Browsing by Author "Whipp, Brian J."
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Item The contribution of "resting" body muscles to the slow component of pulmonary oxygen uptake during high-intensity cycling(Journal Sports Science & Medicine, 2012-12) Whipp, Brian J.; Ward, Susan A.; Özyener, Fadıl; Uludağ Üniversitesi/Tıp Fakültesi/Fizyoloji Anabilim Dalı.; 0000-0002-4606-6596; AAH-1641-2021; 6506242143Oxygen uptake (VO2) kinetics during moderate constant-workrate (WR) exercise (>lactate-threshold (theta(L))) are well described as exponential. Above theta(L), these kinetics are more complex, consequent to the development of a delayed slow component (VO(2)sc), whose aetiology remains controversial. To assess the extent of the contribution to the VO(2)sc from arm muscles involved in postural stability during cycling, six healthy subjects completed an incremental cycle-ergometer test to the tolerable limit for estimation of theta(L) and determination of peak VO2. They then completed two constant-WR tests at 90% of theta(L) and two at 80% of Delta (difference between theta(L) and VO2peak). Gas exchange variables were derived breath-by-breath. Local oxygenation profiles of the vastus lateralis and biceps brachii muscles were assessed by near-infrared spectroscopy, with maximal voluntary contractions (MVC) of the relevant muscles being performed post-exercise to provide a frame of reference for normalising the exercise-related oxygenation responses across subjects. Above supra-theta(L), VO2 rose in an exponential-like fashion ("phase 2), with a delayed VO(2)sc subsequently developing. This was accompanied by an increase in [reduced haemoglobin] relative to baseline (Delta[Hb]), which attained 79 +/- 13 % (mean, SD) of MVC maximum in vastus lateralis at end-exercise and 52 +/- 27 % in biceps brachii. Biceps brachii Delta[Hb] was significantly correlated with VO2 throughout the slow phase. In contrast, for sub-theta(L) exercise, VO2 rose exponentially to reach a steady state with a more modest increase in vastus lateralis Delta[Hb] (30 +/- 11 %); biceps brachii Delta[Hb] was minimally affected (8 +/- 2 %). That the intramuscular O-2 desaturation profile in biceps brachii was proportional to that for VO(2)sc during supra-theta(L) cycle ergometry is consistent with additional stabilizing arm work contributing to the VO(2)sc.Item Effects of exercise intensity on the parameters of V-O2 kinetics in humans(Wiley, 1998-09) Ward, Susan A.; Whipp, Brian J.; Özyener, Fadıl; Uludağ Üniversitesi/Tıp Fakültesi/Fizyoloji Anabilim Dalı.; 0000-0002-4606-6596; AAH-1641-2021Item Influence of exercise intensify on the on- and off-transient kinetics of pulmonary oxygen uptake in humans(Wiley, 2001-06) Rossiter, Harry; Ward, Susan Ann; Whipp, Brian J.; Özyener, Fadıl; Uludağ Üniversitesi/Tıp Fakültesi/Fizyoloji Anabilim Dalı.; 0000-0002-4606-6596; AAH-1641-2021The maximal oxygen uptake ((V) over dot (O2,peak)) during dynamic muscular exercise is commonly taken as a crucial determinant of the ability to sustain high-intensity exercise. Considerably less attention, however, has been given to the rate at which (V) over dot (O2), increases to attain this maximum (or to its submaximal requirement), and even less to the kinetic features of the response following exercise.Six, healthy, male volunteers (aged 22 to 58 years), each performed 13 exercise tests: initial ramp-incremental cycle ergometry to the limit of tolerance and subsequently, on different days, three bouts of square-wave exercise each at moderate, heavy, very heavy and severe intensities. Pulmonary gas exchange variables were determined breath by breath throughout exercise and recovery from the continuous monitoring of respired volumes (turbine) and gas concentrations (mass spectrometer). For moderate exercise, the (V) over dot O-2, kinetics were well described by a simple mono-exponential function, following a short cardiodynamic phase, with the on- and off-transients having similar time constants (tau (1)); i.e. tau (1,on) averaged 33 +/- 16 s (+/- S.D.) and tau (1,off) 29 +/- 6 s. 4. The on-transient (V) over dot (O2) kinetics were more complex for heavy exercise. The inclusion of a second slow and delayed exponential component provided an adequate description of the response; i.e. tau (1,on) = 32 +/- 17 s and tau (2,on) = 170 +/- 49 s. The off-transient (V) over dot (O2) kinetics, however, remained mono-exponential (tau (1,off) = 42 +/- 11 s). 5. For very heavy exercise, the on-transient (V) over dot (O2), kinetics were also well described by a double exponential function (tau (1,on) = 34 +/- 11 s and tau (2,on) = 163 +/- 46 s). However, a double exponential, with no delay, was required to characterise the off-transient kinetics (i.e. tau (1,off) = 33 +/- 5 s and tau (2,off) = 460 +/- 123 s). 6. At the highest intensity (severe), the on-transient Tie, kinetics reverted to a mono-exponential profile (tau (1,on) = 34 +/- 7 s), while the off-transient kinetics retained a two-component form (tau (1,off) = 35 +/- 11 s and tau (2,off) = 539 +/- 379 s). 7. We therefore conclude that the kinetics of (V) over dot (O2) during dynamic muscular exercise are strikingly influenced by the exercise intensity, both with respect to model order and to dynamic asymmetries between the on- and off-transient responses.Item Oxygen uptake kinetics during incremental- and decremental-ramp cycle ergometry(Journal Sport Science and Medicine, 2011-09) Rossiter, Harry B.; Ward, Susan A.; Whipp, Brian J.; Özyener, Fadil; Uludağ Üniversitesi/Tıp Fakültesi/Fizyoloji Anabilim Dalı.; 0000-0002-4606-6596; AAH-1641-2021; 6506242143The pulmonary oxygen uptake (VO2) response to incremental-ramp cycle ergometry typically demonstrates lagged-linear first-order kinetics with a slope of similar to 10-11 ml.min(-1).W-1, both above and below the lactate threshold (theta(L)), i.e. there is no discernible VO2 slow component (or "excess" VO2) above theta(L). We were interested in determining whether a reverse ramp profile would yield the same response dynamics. Ten healthy males performed a maximum incremental -ramp (15-30 W.min(-1), depending on fitness). On another day, the work rate (WR) was increased abruptly to the incremental maximum and then decremented at the same rate of 15-30 W. min(-1) (step-decremental ramp). Five subjects also performed a sub-maximal ramp-decremental test from 90% of theta(L). VO2 was determined breath-by-breath from continuous monitoring of respired volumes (turbine) and gas concentrations (mass spectrometer). The incremental-ramp VO2-WR slope was 10.3 +/- 0.7 ml.min(-1).W-1, whereas that of the descending limb of the decremental ramp was 14.2 +/- 1.1 ml.min(-1).W-1 (p < 0.005). The sub-maximal decremental-ramp slope, however, was only 9.8 +/- 0.9 ml.min(-1).W-1: not significantly different from that of the incremental-ramp. This suggests that the VO2 response in the supra-theta(L) domain of incremental-ramp exercise manifest not actual, but pseudo, first-order kinetics.Item The parameters characterizing the O2 deficit during progressive exercise in humans(Wiley, 2004-03-24) Rossiter, Harry B.; Paterson, Nicola D.; Paterson, Donald; Kowalchuk, John M.; Whipp, Brian J.; Özyener, Fadıl; Uludağ Üniversitesi/Tıp Fakültesi/Fizyoloji Anabilim Dalı; 0000-0002-4606-6596; AAH-1641-2021