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Biomedical subjects

P Cerretelli

Publications and source records attributed to P Cerretelli.

At least 127 records · Page 7Linked to original sources
PubMed1979

Effects of specific muscle training on VO2 on-response and early blood lactate.

The relationship between half time of the O2 uptake on-response (t1/2 VO2on, seconds) and early blood lactate accumulation (delta Lab, mmol.1(-1) at the onset of submaximal arm and/or leg exercise was the object of a cross-sectional study of sedentary subjects (S,n = 3), and kayakers (K, n = 8), and of a longitudinal study on 11 untrained subjects of specific arm vs. leg training. In supine arm cranking (W = 125 watts) S had an average t1/2 VO2on of 82 s and a delta Aab of 9.2 mmol.1(-1) compared to 47 +/- 7 s and 4 +/- 1.4 mmol.1(-1), respectively, for K. In longitudinal trainees shorter t1/2 VO2on was accompanied by lower Lab for the trained limbs. Specific limb conditioning in swimmers and runners resulted in shorter t1/2 VO2on. A linear relationship was observed between delta Lab and t1/2 VO2on having an intercept on the time axis at congruent to 20 s and a slope proportional to muscle mass. Trained muscles were grouped closest to the intercept indicating local acceleration of the rate of O2 transfer approaching the t1/2 VO2on for isolated perfused muscle at the onset of work. Since t1/2 VO2on, we conclude that factors distal to the capillary are specifically involved in the local training response.

Adenosine Triphosphate↗
PubMed1978

Energetics of anaerobic glycolysis in dog gastrocnemius.

Thermally isolated gastrocnemii were stimulated to exhaustion, by rhythmic isotonic (70 N) tetanic contractions, during complete occlusion of blood flow. Enthalpy change (h = work + heat) and work output (w) (kJ/kg) were obtained from records of deep muscle temperature and shortening. The lactate produced (LA, mol/kg) was measured in the outflow after reestablishement of blood flow. The following relationships were obtained: h = 76LA + 1.2, and w = 19.8LA + 0.30. As the energy liberated at exhaustion by alactic energy sources (approximately P and O2 stores) is constant, deltah/deltaLA = 76 (+/- 10.5; S.E.) kJ/mol is the enthalpy change for lactate formation (delta HLA). The neutralization heat was estimated on muscle homogenates at 12kJ/mol, leaving approximately 64 kJ/MOL for deltaH of LA formation proper. The mechanical efficiencies of work related to LA formation (ELA) and of that not related to LA formation (EnonLA) were practically identical (0.25). From these values and from deltaHLA, the enthalpy change of approximately P splitting was estimated in the range of 52--62kJ/mol, depending on the value of the ratio delta approximately P/deltaLA assumed in the calculation.

Adenosine Triphosphate↗
PubMed1977

Oxygen uptake transients at the onset and offset of arm and leg work.

The halftimes (t1/2) of the VO2 on-and off-responses have been determined on 4 moderately active subjects (1) in arm cranking (VO2 congruent to 1 1/min). (2) in leg pedaling at 4 graded submaximal (VO2 congruent to 0.8 to 2.51/min) work loads, and (3) when superimposing arm cranking on preexisting leg pedaling, both in the supine and in the upright position. In supine experiments the mean t1/2 of the VO2 on-response was longer for arm cranking than for leg pedaling (64 vs 44-49 sec) at equal VO2; however, at the same percentage of arm and leg VO2 max the respective t1/2 were similar. In sitting experiments all t1/2 of the VO2 on-response were shorter than when supine, but the t1/2 for the arms were still slightly longer than those for the legs. When arm cranking was superimposed on preexisting leg pedaling, the t1/4 for arms was reduced both in supine (from 64 to 35-38 sec) and in the sitting position (from 44 to 40 sec). The halftime of the VO2 off-response were much shorter (20-32 sec) than those of the on-response and similar in all experiments. In all conditions the O2 deficits at work onset were considerably larger than the fast component of the corresponding O2 debts during the first minutes of recovery. The difference was totally accounted for by anaerobic glycolysis occurring early during the VO2 on-response, particularly in arm exercise. It is concluded that at submaximal work loads the O2 deficit is accounted for the fast component of the O2 debt plus the O2 equivalent of the early lactate production.

Adult↗
PubMed1976

Pulmonary O2 diffusing capacity at exercise by a modified rebreathing method.

The rebreathing technique for the measurement of the pulmonary O2 diffusing capacity, DO2, previously developed for resting conditions [Cerretelli et al., J. appl. Physiol. 37, 526-532 (1974)] has been modified for application to exercise and simplified to one rebreathing maneuver only. The changes consist: 1) in administering in the course of a normoxic exercise a priming breath of an O2 free mixture just before the onset of rebreathing in order to achieve rapidly the appropriate starting PO2 values on the linear part of the O2 dissociation curve as required by the method; 2) in calculating mixed venous blood O2 tension by extrapolation of the alveolar to mixed venous blood PO2 equilibration curve, instead of determining it separately. While the mean DO2 value of 21 measurements on 5 subjects at rest was 30 ml-min-1 - Torr-1 +/- 3 (S.E.), in 2 subjects exercising on a bicycle ergometer, DO2 was found to increase from a resting value of about 32 ml- min-1 - Torr-1 to 107 ml - min-1 - Torr-1 for an eightfold increase of O2 uptake. The validity and the applicability of the method are critically discussed.

Humans↗
PubMed1976

Limiting factors to oxygen transport on Mount Everest.

The effect of a sudden increase of the inspired oxygen tension on the maximal aerobic performance was studied on 23 subjects acclimated to high altitude (5,350-8,848 m above sea level) in the course of a 4-mo expedition to Mt. Everest. Inhalation of 100% O2 at 390 mmHg or a rapid descent (20 min) by helicopter to 2,850 m (Pio2 = 117 mmHg) raised maximal oxygen consumption (Vo2 max) from an average 0.7 of the control sea-level value, respectively, to 0.92 and 0.97. The failure of acclimated subjects to increase markedly or even to resume the preexisting sea-level Vo2mxa while breathing O2 in the presence of a 40% increase of blood Hb concentration and of a limited reduction of maximal cardiac output (Qmax), is attributed to changes in the peripheral circulation. These may consist of a) a hindrance of O2 diffusion due to erythrocytes packing secondary to increased hematocrit (Hct up to 70%); b) a bypass of arterial blood from the high-resistance working areas of the body aimed at reducing the load on the heart caused by increased blood viscosity. A 11.6% increase above normal controls of Hb concentration still found in 13 subjects 25 days after leaving altitude does not increase significantly maximum O2 consumption.

Acclimatization↗
PubMed1976

Energetics of isometric exercise in man.

In isometric contractions of the plantar flexors (5-40% of maximal tension, Tmax), VO2 is linearly related to the force exerted, averaging 2 ml/min-kg of tension. At tension levels above 5% Tmax the lactic acid contribution to the overall energy demand is constant at about 20%. Therefore, up to at least 40% Tmax,-muscle blood flow is not totally occluded, though it is impaired even at low force levels. Below 5% Tmax no lactic acid (LA) accumulates in blood. The energy required for the development of the tension is linearly related to the force exerted up to 33% Tmax, thereafter increasing disproportionately. In the transition from rest to static contractions of the plantar and forearm flexors (30 and 40% Tmax, respectively) VO2 increases initially to 200% of the controls, leveling off later at 150%. During recovery, VO2 increases up to 200% of the initial resting level, due to the payment of a large O2 debt, decreasing then with a t 1/2 of about 30 s. The glycolytic component is relatively more important in isometric contractions of the forearm than of the plantar flexors. No LA accumulates in static contractions of the plantar flexors of 5-10 s duration interrupted by equal pauses.

Adult↗
PubMed1975

Anaerobic recovery in man.

The lactic acid (L.A.) concentration in blood after a 20 sec supramaximal exercise (2.5 times VO2max) has been measured in 4 subjects in the following experimental conditions: a) during the resting period following the supramaximal exercise (rest recovery) and b) during a 3 min exercise at VO2max immediately following the supramaximal effort (exercise recovery). The L.A. concentration in blood has been found to be consistently higher (on the average by 16.9 mg%) in case (b). Since in such condition it may be reasonably assumed that the oxygen taken up by the subject is completely utilized for the exercise, the increase of blood lactate is considered evidence for the occurrence of anaerobic recovery, i.e. of a partial re-synthesis of the high energy phosphate stores of the muscle (GP = ATP + PC) depleted during the supramaximal effort, at the expense of anaerobic glycolysis. From the increase in blood L.A. concentration during the anaerobic recovery period, the amount of L.A. produced has been estimated together with the amount of GP resynthesized. The latter corresponds to 4 to 7 mMoles/kg of muscle, i.e. to about 25% of the average GP concentration in resting human muscle. The finalistic implication of this mechanism is the prompt restoration of the potential maximal power of the muscle even in the absence of O2.

Adenosine Triphosphate↗