Comparative study on determination of plasma thyroid hormones by chemiluminescence and electrochemiluminescence immunoassay methods in sheep

The aim of this study was to compare plasma thyroid hormone concentrations by both chemiluminescence (CLIA) and electrochemiluminescence immunoassay (ECLIA) methods in sheep. Blood samples were taken from the jugular vein of 25 clinically healthy, non-pregnant adult ewes. The plasma was analyzed to determine thyroxine (T₄), tri-iodothyronine (T₃), free thyroxine (fT₄) and free tri-iodothyronine (fT₃) concentrations. The data from this study indicates, there were significant differences in the T₄ (P < 0.0001), T₃(P < 0.01) and fT₃(P < 0.01) concentrations between the two methods, and the levels of these hormones were higher when using the ECLIA method. In determining thyroid hormones using the CLIA and ECLIA methods, significant positive correlations were found between T₄ and fT₄ (P < 0.001, r = 0.703; P < 0.0001, r = 0.806) also between T₃ and fT₃ (P < 0.0001, r = 0.922; P < 0.0001, r = 0.923) concentrations, respectively. The linear regression analysis of these hormones showed that the CLIA and ECLIA results were significantly correlated (T₄ (P < 0.01, r = 0.583), T₃ (P < 0.0001, r = 0.898), fT4 (P < 0.0001, r = 0.796) and fT₃ (P < 0.0001, r = 0.898).     

Comparative study on the determination of serum thyroid hormones by two methods of immunoassay in broiler breeder poultry

Variations in blood thyroid hormone concentrations give an indirect indication of changes in thyroid gland activity; therefore, selecting a suitable method to determine these hormones is crucial. The aim of this study was to compare serum thyroid hormone concentrations (i.e. T₄, T₃, fT₄ and fT₃) using chemiluminescence immunoassay (CLIA) and enzyme-linked immunosorbent assay (ELISA) methods in broiler breeders. This study was carried out on 30 blood samples from randomly selected 45-week-old broiler breeders. Blood samples were collected in summer from the wing vein of birds by using disposable syringes. The separated serum was analysed to determine thyroxine (T₄), triiodothyronine (T₃), free thyroxine (fT₄) and free triiodothyronine (fT₃) concentrations using the mentioned methods. Data were processed in excel and statistical analysis was carried out using SPSS/ver17 software. Our data from this study indicates there was a significant difference in the T₄ (P < 0.0001), fT₄ (P < 0.01) and fT₃ (P < 0.05) concentrations between the two methods and that the levels of these hormones were higher when using the CLIA method, except for fT₃. The linear regression analysis of these hormones showed that the CLIA and ELISA results were significantly correlated only for fT₄ (P < 0.0001, r = 0.798) concentration. In conclusion, determination of the thyroid hormones using the CLIA method had an acceptable performance of higher sensitivity and precision and was more appropriate than the ELISA method for clinical application and investigation in poultry.     

Thyroid hormones and their correlations with serum glucose, beta hydroxybutyrate, nonesterified fatty acids, cholesterol, and lipoproteins of high-yielding dairy cows at different stages of lactation cycle

The relationships between circulating thyroid hormones and serum glucose, beta hydroxybutyrate (BHB), nonesterified fatty acid (NEFA), cholesterol and lipoproteins of high-yielding dairy cows were studied in 125 adult Holsteins at various stages of lactation cycle: early (far-off) dry period (n = 24), late (close-up) dry period (n = 10), fresh cows (n = 22), early lactation (n = 13), mid-lactation (n = 27) and late lactation (n = 29). Decreased levels of thyroxin (T₄) and triiodothyronine (T₃) were noted in peripartum cows which were extended to mid- and late-lactation cows, respectively. In fresh cows, glucose showed correlations with T₄ (r = 0.619, P < 0.01) and T₃ (r = 0.627, P < 0.01). In the same cows there were correlations between T₄ and BHB (r = 0.590, P < 0.01) and NEFA (r = 0.470, P < 0.01). In late dry cows, free thyroxin (fT₄) showed correlations with triglyceride (TG) and very-low-density lipoprotein (VLDL; r = −0.638, P < 0.05). Pooled data of the various stages of lactation cycle revealed correlations between glucose and T₄ (r = 0.20, P < 0.05), glucose and T₃ (r = 0.395, P < 0.01), cholesterol and T₃ (r = −0.201, P < 0.05), and free triiodothyronine (fT₃) and high-density lipoprotein (HDL; r = 0.178, P < 0.05). It appears that the time and the pattern of changes and/or correlations of serum thyroid hormones and lipid fractions may vary among dairy cows and other animals.     

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.     

Influence of sympatho-vagal balance on airway responsiveness in athletes

The increased prevalence of airway hyper-responsiveness (AHR) observed among athletes suggests that high-level training may contribute to the development of AHR. We investigated the possible influence of the sympatho-vagal balance on this phenomenon in 40 athletes and 10 sedentary controls. Each subject filled out a respiratory questionnaire, had a methacholine challenge, and measurements were made of their baseline plasma catecholamines [epinephrine (E), norepinephrine (NE) and dopamine (DA)] as a reflection of sympathetic tone, and their heart rate variability (SDNN: standard deviation of all normal-to-normal intervals) as an indicator of parasympathetic tone. The athletes had a 45% prevalence of AHR (defined as PC₂₀ < 16 mg/ml, where PC₂₀ is the concentration of methacholine inducing a 20% fall in the forced expiratory volume in 1 s, FEV₁) with a mean PC₂₀ of 21.2 mg/ml compared with 10% prevalence (mean PC₂₀: 74.4 mg/ml) in sedentary subjects (P < 0.01). Plasma catecholamine values were not significantly different between the two groups (all P > 0.05), but the estimated parasympathetic tone was higher in athletes (P=0.01). When data from all subjects were analyzed together, plasma E and NE correlated with PC₂₀ (r=0.39, P=0.005 and r=0.29, P < 0.005) but DA and SDNN did not (both P > 0.05). However, the ratios E/SDNN, NE/SDNN and DA/SDNN showed significant correlations with PC₂₀ (r=0.42, P < 0.01; r=0.33, P < 0.005 and r=0.31, P < 0.05, respectively). This study suggests that the sympatho-vagal balance may contribute to the increased AHR in the population studied but this influence alone cannot explain the higher prevalence of AHR in athletes. Accepted: 26 July 2000     

Benefit of endurance training in elderly people over a short period is reversible

 The present study assessed daily activity, physical capacity and body composition in 11 initially sedentary healthy subjects [5 men and 6 women, mean age 62.8 (SD 2.7) years] before training (T_o), after completion of 7 (T_7w) and 14 (T_14w) weeks of training, and again 6 (T_6m) and 12 (T_12m) months after training. The mean daily activity index decreased from T_7w to T_12m reaching a lower level than at T_o [T_12m − T_o = −1.5 (SD 4.6) units, P = 0.18]. Mean maximal oxygen uptake (V˙O_2max) and its corresponding mean power output (W˙ _max) were increased by 12.5 (SD 6.6)% (P = 0.003) and 22.8 (SD 12.8)% (P = 0.003), respectively, at T_14w, and returned to their T_o levels within 1 year. Mean body mass (m _b) remained stable until T_6m but increased significantly by 2.6 (SD 3.7)% from T_6m to T_12m (P < 0.05). Mean fat mass (m _f, from bioelectrical impedance analysis measurements) tended to decrease [−2.0 (SD 4.2)%, P = 0.10] during the training period but increased by 7.8 (SD 10.9)% between T_6m and T_12m (P < 0.05). The mean fat free mass did not vary during the study period (P = 0.81) but magnetic resonance imaging (MRI) showed that mean thigh muscle volume decreased between T_7w and T_12m to less than at T_o [T_12m − T_o = −2.3 (SD 3.6)%, P = 0.05]. Therefore, this study confirmed the favourable effects of endurance training on the physical capacity and body composition of elderly people, but demonstrated that the training programme would have to be continued to maintain the training-related benefits (i.e. increased V˙O_2max and W˙ _max) which would otherwise be lost within 1 year. After training, m _b and m _f were found to be increased. Furthermore, a fast and reproducible MRI protocol was validated for study of small intra-individual variations in tissue volumes in longitudinal studies. Accepted: 7 September 1999     

Serum lipid profiles and their correlation with thyroid hormones in clinically healthy Turkoman horses

 Blood samples were collected from the jugular vein of 50 clinically healthy Turkoman horses according to their age (2–3, 3–5 and >5 years) and sex. Variations in the serum concentrations of cholesterol, triglyceride, total lipid, very low-density lipoprotein (VLDL cholesterol), low-density lipoprotein (LDL cholesterol) and high-density lipoprotein (HDL cholesterol), and their correlations with the concentrations of triiodothyronine (T₃) and thyroxine (T₄) were investigated. With an increase in the age of animals, there were significant increases (p=<0.05) in the cholesterol, triglyceride, total lipid, HDL cholesterol, LDL cholesterol and VLDL cholesterol concentrations. However, sex showed no significant differences on the concentrations of these parameters. The concentrations of T₃ and T₄ were significantly different in male and female Turkoman horses (p=<0.05). There were no significant correlations between thyroid hormones (T₃ and T₄) and serum lipids and cholesterol concentations in lipoproteins. Received: 11 June 2002 / Accepted: 6 November 2002     

Association between serum cortisol and progesterone concentrations and the infiltration of immune cells in the endometrium of gilts with vaginal discharge

The objective of the study was to investigate an association between serum cortisol and progesterone (P₄) concentrations and the distribution of immune cells in the endometrium of the gilts with vaginal discharge. Genital organs from 39 Landrace×Yorkshire crossbred gilts culled owing to vaginal discharge problem were collected from two commercial swine herds in Thailand. The estrous stage and gross pathology were examined. Blood samples were collected from the jugular vein prior to being slaughtered. Serum P₄ and cortisol were analyzed by means of enzyme immunoassay. The samples observed were in inactive (n = 4), follicular (n = 10), and luteal (n = 25) phases. They, afterwards, were processed in hematoxylin and eosin sections. The endometrium of the gilts was histologically divided into three layers, i.e., epithelial, subepithelial connective tissue, and glandular connective tissue layers. Immune cells, i.e., lymphocytes, neutrophils, eosinophils, macrophages, and plasma cells, in each layer were quantified under a light microscope (×400). The results revealed that mean serum cortisol was 430.6 ± 68.3 nmol/l. Serum P₄ varied by ovarian status. Serum P₄ of the gilts in the luteal phase was higher than those in the follicular phase (88.3 ± 7.7 versus 20.6 ± 6.2 nmol/l, P < 0.05). As for the endometrium condition, the gilts were classified into acute/subacute endometritis (n = 13), chronic endometritis (n = 9), and normal endometrium (n = 17). Neutrophils were the main local immune cells in the epithelial layer. Lymphocytes were the dominant population in the subepithelial and glandular connective tissue layers. Generally, the serum cortisol tended to negatively correlate with lymphocytes in the subepithelial connective tissue layer (r = −0.28, P = 0.081). In the gilts with acute/subacute endometritis, no correlation among serum cortisol, P₄, and immune cells was observed. In chronic endometritis gilts, only a negative correlation was remarked between P₄ and epithelial lymphocytes (r = −0.83, P = 0.010), epithelial neutrophils (r = −0.79, P = 0.019), and subepithelial neutrophils (r = −0.73, P = 0.025). In the gilts with normal endometrium, P₄ negatively correlated with subepithelial neutrophils (r = −0.55, P = 0.022) while positively correlated with subepithelial macrophages (r = 0.54, P = 0.024) and subepithelial eosinophils (r = 0.60, P = 0.011).     

Physiological predictors of flat-water kayak performance in women

This study was conducted to investigate the relationship between selected physiological variables and 500-m flat-water kayak (K₅₀₀) performance. Nine female, high-performance kayak paddlers, mean (SD) age 23 (5) years, participated in this investigation. Testing was conducted over 6 days and included anthropometric measurements (height, body mass and skinfolds), an incremental test to determine both peak V˙O₂ and the “anaerobic threshold” (Th_an), and a 2-min, all-out test to calculate accumulated oxygen deficit (AOD). Blood lactate concentrations were measured during the incremental test and at the completion of both tests. Subjects also completed a K₅₀₀ race under competition conditions. K₅₀₀ time was significantly correlated with both peak V˙O₂ (r=−0.82, P < 0.05) and the power output achieved at the end of the incremental test (r=−0.75, P < 0.05). However, the variable most strongly correlated with K₅₀₀ time was Th_an (r=−0.89, P < 0.05). A stepwise multiple regression, for which r=0.95 and the standard error of estimate=1.6 s, yielded the following equation: K₅₀₀time(s)=160.60.154×AOD·kg⁻¹−0.250 × Th_an. In conclusion, the results of this study have demonstrated that although K₅₀₀ performance is a predominantly aerobic activity, it does require a large anaerobic contribution. The importance of both the aerobic and anaerobic energy systems is reflected by the K₅₀₀ time being best predicted by a linear combination of Th_an and AOD · kg⁻¹. This suggests the need to develop and implement training programmes that develop optimally both of these physiological attributes. Further research is required to elucidate the most effective means by which to develop both the aerobic and anaerobic energy systems. Accepted: 29 December 1999     

Relevance of individual characteristics for thermoregulation during exercise in a hot-dry environment

The aim of this study was to investigate the relevance of individual characteristics for thermoregulation during prolonged cycling in the heat. For this purpose, 28 subjects cycled for 60 min at 60% VO_2peak in a hot-dry environment (36 ± 1°C; 25 ± 2% relative humidity, airflow 2.5 m/s). Subjects had a wide range of body mass (99–43 kg), body surface area (2.2–1.4 m²), body fatness (28–5%) and aerobic fitness level (VO_2peak = 5.0–2.1 L/min). At rest and during exercise, rectal and mean skin temperatures were measured to calculate the increase in body temperature (ΔT _body) during the trial. Net metabolic heat production (M _NET) and potential heat loss (by means of evaporation, radiation and convection) were calculated. Although subjects exercised at the same relative intensity, ΔT _body presented high between-subjects variability (range from 0.44 to 1.65°C). ΔT _body correlated negatively with body mass (r = −0.49; P < 0.01), body surface area (r = −0.47; P < 0.01) and T_body at rest (r = −0.37; P < 0.05), but it did not significantly correlate with body fatness (r = 0.12; P > 0.05). ΔT _body positively correlated with the body surface area/mass ratio (r = 0.46; P < 0.01) and the difference between M _NET and potential heat loss (r = 0.56; P < 0.01). In conclusion, a large body size (mass and body surface area) is beneficial to reduce ΔT _body during cycling exercise in the heat. However, subjects with higher absolute heat production (more aerobically fit) accumulate more heat because heat production may exceed potential heat loss (uncompensability).     

Dynamics of ovarian follicular fluid in cattle

In the present study, ovarian follicular fluid metabolites, ions, enzymes and hormonal profiles in relation to follicular size in Holstein cattles were investigated. Fluid from small (4–5 mm), medium (6–9 mm) and large (10–20 mm) follicles were collected from 80 clinically healthy and non-pregnant adult cattles. Follicular fluid samples were analyzed for iron, calcium, phosphorous, sodium, potassium, magnesium, glucose, urea, creatinine, cholesterol, triglyceride, protein, albumin, globulin, alkaline phosphatase (ALK), lactate dehydrogenase (LDH), aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), progesterone, testosterone, estradiol-17β, T3 and T4. The concentration of urea, creatinine and protein in small, medium and large follicles did not differ (P > 0.05). The concentrations of phosphorus, magnesium, cholesterol, triglyceride and albumin in follicular fluid decreased (P < 0.05) with the development of the follicle while the reverse was true for calcium, sodium, globulin and estradiol-17β concentrations (P < 0.05). Glucose concentration in small follicles was lower (P < 0.05) than that in medium and large follicles. The concentrations of iron, ALK, LDH, ALAT and ASAT were higher (P < 0.05) than in small follicles. The concentrations of potassium, progesterone and T3 in large follicles were lower (P < 0.05) than those in small and medium follicles while the reverse was true for the T4 concentration (P < 0.05).     

Thermoregulatory effects of three different types of head cooling in humans during a mild hyperthermia

Seven healthy young men participated in six trials with three different types of local cooling [cool air breathing (CAB), face skin cooling (FaC), and combined cooling (CoC)] in a warm environment for 90 min while either resting (operative temperature: T ₀ = 40°C, dew point temperature: T _dp = 15°C, air velocity: v _a = 0.3 m·s⁻¹) or exercising on a cycle ergometer with an external work load of 90 W (T ₀ = 36°C, T _dp = 15°C, v _a = 0.3 m·s⁻¹). Cool air (10°C) arrived at the entry point of the hood and/or the mask at a ventilation rate of 12 m · s⁻¹. Oesophageal temperature was not affected by any kind of cooling, while tympanic temperature was decreased at rest by both FaC and CoC [respectively −0.15 (0.06) and −0.09 (0.03)°C, P ≤ 0.05]. Mean skin temperature was decreased by FaC and CoC at rest [respectively −0.31 (0.07) and −0.27 (0.09)°C, P ≤ 0.05] and during exercise [respectively −0.64 (0.15) and −1.04 (0.22)°C, P ≤ 0.01]. CAB had no effect on skin temperatures. CoC and FaC reduced head skin temperature during both rest and work (P < 0.001) with no effect on the skin temperature of the rest of the body, except under CoC with exercise (P < 0.05). CAB did not influence local sweating. FaC, however, decreased the more profuse sweat rates (P ≤ 0.05) at rest, while CoC decreased all sweating rates at rest (P ≤ 0.05) and only the back, head and leg sweating rates during exercise (P ≤ 0.05). These results suggest that head skin cooling causes a reduction in heat strain, while CAB does not. This beneficial influence does not, however, appear to be the result of selective brain cooling. Tympanic temperature seems to be a good index of the core thermal inputs to the hypothalamic regulatory system, since variations in that parameter were associated with similarly directed variations in the sweating outputs. Accepted: 12 April 1999     

Subacute Inflammatory Activation in Subjects with Acute Coronary Syndrome and Left Ventricular Dysfunction

Several lines of evidence indicate that increased inflammatory cytokine levels can be used for risk prediction in patients with acute coronary syndrome (ACS). This study therefore aimed to evaluate correlations between levels of soluble interleukin (IL)-2 receptor (sIL-2r), IL-6, and IL-8 and in-hospital incidence of acute heart failure (AHF) and left ventricular (LV) systolic dysfunction in the subacute phase of ACS. In 48 consecutive patients with ACS, circulating levels of sIL-2r, IL-6, and IL-8 were ascertained 72–96 h after onset of symptoms. Clinical data, LV function, and in-hospital incidence of AHF were also evaluated. IL-8 levels were significantly higher in patients with pulmonary edema (1,829 ± 2,496 vs 456 ± 624 pg/ml, p < 0.05); sIL-2r, IL-6, and IL-8 levels were increased proportionally to Killip class (r = 0.35, p < 0.05; r = 0.48, r = 0.47, p < 0.01) and in patients with LV ejection fraction (LVEF) < 30%. Levels of sIL-2r were inversely related to LVEF in subjects with acute myocardial infarction (r = −0.51, p < 0.05). Soluble IL-2r and IL-8 levels were related to mitral regurgitation severity (r = 0.34, p < 0.05; r = 0.37, p < 0.05). Levels of sIL-2 were proportional to LV end-diastolic diameter (r = 0.49, p < 0.001) and LV end-systolic diameter (r = 0.58, p < 0.001). Number of cytokines with circulating values above upper level of normal was significantly correlated with Killip class and LVEF (r = 0.40, r = −0.38, p < 0.05). sIL-2r, IL-6, and IL-8 are increased in patients with ACS and systolic dysfunction or AHF. These data suggest that inflammatory cytokine activity detectable in peripheral blood may be useful in identifying subjects with a worse clinical course.     

Relationship between the level of plasma insulin and lipid profile in Iranian fat-tailed sheep

Insulin is an important hormone in regulating lipid metabolism in a variety of animal tissues; it can both decrease lipolysis and cause an increase in triglyceride synthesis of adipose tissue in ruminants. In this study, variations in the plasma concentration of insulin and its correlation with the plasma cholesterol, triglyceride, high-density lipoprotein (HDL cholesterol), low-density lipoprotein (LDL cholesterol), and very-low-density lipoprotein (VLDL) concentrations were investigated. Blood samples were collected from the jugular vein of 96 clinically healthy, non-pregnant ewes (grouped according to their age 1–3, 3–6, 6–12, 12–24, 24–48, and >48 months) in the autumn months. The level of plasma insulin was determined by chemiluminescence and other parameters were measured by spectrophotometry using commercial kits. According to our data from Iranian fat-tailed sheep, increasing age results in significant decrease in the plasma concentration of insulin (p < 0.05, r = −0.278), cholesterol (p < 0.05, r = −0.249), and HDL (p < 0.01, r = −0.299), there was also a significant correlation between plasma insulin and LDL concentration (p < 0.05, r = 0.268). In addition, we found significant differences between age groups for cholesterol and HDL concentrations (p < 0.05).     

High mobility group box protein-1 correlates with microinflammatory state and nutritional status in continuous ambulatory peritoneal dialysis patients

High mobility group box protein-1 (HMGB-1) was recently identified as a new type of inflammatory cytokine. Inflammation can lead to malnutrition to some extent. Our study was aimed to clarify the relationship between serum HMGB-1 level with microinflammatory state and nutritional status in continuous ambulatory peritoneal dialysis (CAPD) patients. Patients in the treatment of maintenance of peritoneal dialysis for >6 months were included. HMGB-1, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay (ELISA). High-sensitivity C-reactive-protein (hs-CRP), prealbumin (PA), serum albumin (S-Alb), hemoglobin (Hb), subjective global nutritional assessment (SGA), and CAPD presents’ urea clearance rate (Kt/V), creatinine clearance (CrCl), residual glomerular filtration rate (rGFR), and dialysate-to-plasma ratio of creatinine after 4 h (D/P_4Cr) were analyzed. The Independent-samples t test and Pearson’s rank correlation test were used. Serum HMGB-1, IL-6, and TNF-α of CAPD patients were significantly higher than in the control group (P < 0.05); Serum HMGB-1 levels had positive relationships with TNF-α (r = 0.730, P < 0.01), hs-CRP (r = 0.361, P < 0.01), and IL-6 (r = 0.865, P < 0.01), and had negative relationships with Hb (r = −0.59, P < 0.01), Alb (r = −0.34, P < 0.05), and PA (r = −0.44, P < 0.01); no significant relationships were found between serum HMGB-1 with SGA, peritoneal dialysis age, Kt/V, CrCl, rGFR, and D/P_4Cr. Our study revealed that HMGB-1 was elevated significantly in CAPD patients and correlated with indicators of inflammation and malnutrition. Serum HMGB-1 could be used as a marker for evaluating inflammation and malnutrition in CAPD patients.     

The effects of drafting on stroking variations during swimming in elite male triathletes

The aim of this study was to determine the effects of drafting behind another swimmer on the metabolic response and stroke characteristics. Six highly trained male triathletes performed two maximal 400-m swims, one in a drafting (D) and one in a non-drafting condition (ND). Their metabolic response was assessed by measuring the oxygen uptake (V˙O₂) and the blood lactate concentration at the end of each 400 m. Swimming velocity, stroke frequency, stroke length, and stroke index (velocity multiplied by stroke length) were recorded every 50 m. In the D and ND conditions, there was no difference in V˙O₂ [66.7 (1.7) ml · kg⁻¹ · min⁻¹ vs 65.6 (1.2) ml · kg⁻¹ · min⁻¹, respectively], however, the lactate concentrations were lower in D than in ND [9.6 (0.9) mM vs 10.8 (0.9) mM, respectively, P < 0.01]. In D, the performance [1.39 (0.02) m · s⁻¹ vs 1.34 (0.02) m · s⁻¹, respectively, P < 0.01] and the stroking parameters (i.e., stroke length and stroke index) increased significantly, while the stroke frequency remain unchanged. In D, a stable pace was maintained, while in ND, velocity decreased significantly throughout the 400 m. In D, the performance gains were related to the 400-m D velocity (r=0.78, P < 0.05), and to the body fat mass (BFM, r=0.99, P < 0.01). The stroke index in D was also related to BFM (r=0.78, P < 0.05). Faster and leaner swimmers achieved greater performance gains and stroke index when drafting. Thus, drafting during swimming increases the performance and contributes to the maintenance of stable stroking parameters such as stroke frequency and stroke length during a 400-m swim. Accepted: 10 April 2000     

Neuromuscular adaptation during prolonged strength training, detraining and re-strength-training in middle-aged and elderly people

Effects of a 24-week strength training performed twice weekly (24 ST) (combined with explosive exercises) followed by either a 3-week detraining (3 DT) and a 21-week re-strength-training (21 RST) (experiment A) or by a 24-week detraining (24 DT) (experiment B) on neural activation of the agonist and antagonist leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris, maximal isometric and one repetition maximum (1-RM) strength and jumping (J) and walking (W) performances were examined. A group of middle-aged (M, 37–44 years, n=12) and elderly (E, 62–77, n=10) and another group of M (35–45, n=7) and E (63–78, n=7) served as subjects. In experiment A, the 1-RM increased substantially during 24 ST in M (27%, P < 0.001) and E (29%, P < 0.001) and in experiment B in M (29%, P < 0.001) and E (23%, P < 0.01). During 21 RST the 1-RM was increased by 5% at week 48 (P < 0.01) in M and 3% at week 41 in E (n.s., but P < 0.05 at week 34). In experiment A the integrated electromyogram (IEMG) of the vastus muscles in the 1-RM increased during 24 ST in both M (P < 0.05) and E (P < 0.001) and during 21 RST in M for the right (P < 0.05) and in E for both legs (P < 0.05). The biceps femoris co-activation during the 1-RM leg extension decreased during the first 8-week training in M (from 29 ± 5% to 25 ± 3%, n.s.) and especially in E (from 41 ± 11% to 32 ± 9%, P < 0.05). The CSA increased by 7% in M (P < 0.05) and by 7% in E (P < 0.001), and by 7% (n.s.) in M and by 3% in E (n.s.) during 24 ST periods. Increases of 18% (P < 0.001) and 12% (P < 0.05) in M and 22% (P < 0.001) and 26% (P < 0.05) in E occurred in J. W speed increased (P < 0.05) in both age groups. The only decrease during 3 DT was in maximal isometric force in M by 6% (P < 0.05) and by 4% (n.s.) in E. During 24 DT the CSA decreased in both age groups (P < 0.01), the 1-RM decreased by 6% (P < 0.05) in M and by 4% (P < 0.05) in E and isometric force by 12% (P < 0.001) in M and by 9% (P < 0.05) in E, respectively, while J and W remained unaltered. The strength gains were accompanied by increased maximal voluntary neural activation of the agonists in both age groups with reduced antagonist co-activation in the elderly during the initial training phases. Neural adaptation seemed to play a greater role than muscle hypertrophy. Short-term detraining led to only minor changes, while prolonged detraining resulted in muscle atrophy and decreased voluntary strength, but explosive jumping and walking actions in both age groups appeared to remain elevated for quite a long time by compensatory types of physical activities when performed on a regular basis. Accepted: 2 May 2000     

Biarticular and monoarticular muscle activation and injury in human quadriceps muscle

We hypothesized that activation of the quadriceps femoris muscle group during eccentric exercise is related to the increase in magnitude of several markers of muscle injury that developed during the next week. Fourteen male subjects performed six to eight sets of five to ten repetitions of single-leg eccentric-only seated knee extension exercise. Magnetic resonance (MR) images were collected before and immediately after exercise and on days 2–4 and 6 after eccentric exercise. Changes in maximal voluntary contraction (MVC), perceived soreness, muscle volume and muscle transverse relaxation of water protons (T₂) were determined for the quadriceps femoris muscle group each day. Changes in muscle volume and T₂ were determined every day for each muscle [vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), rectus femoris (RF)] of the quadriceps femoris group. Post-exercise T₂ was greater than pre-exercise T₂ (P<0.05) for all muscles. The acute ΔT₂ (Post-Pre) was similar (P>0.05) among VL, VM, VI, and RF [5.5 (0.3) ms], suggesting that the four muscles were equally activated during eccentric exercise. In the week after eccentric exercise, subjects experienced delayed-onset muscle soreness (DOMS) and all muscles demonstrated a delayed increase in T₂ above pre-exercise values (P<0.05), suggesting that muscle injury had occurred. For the quadriceps femoris muscle group, there was no correlation between acute ΔT₂ and delayed (peak T₂ during days 2, 3, 4, 6 minus pre-exercise T₂) ΔT₂ (r=0.04, P>0.05). Similar results were obtained when VL, VM, VI and RF were examined separately. Of the four muscles in quadriceps femoris, the biarticular RF experienced greater muscle injury [delayed ΔT₂=15.2 (2.0) ms] compared to the three monoarticular vasti muscles [delayed ΔT₂=7.7 (1.3) ms; P<0.05]. We propose that the disproportionate muscle injury to RF resulted from an ineffective transfer of torque from the knee to hip joint during seated eccentric knee extension exercise, thus causing RF to dissipate greater energy than normal. We conclude that in humans, muscle activation is not a unique determinant of muscle injury. Electronic Publication     

Relationship between muscle T2 * relaxation properties and metabolic state: a combined localized 31P-spectroscopy and 1H-imaging study

A multi-volume ³¹P-magnetic resonance spectroscopy localization procedure was implemented to compare directly muscle metabolism and proton T₂ ^* relaxation properties in the human plantar flexor muscles during exercise. Localized ³¹P-spectra were collected simultaneously from the medial gastrocnemius, lateral gastrocnemius and soleus muscles during exercise using β ₁-insensitive Hadamard Spectroscopic Imaging (HSI). ¹H T₂ ^*-weighted gradient-echo images were acquired at rest and immediately following high-intensity plantar flexion exercise. T₂ ^* mapping of the individual calf muscles showed that plantar flexion with the knee extended produces significant increases (P < 0.0001) in the mean (SEM) T₂ ^* of the medial [35.6 (1.2) ms vs 28.5 (0.5) ms at rest] and lateral gastrocnemius [35.6 (0.9) ms vs 26.2 (0.9) ms at rest], but not in the soleus [26.7 (0.6) ms vs 27.3 (0.8) ms at rest]. In accordance with the changes in T₂ ^*, the ratio of inorganic phosphate to phosphocreatine (P_i:PCr) and the intracellular muscle pH shifted significantly in the gastrocnemii, while the soleus showed no change in muscle pH and only a moderate increase in P_i-to-Ph. Comparison of spectroscopic and relaxation parameters in both gastrocnemius muscles revealed a significant relationship between post-exercise T₂ ^* and intracellular pH (r=0.72–0.76) and P_i-to-Ph ratios (r=0.81–0.88) during exercise. Using an improved method of localization, this study confirms the existence of a strong relationship between transverse relaxation properties and the metabolic state in skeletal muscles engaged in heavy exercise. Accepted: 28 December 1999     

Influence of ultra-long-term fatigue on the oxygen cost of two types of locomotion

The aim of this study was to examine the effects of fatigue induced by a 65-km ultramarathon on the oxygen cost of running (C_r) and cycling (C_cycl). The day before and immediately after the race, a group of nine well-trained male subjects performed two sub-maximal 4-min exercise bouts: one cycling at a power corresponding to 1.5 W · kg⁻¹ body mass on an electromagnetically braked ergometer, and one running at 11 km · h⁻¹ on a flat asphalt roadway. Before oxygen cost determinations, the subjects performed 12 “ankle” jumps at a given frequency that was fixed by an electronic metronome (2.5 Hz). From the non-fatigued to the fatigued condition, there was a significant increase in minute ventilation for both running (P < 0.01) and cycling (P < 0.0001). Significant changes were also found in respiratory exchange ratio both for running (P=0.01) and cycling (P < 0.0001). However, running and cycling differed in that C_cycl increased significantly by [mean (SD)] 24.2 (11.5)% (P < 0.001), suggesting an alteration of muscle efficiency, while C_r did not change with fatigue [186.8 (14.1) mlO₂ · kg⁻¹ · km⁻¹ vs 186.8 (18.7) mlO₂ · kg⁻¹ · km⁻¹]. In addition, contact times during hopping increased significantly from 0.173 (0.019) ms to 0.194 (0.027) ms (P < 0.01). Analysis of the factors that determine C_r indicate that the subjects modified their movement pattern in order to decrease the mechanical cost of running in such long-term fatigue conditions. Accepted: 7 August 2000