Plasma Creatine Kinase Activity Research Articles

Effect of 5-day vitamin E supplementation on muscle injury after downhill running in rats

Antioxidant supplementation has been suggested to prevent exercise-induced muscle injury, but the findings are inconsistent. The objective of this study was to investigate the potential protective role of vitamin E treatment against eccentric exercise-induced muscle injury by examining morphological and functional alterations in rat soleus muscle after downhill running as well as muscle injury markers in the blood. Sixty adult male Wistar rats were randomly assigned to vitamin E-treated or placebo-treated groups studied at rest, immediately post-exercise or 48h post-exercise (n=10 per group). Vitamin E was administered by daily intraperitoneal injections of 100mg/kg body mass of DL: -α-tocopheryl acetate for five consecutive days prior to exercise, resulting in the doubling of its plasma concentration. Downhill running resulted in significant (P<0.05) changes in all injury markers for the placebo-treated rats at 0 and 48h post-exercise. However, significantly smaller soleus muscle single-twitch tension (P (t)) and unfused (40Hz) tetanic force, and greater plasma creatine kinase (CK) and lactate dehydrogenase (LD) activities compared with the control were found only immediately post-exercise for the vitamin E-treated rats (P<0.05). Maximal tetanic force (P (o)) did not decline significantly compared to sedentary controls at neither time points measured. The vitamin E-treated rats had significantly (P<0.05) higher soleus muscle P (t) immediately post-exercise than the placebo-treated rats as well as lower plasma CK and LD activity 48h post-exercise. However, there was no difference in P (o) decline between groups at either time points measured. Vitamin E-treated rats had less pronounced morphological alterations in muscle in the immediate and 48-h post-exercise period. In conclusion, the effect of short-term vitamin E supplementation against eccentric exercise-induced muscle injury did not appear to be physiologically significant, because vitamin E failed to prevent the decline in the functional measure of P (o) compared to the placebo conditions.

Effects of Flexibility Training on Eccentric Exercise-Induced Muscle Damage

This study investigated whether flexibility training would attenuate muscle damage induced by maximal eccentric exercise. Thirty untrained young men were allocated to static stretching (SS), proprioceptive neuromuscular facilitation (PNF), or control group (n = 10 per group). The SS consisted of 30 sets of a 30-s standard SS with a 30-s rest between sets, and the PNF included 5 sets of the 30-s standard SS followed by 3 sets of three "contract-relax-agonist-contract" procedures. These were performed three times a week for 8 wk, and all subjects performed six sets of 10 maximal isokinetic (30°·s) lengthening contractions of the knee flexors after the 8-wk training or 8 wk after the baseline measures (control). Changes in indirect markers of muscle damage before and for 5 d after the eccentric exercise were compared among the groups. The range of motion (ROM) of the hip joint increased by 25°, and the optimum angle of the knee flexors shifted (P < 0.05) to a longer muscle length by 10° after training, without significant differences between SS and PNF. No significant changes in these variables were evident for the control group. Compared with the control group, the SS and PNF groups showed significantly (P < 0.05) smaller decreases and faster recovery of knee flexor muscle strength and smaller changes in optimum angle, ROM, muscle soreness, and plasma creatine kinase activity and myoglobin concentration without significant differences between the groups. The preeccentric exercise ROM or optimum angle was significantly (P < 0.05) correlated with the changes in the muscle damage markers. These results suggest that both SS and PNF training are effective in attenuating eccentric exercise-induced muscle damage and that flexible muscles are less susceptible to the damage.

The repeated-bout effect: influence on biceps brachii oxygenation and myoelectrical activity

This study investigated biceps brachii oxygenation and myoelectrical activity during and following maximal eccentric exercise to better understand the repeated-bout effect. Ten men performed two bouts of eccentric exercise (ECC1, ECC2), consisting of 10 sets of 6 maximal lengthening contractions of the elbow flexors separated by 4 wk. Tissue oxygenation index minimum amplitude (TOI(min)), mean and maximum total hemoglobin volume by near-infrared spectroscopy, torque, and surface electromyography root mean square (EMG(RMS)) during exercise were compared between ECC1 and ECC2. Changes in maximal voluntary isometric contraction (MVC) torque, range of motion, plasma creatine kinase activity, muscle soreness, TOI(min), and EMG(RMS) during sustained (10-s) and 30-repeated isometric contraction tasks at 30% (same absolute force) and 100% MVC (same relative force) for 4 days postexercise were compared between ECC1 and ECC2. No significant differences between ECC1 and ECC2 were evident for changes in torque, TOI(min), mean total hemoglobin volume, maximum total hemoglobin volume, and EMG(RMS) during exercise. Smaller (P < 0.05) changes and faster recovery of muscle damage markers were evident following ECC2 than ECC1. During 30% MVC tasks, TOI(min) did not change, but EMG(RMS) increased 1-4 days following ECC1 and ECC2. During 100% MVC tasks, EMG(RMS) did not change, but torque and TOI(min) decreased 1-4 days following ECC1 and ECC2. TOI(min) during 100% MVC tasks and EMG(RMS) during 30% MVC tasks recovered faster (P < 0.05) following ECC2 than ECC1. We conclude that the repeated-bout effect cannot be explained by altered muscle activation or metabolic/hemodynamic changes, and the faster recovery in muscle oxygenation and activation was mainly due to faster recovery of force.

Monitoring markers of muscle damage during a 3 week periodized drop-jump exercise programme

The aim of this study was to examine changes in indirect markers of muscle damage during 3 weeks of stretch–shortening exercise with a progressively increasing load and continued modulation of various key training variables. Eight healthy untrained men performed a drop-jump programme involving a progressive increase in load impact with respect to the number of jumps performed, drop (platform) height, squat depth amplitude, and addition of weights. Maximal concentric and isometric knee extensor strength were assessed immediately before and 10 min after each training session. Voluntary and 100 Hz-stimulation-evoked torque decreased acutely after each training session relative to pre-exercise values (P < 0.05) but recovered before the subsequent training session. Post-exercise plasma creatine kinase activity increased from 162.2 ± 56.2 IU · l−1 to 284.3 ± 116.3 IU · l−1 at 48 h after the first training session (P < 0.05) and remained marginally elevated throughout the training period. The present results indicate that detrimental muscle damage can be avoided with drop-jump training even with the gradual introduction of more demanding exercise induced by increasing the volume, intensity, and muscle stretch amplitude. These findings suggest that the human neuromuscular system is highly adaptable to progressively varied loading demands during stretch–shortening exercise training.

Effects of cold water immersion on the recovery of physical performance and muscle damage following a one-off soccer match

The aim of this study was to assess the effects of a single session of cold or thermoneutral water immersion after a one-off match on muscular dysfunction and damage in soccer players. Twenty-male soccer players completed one match and were randomly divided into cryotherapy (10 min cold water immersion, 10°C, n = 10) and thermoneutral (10 min thermoneutral water immersion, 35°C, n = 10) groups. Muscle damage (creatine kinase, myoglobin), inflammation (C-reactive protein), neuromuscular function (jump and sprint abilities and maximal isometric quadriceps strength), and delayed-onset muscle soreness were evaluated before, within 30 min of the end, and 24 and 48 h after the match. After the match, the players in both groups showed increased plasma creatine kinase activity (30 min, 24 h, 48 h), myoglobin (30 min) and C-reactive protein (30 min, 24 h) concentrations. Peak jump ability and maximal strength were decreased and delayed-onset muscle soreness increased in both groups. However, differential alterations were observed between thermoneutral water and cold water immersion groups in creatine kinase (30 min, 24 h, 48 h), myoglobin (30 min), C-reactive protein (30 min, 24 h, 48 h), quadriceps strength (24 h), and quadriceps (24 h), calf (24 h) and adductor (30 min) delayed-onset muscle soreness. The results suggest that cold water immersion immediately after a one-off soccer match reduces muscle damage and discomfort, possibly contributing to a faster recovery of neuromuscular function.

Effects ofPanax ginsengSupplementation on Muscle Damage and Inflammation after Uphill Treadmill Running in Humans

The purpose of this investigation was to determine whether Panax ginseng extract intake would influence exercise-induced muscle damage and inflammation responses. Eighteen male college students were randomly assigned to either an RG intake group (RG, n = 9) or a placebo group (P, n = 9). All subjects performed a high-intensity uphill treadmill running task (two rounds of 45 min at 10 km/h speed with a 15 degree uphill slope separated by 5 min of rest). The RG group ingested 20 g/day of Korean red ginseng extract (mixed with 200 ml of water) three times/day for seven days prior to performing the uphill treadmill exercise test and for four days after the treadmill test, while the P group ingested 200 ml of water containing Agastachis Herba on the same schedule. Plasma creatine kinase activity (CK) and interlukin-6 (IL-6) levels were measured at pre-exercise and 24, 48, 72, and 96 h post-exercise; the IL-6 level was also measured at 1 and 2 h post-exercise. To evaluate insulin sensitivity, the oral glucose tolerance test (OGTT) was performed 24 h post-exercise. Plasma CK level in RG was significantly lower than that in P 72 h post-exercise (p < 0.05), and IL-6 level was significantly decreased in RG during the 2 h and 3 h recovery period compared to that of P (p < 0.05). Plasma glucose and insulin responses in RG were significantly reduced compared to those of P (p < 0.05). The results of this study suggest that RG supplementation could reduce exercise-induced muscle damage and inflammatory responses, resulting in improvements in insulin sensitivity.

Cerivastatin induces type-I fiber-, not type-II fiber-, predominant muscular toxicity in the young male F344 rats

3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are associated with adverse skeletal muscle toxicity, but the underlying mechanism remains unclear. To investigate the pathological mechanism of statin-induced myotoxicity, cerivastatin (20 ppm; corresponding to 2 mg/kg/day) was dietarily administered to young male F344 rats for 10 days, and time-course clinical observations, measurement of plasma creatine kinase activity, and light and electron microscopy of type I fiber-predominant skeletal muscle (soleus) or type II fiber-predominant skeletal muscles (extensor digitorum longus and tibialis anterior), were performed. Clinical symptoms including weakness of hind limbs, staggering gait and body weight loss, accompanied by marked plasma creatinine kinase elevation in rats fed cerivastatin at around Day 6 to 8. Interestingly, microscopic examination revealed that cerivastatin-induced muscle damages characterized by hypercontraction (opaque) and necrosis of the fibers were of particular abundance in the soleus muscle at Day 8, whereas these histological lesions in the extensor digitorum longus and tibialis anterior were negligible, even at Day 9. Prior to manifestation of muscle damage, swollen mitochondria and autophagic vacuoles in the soleus were observed as the earliest ultra structural changes at Day 6; then activated lysosomes, disarray of myofibril and dilated sarcoplasmic reticulum vesicles became ubiquitous at Day 8. These results demonstrate that cerivastatin induces type I fiber-predominant muscles injury, which is associated with mitochondrial damage, in young male F344 rats. Since the rat exhibiting type I fiber-targeted injury is a unique animal model for statin-induced myotoxicity, it will be useful for gaining insight into mechanisms of statin-induced myotoxicity.

Effects of sevoflurane postconditioning on myocardial ischemia-reperfusion injury in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass

Objective To investigate the effects of sevoflurane postconditioning on myocardial ischemiareperfusion(I/R)injury in patients undergoing coronary artery bypass grafting(CABG)with cardiopulmonary bypass(CPB).Methods Forty NYHA Ⅰ -Ⅲ patients of both sexes,aged 55-64 yr,with BMI ＜ 30 kg/m2,scheduled for CABG under CPB,were randomly divided into 2 groups(n = 20): control group(group C)and sevoflurane postconditioning group(group S).Anesthesia was induced with midazolam and/or etomidate,fentanyl and rocuronium.Patients were tracheal intubated and mechanically ventilated.Anesthesia was maintained with iv infusion of propefol and intermittent iv injection of fentanyl and pipecuronium.In group S,2% sevoflurane was inhaled continuously for 15 min immediately after aortic unclamping.After anesthesia induction,before CPB,10 min after the end of CPB,at the end of operation,and 6 and 24 h after operation,MAP,HR,CVP,mean pulmonary arterial pressure,pulmonary arterial wedge pressure,CO and S(v)O2 were recorded,and CI,SVI,systemic vascular resistance index and pulmonary vascular resistance index were calculated.Blood samples were taken from central vein before aortic clamping,at 6 h of reperfusion and 24 h after operation for determination of plasma creatine kinase(CK),creatine kinase isoenzyme(CK- M B)and lactate dehydrogenase(LDH)activities and tropenin I(TnI)concentrations.Myocardial tissues were obtained from right auricle before aortic clamping and at the end of CPB for observation of the ultrastructure and the severity of myocardial injury was assessed.Results There was no significant difference in hemodynamics and parameters of cardiac function between the two groups(P ＞ 0.05).Compared with group C,plasma CK-MB and LDH activities at 6 h of reperfusion and plasma CK activity and TnI concentrations at 24 h after operation were significantly decreased and the myocardial injury was significantly reduced after the end of CPB in group S(P ＜ 0.05).Conclusion Sevoflurane postconditioning can protect myocardium against I/R injury induced by CPB in patients undergoing CABG. Key words: Anesthetics,inhalation; Myocardial reperfusion injury; Cardiopulmonary bypass

Cambios sanguineos y sudorales en equinos sometidos a carreras de resistencia

Endurance races produce thermic, neuroendocrine and oxidative stress, large consumption of energetic substrates, loss of electrolytes and water through ventilation and sweat. In these races free radical production changes several physiological processes. In this work the alteration in the plasma and sweat composition, as well as the endocrine and antioxidative responses of horses competing in endurance rides were characterized. For this purpose, heparinized blood was collected before and at 22 Km and the end of 42 Km endurance race, from ten horses (6 arabian and 4 angle­chileans). In addition, sweat was collected at 22 and 42 Km by means of a specially designed sponge placed underneath the saddle. Both at 22 Km and at the end of the race there was a significant increase in packed cell volume (PCV), plasma lactate, plasma osmolality, total plasma proteins (TPP) and plasma concentrations of aldosterone and cortisol. At the end of the race, there were increased plasma potassium concentration, plasma antioxidant capacity and creatine kinase (CK) activity, chloride and calcium concentrations decreased. In all runners, both sweat samples turned out to be hyperosmotic with respect to plasma, being chloride and potassium sweat concentrations twice and ten fold as much as those in plasma, respectively. These results characterize the equipe management of energetic supplies during endurance races and demonstrate the efficiency of homeostatic mechanisms to maintain plasma electrolytes composition, overcoming their losses through sweat and to neutralize oxidative stress and decreases in blood volume.

Cambios sanguíneos y sudorales en equinos sometidos a carreras de resistencia

Endurance races produce thermic, neuroendocrine and oxidative stress, large consumption of ener­getic substrates, loss of electrolytes and water through ventilation and sweat. In these races free radi­cal production changes several physiological processes.In this work the alteration in the plasma and sweat composition, as well as the endocrine and an­tioxidative responses of horses competing in endurance rides were characterized.For this purpose, heparinized blood was collected before and at 22 km and the end of 42 km endu­rance race, from ten horses (6 arabian and 4 Anglo-Chileans). In addition, sweat was collected at 22 and 42 km by means of a specially designed sponge placed underneath the saddle.Both at 22 km and at the end of the race there was a significant increase in packed cell volume (PCV), plasma lactate, plasma osmolality, total plasma proteins (TPP) and plasma concentrations of aldosterone and cortisol. At the end of the race, whilst there were increased plasma potassium concen­tration, plasma antioxidant capacity and creatine kinase (CK) activity, chloride and calcium concen­trations decreased.In all runners, both sweat samples turned out to be hyperosmotic with respect to plasma, being chlo­ride and potassium sweat concentrations twice and ten fold as much as those in plasma, respectively.These results characterize the equine management of energetic supplies during endurance races anddemonstrate the efficiency of homeostatic mechanisms to maintain plasma electrolytes composition, over­coming their losses through sweat and to neutralize oxidative stress and decreases in blood volume.

The effect of sea transport from Ireland to the Lebanon on inflammatory, adrenocortical, metabolic and behavioural responses of bulls

The objective was to investigate the effect of sea transport on the physiological, behavioural and performance responses of bulls. One-hundred and eleven bulls (mean body weight (standard error of the mean) 429 (5.7 kg)) were randomly assigned to one of three treatments; control (C; n = 54) bulls were housed in 6 pens at Teagasc, Grange Research Centre at a stocking density of (1), 1.7 m 2/head (C1.7; 3 pens) and (2), 3.4 m 2/head (C3.4; 3 pens) and (3), transported (T) bulls ( n = 57) were penned at a space allowance of 1.7 m 2/head (6 pens) and allocated to one of five decks on the shipping vessel. C and T bulls were subjected to the same live weight (d −2), blood sampling and rectal temperature (d −1) measurements pre-transport and on d 3, d 6, d 9 and d 11 of the study. T bulls had greater ( P < 0.05) live weight gain (+4.4%) compared with C1.7 bulls (−2.0%) and C3.4 (+0.13%)). Time spent lying was greater ( P < 0.05) among C1.7 and C3.4 bulls (9.9% and 53.3%, respectively) compared with T bulls (45.8%). Rectal body temperature was not different ( P > 0.05) among treatment groups throughout the study. At d 11, neutrophil % was greater ( P < 0.05) in transported bulls on decks 1, 2, 4 and 5 compared with C1.7 and C3.4 treatments. Plasma cortisol concentrations were not different ( P > 0.05) between control and transported bulls. Plasma creatine kinase (CK) activity was lower ( P < 0.05) among C3.4 and T bulls on decks 2, 3, 4 and 5 compared with d 3 values. In conclusion, the welfare of bulls transported by sea on the sea journey was not adversely affected. Housing control bulls at a reduced space allowance (1.7 m 2) had a negative effect on live weight gain.

Comparison in eccentric exercise-induced muscle damage among four limb muscles

This study tested the hypothesis that changes in indirect markers of muscle damage following maximal eccentric exercise would be smaller for the knee extensors (KE) and flexors (KF) compared with the elbow flexors (EF) and extensors (EE). A total of 17 sedentary men performed five sets of six maximal isokinetic (90° s(-1)) eccentric contractions of EF (range of motion, ROM: 90°-0°, 0 = full extension), EE (55°-145°), KF (90°-0°), and KE (30°-120°) using a different limb with a 4-5-week interval in a counterbalanced order. Changes in maximal isometric and concentric isokinetic strength, optimum angle, limb circumference, ROM, plasma creatine kinase activity and myoglobin concentration, muscle soreness, and echo-intensity of B-mode ultrasound images before and for 5 days following exercise were compared amongst the four exercises using two-way repeated-measures ANOVA. All variables changed significantly following EF, EE, and KF exercises, but KE exercise did not change the optimum angle, limb circumference, and echo-intensity. Compared with KF and KE, EF and EE showed significantly greater changes in all variables, without significant differences between EF and EE. Changes in all variables were significantly greater for KF than KE. For the same subjects, the magnitude of change in the dependent variables following exercise varied among the exercises. These results suggest that the two arm muscles are equally more susceptible to muscle damage than leg muscles, but KF is more susceptible to muscle damage than KE. The difference in the susceptibility to muscle damage seems to be associated with the use of muscles in daily activities.

Microdystrophin Delivery in Dystrophin-Deficient ( mdx) Mice by Genetically-Corrected Syngeneic MSCs Transplantation

Cell transplantation and gene therapy are two promising therapeutical approaches for the treatment on Duchenne Muscular Dystrophy (DMD). However, both strategies have met many hurdles, mainly because of the absence of an efficient systemic delivery system on gene therapy and immune reactionns on cell transplantation. In this project, we investigated the strategy based on combination of these two basic ones, ie, transplantation of transgene-corrected mdx mesenchymal stem cells (MSCs) into mdx mice to cure DMD. The MSCs isolated from male mdx mice were transduced with recombinant adenovirus including human microdystrophin gene and labeled with BrdU were transplanted into female mdx mice, the Chimerism with the sex-determinant Y chromosome and human microdystrophin expression were detected. Simultaneously, the plasma creatine kinase (CK) activity, the improvement with the muscles' pathology and contractile propertie were evaluated. The results clearly demonstrated that some human dystrophin and BrdU expression collectively were detected in some muscles of transplanted mdx mice. Moreover, the CK activity and percentage of centrally nucleated fiber (CNF) decreased slightly after transplanation. Regrettably, the protective effect on contraction-induced injury in TA and diaphragm muscles wasn't significantly improvement after transplantation. Our results suggested, if enhancement on the efficiency with cell transplantation, that the transplantation of autologous MSCs corrected by dystrophin may be a form to treat DMD patients in future.

Effect of N-acetylcysteine on markers of skeletal muscle injury after fatiguing contractile activity

The effects of N-Acetylcysteine (NAC), an unspecific antioxidant, on fatiguing contractile activity-induced injury were investigated. Twenty-four male Wistar rats were randomly assigned to two groups. The placebo group (N=12) received one injection of phosphate buffer (PBS) 1 h prior to contractile activity induced by electrical stimulation. The NAC group (NAC; N=12) received electrical stimulation for the same time period and NAC (500 mg/kg, i.p.) dissolved in PBS 1 h prior to electrical stimulation. The contralateral hindlimb was used as a control, except in the analysis of plasma enzyme activities, when a control group (rats placebo group not electrically stimulated and not treated) was included. The following parameters were measured: tetanic force, muscle fatigue, plasma activities of creatine kinase (CK) and lactate dehydrogenase (LDH), changes in muscle vascular permeability using Evans blue dye (EBD), muscle content of reactive oxygen species (ROS) and thiobarbituric acid-reactive substances (TBARS) and myeloperoxidase (MPO) activity. Muscle fatigue was delayed and tetanic force was preserved in NAC-treated rats. NAC treatment decreased plasma CK and LDH activities. The content of muscle-derived ROS, TBARS, EBD and MPO activity in both gastrocnemius and soleus muscles were also decreased by NAC pre-treatment. Thus, NAC has a protective effect against injury induced by fatiguing contractile activity in skeletal muscle.

Comparison between alternating and pulsed current electrical muscle stimulation for muscle and systemic acute responses

This study compared alternating current and pulsed current electrical muscle stimulation (EMS) for torque output, skin temperature (Tsk), blood lactate and hormonal responses, and skeletal muscle damage markers. Twelve healthy men (23-48 yr) received alternating current EMS (2.5 kHz delivered at 75 Hz, 400 micros) for the knee extensors of one leg and pulsed current (75 Hz, 400 micros) for the other leg to induce 40 isometric contractions (on-off ratio 5-15 s) at the knee joint angle of 100 degrees (0 degrees: full extension). The use of the legs for each condition was counterbalanced among subjects, and the two EMS bouts were separated by 2 wk. The current amplitude was consistently increased to maximally tolerable level, and the torque and perceived intensity were recorded over 40 isometric contractions. Tsk of the stimulated and contralateral knee extensors were measured before, during, and for 30 min after EMS. Blood lactate, growth hormone, testosterone, insulin-like growth factor 1, testosterone, and cortisol were measured before, during, and for 45 min following EMS. Muscle damage markers included maximal voluntary isometric contraction torque, muscle soreness with a 100-mm visual analog scale, and plasma creatine kinase (CK) activity, which were measured before and 1, 24, 48, 72, and 96 h after EMS. No significant differences in the torque induced during stimulation (approximately 30% maximal voluntary isometric contraction) and perceived intensity were found, and changes in Tsk, blood lactate, and hormones were not significantly different between conditions. However, all of the measures showed significant (P<0.05) changes from baseline values. Skeletal muscle damage was evidenced by prolonged strength loss, development of muscle soreness, and increases in plasma CK activity; however, the changes in the variables were not significantly different between conditions. It is concluded that acute effects of alternating and pulsed current EMS on the stimulated muscles are similar.

Comparison between maximal lengthening and shortening contractions for biceps brachii muscle oxygenation and hemodynamics

Eccentric contractions (ECC) require lower systemic oxygen (O2) and induce greater symptoms of muscle damage than concentric contractions (CON); however, it is not known if local muscle oxygenation is lower in ECC than CON during and following exercise. This study compared between ECC and CON for changes in biceps brachii muscle oxygenation [tissue oxygenation index (TOI)] and hemodynamics [total hemoglobin volume (tHb)=oxygenated-Hb+deoxygenated-Hb], determined by near-infrared spectroscopy over 10 sets of 6 maximal contractions of the elbow flexors of 10 healthy subjects. This study also compared between ECC and CON for changes in TOI and tHb during a 10-s sustained and 30-repeated maximal isometric contraction (MVC) task measured immediately before and after and 1-3 days following exercise. The torque integral during ECC was greater (P<0.05) than that during CON by approximately 30%, and the decrease in TOI was smaller (P<0.05) by approximately 50% during ECC than CON. Increases in tHb during the relaxation phases were smaller (P<0.05) by approximately 100% for ECC than CON; however, the decreases in tHb during the contraction phases were not significantly different between sessions. These results suggest that ECC utilizes a lower muscle O2 relative to O2 supply compared with CON. Following exercise, greater (P<0.05) decreases in MVC strength and increases in plasma creatine kinase activity and muscle soreness were evident 1-3 days after ECC than CON. Torque integral, TOI, and tHb during the sustained and repeated MVC tasks decreased (P<0.01) only after ECC, suggesting that muscle O2 demand relative to O2 supply during the isometric tasks was decreased after ECC. This could mainly be due to a lower maximal muscle mass activated as a consequence of muscle damage; however, an increase in O2 supply due to microcirculation dysfunction and/or inflammatory vasodilatory responses after ECC is recognized.

Protective effects of therapeutic cold and heat against the oxidative damage induced by a muscle strain injury in rats

The mechanisms of action of physical agents commonly used to treat skeletal muscle lesions are not well understood. In this study, we examined whether the modulation of oxidative stress is involved in the beneficial effects of cold and heat on gastrocnemius muscle strain injury. Adult male Wistar rats were submitted to a strain injury and treated with therapeutic agents in an isolated or combined form. Strain damage caused an increase in muscle and blood oxidative damage. We suggest that this oxidative damage might be related to the impairment of the muscle cell structure, since we observed a significant positive correlation between increased plasma creatine kinase activity and both oxidized dichlorofluoresceine and lipid peroxidation levels in muscle and blood. The intensity of the inflammatory response appears also to be an important factor in the genesis of oxidative damage immediately following a muscle strain injury. Therapeutic cold seems to be more effective in preventing the damage induced by a strain injury, possibly due to its capacity to control the impairment of muscle cell structure and to modulate the intensity of the inflammatory response that follows a muscle strain injury.

Nutritional Status Affects Fluvastatin-Induced Hepatotoxicity and Myopathy in Rats

Rats that consumed a high-fat and high-sucrose diet (HF diet) developed hepatic steatosis. Treatment of HF diet-fed rats with fluvastatin (8 mg/kg) was lethal, followed by an elevation in levels of plasma aspartate aminotransferase and creatine kinase activities and skeletal muscle toxicity. This study was conducted to determine whether nutritional status affects statin-induced adverse effects in rats. Fluvastatin treatment of rats fed the HF diet led to an increase in systemic exposure, suggesting altered metabolism and elimination. In fact, although hepatic multidrug resistance-associated protein (Mrp) 2 and multidrug resistance (Mdr) 1b protein levels were not significantly changed by fluvastatin treatment for 8 days of rats fed a HF diet, the organic anion-transporting protein (Oatp) 1, Mrp3, CYP1A, CYP2C, UDP-glucuronosyltransferase (UGT) 1A1, and UGT1A5 protein levels were moderately decreased and the Oatp2, CYP3A, and UGT2B1 protein levels were markedly suppressed. No significant difference in the baseline level of Oatp1, Oatp2, Mrp2, Mrp3, Mdr1b, CYP1A, CYP2C, CYP3A, UGT1A1, UGT1A5, or UGT2B1 protein was found between the standard diet- and HF diet-fed groups. In addition, the mRNA levels of Oatp2, CYP2C11, and CYP3A1/2 were markedly decreased in HF diet-fed and fluvastatin-treated rats. There was no significant difference in the glucuronidation activities against fluvastatin among the four groups. In liver cell nuclei, levels of constitutive androstane receptor, pregnane X receptor, and hepatocyte nuclear factor 4α proteins were decreased in fluvastatin-treated HF diet-fed rats, which correlated with the decrease in Oatp2, CYP2C, and CYP3A. Taken together, these results indicate that nutritional status may influence adverse effects of fluvastatin by increasing systemic exposure through modulation of hepatic uptake and elimination.

Effect of eccentric contraction velocity on muscle damage in repeated bouts of elbow flexor exercise

Eccentric exercise induces muscle damage, but controversy exists concerning the effect of contraction velocity on the magnitude of muscle damage, and little is known about the effect of contraction velocity on the repeated-bout effect. This study examined slow (60 degrees.s(-1)) and fast (180 degrees.s(-1)) velocity eccentric exercises for changes in indirect markers of muscle damage following 3 exercise bouts that were performed every 2 weeks. Fifteen young men were divided into 2 groups based on the velocity of eccentric exercise: 7 in the Ecc60 (60 degrees.s(-1)) group, and 8 in the Ecc180 (180 degrees.s(-1)) group. The exercise consisted of 30 maximal eccentric contractions of the elbow flexors at each velocity, in which the elbow joint was forcibly extended from 60 degrees to 180 degrees (full extension) on an isokinetic dynamometer. Changes in maximal voluntary isometric contraction strength, range of motion, muscle soreness, and plasma creatine kinase activity before and for 4 days after the exercise were compared in the 2 groups using a mixed-model analysis (groupxboutxtime). No significant differences between groups were evident for changes in any variables following exercise bouts; however, the changes were significantly smaller (p<0.05) after the second and third bouts than after the first bout. These results indicate that the contraction velocity does not influence muscle damage or the repeated-bout effect.

Potent Protective Effect Conferred by Four Bouts of Low-Intensity Eccentric Exercise

It is known that submaximal eccentric exercise does not confer as strong a protective effect as maximal eccentric exercise. This study tested the hypothesis that four bouts of submaximal eccentric exercise would confer a similar protective effect to one bout maximal eccentric exercise. Thirty untrained men were placed into 4 x 40% (40%) or control (CON) groups (n = 15 per group) by matching preexercise maximal voluntary isometric contraction strength (MVC). The 40% group performed 30 eccentric contractions with a load of 40% MVC (40% ECC) every 2 wk for four times followed 2 wk later by 30 maximal eccentric exercise (100% ECC) of the elbow flexors of the nondominant arm. The CON group performed two bouts of the 100% ECC separated by 2 wk. MVC at six angles, optimum angle (OA), concentric isokinetic strength (30 degrees x s(-1) and 300 degrees x s(-1)), range of motion, upper arm circumference, plasma creatine kinase activity and myoglobin concentration, muscle soreness, and echo intensity of B-mode ultrasound images were taken before to 5 d after each exercise. No significant differences in the changes in any measures were evident between the 100% ECC of the 40% group and the second 100% ECC of the CON group. Changes in all measures except for OA and upper arm circumference after the second to the fourth 40% ECC bouts were significantly smaller than those after the first 40% ECC bout. The changes in the measures after any of the 40% ECC bouts were significantly (P < 0.05) smaller than those after the first 100% ECC bout of the CON group. These results suggest that repeating submaximal eccentric exercise confers the same magnitude of protective effect as one bout of maximal eccentric exercise against the subsequent maximal eccentric exercise.