Adaptation of the left heart, cerebral and femoral arteries, and jugular and femoral veins during short- and long-term head-down tilt and spaceflights

The objective of this investigation was to identify the major cardiovascular changes induced by exposure to real or simulated 0g (spaceflights: 6, 14, 21 and 25 days, and 6 months; head down tilt, HDT: 10 h, 4, 5, 7, 30 and 42 days), with a minimum of countermeasures. The following cardiovascular data were measured by echocardiography and Doppler ultrasonography: left ventricle end-diastolic volume (LVDV), stroke volume (SV), cardiac output (CO), ejection fraction (EF), middle cerebral artery flow velocity ( ), femoral artery flow velocity ( ), cerebral vascular resistance (R _ca), femoral vascular resistance (R _fa), jugular vein cross-sectional area (A _jv), femoral vein cross-sectional area (A _fv), heart rate (HR), and mean blood pressure (MBP). LVDV remained decreased compared to pre-HDT or pre-flight levels after 1 week of spaceflight or HDT (–8 to –13%, P<0.05), EF did not change. HR tended to increase (5–10%) during spaceflight and HDT, whereas MBP tended to decrease during flight, but did not change in HDT. These findings are consistent with the existence of a moderate and stable hypovolemia. and R _ca fluctuated between +10 and –10% from pre-HDT or pre-flight values, and always showed opposing variations. There was no significant decrease in cerebral perfusion. Lower-limb resistance (R _fa) remained decreased (–5% to –18%, P<0.05) throughout the flights or HDT after week 1. A _jv remained significantly enlarged (+40% P<0.05) after 1 week in spaceflight or in HDT. A _fv was enlarged in spaceflight after week 1 (+15% to +35%, P<0.05), whereas it decreased after 4–5 days of HDT (–20% to –35%, P<0.05). The cardiovascular system reached a new and stable equilibrium during flight and HDT within less than 1 week. With the exception of the femoral vein, there was no significant difference in either the amplitude or the time course of the cardiovascular changes in both situations after 1 week. Electronic Publication     

Effects of fasting and carbohydrate consumption on voluntary resting apnea duration

Breath holding is normally terminated due to the urge to breathe, mainly caused by the increasing carbon dioxide level. It was recently shown that a combination of 18 h of carbohydrate-free diet and prolonged exercise prior to breath holding lowered the respiratory exchange ratio (RER) and end-expiratory PO₂ at maximal breath-hold break-point (MBP). Current hypothesis: fasting will result in longer breath-hold duration than will fasting followed by carbohydrate intake. It was also hypothesized that breath-holds during carbohydrate supplementation would be ended at a higher alveolar PO₂. Ten male non-divers performed multiple breath-holds either to the first diaphragmatic contraction (PBP), or to MBP. The breath-holds were performed during normal diet (control; C), twice during fasting (F14 h, F18 h), followed by post fasting carbohydrate consumption (PFCC) and a repetition of the breath-hold testing 1–2 h after ingestion of carbohydrates. Duration, RER, end-tidal PO₂ and PCO₂, SaO₂ and blood glucose were determined. RER and blood glucose increased after PFCC compared with fasting and control conditions (P < 0.001). PBP breath-hold duration increased from 129 ± 34 s at C to 148 ± 33 s at F18 h, and was reduced during PFCC to 122 ± 30 s (P < 0.001). End-tidal PO₂ was higher at PFCC compared to F18 h (10.4 ± 1.2 vs. 9.5 ± 1.2 kPa at PBP, P < 0.05). Similar trends in breath-hold duration and physiology were seen in breath-holds that were terminated at MBP. Dietary restriction can affect breath-hold duration. The lower O₂ level at breakpoint during fasting suggests that breath holding may be less safe during fasting; the increased risk may be mitigated by ingestion of carbohydrates before breath holding.     

Effect of human head flexion on the control of peripheral blood flow in microgravity and in 1 g

This study evaluated, in six healthy subjects, whether head flexion, which stimulates the vestibular system and the tonic neck receptors, interferes with cardiovascular regulation. Arterial parameters were measured continuously using a pulsed Doppler ultrasound probe during parabolic flights with subjects either in the supine craned-head position (control) or in the supine anterior neck flexion bent-neck position. Exposure to 0 g induced a fluid shift towards the head (stroke volume +8%, P<0.05). Compared to the control situation the mean (SD) blood flow in the femoral artery decreased [ –10 (9)% vs +1 (10)%; P<0.05], and the ratio cerebral artery:femoral artery blood flow ( : ) increased [+8 (14)% vs –4 (7)%; P<0.05], in the bent-neck position. Thus, neck flexion without otolith loading (subject in 0 g) favoured cerebral perfusion during the exposure to 0 g. The return to 1 g, even in the supine position, induced a fluid shift towards the lower limbs. From 0 to 1 g, reduced less [ +6 (8)% vs –1 (8)%; P<0.05], and the : decreased more [–11 (9)% vs 0 (10)%; P<0.05], in the bent-neck position than in the control position. Thus the redistribution of peripheral blood flow in response to the fluid shift towards the legs was less efficient in the bent-neck position. In 0 g environment the passive flexion of the neck (neck receptor stimulation only) increased resistance in the femoral artery [R _fa +20 (21)%; P<0.05] and reduced the [–15(10)%; P<0.07] which increased the redistribution of flow towards the brain [ ; +12 (7)%; P<0.07]. This response was of lower amplitude when both otoliths and neck muscle were stimulated (neck flexion in 1 g) [R _fa+9 (7)%, P<0.05; –9 (12), NS; : 0 (12), NS]. We suggest that otolith and neck muscle stimulation (by neck flexion) trigger opposite vascular effects in response to a fluid shift towards the legs. Electronic Publication     

Analysis of Risk Factors for Ventilator-Associated Pneumonia in a Multidisciplinary Intensive Care Unit

 A prospective study was conducted to determine the incidence, risk factors and pathogens of ventilator-associated pneumonia (VAP) in 198 patients requiring mechanical ventilation for more than 48 hours. VAP occurred in 67 (33.8%) patients. Risk factors associated with VAP were admission APACHE II score >20 (odds ratio [OR] 4.77, 95% confidence interval [CI] 2.04–11.27, P<0.001), mechanical ventilation >10 days (OR 44.4, 95% CI 2.16–26.7, P<0.0001), ICU length of stay >10 days (OR 9.4, 95% CI 3.55–25.65, P<0.0001), and admission PaO₂/FiO₂ ratio <200 mmHg (OR 3.4, 95% CI 1.00–11.41, P<0.05). Logistic regression analysis showed a relationship between VAP and length of stay in ICU, duration of fever and presence of catheter-related infection. The pathogens isolated were predominantly gram-negative bacteria (83.2%), with a high proportion of Acinetobacter spp. (35%) resistant to commonly used antimicrobial agents. The mortality rate was not influenced by VAP.     

Alterations in neuromuscular function and perceptual responses following acute eccentric cycling exercise

Previous investigators have reported velocity-dependent strength loss for single-joint actions following acute eccentric exercise. The extent to which velocity influences recovery of multi-joint function is not well documented. Our main purpose was to compare alterations in maximal cycling power produced across a range of pedaling rates following eccentric exercise. An additional purpose was to determine the extent to which changes in rating of perceived exertion (RPE) associated with submaximal cycling reflect changes in maximal cycling power. Eighteen cyclists performed baseline trials of maximal and submaximal single-leg concentric cycling immediately before and 24 and 48 h after acute submaximal single-leg eccentric (151 ± 32 W, 487 ± 107 s) and concentric (148 ± 21 W, 488 ± 79 s) cycling trials. Maximum cycling power (apex of power–pedaling rate relationship; P _max) was assessed using inertial-load cycling, and powers produced at 65, 110 and 155 rpm were also analyzed. Compared to baseline, P _max was reduced (11–13%) at 24–48 h in the eccentric leg (P < 0.001). Power produced at 65, 110 and 155 rpm was reduced by similar relative magnitudes (11–15%) at 24–48 h in the eccentric leg. RPE increased (15–18%) at 24–48 h in the eccentric leg (P < 0.001). Magnitudes of relative changes in RPE did not differ from those for P _max. There were no alterations in the concentric leg. Our results indicated a global, rather than velocity-specific, reduction in neuromuscular function. Such a global reduction does not support the notion of fiber-type specific damage from eccentric exercise. The similar relative changes in RPE and P _max suggest that increased exertion may reflect the need to recruit additional motor units to produce the same submaximal power.     

Hypoxia and cardiac arrhythmias in breath-hold divers during voluntary immersed breath-holds

The incidence and nature of cardiac arrhythmias during static apnea were studied by monitoring the electrocardiogram (ECG) and oxygen saturation (SaO₂) of 16 recreational breath-hold divers. All subjects completed a maximal apnea with a mean (±SD) breath-hold duration of 281 (±73) s without clinical complications. Both heart rate (HR) and SaO₂ decreased significantly with breath-hold duration. The decline in SaO₂ was inversely related to the decline in HR (r = −0.55, P < 0.05). Cardiac arrhythmias (supraventricular and ventricular premature complexes, right bundle branch block) occurred in 12/16 (77%) subjects and were related to breath-hold duration. Subjects with atrial premature complexes (n = 9) had a reduced BMI (P = 0.016) and a higher decline of the terminal SaO₂ (P = 0.01). In conclusion, ectopic arrhythmias were common during maximal static apneas for training purposes. The results indicate that the occurrence of ectopic beats is associated with individual factors such as the tolerable SaO₂ decrease.     

Interleukin-18 and its three gene polymorphisms relating to allergic rhinitis

The study aimed to examine an association of three different single nucleotide polymorphisms (SNPs) of the IL-18 gene (−607 C/A, −137 G/C and −133 C/G) on chromosome 11q22 with allergic rhinitis (AR). Genotyping for the SNPs was performed using 539 patients with AR and 312 healthy control volunteers. Positivity to the skin prick test for the fungus Alternaria sp. in patients with AR, and IgE levels according to particular genotypes of selected SNPs, were also determined. There were no significant differences in the distribution of single IL-18 alleles or genotypes between controls and AR patients. However, frequencies of combined IL-18 genotypes arising from combinations of the three common polymorphisms (−607, −137 and −133) were significantly different between both groups (P = 0.009, P _corr < 0.05, OR = 5.35, 95% CI: 1.9–15.2). There was a marginally significant association of the IL-18–607 variant with IgE levels (P = 0.05) in patients, but not in the case of the other SNPs. Patients allergic to Alternaria, but not those allergic to other antigens, showed a significant association with the IL-18–607 polymorphism (P = 0.0037, P _corr < 0.05). Results suggest that IL-18 gene variants may be one of the factors participating in the pathogenesis of AR or its intermediary phenotypes.     

Cardiac, arterial and venous adaptation to weightlessness during 6-month MIR spaceflights with and without thigh cuffs (bracelets)

The objectives of this investigation were to study the effects of thigh cuffs (bracelets) on cardiovascular adaptation and deconditioning in 0 g. The cardiovascular parameters of six cosmonauts were measured by echocardiography, Doppler, and plethysmography, during three 6-month MIR spaceflights. Measurements were made at rest during preflight (−30 days), inflight (1, 3–4, and 5–5.5 months) without cuffs (morning) and after 5 h with cuffs, and during postflight (+3 and +7 days). Lower-body negative pressure (LBNP) measurements were performed 1 day after each resting session. Inflight values of left ventricle end-diastolic volume and stroke volume measured without the thigh cuffs (−8 to −24% and −10 to −16%, respectively, both P < 0.05) were lower than corresponding preflight values. The jugular and femoral vein cross-sectional areas (A _jv and A _fv, respectively) were enlarged (A _jv: by 23–30%, P < 0.001; A _fv: by 33–70% P < 0.01). The renal and femoral vascular resistances (R _ra and R _fa, respectively) decreased (R _ra: by −15 to −16%, P < 0.01; R _fa: by −5 to −11%, P < 0.01). Inflight, the thigh cuffs reduced the A _jv (by −12 to −20%, P < 0.02), but enlarged the A _fv (A _fv: by 9–20%, P < 0.02) and increased the vascular resistance (R _ra: by 8–13%, P < 0.05; R _fa: by 10–16%, P < 0.01) compared to corresponding inflight, without-cuffs values. During LBNP (−45 mmHg, where 1 mmHg=133.3 N/m²), R _fa and the ratio between cerebral and femoral blood flow (Q˙ _ca/Q˙ _fa) increased less inflight and postflight (+25% for R _fa and +30% for Q˙ _ca/Q˙ _fa) than during preflight (60% for R _fa and 75% for Q˙ _ca/Q˙ _fa, P < 0.01). This reduced vasoconstrictive response and less efficient flow redistribution toward the brain was associated with orthostatic intolerance during postflight stand tests in all of the cosmonauts. The calf circumference increased less inflight and postflight (6% P < 0.05) than preflight (9% P < 0.05). The vascular response to LBNP remained similarly altered throughout the flight. The thigh cuffs compensated partially for the cardiovascular changes induced by exposure to 0 g, but did not interfere with 0 g deconditioning. Accepted: 5 November 1999     

Relationship between the blood thyroid hormones and lipid profile in Moghani sheep; influence of age and sex

The aim of this study was to determine the correlation between thyroid hormones and lipid profile in blood of Iranian Moghani sheep in different ages and sexes. Blood samples were taken from the jugular vein of 260 clinically healthy and nonpregnant animals in eight age groups (1–14 days, 1–2, 2–3, 3–6, 6–12, 12–24, 24–48, and  > 48 months) in autumn. The plasma was analyzed to determine thyroxine (T₄), triiodothyronine (T₃), free thyroxine (fT₄), free triiodothyronine (fT₃), cholesterol, triglyceride, high-density lipoprotein (HDL-cholesterol), low-density lipoprotein (LDL-cholesterol) and very low-density lipoprotein (VLDL-cholesterol) concentrations. According to our data from Moghani sheep, an increase in age results in significant decreases in the plasma concentrations of T₄, T₃, fT₄, fT₃, cholesterol, and HDL-cholesterol (P < 0.05) but no gender-dependent significant differences in the studied parameters were found.     

Effect of altitude training on serum creatine kinase activity and serum cortisol concentration in triathletes

In this investigation we evaluated the effect of a 5-week training program at 1860 m on serum creatine kinase (CK) activity and serum cortisol concentration in national-caliber triathletes for the purpose of monitoring the response to training in a hypobaric hypoxic environment. Subjects included 16 junior-level female (n = 8) and male (n = 8) triathletes who were training for the International Triathlon Union (ITU) World Championships. After an initial acclimatization period, training intensity and/or volume were increased progressively during the 5-week altitude training camp. Resting venous blood samples were drawn at 0700 hours following a 12-h overnight fast and were analyzed for serum CK activity and serum cortisol concentration. Subjects were evaluated before [7–10 days pre-altitude (SL 1)] and after [7–10 days post-altitude (SL 2)] the 5-week training camp at 1860 m. At altitude, subjects were evaluated within 24–36 h after arrival (ALT 1), 7 days after arrival (ALT 2), 18 days after arrival (ALT 3), and 24–36 h prior to leaving the altitude training camp (ALT 4). A repeated-measures analysis of variance was used to evaluate differences over time from SL 1 to SL 2. Compared to SL 1, serum CK activity increased approximately threefold (P < 0.05) within the initial 24–36 h at altitude (ALT 1), and increased by an additional 70% (P < 0.05) after the 1st week of altitude training (ALT 2). Serum CK activity remained significantly elevated over the duration of the experimental period compared to pre-altitude baseline levels. Serum cortisol concentration was increased (P < 0.05) at the end of the 5-week altitude training period (ALT 4) relative to SL 1, ALT 1 and ALT 3. These data suggest that: (1) the initial increase in serum CK activity observed in the first 24–36 h at altitude was due primarily to acute altitude exposure and was independent of increased training intensity and/or training volume, (2) the subsequent increases in serum CK activity observed over the duration of the 5-week altitude camp were probably due to the combined effects of altitude exposure and increased training load, and (3) the increase in serum cortisol concentration observed at the end of the altitude training camp reflects the additive effect of 5 weeks of altitude exposure in combination with a progressively increased training intensity and/or volume. Accepted: 5 June 1999     

Dynamic cerebral autoregulation assessment using chaotic analysis in diabetic autonomic neuropathy

Cerebral autoregulation (CA) was assessed by chaotic analysis based on mean arterial blood pressure (MABP) and mean cerebral blood flow velocity (MCBFV) in 19 diabetics with autonomic neuropathy (AN) and 11 age-matched normal subjects. MABP in diabetics dropped significantly in response to tilting (91.6 ± 14.9 vs. 74.1 ± 13.4 mmHg, P < 0.05). Valsalva ratio of heart rate was reduced in diabetics compared to normal (1.1 ± 0.1 vs. 1.5 ± 0.2, P < 0.05). It indicated AN affects the vasomotor tone of peripheral vessels and baroreflex. Nonlinear results showed higher correlation dimension values of MABP and MCBFV in diabetics compared to normal, especially MABP (3.7 ± 2.3 vs. 2.0 ± 0.8, P < 0.05). It indicated CA is more complicated in diabetics. The lower Lyapunov exponent and the higher Kolmogorov entropy values in diabetics indicated less predictable behavior and higher chaotic degree. This study suggests impaired autoregulation would be more chaotic and less predictable.     

Evaluation of the limits to accurate sweat loss prediction during prolonged exercise

Sweat prediction equations are often used outside their boundaries to estimate fluid requirements and generate guidance. The limitations associated with these generalized predictions have not been characterized. The purposes of this study were to: (1) evaluate the accuracy of a widely used sweat prediction equation (SHAP) when widening it’s boundaries to include cooler environments (2 h) and very prolonged exercise (8 h), (2) determine the independent impact of holding skin temperature constant (SHAP₃₆), and (3) describe how adjustments for non-sweat losses (NSL) and clothing saturation dynamics affect prediction accuracy. Water balance was measured in 39 volunteers during 15 trials that included intermittent treadmill walking for 2 h (300–600 W, 15–30°C; n = 21) or 8 h (300–420 W, 20–40°C; n = 18). Equation accuracy was assessed by comparing actual and predicted sweating rates (211 observations) using least-squares regression. Mean and 95% confidence intervals for group differences were compared against a zone of indifference (±0.125 l/h). Sweating rate variance accounted for by SHAP and SHAP₃₆ was always high (r ² > 0.70), while the standard error of the estimate was small and uniform around the line of best fit. SHAP errors were >0.125 l/h during 2 and 8 h of exercise. SHAP₃₆ errors were <0.125 l/h for 2 h conditions but were higher at 8 h in three of the six warmest trials. Adjustments for NSL and clothing saturation dynamics help explain SHAP errors at 2 and 8 h, respectively. These results provide a basis for future development of accurate algorithms with broader utility.     

Tactile input of the hand and the control of reaching to grasp movements

Phosphorus magnetic resonance spectroscopy (³¹P MRS) was used to determined whether focal cerebral injury caused by unilateral carotid artery occlusion and graded hypoxia in developing rats led to a delayed impairment of cerebral energy metabolism and whether the impairment was related to the magnitude of cerebral infarction. Forty-two 14-day-old Wistar rats were subjected to right carotid artery ligation, followed by 8% oxygen for 90 min. Using a 7T MRS system,³¹P brain spectra were collected during the period from before until 48 h after hypoxia-ischaemia. Twenty-eight control animals were studied similarly. In controls, the ratio of the concentration of phosphocreatine ([PCr]) to inorganic orthophosphate ([Pi]) was 1.75 (SD 0.34) and nucleotide triphosphate (NTP) to total exchangeable phosphate pool (EPP) was 0.20 (SD 0.04): both remained constant. In animals subjected to hypoxia-ischaemia, [PCr] to [Pi] and [NTP] to [EPP] were lower in the 0- to 3-h period immediately following the insult: 0.87 (0.48) and 0.13 (0.04), respectively. Values then returned to baseline level, but subsequently declined again: [PCr] to [Pi] at −0.02 h⁻¹ (P<0.0001). [PCr] to [Pi] attained a minimum of 1.00 (0.33) and [NTP] to [EPP] a minimum of 0.14 (0.05) at 30–40 h. Both ratios returned towards baseline between 40 and 48 h. The late declines in high-energy phosphates were not associated with a fall in pH_i. There was a significant relation between the extent of the delayed impairment of energy metabolism and the magnitude of the cerebral infarction (P<0.001). Transient focal hypoxia-ischaemia in the 14-day-old rat thus leads to a biphasic disruption of cerebral energy metabolism, with a period of recovery after the insult being followed by a secondary impaiment some hours later.     

The use of magnetic resonance imaging to evaluate the effects of cooling on skeletal muscle after strenuous exercise

The purpose of this study was to investigate the separate effects of cooling during the acute (within 60 min post-exercise) or subacute (24–168 h post-exercise) phase on skeletal muscle after exercise. Twenty-eight male subjects [mean (SD) 23.8 (1.8) years] were randomly assigned to the control (COTG, n=10), cold-water immersion (CWIG, n=9), and double-cold-water immersion groups (DCWIG, n=9). The cold-water immersion (15 min) was administered to the subjects' legs after calf-raise exercise (CWIG: after recording initial post-exercise measures, DCWIG: after recording initial and 24 h post-exercise measures). Magnetic resonance T2-weighted images were obtained to calculate the T2 relaxation time (T2) of the triceps surae muscle before, immediately after, and at the following times post-exercise: 20, 40, and 60 min, and 24, 48, 96 and 168 h. In addition, the ankle joint range of motion, serum creatine kinase and lactate dehydrogenase, and muscle soreness level were investigated before and after exercise. In all groups, significant T2 elevations in the gastrocnemius muscle appeared from immediately after to 60 min after exercise (P<0.05). Thereafter, COTG showed significantly re-elevated T2 levels in the gastrocnemius at 96–168 h post-exercise (P<0.05), while CWIG and DCWIG showed significantly smaller T2 values than the COTG at 96 h post-exercise (P<0.05). In addition, COTG showed larger increases in serum enzymes at 96 h post-exercise (not significant) and significantly greater muscle soreness levels at 48 h post-exercise (P<0.05) than the cooling groups. The results of this study may suggest that cooling has no dramatic effect, but some minor effects on reducing exercise-induced muscle edema in the subacute phase and relieving the extent of the damaged muscle cells. Electronic Publication     

Maximal voluntary contraction force,SR function and glycogen resynthesis during the first 72 h after a high-level competitive soccer game

The aim of this study was to examine maximal voluntary knee-extensor contraction force (MVC force), sarcoplasmic reticulum (SR) function and muscle glycogen levels in the days after a high-level soccer game when players ingested an optimised diet. Seven high-level male soccer players had a vastus lateralis muscle biopsy and a blood sample collected in a control situation and at 0, 24, 48 and 72 h after a competitive soccer game. MVC force, SR function, muscle glycogen, muscle soreness and plasma myoglobin were measured. MVC force sustained over 1 s was 11 and 10% lower (P < 0.05) after 0 and 24 h, respectively, compared with control. The rate of SR Ca²⁺ uptake at 800 nM [Ca²⁺]_free was lower (P < 0.05) after 0 h (2.5 μmol Ca²⁺ g prot⁻¹ min⁻¹) than for all other time points (24 h: 5.1 μmol Ca²⁺ g prot⁻¹ min⁻¹). However, SR Ca²⁺ release rate was not affected. Plasma myoglobin was sixfold higher (P < 0.05) immediately after the game, but normalised 24 h after the game. Quadriceps muscle soreness (0–10 VAS-scale) was higher (P < 0.05) after 0 h (3.6), 24 h (1.8), 48 h (1.1) and 72 h (1.4) compared with control (0.1). Muscle glycogen was 57 and 27% lower (P < 0.001) 0 and 24 h after the game compared with control (193 and 328 vs. 449 mmol kg d w⁻¹). In conclusion, maximal voluntary contraction force and SR Ca²⁺ uptake were impaired and muscle soreness was elevated after a high-level soccer game, with faster recovery of SR function in comparison with MVC force, soreness and muscle glycogen.     

Effect of water ingestion on cardiovascular and thermal responses to prolonged cycling and running in humans: a comparison

The aim of this investigation was to examine the effect of water ingestion on physiological responses to prolonged cycling (CYC) and running (RUN). A group of 11 men with mean (SEM) maximal oxygen uptake (V˙O_2max) 48.5 (1.8) ml·kg^–1·min^–1 on a cycle-ergometer and 52.1 (2.2) ml·kg^–1·min^–1 on a treadmill (P<0.01) exercised for 90 min on four occasions, twice on each ergometer, at 60% of mode specific V˙O_2max. No fluid was taken (D) in one trial on each ergometer, whereas 60% of fluid losses were replaced by drinking water in the other trial (W). In CYC, water ingestion attenuated the change in cardiac output ( ) and the reduction in stroke volume (ΔSV) [ΔSV: –22.7 (3.8) in D, –10.7 (2.9) ml·beat^–1 in W, P<0.01; : –1.9 (0.5) in D, –0.2 (0.4) l·min^–1 in W at 85 min, P<0.01], but did not affect rectal temperature [T _re at 90 min: 38.8 (0.1)°C in D, 38.7 (0.1)°C in W]. In contrast, fluid replacement reduced hyperthermia in RUN [T _re at 90 min: 39.6 (0.2) in D, 39.1 (0.2)°C in W, P<0.01], and this was linked with a higher skin blood flow [RUN-W 88.9 (8.5), RUN-D 70.7 (8.4)%, P<0.05]. The and ΔSV were also attenuated with water ingestion in this mode of exercise (P<0.05). It is concluded that water ingestion improves physiological function in both cycling and running, but that the underlying mechanism is different in the two modes of exercise. Electronic Publication     

Alterations in the expression and activity of creatine kinase-M and mitochondrial creatine kinase subunits in skeletal muscle following prolonged intense exercise in rats

Creatine kinase (CK) isoenzymes are important structural and energy metabolism components in skeletal muscle. In this study, CK isoenzyme alterations were examined in male rats, with an 8% body mass weight attached to their tail. The rats were either forced to swim for 5 h (5S, n = 51), or were pre-trained for 8 days and then forced to swim for 5 h (T5S, n = 48). Rats were sacrificed either immediately (0 h PS), 3 h (3 h PS), or 48 h post-swimming (48 h PS). Serum CK was increased significantly (P < 0.01) 6.2- and 2.0-fold at 0 h PS following the 5S and T5S protocols, respectively. However, training (T5S protocol) significantly (P < 0.01) decreased CK release. Soleus and white gastrocnemius (WG) CK activity was significantly decreased following the 5S protocol (P < 0.05), but not following the T5S protocol. The CK-M activity of the soleus muscle was significantly (P < 0.05) decreased at 0 h PS following both the 5S and T5S protocols, and returned to control values at 3 h PS. The CK-M activity of the WG was significantly (P < 0.05) decreased at 0 h PS following the 5S protocol. Sarcomeric mitochondrial CK (sCK-Mit) was decreased significantly (P < 0.01) at 0 h PS (20%), 3 h PS (14%), 24 h PS (22%), and 48 h PS (15%) following the 5S protocol. However, sCK-Mit was decreased significantly (P < 0.01) only at 0 h PS (7%) following the T5S. The results of this study demonstrate that prolonged intense exercise causes a loss of skeletal muscle CK-M and sCK-Mit activity and that training prior to the prolonged intense exercise attenuates the exercise-induced CK-M and sCK-Mit loss in both red and white skeletal muscles. Accepted: 18 July 1999     

Relationship between plasma thyroid hormones and some biochemical parameters in Iranian Sarabi calves

The thyroid gland has some important endocrine hormones that regulate basal metabolism in various tissues of domestic animals. Thyroid hormones have a central role in animals’ development and their tissue functions. In this study, the relationship between the plasma thyroxine (T₄), triiodothyronine (T₃), free thyroxine (fT₄), free triiodothyronine (fT₃), triglyceride, cholesterol, glucose, total protein, and albumin concentrations as well as albumin/globulin ratio in different ages of Iranian Sarabi calves was investigated. Blood samples were collected from the jugular vein of 47 clinically healthy calves free from internal and external parasites (grouped according to their age—1–14 days, 1–2, and 3–6 months) in early of winter. The level of thyroid hormones was determined by chemiluminescence, and other parameters were measured by spectrophotometry using commercial kits. Our data from this study indicates that there was no significant difference and correlation in all the studied parameters between age groups and sexes. But we found a significant correlation between plasma T₄ and total protein (P < 0.05, r = 0.600), T₄ and albumin (P < 0.05, r = 0.575), T₃ and fT₃ (P < 0.05, r = 0.610), T₃ and total protein (P < 0.01, r = 0.725), T₃ and glucose (P < 0.01, r = 0.685), and fT₄ and fT₃ (P < 0.05, r = 0.609) concentrations as well as between total protein and albumin/globulin ratio (P < 0.01, r = −0.783).     

Relationship between side medicine-ball throw performance and physical ability for male and female athletes

The purpose of the study was to examine the factors contributing to performance of a side medicine-ball throw (S-MBT) and a fast side medicine-ball throw (FS-MBT) and to analyze some of the factors which account for the difference in side medicine ball throw performance between the sexes. Sixteen males and ten females were evaluated by S-MBT, FS-MBT, isometric maximal trunk rotation torque (IMTRT), One repetition maximum of Parallel Squat (1RM_PS) and Bench Press (1RM_BP), Bench Press peak power (BP_PP), Static Squat Jump peak power (SSJ_PP) and vertical jump height. Males demonstrated significantly greater scores than females in all measurements. Significant correlations were observed in males, but not in females, between the distances during S-MBT and the IMTRT values (r = 0.596–0.739, P < 0.05–0.01) and the 1RM_PS values (r = 0.683–0.725, P < 0.01). In FS-MBT performance, significant correlations were observed in males, but not in females, between the ball velocity values during FS-MBT and the IMTRT values (r = 0.611–0.687, P < 0.05–0.01), 1RM_BP values (r = 0.596–0.655, P < 0.05–0.01) and 1RM_PS values (r = 0.679–0.718, P < 0.01). These results suggested that the contributing factors of S-MBT and FS-MBT performance were deferent in males and females. Hence, the side medicine-ball throw test would be useful to examine the trunk rotation power of male athletes, but may have a limited potential as a predictor of trunk rotation power for female athletes.     

Effects of long-term training specificity on maximal strength and power of the upper and lower extremities in athletes from different sports

Maximal concentric one repetition maximum half-squat (1RM_HS), bench-press (1RM_BP), power-load curves during concentric actions with loads ranging from 30% to 100% of 1RM_HS and 1RM_BP were examined in 70 male subjects divided into five groups: weightlifters (WL, n=11), handball players (HP, n=19), amateur road cyclists (RC, n=18), middle-distance runners (MDR, n=10) and age-matched control subjects (C, n=12). The 1RM_HS values in WL, HP and RC were 50%, 29% and 28% greater, respectively, (P<0.001–0.01) than those recorded for MDR and C. The half-squat average power outputs at all loads examined (from 30% to 100%) in WL and HP (P<0.001 at 45% and 60% with HP) were higher (P<0.05–0.001) than those in MDR, RC and C. Average power output at the load of 30% of 1RM_HS in RC was higher (P<0.05) than that recorded in MDR and C. Maximal power output was produced at the load of 60% for HP, MDR and C, and at the load of 45% for WL and RC. The 1RM_BP in WL was larger (P<0.05) than those recorded in HP, RC, MDR and C. In the bench press, average muscle power outputs in WL and HP were higher (P<0.05–0.001) than those in MDR, RC and C, and were maximized at a load of 30% of 1RM for WL and HP, and at 45% for RC, MDR and C. In addition, the velocities that elicited the maximal power in the lower extremities were lower (≈0.75 m·s^–1) than those occurring in the upper extremities (≈1 m·s^–1). The data suggest that the magnitude of the sport-related differences in strength and/or muscle power output may be explained in part by differences in muscle cross-sectional area, fibre type distribution and in the muscle mechanics of the upper and lower limbs as well as by training background. Electronic Publication