Biomedical subjects

P Zamparo

Publications and source records attributed to P Zamparo.

32 records · Page 2Linked to original sources

PubMed1997

Quantitative evaluation of the Myotatic Reflex in Hemiplegic and Paraplegic patients.

The aim of this study was the quantitative evaluation of the myotatic reflex in a group of 11 subjects affected by spastic paresis of the lower limbs (8 hemiplegic and 3 paraplegic patients) and, for comparison, in a group of 7 healthy subjects. The parameters taken into account were the gain of the reflex and the time delay between the input and the mechanical output. The gain was calculated as the ratio between: i) the peak value of the input force (FPH) measured by means of an instrumented hammer with which the patellar tendon was hit; and ii) the peak value of the corresponding reflex force of the quadriceps femoris (FPQ) measured by means of a load cell connected to the subject's ankle. The gain of the reflex (FPQ/FPH) was found to be 1.9 to 2.4 times larger in patients as compared to control subjects and, among the patients to be twice at low, as compared to high, levels of stimulation. Among the hemiplegic patients, significant differences were found in the time delay of the response between the affected and unaffected limbs. Since both the intensity of the reflex and its gain were found to depend on the mechanical energy input, both parameters must be taken in to account if a diagnosis of spasticity has to be made.

Journal Article↗

PubMed1996

Effect of the underwater torque on the energy cost, drag and efficiency of front crawl swimming.

Underwater torque (T') is defined as the product of the force with which the swimmer's feet tend to sink times the distance between the feet and the centre of volume of the lungs. It has previously been shown that experimental changes of T', obtained by securing around the swimmer's waist a plastic tube filled, on different occasions, with air, water or 2-kg lead, were accompanied by changes in the energy cost of swimming per unit of distance (Cs) at any given speed. The aim of this study was to investigate whether the observed increases of Cs with T' during front crawl swimming were due to an increase of active body drag (Db), a decrease of drag efficiency (eta /d) or both. The effect of experimental changes of T' on Cs, Db and eta /d were therefore studied on a group of eight male elite swimmers at two submaximal speeds (1.00 and 1.23 m.s-1). To compare different subjects and different speeds, the individual data for Cs, Db, eta /d and T' were normalized dividing them by the corresponding individual averages. These were calculated from all individual data (of Cs, Db, eta /d and T') obtained from that subject at that speed. It was found that, between the two extremes of this study (tube filled with air and with 2-kg lead), T' increased by 73% and that Cs, Db and eta /d increased linearly with T'. The increase of Cs between the two extremes was intermediate (approximately 20%) between that of Db (approximately 35%) and of eta /d (approximately 16%). Thus, the actual strategy implemented by the swimmers to counteract T', was to tolerate a large increase of Db. This led also to a substantial (albeit smaller) increase of r/d, the effect of which was to reduce the increase of Cs that would otherwise have occurred.

Adult↗

PubMed1996

Effects of body size, body density, gender and growth on underwater torque.

Two forces act on a human body motionless in water: weight (W) and buoyancy (B). They are applied to the center of mass (CM) and to the center of volume (CV) of the subject, respectively. CM and CV do not coincide; this generates a torque that is a measure of the tendency of the upper part of the body to rise, rotating around its center of mass. To quantify this tendency, Pendergast & Craig defined 'underwater torque' (T') as the product of the net force with which the feet of a subject lying horizontally in water tend to sink, times the distance between the feet and the center of volume of the lungs. In this paper we have investigated: (a) the relationships between T' and body weight (BW), height (H), body surface area (BS), body density (BD) and leg density (LD) in a group of 30 subjects (group A, 14 females and 16 males, age range 16-50 years); and (b) the effect of gender and growth on T' in a group of 110 subjects (group B, 67 girls and 43 boys, age range 12-17 years). In group A, T' was found to be linearly related with BW (r=0.833, P<0.001), H (r=0.803, P<0.001), BS (r=0.866, P<0.001), BD (r=0.617, P<0.001) and LD (r=0.549, P<0.005). A multiple linear regression analysis showed that BS and BD explained about 85% of the variability of T' (r2=0.85). In group B, T' was found to increase linearly with age (r=0.47, P<0.01), the increasing rate being three times higher in boys compared with girls. As a consequence, the T' ratio between boys and girls increased with age, from 1.69 at 13 years to 2.04 at 16 years.

Adolescent↗

PubMed1995

The energy cost of level walking in patients with hemiplegia.

The energy cost of level walking (Cw) was measured from the ratio of O2 consumption to speed (from 0.1 to 1.2 m.s-1) in hemiplegic patients (n = 20) and in a control group of healthy subjects (n = 17). Average age and body mass were 58, 54 years and 73, 78 kg, respectively. In hemiplegic patients Cw was higher than in control subjects (average value at 1.0 m.s-1 = 3.6 and 3.3 J.m-1.kg-1, respectively) and this difference increased at lower speeds (from 5.1% at 1.2 m.s-1 to 28.7% at 0.1 m.s-1).

Energy Metabolism↗

PubMed1995

Bioenergetics and biomechanics of front crawl swimming.

"Underwater torque" (T') is one of the main factors determining the energy cost of front crawl swimming per unit distance (Cs). In turn, T' is defined as the product of the force with which the swimmer's feet tend to sink times the distance between the feet and the center of volume of the lungs. The dependency of Cs on T' was further investigated by determining Cs in a group of 10 recreational swimmers (G1: 4 women and 6 men) and in a group of 8 male elite swimmers (G2) after T' was experimentally modified. This was achieved by securing around the swimmers' waist a plastic tube filled, on different occasions, with air, water, or 1 or 2 kg of lead. Thus, T' was either decreased, unchanged, or increased compared with the natural condition (tube filled with water). Cs was determined, for each T' configuration, at 0.7 m/s for G1 and at 1.0 and 1.2 m/s for G2. For T' equal to the natural value, Cs (in kJ.m-1.m body surface area-2) was 0.36 +/- 0.09 and 0.53 +/- 0.13 for G1 in women and men, respectively, and 0.45 +/- 0.05 and 0.53 +/- 0.06 for G2 at 1.0 and 1.2 m/s, respectively. In a given subject at a given speed, Cs and T' were linearly correlated. To compare different subjects and different speeds, the single values of Cs and T' were normalized by dividing them by the corresponding individual averages. These were calculated from all single values (of Cs or T') obtained from that subject at that speed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Effects of stride frequency on mechanical power and energy expenditure of walking.

The energetics and mechanics of walking were investigated at different speeds, both at the freely chosen stride frequency (FCSF) and at imposed ones (up to +/- 40% of FCSF). Metabolic energy expenditure was minimized at FCSF for each speed. Motion analysis allowed to calculate: the mechanical internal work rate (Wint), needed to move the segments with respect to the body center of mass (bcm); the external work rate (Wext), necessary to move bcm in the environment; and the total work rate (Wtot), equal to Wint+Wext. Wtot explains the metabolic optimization only at high speeds, while Wext, differently from previously reported, displays minima which better predict FCSF at all speeds (exception made for 1.39 m.s-1). This is probably caused by an overestimation of Wint due to a more ballistic movement of the limbs at low speeds (and low frequencies). The tendency of Wext to increase at high frequencies is due to a persistent minimal vertical excursion of bcm (about 0.02 m, the "locomotory dead space"). While the match between mechanics and energetics (at FCSF and imposed frequencies) occurs to a certain extent, it could be improved by removing the methodological assumptions about the energy transfer between segments and by the possibility to account for the coactivation of antagonist muscles.

Adult↗

PubMed1993

Effects of prolonged cycle ergometer exercise on maximal muscle power and oxygen uptake in humans.

The mechanical power (Wtot, W.kg-1) developed during ten revolutions of all-out periods of cycle ergometer exercise (4-9 s) was measured every 5-6 min in six subjects from rest or from a baseline of constant aerobic exercise [50%-80% of maximal oxygen uptake (VO2max)] of 20-40 min duration. The oxygen uptake [VO2 (W.kg-1, 1 ml O2 = 20.9 J)] and venous blood lactate concentration ([la]b, mM) were also measured every 15 s and 2 min, respectively. During the first all-out period, Wtot decreased linearly with the intensity of the priming exercise (Wtot = 11.9-0.25.VO2). After the first all-out period (t greater than 5-6 min), and if the exercise intensity was less than 60% VO2max, Wtot, VO2 and [la]b remained constant until the end of the exercise. For exercise intensities greater than 60% VO2max, VO2 and [la]b showed continuous upward drifts and Wtot continued decreasing. Under these conditions, the rate of decrease of Wtot was linearly related to the rate of increase of VO2 [(dWtot/dt) (W.kg-1 x s-1) = 5.0 x 10(-5) -0.20.(VO2/dt) (W.kg-1 x s-1)] and this was linearly related to the rate of increase of [la]b [(dVO2/dt) (W.kg-1 x s-1) = 2.3 x 10(-4) + 5.9 x 10(-5).(d[la]b/dt) (mM.s-1)].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Energetics of best performances in middle-distance running.

Oxygen consumption (VO2) and blood lactate concentration were determined during constant-speed track running on 16 runners of intermediate level competing in middle distances (0.8-5.0 km). The energy cost of track running per unit distance (Cr) was then obtained from the ratio of steady-state VO2, corrected for lactate production, to speed; it was found to be independent of speed, its overall mean being 3.72 +/- 0.24 J.kg-1 x m-1 (n = 58; 1 ml O2 = 20.9 J). Maximal VO2 (VO2max) was also measured on the same subjects. Theoretical record times were then calculated for each distance and subject and compared with actual seasonal best performances as follows. The maximal metabolic power (Er max) a subject can maintain in running is a known function of VO2max and maximal anaerobic capacity and of the effort duration to exhaustion (te). Er max was then calculated as a function of te from VO2max, assuming a standard value for maximal anaerobic capacity. The metabolic power requirement (Er) necessary to cover a given distance (d) was calculated as a function of performance time (t) from the product Crdt-1 = Er. The time values that solve the equality Er max(te) = Er(t), assumed to yield the theoretical best t, were obtained by an iterative procedure for any given subject and distance and compared with actual records.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

The energy cost of walking or running on sand.

Oxygen uptake (VO2) at steady state, heart rate and perceived exertion were determined on nine subjects (six men and three women) while walking (3-7 km.h-1) or running (7-14 km.h-1) on sand or on a firm surface. The women performed the walking tests only. The energy cost of locomotion per unit of distance (C) was then calculated from the ratio of VO2 to speed and expressed in J.kg-1.m-1 assuming an energy equivalent of 20.9 J.ml O2-1. At the highest speeds C was adjusted for the measured lactate contribution (which ranged from approximately 2% to approximately 11% of the total). It was found that, when walking on sand, C increased linearly with speed from 3.1 J.kg-1.m-1 at 3 km.h-1 to 5.5 J.kg-1.m-1 at 7 km.h-1, whereas on a firm surface C attained a minimum of 2.3 J.kg-1.m-1 at 4.5 km.h-1 being greater at lower or higher speeds. On average, when walking at speeds greater than 3 km.h-1, C was about 1.8 times greater on sand than on compact terrain. When running on sand C was approximately independent of the speed, amounting to 5.3 J.kg-1.m-1, i.e. about 1.2 times greater than on compact terrain. These findings could be attributed to a reduced recovery of potential and kinetic energy at each stride when walking on sand (approximately 45% to be compared to approximately 65% on a firm surface) and to a reduced recovery of elastic energy when running on sand.

Adult↗

PubMed1992

Blood lactate during leg exercise in microgravity.

Venous blood lactate concentration ([La]b) was measured in five male subjects (age: 30-50 years; BW: 72-84 kg, VO2max:2.2-3.6 l min-1) during cycloergometric exercise in microgravity obtained by parabolic flight maneuvers of approximately 25 s duration. The subject(s) exercised at 30, 60, 90 and 120 W (60 RPM) for at least 7 min at each intensity. Three consecutive parabolas with approximately 3 min interval were performed at each workload. [La]b was determined at rest and immediately after 60, 90 and 120 W exercise. The day after the flight experiments, the subject(s) underwent the same experimental protocol on the ground and the blood samples were taken at the very same time intervals as on the aircraft. [La]b in flight and control didn't show any appreciable difference once the values are plotted as a function of the relative exercise intensities expressed as a percent of the individual VO2max corrected for the moderate hypoxia prevailing inside the aircraft (cabin barometric pressure = 590 mmHg).

Adult↗

PubMed1991

Effects of order of presentation of exercise intensities and of sauna baths on perceived exertion during treadmill running.

Thirteen male subjects performed a running test on the treadmill consisting of four standard exercise intensities [65%, 75%, 85%, 95% maximal O2 uptake (VO2 max)] presented in ascending, descending or random order. At the end of each exercise intensity, O2 consumption, heart rate (fc), venous blood lactate concentration [( Ia]b) and perceived exertion were assessed. This last variable was determined according to the Borg nonlinear CR-20 scale. The same variables were also determined during exercise at a standard intensity (65% or 95% VO2 max) performed before and after a Finnish sauna bath. Ratings of perceived exertion showed a good test-retest reliability (r = 0.77); they were the same when the exercise intensity was expressed in relative (%VO2 max) or absolute (speed) terms, and were independent of the order of presentation of the exercise. The latter had no effect on fc either but it did, however, influence [Ia]b, which was significantly higher in the descending, as compared to the ascending or random modes of presentation. The sauna bath increased fc at a given exercise intensity, but left perceived exertion and [Ia]b unchanged. It was concluded that at least under the present experimental conditions, fc and venous [Ia]b do not play a major role as determinants of perceived exertion.

Adult↗

PubMedDate not supplied

Energetics of kayaking at submaximal and maximal speeds.

The energy cost of kayaking per unit distance (C(k), kJ x m(-1)) was assessed in eight middle- to high-class athletes (three males and five females; 45-76 kg body mass; 1.50-1.88 m height; 15-32 years of age) at submaximal and maximal speeds. At submaximal speeds, C(k) was measured by dividing the steady-state oxygen consumption (VO(2), l x s(-1)) by the speed (v, m x s(-1)), assuming an energy equivalent of 20.9 kJ x l O(-1)(2). At maximal speeds, C(k) was calculated from the ratio of the total metabolic energy expenditure (E, kJ) to the distance (d, m). E was assumed to be the sum of three terms, as originally proposed by Wilkie (1980): E = AnS + alphaVO(2max) x t-alphaVO(2max) x tau(1-e(-t x tau(-1))), were alpha is the energy equivalent of O(2) (20.9 kJ x l O(2)(-1)), tau is the time constant with which VO(2max) is attained at the onset of exercise at the muscular level, AnS is the amount of energy derived from anaerobic energy utilization, t is the performance time, and VO(2max) is the net maximal VO(2). Individual VO(2max) was obtained from the VO(2) measured during the last minute of the 1000-m or 2000-m maximal run. The average metabolic power output (E, kW) amounted to 141% and 102% of the individual maximal aerobic power (VO(2max)) from the shortest (250 m) to the longest (2000 m) distance, respectively. The average (SD) power provided by oxidative processes increased with the distance covered [from 0.64 (0.14) kW at 250 m to 1.02 (0.31) kW at 2000 m], whereas that provided by anaerobic sources showed the opposite trend. The net C(k) was a continuous power function of the speed over the entire range of velocities from 2.88 to 4.45 m x s(-1): C(k) = 0.02 x v(2.26) (r = 0.937, n = 32).

Adolescent↗

PubMedDate not supplied

Effects of microgravity on muscular explosive power of the lower limbs in humans.

The maximal explosive power of the lower limbs of one astronaut has been measured before launch, and 2, 6 and 11 days after re-entry from 31 days on the MIR Station (EUROMIR '94). The subject, sitting on the carriage-seat of a Multipurpose Ergometer-Dynamometer (MED) constructed ad hoc in our laboratory, pushed maximally with both feet on two force platforms (knees angle 110 degrees). The carriage was free to move backwards on two rails inclined 20 degrees upwards. The force (F) of the lower limbs and the speed of the carriage (v) were recorded and the instantaneous mechanical power (w) was calculated as w = F * v. The average value of the mechanical power (w max) throughout the explosive effort was then obtained. The overall duration of the push was on the average about 0.3 s. It was observed that, at day R+2, mean force, maximal velocity, maximal power (mean and peak), maximal acceleration and overall mechanical work, were all reduced between 60 and 80% of pre-flight values. However, the recovery was remarkably fast, since all these parameters attained about 90% of pre-flight values by day R+11.

Biomechanical Phenomena↗

PubMedDate not supplied

The influence of drag on human locomotion in water.

Propulsion in water requires a propulsive force to overcome drag. Male subjects were measured for cycle frequency, energy cost and drag (D) as a function of velocity (V), up to maximal V, for fin and front crawl swimming, kayaking and rowing. The locomotion with the largest propulsive arms and longest hulls traveled the greatest distance per cycle (d/c) and reached higher maximal V. D while locomotoring increased as a function of V, with lower levels for kayaking and rowing at lower Vs. For Vs below 1 m/s, pressure D dominated, while friction D dominated up to 3 m/s, after which wave D dominated total D. Sport training reduced the D, increased d/c, and thus lowered C and increased maximal V. Maximal powers and responses to training were similar in all types of locomotion. To minimize C or maximize V, D has to be minimized by tailoring D type (friction, pressure or wave) to the form of locomotion and velocity.

Adult↗