The effects of chronic concentric and eccentric training on position sense and joint reaction angle of the knee extensors.

The aim of the present study was to compare the effect of chronic concentric or eccentric training on position sense and joint reaction angle, in healthy, untrained young men. Twenty-four men were randomly assigned into a pure concentric (CT) or a pure eccentric (ET) group and performed for 8 weeks, one training session/week, 75 maximal knee extensors contractions. Before and 48 h after the first (W1) and the last (W8) training sessions, knee joint position sense and joint reaction angle were assessed at three different knee angles (i.e. 30°, 45° and 60°). At the same time points, indirect indices of exercise-induced muscle damage (EIMD) were evaluated (i.e. range of motion [ROM], optimal angle, maximum isometric, concentric and eccentric torques, delayed onset muscle soreness [DOMS] and blood creatine kinase concentrations [CK]). Forty-eight hours post W1, position sense, reaction angle and all EIMD indices were significantly changed for both groups (p < 0.05; η2: 0.125-0.618), however, greater alterations were observed after ET. Significant correlations were found, in both groups, between the training-induced changes of position sense, reaction angles and the changes of EIMD biomarkers (r: -0.855-0.825; p < 0.005). No significant changes were found 48 h post W8 for position sense, reaction angle and EIMD indices (p > 0.285) for both CT or ET groups. In conclusion, exercise-induced changes in position sense and reaction angle, were related to the magnitude of EIMD, and not by the type of muscle contraction per se.HighlightsExercise induced changes in position sense and reaction angle, were related to the magnitude of EIMD, and not by the type of muscle contraction per se.After the 1st training session eccentric exercise caused greater disturbances, compared to concentric exercise, in EIMD indices which caused concomitant disturbances to position sense and knee reaction angle.8 weeks of either eccentric or concentric training leads to preservation of position sense and knee reaction angle 48 h after maximal intensity exercise of either types of muscle contraction.

Redox basis of exercise physiology.

Redox reactions control fundamental processes of human biology. Therefore, it is safe to assume that the responses and adaptations to exercise are, at least in part, mediated by redox reactions. In this review, we are trying to show that redox reactions are the basis of exercise physiology by outlining the redox signaling pathways that regulate four characteristic acute exercise-induced responses (muscle contractile function, glucose uptake, blood flow and bioenergetics) and four chronic exercise-induced adaptations (mitochondrial biogenesis, muscle hypertrophy, angiogenesis and redox homeostasis). Based on our analysis, we argue that redox regulation should be acknowledged as central to exercise physiology.

Rapid decreases of key antioxidant molecules in critically ill patients: A personalized approach.

BACKGROUND & AIMS: Oxidative stress is regarded a key component of critical illness and has been associated with poor prognosis in Intensive Care Unit (ICU) patients. Diverse antioxidant treatments have been applied to combat oxidative stress in ICU, yet the results were typically disappointing. An explanation for this failure is that all studies utilized antioxidants indiscriminately and did not take into account the antioxidant profile of the patients. The aim of the present study was to investigate whether critically ill patients experience different insufficiencies in three major antioxidants with a "recycling" redox relationship (vitamin C, vitamin E and glutathione) and in the central reductant molecule of many enzymatic antioxidants (NADPH). METHODS: Sixty mechanically-ventilated adult medical critically ill patients (age: 63.5 ± 17.1; APACHE II score: 21.2 ± 7.4; Glasgow Coma Scale: 6.2 ± 1.9) were enrolled in the study, while 20 healthy age-matched volunteers served as control group. The antioxidant profile and the level of systemic oxidative stress (F2-isoprostanes) were measured at ICU admission and at days 1 and 7. RESULTS: The majority of the ICU patients developed rapid and severe antioxidant insufficiencies (by exhibiting less than 50% of the control values) in one (22/60), two (7/60) or three (2/60) of the antioxidants measured, despite the almost similar levels of oxidative stress. CONCLUSIONS: The wide heterogeneity in antioxidant decreases in response to ICU stay highlights the importance of patient stratification when planning to apply antioxidant treatments and indicates that the successful delivery of personalized clinical nutrition may depend on our ability to identify "responsive" phenotypes.

Nicotinamide riboside supplementation dysregulates redox and energy metabolism in rats: Implications for exercise performance.

NEW FINDINGS: What is the central question of this study? The aim was to investigate the potential metabolic and redox mechanisms that impaired exercise performance after 21 days of supplementation with 300 mg (kg body weight)-1 of nicotinamide riboside in rats. What is the main finding and its importance? Nicotinamide riboside disturbed energy and redox metabolism and impaired exercise performance in heathy rats. Exogenously administered redox agents in heathy populations might lead to adverse effects. ABSTRACT: Nicotinamide riboside is a recently discovered form of vitamin B3 that can increase NAD(P) levels. NAD(P) plays key roles in energy metabolism, and its main function is the transfer of electrons in various cellular reactions. Research in aged or diseased mice reported that nicotinamide riboside increases NAD(H) levels, reduces morbidity and improves health and muscle function. We have recently shown that in healthy young rats, chronic administration of nicotinamide riboside marginally non-significantly decreased exercise performance by 35% (P = 0.071). As a follow-up to this finding, we analysed samples from these animals, in an attempt to reveal the potential mechanisms driving this adverse effect, focusing on redox homeostasis and bioenergetics. Thirty-eight Wistar rats were divided into four groups: control (n = 10), exercise (n = 9), nicotinamide riboside (n = 10) and exercise plus nicotinamide riboside (n = 9). Nicotinamide riboside was administered for 21 days [300 mg (kg body weight)-1 daily]. At the end of administration, the exercise and the exercise plus nicotinamide riboside groups performed an incremental swimming performance test until exhaustion. Nicotinamide riboside supplementation increased the levels of NADPH in the liver (P = 0.050), increased the levels of F2 -isoprostanes in plasma (P = 0.047), decreased the activity of glutathione peroxidase (P = 0.017), glutathione reductase (P < 0.001) and catalase (P = 0.024) in erythrocytes, increased the level of glycogen in the liver (P < 0.001) and decreased the concentration of glucose (P = 0.016) and maximal lactate accumulation in plasma (P = 0.084). These findings support the prevailing idea that exogenously administered redox agents in heathy populations might lead to adverse effects and not necessarily to beneficial or neutral effects.

Adaptations to endurance training depend on exercise-induced oxidative stress: exploiting redox interindividual variability.

AIM: The aim of this study was to reveal the role of reactive oxygen and nitrogen species (RONS) in exercise adaptations under physiological in vivo conditions and without the interference from other exogenous redox agents (e.g. a pro-oxidant or antioxidant). METHODS: We invented a novel methodological set-up that exploited the large redox interindividual variability in exercise responses. More specifically, we used exercise-induced oxidative stress as the 'classifier' measure (i.e. low, moderate and high) and investigated the physiological and redox adaptations after a 6-week endurance training protocol. RESULTS: We demonstrated that the group with the low exercise-induced oxidative stress exhibited the lowest improvements in a battery of classic adaptations to endurance training (VO2 max, time trial and Wingate test) as well as in a set of redox biomarkers (oxidative stress biomarkers and antioxidants), compared to the high and moderate oxidative stress groups. CONCLUSION: The findings of this study substantiate, for the first time in a human in vivo physiological context, and in the absence of any exogenous redox manipulation, the vital role of RONS produced during exercise in adaptations. The stratification approach, based on a redox phenotype, implemented in this study could be a useful experimental strategy to reveal the role of RONS and antioxidants in other biological manifestations as well.

Going retro: Oxidative stress biomarkers in modern redox biology.

The field of redox biology is inherently intertwined with oxidative stress biomarkers. Oxidative stress biomarkers have been utilized for many different objectives. Our analysis indicates that oxidative stress biomarkers have several salient applications: (1) diagnosing oxidative stress, (2) pinpointing likely redox components in a physiological or pathological process and (3) estimating the severity, progression and/or regression of a disease. On the contrary, oxidative stress biomarkers do not report on redox signaling. Alternative approaches to gain more mechanistic insights are: (1) measuring molecules that are integrated in pathways linking redox biochemistry with physiology, (2) using the exomarker approach and (3) exploiting -omics techniques. More sophisticated approaches and large trials are needed to establish oxidative stress biomarkers in the clinical setting.

Oxygen Delivery and Muscle Deoxygenation during Continuous, Long- and Short-Interval Exercise.

This study compared the O2 delivery (a central determinant of VO2) and muscle deoxygenation (reflecting a peripheral determinant of VO2) during intense continuous, long-interval, and short-interval exercise protocols. Twelve young men completed the 3 protocols with equal overall effort. Simultaneous and continuous recordings of central hemodynamics, muscle oxygenation/deoxygenation and VO2 were performed. Peak responses for stroke volume and peripheral resistance did not differ among protocols, whereas peak cardiac output and VO2 were higher in long-interval vs. continuous and short-interval protocols with inactive rest phases (p<0.05). The average responses for all central parameters were higher in continuous and long-interval vs. short-interval exercise (p<0.05); average VO2 and exercise-time above 80% VO2max were also higher in continuous and long-interval vs. short-interval protocol (p<0.05). Muscle de-oxygenation (↑Δdeoxyhemoglobin,↓Δoxyhemoglobin, ↓muscle O2-saturation), as well as the mismatch of O2 delivery and utilization (Δdeoxyhemoglobin/VO2) were remarkably alike among protocols. In conclusion, all 3 protocols resulted in a great activation of central and peripheral determinants of VO2. When performed with equal overall effort, the intense continuous and interval modalities reveal similarities in muscle O2-utilization response, but differences in central hemodynamic and VO2 responses. Intense continuous and long-interval protocols exert a more commanding role on the cardiovascular system and VO2 response compared to short-interval exercise with inactive rest phases.

Reductive stress after exercise: The issue of redox individuality.

Exercise has been consistently used as an oxidant stimulus in redox biology studies. However, previous studies have focused on group differences and did not examine individual differences. As a result, it remains untested whether all individuals experience oxidative stress after acute exercise. Therefore, the main aim of the present study was to investigate whether some individuals exhibit unexpected responses after an acute eccentric (i.e., muscle-damaging) exercise session. Ninety eight (N = 98) young men performed an isokinetic eccentric exercise bout with the knee extensors. Plasma, erythrocytes and urine samples were collected immediately before and 2 days post-exercise. Three commonly used redox biomarkers (F2-isoprostanes, protein carbonyls and glutathione) were assayed. As expected, the two oxidant biomarkers (F2-isoprostanes and protein carbonyls) significantly increased 2 days after exercise (46% and 61%, respectively); whereas a significant decrease in glutathione levels (by -21%) was observed after exercise. A considerable number of the participants exhibited changes in the levels of biomarkers in the opposite, unexpected direction than the group average. More specifically, 13% of the participants exhibited a decrease in F2-isoprostanes and protein carbonyls and 10% of the participants exhibited an increase in glutathione levels. Furthermore, more than 1 out of 3 individuals exhibited either unexpected or negligible (from 0% to ± 5%) responses to exercise in at least one redox biomarker. It was also observed that the initial values of redox biomarkers are important predictors of the responses to exercise. In conclusion, although exercise induces oxidative stress in the majority of individuals, it can induce reductive stress or negligible stress in a considerable number of people. The data presented herein emphasize that the mean response to a redox stimulus can be very misleading. We believe that the wide variability (including the cases of reductive stress) described is not limited to the oxidant stimulus used and the biomarkers selected.

A single bout of downhill running transiently increases HOMA-IR without altering adipokine response in healthy adult women.

PURPOSE: Eccentric exercise-induced muscle damage may cause marked alterations in insulin sensitivity. However, it is not entirely known whether such alterations are also related to changes in adipokine levels. The aim of this study was to investigate the effects of muscle damage due to downhill running on inflammation, insulin sensitivity and selected adipokines related to insulin regulation (adiponectin, visfatin, resistin). METHODS: Data were collected from 12 healthy adult women. Each subject participated in two trials, 4 weeks apart. The first trial was reserved for resting measurements only (control trial), while the second trial involved a 45-min exercise (-15 % slope, ~60 % of VO2max) intervention (exercise trial). Insulin sensitivity (HOMA), creatine kinase activity (CK), delayed onset muscle soreness (DOMS), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), glucose, insulin, adiponectin, resistin, and visfatin were assessed pre-exercise and 1, 2, 3, and 4 days post-exercise and during the same time points in the control trial. RESULTS: Analyses revealed that CK, DOMS, TNF-α, IL-6, insulin and HOMA significantly increased (p < 0.05) throughout recovery (days 1-4). Adiponectin and visfatin remained unchanged, while resistin significantly increased (p < 0.05) only 2 days post-exercise. Visfatin was negatively correlated with HOMA at days 1 and 4 of recovery. CONCLUSION: Although muscle damage due to downhill running caused a decline of insulin sensitivity, this response was not associated with the changes in adipokine levels.

No adverse effects of statins on muscle function and health-related parameters in the elderly: an exercise study.

The aim of the present study was to investigate the effects of a repeated bout of eccentric exercise on health-related parameters and muscle performance on subjects undergoing atorvastatin therapy. Twenty-eight elderly men participated in the investigation and were assigned either in a control (n = 14) or in a statin therapy group (n = 14). All participants performed two isokinetic eccentric exercise bouts separated by 3 weeks. Muscle damage indices, resting energy expenditure, substrate metabolism, lipid and lipoprotein profile, as well as insulin sensitivity, were evaluated before and after eccentric. No differences in muscle function were observed between the two groups either at rest or after exercise. Eccentric exercise increased resting energy expenditure, increased fat oxidation, improved lipid profile, and increased insulin resistance 2 days after both eccentric exercise bouts. However, these changes appeared to lesser extent after the second bout. No differences were observed in the responses in the health-related parameters in the control and in the statin therapy group. Eccentric exercise affected similarly the control and the atorvastatin-treated individuals. The present results indicate that atorvastatin-treated elderly individuals may participate in various physical activities, even high-intensity muscle-damaging activities, without negative impact on muscle function and adaptation.

Muscle perfusion of posterior trunk and lower-limb muscles at rest and during upper-limb exercise in spinal cord-injured and able-bodied individuals.

STUDY DESIGN: Nonrandomized-controlled trial. OBJECTIVES: To assess muscle perfusion at rest and during arm-cranking exercise (ACE) in upper and lower posterior trunk and vastus lateralis (VL) muscles in individuals with spinal cord injury (SCI) and controls (C). SETTING: Exercise Physiology-Biochemistry Laboratory. METHODS: Eight SCI with thoracic lesion and eight C received injections of radioactive tracer to trapezius (TRAP), latissimus dorsi (LAT) and VL. Radioactive counts were recorded with a γ-camera for 10 min at rest and during ACE (60% VO(2max) for 20 min). Time-count curves were generated and the isotope clearance rate, expressed as half-life time (T(1/2),min), was calculated to assess muscle perfusion. RESULTS: Resting T(1/2) was lower in TRAP and LAT vs VL (P<0.05) in SCI, however, there were no differences among muscles in C. Arm-cranking increased (P<0.001) the isotope clearance in TRAP and LAT in SCI and C, whereas no effect was found on T(1/2) in VL in both groups. T(1/2) was longer (P<0.05) in SCI vs C in VL at rest and during ACE, whereas there were no differences between groups in posterior trunk muscles. CONCLUSIONS: Resting muscle perfusion was reduced in the paralyzed limbs of SCI compared with C, whereas there was no evidence of impaired microcirculation in upper and lower back muscles in SCI. Although ACE did not induce a hyperemic response in VL, it increased hyperemia in upper and lower posterior trunk muscles in SCI, suggesting beneficial effects of this type of activity on muscle microvasculature in this region.

Beneficial changes in energy expenditure and lipid profile after eccentric exercise in overweight and lean women.

The aim was to compare lean and overweight females in regard to the effects of eccentric exercise on muscle damage indices, resting energy expenditure (REE) and respiratory quotient (RQ) as well as blood lipid and lipoprotein profile. Lean and overweight females (deviated by their body mass index) performed an eccentric exercise session. Muscle damage, energy cost and lipid profile were assessed pre-exercise and up to 72 h post-exercise. After eccentric exercise (i) muscle damage indices were affected more in the overweight subjects compared with the lean subjects; (ii) the elevation of absolute and relative REE was larger and more prolonged in the overweight group compared with the lean group; (iii) after 24 h, RQ had significantly declined, with the overweight subjects exhibiting a larger reduction compared with the lean group; and (iv) the blood lipid profile was favorably modified, with the overweight group exhibiting more favorable responses compared with the lean group. The differences between the lean and the overweight subjects may be partly due to the fact that overweight individuals experienced greater muscle damage than lean individuals. Eccentric exercise may be a promising lifestyle factor to combat obesity and dyslipidemias.

Position sense and reaction angle after eccentric exercise: the repeated bout effect.

The purpose of the present investigation was to examine the effects of a repeated eccentric exercise on position sense and muscle reaction angle. Fourteen healthy women underwent an isokinetic exercise session on their knee flexors, which was repeated after 4 weeks. Muscle damage indices, position sense and joint reaction angle of the knee were examined before, immediately after, as well as at 1, 2, 3, 4 and 7 days after exercise. The second exercise bout induced significantly lesser effects in all muscle damage indices as well as lesser disturbances in position sense and reaction angle when compared to the first one. The main finding of this study is that position sense and joint reaction angle to release of the lower limbs may adapt in response to a repeated bout of eccentric exercise, leading to less disturbances in position sense and reaction angle after the second bout of exercise.

Short duration exhaustive aerobic exercise induces oxidative stress: a novel play-oriented volitional fatigue test.

AIM: Exercise is associated with the generation of reactive oxygen and nitrogen species. This study examined the oxidative stress in response to a novel volitional fatigue test. METHODS: Eleven male college students performed a volitional fatigue test consisting of shuttle runs with a tennis racquet in the hand towards the left and right sidelines within the tennis singles court in an attempt to hit tennis balls until exhaustion. A tennis ball serving machine was adjusted to alternate feeds to the forehand and backhand sides of the subjects, standing at the baseline, at a frequency of 20 balls per minute. RESULTS: Mean time to volitional fatigue was 5.9+/-1.3 min and mean heart rate at volitional fatigue was 189+/-8.1 beats x min(-1). The volitional fatigue test resulted in significant increases in blood thiobarbituric acid-reactive substances (22%), protein carbonyls (58%), catalase activity (143%), total antioxidant capacity (34%) and oxidized glutathione (GSSG, 81%) concentration, as well as significant decreases in reduced glutathione (GSH, 15%) concentration and GSH/GSSG ratio (56%) immediately postexercise, as compared to the pre-exercise concentration. CONCLUSION: The data provide evidence that acute short duration exhaustive aerobic exercise in the form of a novel volitional fatigue test is capable of inducing oxidative stress. This novel test could serve as an alternative exercise modality to study oxidative stress.

The effect of eccentric exercise on position sense and joint reaction angle of the lower limbs.

Impaired position sense and impaired joint reaction angle of the lower limbs after muscle-damaging activities is a serious functional limitation that may lead to an increased risk of injury, particularly in older populations. The purpose of the present study was to examine whether position sense and joint reaction angle to release can be affected by eccentric exercise-induced muscle damage. Twelve women underwent an isokinetic exercise session of the lower limb. Isometric peak torque, delayed-onset muscle soreness, serum creatine kinase, position sense, and knee joint reaction angle to release were examined before, immediately after, and 24, 48, and 72 h post-exercise. Due to the effect of eccentric exercise, subjects persistently placed their lower limb at a more extended position, representing a shorter knee extensor muscle. Eccentric exercise increased the knee reaction angle of the lower limb after release from 0 degrees and 15 degrees but not from 30 degrees and 45 degrees . Position sense and joint reaction to release were similarly affected by eccentric exercise and independently of visual feedback. Position sense was impaired only immediately post-exercise (probably due to muscle fatigue), whereas impairment of the reaction angle to release persisted up to 3 days post-exercise (probably due to muscle damage). Attenuation of position sense and joint reaction angle of the lower limbs after damaging activities is a serious functional limitation that may lead to an increase risk of injury, particularly in older populations.

Mitochondrial phospholipids of rat skeletal muscle are less polyunsaturated than whole tissue phospholipids: implications for protection against oxidative stress.

The fatty acid composition of phospholipids is an important determinant of membrane function. Although the mitochondria play a pivotal role in skeletal muscle function, the fatty acid composition of their individual phospholipids has not been examined. The purpose of this study was to determine the fatty acid profile of each phospholipid in rat skeletal muscle mitochondria and compare it with that of the whole muscle. Lipids were extracted from the gastrocnemius muscles of 10 Wistar rats, and phospholipids were separated by thin-layer chromatography. The fatty acid composition of each phospholipid was then determined by gas chromatography. The same procedure was applied to a mitochondrial preparation from these muscles. We found that the fatty acid composition of the individual mitochondrial phospholipids (phosphatidyl choline, phosphatidyl ethanolamine, cardiolipin, phosphatidyl inositol, phosphatidyl serine, sphingomyelin, and lysophosphatidyl choline) and of the total mitochondrial phospholipids differed markedly (P < 0.05) from the fatty acid composition of the corresponding whole muscle phospholipids. Notably, the mitochondrial phospholipids had higher percentages of MUFA [13.9 (2.1) vs. 10.3 (0.9)] and lower percentages of PUFA [34.8 (4.3) vs. 39.5 (5.2)] and n6 fatty acids [25.0 (2.5) vs. 27.6 (2.5)]. Overall, the mitochondrial phospholipids had a lower unsaturation index than whole muscle phospholipids [135 (20) vs. 161 (26)]. Because PUFA are susceptible to peroxidation, unlike saturated fatty acids and MUFA, we propose that the low polyunsaturation of mitochondrial phospholipids is the result of selective pressure toward membranes that are more resistant to oxidative damage by reactive oxygen species produced in their vicinity. The negative effect of the low polyunsaturation on membrane fluidity may be counterbalanced by the higher percentage of MUFA and the known low cholesterol content of mitochondrial membranes.

Comparison of the blood redox status between long-distance and short-distance runners.

Exercise increases the production of reactive oxygen species, which may damage a number of cell constituents. Organisms have developed a sophisticated antioxidant system for protection against reactive oxygen species. Our aim was to compare the adaptive responses of antioxidant mechanisms and the blood redox status of two groups of athletes, long-distance and short-distance runners. Thiobarbituric acid reactive substances, catalase activity and total antioxidant capacity was measured in the serum, while reduced and oxidized glutathione as well as their ratio were determined in blood hemolysates. Serum catalase activity (P<0.001) was found to be three times higher in long-distance compared to short-distance runners (25.4 vs. 8.9 micromol x min(-3) x ml(-1)), whereas the two groups did not differ in the other markers. Catalase activity also correlated significantly with maximal oxygen consumption in long-distance runners. In conclusion, we report here that long-distance and short-distance runners exhibit similar blood redox status judged by several oxidative stress indices, except for the much higher activity of catalase in long-distance runners. This different effect of the two training modules on catalase activity of long-distance runners might be partly due to the high oxygen load imposed during their repeated prolonged exercise bouts.

Comparison of the phospholipid and triacylglycerol fatty acid profile of rat serum, skeletal muscle and heart.

Although several studies have analyzed the fatty acid profile of phospholipids (PL) and, to a lesser degree, triacylglycerols (TG) in one or more tissues concurrently, a systematic comparison of the fatty acid composition of different tissues and/or lipid classes is lacking. The purpose of the present study was to compare the fatty acid composition of major lipid classes (PL and TG) in the rat serum, soleus muscle, extensor digitorum longus muscle and the heart. Lipids were extracted from these tissues and analyzed by a combination of thin-layer chromatography and gas chromatography. We found many significant differences in various tissues and lipid classes. Serum had the most distinct fatty acid profile in PL but this "uniqueness" was less apparent in TG, where differences among tissues were in general less frequent than in PL. These two skeletal muscles exhibited similar fatty acid composition in both lipid classes despite their different muscle fiber type composition, denoting that fiber type is not a major determinant of the fatty acid composition of rat skeletal muscle. The fatty acid profile of heart PL was the most different from that of the other tissues examined. PL were rich in polyunsaturated fatty acids, whereas TG were rich in monounsaturated fatty acids. Although the reasons for the differences in fatty acid profile among the tissues examined are largely unknown, it is likely that these differences have an impact upon numerous biological functions.

Effect of voluntary exercise on the expression of IGF-I and androgen receptor in three rat skeletal muscles and on serum IGF-I and testosterone levels.

The effects of anabolic agents and training on skeletal muscle are believed to be mediated by a variety of growth and transcription factors. Among these regulatory proteins, insulin-like growth factor-I (IGF-I) and androgen receptor (AR) play a crucial role. The purpose of this study was to investigate the effects of wheel running on IGF-I and AR mRNA expression in three distinct rat skeletal muscles (i.e., gastrocnemius, vastus lateralis, and soleus), as well as on the serum levels of IGF-I and testosterone. Twenty male Wistar rats were housed in cages with free access to running wheels for 12 weeks, while nine rats served as controls. Analysis of the mRNA expression of IGF-I and AR using real time RT-PCR revealed no significant differences between the trained and untrained rats in any of the muscles studied. Enzyme immunoassay showed significantly lower serum levels of IGF-I and testosterone in the trained compared to the untrained animals. These results suggest that chronic exercise in wheels does not affect IGF-I and AR mRNA levels in rat skeletal muscle, while decreasing the circulating levels of two anabolic factors, i.e., IGF-I and testosterone. It is concluded that IGF-I, AR and testosterone seem to play a marginal role during the adaptation process of rat skeletal muscle to long-term wheel running.

Effect of chronic wheel running on the fatty acid composition of phospholipids and triacylglycerols in rat serum, skeletal muscle and heart.

AIM: The purpose of this study was to examine the effects of long-term wheel running on the fatty acid composition of phospholipids (PL) and triacylglycerols (TG) in rat serum, skeletal muscle (soleus and extensor digitorum longus) and heart. METHODS: To this end, the relevant tissues of 11 trained male Wistar rats were compared with those of 14 untrained ones. RESULTS: There were several significant differences between the two groups regarding the concentrations and percentages of individual fatty acids in serum PL and TG, with most differences appearing in the fatty acid distribution of PL. Monounsaturated fatty acids of muscle PL were significantly lower in the trained rats. Estimated elongase activity was significantly higher, whereas Delta(9)-desaturase activity was significantly lower in the trained muscles. Monounsaturated fatty acids of PL were also significantly lower in the trained hearts. The fatty acid composition of PL in the skeletal muscles and the heart adapted to training in a comparable manner, whereas most of the changes in the fatty acid profile of TG were tissue-dependent. Judging from the magnitude of the effect sizes and the percentage differences between trained and untrained animals, there were many large effects of chronic exercise on the fatty acid composition of the tissues examined. CONCLUSION: Long-term wheel running modified the fatty acid profile of PL and TG in rat serum, skeletal muscle and heart, and could thus be considered as a modulator of tissue fatty acid composition.