Prior exercise speeds pulmonary O2 uptake kinetics by increases in both local muscle O2 availability and O2 utilization (original) (raw)
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Journal of applied physiology (Bethesda, Md. : 1985), 2002
We hypothesized that the elevated primary O(2) uptake (VO(2)) amplitude during the second of two bouts of heavy cycle exercise would be accompanied by an increase in the integrated electromyogram (iEMG) measured from three leg muscles (gluteus maximus, vastus lateralis, and vastus medialis). Eight healthy men performed two 6-min bouts of heavy leg cycling (at 70% of the difference between the lactate threshold and peak VO(2)) separated by 12 min of recovery. The iEMG was measured throughout each exercise bout. The amplitude of the primary VO(2) response was increased after prior heavy leg exercise (from mean +/- SE 2.11 +/- 0.12 to 2.44 +/- 0.10 l/min, P < 0.05) with no change in the time constant of the primary response (from 21.7 +/- 2.3 to 25.2 +/- 3.3 s), and the amplitude of the VO(2) slow component was reduced (from 0.79 +/- 0.08 to 0.40 +/- 0.08 l/min, P < 0.05). The elevated primary VO(2) amplitude after leg cycling was accompanied by a 19% increase in the averaged iEM...
Journal of Applied Physiology, 2011
The relationship between the adjustment of muscle deoxygenation (Δ[HHb]) and phase II VO2p during moderate-intensity exercise was examined before (Mod 1) and after (Mod 2) a bout of heavy-intensity “priming” exercise. Moderate intensity VO2p and Δ[HHb] kinetics were determined in 18 young males (26 ± 3 yr). VO2p was measured breath-by-breath. Changes in Δ[HHb] of the vastus lateralis muscle were measured by near-infrared spectroscopy. VO2p and Δ[HHb] response profiles were fit using a monoexponential model, and scaled to a relative % of the response (0–100%). The Δ[HHb]/V̇o2 ratio for each individual (reflecting the local matching of O2 delivery to O2 utilization) was calculated as the average Δ[HHb]/V̇o2 response from 20 s to 120 s during the exercise on-transient. Phase II τVO2p was reduced in Mod 2 compared with Mod 1 ( P < 0.05). The effective τ′Δ[HHb] remained the same in Mod 1 and Mod 2 ( P > 0.05). During Mod 1, there was an “overshoot” in the Δ[HHb]/V̇o2 ratio (1.08; P...
VO(2) kinetics and the O(2) deficit in heavy exercise
Journal of applied physiology (Bethesda, Md. : 1985), 2000
The purpose of this study was to examine a new method for calculating the O(2) deficit that considered the O(2) uptake (VO(2)) kinetics during exercise as two separate phases in light of previous research in which it was shown that the traditional O(2) deficit calculation overestimated the recovery O(2) consumption (ROC). Eight subjects completed exercise transitions between unloaded cycling and 25% (heavy, H) or 50% (very heavy, VH) of the difference between the lactic acid threshold (LAT) and peak VO(2) for 8 min. The O(2) deficit, calculated in the traditional manner, was significantly greater than the measured ROC for both above-LAT exercises: 4.03 +/- 1.01 vs. 2.63 +/- 0.80 (SD) liters for VH and 2.36 +/- 0.91 vs. 1.74 +/- 0.63 liters for H for the O(2) deficit vs. ROC (P < 0.05). When the kinetics were viewed as two separate components with independent onsets, the calculated O(2) deficit (2.89 +/- 0.79 and 1.71 +/- 0.70 liters for VH and H, respectively) was not different f...
Dynamics of skeletal muscle oxygenation during sequential bouts of moderate exercise
Experimental Physiology, 2005
In rat muscle, faster dynamics of microvascular P O 2 (approximately blood flow (Q m ) to O 2 uptake (V O 2 ) ratio) after prior contractions that did not alter blood [lactate] have been considered to be a consequence of fasterV O 2 kinetics. However, in humans, prior exercise below the lactate threshold does not affect the pulmonaryV O 2 kinetics. To clarify this apparent discrepancy, we examined the effects of prior moderate exercise on the kinetics of muscle oxygenation (deoxyhaemoglobin, [HHb] αV O 2 m /Q m ) and pulmonaryV O 2 (V O 2 p ) in humans. Eight subjects performed two bouts (6 min each) of moderate-intensity cycling separated by 6 min of baseline pedalling. Muscle (vastus lateralis) oxygenation was evaluated by near-infrared spectroscopy anḋ V O 2 p was measured breath-by-breath. The time constant (τ ) of the primary component ofV O 2 p was not significantly affected by prior exercise (21.5 ± 9.2 versus 25.6 ± 9.7 s; Bout 1 versus 2, P = 0.49). The time delay (TD) of [HHb] decreased (11.6 ± 2.6 versus 7.7 ± 1.5 s; Bout 1 versus 2, P < 0.05) and τ [HHb] increased (7.0 ± 3.5 versus 10.2 ± 4.6 s; Bout 1 versus 2, P < 0.05), while the mean response time (TD + τ ) did not change (18.6 ± 2.7 versus 17.9 ± 3.9 s) after prior moderate exercise. Thus, prior moderate exercise resulted in shorter onset and slower rate of increase in [HHb] during subsequent exercise. These data suggest that prior exercise altered the dynamic interaction betweenV O 2 m andQ m following the onset of exercise.
A detailed comparison of oxygen uptake kinetics at a range of exercise intensities
Motriz: Revista de Educação Física, 2019
The aim of this study was to comprehensively examine oxygen uptake (V O 2) kinetics during cycling through mathematical modeling of the breath-by-breath gas exchange responses across eight conditions of unloaded cycling to moderate to high-intensity exercise. Methods: Following determination of GET and V O 2peak , eight participants (age: 24±8y; height: 1.78±0.09m; mass: 76.5±10.1kg; V O 2peak : 3.89±0.72 L. min-1) completed a series of square-wave rest-to-exercise transitions at;-20%∆ (GET minus 20% of the difference in V O 2 between that at GET and VO 2peak),-10%∆, GET, 10%∆, 20%∆, 30%∆, 40%∆, and 50%∆. The V O 2 kinetic response was modelled using mono-and bi-exponential non-linear regression techniques. The difference in the standard error of the estimates (SEE) for the mono-and bi-exponential models, and the slope of V O 2 vs time (for the final minute of exercise) were analysed using paired and one-sample t-tests, respectively. Results: The bi-exponential model SEE was lower than the monoexponential model across all exercise intensities (p<0.05), indicating a better model fit. Steady-state V O 2 was achieved across all exercise intensities (all V O 2 vs. time slopes; p>0.05). The modelled slow component time constants, typical of literature reported values, indicated that the V O 2 kinetic response would not be completed during the duration of the exercise. Conclusion: It was shown that the addition of the more complex bi-exponential model resulted in a better model fit across all intensities (notably including sub-GET intensities). The slow component phase was incomplete in all cases, even when the investigation of slopes indicated that a steady state had been achieved.
Journal of Applied Physiology, 2005
The effect of prior heavy-intensity warm-up exercise on subsequent moderate-intensity phase 2 pulmonary O2 uptake kinetics (τV̇o2) was examined in young adults exhibiting relatively fast (FK; τV̇o2 < 30 s; n = 6) and slow (SK; τV̇o2 > 30 s; n = 6) V̇o2 kinetics in moderate-intensity exercise without prior warm up. Subjects performed four repetitions of a moderate (Mod1)-heavy-moderate (Mod2) protocol on a cycle ergometer with work rates corresponding to 80% estimated lactate threshold (moderate intensity) and 50% difference between lactate threshold and peak V̇o2 (heavy intensity); each transition lasted 6 min, and each was preceded by 6 min of cycling at 20 W. V̇o2 and heart rate (HR) were measured breath-by-breath and beat-by-beat, respectively; concentration changes of muscle deoxyhemoglobin (HHb), oxyhemoglobin, and total hemoglobin were measured by near-infrared spectroscopy (Hamamatsu NIRO 300). τV̇o2 was lower ( P < 0.05) in Mod2 than in Mod1 in both FK (20 ± 5 s vs....
Medicine & Science in Sports & Exercise, 1998
NT. Temporal changes in blood lactate (r=0.40) and ventilation (r=0.72) were significantly correlated with the changes for SC over the 6 wk training period (p<0.05). In conclusion, training at supra-LT and sub-LT intensities produces similar improvement in VO 2 and power output at peak exercise and in the LT, when total work output is held constant. However, training at supra-LT intensity promotes larger and faster adaptations in the SC than training at the sub-LT levels.