Comparison of physiological responses and muscle activity during incremental and decremental cycling exercise

Objective: to investigate whether a cycling test based on decremental loads (DEC) could elicit higher V̇O2max values compared with an incremental test (INC).

Design: Nineteen well-trained individuals performed an INC and a DEC test on a single day, in randomized order.

Methods: During INC the load was increased by 20 W.min-1 until task failure. During DEC the load started at 20 W higher than the peak load achieved during INC (familiarization trial) and was progressively decreased. Gas exchange and EMG activity (n=11) from four lower limb muscles were monitored throughout the tests. Physiological and EMG data measured at V̇O2max were compared between the two protocols using paired t-tests.

Results: V̇O2max during the DEC was 3.0 (5.9) % higher than during INC (range 94 – 116 %; p = 0.01), in spite of a lower power output (-21 [20] W, p < 0.001) at V̇O2max. Pulmonary ventilation (p = 0.036) and breathing rate (p = 0.023) were also higher during DEC. EMG activity measured at V̇O2max was not different between tests, despite the lower output during DEC.

Conclusions: A decremental exercise test produces higher V̇O2max in cycling compared to an incremental test, which was accompanied by higher pulmonary ventilation and similar EMG activity. The additional O2 uptake during DEC might be related to extra work performed by the respiratory and the less oxidatively efficient leg muscles.