67, p < 0.000). No significant changes in acid-base balance were observed as a result of difference cadences.

Conclusions:
Unloaded cycling at a cadence of 70 rpm or above has a significant effect on respiratory function and may be associated with the involvement of large muscle ergoreceptors (mechanoreceptors) stimulated by the frequency of muscle contractions.