Search PubMed⌕ Search

Biomedical subjects

P Mognoni

Publications and source records attributed to P Mognoni.

At least 37 records · Page 2Linked to original sources
PubMed1979

Equation of motion of a cyclist.

Tractional resistance (RT, N) was determined by towing two cyclists on a racing bike in "fully dropped" posture in calm air on a flat track at constant speed (5--16.5 m/s). RT increased with the air velocity (v, m/s): RT = 3.2 + 0.19 V2. The constant 3.2 N is interpreted as the rolling resistance and the term increasing with v2 as the air resistance. For a given posture this is a function of the body surface (SA, m2), the air temperature (T, degree K), and barometric pressure (PB, Torr). The mechanical power output (W, W) can then be described as a function of the air (v) and ground (s) speed: W = 4.5.10(-2) Ps + 4.1.10(-2) SA (PB/T)v2 s, where P is the overall weight in kg. With a mechanical efficiency of 0.25, the energy expenditure rate (VO2, ml/s) is given by: VO2 = 8.6.10(-3) Ps + 7.8.10(-3) SA (PB/T)v2 s (1 ml O2 = 20.9 J). As the decrease of VO2max with altitude is known from the literature, this last equation allows the calculation of the optimal altitude for top aerobic performance. The prediction derived from this equation is consistent with the present 1-h world record.

Air↗
PubMed1978

Oronasal breathing during exercise.

The shift from nasal to oronasal breathing (ONBS) has been observed on 73 subjects with two independent methods. A first group of 63 subjects exercising on a bicycle ergometer at increasing work load (98--196 W) has been observed. On 35 subjects the highest value of ventilation attained with nasal breathing was 40.2 +/- 9.41 . min-1 S.D. Ten subjects breathed through the mouth at all loads, while 5 never opened the mouth. On 13 subjects it was not possible to make reliable measurements. On a second group of 10 subjects utilizing a different techniques which did not need a face mask, the ventilation at which one changes the pattern of breathing was found to be 44.2 +/- 13.51 . min-1 S.D. On the same subjects nasal resistance did not show any correlation with ONBS. It is concluded that ONBS is not solely determined by nasal resistance, though an indirect effect due to hypoventilation and hence to changes in alveolar air composition cannot be ruled out. It is likely that ONBS is also influenced by psychological factors.

Adult↗
PubMed1976

Energy cost of speec skating and efficiency of work against air resistance.

The energy expenditure during speed ice skating (PB=650 mmHg; T=-5 degrees C) was measured on 13 athletes (speed range: 4-12 m/s) from VO2 and (for speeds greater than 10 m/s) from blood lactic acid concentration. The energy spent (O2 equivalents) per unit body wt and unit distance (Etot/V, ml/kg-min) increases with the speed (v, m/s): Etot/v=0.049 + 0.44 X 10(-3) V2. At 10 m/s, Vtot/v amounts then to 0.093 ml/kg-m: about half the value of running. The constant 0.049 ml/kg-m is interpreted as the energy spent against gravitational and inertial forces. The term 0.44 X 10(-3) v2 indicates the energy spent against the wind, the constant 0.44 X 10(-3) ml-s2-kg-1-m-3 being a measure of k/e, where k is the coefficient relating drag to v2, and e the efficiency of work against the wind. From a direct estimate of k in a wind tunnel, e was calculated as 0.11. In running, skating, and cycling k/e is similar (approximately 0.020 ml-s2-m-3 per m2 body area), hence at a given speed the energy spent against the wind is equal. On the contrary, the energy spent against other forces decreases in the above order: 0.19, 0.05, 0.018 ml-m-1 per kg body wt. This explains the different speeds attained in these exercises with the same power output.

Adult↗
PubMed1969

Contribution of the diaphragm and the other inspiratory muscles to different levels of tidal volume and static inspiratory effort in the rabbit.

1. The contribution of the diaphragm and that of the other inspiratory muscles at different levels of tidal volume and during static inspiratory efforts of various strength has been studied in supine rabbits by blocking phrenic conduction with an electrotonic current. The rabbits were lightly anaesthetized with urethane and pentobarbitone.2. The volume displaced by the extradiaphragmatic muscles (V(tEDM)) in vagotomized rabbits increases linearly with the tidal volume (V(t)), according to the function V(tEDM) = - 3.27 + 0.32 V(t). The relative contribution of extradiaphragmatic muscles (V(tEDM)/V(t) x 100) for resting ventilation is 12% and becomes ca. 25% for the maximum V(t) value attained during re-breathing.3. When the vagi are left intact, the V(tEDM) is always higher because of the compensatory hyperactivity of the extradiaphragmatic muscles due to Hering-Breuer reflexes during the phrenic block.4. The pressure exerted by the extradiaphragmatic muscles, during inspiratory efforts with closed airways, increases linearly with the strength of the effort, without any difference between intact and vagotomized rabbits. The relationship between the pressure exerted by the extradiaphragmatic muscles (P(EDM)) and the pressure exerted by all the inspiratory muscles (P) is expressed by the function P(EDM) = - 3.29 + 0.38P.5. These results indicate that the diaphragm is the main inspiratory muscle at all levels of inspiratory activity.

Action Potentials↗