Biomedical subjects

C Bosco

Publications and source records attributed to C Bosco.

At least 19 recordsLinked to original sources

PubMed2005

Increased immunohistochemical expression of thrombomodulin at placental perivascular myofibroblast in severe preeclampsia (PE).

The presence of pro-coagulant and anti-coagulant components of the placental vascular endothelium and syncytiotrophoblast are essential for homeostasis. Vascular endothelium prevents blood clot formation in vivo by involving a cell surface thrombin-binding glycoprotein, thrombomodulin (TM), that activates plasma anti-coagulant protein C. The TM levels increase during pregnancy, but the fibrinolytic capacity diminishes. Since vascular lesions with placental coagulation disorders can be associated with preeclampsia (PE), we hypothesized that TM expression in the stem villous vasculature and syncytiotrophoblast of the placenta are impaired in PE. Plasma and placental tissue samples were collected from PE (n=12) and normotensive pregnant patients (n=11). Patient's gestational age was 35.7+/-1.2 (normotensive) and 30.6+/-1.5 weeks (PE). Blood samples were drawn 30 min before delivery. Serum PAI-1 and PAI-2 antigens were determined by enzyme-linked immunoabsorbent assay (ELISA). A monoclonal antibody specific for TM was used for immunohistochemical tissue staining (ABC) and the staining was quantified by semi quantitative scores. Results show no intensity differences at the apical syncytiotrophoblast between the two groups. However, in preeclamptic placenta, TM expression diminished in the endothelium of the stem villi arteries and increased in the perivascular and stromal myofibroblats in cases of severe PE. TM changes were associated with an increased PAI-1/PAI-2 ratio. It is suggested that in severe PE, the decreased placental blood flow may be due to structural and functional impairment of the endothelium of the stem villi vessels and the surrounding perivascular and stromal myofibroblast, by increasing TM expression which may modulate fetal blow flow in the villous tree.

Actins↗

PubMed2004

Effects of whole-body vibration exercise on the endocrine system of healthy men.

Whole-body vibration is reported to increase muscle performance, bone mineral density and stimulate the secretion of lipolytic and protein anabolic hormones, such as GH and testosterone, that might be used for the treatment of obesity. To date, as no controlled trial has examined the effects of vibration exercise on the human endocrine system, we performed a randomized controlled study, to establish whether the circulating concentrations of glucose and hormones (insulin, glucagon, cortisol, epinephrine, norepinephrine, GH, IGF-1, free and total testosterone) are affected by vibration in 10 healthy men [age 39 +/- 3, body mass index (BMI) of 23.5 +/- 0.5 kg/m2, mean +/- SEM]. Volunteers were studied on two occasions before and after standing for 25 min on a ground plate in the absence (control) or in the presence (vibration) of 30 Hz whole body vibration. Vibration slightly reduced plasma glucose (30 min: vibration 4.59 +/- 0.21, control 4.74 +/- 0.22 mM, p=0.049) and increased plasma norepinephrine concentrations (60 min: vibration 1.29 +/- 0.18, control 1.01 +/- 0.07 nM, p=0.038), but did not change the circulating concentrations of other hormones. These results demonstrate that vibration exercise transiently reduces plasma glucose, possibly by increasing glucose utilization by contracting muscles. Since hormonal responses, with the exception of norepinephrine, are not affected by acute vibration exposure, this type of exercise is not expected to reduce fat mass in obese subjects.

Adult↗

PubMed2001

Glucocorticoid receptors in human peripheral blood mononuclear cells in relation to explosive performance in elite handball players.

Ten handball players, members of the Italian National Team (aged 20-25 years), were studied in two sessions corresponding to different performance levels. The first session occurred one week after the end of the regular season of the Italian Handball Federation: it corresponded to the beginning of the training cycle for the European Handball Championship. The second session occurred ten weeks after the first session. During this period, training consisted of 3 weeks of active recovery and 7 weeks of increasing workload. For each session, jumping performances (maximal height in a single jump, average mechanical power for a 15-s set of consecutive jumps) were evaluated. Venous blood samples were collected in resting conditions immediately before jumping performances to assess cortisol and testosterone plasma concentrations and glucocorticoid receptors (GcR) binding capacity and affinity in peripheral blood mononuclear cells (PBMCs). All the parameters, except GcR binding affinity, increased in the second session. The trends of variation in jumping performances, steroid hormone levels and GcR binding capacity were similar. For testosterone, this agrees with the hypothesis that an adequate level of this hormone is a prerequisite for improvement in explosive performances. For cortisol, higher GcR binding capacity after 10 weeks of training (with respect to initial values) indicated an up-regulation of GcR concomitant with the increase in hormone levels and performances. These findings suggest that the adaptation to training, confirmed by the improvement in performance, is characterized by a high value of GcR binding capacity and that it is mediated, among other factors, by the hormone levels and up-regulation of the receptors.

Adult↗

PubMed2001

Effects of iron overload and lindane intoxication in relation to oxidative stress, Kupffer cell function, and liver injury in the rat.

Parameters related to liver oxidative stress, Kupffer cell function, and hepatocellular injury were assessed in control rats and in animals subjected to lindane (40 mg/kg; 24 h) and/or iron (200 mg/kg; 4 h) administration. Independently of lindane treatment, iron overload enhanced the levels of iron in serum and liver. Biliary efflux of glutathione disulfide increased by 140, 160, or 335% by lindane, iron, or their combined administration, respectively, and the hepatic content of protein carbonyls was elevated by 5.84-, 2.95-, and 10-fold. Colloidal carbon uptake by perfused livers was not modified by lindane and/or iron, whereas gadolinium chloride (GdCl(3)) pretreatment diminished uptake by 60-72%. Carbon-induced liver O(2) uptake was not altered by lindane, whereas iron produced a 61% increase and the combined treatment led to a 72% decrease over control values. Pretreatment with GdCl(3) abolished these effects in all groups. Lindane-treated rats showed acidophilic hepatocytes in periportal areas and some hepatic cells with nuclear pyknosis, whereas iron overload led to moderate hyperplasia and hypertrophy of Kupffer cells and moderate inflammatory cell infiltration. Combined lindane-iron treatment led to hepatocytes with pyknotic nuclei, significant acidophilia, and extensive lymphatic and neutrophil infiltration in the portal space. Hepatic myeloperoxidase activity increased by 1.1-, 2.1-, or 6.7-fold by lindane, iron, or their combined administration, respectively. Liver sinusoidal lactate dehydrogenase efflux increased by 2.2-fold (basal conditions) and 9.7-fold (carbon infusion) in the lindane-iron treated rats, effects that were diminished by 35 and 78% by GdCl(3) pretreatment, respectively. These data support the contention that lindane sensitizes the liver to the damaging effects of iron overload by providing an added enhancement to the oxidative stress status in the tissue, and this may contribute to the alteration of the respiratory activity of Kupffer cells and the development of an inflammatory response.

Animals↗

PubMed2000

Hormonal responses to whole-body vibration in men.

The aim of this study was to evaluate the acute responses of blood hormone concentrations and neuromuscular performance following whole-body vibration (WBV) treatment. Fourteen male subjects [mean (SD) age 25 (4.6) years] were exposed to vertical sinusoidal WBV, 10 times for 60 s, with 60 s rest between the vibration sets (a rest period lasting 6 min was allowed after 5 vibration sets). Neuromuscular performance tests consisting of counter-movement jumps and maximal dynamic leg presses on a slide machine, performed with an extra load of 160% of the subjects body mass, and with both legs were administered before and immediately after the WBV treatment. The average velocity, acceleration, average force, and power were calculated and the root mean square electromyogram (EMGrms) were recorded from the vastus lateralis and rectus femoris muscles simultaneously during the leg-press measurement. Blood samples were also collected, and plasma concentrations of testosterone (T), growth hormone (GH) and cortisol (C) were measured. The results showed a significant increase in the plasma concentration of T and GH, whereas C levels decreased. An increase in the mechanical power output of the leg extensor muscles was observed together with a reduction in EMGrms activity. Neuromuscular efficiency improved, as indicated by the decrease in the ratio between EMGrms and power. Jumping performance, which was measured using the counter-movement jump test, was also enhanced. Thus, it can be argued that the biological mechanism produced by vibration is similar to the effect produced by explosive power training (jumping and bouncing). The enhancement of explosive power could have been induced by an increase in the synchronisation activity of the motor units, and/or improved co-ordination of the synergistic muscles and increased inhibition of the antagonists. These results suggest that WBV treatment leads to acute responses of hormonal profile and neuromuscular performance. It is therefore likely that the effect of WBV treatment elicited a biological adaptation that is connected to a neural potentiation effect, similar to those reported to occur following resistance and explosive power training. In conclusion, it is suggested that WBV influences proprioceptive feedback mechanisms and specific neural components, leading to an improvement of neuromuscular performance. Moreover, since the hormonal responses, characterised by an increase in T and GH concentration and a decrease in C concentration, and the increase in neuromuscular effectiveness were simultaneous but independent, it is speculated that the two phenomena might have common underlying mechanisms.

Adult↗

PubMed2000

Monitoring strength training: neuromuscular and hormonal profile.

PURPOSE: This study investigated changes induced by a single heavy resistance training session on neuromuscular and endocrine systems in trained athletes, using the same exercises for training and testing. METHODS: Five different groups volunteered: track and field male sprinters (MS, N = 6), track and field female sprinters (FS, N = 6), body builders (BB, N = 6), and weight lifters performing low-repetition exercise (WLL, N = 4) and high-repetition exercise (WLH, N = 4). In training, the work performed during half and full squat exercise was monitored for mechanical power output as well as EMG analysis on leg extensor muscles of the subjects belonging to the MS, FS, and BB groups. Just before and immediately after the training session, venous blood samples were obtained for RIA determination of testosterone (T), cortisol (C), lutropin (LH), human prolactin (PRL), and follitropin (FSH) in FS and MS. In the other three groups (BB, WLH, and WLL), the hormonal profile was limited to T and human growth hormone (hGH) only. RESULTS: After training the power developed in full squat demonstrated a statistically significant decrease (P < 0.01) in MS and no changes in FS. The EMG activity remained constant during the training session. Consequently, the EMG/Power ratio increased in both MS and FS, although only in MS a statistical significance was noted (P < 0.05). In MS immediately after the session the levels of C, T, and LH were significantly lower (P < 0.05). No changes were found in FS. In both groups and in BB significant negative correlation was found between changes in T level and EMG/Power ratio in half squat performance. CONCLUSIONS: It is likely that adequate T level may compensate the effect of fatigue in FT fibers by ensuring a better neuromuscular efficiency.

Adult↗

PubMed1999

Effects of bromoethylamine on antioxidant capacity, lipid peroxidation, and morphological characteristics of rat liver.

Administration of bromoethylamine (BEA, 1.2 mmol/kg) to fed rats induced a significant diminution in the activity of hepatic superoxide dismutase (at 1 h after treatment), catalase, and glutathione peroxidase and in the content of nonprotein sulfhydryls (at 15 h after treatment). The content of thiobarbituric acid reactants by the liver was enhanced by 1.9 times over control values (at 3 h). Light microscopy studies revealed that BEA (72 h after treatment) induced periportal fatty accumulation, focal liver cell necrosis, and diffuse inflammatory infiltrates, in addition to hypertrophic Kupffer cells and mitotic hepatocytes. Also, hypertrophic middle tunic or hypertrophic smooth muscle layers of arterioles was observed in the periportal space, with dilated sinusoidal capillaries and free macrophage infiltration. It is concluded that BEA induces a derangement in the antioxidant status of the liver with the consequent lipid peroxidation response, which may constitute a significant hepatotoxic mechanism of the haloaklylamine.

Animals↗

PubMed1999

Influence of vibration on mechanical power and electromyogram activity in human arm flexor muscles.

The aim of this study was to evaluate the influence of vibration on the mechanical properties of arm flexors. A group of 12 international level boxers, all members of the Italian national team, voluntarily participated in the experiment: all were engaged in regular boxing training. At the beginning of the study they were tested whilst performing forearm flexion with an extra load equal to 5% of the subjects' body mass. Following this. one arm was given the experimental treatment (E; mechanical vibration) and the other was the control (no treatment). The E treatment consisted of five repetitions lasting 1-min each of mechanical vibration applied during arm flexion in isometric conditions with 1 min rest between them. Further tests were performed 5 min immediately after the treatment on both limbs. The results showed statistically significant enhancement of the average power in the arm treated with vibrations. The root mean square electromyogram (EMGrms) had not changed following the treatment but, when divided by mechanical power, (P) as an index of neural efficiency, it showed statistically significant increases. It was concluded that mechanical vibrations enhanced muscle P and decreased the related EMG/P relationship in elite athletes. Moreover, the analysis of EMGrms recorded before the treatment and during the treatment itself showed an enormous increase in neural activity during vibration up to more than twice the baseline values. This would indicate that this type of treatment is able to stimulate the neuromuscular system more than other treatments used to improve neuromuscular properties.

Adult↗

PubMed1999

Adaptive responses of human skeletal muscle to vibration exposure.

The aim of this study was to investigate the effects of whole-body vibrations (WBV) on the mechanical behaviour of human skeletal muscle. For this purpose, six female volleyball players at national level were recruited voluntarily. They were tested with maximal dynamic leg press exercise on a slide machine with extra loads of 70, 90, 110 and 130 kg. After the testing, one leg was randomly assigned to the control treatment (C) and the other to the experimental treatment (E) consisting of vibrations. The subjects were then retested at the end of the treatment using the leg press. Results showed remarkable and statistically significant enhancement of the experimental treatment in average velocity (AV), average force (AF) and average power (AP) (P < 0.05-0.005). Consequently, the velocity-force and power-force relationship shifted to the right after the treatment. In conclusion, it was affirmed that the enhancement could be caused by neural factors, as athletes were well accustomed to the leg press exercise and the learning effect was minimized.

Adaptation, Physiological↗

PubMed1999

Single and multiple selenium-zinc-iodine deficiencies affect rat thyroid metabolism and ultrastructure.

This study was conducted to evaluate the effects of single and combined deficiencies of Se, Zn and I on thyroid function in rats. Rats were fed amino acid-based diets for 6 wk starting from weaning. The diets contained either low or adequate amounts of these minerals. In addition to the control and control pair-fed groups, seven experimental groups were formed: Se deficient (Se-); I deficient (I-); Zn deficient (Zn-); Se and I deficient (Se-I-); Zn and I deficient (Zn-I-); Se and Zn deficient (Se-Zn); and Se, I and Zn deficient (Se-I-Zn-). Serum triiodothyronine (T3) was significantly lower than in controls in Zn-, Se-Zn- and Se-I- groups. Serum total thyroxine (T4) and free T4 were significantly lower and thyroid-stimulating hormone (TSH) greater in all iodine-deficient groups, regardless of Se or Zn status. Thyroid glutathione peroxidase activity was significantly reduced in Se- and Se-Zn- groups. Nevertheless, in the groups with a concurrent I deficiency, the activity of this enzyme was significantly greater than in controls. Severe alterations of the follicle cellular architecture, including signs compatible with apoptosis, were observed in the Zn- and Se-Zn- groups. These alterations appeared to be less severe when iodine deficiency was simultaneously present. Single and multiple deficiencies of Se, Zn and I have distinct effects on thyroid metabolism and structure.

Animals↗

PubMed1999

Derangement of Kupffer cell functioning and hepatotoxicity in hyperthyroid rats subjected to acute iron overload.

Liver oxidative stress, Kupffer cell functioning, and cell injury were studied in control rats and in animals subjected to L-3,3',5-tri-iodothyronine (T3) and/or acute iron overload. Thyroid calorigenesis with increased rates of hepatic O2 uptake was not altered by iron treatment, whereas iron enhanced serum and liver iron levels independently of T3. Liver thiobarbituric acid reactants formation increased by 5.8-, 5.7-, or 11.0-fold by T3, iron, or their combined treatment, respectively. Iron enhanced the content of protein carbonyls independently of T3 administration, whereas glutathione levels decreased in T3- and iron-treated rats (54%) and in T3Fe-treated animals (71%). Colloidal carbon infusion into perfused livers elicited a 109% and 68% increase in O2 uptake in T3 and iron-treated rats over controls. This parameter was decreased (78%) by the joint T3Fe administration and abolished by gadolinium chloride (GdCl3) pretreatment in all experimental groups. Hyperthyroidism and iron overload did not modify the sinusoidal efflux of lactate dehydrogenase, whereas T3Fe-treated rats exhibited a 35-fold increase over control values, with a 54% reduction by GdCl3 pretreatment. Histological studies showed a slight increase in the number or size of Kupffer cells in hyperthyroid rats or in iron overloaded animals, respectively. Kupffer cell hypertrophy and hyperplasia with presence of inflammatory cells and increased hepatic myeloperoxidase activity were found in T3Fe-treated rats. It is concluded that hyperthyroidism increases the susceptibility of the liver to the toxic effects of iron, which seems to be related to the development of a severe oxidative stress status in the tissue, thus contributing to the concomitant liver injury and impairment of Kupffer cell phagocytosis and particle-induced respiratory burst activity.

Animals↗

PubMed1997

Renal effects of chronic exposure to malathion in Octodon degus.

We studied the effects of chronic exposure to malathion in the kidney of Octodon degus, a caviomorph whose habitat may be exposed to pesticides currently used in Chilean agriculture. A group of adult female animals received malathion (200 ppm) as sole drinking fluid for 90 days. Kidneys showed signs of histologic damage, marked by hyperplasia and hypertrophy of tubular cells. Exposed animals had unchanged glomerular filtration rates and renal handling of sodium and chloride, but a significant increase in fractional excretion of potassium resulted from this treatment. The activities of Na+/K(+)-ATPase and Mg(2+)-ATPase in renal cortex and outer medulla were not affected by malathion exposure. This study provides evidence of both morphologic and functional renal damage elicited by chronic exposure of O. degus to a low dose of malathion. Morphologic alterations in glomerulus were accompanied by either morphologic and functional impairments of the distal nephron.

Animals↗

PubMed1997

Effect of oral creatine supplementation on jumping and running performance.

The study was designed to investigate the effect of creatine monohydrate ingestion (20 g daily for 5 days) on performance in 45 s maximal continuous jumping and in all-out treadmill running at 20 km x h(-1), (inclination 5 degrees, duration approximately 60s). The participants were qualified sprinters and jumpers. The effect of creatine was compared with placebo in a double-blind design. Creatine (Cr) supplementation led to a significant enhancement of performance capacity in the jumping test by 7% during the first 15 s and by 12% during the second 15 s of the exercise. The positive effect of Cr supplementation was not observed in the last third of the continuous jumping exercise, when the contribution of anaerobic metabolism was decreasing. The time of intensive running up to exhaustion improved by 13%. The results show that Cr supplementation helps to prolong the time during which the maximal rate of power output could be maintained.

Adult↗

PubMed1997

The influence of different floor stiffness on mechanical efficiency of leg extensor muscle.

The mechanical behaviour of skeletal muscle is influenced by internal factors (e.g. re-use of elastic energy) and/or external conditions (e.g. floor compliance, shoe structure etc.). These factors have an effect on muscular work economy-this was investigated in the present study. Eight subjects were tested during three different series of jumps. Each series consisted of rhythmical vertical jumps performed at desired frequency and height for 1 min. The first (1) series was executed on the laboratory floor without rebound condition (subjects were asked to maintain 1 s period in an isometric condition before concentric work was performed), the second (II) and the third (III) series were performed in rebound conditions respectively on a laboratory floor (hard surface) and on a special panel possessing high compliance (a special foam rubber panel with stiffness of 14.4 kN/m). Expired air was collected during the test and recovery for determination of energy expenditure. Mechanical work was calculated from the vertical displacement of the body during the jumps. The results indicated that the net efficiency in the jumps without prestretch of the leg extensor muscles (series I) was the lowest (19.4%). In contrast, the net efficiency observed in rebound jumps (series II and III) was respectively 30.8% and 33.1%, demonstrating that the reuse of elastic energy (Wel) plays an important role for muscular work efficiency. However, the contribution of Wel to the total work performed was different p < 0.05, Student's t-test) in jumps on the special panel (41%) compared to the normal surface (37%), even if the total amount of stored elastic energy was the same in both conditions. The different efficiency observed between series II and III was attributed to the compliance of the surface on which the tests were executed. It was suggested that man could change his neuromuscular pattern to adapt muscular behaviour for matching the damped properties shown by the high compliance surface. Finally, the soft surface may favour a very low rate of running injuries.

Adult↗

PubMed1996

Relationships between field fitness test and basal serum testosterone and cortisol levels in soccer players.

The aim of this study was to investigate the existence of a relationship between performance capacities and blood levels of testosterone (T) and cortisol (C). Thirty-two professional soccer players volunteered for the study. Morning levels of hormones were plotted against results of maximal vertical jump with a preparatory counter-movement (CMJ), 30 m running, and Cooper's 12-min running test. The serum T was positively related to both CMJ and average running speed (r=0.43 and r=0.47, respectively). Serum levels of C and T were in negative correlation (r= -0.40 and r= -0.49, respectively) with the results of Cooper's test. It was concluded that athletes with better explosive strength and sprint running performances have a higher basal level of testosterone. The results suggest a relationship between testosterone production and development of fast twitch muscle fibres in athletes.

Adult↗

PubMed1996

Hormonal responses in strenuous jumping effort.

In order to test the possibility for rapid responses of blood hormone levels in short-term supramaximal exercises, serum concentrations of corticotropin (ACTH), cortisol (C), total testosterone (tT), free testosterone (fT), growth hormone (GH), thyrotropin (TSH), free thyroxine (fT4), free triiodothyronine (fT3), prolactin (PRL), insulin-like growth factor (IGF-I), and sex hormone-binding globulin (SHBG) were determined by RIA procedures in blood samples obtained before and immediately after a 60-s period of consecutive vertical jumps (Bosco test). The study subjects were 16 Italian professional soccer players. Immediately after exercise, significant increases (p < 0.05) were found in the concentrations of ACTH (by 39%), C (by 14%), TSH (by 20%), fT3 (by 28%), fT4 (by 30%), tT (by 12%), fT (by 13%), and SHBG (by 21%). Significant changes were not detected in the blood levels of GH, IGF-I and PRL. Most pronounced testosterone responses were typical for persons of high jumping performance (the increase of serum tT correlated with average power output, r = 0.61 and jumping height, r = 0.66). The larger the drop in power output during 60-s jumping, the higher was the thyroid response: the difference in jumping height between the first and last 15-s period correlated with increases in TSH (r = 0.52) and in fT4, (r = 0.55). In conclusion, the obtained results indicate that in intense exercise, causing the rapid development of fatigue, rapid increases in serum levels of hormones of the pituitary-adrenocortical, pituitary-gonadal and pituitary-thyroid systems occur.

Adrenocorticotropic Hormone↗

PubMed1995

A dynamometer for evaluation of dynamic muscle work.

The validation of a new dynamometer for evaluation of dynamic muscle work is presented. The device was based on a precise measurement of load displacements of any machine using gravitational loads as external resistance. It allowed, through a sensor consisting of an infrared photo interrupter, the calculation of velocity, force and power during concentric, eccentric and stretch-shortening cycle activity. To validate the dynamometer 33 male and female track and field athletes (12 throwers and 21 jumpers) participated in the study. The throwers (4 women and 8 men) were asked to perform half-squat exercises on a slide machine with a load of 100% of the subject's body mass. The day-to-day reproducibility of half-squat exercises gave a correlation coefficient of r = 0.88, 0.97 and 0.95 for average push-off force (AF), average push-off velocity (AV), and average push-off power (AP) respectively. Comparison of half-squat measurements was performed against jumping and running test evaluation by the jumpers (7 women and 14 men). The interrelationships among the different variables studied demonstrated a strong correlation between AF, AV and AP and sprinting and jumping parameters (r = 0.53-0.97; P < 0.05-0.001). Using values of AF, AV and AP developed in half-squat exercises executed with different loads, ranging from 35% to 210% of the subject's body mass, it was also possible to establish the force-velocity and power-velocity relationships for both male and female jumpers. In any individual case, the maximal error due to the measurement system was calculated to be less than 0.3%, 0.9% and 1.2% for AF, AV, and AP respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Effect of vertical loading on energy cost and kinematics of running in trained male subjects.

This investigation examined, in a group of 10 trained male runners, the effect of vertical loading during level treadmill running at a velocity of 5 m/s. The net energy cost of running (Cr), the external work of the center of mass of the body (Wext; both expressed in J.kg-1.m-1), and the eccentric-to-concentric ratio (Ecc/Con) of integrated electromyographic activity for the vastus lateralis (VL) and gastrocnemius lateralis muscles were measured. It was observed that Wext and Ecc/Con for the VL could explain a large part of the interindividual variations in Cr. This result reinforces the hypothesis that Ecc/Con could be a good index of effectiveness in the stretch-shortening cycle. When the subjects ran with a vertical load of 9.3% of their body mass, Cr and Wext were significantly reduced (P < 0.01 and P < 0.05, respectively), whereas Ecc/Con for the VL and gastrocnemius lateralis remained unchanged. The variations in Cr and Wext due to vertical loading were significantly correlated (r = 0.75; P < 0.01). It was then concluded that the significant improvement of Cr observed with the added load was mainly due to the fact that Wext was significantly decreased.

Adult↗