Effects Of Swimming Training Research Articles

Effect of swimming training on levels of asprosin, lipid profile, glucose and insulin resistance in rats with metabolic syndrome

BackgroundAsprosin is a novel biomarker that associated with type 2 diabetes mellitus. The aim of this study was to investigate the effects of continuous and interval swimming training on the asprosin, lipid profile, glucose concentration and insulin resistance serum levels of rats with metabolic syndrome. MethodsForty-eight male Wistar rats were randomly divided into two groups, standard diet (SD) and high-fat diet (HD), and received their respective diets for a period of 12 weeks without exercise stimuli. After this period, the animals were randomly divided into four groups (n = 8); normal control standard diet (NC), control (Ctr), continuous training (load 0–3% body mass, 5 d/wk, for 8 weeks, CT) and interval training (load 5–16% body mass, 5 d/wk, for 8 weeks, IT). The continuous and interval training consisted of a swimming exercise performed over eight weeks. ResultThe NC and trained groups showed lower values of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL-C) and glucose concentration compared to Ctr group. Serum level of asprosin significantly decreased underlying CT and IT compared to NC and Ctr groups. No significant difference were observed between trained groups. ConclusionIt seems that both swimming training methodologies are shown to be effective in the serum levels of asprosin, lipid profile and glucose concentration in metabolic syndrome rats.

The Effects of Swimming Training on Arterial Stiffness, Muscular Strength and Cardiorespiratory Endurance in Postmenopausal Women with Stage 2 Hypertension

PURPOSE: Aging is associated with progressive decreases in arterial health and function as well as overall fitness. It is crucial to prevent or reduce the negative effects of aging on vasculature and fitness components by implementing appropriate lifestyle interventions, such as exercise training. We examined the effects of a swimming (SWM) regimen on arterial stiffness (pulse wave velocity, PWV), blood pressure (BP), wave reflection (AIx), muscle strength and aerobic capacity in postmenopausal women with stage 2 hypertension. METHODS: Using a parallel experimental design, participants were randomly assigned to either a SWM (n=52) or non-exercising control group (n=48) for 20 weeks. Participants in the SWM group trained 3-4 days/week, progressing in duration from 25 to 45 min. Participants’ carotid to radial PWV (crPWV), BP, AIx, muscular strength and cardiorespiratory capacity were measured at baseline and after 20 weeks of their assigned intervention. RESULTS: There was a significant group x time interaction (P<0.05) for crPWV, AIx, and systolic and diastolic BP, which significantly decreased (P<0.05); and strength and cardiorespiratory capacity, which significantly increased (P<0.05) following SWM compared to no changes in control. CONCLUSION: SWM led to reductions in arterial stiffness, wave reflection and BP while increasing strength and aerobic capacity in postmenopausal women with stage 2 hypertension. SWM may be an effective intervention in the prevention and treatment of age-related vascular complications as well as declines in muscle strength and cardiorespiratory capacity.

The Effects of Swimming Training in Cold Water on Antioxidant Enzyme Activity and Lipid Peroxidation in Erythrocytes of Male and Female Aged Rats.

The aim of this study was to verify whether eight-week-long swimming exercise training would evaluate the level of selected indicators of the pro-oxidant/antioxidant status in response to cold water in comparison with swimming under thermoneutral conditions in sedentary male and female elderly rats. The exercise-trained groups swam four min/day and five days a week during eight weeks of housing. Exercise was performed by swimming in glass tanks containing tap water maintained according to group at 5 °C and 36 °C. At the end of treatment (48 h after the last session), all rats were anaesthetized. The level of chosen biomarkers of oxidative stress and antioxidant enzyme activity was determined in the red blood cells and plasma. The results of study show that female rats seem to be better adapted to changing thermal conditions of the environment, developing not only morphological, but also antioxidant, defense mechanisms, mainly in the form of increased erythrocyte superoxide dismutase (SOD) activity and glutathione (GSH) concentration to restore the pro-oxidant/oxidant balance of the organism. Significantly higher concentrations of GSH were observed in the female rats of the group swimming in cold water (by 15.4% compared to the control group and by 20.5% in relation to the group of female rats swimming at 36 °C). In the group exposed to swimming training exercise in cold water, a significantly higher activity of SOD1 (by 13.4%) was found compared to the control group. On the other hand, the organs of ageing male rats show a reduced capacity to increase the metabolic response to low temperatures compared to female ones. In addition, it was demonstrated that cold exposure leads to an increase in lipid peroxidation in tissues. On the other hand, the repeated exposure to low levels of oxidative stress may result in some adaptive changes in organisms that help them to resist stress-induced damage.

Swimming exercise in combination with garlic extract administration as a therapy against doxorubicin-induced hepatic, heart and renal toxicity to rats

Effect of swimming training is considered on doxorubicin-induced toxicity in the liver, heart, and kidney of rats. Histopathological degeneration could partially be prevented in swimming-trained rats pretreated with garlic extract. Exercise combined with garlic extract reduced the malondialdehyde value and improved the activities of antioxidant enzymes. Doxorubicin treatment enhanced the mean values of blood ALT, AST, and ALP enzymes, as well as hepatic, cardiac, and renal TNF-α and HSP70 (p < .05). Swimming alone or supplemented with garlic extract can protect liver, heart, and kidney against doxorubicin toxicity by increasing antioxidants and reducing oxidative stress and inflammation.

The effects of swimming training on arterial function, muscular strength, and cardiorespiratory capacity in postmenopausal women with stage 2 hypertension.

Aging is associated with progressive decreases in arterial health as well as muscular strength and cardiorespiratory capacity. It is crucial to prevent or reduce the negative effects of aging on vasculature, muscular, and cardiorespiratory function by implementing appropriate lifestyle interventions, such as exercise training. We examined the effects of a swimming (SWM) regimen on arterial stiffness (pulse wave velocity [PWV]), blood pressure (BP), wave reflection (augmentation index [AIx]), muscle strength, and aerobic capacity in sedentary, postmenopausal women with stage 2 hypertension. One hundred participants (∼74 years of age) were recruited from multiple general practice centers. Using a parallel experimental design, participants were randomly assigned to either SWM (n = 52) or nonexercising control group (n = 48) for 20 weeks. Participants in the SWM group trained 3 to 4 days/week. Participants' carotid to radial PWV, BP, AIx, muscular strength, and cardiorespiratory capacity were measured at baseline and after 20 weeks of their assigned intervention. There was a significant group × time interaction (P < 0.05) for carotid to radial PWV (Δ-1.2 m/s), AIx (Δ-4%), and systolic (Δ-9 mm Hg) and diastolic BP (Δ - 9 mm Hg), which significantly decreased (P < 0.05); and strength (Δ3 kg) and cardiorespiratory capacity (Δ4 mL/kg/min), which significantly increased (P < 0.05) following SWM compared to no changes in control. SWM led to reductions in arterial stiffness, wave reflection, and BP while increasing strength and aerobic capacity in postmenopausal women with stage 2 hypertension. SWM may be an effective intervention in the prevention and treatment of age-related vascular complications and declines in muscle strength and cardiorespiratory capacity.

Effect of swimming training on nerve morphological recovery after compressive injury

ABSTRACTObjective: This study aims to investigate morphological alterations caused by partial sciatic nerve ligation (PNL) and the efficacy of a moderate-intensity swimming training as therapeutic strategy for nerve regeneration.Methods: A number of 30 male adult mice were equally divided in control, 14 days after PNL (PNL 14 days), 42 days after PNL (PNL 42 days), 70 days after PNL (PNL 70 days) and 5-week exercise training after 7 days post-lesion (PNL trained 35 days) groups. PNL trained 35 days group began with a 10-min session for 3 days and this time was gradually increased by 10 min every three sessions until the animals had swum for 50 min per session. Morphoquantitative analysis was carried out to assess nerve regeneration in each group.Results: PNL 14 days group exhibited less degenerating signs than PNL 42 days group, where most post-lesion alterations were visualized. Nerve area and minimum diameter were significantly lower (p < 0.05) than control group. PNL 70 days group showed a greater degree of regenerating fibers and similar morphometric parameters to control group. PNL trained 35 days demonstrated signs of regeneration, reaching control group values in the morphometric analysis.Discussion: PNL promotes great histopathological changes, which became more visible at 42 post-injury days. A natural nerve-regeneration tendency was observed throughout time, as observed in PNL 70 days group; nevertheless, moderate swimming training was found to be a therapeutic resource for nerve regeneration, accelerating such process from a morphoquantitative perspective.Abbreviations: ANOVA: One-way analysis of variance; BDNF: Brain-derived neurotrophic factor; FGF-2: Fibroblast growth factor 2; GDNF: Glial cell line derived neurotrophic factor; IGF: Insulin-link growth factor; IL-1β: Interleukin-1β; NGF: Neural growth factor; PBS: Phosphate-buffered saline; PNL: Partial sciatic nerve ligation

Swim training affects bone canonical Wnt pathway in type 2 diabetes induced by high fat diet and low dose of streptozotocin in male rats

Objective: Susceptibility to diabetes-induced bone complication has been linked to Wnt signaling, which plays an important role in bone development and remodeling. In this study, the effect of swim training on Wnt pathway in T2DM was investigated.Materials and methods: Forty male rats were assigned to groups: control (C), diabetic (D), exercised control (E) and diabetic exercised (DE). One week after the induction of diabetes, animals were subjected to swim. At the end of training, bone gene and protein levels of SOST, RUNX2 and RANKL/OPG ratio were measured.Results: Diabetes could significantly increase bone sclerostin expression levels, while decreased RUNX2 mRNA and protein. Bone RANKL/OPG ratio was significantly lower in diabetic rats compared to control group. Swim training significantly increased this ratio in DE compared to D group.Conclusion: Swim training could partially compensate the diabetes-associated changes of Wnt pathway possibly by moderating sclerostin or blood sugar.

The impact of forced swimming on expression of RANKL and OPG in a type 2 diabetes mellitus rat model

Objective: The importance of swimming in bone metabolism during type 2 diabetes (T2DM) is not well known. Receptor activator of nuclear factor-kB ligand (RANKL)/ osteoprotegerin (OPG) system as a critical pathway in bone remodeling may play a role in pathogenesis of T2DM. Hence, we tested this pathway and the possible beneficial effects of swim training on T2DM.Materials and methods: Forty male rats were assigned to groups (n = 10): control(C), diabetic (D), exercised control (E), and diabetic exercised (DE). One week after the induction of diabetes, animals were subjected to swim. At the end of training, fasting blood sugar, insulin, bone and serum OPG and RANKL levels were measured.Results: Diabetes significantly increased OPG and decreased RANKL mRNAs and proteins in bone and serum and swim training could reverse these changes to control.Conclusion: Swim training could partially compensate T2DM associated changes of bone and serum OPG/RANKL in rats.

Effects of Swimming Training and Estrogen Terapy on C‐Type Natriuretic Peptide‐induced Relaxation in aorta of ovariectomized Hypertensive Rats

Estrogen deficiency is detrimental to vascular function. On the other hand, the practice of exercise training and estrogen therapy improve vascular function. However, the effects of swimming training (SW) and estrogen therapy (ET) on the relaxation induced by C‐type natriuretic peptide (CNP) is unclear. Our aim was to investigate the effects of chronic SW and ET on CNP‐induced vascular relaxation in the aorta of ovariectomized hypertensive rats. The groups were randomly divided into sham (S), sham+SW (SSW), ovariectomized (OVX), ovariectomized+ET (OET), ovariectomized+SW (OSW) and ovariectomized+ET+SW (OET+SW). ET (5 mg of 17β‐Estradiol, s.c.) and SW (60 min – 5x/wk) were performed during eight weeks. Systolic blood pressure was measured before and after the training and treatment period. Aorta reactivity was performed in response to increased concentration of CNP. Ovariectomy significantly impairs the systolic blood pressure, while ET, SW and the association of both prevents this impairment. OVX reduces significantly the CNP‐induced vasorelaxation in the aorta of hypertensive animals. However, ET and SW were able to prevent the reduction caused by OVX, being able to maintain the relaxation at the same level as observed in sham animals. The association of ET and SW can also prevent the decrease in relaxation induced by CNP, but it did not show any additive effects. SW and ET prevent the ovariectomy‐induced worsening in vascular relaxation to CNP in hypertensive animals. Therefore, the practice of chronic exercise training can play a major role in the cardioprotection in hypertensive postmenopausal women.Support or Funding InformationUFES‐CApes‐CNPq‐Fapes

Swimming training prevents coronary endothelial dysfunction in ovariectomized spontaneously hypertensive rats.

Estrogen deficiency and hypertension are considered major risk factors for the development of coronary heart disease. On the other hand, exercise training is considered an effective form to prevent and treat cardiovascular diseases. However, the effects of swimming training (SW) on coronary vascular reactivity in female ovariectomized hypertensive rats are not known. We aimed to evaluate the effects of SW on endothelium-dependent coronary vasodilation in ovariectomized hypertensive rats. Three-month old spontaneously hypertensive rats (SHR, n=50) were divided into four groups: sham (SH), sham plus swimming training (SSW), ovariectomized (OVX), and ovariectomized plus swimming training (OSW). The SW protocol (5 times/week, 60 min/day) was conducted for 8 weeks. The vasodilatory response was measured in isolated hearts in the absence and presence of a nitric oxide synthase inhibitor (L-NAME, 100 µM). Cardiac oxidative stress was evaluated in situ by dihydroethidium fluorescence, while the expression of antioxidant enzymes (SOD-2 and catalase) and their activities were assessed by western blotting and spectrophotometry, respectively. Vasodilation in SHR was significantly reduced by OVX, even in the presence of L-NAME, in conjunction with an increased oxidative stress. These effects were prevented by SW, and were associated with a decrease in oxidative stress. Superoxide dismutase 2 (SOD-2) and catalase expression increased only in the OSW group. However, no significant difference was found in the activity of these enzymes. In conclusion, SW prevented the endothelial dysfunction in the coronary bed of ovariectomized SHR associated with an increase in the expression of antioxidant enzymes, and therefore may prevent coronary heart disease in hypertensive postmenopausal women.

Spirometry improvement after muscular exercise in elite swimmers.

An increased sympathetic activity during muscular effort is a well established physiological response, whose intensity is known to increase with the muscular load. Spirometry was described to improve as an effect of swimming training in healthy and asthmatic subjects, suggesting a decrease in airway resistance The aim was to investigate the possible effect of muscular exercise (swimming) on spirometry, in particular searching for possible differences because of different swimming times. The measurements were performed on 9 highly trained male competitive swimmers (age: 41±12.79 years, height: 1.69±0.06 meters, weight: 66.14±14.28 kg, BMI: 22.8±3.61 kg/m2) during an official competition. The data were collected at the border of the swimming-pool before (control, C) and few minutes after the swimming sessions (exercise, E), which consisted either of 800 meter (7 subjects) or 1500 meter (5 subjects) free style. A general trend indicating a postexercise increase in spirometry was observed. We found post-exercise significant increments in FEV1 and in MEF75 for both the 800 and 1500 meter swimming sessions, and in FEF25-75 and in MEF25 for the shorter distance. We conclude that, as it may be expected, muscular exercise induces an improvement of spirometry both because of a smooth muscle relaxation-induced modulation of airway diameter and resistance to airflow, and because of an enhanced expiratory muscle contraction strength. Both of these mechanisms are related to an increased sympathetic activity which is well known to accompany muscular exercise.

Effects of swim training on energetic and performance in women masters’ swimmers

The aim of this study was to analyze and compare the changes of performance and energetic profile of female masters swimmers over a season, in three distinct time periods (TP): December (TP 1 ), March (TP 2 ) and June (TP 3 ). Eleven female masters swimmers performed an all-out 200 m freestyle to evaluate the swimmers’ energetic adaptations. The 200 m freestyle performance, the total energy expenditure ( E tot ) and the partial contribution of aerobic energy source (% Aer ), partial contribution of anaerobic lactic energy source (% AnL ) and partial contribution of anaerobic alactic energy source (% AnAl ) contributions were estimated or assessed. Female masters swimmers improved significantly the 200 m freestyle performance over a season. However, a non-significant improvement was found on their energetic profile. Hence, one might speculate that performance improvement might be related to other performance determinants, such as, technical enhancement. Aerobic metabolism was the major contributor for E tot whereas anaerobic alactic was the second major contributor.

Adaptation and acclimation of aerobic exercise physiology in Lake Whitefish ecotypes (Coregonus clupeaformis).

The physiological mechanisms underlying local adaptation in natural populations of animals, and whether the same mechanisms contribute to adaptation and acclimation, are largely unknown. Therefore, we tested for evolutionary divergence in aerobic exercise physiology in laboratory bred, size-matched crosses of ancestral, benthic, normal Lake Whitefish (Coregonus clupeaformis) and derived, limnetic, more actively swimming "dwarf" ecotypes. We acclimated fish to constant swimming (emulating limnetic foraging) and control conditions (emulating normal activity levels) to simultaneously study phenotypic plasticity. We found extensive divergence between ecotypes: dwarf fish generally had constitutively higher values of traits related to oxygen transport (ventricle size) and use by skeletal muscle (percent oxidative muscle, mitochondrial content), and also evolved differential plasticity of mitochondrial function (Complex I activity and flux through Complexes I-IV and IV). The effects of swim training were less pronounced than differences among ecotypes and the traits which had a significant training effect (ventricle protein content, ventricle malate dehydrogenase activity, and muscle Complex V activity) did not differ among ecotypes. Only one trait, ventricle mass, varied in a similar manner with acclimation and adaptation and followed a pattern consistent with genetic accommodation. Overall, the physiological and biochemical mechanisms underlying acclimation and adaptation to swimming activity in Lake Whitefish differ.

The Effects Of Swimming Training On The Blood Pressure Of Middle-aged Pre-hypertensive Men.

The Effects Of Swimming Training On The Blood Pressure Of Middle-aged Pre-hypertensive Men.

The effects of swimming training on bone tissue in adolescence.

The aim was to analyze bone mineral content (BMC) and density (BMD) in regular swimming trained adolescents and the interaction that weigh-bearing sports may have on these values. Bone mass was evaluated by dual energy x-ray absorptiometry (DXA) and quantitative ultrasound (QUS) in 77 swimmers (34 females/43 males) and 52 normoactive controls (CG; 23 females/29 males) from 11 to 18 years. Swimmers who had performed or were performing other sports (OSP; 11 females/20 males) were compared with pure swimmers (PSW; 23 females/23 males). Both groups were compared with CG. Bone values were compared using analyses of covariance adjusting for height, calcium intake, subtotal lean (whole body lean minus head), and pubertal status. Male PSW showed lower BMD and BMC at several sites than male CG. However, for male OSP, only lumbar spine BMC was lower in OSP than male CG. Male PSW showed lower BMD and BMC when compared with male OSP. Female PSW showed higher arm BMD and lower leg BMC than female CG, while female OSP only presented lower leg BMC than female CG. Contrary to males, female-PSW presented higher BMD and BMC than female OSP. No differences in QUS values were found between swimmers and CG. To summarize, although more information is needed for females, it seems that for males, swimming is associated with lower BMC and BMD.

Effects of swimming training and estrogen therapy on the vascular reactivity of hypertensive ovariectomized rats: role of renin angiotensin system (706.7)

Effects of swimming training and estrogen therapy on the vascular reactivity of hypertensive ovariectomized rats: role of renin angiotensin system Glaucia R Abreu, Nazare S Bissoli, Ana Ligia R Carvalho, Erick Roberto C Gonçalves, Patrick W Endlich: Health Science Center, Federal University of Espirito Santo, Brazil Several studies showed up regulation of Renin Angiotensin System (RAS) after menopause and the ability of physical training in reduces cardiovascular risk factors. The aim of this study was to analyze the effects of swimming training (eight weeks) and estrogen therapy (5 mg of 17β‐Estradiol, s.c.) on vascular reactivity and the expression of RAS of aorta rings in ovariectomized spontaneously hypertensive rats (SHR). The groups were divided: Sham (S), Ovariectomized (OVX), ovariectomized (OTE2), ovariectomized+swimming ON) and ovariectomized treated with E2 plus swimming (OE2+N). The systolic blood pressure was measured after the animals were sacrificed and blood was collected to measure Angiotensin II plasma levels by radioimmunoassay. Aorta reactivity we evaluated in response to Ang II and Angiotensin‐(1‐7) and RAS proteins expression were made by Western Blotting method. Both exercise and E2 increased Ang II plasma levels. However, the systolic blood pressure was attenuated by treatments. The OVX group showed increase in the constrictor response to Ang II and decrease dilatator response to Ang (1‐7), that was reverted by swimming training or E2 therapy associated to swimming. Moreover, ON and OE2+N groups showed increase in the AT2 and Mas receptor expression. On the other hand, the ON showed increase in the superoxide dismutase (SOD) anti‐oxidant enzyme and only the groups treated with E2 showed increase on eNOS expression. Then both swimming training and E2 treatment may play a non‐additive, role in the cardioprotection and the chronic physical exercise can be a feasible alternative in relation to estrogen therapy in post‐menopausal women.Grant Funding Source: Capes;CNPq

Effects of Swim Training on Energetics and Performance

The aim of this study was to determine the effect of several months of training on performance and energetic profile of elite swimmers. 9 elite swimmers were evaluated at 3 different time periods during the 2010-2011 calendar. Swimming performance was assessed based on lists of times for the 200 m freestyle event. An incremental set of 7×200 m swims was applied to obtain the energetic data. Measurements and/or estimations were made for the: velocity at 4 mmol l(-1) of lactate concentrations, highest value of lactate concentrations, maximal oxygen consumption, minimum swimming velocity where the maximal oxygen consumption is reached and total energy expenditure (Etot). The performance and most of the energetic variables assessed presented no significant variations during the study period. The only exception was the Etot with significant differences between all measurements. Correlation coefficients suggested a high stability for all variables. Cohen's Kappa tracking index demonstrated high variability in the individual adaptations to training. It is concluded that elite swimmers demonstrate a slight improvement in performance and energetic profile in response to several months of training. Each subject has an individual way of adapting to the training load, combining the different energetic confounders to enhance performance.

Effects of swim training on liver carcinogenesis in male Wistar rats fed a low-fat or high-fat diet

The present study aimed to investigate the beneficial effects of swim training on the promotion-progression stages of rat liver carcinogenesis. Male Wistar rats were submitted to chemically induced liver carcinogenesis and allocated into 4 major groups, according their dietary regimen (16 weeks) and swim training of 5 days per week (8 weeks): 2 groups were fed low-fat diet (LFD, 6% fat) and trained or not trained and 2 groups were fed high-fat diet (HFD, 21% fat) and trained or not trained. At week 20, the animals were killed and liver samples were processed for histological analyses; immunohistochemical detection of persistent or remodeling preneoplastic lesions (pPNL and rPNL) expressing placental glutathione S-transferase (GST-P) enzyme; or proliferating cell nuclear antigen (PCNA), cleaved caspase-3, and bcl-2 protein levels by Western blotting or malonaldehyde (MDA) and total glutathione detection by HPLC. Overall analysis indicated that swim training reduced the body weight and body fat in both LFD and HFD groups, normalized total cholesterol levels in the HFD group while decreased the MDA levels, increased glutathione levels and both number of GST-P-positive pPNL and hepatocellular adenomas in LFD group. Also, a favorable balance in PCNA, cleaved caspase-3, and bcl-2 levels was detected in the liver from the LFD-trained group in relation to LFD-untrained group. The findings of this study indicate that the swim training protocol as a result of exercise postconditioning may attenuate liver carcinogenesis under an adequate dietary regimen with lowered fat intake.

Effect of swimming training on the motor behavior and expression of BDNF and trkB in adrenal body

Objective To explore the effect of swimming on motor behavior and expression of brain derived neurotrophic factor(BDNF) and trkB in adrenal body. Methods SD adult rats were divided into normal cotrol group and swimming group (n=10 in each group). All rats in swimming group were subjected 6 weeks swimming for 1h each day.Motor performances including swimming speed and distance were recorded and expression of BDNF and trkB in adrenal body was measured. Results There was a significant increase in swimming speed((157±60)m/min)and distance ((283.36±49.50)m) in swimming group, compared with control group ((283±60)m/min, (156.92±29)m)(P<0.05). Simultaneously, expression of BDNF in adrenal body had been significantly unregulated(0.93±0.09 vs 0.56±0.19)(P<0.05), while expression of trkB kept to be not changed. Conclusion Swimming increases motor ability in rats, and the possible mechanism may be related the upregulation of BDNF in adrenal body. Key words: Rat; Swimming; Adrenal body; Brain derived neurotrophic factor; trkB

Effects of swimming training on tissue glycogen content in experimental thyrotoxic rats

Thyrotoxicosis, a condition in which there is an excessive amount of circulating thyroid hormones, leads to reduced glycogen content in different tissues. In this study we analyzed the effects of aerobic swimming training on liver, heart, and skeletal muscle glycogen content in experimentally induced thyrotoxicosis. Wistar male rats were divided into euthyroid sedentary (ES, n = 12), euthyroid trained (ET, n = 11), thyrotoxic sedentary (TS, n = 12), and thyrotoxic trained (TT, n = 10) groups. Thyrotoxic groups received daily i.p. doses of T4 (sodium levothyroxine, 25 µg/100 g body mass) through the experimental period, and trained groups swam for 1 h at 80% of the aerobic-anaerobic transition intensity, 5 days/week for 4 weeks. Heart and liver glycogen stores were ∼30% lower in T4 treated compared with nontreated groups, but were not changed by training status. On the other hand, glycogen content in mixed fiber type gastrocnemius of TT was 1.5- to 2.3-fold greater than those in other groups, whereas no significant differences were found for the slow soleus muscle. Increased gastrocnemius but not soleus, liver, or heart glycogen indicates that in mild long-term thyrotoxicosis chronic swimming affects glycogen stores in a tissue-specific manner.