Limitations to oxygen transport and utilization during sprint exercise in humans: evidence for a functional reserve in muscle O₂ diffusing capacity

Abstract

Key pointsr Severe acute hypoxia reduces sprint performance. r MuscleV O 2 during sprint exercise in normoxia is not limited by O 2 delivery, O 2 offloading from haemoglobin or structure-dependent diffusion constraints in the skeletal muscle of young healthy men.r A large functional reserve in muscle O 2 diffusing capacity exists and remains available at exhaustion during exercise in normoxia; this functional reserve is recruited during exercise in hypoxia.r During whole-body incremental exercise to exhaustion in severe hypoxia, legV O 2 is primarily dependent on convective O 2 delivery and less limited by diffusion constraints than previously thought.r The kinetics of O 2 offloading from haemoglobin does not limitV O 2 peak in hypoxia. r Our results indicate that the limitation toV O 2 during short sprints resides in mechanisms regulating mitochondrial respiration.Abstract To determine the contribution of convective and diffusive limitations toV O 2 peak during exercise in humans, oxygen transport and haemodynamics were measured in 11 men (22 ± 2 years) during incremental (IE) and 30 s all-out cycling sprints (Wingate test, WgT), in normoxia (Nx, P IO 2 : 143 mmHg) and hypoxia (Hyp, P IO 2 : 73 mmHg). Carboxyhaemoglobin (COHb) was increased to 6-7% before both WgTs to left-shift the oxyhaemoglobin dissociation curve. Leġ V O 2 was measured by the Fick method and leg blood flow (BF) with thermodilution, and muscle O 2 diffusing capacity (D MO 2 ) was calculated. In the WgT mean power output, leg BF, leg O 2 delivery and legV O 2 were 7, 5, 28 and 23% lower in Hyp than Nx (P < 0.05); however, peak WgT D MO 2 was higher in Hyp (51.5 ± 9.7) than Nx (20.5 ± 3.0 ml min −1 mmHg −1 , P < 0.05). Despite a similar P aO 2 (33.3 ± 2.4 and 34.1 ± 3.3 mmHg), mean capillary P O 2 (16.7 ± 1.2 and 17.1 ± 1.6 mmHg), and peak perfusion during IE and WgT in Hyp, D MO 2 and legV O 2 were 12 and 14% higher, respectively, during WgT than IE in Hyp (both P < 0.05). D MO 2 was insensitive to COHb (COHb: 0.7 vs. 7%, in IE Hyp and WgT Hyp). At exhaustion, the Y equilibration index was well above 1.0 in both conditions, reflecting greater convective than diffusive limitation to the O 2 transfer in both Nx and Hyp. In conclusion, muscleV O 2 during sprint exercise is not limited by O 2 delivery, O 2 offloading from haemoglobin or structure-dependent diffusion constraints in

A new equation to estimate temperature‐corrected PaCO2 from PETCO2 during exercise in normoxia and hypoxia

“…I detailed description of the experimental procedures can be found elsewhere (Calbet et al., ; Morales‐Alamo et al., ). Both femoral veins and one femoral artery were catheterized under local anesthesia (2% lidocaine), as previously reported (Calbet et al., ).…”

“…A detailed description of the exercise protocol can be found elsewhere (Losa‐Reyna et al., ; Calbet et al., ; Morales‐Alamo et al., ). After catheterization, subjects were assigned randomly to either an incremental exercise test (Lode Excalibur Sport 925900, Groningen, the Netherlands) until volitional exhaustion in normoxia (P I O 2 : ∼143 mmHg), starting at 80 W with load increments of 30 W every 2 min or in hypoxia (P I O 2 : ∼73 mmHg, Altitrainer200, SMTEC, Nyon, Switzerland), starting at 60 W with load increments of 20 W every 2 min until exhaustion (Exh1).…”

Efectos de un dispositivo de restricción ventilatoria nasal sobre la ventilación pulmonar e intercambio gaseoso durante el ejercicio en personas sanas

“…Hence, FB requires deeper, slower and more O 2 extraction breaths per breath, thereby causing more effective breathing pattern. Moreover, it has been recently shown that there is a large functional reserve in the muscles at the end of an incremental exercise, regardless of the inspiratory O 2 pressure, since it seems that VO 2 uptake is primarily dependent on convective O 2 delivery and less limited by diffusion constraints (39,40).…”

Restructuring of Skeletal Muscle, Lung and Heart Tissues of Rats Under Hypoxia Training

“…Однією з основних характеристик ГН є обмежена дифузія кисню в тканинах, зокрема й у м'язовій тканині, під час його транспорту з судин мікроциркуля-торного русла до мітохондрій. Для зменшення впливу цього фактора та підвищення пра-цездатності завдяки розширенню функціо-нальних можливостей ФСД, необхідною (а часто й достатньою) умовою може виступати зростання капіляризації тканини, причому не тільки м'язової, а й тканин тих органів, що задіяні у адекватному киснезабезпечен-ні організму, та/або активація морфогенезу мітохондрій [5].…”