Effects of two successive maximal exercise tests on pulmonary gas exchange in athletes

Pulmonary extravascular water accumulation may be involved in exercise-induced hypoxaemia in highly aerobically trained athletes. We hypothesized that if such an alteration were present in elite athletes performing a maximal exercise test, the impairment of gas exchange would be worse during a second exercise test following the first one. Eight male athletes performed two incremental exercise tests separated by a 30-min recovery period. Pulmonary gas exchange and ventilatory data were measured during exercise tests performed in normoxia. Arterial blood samples were drawn each minute during rest, exercise, and recovery. Pulmonary diffusing capacity for CO (D _LCO) was measured at rest, after the first (T1) and the second (T2) test. All the subjects underwent a spirometric test at rest and after T2. Maximal and recovery data for 0₂ uptake and minute ventilation were not statistically different between T1 and T2. Partial pressure of arterial 0₂ (P _aO₂) decreased during both tests but was lower during T2 for rest, 60 W, and 120 W (P < 0.02). Alveolar-arterial difference in partial pressure of 0₂ (P _A-a0₂) increased during both the tests but was significantly larger during T2 for rest, 60 W, and 120 W (P < 0.01). The P _aO₂ and P _A-aO₂ data at maximal exercise were not significantly different between T1 and T2. Compared to rest, P _A-aO₂ remained significantly larger during recovery for both T1 and T2 (P < 0.0001). The P _A-aO₂ during T2 recovery was larger than T1 recovery (P < 0.008). Spirometric data did not change. The D _LCO measurements after T1 and T2 were not significantly different from rest. These results showed an alteration of P _aO₂ and P _A-aO₂ during T1, which tended to be worse during and after T2; however, these data do not allow us to make a definitive statement as to the cause of the hypoxaemia. Our study confirmed that exhausting exercise caused hypoxaemia. It also demonstrated that the disturbance in pulmonary gas exchange persisted for at least 30 min following the end of the exercise period and became worse during submaximal intensities of the following incremental exercise test.     

Distribution of the myocardial tissuePO2 in the rat and the inhomogeneity of the coronary bed

The structural inhomogeneity of the myocardial capillary bed is simulated by microcirculatory units (MCU's) in a diffusion model. This simulation is based on MCU's in which the arrangement of the capillary ends (concurrent structure, partial and total countercurrent structure, helical structure) as well as the structure and supply parameters are varied. The variation of these parameters is based on own measurements of the intracapillary HbO₂ saturation as well as on the following parameters from the literature: frequency distribution of capillary distance and capillary radius, mean capillary length or capillary section length respectively, arterial and mean venousPO₂, mean coronary blood flow, mean O₂ consumption and diffusion conductivity. The analysis of O₂ supply of the normoxic rat heart shows that an O₂ diffusion shunt is obligatory except for MCU's with an extremely large capillary distance or with a concurrent capillary structure. Therefore the minimal tissuePO₂ lies at the level of the capillary venousPO₂ of a MCU. The maximum of the totalPO₂ frequency distribution in the normoxic rat myocardium lies at 25±5 mm Hg, i.e. above the mean venousPO₂ (20 mm Hg). TissuePO₂ values between 0 and 5 mm Hg amount to 0.5%, i.e. they are extremely rare. TissuePO₂ values of 0–1 mm Hg represent less than 0.2%.List of Symbols a arterial capillary end - a branching point of a capillary near the arterial capillary end (branching point of an anastomosis) - A maximal O₂-consumption - A(P) O₂-consumption dependent uponPO₂ - AVDO₂ arterio-venous difference - AVDO₂; AVDO_{2 c} ^(j) arterio-venous difference of a capillary - c _j weighting factor of the capillary distance - c _Hb hemoglobin concentration in the blood - d, d ^j capillary distance - mean capillary distance - i index for the different MCU's (i=1...8) - i.e. PO₂ intracapillaryPO₂ - j index for the parameters of an MCU with the capillary distanced ^(j) (j=1...7) - K diffusion conductivity - l capillary length - l _s capillary section length - MCU microcirculatory unit - P, P(x,y,z), PO₂ O₂ partial pressure - P _a arterialPO₂ - P _a; P_a ^(j) PO₂ at the branching pointa - P _i; P_v ^(j) venousPO₂ - mean venousPO₂ - P ₅₀ PO₂ at half maximal O₂ consumption - P _min,P _min ^(j) minimal tissuePO₂ - r _c, r_c ^(j) capillary radius - mean capillary radius - s(P) relative HbO₂ saturation (HbO₂ dissociation curve) - s ^–1 inverse function of the HbO₂ dissorciation curve - S _v, S_v ^(j) capillary venous HbO₂ saturation - mean venous HbO₂ saturation - v venous capillary end - V volume of the tissue fragment of a MCU - V _c, V_c ^(j) capillary supply volume - W _c, W_c ^(j) blood flow of the supply volume of a capillary (local blood flow) - mean blood flow - x,y,z cartesian coordinates of thePO₂ in a MCU - Bunsen's solubility coefficient - _c . _c ^(J) capilary blood flow - , ^(j) blood flow of an MCU - _i ^(j) (P) relative frequency distribution of thePO₂ in thei-th MCU - (P) relative frequency distribution of thePO₂ of all MCU's, total frequency distribution of the myocardial tissuePO₂ - Laplace operator Supported by the DFG     

Effect of endurance training on excessive CO2 expiration due to lactate production in exercise

Summary We attempted to determine the change in total excess volume of CO₂ Output (CO₂ excess) due to bicarbonate buffering of lactic acid produced in exercise due to endurance training for approximately 2 months and to assess the relationship between the changes of CO₂ excess and distance-running performance. Six male endurance runners, aged 19–22 years, were subjects. Maximal oxygen uptake (VO_2max), oxygen uptake (VO₂) at anaerobic threshold (AT), CO₂ excess and blood lactate concentration were measured during incremental exercise on a cycle ergometer and 12-min exhausting running performance (12-min ERP) was also measured on the track before and after endurance training. The absolute magnitudes in the improvement due to training for C02 excess per unit of body mass per unit of blood lactate accumulation (Ala^–) in exercise (CO₂ excess·mass^–1·la^–), 12-min ERP, VO₂ at AT (AT-VO₂) and VO_2max on average were 0.8 ml·kg^–1·l^–1·mmol^–1, 97.8m, 4.4 ml·kg^–1· min^–1 and 7.3 ml·kg^–1·min^–1, respectively. The percentage change in CO₂ excess·mass^–1·la^– (15.7%) was almost same as those of VO_2max (13.7%) and AT-VO₂ (13.2%). It was found to be a high correlation between the absolute amount of change in CO₂ excess·mass^–1·la^– and the absolute amount of change in AT-VO₂ (r=0.94, P<0.01). Furthermore, the absolute amount of change in C02 excess·mass^–1·la^–, as well as that in AT-VO₂ (r=0.92, P<0.01), was significantly related to the absolute amount of change in 12-min ERP (r=0.81, P<0.05). It was concluded that a large CO₂ excess·mass^–1·la^–1 of endurance runners could be an important factor for success in performance related to comparatively intense endurance exercise such as 3000–4000 m races.     

New acquisitions in the assessment of breath-by-breath alveolar gas transfer in humans

We summarise recent results obtained in testing some of the algorithms utilised for estimating breath-by-breath (BB) alveolar O₂ transfer (VO_2A) in humans. VO_2A is the difference of the O₂ volume transferred at the mouth minus the alveolar O₂ stores changes. These are given by the alveolar volume change at constant O₂ fraction (F _AiO₂ V _Ai) plus the O₂ alveolar fraction change at constant volume [V _Ai–1(F _Ai–F _Ai–1)O₂], where V _Ai–1 is the alveolar volume at the beginning of the breath i. All these quantities can be measured BB, with the exception of V _Ai–1, which is usually set equal to the subjects functional residual capacity (FRC) (Auchincloss algorithm, AU). Alternatively, the respiratory cycle can be defined as the time elapsing between two equal O₂ fractions in two subsequent breaths (Grønlund algorithm, GR). In this case, F _AiO₂=F _Ai–1O₂ and the term V _Ai–1(F _Ai–F _Ai–1)O₂ disappears. BB alveolar gas transfer was first determined at rest and during exercise at steady-state. AU and GR showed the same accuracy in estimating alveolar gas transfer; however GR turned out to be significantly more precise than AU. Secondly, the effects of using different V _Ai–1 values in estimating the time constant of alveolar O₂ uptake (O_2A) kinetics at the onset of 120 W step exercise were evaluated. O_2A was calculated by using GR and by using (in AU) V _Ai–1 values ranging from 0 to FRC +0.5 l. The time constant of the phase II kinetics (₂) of O_2A increased linearly, with V _Ai–1 ranging from 36.6 s for V _Ai–1=0 to 46.8 s for V _Ai–1=FRC+0.5 l, whereas ₂ amounted to 34.3 s with GR. We concluded that, when using AU in estimating O_2A during step exercise transitions, the ₂ value obtained depends on the assumed value of V _Ai–1.     

Influence of muscle fibre type and pedal rate on the V̇O2-work rate slope during ramp exercise

We hypothesised that the ratio between the increase in oxygen uptake and the increase in work rate (O₂/WR) during ramp cycle exercise would be significantly related to the percentage type II muscle fibres at work rates above the gas exchange threshold (GET) where type II fibres are presumed to be active. We further hypothesised that ramp exercise at higher pedal rates, which would be expected to increase the proportional contribution of type II fibres to the total power delivered, would increase the O₂/WR slope at work rates above the GET. Fourteen healthy subjects [four female; mean (SD): age 25 (3) years, body mass 74.3 (15.1) kg] performed a ramp exercise test to exhaustion (25 W min^–1) at a pedal rate of 75 rev min^–1, and consented to a muscle biopsy of the vastus lateralis. Eleven of the subjects also performed two further ramp tests at pedal rates of 35 and 115 rev min^–1. The O₂/WR slope for exercise <GET (S ₁) was significantly correlated with O₂ peak in ml kg^–1 min^–1 (r=0.60; P<0.05), whereas the O₂/WR slope for exercise >GET (S ₂) was significantly correlated to percentage type II fibres (r=0.54; P=0.05). The ratio between the O₂/WR slopes for exercise above and below the GET (S ₂/S ₁) was significantly greater at the pedal rate of 115 rev min^–1 [1.22 (0.09)] compared to pedal rates of 35 rev min^–1 [0.96 (0.02)] and 75 rev min^–1 [1.09 (0.05), (P<0.05)]. The greater increase in S ₂ relative to S ₁ in subjects (1) with a high percentage type II fibres, and (2) at a high pedal rate, suggests that a greater recruitment of type II fibres contributes in some manner to the xs O₂ observed during ramp exercise.     

Interpretation of gas-blood ratio inP O 2polarography

Summary The differences inP _{O 2}readings between gas and blood were studied with a Clark-type electrode in the range of 38.5 to 713 mm HgP _{O 2}.The tonometered blood samples were taken in two different ways. The results showed that the gas-blood ratior _b(equilibrating gasP _{O 2}reading/equilibrated bloodP _{O 2}reading) depended not only on the sampling method but also on theP _{O 2}range: it varied from 1.005 to 1.032 for aP _{O 2}of 96.5 mm Hg, and from 1.040 to 1.081 for aP _{O 2}of 713 mm Hg according to the sampling procedure.A theoretical analysis demonstrated that the variation ofr _bwith the bloodP _{O 2}can be attributed to the influence of the degree of oxygen saturation of the hemoglobin on theP _{O 2}gradient existing in the blood diffusion boundary layer adhering to the electrode membrane.This work was supported by grants from the High Authority of the European Coal and Steel Community and from the Fonds de la Recherche Scientifique Médicale, Belgium.     

Bio-energetic profile in 144 boys aged from 6 to 15 years with special reference to sexual maturation

Summary The effects of growth and pubertal development on bio-energetic characteristics were studied in boys aged 6–15 years (n = 144; transverse study). Maximal oxygen consumption (VO_2max, direct method), mechanical power at (VO_2max ( ), maximal anaerobic power (P_max; force-velocity test), mean power in 30-s sprint (P _30s; Wingate test) were evaluated and the ratios between P_max,P _30s and were calculated. Sexual maturation was determined using salivary testosterone as an objective indicator. Normalized for body massVO_2max remained constant from 6 to 15 years (49 ml· min^–1 · kg^–1, SD 6), whilst P_max andP _30s increased from 6–8 to 14–15 years, from 6.2 W · kg^–1, SD 1.1 to 10.8 W · kg^–1, SD 1.4 and from 4.7 W · kg^–1, SD 1.0 to 7.6 W · kg^–1, SD 1.0, respectively, (P < 0.001). The ratio P_max: was 1.7 SD 3.0 at 6–8 years and reached 2.8 SD 0.5 at 14–15 years and the ratioP _30s: changed similarly from 1.3 SD 0.3 to 1.9 SD 0.3. In contrast, the ratio P_max:P _30s remained unchanged (1.4 SD 0.2). Significant relationships (P < 0.001) were observed between P_max (W · kg^–1),P _30s (W · kg^–1), blood lactate concentrations after the Wingate test, and age, height, mass and salivary testosterone concentration. This indicates that growth and maturation have together an important role in the development of anaerobic metabolism.     

Analysis of alveolar PCO 2 control during the menstrual cycle

We attempted to analyze how is regulated during progesterone-induced hyperventilation in the luteal phase. A model for the CO₂ control loop was constructed, in which the function of the CO₂ exchange system was described as and that of the CO₂ sensing system as . Using this model, we estimated (1) the primary increase in produced by progesterone stimulation and (2) the effectiveness (E) of the loop to regulateP _{A CO 2}, defined as P _{A CO 2} (op)/P _{A CO 2} (cl) in which op signifies open-loop and cl, closed-loop. These respiratory variables were investigated throughout the menstrual cycle in 8 healthy women. During the luteal phase, on average, increased by 9.4% andP _{A CO 2},B andH decreased by 0.33 kPa (2.5 mm Hg), 0.47 kPa (3.5 mm Hg) and 13.6%, respectively, whileS and did not change significantly. (op) increased progressively on successive days of the luteal phase whileE remained unchanged at a value of 7.9, thus there was a progressive decrease inP _{A CO 2}. The decrease inH was considered to lessen P _{A CO 2} (op) and so reduce the final deviation ofP _{A CO 2} (P _{A CO 2} (cl)) during the luteal phase. The decrease inB was found to be dependent on (op).     

Diffusionsfehler und Eigenverbrauch der Pt-elektrode beipO2-Messungen im steady state

Zusammenfassung Im steady state beeinflussen Diffusionsfehler und Eigenverbrauch der Pt-Elektrode als systematische Fehler O₂-Partialdruckmessungen. Sie sind abhängig von den geometrischen Eigenschaften der Elektrode, den Diffusionseigenschaften der Membran sowie den Diffusions- und Konvektionseigenschaften des Meßmediums. Das Diffusionsfeld vor der Pt-Oberfläche und das dadurch bestimmte stationäre Meßsignal werden für gasförmige und nicht gasförmige Medien mit und ohne Konvektion berechnet. Daraus resultieren quantitative Aussagen über die systematischen Fehler. Speziell für Messungen in durchbluteten Geweben (z. B. Hirnrinde und Myokard) wird der Einfluß des Eigenverbrauchs von Pt-Elektroden auf den intracapillärenpO₂-Abfall in Durchblutungsrichtung und das intercapillärepO₂-Feld am Meßort der Elektrode ermittelt. Diese Berechnungen erfolgten mit Hilfe eines Digitalmodells.

---

Erklärung der Symbole A O₂-Verbrauch des Gewebes - Bunsenscher Löslichkeitskoeffizient des Mediums - _m Bunsenscher Löslichkeitskoeffizient der Membran - C ₁,C ₁,C ₂,C ₂,C ₃ Konstanten - D Diffusionskoeffizient des Mediums - DF, DF Diffusionsfehler bei einfacher und doppelter Membran - DGl Differentialgleichung - d Capillarabstand - d _h Dicke der hydrodynamischen Grenzschicht - d _m ,d _m Dicke der Membranen - , , , , , dimensionslose Parameter - exp Exponentialfunktion - F Faradaykonstante - grad Gradient - I _o stationäres Meßsignal in Medien ohne Konvektion - I stationäres Meßsignal in Gasen - I _o stationäres Meßsignal in Flüssigkeiten mit Konvektion - J _o nullte Bessel-Funktion - K Diffusionsleitfähigkeit des Mediums - KE, KE Konvektionseffekt bei einfacher und doppelter Membran - K _m ,K _m Diffusionsleitfähigkeit der Membranen - l Capillarlänge - l Capillarabschnitt - Viscosität des Mediums - p, pO₂,p(r), p(r,z) O₂-Partialdruck - p mittlerer Partialdruck - P _a O₂-Partialdruck am arteriellen Capillarende - p _c konstanter Partialdruck - P/r _o +d _m O₂-Partialdruck an der Grenze Membran/Medium - P _v O₂-Partialdruck am venösen Capillarende - P _g relativer O₂-Partialdruckabfall im Gewebe - P _v relativer O₂-Partialdruckabfall am venösen Capillarende - R Radius der ebenen kreisförmigen Elektrode - RB Randbedingung - RDF, RDF restlicher Diffusionsfehler einfacher und doppelter Membranen - r _o Radius der Elektrode mit halbkugelförmiger Pt-Oberfläche - r, z Zylinderkoordinaten - r _K Capillarradius - S Sättigungsabfall im Capillarblut ohne Elektrode - S Sättigungsabfall im Capillarblut mit Elektrode - u O₂-Konzentration - V Diffusionsgesamtfluß - V _K Diffusionsfluß aus einem Capillarabschnitt - v _r ,v _z Komponenten des Stromdichtevektors inr- bzw.z-Richtung (Zylinderkoordinaten) - mittlere Stromdichte - Stromdichtevektor des Flusses der O₂-Moleküle - v _c konstante Geschwindigkeit des bewegten Mediums - x, y, z Kartesische Koordinaten - Integrationsvariable - ² Laplace-Operator - partielle Ableitung nach der Zeit     

A new approach to rowing ergometry: establishing exercise intensity relative to maximum force output

Summary The present experiment evaluated a new approach to establish exercise intensity during hydraulic rowing ergometry. In contrast to the traditional approach where exercise intensity is augmented by systematically increasing workload, the new procedure increments the intensity of exercise while maintaining a constant percentage of maximum force output. Ten college females exercised on a hydraulic rower that allowed for control of rowing speed and resistance. The new method to establish work intensity was to row at a cadence of 30 c·min^–1 at a force output equal to 50% of maximum rowing force at each setting determined dynamically prior to testing. Two protocols were used for the maximum tests on the hydraulic rower. Row 1 was a 17-min, six-stage, incremental continuous row test performed at increasingly difficult settings from easy (setting 1; 603 N) to difficult (setting 6; 893 N). Row 2 was identical to row 1 until 15 min when resistance was reduced to setting 2 (658 N) for allout effort during the last 2 min. During this time, cadence declined from 30 c·min^–1 to 19.4 c·min^–1 at dial setting 6 and increased to 35.4 c·min^–1 at dial setting 2. Both rowing protocols were compared to maximal physiological responses during treadmill running (TM). Compared to TM, both rowing protocols elicited. significantly lower maximum oxygen uptake (VO_2max;P<0.05; row 1=29.0% and row 2=12.9%) and maximum heart rate (HR_max;P<0.05; row 1=12.9% and row 2=6.7%). Maximum ventilation (V _Emax) during row 1 was also lower by 30.4% than TM (P<0.05). In addition, row 1 was significantly lower (P<0.05) than row 2 forVO_2max (2.23 vs 2.60 l·min^–1), HR_max (165.5 vs 177.3 beats·min^–1), andV _Emax (62.7 vs 86.3 1·min^–1). These results demonstrate thatVO_2max, HR_max, andV _Emax are depressed when rowing exercise is performed at a high intensity relative to maximum strength. We conclude that the new approach to establish exercise intensity relative to maximum force production is more effective for eliciting near maximum values ofVO₂, HR, andV _E than the conventional method that increases the workload by set increments without consideration of maximal strength.     

Physiological responses to intermittent and continuous exercise at the same relative intensity in older men

We investigated the physiological responses in older men to continuous (CEx) and intermittent (IEx) exercise. Nine men [70.4 (1.2) years, O_2peak: 2.21 (0.20) l min^–1; mean (SE)] completed eight exercise tests (two CEx and six IEx) on an electronically braked cycle ergometer in random order. CEx and IEx were performed at 50% and 70% O_2peak. IEx was performed using 60sE:60sR, 30sE:30sR and 15sE:15sR exercise to rest ratios. The duration of exercise was adjusted so that the total amount of work completed was the same for each exercise test. Oxygen uptake (O₂), minute ventilation (_E) and heart rate (HR) were measured at the mid-point of each exercise test. Arterialised blood samples were obtained at rest and during exercise and analysed for pH and PCO₂. At the same relative intensity (50% or 70% O_2peak), IEx resulted in a significantly lower (P<0.01) O₂, _E and HR than CEx. There were no significant differences (P>0.05) in O₂, _E and HR measured at the mid point of the three exercise to rest ratios at 50% and 70% O_2peak. pH and PCO₂ during CEx and IEx at 50% O_2peak were not significantly different from rest. CEx performed at 70% O_2peak resulted in significant decreases (P<0.05) in pH and PCO₂. There was a significant decrease (P<0.05) in pH only during the 60sE:60sR IEx at 70% O_2peak. Changes in arterialised PCO₂ during the 60sE:60sR, 30sE:30sR and 15sE:15sR at both 50% and 70% O_2peak exercise tests were not significant. When exercising at the same percentage of O_2peak and with the total amount of work fixed, IEx results in significantly lower physiological responses than CEx in older men. All results are given as mean (SE).     

Quantitative continuous measurement of partial oxygen pressure on the skin of adults and new-born babies

Summary It is possible to perform continuous quantitativeP _{O 2} measurements on vasodilated skin by means of surface Pt electrodes according to Clark when the electrode is fixed to the skin with a synthetic plastic material and in situ calibration is performed. A new in situ calibration of theP _{O 2} electrode is described. At first the skinP _{O 2} increases with O₂ inspiration. After perfusion stop the skinP _{O 2} shows a linear decrease because of the skin respiration, down to aP _{O 2} at which hemoglobin liberates chemically bound O₂. As thisP _{O 2} value of hemoglobin is known it is possible to use it for calibrating the electrode. TheP _{O 2} of normal skin is about 0–7 Torr. After vasodilation obtained by rubbing with a nicotinic acid derivate (Finalgon^®, Anasco, Wiesbaden),P _{O 2} increases to a mean value of 38.1 (±8.1) Torr (n=77). Under these conditions, skinP _{O 2} reaches arterial values never in adults and rarely in new-born babies.Part of the results have been reported during the Workshop on Oxygen Transport in Tissue, 19–22 July, 1971, in Dortmund and at the 4. Deutsche Kongress für Perinatale Medizin, 4–6 Nov. 1971, in Berlin. The study was carried out with partial support from the German Research Council (DFG).     

Acute EPOC response in women to circuit training and treadmill exercise of matched oxygen consumption

The purpose of the study was to evaluate the effects of circuit training (CT) and treadmill exercise performed at matched rates of oxygen consumption and exercise duration on elevated post-exercise oxygen consumption (EPOC) in untrained women, while controlling for the menstrual cycle. Eight, untrained females (31.3±9.1 years; 2.04±0.26 l min^–1 estimated VO_2max; BMI=24.6±3.9 kg/m²) volunteered to participate in the study. Testing was performed during the early follicular phase for each subject to minimize hormonal variability between tests. Subjects performed two exercise sessions approximately 28 days apart. Resting, supine energy expenditure was measured for 30 min preceding exercise and for 1 h after completion of exercise. Respiratory gas exchange data were collected continuously during rest and exercise periods via indirect calorimetry. CT consisted of three sets of eight common resistance exercises. Pre-exercise and exercise oxygen consumption was not different between testing days (P>0.05). Thus, exercise conditions were appropriately matched. Analysis of EPOC data revealed that CT resulted in a significantly higher (p<0.05) oxygen uptake during the first 30 min of recovery (0.27±0.01 l min^–1 vs 0.23±0.01 l min^–1); though, at 60 min, treatment differences were not present. Mean VO₂ remained significantly higher (0.231±0.01 l min^–1) than pre-exercise measures (0.193±0.01 l min^–1) throughout the 60-min EPOC period (p<0.05). Heart rate, RPE, V_E and RER were all significantly greater during CT (p<0.05). When exercise VO₂ and exercise duration were matched, CT was associated with a greater metabolic disturbance and cost during the early phases of EPOC.     

Effects of training on plasma FFA during exercise in women

Summary The purpose of this study was to investigate the effects of training on plasma FFA concentrations in women during 60 min of work. All subjects (n=10) exercised at 55% of their initial VO_{2 max} for 60 min on a bicycle ergometer. Five subjects then participated in a training program, consisting of bicycling five days per week for four weeks while five control subjects remained inactive. Following the training or control period, all 10 subjects repeated the initial 1-h test at the same absolute work load. The training program resulted in a 14% increase in VO_{2 max} and a decreased resting HR (p<0.05). The submaximal exercise HR and R were also lower following training (p<0.05). Plasma FFA were significantly lower (p<0.05) during exercise in the experimental group following training. The average increase in plasma FFA during the 60 min bicycle test was 0.22 mol/l, from 0.48 mol/l at rest to 0.70 mol/l after 60 min of exercise prior to training. After training the same absolute work load resulted in an increased plasma FFA of only 0.10 mol/l from 0.29 to 0.39 mol/l. No significant changes due to training were observed for glycerol or lactate. The results suggest that the metabolic response of women is similar to men during exercise before and after training. Possible mechanisms for the decreased plasma FFA response after training are discussed.     

Effect of variations in blood hydrogen ion concentration on pulmonary gas exchange of artificially ventilated dogs

The effect of variation of blood hydrogen ion concentration on arterial and mixed venousP _{O 2},ideal alveolar-arterial O₂ pressure difference (P _AiO₂–P _aO₂),venous admixture (Q _s/Q _t), arterio-alveolar CO₂ pressure difference (a–A)D _{CO 2},physiological dead space to tidal volume ratio (V _D/V_T),cardiac output (Q _t) and mean pulmonary arterial pressure ( ) has been studied. Arterial and mixed venousP _{O 2}increased and (P _AiO₂–P _aO₂)decreased with increasing blood hydrogen ion concentration. No change in (Q _s/Q _t), (a–A)-D _{CO 2},V _D/V_T,Q _t and was observed.The effect of hydrogen ion concentration on arterial and mixed venousP _{O 2}and on (P _AiO₂–P _aO₂)is mainly due to a shift of the blood oxyhemoglobin dissociation curve (ODC), i.e. due to the Bohr effect. The upper part of the ODC is more flat in alkalosis (shift to the left) than in acidosis (shift to the right). Therefore the same end-capillary to arterial O₂ content difference results in a greater (P _AiO₂–P _aO₂)in alkalosis than in acidosis. Any factor influencing the slope of the upper part of the ODC is expected to affect the arterialP _{O 2}and the (P _AiO₂–P _aO₂)by this mechanism. Similarly any factor shifting the steep part of the ODC is expected to affect theP _{O 2}of the mixed venous blood.     

The VO2 response to exhaustive square wave exercise: influence of exercise intensity and mode

We investigated the oxygen uptake (O₂) response to exhaustive square wave exercise of approximately 2, 5 and 8 min duration in cycling and running. Nine males completed a ramp test and three square wave tests on a motorised treadmill and the same four tests on a cycle ergometer, throughout which gas exchange was assessed (Douglas bag method). The peak O₂ from the ramp test was higher for running than for cycling [mean (SD): 58.4 (2.8) vs. 55.9 (3.7) ml.kg^–1.min^–1; P=0.04]. However O_2max (defined as the highest O₂ achieved in any of the four tests) did not differ between running and cycling [60.0 (2.9) vs. 58.5 (3.3) ml.kg^–1.min^–1; P=0.15]. The peak O₂ was similar (P>0.1) for the 5 and 8 min square wave tests [98.5 (1.8) and 99.2 (2.3) %O_2max for running; 97.0 (4.2) and 97.5 (2.0) %O_2max for cycling] but lower (P<0.001) for the 2-min test [91.8 (2.5) and 89.9 (5.5) %O_2max for running and cycling respectively]. O₂ increased over the final two 30-s collection periods of the 2-min test for cycling [O₂=0.18 (0.15) l.min^–1; P<0.01] but not running [O₂=0.00 (0.09) l.min^–1; P=0.98]. We conclude that in the aerobically fit the peak O₂ for square wave running or cycling at an intensity severe enough to result in exhaustion in approximately 2 min is below O_2max. In running, O₂ plateaus at this sub-maximal rate.     

Effects of inositol hexaphosphate on the Bohr effect induced by CO2 and fixed acids in chicken hemoglobin

Bohr factors, = logP _{O 2}/ pH, were measured in chicken hemoglobin (Hb) solutions at various levels of O₂ saturation in the absence and the presence of inositol hexaphosphate (IHP). pH changes were induced either by changingP _{CO 2}at constant base excess near zero (CO₂ Bohr factor, {ie135-1}) or by addition of fixed acid or base at constantP _{CO 2}(fixed acid Bohr factor, {ie135-2}). In the presence of IHP in a concentration of about 1.2 mol per mol Hb tetramer the two Bohr factors did not differ, the mean value being –0.61 (pH range, 7.1 to 7.6), independent of O₂ saturation (S _{O 2}) between 10 and 90%. Removal of IHP significantly decreased {ie135-3} to –0.25) pH range, 7.0 to 7.6), independent ofS _{O 2}, whereas the reduction in {ie135-4} was much less pronounced. Thus {ie135-5}, which showed a decrease with increasingS _{O 2}, exceeded {ie135-6} at all levels ofS _{O 2}. The data show that chicken hemoglobin is capable of binding CO₂ as oxygen-linked carbamate. But, at about equimolar concentrations of IHP and the tetrameric hemoglobin, oxylabile carbamate formation is abolished. It is suggested that this interaction between CO₂ and the organic phosphate compound accounts for the lack of a difference between the two Bohr factors in avian whole blood (cf. Meyer et al., 1978) where inositol pentaphosphate is present at about the same concentration as tetrameric hemoglobin.     

Serum carbonic anhydrase III,an enzyme of type I muscle fibres,and the intensity of physical exercise

The effects of 30 min running with stepwise increasing intensity (exhaustive, energy demand approx. 50 100% ofVO_2max), 60 s supramaximal running (anaerobic, 125% ofVO_2max) and 40–60 min low-intensity running (acrobic, 40–60% ofVO_2max) on serum concentration of muscle-derived proteins were studied in 5 male and 5 female elite orienteerers. S-Carbonic anhydrase III (S-CA III) was used as a marker of protein leakage from type I (slow oxidative) muscle fibres and S-myoglobin (S-Mb) as a non-selective (type I+II) muscular marker. The fractional increase in S-CA III (S-Ca III) was 0.37±0.09 (mean±SEM,p<0.001), 0.10±0.05 (N. S.) and 0.46±0.09 (p<0.001) 1 h after exhaustive, anaerobic and aerobic exercise, respectively. The corresponding values for S-Mb were 1.45±0.36 (p<0.001), 0.39±0.13 (p<0.01) and 0.67±0.18 (p<0.001). The value for the S-CA III/S-Mb ratio was 0.68±0.03 after the acrobic exercise, but only 0.25–0.26 (p vs. aerobic exercise <0.001) after the two high-intensity forms of exercise. Since type I fibres of skeletal muscle are known to be responsible for power production during low-intensity exercise, whereas fibres of both type I and type II are active at higher intensities, the S-CA III/S-Mb ratio may depend on the recruitment profile of type I vs. type I+II fibres.     

APCO2 surface electrode working on the principle of electrical conductivity

APCO₂ electrode working on the principle of electrical conductivity is described. The calibration curve can be linearized according to the formula . This linearity has been tested in thePCO₂ range of 0.93–9.33 kPa (7–70 Torr). For the experiments electrodes are used which have conductivity values of about 50 nS and drifts of maximally 5%/h at aPCO₂ of 5.33 kPa (40 Torr). The response time (T ₉₀) is about 20 s. The temperature sensitivity is 2.4 nS/1 K between 298K–310K. The standard error of the measurements is =0.33 nS. With these electrodes tissuePCO₂ can be measured on the surface of various organs.     

Is the balance between skeletal muscular metabolic capacity and oxygen supply capacity the same in endurance trained and untrained subjects?

We attempted to test whether the balance between muscular metabolic capacity and oxygen supply capacity in endurance-trained athletes (ET) differs from that in a control group of normal physically active subjects by using exercises with different muscle masses. We compared maximal exercise in nine ET subjects [Maximal oxygen uptake (VO₂max) 64 ml kg⁻¹ min⁻¹ ± SD 4] and eight controls (VO₂max 46 ± 4 ml kg⁻¹ min⁻¹) during one-legged knee extensions (1-KE), two-legged knee extensions (2-KE) and bicycling. Maximal values for power output (P), VO₂max, concentration of blood lactate ([La⁻]), ventilation (VE), heart rate (HR), and arterial oxygen saturation of haemoglobin (SpO₂) were registered. P was 43 (2), 89 (3) and 298 (7) W (mean ± SE); and VO₂max: 1,387 (80), 2,234 (113) and 4,115 (150) ml min⁻¹) for controls in 1-KE, 2-KE and bicycling, respectively. The ET subjects achieved 126, 121 and 126% of the P of controls (p < 0.05) and 127, 124, and 117% of their VO₂max (p < 0.05). HR and [La⁻] were similar for both groups during all modes of exercise, while VE in ET was 147 and 114% of controls during 1-KE and bicycling, respectively. For mass-specific VO₂max (VO₂max divided by the calculated active muscle mass) during the different exercises, ET achieved 148, 141, and 150% of the controls’ values, respectively (p < 0.05). During bicycling, both groups achieved 37% of their mass-specific VO₂ during 1-KE. Finally we conclude that ET subjects have the same utilization of the muscular metabolic capacity during whole body exercise as active control subjects.