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Power Reserve at the Limit of Ramp‐incremental Exercise is Affected by Incrementation Rate
Author(s) -
Davies Matthew J,
Benson Alan P,
Birch Karen M,
Rossiter Harry B,
Ferguson Carrie
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.761.8
Subject(s) - cadence , cycling , power (physics) , mathematics , cardiology , zoology , physical therapy , medicine , physical medicine and rehabilitation , simulation , physics , computer science , biology , thermodynamics , geography , archaeology
The mechanisms that bring about task failure during exercise in which VO 2max is attained remain poorly understood. A fundamental question is whether maximum voluntary power declines to the point at which it no longer exceeds the requirements of the exercise task (i.e. no power reserve). We recently demonstrated that there was no power reserve at the limit of tolerance (LoT) of ramp‐incremental (RI) cycle ergometry, but that the central and peripheral contributions to performance fatigue (PF; i.e. the decline in maximal voluntary power) were widely heterogeneous amongst individuals. As the kinetics of central and peripheral limitations to power generation are likely to be influenced by the kinetics of the task, we aimed to determine the influence of ramp‐incrementation rate on the power reserve at the LoT. Using an instantaneous switch from cadence‐independent to isokinetic cycling, peak isokinetic power (P ISO , measured at 80 rpm for 6 s) was measured at baseline, and at the LoT of 3 maximal RI exercise tests (LoT P ISO ). Ramp‐incrementation rates of 10, 25 and 50 W·min −1 (RI‐10, RI‐25 and RI‐50, respectively) were performed in seven healthy participants (mean ± SD; 27 ± 6 yr; 174 ± 9 cm; 72 ± 10 kg; 5 m, 2 f). Breath‐by‐breath pulmonary gas exchange was measured throughout all protocols. Baseline P ISO was not different amongst the three RI protocols (732 ± 140, 739 ± 143, and 737 ± 144 W for RI‐10, RI‐25 and RI‐50, respectively; p > 0.05). VO 2max at LoT was within the normal day‐to‐day variation (< 7 %) across the three RI protocols (mean: 3.69 ± 0.74 L·min −1 ); however, flywheel power requirement at LoT increased with ramp rate (RI‐10: 270 ± 38; RI‐25: 318 ± 43; RI‐50: 354 ± 52 W; p < 0.05). PF was 313 ± 135, 346 ± 129, 380 ± 139 W for RI‐10, RI‐25 and RI‐50, respectively ( p > 0.05), with LoT P ISO decreasing to 54 ± 12 % of baseline P ISO . Thus at LoT, P ISO was greater than flywheel power in RI‐10 ( p < 0.05), but was not different from flywheel power in RI‐25 and RI‐50 ( p > 0.05). At the limit of ramp‐incremental exercise in which VO 2max is attained, the absence of a power reserve in RI‐25 and RI‐50 is consistent with the notion that exercise intolerance occurs when maximal evocable power equals the power required by the task. However, our data indicate that, while there was considerable fatigue during RI‐10, the decline in P ISO was insufficient to limit the exercise, thus other mechanisms were contributory to the exercise limitation in this slow ramp condition. This suggests that the mechanisms that precipitate task failure at VO 2max are plastic in young healthy subjects, and dependent on the kinetics of the task.