Effect of hyperventilation and prior heavy exercise on O2 uptake and muscle deoxygenation kinetics during transitions to moderate exercise. 2010

Lisa M K Chin, and George J F Heigenhauser, and Donald H Paterson, and John M Kowalchuk
Canadian Centre for Activity and Aging, School of Kinesiology, The University of Western Ontario, Arthur and Sonia Labatt Health Sciences Building, Rm 411C, London, ON, N6A 5B9, Canada.

The effect of hyperventilation-induced hypocapnic alkalosis (HYPO) and prior heavy-intensity exercise (HVY) on pulmonary O(2) uptake (VO(2p)) kinetics were examined in young adults (n = 7) during moderate-intensity exercise (MOD). Subjects completed leg cycling exercise during (1) normal breathing (CON, P(ET)CO(2) approximately 40 mmHg) and (2) controlled hyperventilation (HYPO, P(ET)CO(2) approximately 20 mmHg) throughout the protocol, with each condition repeated on four occasions. The protocol consisted of two MOD transitions (MOD1, MOD2) to 80% estimated lactate threshold with MOD2 preceded by HVY (Delta50%); each transition lasted 6 min and was preceded by 20 W cycling. VO(2p) was measured breath-by-breath and concentration changes in oxy- and deoxy-hemoglobin/myoglobin (Delta[HHb]) of the vastus lateralis muscle were measured by near-infrared spectroscopy. Adjustment of VO(2p) and Delta[HHb] were modeled using a mono-exponential equation by non-linear regression. During MOD1, the phase 2 time constant (tau) for VO(2p)(tauVO(2p)) was greater (P < 0.05) in HYPO (45 +/- 24 s) than CON (28 +/- 17 s). During MOD2, tauVO(2p) was reduced (P < 0.05) in both conditions (HYPO: 24 +/- 7 s, CON: 20 +/- 8 s). The Delta[Hb(TOT)] and Delta[O(2)Hb] were greater (P < 0.05) prior to and throughout MOD2. The Delta[HHb] mean response time was similar in MOD1 and MOD2, and between conditions, however, the MOD1 Delta[HHb] amplitude was greater (P < 0.05) in HYPO compared to CON, with no differences between conditions in MOD2. These findings suggest that the speeding of VO(2p) kinetics after prior HVY in HYPO was related, in part, to an increase in microvascular perfusion.

UI MeSH Term Description Entries
D006985 Hyperventilation A pulmonary ventilation rate faster than is metabolically necessary for the exchange of gases. It is the result of an increased frequency of breathing, an increased tidal volume, or a combination of both. It causes an excess intake of oxygen and the blowing off of carbon dioxide. Hyperventilations
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008297 Male Males
D010100 Oxygen An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration. Dioxygen,Oxygen-16,Oxygen 16
D010101 Oxygen Consumption The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346) Consumption, Oxygen,Consumptions, Oxygen,Oxygen Consumptions
D012123 Pulmonary Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Respiratory Airflow,Ventilation Tests,Ventilation, Pulmonary,Expiratory Airflow,Airflow, Expiratory,Airflow, Respiratory,Test, Ventilation,Tests, Ventilation,Ventilation Test
D005082 Physical Exertion Expenditure of energy during PHYSICAL ACTIVITY. Intensity of exertion may be measured by rate of OXYGEN CONSUMPTION; HEAT produced, or HEART RATE. Perceived exertion, a psychological measure of exertion, is included. Physical Effort,Effort, Physical,Efforts, Physical,Exertion, Physical,Exertions, Physical,Physical Efforts,Physical Exertions
D006454 Hemoglobins The oxygen-carrying proteins of ERYTHROCYTES. They are found in all vertebrates and some invertebrates. The number of globin subunits in the hemoglobin quaternary structure differs between species. Structures range from monomeric to a variety of multimeric arrangements. Eryhem,Ferrous Hemoglobin,Hemoglobin,Hemoglobin, Ferrous
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000222 Adaptation, Physiological The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT. Adaptation, Physiologic,Adaptations, Physiologic,Adaptations, Physiological,Adaptive Plasticity,Phenotypic Plasticity,Physiological Adaptation,Physiologic Adaptation,Physiologic Adaptations,Physiological Adaptations,Plasticity, Adaptive,Plasticity, Phenotypic

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