169,781 research outputs found
Breath-by-breath estimate of alveolar gas transfer variability in man at rest and during exercise
No full textEffects of nitric oxide on diaphragmatic muscle endurance and strength in pigs
No full textThe aim of the study was to evaluate the effects of nitric oxide (NO) on diaphragmatic fatigue in fifteen anaesthetized, mechanically ventilated pigs, divided into three groups. The animals were pre-treated with indomethacin (3 mg kg-1, i.v.) to block the cyclo-oxygenase pathway. To group 1 pigs (n = 6) NG-nitro-L-arginine methyl ester (L-NAME, 5 mg kg-1 i.v.) was administered as a bolus to block endogenous NO production, while group 2 pigs (n = 6) were infused with sodium nitroprusside (SNP, 0.023 mg kg-1, i.v.), a donor of NO. Group 3 pigs (n = 3) were used as the controls. We evaluated diaphragmatic strength by measuring the transdiaphragmatic pressure (P di) generated during bilateral phrenic nerve stimulation at 10, 20, 30 and 50 Hz, 15 V, while the diaphragmatic endurance was assessed by a 30s stimulation at 10 Hz, 15 V. Diaphragmatic index was assessed as the ratio of peak force between single twitches performed before and after the 30 s stimulation west. We also evaluated mean systemic (MAP) and pulmonary (MPAP) arterial pressures, pulmonary wedge pressure (PW), systemic (SVR) and pulmonary vascular resistance (PVR) and cardiac output (CO). L-NAME increased MAP, MPAP, PW, SVR and PVR, but decreased CO. SNP caused a decrease in MAP, MPAP, PW and SVR, while PVR and CO did not change. The main finding of this study was that diaphragmatic strength was not significantly weakened after L-NAME administration, except at 10 Hz, while it did not change after SNP infusion. However, both L-NAME and SNP caused significant decreases in diaphragmatic endurance capacity. The fatigue appearing after L-NAME is probably correlated with a decline in diaphragmatic blood flow, as evidenced by the increase in SVR and the decrease in CO, and consequently in oxygen supply. In contrast, the decrease in endurance capacity after SNP infusion can be attributed to a direct action of NO on skeletal muscle
Effects of short-term, integrated body mass reduction program on maximal oxygen consumption and anaerobic alactic performance in obese subjects
No full textThe study investigated the effect of a short-term (3-week) body mass reduction program, combining energy-restricted diet, nutritional education, psychological counselling and aerobic exercise training (DEP-AT) on maximal oxygen consumption (VO2max) and anaerobic alactic performance evaluated with different techniques in obese patients (grade II and III). Fifty-three (14 males, 39 females) obese subjects [average±SD body mass index (BMI): 41.6±4.2 kg/m2] were tested before and after the DEP-AT program characterised by a daily conditioning protocol of aerobic exercise on cycloergometer, treadmill and armergometer for a total duration of 35 min at an intensity corresponding to 50% of individual VO2max during the first week of the program and at 60% in the following 2 weeks. VO2max was determined with the cycloergometric indirect method. Short-term alactic anaerobic performance was evaluated with: a) jumping test (5 consecutive jumps with maximal effort, Bosco technique), b) short sprint running test (8 m), and c) stair climbing test (modified Margaria test). The DEP-AT program induced a significant weight loss (-4.57±1.26%, p<0.001) and a significant ̇VO2max increase (14.1±20.5%, p<0.001). After the DEP-AT program, lower limb alactic anaerobic power output, calculated on a per kg body mass basis, increased significantly both in jumping and in stair climbing (20.1±24.8%, p<0.001 and 13.5±19.75%, p<0.001, respectively), as well as average horizontal velocity during short sprinting (7.2±17.6%, p<0.01 . Power output was a major determinant of the motor performance, being significantly correlated with: a) vertical displacement of the centre of gravity (R2=0.884, p<0.001) in jumping test, b) vertical velocity (R2=0.348, p<0.001) in stair climbing test, and c horizontal velocity (R2=0.394, p<0.001) in short running test. In conclusion, short-term DEP-AT program induces significant improvements in both aerobic capabilities and anaerobic performance, possibly through the combination of a number of contributory mechanisms, such as exercise-mediated training, shift in the balance between parasympathetic and sympathetic activity, a weight-loss dependent shift toward a more favourable region of the muscle power-velocity curve, acquisition of a certain degree of motor skill during the conditioning program, improvement of self-esteem and motivation. © 2003, Editrice Kurtis
The impact of gender, body dimension and body composition on hand-grip strength in healthy children
No full textMaximum hand-grip (HG) strength, body composition and main anthropometric variables were evaluated in 278 children with normal weight and growth, aged 5-15 yr divided into 3 age groups: group 1, age+/-SD: 7.6+/-0.9 yr 7.6+/-0.9 SD (Tanner stage 1); group 2, age: 10.8+/-0.7 yr (Tanner stage: 2-3); group 3, age: 13.2+/-0.9 yr (Tanner stage: 4-5). Weight, height, body surface area (BSA), BMI, percent body fat (BF) and fat free mass (FFM) increased progressively and significantly from the younger to the older age group. A significant difference between genders was detected only for BF and FFM, females having a higher fat mass and a lower FFM compared to males. Most children were right-handed (91%). In either genders, a curvilinear relation was detected between HG strength and age, with best fit for the dominant (d) hand given by the equations: dHG=5.891 *10(0.051) age, r2=0.986, p<0.001 in males and dHG=6.163 *10(0.045) age r2=0.973, p<0.001 in females. The increase in HG strength after 11 yr appears to be steeper in males as compared with that found in females. In both d and non-dominant (nd) hand, a significant difference in HG strength was detected between males and females, the average difference being about 10% at all ages. For both genders, nd hand was significantly weaker than d hand in the older age groups (2 and 3), but not in the younger group 1. Age and gender-dependent differences in HG strength (but not differences between d and nd hand) disappear if HG strength is normalized for FFM. Thus, in general, dHG strength normalized for FFM resulted on average to be 0.67+/-0.11 kg/kg. A multiple linear regression analysis indicated that HG was positively correlated with BMI, BSA, stature, stature2 and FFM (p<0.001 for all correlations) without differences between genders, while a negative correlation was found between HG strength and %BF. The most significant correlation was found between HG strength and FFM, without any significant difference between genders, so that the overall equation describing the line for the d hand was: dHG strength= 2.32+0.63 FFM, r2=0.72, p<0.001. In conclusion, the present study indicates that the age-dependent increase of HG strength as well as the between-gender differences are strongly related to changes of FFM values occurring during childhood. Moreover, the study provides a standard normative value of maximal HG strength for the healthy children population in Northern Italy
Respiratory airflow pattern in patients with chronic airway obstruction
No full textPrevious experimental evidence has shown that in healthy humans inspiratory airflow waveform can be optimized according to minimum rate of work criteria when the respiratory energetic requirements become a substantial fraction of the general metabolism (i.e., during exercise hyperpnea and maximum voluntary ventilation). In patients with chronic airway obstruction (CAO) the relative energetic expenditure devoted to respiration is also greatly enhanced at rest. To investigate the performance of a system also controlling airflow wave pattern in this condition we evaluated by Fourier analysis the harmonic content of respiratory flow waves recorded at rest and during exercise hyperpnea (25 and 50 W on cycloergometer) in 15 patients. The results were compared with those we previously obtained in normal subjects and with some theoretical models. It was found that, while normal subjects display at rest an inspiratory flow waveform reasonably close to a sinusoidal model and adopt a more rectangular and economical flow shape during exercise hyperpnea, patients with CAO show a rather rectangular inspiratory flow shape also at rest, without any remarkable change at higher levels of ventilation. So, in general terms, the airflow pattern employed by patients at rest entails a reduction in the rate of dynamic inspiratory work of about 12% over that required by a sinusoidal waveform, and no further advantage is observed during exercise hyperpnea. Some features of the expiratory flow wave were also analysed. As no model of the respiratory system mechanics presently developed can explain the findings obtained in CAO patients purely on the basis of their altered mechanical parameters, it has been suggested that more complex control of respiratory airflow is operating in this class of patient
Effects of a 16-week progressive high-intensity strength training (HIST) on indexes of bone turnover in men over 65 years: A randomized controlled study
No full textThe aim of the present study was to evaluate the effects of a 16-week progressive high-intensity strength training (HIST) program on peripheral markers of bone turnover (bone Gla protein, BGP; bone alkaline phosphatase, B-AP; N-terminal propeptide of type I procollagen, PINP; C-terminal cross-linked telopeptide of type I collagen, ICTP) in healthy, elderly men over 65 yr of age. Thirty healthy men (aged 65-81 yr), performing light to moderate daily physical activity, were randomly divided into two groups. Group 1 (no.=16) followed a supervised 16-week progressive HIST program, while subjects of group 2 (no.=14), used as controls, were requested to maintain their habitual level of physical activity for 16 weeks. HIST program consisted of 6 different sets of exercise (2 involving the major muscle groups of the lower limb and 4 involving those of the upper limb). Three sessions/week, during which 10 repetitions of each exercise set were completed, were performed. Lower limb exercises shifted from 50 to 80% of the one maximal repetition (1 MR) during the first month of the protocol and were thereafter maintained at an intensity of 80% 1 MR throughout the training. Upper limb exercises shifted from 40 to 65% of 1 MR with a similar pattern. All sessions were preceded by 15 min of cycloergometer exercise at 50% of maximal oxygen uptake and by a warm-up of 15 repetitions at 20% of 1 MR of each exercise set. The HIST program did not significantly change BGP (mean +/- SE, before: 15.6 +/-1.2 mug/l vs after: 16.0 +/-1.2 mug/l, NS) and PINP levels (before: 44.6 +/-6.7 mug/l vs after: 43.1 +/-6.0 mug/l, NS). On the contrary, serum B-AP significantly increased (before: 50.2 +/-6.1 IU/l vs after: 62.3 +/-7.0 IU/l, p <0.001) and serum ICTP slightly reduced (before: 4.0 +/-0.3 mug/l vs after: 3.8 +/-0.3 mug/l, p <0.05). When bone turnover was expressed as the ratio between bone formation to bone resorption (B-AP/ICTP ratio), a significant improvement in this ratio was found in all subjects of group 1 (before: 12.9 +/-1.3 IU/mug vs after: 17.3 +/-1.5 IU/mug, p <0.0001), while no significant changes were observed in Group 2. No significant changes of IGF-I levels were observed after the HIST program (before: 94.9 +/-9.4 mug/l vs after: 89.9 +/-9.7 mug/l). No significant changes of BGP, PINP, B-AP, ICTP, B-AP-ICTP ratio and IGF-I levels were observed in controls (group 2) during the 16 weeks of observation. Although the positive effects of a progressive HIST program on B-AP levels and B-AP-ICTP ratio seem promising, the support of bone mass measurement and the determination of other bone markers are requested to better identify exercise protocol (duration, intensity) for elderly people
Test di valutazione del lavoro meccanico dei muscoli respiratori nel cavallo durante iperventilazione ipercapnica e iperpnea da lavoro
No full textThe study of the mechanical work of breathing (Wresp) is an important step in the evaluation of equine maximal performance. In this work we compared two different techniques (hypercapnic hyperventilation with an added dead space at rest (HHVD) and hyperpnea during treadmill exercise (HTE)) to determine the function between Wresp and ventilation (Ve) in healthy horses. Wresp was also measured in a group of horses affected by inflammatory airway disease (IAD) with HHVD test. No difference in Wresp measured with the two different techniques, at comparable ventilatory levels, was found in healthy animals. Compared with normal horses, in animals with IAD, Wresp at the same Ve was higher. Since both techniques show comparable results in normal animals, HHVD can be used as diagnostic tool in horses in which treadmill exercise could be inappropriat
An analysis of world records in three types of locomotion
No full textThe record history of running, swimming and ice-skating, over various distances, was analyzed. A mean period of about 66 years for the 18 male events and of about 50 years for the 14 female events was studied. Over a given distance the velocity (v) was related to the dates of the records minus 1900 (T) according to polynomial functions like: Mathematical expression In 21 out of the 32 events equations of first or second degree fitted the experimental data. The mean correlation coefficient was 0.979±0.019 (± S.D.). The ratio between predicted (v1p) and actual value (v1) of the last records was 0.999±0.010. For T corresponding to v1 (T1), the rate of record growth was slowing down in 5 events. Hence up to June 1981 a tendency towards an asymptotic v was not yet a general phenomenon. At T1 the range of the relative rate of increase of v (dvp/dT·(v1p) was 0.9·10-3 per year (800 m - female running) and 12.4·10-3 per year (800 m - female swimming). dv/dT·(v1p) in swimming and skating was similar in both sexes but 4 times faster than in male running. Less marked differences were found for female running. A lowering of the cost of transport was probably the main reason of the fast growth of swimming and skating records. The numerical constants calculated from linear regression of v versus the time of the races over different distances did not seem to have a clear physiological meaning, as reported in the previous literature. © 1982 Springer-Verlag
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