The effects of inspiratory muscle training on swimming performance: A study on the cohort of swimming specialization students

PURPOSE

Current evidence posits a strong correlation between respiratory muscle function and swimming performance. Despite this, few studies have explored the integration of inspiratory muscle training (IMT) into standard swimming training regimens, which remains an unexplored avenue for improving performance in swimmers. This study aims to evaluate the potential advantages of IMT for enhancing respiratory function and swimming performance and determine whether such training could induce beneficial physiological adaptations.

METHODS

We designed and conducted a randomized controlled trial involving 43 swimming specialization students aged 18-25 years. Participants were randomly allocated to two groups: a control group, which followed regular swimming training, and an experimental group, which complemented the standard training with IMT. The intervention lasted for six weeks. Key outcomes measured included swimming performance metrics (time of 50 m freestyle, number of breaths in 50 m freestyle, distance before first breath in freestyle, time of 100 m freestyle) and various inspiratory muscle function parameters such as vital capacity (VC), maximum inspiratory pressure (MIP), maximum inspiratory flow (MIF), and maximum inspiratory capacity (MIC). We also assessed certain biochemical parameters, including hemoglobin, creatine kinase (CK), blood urea nitrogen (BUN), testosterone, and cortisol concentrations.

RESULTS

Following the training period, the experimental group exhibited significant improvements in swimming performance and respiratory function parameters. We also noted an increase in hemoglobin levels and a reduction in testosterone concentrations in this group, suggesting beneficial physiological adaptations in response to the combined IMT and swimming training.

CONCLUSION

Our findings underline the potential of IMT as a supplementary training modality for enhancing respiratory function and improving swimming performance. The changes in biochemical parameters suggest physiological adaptations that might contribute to these observed improvements. This study opens the door for future research on the benefits of integrating IMT into training regimens for competitive swimmers. Further investigation is warranted to fully elucidate the mechanisms behind the observed benefits and to validate these findings in a larger cohort and other athlete populations.

Kinematic and electromyography characteristics of performing butterfly stroke with different swimming speeds in flow environment

Objective

To investigate effect of flow speeds on the upper limb muscular activity of butterfly swimmers training in a flow environment. A comparison of kinematic characteristics and muscular activity of upper limbs were made when the swimmers training with different flow speeds in a swimming flume. The purpose was to provide a basis for scientifically formulating special swimming training advice for athletes' training in flow environment.

Methods

Ten youth female butterfly swimmers participated in the study with the speed of 70%, 80%, and 90% level of their max speeds. A stroke cycle was divided into four phases (entry, pull, push, and recovery). The kinematic parameters of upper limbs (stroke rate, stroke length, duration of each phase in a stroke cycle) and muscular activity (onset timing, integrated electromyography (iEMG), contribution ratio) of four muscles (Biceps brachii (BB), Triceps brachii (TB), Pectoralis major (PM), and Latissimus dorsi (LD)) were collected and analyzed in different stroke phases.

Results

There was no significant difference between stroke rate and stroke length with different flow speeds. There were significant differences among the duration of the four stroke phases. The entry phase had the longest duration, the pull phase had the shortest duration, the push phase was longer than the recovery phase, and the recovery phase was shorter than the entry phase. The BB and PM were activated significantly earlier at 90% of target speed than at 80% of target speed, while the TB was activated significantly later than other two speeds. The muscular contribution ratio of the PM was highest in the pull phase and lowest in the pushing phase. The muscular contribution ratio of the BB was significantly lower in the pushing phase than in other three stroke phases. The muscular contribution of the TB was significantly higher in the recovery phase than in other three stroke phases. The muscular contribution ratio of the LD was highest in the pushing phase, and it was significantly higher in pushing phase and recovery phase than in pull phase.

Conclusions

(1) When butterfly athletes training with 70%, 80% and 90% of their max speed in a flow environment, it didn't make significant differences between the kinematic or muscle activation characteristics of the upper limbs movement except the muscle onset timing. (2) Stroke phase was the main factor of the duration and the muscle contribution ratio during butterfly arm stroke for young athletes.

Swimming training reduced inflammation and apoptotic changes in pulmonary tissue in type 1 diabetic mice

Background

Despite the vulnerability of pulmonary tissue to diabetic conditions, there are few reports related to the detrimental effects of hyperglycemia and therapeutic modalities on lung parenchyma. Here, the apoptotic changes were monitored in the diabetic pulmonary tissue of mice (DM1) subjected to a four‒week swimming plan.

Methods

The mice were randomly allocated into Control; Control + Swimming (S); Diabetic group (D); and Diabetic + Swimming (D + S) groups (each in 8 mice). In the D and D + S groups, mice received intraperitoneally 50 mg/kg of streptozotocin (STZ). After 14 days, swimming exercise was done for four weeks. The expression of il-1β, bcl-2, bax, and caspase-3 was investigated using real-time PCR analysis. A histological examination was performed using H&E staining.

Results

DM1 significantly upregulated il-1β, bax, and caspase-3, and down-regulated bcl-2 compared to the non-diabetic mice (p < 0.05). We noted that swimming exercises reversed the expression pattern of all genes in the diabetic mice and closed to basal levels (p < 0.05). Data indicated that swimming exercise could diminish emphysematous changes, and interstitial pneumonitis induced by STZ. Along with these changes, swimming exercise had protective effects to reduce the thickness of the inter-alveolar septum and mean alveolar area in diabetic mice.

Conclusion

These data demonstrated that swimming exercises could decrease DM1-related pathologies in mouse lungs by regulating apoptosis and inflammatory response.

Swimming training and herbal nanoformulations as natural remedies to improve sensory-motor impairment in rat midbrain tumor models: system biology, behavioral test, and experimental validation

Motor impairment worsens health-related quality of life in patients with primary and metastatic midbrain tumors. Here, 56-male-Wistar rats were divided into eight groups: Normal group, Midbrain Tomur Model group, Model + Exe group, Model + Lipo, Model + Extract, Model + Lipo-Extract, Model + Extract-Exe, Model + Lipo-Extract + Exe. According to the aim, mid-brain tumor models were conducted by injections of the C6 glioma cell line (5 × 105 cell suspension) and stereotaxic techniques in the substantia nigra area. Furthermore, consumption of nanoformulation of herbals extract (100 mg/kg/day), crude extract (100 mg/kg/day), and swimming training (30 min, 3 days/week) as interventional protocols were performed for 6 weeks. In addition, we evaluated the effect of polyherbal nanoliposomes containing four plant extracts and swimming training on the GABArα1/TRKB/DRD2/DRD1a/TH network in the substantia nigra of the midbrain tumor rat model. Data emphasized that DRD2 might be a druggable protein with the network's highest significance cut-point effect that could modulate sensory-motor impairment. Furthermore, we found Quercetin, Ginsenosides, Curcumin, and Rutin, as bioactive compounds present in Ginseng, Matthiola incana, Turmeric, and Green-Tea extracts, could bind over the DRD2 protein with approved binding affinity scores. Based on our data, swimming training, and nanoliposome-enriched combined supplements could consider effective complementary medicine for motor impairment recovery induced by the midbrain tumor in the substantia nigra area. Hence, regular swimming training and natural medicines rich in polyphenolic bioactive components and antioxidative effects could modify and improve the dopamine receptors' function.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03574-3.

Swimming training combined with fecal microbial transplantation protects motor functions in rats with spinal cord injury by improving the intestinal system

Spinal cord injury (SCI) leads to severe intestinal dysfunction and decreased motility. There is an interaction between the intestine and the nervous system, intestinal intervention through microbial regulation and exercise is a potential treatment option for spinal cord injury. We investigated the effects of swimming rehabilitation training combined with fecal microbial transplantation on intestinal as well as neurological functions in rats with spinal cord injuries, and explored the potential mechanisms. The animals were randomly divided into five groups: sham-operated control group (Sham), spinal cord injury only group (SCI), swimming training group (Swimming), fecal microbial transplantation group (FMT) and combined interventions group (Combined). Behavioral assessments, pathological and immunological analyses were performed after the interventions. Compared to rats in the spinal cord injury group, rats subjected to swimming training, fecal microbial transplantation and combined interventions group exhibited improved intestinal transit, barrier functions, motility, and motor conduction pathway conductivity(P < 0.05). The combined interventions group had better outcomes(P < 0.01). In addition, combined interventions significantly suppressed inflammatory factor levels (P < 0.05) in the colon and spinal cords and significantly protected forefoot motor neurons (NeuN) in the spinal cord injury area, inhibiting astrocyte activation and reducing the expressions of the signature glial fibrillary acidic protein (GFAP) and markers of microglia (Iba-1) at the lesion site(P < 0.05). In conclusion, all effects of combined swimming training and fecal microbial transplantation interventions were superior to swimming training or fecal microbial transplantation alone. Swimming training and fecal microbial transplantation interventions have a synergistic effect on the recovery of intestinal function and motility after spinal cord injury. The mechanism of mutual facilitation between gut function and motility may be related to the brain-gut axis interaction.

Neurogranin as an important regulator in swimming training to improve the spatial memory dysfunction of mice with chronic cerebral hypoperfusion

BACKGROUND

Vascular cognitive impairment caused by chronic cerebral hypoperfusion (CCH) has become a hot issue worldwide. Aerobic exercise positively contributes to the preservation or restoration of cognitive abilities; however, the specific mechanism has remained inconclusive. And recent studies found that neurogranin (Ng) is a potential biomarker for cognitive impairment. This study aims to investigate the underlying role of Ng in swimming training to improve cognitive impairment.

METHODS

To test this hypothesis, the clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) system was utilized to construct a strain of Ng conditional knockout (Ng cKO) mice, and bilateral common carotid artery stenosis (BCAS) surgery was performed to prepare the model. In Experiment 1, 2-month-old male and female transgenic mice were divided into a control group (wild-type littermate, n = 9) and a Ng cKO group (n = 9). Then, 2-month-old male and female C57BL/6 mice were divided into a sham group (C57BL/6, n = 12) and a BCAS group (n = 12). In Experiment 2, 2-month-old male and female mice were divided into a sham group (wild-type littermate, n = 12), BCAS group (n = 12), swim group (n = 12), BCAS + Ng cKO group (n = 12), and swim + Ng cKO group (n = 12). Then, 7 days after BCAS, mice were given swimming training for 5 weeks (1 week for adaptation and 4 weeks for training, 5 days a week, 60 min a day). After intervention, laser speckle was used to detect cerebral blood perfusion in the mice, and the T maze and Morris water maze were adopted to test their spatial memory. Furthermore, electrophysiology and Western blotting were conducted to record long-term potential and observe the expressions of Ca²⁺ pathway-related proteins, respectively. Immunohistochemistry was applied to analyze the expression of relevant markers in neuronal damage, inflammation, and white matter injury.

RESULTS

The figures showed that spatial memory impairment was detected in Ng cKO mice, and a sharp decline of cerebral blood flow and an impairment of progressive spatial memory were observed in BCAS mice. Regular swimming training improved the spatial memory impairment of BCAS mice. This was achieved by preventing long-term potential damage and reversing the decline of Ca²⁺ signal transduction pathway-related proteins. At the same time, the results suggested that swimming also led to improvements in neuronal death, inflammation, and white matter injury induced by CCH. Further study adopted the use of Ng cKO transgenic mice, and the results indicated that the positive effects of swimming training on cognitive impairments, synaptic plasticity, and related pathological changes caused by CCH could be abolished by the knockout of Ng.

CONCLUSION

Swimming training can mediate the expression of Ng to enhance hippocampal synaptic plasticity and improve related pathological changes induced by CCH, thereby ameliorating the spatial memory impairment of vascular cognitive impairment.

Vitamin D supplementation combined with aerobic physical exercise restores the cell density in hypothalamic nuclei of rats exposed to monosodium glutamate

BACKGROUND & AIMS

In view of the increase in the prevalence of obesity and metabolic syndrome in childhood and adolescence, this study proposed the early and combined use of treatments to restore brain areas related to satiety. The vitamin D supplementation, aerobic exercise and the combination of these interventions on the structure of arcuate (ARC) and ventromedial (VMH) nuclei of hypothalamus were investigated in monosodium glutamate (MSG)-treated rats.

METHODS

Wistar rats were separated into five groups: Control group (CT); Obese group injected with MSG (OB); Obese group supplemented with vitamin D (OBvd); Obese group submitted to forced swimming training (OBexe) and Obese group treated with vitamin D supplementation and forced swimming training (OBvd + exe).

RESULTS

In the OB group, the visceral fat weight was significantly higher, there was a reduction in the number of glial cells in the ARC nucleus and also in the number of neurons in the ARC and VMH nuclei. Aerobic exercise was able to reduce the visceral fat weight in the OBexe group. The combination of treatments used in the OBvd + exe group reversed the loss of neurons and glial cells produced by MSG in the ARC nucleus. All treated groups exhibited a higher number of neurons in VMH nucleus, but an increase in the glial cells were observed only in the OBexe and OBvd + exe groups.

CONCLUSIONS

The effectiveness of obesity treatment can be favored through the early and combined use of vitamin D supplementation and aerobic exercise, since these therapies are able to restore brain nuclei involved in the control of food intake.

Swimming training combined with chitosan supplementation reduces the development of obesity and oxidative stress in high-fat diet-fed mice

Obesity is often introduced as one of the metabolic disorders caused by imbalance between energy consumption and metabolisable energy intake. Experts in the field considered obesity as one of the robust risk factors for the lifestyle-associated diseases. The present research examined interventional effects of marine chitosan (CS), swimming training (ST) and combination of CS and ST (CS + ST) in the mice fed with high-fat diets (HFD). In this study, sample size was considered more than three in groups. Forty mice were randomly divided into five groups (n 8 per group) including control group (received the standard diet), HFD group (received high-fat food with 20 % fat), HFD + CS group (treated with high-fat food with 5 % CS), HFD + ST group (treated with HFD and ST) and HFD + CS + ST group (treated with high-fat food with 5 % CS and ST). After 8 weeks, the blood glucose, oxidative stress (OS) and lipid profile were measured. The results showed that CS + ST group has more effects in the control of body weight with the increased concentration of HDL-cholesterol, OS inhibition via enhancing the body antioxidant capacity in comparison with the ST or CS alone in HFD-fed mice. Moreover, lipid profile was improved in CS + ST-treated mice compared with HFD-treated mice, and OS inhibition correlated with the greater activities of the antioxidant enzyme enhances the lipid oxidation, cholesterol and fatty acid homoeostasis. The results suggested that a dietary intervention with a combined ST and CS can be a feasible supplementary for human prevention of obesity.

Swimming training and Plantago psyllium ameliorate cognitive impairment and glucose tolerance in streptozotocin-nicotinamide-induced type 2 diabetic rats

Brain malfunction is common in diabetic patients. On the other hand, a growing body of research points to the beneficial effect of medicinal plants and exercise training on insulin sensitivity and brain function. Therefore, the aim of the present study was to investigate the effect of co-administration of swimming training and Plantago psyllium (mixed with standard pelleted food at a weight ratio of 5%) on learning and memory impairment and glucose tolerance in type 2 diabetic rats. For this purpose, 10 healthy and 40 rats with type 2 diabetes were randomly allocated to five groups: healthy sedentary control group (Con), sedentary diabetic group (D), diabetic group subjected to swimming training (D + Tr), diabetic group receiving P. psyllium (D + Ps), and diabetic group subjected to swimming training and receiving P. psyllium (D + Ps + Tr). Diabetes was induced by a single intraperitoneal injection of nicotinamide (120 mg/kg) and streptozotocin (65 mg/kg) separately with 15 min intervals. Experimental groups were treated with swimming training and P. psyllium independently and simultaneously for 12 weeks. Lipid profile and food intake were measured and also, glucose tolerance was evaluated by glucose area under the curve (AUCg) using an oral glucose tolerance test. Passive avoidance learning (PAL) and memory were evaluated by shuttle box test and cognitive memory was assessed by novel object recognition (NOR) and elevated plus-maze (EPM) tests. Diabetic rats exhibited a significant increase in food intake, lipid profile, and AUCg compared to healthy rats. Step-through latency in the PAL acquisition trial (STL-a) and retention test (STL-r) were significantly lower in diabetic rats than in the control group. In the diabetic group without treatment, time spent in the dark compartment increased compared to the control group in the shuttle box test. Discrimination index and distance traveled reduced in diabetic rats. On the other hand, swimming training and P. psyllium alleviated food intake, lipid profile, and glucose tolerance in diabetic rats. Also, the STL-a, STL-r, discrimination index, and distance travelled in the D + Ps + Tr group were significantly more than the diabetic group. Results showed that 12 weeks of swimming training and receiving P. psyllium improved memory deficit in streptozotocin-nicotinamide-induced type 2 diabetic rats possibly through hypolipidemic and hypoglycemic effects. These results suggest that the administration of swimming training and P. psyllium simultaneously might be an effective intervention for the treatment of diabetes-induced behavioral deficits.

Melatonin and prolonged physical activity attenuated the detrimental effects of diabetic condition on murine cardiac tissue

In this study, the combined effects of four-week swimming training and melatonin were examined on the oxidative response, inflammation, apoptosis, and angiogenesis capacity of cardiac tissue in the mouse model of diabetes. The mice were randomly allocated into five groups (n = 10 per group) as follows: Control; Diabetic group; Diabetic + Melatonin group; Diabetic + Exercise group; and Diabetic + Exercise + Melatonin group. 50 mg/kg streptozotocin was intraperitoneally administrated. In melatonin-treated groups, melatonin was injected intraperitoneally at 3 mg/kg body weight for four weeks and twice weekly. Swimming exercises were performed for four weeks. We measured cardiac superoxide dismutase, glutathione peroxidase enzymes, malondialdehyde, and total antioxidant capacity. The expression of tumor necrosis factor-α, Caspase‑3, Sirtuin1, and Connexin-43 was measured using real-time PCR analysis. The vascular density was analyzed by immunohistochemistry using CD31 and α-smooth muscle actin antibodies. The combination of melatonin and exercise elevated cardiac superoxide dismutase, glutathione peroxidase coincided with the reduction of malondialdehyde and increase of total antioxidant capacity as compared to the diabetic mice (p < 0.05). In Diabetic + Exercise + Melatonin mice, tumor necrosis factor-α, Caspase‑3 was significantly down-regulated compared to the Diabetic group (p < 0.05). Melatonin and exercise suppressed the expression of Connexin-43 and Sirtuin1 in diabetic mice in comparison with the control mice (p < 0.05). H & E staining showed necrosis and focal hyperemia reduction in the Diabetic + Exercise + Melatonin group compared to the Diabetic group. Data showed a decrease of CD31+ and α-smooth muscle actin+ vessels in the Diabetic group as compared to the normal samples (p < 0.05). The number of CD31+ vessels, but not α-smooth muscle actin+ type, increased in the Diabetic + Exercise + Melatonin group compared to the Diabetic mice. These data demonstrated that exercise along with melatonin administration could diminish the detrimental effects of diabetes on cardiac tissue via using different mechanisms.

Swimming training reduces iNOS expression, augments the antioxidant defense and reduces sympathetic responsiveness in the rostral ventrolateral medulla of normotensive male rats

We sought to investigate whether RVLM iNOS activity and oxidative profile may participate in the reduction of sympathetic responsiveness in swimming trained normotensive rats. Sedentary (S) and swimming trained (T) Wistar male rats chronically instrumented with an arterial catheter and guide cannula into the RVLM were submitted to continuous pressure and heart rate (HR) recordings and determination of autonomic control (power spectral analysis) before and after unilateral RVLM iNOS inhibition (aminoguanidine, 250 pmol/100 nL). Other S and T rats received local l-glutamate microinjection (5 nmol/100 nL). In separate S and T groups not submitted to brainstem cannulation, fresh bilateral RVLM punchs were collected for iNOS gene expression (qPCR); reduced glutathione and lipid peroxidation quantification (spectrophotometry); iron-reducing antioxidant (FRAP) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS˙⁺) scavenger assays. iNOS gene expression was confirmed in fixed RVLM slices (immunofluorescence). T rats exhibited resting bradycardia, lower sympathovagal balance, reduced RVLM iNOS gene/protein expression and higher antioxidant capacity. Decreased iNOS expression was positively correlated with reduced HR. Pressor and tachycardic response to l-Glutamate were smaller in T rats. Aminoguanidine microinjection reduced sympathetic activity in S rats but did not change it in T rats expressing reduced RVLM iNOS content. Our data indicate that iNOS, expressed in the RVLM of normotensive male rats, has tonic effects on sympathetic activity and that swimming training is an efficient tool to reduce iNOS expression and augment the antioxidant defense, thus reducing glutamatergic responsiveness and sympathetic drive to cardiovascular effectors.

Swimming training attenuates pancreatic apoptosis through miR-34a/Sirtu in1/P53 Axis in high-fat diet and Streptozotocin-induced Type-2 diabetic rats

Objective

The present study sought to evaluate the miR-34a/Sirtuin1/p53 pro-apoptotic pathway, and reveal its modulation in diabetic rats undergoing swimming exercise.

Methods

Twenty-eight male Wistar rats were divided into four groups. They were inducted to develop diabetes by injection of streptozotocin. After 12 weeks of swimming, the pancreatic tissue of these rats were removed to be evaluated for the expression level of Sitruin1/P53/miR-34a through qPCR.

Results

Findings indicated a marked rise in the expression of miR-34 and P53 (P < 0.01) as well as a significant decrease in expression of Sitruin1 (P < 0.01) in the diabetic group. In contrast, swimming resulted in a significant decrease in miR-34a expression (P < 0.01), and a prominent rise in the level of Sitruin1 in the swimming-trained-diabetic group (P < 0.01). Additionally, high, moderate and low apoptosis rate were observed in the pancreatic tissue of the diabetic, swimming-trained diabetic, and control groups, respectively.

Conclusion

Our findings suggested a correlation between pancreatic tissue apoptosis rate and miR-34a/Sitruin1/p53 signaling, that was subject to modulation by training.

Graphical abstract

The Effects of Maternal Atrazine Exposure and Swimming Training on Spatial Learning Memory and Hippocampal Morphology in Offspring Male Rats via PSD95/NR2B Signaling Pathway

Atrazine (ATR), a widely used herbicide, has been previously shown to damage spatial memory capability and the hippocampus of male rats during the development. It has also been indicated that physical exercise can improve learning and memory in both humans and animals, as a neuroprotective method. Our aim here was to investigate the effect of maternal ATR exposure during gestation and lactation on spatial learning and memory function and hippocampal morphology in offspring and to further evaluate the neuroprotective effect of swimming training and identify possible related learning and memory signaling pathways. Using Sprague-Dawley rats, we examined behavioral and molecular biology effects associated with maternal ATR exposure, as well as the effects of 8 or 28 days swimming training. Maternal exposure to ATR was found to impair spatial learning and memory by behavioral test, damage the hippocampal morphology, and reduce related genes and proteins expression of learning and memory in the hippocampus. The extended, 28 days, period of swimming training produced a greater amelioration of the adverse effects of ATR exposure than the shorter, 8 days, training period. Our results suggest that maternal ATR exposure may damage the spatial learning and memory of offspring male rats via PSD95/NR2B signaling pathway. The negative effect of ATR could be at least partially reversed by swimming training, pointing to a potential neuroprotective role of physical exercise in nervous system diseases accompanying by learning and memory deficit.

Swimming improves cognitive reserve in ovariectomized rats and enhances neuroprotection after global cerebral ischemia

Cognitive reserve has been proposed to account for different responses to brain damage or pathology. Factors implicated to influence cognitive reserve include cognitive engagement, physical activity, leisure activities, stress levels, and diet. Furthermore, long-term ovariectomy (OVX), such as occurs in women that have underwent surgical menopause, has been reported to increase the risk of cognitive impairment. In the current study, we examined whether swimming improves cognitive function in long-term OVX-rats. We also examined the neuroprotective effect of swimming after global cerebral ischemia (GCI) and explored the effect of swimming preconditioning on activation of the MAPK cascade signaling pathway, synaptic proteins and brain-derived growth factor (BDNF) - all factors implicated in regulating synaptic plasticity and neuroprotection in the brain. Adult Sprague-Dawley OVX-rats were randomly assigned into four groups: Sham (Sh), Sham + Swimming (Sh + Sw), Ischemia/Reperfusion (IR) and IR + Sw. Our results revealed that (1) Morris water maze and shuttle box test analysis revealed that swimming improved cognitive function in OVX-rats, (2) The levels of PSD95 and synaptophysin, as well as the protein expression of p-ERK, p-CREB and BDNF were all increased in the hippocampus after swimming with or without GCI, and (3) Swimming also increased the number of surviving neurons and IL4 protein expression, while decreasing the Iba1 (a microglia marker) level in the hippocampus. In conclusion, our study demonstrates that swimming improves memory in OVX-rats, and that swimming preconditioning enhances the neuroprotective ERK1/2/CREB/BDNF pathway signaling and ameliorates brain damage after GCI in OVX-rats, which may be closely related to induction of an IL4-mediated anti-inflammatory mechanism.

Active recovery intervals restore initial performance after repeated sprints in swimming

The purpose of this study was to examine the effects of active recovery (AR) and passive recovery (PR) using short (2-min) and long (4-min) intervals on swimming performance. Twelve male competitive swimmers completed a progressively increasing speed test of 7 × 200-m swimming repetitions to locate the speed before the onset of curvilinear increase in blood lactate concentration (LT₁). Subsequently, performance time of 6 × 50-m sprints was recorded during four different conditions: (i) 2-min PR (PR-2), (ii) 4-min PR (PR-4), (iii) 2-min AR (AR-2) and (iv) 4-min AR (AR-4) intervals. Blood lactate concentration was measured before the first and after the last 50-m repetition. AR was applied at an intensity corresponding to LT₁. Performance as indicated by the time needed to complete 6 × 50-m sprints was impaired after AR-4 compared to PR-4 (AR-4: 28.65 ± 1.04, PR-4: 28.17 ± 0.72 s; mean% difference: MD% ±s; ±90% confidence limits: 90%CL, 1.71 ± 3.01%; ±1.43%, p = .01) but was not different between AR-2 compared to PR-2 conditions (AR-2: 28.68 ± 0.85, PR-2: 28.69 ± 0.82 s; MD%: 0.03 ± 1.61%; 90%CL ± 0.77%, p = .99). Performance in sprint-6 was improved after AR compared to PR independent of interval duration (AR: 28.55 ± 0.81, PR: 29.01 ± 1.03 s; MD%: 1.52 ± 2.61%; 90%CL ± 1.2%; p = .03). Blood lactate concentration was lower after AR-4 compared to PR-4 but did not differ between AR-2 and PR-2 conditions. In conclusion, AR impaired performance after a 4-min but not after a 2-min interval. A better performance during sprint-6 after AR could be attributed to a faster metabolic recovery or anticipatory regulatory mechanisms towards the end of the series especially when adequate 4-min active recovery interval is applied.

SOD2 gene polymorphism may modulate biochemical responses to a 12-week swimming training

The aim of the study was to analyze the effect of SOD2 Val16Ala polymorphism on blood biochemical response to chronic swimming training. Healthy men (students of physical education) participated in a swimming training program (ST group) or served as a control group (CON group). The swimming training program lasted 12 weeks (1.5h per day; 4 days per week). Fasting blood samples were obtained prior to (pre) and after (post) a 12-week study period, to measure the biomarkers of oxidative stress, muscle damage and lipid profile. No significant changes in the study parameters were documented in CON group after a 12-week study period, either overall or among carriers of specific SOD2 Val16Ala genotypes. In ST group, post-training decrease in serum lipid hydroperoxides (p < 0.05) and creatine kinase activity (p < 0.05) was associated with Ala/Ala genotype of SOD2 Val16Ala polymorphism. In turn, the increase in serum activity of superoxide dismutase (p < 0.05) was associated with Val carriers, and Val/Val genotype additionally predisposed to the post-training increase in total glutathione level in whole blood (p < 0.05). Moreover, in ST group, a 12-week swimming training program induced an increase in serum concentration of total cholesterol (p < 0.05), which resulted from an increase in both high density (p < 0.05) and low density lipoprotein cholesterol (p < 0.05). The change in high density lipoprotein cholesterol level was irrespective of the genotype. Also, a tendency to post-training increase in both total and low density lipoprotein cholesterol was observed in all three genotypes, although these changes were significant solely in Ala/Val genotype carriers (p < 0.05). In conclusion, 12-week swimming training induces changes in oxidative stress and muscle damage parameters, as well as in lipid profile. These changes seem to be associated with the presence of SOD2 Val16Ala polymorphism. Presence of Ala allele, especially as homozygote, is associated with some beneficial post-training changes, such as a decrease in lipid peroxidation and less pronounced muscle damage. In turn, the influence of SOD2 Val16Ala polymorphism on the changes in lipid profile in response to chronic swimming training should be verified in further study.

Effects of 8-week swimming training on carotid arterial stiffness and hemodynamics in young overweight adults

BACKGROUND

Exercise has been found to either reduce or increase arterial stiffness. Land-based exercise modalities have been documented as effective physical therapies to decrease arterial stiffness. However, these land-based exercise modalities may not be suitable for overweight individuals, in terms of risks of joint injury. The purpose of this study was to determine the effects of 8-week swimming training and 4-week detraining on carotid arterial stiffness and hemodynamics in young overweight adults.

METHODS

Twenty young male adults who were overweight were recruited and engaged in 8-week of swimming training and 4-week detraining. Five individuals withdrew due to lack of interest and failure to follow the training protocol. Body Fat Percentage (BFP) and carotid hemodynamic variables were measured on a resting day at the following intervals: baseline, 4 weeks, 8 weeks after swimming training and 4 weeks after detraining. A repeated analysis of variance (ANOVA) was used to assess the differences between baseline and each measurement. When significant differences were detected, Tukey's test for post hoc comparisons was used.

RESULTS

Eight-week swimming training at moderate intensity decreased BFP, including the trunk and four extremities. Additionally, the BFP of the right and left lower extremities continued to decrease in these overweight adults 4 weeks after ceasing training. Carotid arterial stiffness decreased, while there were no significant changes in arterial diameters. Blood flow velocity, flow rate, maximal and mean wall shear stress increased, while systolic blood pressure and peripheral resistance decreased. No significant differences existed in minimal wall shear stress and oscillatory shear stress.

CONCLUSIONS

Eight-week swimming training at moderate intensity exhibited beneficial effects on systolic blood pressure, arterial stiffness and blood supply to the brain in overweight adults. Moreover, maximal and mean wall shear stress increased after training. It is worth noting that these changes in hemodynamics did not last 4 weeks. Therefore, further studies are still warranted to clarify the underlying relationship between improvements in arterial stiffness and alterations in wall shear stress.

Effects of high-intensity swimming training on the bones of ovariectomized rats

[Purpose]

This study was performed to assess the effects of high-intensity intermittent swimming training(HIT) on bone in ovariectomized rats.

[Methods]

Six-week-old female Sprague-Dawley rats were randomly assigned to either sham operation or bilateral ovariectomy. After surgery, they were divided into the following four groups: 1) sham-operated sedentary (S), 2) sham-operated exercise training (SE), 3) OVX sedentary (O), 4) OVX exercise training (OE) 5) OVX given 17β-estradiol (OE2) and 6) OVX exercise training and given 17β-estradiol (OEE). SE, OE and OEE rats were used extremely high-intensity swim exercise. The rats repeated fourteen 20-s swimming bouts with a weight equivalent to 14, 15, and 16% of body weight for the first 5, the next 9, and the last 5 days, respectively. Between exercise bouts, a 10-s pause was allowed. HIT was originally designed as an exercise method; a method that very quickly induces an increase in the maximum oxygen intake (Tabata I et al., 1996). OEE and OE2 rats were subcutaneously injected ethanol with 25μg/kg body weight 17β-estradiol 3 times per week.

[Results]

Bone strength, bone mineral density and trabecular bone parameters were measured after a 8-weeks experimental period. Bone strength was significantly higher in the SE, OE, OE2 and OEE group compared with the O group. BV/TV was significant increase in the SE, OE groups compared with the O group. BMD showed no difference in the OE group compared with the O group.

[Conclusion]

This study demonstrate some beneficial effects of postmenopausal osteoporosis of high-intensity intermittent swimming training on bone structure and strength.

Age-related changes in the brain antioxidant status: modulation by dietary supplementation of Decalepis hamiltonii and physical exercise

The synergistic effects of physical exercise and diet have profound benefits on brain function. The present study was aimed to determine the effects of exercise and Decalepis hamiltonii (Dh) on age-related responses on the antioxidant status in discrete regions of rat brain. Male Wistar albino rats of 4 and 18 months old were orally supplemented with Dh extract and swim trained at 3 % intensity for 30 min/day, 5 days/week, for a period of 30 days. Supplementation of 100 mg Dh aqueous extract/kg body weight and its combination with exercise significantly elevated the antioxidant enzyme activities irrespective of age. Age-related and region-specific changes were observed in superoxide levels, and protein carbonyl and malondialdehyde contents, and were found to be decreased in both trained and supplemented groups. Levels of total thiols, protein, and nonprotein thiols decreased with age and significantly increased in the SW-T(+100 mg) groups. Our results demonstrated that the interactive effects of two treatments enhanced the antioxidant status and decreased the risk of protein and lipid oxidation in the rat brain.

Expression of the Mir-133 and Bcl-2 could be affected by swimming training in the heart of ovariectomized rats

OBJECTIVES

The beneficial and more potent role of exercise to prevent heart apoptosis in ovariectomized rats has been known. The aim of this study was to examine the effects of swimming training on cardiac expression of Bcl-2, and Mir-133 levels and glycogen changes in the myocyte.

MATERIALS AND METHODS

Forty animals were separated into four groups as control, sham, ovariectomy (OVX) and ovariectomized group with 8 weeks swimming training (OVX.E). Training effects were evaluated by measuring lipid profiles, Bcl-2 and Mir-133 expression levels in the cardiac tissue. Grafts were analyzed by reverse transcription-polymerase chain reaction for Bcl-2 mRNA and Mir-133 and by Western blot for Bcl-2 protein.

RESULTS

Ovariectomy down-regulated Bcl-2 and Mir-133 expression levels in the cardiac tissue, and swimming training up-regulated their expression significantly (P<0.05).

CONCLUSION

Our results showed that regular exercise as a physical replacement therapy could prevent and improve the effects of estrogen deficiency in the cardia.