Effects of different lengths of high-intensity interval training microcycles on the systemic and hippocampal inflammatory state and antioxidant balance of immature rats.

There is a lack of evidence on the effects of high-intensity interval training (HIIT) microcycle duration on the antioxidant capacity and hippocampal inflammatory response of young (immature) samples. This study compared two HIIT microcycles lengths on adaptation to training, antioxidant balance, and systemic and hippocampal inflammation in immature rats. Twenty-four immature Wistar rats (27 days) were equally divided into groups: control; 4-day HIIT (3 training days + 1 rest day); and 7-day HIIT (6 training days + 1 rest day). Both microcycles of 4 and 7 days were 28 days of training (37-38 m min-1). Running performance improved in all training groups compared to controls (P < 0.05). However, the 7-day HIIT group statistically increased serum interleukin-6 (IL-6) compared to the control and 4-day HIIT groups (P < 0.05). The total serum antioxidant capacity in the 7-day HIIT group was statistically lower than in the control group (P < 0.05). There was no statistical difference for the analysis of serum malondialdehyde between the groups. The hippocampal gene expression of IL-6, IL-1ß, IL-10, and tumor necrosis factor-alpha in the training groups was statistically higher than in the control group (P = 0.01), with no significant difference between the 4-day HIIT and 7-day HIIT groups. We concluded that HIIT microcycles with a longer duration decrease the antioxidant capacity and increase the systematic and hippocampal inflammation. Thus, we suggest using short HIIT microcycles for young (immature) groups due to improved running performance with less inflammatory and antioxidant changes.

Muscle gene expression of CGRP-α, CGRP receptor, nAchR-ß, and GDNF in response to different endurance training protocols of Wistar rats.

The neuromuscular junction underwent adaptations to meet the demands of muscles following increased muscle activity. This study aimed to investigate the effects of high-intensity interval training (HIIT), endurance training (END), and mixed interval training (MIX) on the gene expression of the calcitonin gene-related peptide-α (CGRP-α), CGRP receptor, nicotinic acetylcholine receptors (nAchR)-ß and glial-derived neurotrophic factor (GDNF) among different muscle types. Male Wistar rats were randomly divided into four groups: Control (n = 8), END (n = 8), HIIT (n = 8), and MIX (n = 8). The animals run each training protocol for 8 weeks (five sessions/week). Forty-eight hours after the last training session, the muscles gastrocnemius and soleus were excised under the sterilized situation. After collection, the material was prepared for RNA extraction, Reverse Transcriptase reaction, and qPCR assay. The HIIT training up-regulated the CGRP-α (p < 0.01), CGRP-Rec (p < 0.01), and GDNF (p < 0.01) in soleus as well as the nAchR-ß (p < 0.01) and GDNF (p < 0.01) in gastrocnemius muscles. END training down-regulated the gene expression of CGRP-α (p < 0.01), and nAchR-ß (p < 0.01) in gastrocnemius but up-regulated nAchR-ß (p = 0.037) in soleus and GDNF (p < 0.01) in gastrocnemius muscles. MIX training did not show any significant up or down-regulation. The endurance performance of HIIT and MIX groups was higher than the END group (p < 0.01). All studied genes up-regulated by HIIT training in a muscle type-specific manner. It seems that the improvement of some synaptic indices induced by HIIT resulted in the improvement of endurance performance.

Emergence and Progression of Behavioral Motor Deficits and Skeletal Muscle Atrophy across the Adult Lifespan of the Rat.

The facultative loss of muscle mass and function during aging (sarcopenia) poses a serious threat to our independence and health. When activities of daily living are impaired (clinical phase), it appears that the processes leading to sarcopenia have been ongoing in humans for decades (preclinical phase). Here, we examined the natural history of sarcopenia in male outbred rats to compare the occurrence of motor behavioral deficits with the degree of muscle wasting and to explore the muscle-associated processes of the preclinical and clinical phases, respectively. Selected metrics were validated in female rats. We used the soleus muscle because of its long duty cycles and its importance in postural control. Results show that gait and coordination remain intact through middle age (40-60% of median lifespan) when muscle mass is largely preserved relative to body weight. However, the muscle shows numerous signs of remodeling with a shift in myofiber-type composition toward type I. As fiber-type prevalence shifted, fiber-type clustering also increased. The number of hybrid fibers, myofibers with central nuclei, and fibers expressing embryonic myosin increased from being barely detectable to a significant number (5-10%) at late middle age. In parallel, TGFß1, Smad3, FBXO32, and MuRF1 mRNAs increased. In early (25-month-old) and advanced (30-month-old) aging, gait and coordination deteriorate with the progressive loss of muscle mass. In late middle age and early aging due to type II atrophy (>50%) followed by type I atrophy (>50%), the number of myofibers did not correlate with this process. In advanced age, atrophy is accompanied by a decrease in SCs and ßCatenin mRNA, whereas several previously upregulated transcripts were downregulated. The re-expression of embryonic myosin in myofibers and the upregulation of mRNAs encoding the γ-subunit of the nicotinic acetylcholine receptor, the neuronal cell adhesion molecule, and myogenin that begins in late middle age suggest that one mechanism driving sarcopenia is the disruption of neuromuscular connectivity. We conclude that sarcopenia in rats, as in humans, has a long preclinical phase in which muscle undergoes extensive remodeling to maintain muscle mass and function. At later time points, these adaptive mechanisms fail, and sarcopenia becomes clinically manifest.

Prediction of elite athletes' performance by analysis of peak-performance age and age-related performance progression.

The aim of this study was to analyse age-related performance progression and peak-performance age (PPA) in elite track and field athletes and to use a model to predict peak performance. Best performances of world-class athletes from ages 14 to 15 y up to and including the last Olympic year (n = 798), all-time top lists (n = 444), and world record-holders (n = 43) were considered in all 22 disciplines for men and 21 disciplines for women. A discipline/sex-specified model was used by applying dynamic panel data methods to analyze the performance trends. Profile analysis showed that PPA of all-time top list throwers was higher than middle-distance runners (P < 0.001), distance runners (P < 0.05), and jumpers (P < 0.05) in men and higher (P < 0.05) than middle-distance runners in women. Olympic year top list athletes showed that PPA of women throwers was higher than sprinters (P < 0.001) and middle-distance runners (P < 0.05), and PPA of women distance runners was higher (P < 0.05) than sprinters. In both all-time (P < 0.05) and Olympic year (P < 0.05) top lists, the PPA of men race walkers was higher than middle-distance runners. Performance over the preceding 1-2 years (in all disciplines), height (in Long Jump Men; Long Jump Women; Triple Jump Men) and weight (in Discus Throwing Men) indices, respectively, are important (P < 0.05) for predicting future records with different coefficients in different disciplines. The models provide a useful tool for coaches to predict peak performance records and PPA of their athletes which may be of benefit with goal-setting and evaluation of performance progression at different ages in track and field athletics.

Deceptive intensities: An exploratory strategy for overcoming early central fatigue in resistance training.

Neuropsychological stress induced by misleading information can limit human performance, possibly by early central fatigue mechanisms. In this study, we investigated the impact caused by prescribing misleading intensities of resistance exercise on acute electroencephalogram (EEG) and electromyogram (EMG) responses and the total number of repetitions to exhaustion. Collegiate female students performed three sets of biceps curls to exhaustion. The actual intensity for all sets was set at 65% 1-Repetition Maximum (1-RM). However, participants were deceptively informed that the intensities were 60%, 65%, or 70% 1-RM. The number of repetitions to fatigue and the magnitude of EEG and EMG signals were analyzed. The number of repetitions to exhaustion was significantly lower in greater announced intensities (18.11 ± 8.44) compared to lower (29.76 ± 16.28; p = 0.017) and correctly (27.82 ± 11.01; p = 0.001) announced intensity. The correlation between frontal and motor-cortex signals was significant in lower (r = 0.72, p = 0.001) and higher (r = 0.64, p = 0.005) announced intensities. The median and mean frequencies of EMG signal and Root Mean Square (RMS) did not show any significant difference between sets, but the peak-to-peak range (PPR) of biceps EMG signals was significantly higher in lower intensity (0.145 ± 0.042) when compared with higher (0.104 ± 0.044; p = 0.028) or correctly (0.126 ± 0.048; p = 0.037) announced intensity. It seems that deceptive information regarding the mass of an object could affect the number of repetitions to exhaustion and PPR to cover muscle capacity in endurance-type strength training.

Muscle hypertrophy is correlated with load progression delta, climb volume, and total load volume in rodents undergoing different ladder-based resistance training protocols.

We compared the effects of two ladder-based resistance training (LRT) protocols on the skeletal muscle morphology (biceps brachialis and plantaris) of Wistar rats. Also, we correlated the training parameters with the muscle fiber cross-sectional area (fCSA). After maximum load tests (ML), twenty-nine young adult Wistar rats were divided into: CONTROL (n = 9), LIMITED (n = 10, 6-8 climb [2 × 50 %ML, 2 × 75 %ML, 2 × 100 %ML, and 2 × 100 %ML+30 g]) and UNLIMITED (n = 10, ≥4 climbs [50 %ML, 75 %ML, 90 %ML, 100 %ML + 30 g until failure) LRT. After eight weeks, the main results were: 1) For biceps brachialis, the type I, IIa, and mean fCSA was statistically larger in the LIMITED than CONTROL. The nuclei/fiber ratio was statistically higher in the LIMITED and UNLIMITED. The correlations found between total load, absolute delta load, and relative load and fCSA were moderate. 2) For plantaris, the type I, IIa, IIx/b, and mean fCSA was statistically larger in the LIMITED than CONTROL. The type IIa, IIx/b, and mean fCSA was statistically larger in the UNLIMITED than CONTROL. The nuclei/fiber ratio was statistically higher in both trained groups than CONTROL. The correlation between the climbing number, total load, and the fCSA was moderate. The correlation between delta absolute load and fCSA was strong. We concluded that rodents submitted to high-intensity, high-volume LRT, but limited climbing volume per session, presented more significant type I, IIa, IIx/b, and mean fCSA, higher nuclei/fiber ratio, and greater maximum carrying capacity. Also, muscle hypertrophy correlated positively with the load progression, training volume, and total load.

Training Intensity, Not Duration, May Be Key to Upregulating Presynaptic Proteins of Calcium Dynamics and Calcium-Dependent Exocytosis in Fast- and Slow-Twitch Skeletal Muscles, in Addition to Maintaining Performance After Detraining.

Neuromuscular adaptations are essential for improving athletic performance. However, little is known about the effect of different endurance training protocols and their subsequent detraining on the gene expression of critical factors for neuromuscular synaptic transmission. Therefore, this study investigated the effects of endurance training (high-intensity interval training [HIIT], continuous [cEND], mixed interval [Mix], and all protocols combined [Comb]) and detraining on performance and gene expression (GE) of the alpha-1a, synaptotagmin II (Syt-II), synaptobrevin II (Vamp2), and acetylcholinesterase (AChE) in the gastrocnemius and soleus of Wistar rats. Eighty rodents were randomly divided into control, HIIT, cEND, Mix, Comb, and detraining groups. The rodents trained for 6 weeks (5 × /week), followed by 2 weeks of detraining. Performance improved in all training groups and decreased following detraining (p < 0.05), except HIIT. In the gastrocnemius, alpha-1a GE was upregulated in the Mix. Syt-II and AChE GE were upregulated in HIIT, Mix, and Comb. Vamp2 GE was upregulated in all groups. In the soleus, alpha-1a GE was upregulated in HIIT, Mix, and Comb. Syt-II and Vamp2 GE were upregulated in all groups. AChE GE was upregulated in cEND, Mix, and Comb. Detraining downregulated mostly the gene expression in the skeletal muscles. We conclude that training intensity appears to be a key factor for the upregulation of molecules involved in neuromuscular synaptic transmission. Such changes occur to be involved in improving running performance. On the other hand, detraining negatively affects synaptic transmission and performance.

The Effect of Precooling on Exhaustive Performance in the Hot Environment.

BACKGROUND: Pre-cooling is known to enhance exercise performance in soccer players. However, little information currently exists regarding precooling effects in Iranian young soccer players. OBJECTIVES: The aim of this study was to assess the effect of precooling (water immersion) on exhaustive performance in the heat ( temperature = 32 - 34°C, humidity = 50%). PATIENTS AND METHODS: Sixteen young male soccer players from the provincial competitive teams were divided into two equal groups and were randomly assigned to precooling (age = 16.5 ± 1.1 year, height = 171.7 ± 6.4 cm, BMI = 21.5 ± 3.3, VO2max = 50.6 ± 6.9 mL/kg/min) and non-precooling (age = 16.1 ± 1.1 year, height = 170.0 ± 4.7 cm, BMI = 21.3 ± 3.6, VO2max = 50.6 ± 6.8 mL/kg/min) groups. An exhaustive treadmill run test was conducted after warm-up (non-precooling) or warm-up + water immersion (temperature = 22 - 24°C). Oral temperature, plasma lactate and plasma volume were measured at the baseline (fasting state), mid test (immediately after warm up or warm -up + water immersion) and post test (immediately after exhaustive test). Mixed repeated measures analysis of variance and independent t test were used for data analyzing. P < 0.05 was considered significant. RESULTS: There were no significant differences between two groups at baseline, mid test and post test regarding oral temperature and plasma lactate. The time to exhaustion was considerably higher in the precooling group compared with the non-precooling group, but the difference was not statistically significant. No significant differences were found between the two groups on measures of the baseline and mid test plasma volume, but post test plasma volume was significantly higher in the precooling group compared to the non-precooling group (P < 0.05). CONCLUSIONS: These results show that precooling effectively attenuates dehydration, but has no positive effect on exhaustion time in the hot environment.

The influence of oral magnesium sulfate on skin microvasculature blood flow in diabetic rats.

Microvascular disease is a major feature of type1 diabetes and results from long-standing structural and functional changes especially in the skin microvasculature. Magnesium (Mg) deficiency has recently been proposed as a novel factor implicated in the pathogenesis of diabetes complications such as vascular disturbance, but its mechanism of action is not completely elucidated. The present study was designed to determine whether chronic magnesium sulfate administration could control streptozocin-induced diabetes and improve endothelium-dependent and endothelium-independent dilatation, and identify its probable mechanism in the skin microvasculature of diabetic rats. Fifty male Wistar rats (220 ± 10 g) were divided into two diabetic and one control groups. One subgroup of diabetic received magnesium sulfate (10 g/l) in their drinking water, while two other groups had only tap water. Laser Doppler flow meter with iontophoresis was used to measure the relative changes in skin blood flow. We used acetylcholine (Ach), sodium nitroprusside (SNP), and N (w)-nitro-L-arginine (LNNA; NO synthase inhibitor) with magnesium sulfate (0.1 M) in control and experimental animal by microsyringe pump microinjection. SNP- and Ach-induced cutaneous perfusion increased significantly by Mg treatment in the diabetic groups, and local microinjection of magnesium sulfate (0.1 M) increased cutaneous blood flow in all groups (p < 0.01). However, the administration of LNNA prior to magnesium sulfate attenuated (p < 0.05) but not abolished the increase in cutaneous blood flow in diabetic and normal rats. From the results of this study, it may be concluded that Mg could improve skin microvasculature of diabetic rats with potentiation of nitric oxide pathway.