Tribulus Terrestris may decrease muscle damage markers following a high-intensity resistance exercise: A pilot study.

The purpose of this study was to investigate the effect of two weeks of Tribulus Terrestris (TT) on the responses of Interleukin-6 (IL-6), high sensitivity C-reactive protein (hs-CRP), and enzymes creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) following a single session of resistance exercise (RE). Eighteen healthy non-athlete males (age: 22.44 ± 2.54 years, BMI: 26.15 ± 1.62 kg/m2) participated in this study and were divided randomly into two 9-person groups of supplementation or placebo. The participants consumed two 250-mg capsules of TT or placebo (maltodextrin) per day and performed six REs with the intensity 80, 85, and 90% of 1RM in three circles at the day after the end of supplementation period. Blood samples were collected before the initiation of supplementation, and before and after the RE session. Total changes of IL-6 (p<0.001) and LDH (p=0.005) were significant in both groups. Bonferroni post hoc test showed that increased values of IL-6 and CPK in both groups were significant after exercise compared with pre-exercise and baseline (p<0.001). There were no significant differences in relation to within- and between-group changes in hs-CRP (p>0.05). Moreover, differences between the groups regarding post-exercise IL-6 and CPK were not significant (p>0.05). However, post-exercise LDH in supplementation group were lower than placebo group (p=0.015). In conclusion, short-term supplementation with TT has no effect on IL-6 and hs-CRP, but may be effective on the reduction of muscle damage enzymes CPK and LDH following high-intensity circuit RE.

Identifying the Pressure Points of Acute Cadmium Stress Prior to Acclimation in Arabidopsis thaliana.

The toxic metal cadmium (Cd) is a major soil pollutant. Knowledge on the acute Cd-induced stress response is required to better understand the triggers and sequence of events that precede plant acclimation. Therefore, we aimed to identify the pressure points of Cd stress using a short-term exposure set-up ranging from 0 h to 24 h. Acute responses related to glutathione (GSH), hydrogen peroxide (H2O2), 1-aminocyclopropane-1-carboxylic acid (ACC), ethylene and the oxidative challenge were studied at metabolite and/or transcript level in roots and leaves of Arabidopsis thaliana either exposed or not to 5 µM Cd. Cadmium rapidly induced root GSH depletion, which might serve as an alert response and modulator of H2O2 signalling. Concomitantly, a stimulation of root ACC levels was observed. Leaf responses were delayed and did not involve GSH depletion. After 24 h, a defined oxidative challenge became apparent, which was most pronounced in the leaves and concerted with a strong induction of leaf ACC synthesis. We suggest that root GSH depletion is required for a proper alert response rather than being a merely adverse effect. Furthermore, we propose that roots serve as command centre via a.o. root-derived ACC/ethylene to engage the leaves in a proper stress response.

Satellite cell response to concurrent resistance exercise and high-intensity interval training in sedentary, overweight/obese, middle-aged individuals.

PURPOSE: Sarcopenia can begin from the 4-5th decade of life and is exacerbated by obesity and inactivity. A combination of resistance exercise (RE) and endurance exercise is recommended to combat rising obesity and inactivity levels. However, work continues to elucidate whether interference in adaptive outcomes occur when RE and endurance exercise are performed concurrently. This study examined whether a single bout of concurrent RE and high-intensity interval training (HIIT) alters the satellite cell response following exercise compared to RE alone. METHODS: Eight sedentary, overweight/obese, middle-aged individuals performed RE only (8 × 8 leg extensions at 70% 1RM), or RE + HIIT (10 × 1 min at 90% HRmax on a cycle ergometer). Muscle biopsies were collected from the vastus lateralis before and 96 h after the RE component to determine muscle fiber type-specific total (Pax7+ cells) and active (MyoD+ cells) satellite cell number using immunofluorescence microscopy. RESULTS: Type-I-specific Pax7+ (P = 0.001) cell number increased after both exercise trials. Type-I-specific MyoD+ (P = 0.001) cell number increased after RE only. However, an elevated baseline value in RE + HIIT compared to RE (P = 0.046) was observed, with no differences between exercise trials at 96 h (P = 0.21). Type-II-specific Pax7+ and MyoD+ cell number remained unchanged after both exercise trials (all P ≥ 0.13). CONCLUSION: Combining a HIIT session after a single bout of RE does not interfere with the increase in type-I-specific total, and possibly active, satellite cell number, compared to RE only. Concurrent RE + HIIT may offer a time-efficient way to maximise the physiological benefits from a single bout of exercise in sedentary, overweight/obese, middle-aged individuals.

Low-load resistance training with low relative pressure produces muscular changes similar to high-load resistance training.

INTRODUCTION: This study compares the acute and chronic response of high-load resistance training (HL) to low-load resistance training with low blood flow restriction (LL-BFR) pressure. METHODS: Participants completed elbow flexion with either HL or LL-BFR or nonexercise. In the chronic study, participants in the HL and LL-BFR groups were trained for 8 weeks to determine differences in muscle size and strength. The acute study examined the changes in pretesting/posttesting (Pre/Post) torque, muscle swelling, and blood lactate. RESULTS: In the chronic study, similar changes in muscle size and strength were observed for both HL and LL-BFR. In the acute study, Pre/Post changes in the torque, muscle swelling, and blood lactate were similar between HL and LL-BFR. DISCUSSION: Our findings indicate that pressure as low as 50% arterial occlusion can produce similar changes in muscle mass and strength compared with traditional HL. Muscle Nerve 56: E126-E133, 2017.

Acute psychophysiological responses during exercise while using resistive respiratory devices: A systematic review.

Different studies have observed that respiratory muscle training (RMT) improve the endurance and strength of the respiratory muscles, having a positive impact on performance of endurance sports. Nevertheless, it remains to be clarified how to improve the efficiency of such training. The objective of this systematic review was to evaluate the acute physiological responses produced by training the respiratory muscles during exercise with flow resistive devices because such information may support us improve the efficiency of this type of training. A search in the Medline, Science Direct, Web of Science and Scopus databases was conducted, following the PRISMA guidelines. The methodological quality of the articles was assessed using the PEDro scale. Nineteen studies met the inclusion criteria and a total of 212 subjects were included in the studies. The RMT method used in all studies was flow resistive loading, whereas the constant load exercise was the most common type of exercise among the studies. The results obtained seem to indicate that the use of this type of training during exercise reduces the performance, the lactate (La-) values and the ventilation, whereas the end - tidal partial pressure of carbon dioxide (PCO2) is increased.

Piglets' acute responses to local anesthetic injection and surgical castration: Effects of the injection method and interval between injection and castration.

Although applied in some countries, efficacy of local anesthetics based on procaine to mitigate acute responses to piglet castration remains questioned. This paper presents results from a factorial study examining the effects of two methods of injection of a procaine-based drug (intra-funicular, IF, vs. intra-testicular, IT), and four intervals between drug injection and castration (2.5, 5, 10, and 30 min) on acute responses of 3-4 day old piglets. The study involved 597 male piglets, and 13 treatments: surgical castration without anesthesia (CC), local anesthesia followed by castration involving all combinations of injection method and interval, and sham handling separated by the same four intervals (SH). Responses of piglets to drug injection, castration and sham handling were evaluated based on quantification of intra-procedural vocalizations and leg movements, as well as saliva cortisol concentration in samples taken before and after castration. No differences were found between IF and the simpler IT injection method. Intervals of 2.5 or 30 min led to stronger piglet responses than the other intervals. Overall, treatments involving anesthesia led to significantly stronger responses than sham handling, during both injection and castration. All treatments, even sham handling, led to a significant increase in saliva cortisol, with no differences between anesthesia treatments and controls. Based on these results, castration 5-10 min after intra-testicular injection of procaine seems to be preferable as compared to the other treatments tested. However, piglets still showed measurable signs of pain and stress during both injection and castration, while handling alone (including the use of a castration bench) triggered a noticeable stress response. In light of these findings, the overall benefit of the procedure in terms of piglet welfare remains arguable.

Piglets' acute responses to procaine-based local anesthetic injection and surgical castration: Effects of two volumes of anesthetic.

Surgical castration of piglets is painful, but practiced routinely in commercial pig production. Procaine-based local anesthetics are used to mitigate piglet pain during castration in some countries. Yet, effects of the volume of anesthetic injected remain under-studied. The volume of drug administered may modulate the pain mitigating effect via variation in intra-testicular pressure at injection, potentially leading to pain or discomfort, as well as variation in the dose of active ingredient administered. The present study investigated the effects of injection with two volumes of a procaine-based local anesthetic, 0.3 vs. 0.5 mL per testis, on acute responses of 3-4 day old piglets. A total of 290 piglets were divided into 5 treatment groups: castration without anesthesia, castration after intra-testicular injection of 0.5 or 0.3 mL of drug per testis, and sham handling with one or two stays in a castration bench. Acute responses to drug injection, castration and sham handling were evaluated based on quantification of intra-procedural vocalizations and foreleg movements, as well as saliva cortisol concentrations before and after castration. Regardless of the volume, injection of anesthetic as well as castration led to significantly stronger responses than sham handling. Responses to the two drug volumes did not differ significantly, and responses to castration following injection of 0.3 mL did not differ from piglets castrated without anesthesia. All treatments, including sham handling, led to a significant increase in saliva cortisol, and no difference was found between anesthesia treatments and sham handling. Overall, the results suggested that injection of 0.5 mL led to better pain mitigation at castration compared to injection of 0.3 mL, but even when the local anesthetic was used, the combined procedures of injection and castration led to intra-procedural signs of pain and stress.

Sodium Leak Channel in the Nucleus Accumbens Modulates Ethanol-Induced Acute Stimulant Responses and Locomotor Sensitization in Mice: A Brief Research Report.

Ethanol can induce acute stimulant responses in animals and human beings. Moreover, repeated exposure to ethanol may produce increased sensitivity to its acute locomotor stimulant actions, a process referred to as locomotor sensitization. The molecular mechanism of the development of acute stimulant responses and locomotor sensitization by ethanol is not fully understood. Sodium leak channel (NALCN) is widely expressed in central nervous system and controls the basal excitability of neurons. The present study aims to determine whether NALCN is implicated in the ethanol-induced acute responses and locomotor sensitization in mice. Here, our results showed that ethanol caused acute stimulant responses in DBA/2 mice. Locomotor sensitization was successfully induced following the sensitization procedure. Accordingly, the expression levels of NALCN mRNA and protein in the nucleus accumbens (NAc) were markedly increased in the sensitization mice compared to the control mice. Knockdown the expression levels of NALCN in the NAc alleviated both the ethanol-induced acute responses and locomotor sensitization. Our findings indicate that upregulation of NALCN expression in the NAc contributes to the ethanol-induced acute stimulant responses and locomotor sensitization in DBA/2 mice.

The importance of protein intake in master marathon runners.

OBJECTIVES: The aim of this study was to investigate the relationships between protein intake (during the tapering period and the race), marathon performance, body composition, acute race-induced changes, and selected metabolic- and muscle damage-related blood biomarkers in recreational master runners. METHODS: In 58 experienced master runners (58.28 y ± 1.07 y, 174.06 cm ± 0.72 cm, 78.51 kg ± 0.76 kg body mass, 21.38% ± 0.52% body fat, mean ± SEM), nutritional intake was evaluated 1 wk before the race and during the marathon. Body composition was evaluated before and 2 h after the race. Blood samples were collected at the same time points. RESULTS: Body fat and lean body mass (LBM) were significantly reduced after the marathon (P < 0.01; η2: 0.311-0.888). Significant negative correlations were observed between energy intake from carbohydrates and proteins (expressed per LBM), marathon performance, and race-induced changes of blood metabolic-muscle damage indices (P < 0.05; r: -0.522 to -0.789). Positive correlations were observed between energy from carbohydrates and proteins per LBM, and body mass and LBM changes (P < 0.05; r: 0.485-0.814). The specific contribution of protein intakes per LBM (beta coefficient: -0.789 to 0.615) on race-induced changes of body composition and blood markers was the same as that of carbohydrate intakes per LBM (beta coefficient: -0.777 to 0.559). CONCLUSIONS: Marathon-induced changes in body composition and metabolic blood indices are highly related to protein intake, either during the tapering period or during the race, with runners experiencing the lowest changes when consuming higher protein intakes.

The Perennial Use of the Green Fluorescent Protein Marker in a Live Vaccinia Virus Ankara Recombinant Platform Shows No Acute Adverse Effects in Mice.

Recombinant virus vectors represent a promising strategy for vaccine research. Among available viral vectors, members of the Poxviridae family-especially the modified Vaccinia virus Ankara (MVA)-stand out as immunogenic and safe vaccine platforms. Because MVA usually does not produce plaques in cell culture, visible selection markers such as the green fluorescent protein (GFP) are frequently incorporated into the constructions in order to facilitate the recognition of recombinants. However, these genetic markers have to be removed before any clinical trial. Here, we evaluated the acute responses generated in mice immunized with a MVA vector in which the GFP marker was not removed. We observed no differences in neutrophil, monocyte, or total leucocyte recruitment among animals inoculated with MVA or MVA-GFP. Likewise, there were no differences in neutrophil activation between mice groups. Hepatic functions were not altered in either MVA or MVA-GFP-inoculated mice, and we observed no histopathological alterations in different tissues from virus-inoculated animals. In conclusion, the presence of GFP is innocuous to immunized animals and do not alter acute physiopathological responses to the MVA vector. We suggest that keeping the GFP marker may be a good strategy for vaccine development, production, and evaluation.

Acute molecular responses to concurrent resistance and high-intensity interval exercise in untrained skeletal muscle.

Concurrent training involving resistance and endurance exercise may augment the benefits of single-mode training for the purpose of improving health. However, muscle adaptations, associated with resistance exercise, may be blunted by a subsequent bout of endurance exercise, via molecular interference. High-intensity interval training (HIIT), generating similar adaptations to endurance exercise, may offer an alternative exercise mode to traditional endurance exercise. This study examined the influence of an acute HIIT session on the molecular responses following resistance exercise in untrained skeletal muscle. Ten male participants performed resistance exercise (4 × 8 leg extensions, 70% 1RM, (RE)) or RE followed by HIIT (10 × 1 min at 90% HRmax, (RE+HIIT)). Muscle biopsies were collected from the vastus lateralis before, 2 and 6 h post-RE to determine intramuscular protein phosphorylation and mRNA responses. Phosphorylation of Akt (Ser(473)) decreased at 6 h in both trials (P < 0.05). Phosphorylation of mTOR (Ser(2448)) was higher in RE+HIIT (P < 0.05). All PGC-1α mRNA variants increased at 2 h in RE+HIIT with PGC-1α and PGC-1α-ex1b remaining elevated at 6 h, whereas RE-induced increases at 2 and 6 h for PGC-1α-ex1b only (P < 0.05). Myostatin expression decreased at 2 and 6 h in both trials (P < 0.05). MuRF-1 was elevated in RE+HIIT versus RE at 2 and 6 h (P < 0.05). Atrogin-1 was lower at 2 h, with FOXO3A downregulated at 6 h (P < 0.05). These data do not support the existence of an acute interference effect on protein signaling and mRNA expression, and suggest that HIIT may be an alternative to endurance exercise when performed after resistance exercise in the same training session to optimize adaptations.

Cardiac autonomic responses during and after a single session of aerobic exercise with and without blood flow restriction

Aim: To verify the on and off heart rate (HR) and HR variability (HRV) kinetics during a high-load aerobic exercise and a low-load aerobic exercise, with and without blood flow restriction (BFR). Methods: Fourteen healthy male subjects performed three randomly assigned experimental sessions: 1) 10 minutes walking at 40% of maximal aerobic speed (MAS) (40LL); 2) 10 minutes walking at 40% of MAS with BFR (40LL+BFR); and 3) 10 minutes running at 70% of MAS (70HL). The HR and HRV measurements were taken at rest, during exercise and the recovery period after constant load sessions. Results: The HR on- and off- kinetics, and HRV on-kinetics were faster in 40LL than in 40LL +BFR and 70HL (p < 0.05). The time constant (τon) of HR on-kinetics was faster in 40LL+BFR than in 70HL (23.4 ± 9.5 s vs 42 ± 9.5 s, respectively, p < 0.01), and was accompanied by faster HRV on-kinetics (12.4 ± 9.6 s vs 20.3 ± 13.7 s, respectively, p < 0.01). Although HR off-kinetics was not different between 40LL+BFR and 70HL, the recovery of time and frequency HRV indices were delayed in 70HL when compared to 40LL and 40LL+BFR (p < 0.05). Conclusions: These findings indicate that 40LL promoted faster cardiac adjustments compared to 40LL+BFR and 70HL sessions. Additionally, 40LL+BFR promoted faster cardiac adjustment and better HRV recovery compared to the 70HL session. (AU)

Efeito hipotensor de uma sessão de exercícios aquáticos: variabilidade e reprodutibilidade / Antihypertensive effect of an aqua activity session: variability and reproducibility

Exercícios físicos são indicados como parte do tratamento de hipertensos devido à possibilidade de redução da pressão arterial sistólica (PAS) e diastólica (PAD), sendo sugerido que essa redução ocorra imediatamente após a realização do exercício, podendo permanecer por várias horas. Este estudo objetivou verificar a duração do efeito hipotensor de uma sessão de hidroginástica em mulheres hipertensas moderadas, bem como a reprodutibilidade e variabilidade desses efeitos. A amostra foi composta por 13 mulheres hipertensas (idades: 40 a 65 anos; x =53,2±7,5). Foram mensuradas a PA em repouso (PAS1, PAD1), 15 minutos (PAS2, PAD2), 24h (PAS3, PAD3) e 48h (PAS4, PAD4) pós-exercício (S1). No dia posterior à última medida foi realizada uma segunda sessão de exercícios (S2) com aferição da PA 24h depois (PAS5, PAD5). A ANOVA para medidas repetidas + post-hoc Tukey exibiu diferenças significativas entre PAS2 e 3 e PAD2 e 3, em relação a PAS1 e PAD1 (p < 0,05). O coeficiente de correlação intraclasse verificado entre PAS4 e PAS5 foi de 0,99 e, entre PAD4 e PAD5, de 0,97; e o coeficiente devariabilidade foi de 6% entre PAS4 e PAS5 e 5% entre PAD4 E PAD5. Esses valores demonstram uma excelente reprodutibilidade e uma pequena variabilidade do comportamento pressórico 24h pós-exercício. Nossos resultados indicam que uma sessão de exercícios pode reduzir de forma significativa (p<0,05) a PAS e a PAD e que seus efeitos são consistentemente sustentados por 24h, sugerindo a necessidade do exercício diário para obtenção dos benefícios do exercício como terapia não farmacológica para o adequado controle da PA.

Physical exercises are indicated as a part of hypertensive’s treatment due to the possibility of a systolic (SBP) and diastolic blood pressure (DBP) reduction, being suggested that such reduction occurs immediately after the exercise, with a possibility to be prolonged for several hours. The aim of this study was to verify the duration of the antihypertensive effect of an aqua activity session in moderately hypertensive women, as well as the reproducibility and variability of this effect. The sample was comprised by 13 hypertensive women (ages: 40 to 65 years; x =53.2±7.5). The BP at rest (SBP1, DBP1), 15-min (SBP2, DBP2), 24h (SBP3, DBP3) and 48h (SBP4, DBP4) after the exercise (S1) were measured. On the day before the last measurement, a second session of exercises (S2) with BP measurement 24h later (SBP5, DBP5) was performed. The repeated measures ANOVA + post-hoc Tukey demonstrated significant changes between SBP2 and 3 and DBP2 and 3, in relation to SBP1 and DBP1 (p< 0.05). The interclass correlation coefficient verified between SBP4 and SBP5 was 0.99 and, between DBP4 and DBP5, 0.97. The variability coefficient was 6% between SBP4 e SBP5 and 5% between DBP4 and DBP5. Such values demonstrate and excellent reproducibility and a small variability of the BP 24h after the exercise. Our results indicate that a session of exercises can reduce significantly (p<0.05) the SBP and DBP and that its effects are consistently maintained for 24h, suggesting the necessity of a daily exercise to obtain the benefits of the exercise as a non pharmacological therapy for an adequate BP control.

Respostas hormonais agudas a diferentes intensidades de exercícios resistidos em mulheres idosas / Acute hormonal responses to different intensities of resistance exercises in older women

O treinamento resistido vem sendo apontado como eficaz em retardar o declínio de força e massa muscular que acompanham o envelhecimento; contudo, a resposta hormonal aguda a esse tipo de exercício precisa ser mais bem caracterizada. Os objetivos do presente estudo foram caracterizar e comparar as respostas hormonais agudas resultantes de diferentes intensidades de exercícios resistidos realizados por mulheres idosas. A amostra foi composta por 15 mulheres com idade média de 67,5 anos, as quais realizaram, de forma aleatória, três visitas ao laboratório: 1) exercícios resistidos realizados a 50 por cento de 1-RM (G50); 2) exercícios resistidos realizados a 80 por cento de 1-RM (G80); e 3) sessão controle (GC). Coletas sanguíneas foram realizadas imediatamente antes e após (TO e T1, respectivamente) cada sessão, bem como três e 48 horas após (T2 eT3, respectivamente), para posterior análise hormonal através do método imunoensaio quimiluminescente. ANOVA e ANCOVA foram utilizadas, respectivamente, para examinar diferenças intra e intersessões. Não foram observadas diferenças significativas entre as sessões para nenhum dos hormônios avaliados. EmT2, as concentrações do cortisol encontraram-se significativamente inferiores quando comparados com T0 nas três sessões realizadas, enquanto a testosterona apresentou-se reduzida no T2 do GC. Apenas a sessão G80 induziu elevação transitória significativa da razão testosterona/cortisol e nenhuma das sessões provocou alterações nas concentrações séricas de GH. Conclui-se que exercícios resistidos realizados a 50 por cento ou a 80 por cento de 1-RM não induziram agudamente elevação significativa de cortisol, testosterona ou GH na amostra estudada. Por outro lado, a sessão realizada a 80 por cento de 1-RM promoveu aumento significativo da razão testosterona/cortisol três horas pós-exercício quando comparada com a dos valores basais, em mulheres idosas.

Resistance training has been pointed as an effective intervention to minimize muscle mass and strength decline observed with advancing age, however, its acute hormonal responses need to be better characterized. The purposes of the present study were characterize and compare the acute hormonal responses to different resistance exercises intensities performed by older women. Sample was composed by 15 women with a mean age of 67,5 years, who performed, in a randomized order, three visits at the laboratory: 1) resistance exercises performed at 50 percent of 1-RM (G50); 2) resistance exercises performed at 80 percent of 1-RM (G80) and 3) control session (GC). Blood samples were taken immediately before and after (T0 and T1, respectively) each session, as well as three and 48 hour after (T2 and T3, respectively), for subsequent hormonal analyses by the enzyme immunoassay chemiluminescent method. ANOVA and ANCOVA were used, respectively, to examine intra and inter sessions differences. No significant differences were observed between sessions for any of the evaluated hormone. In T2, cortisol concentrations were significantly reduced when compared to T0 for the three examined sessions, while testosterone was reduced after (T2) GC. Only G80 elicited a significant transient elevation in testosterone/cortisol ratio and none of the sessions provoked alterations on serum GH concentrations. It's concluded that resistance exercises performed at 50 percent or 80 percent of 1-RM do not acutely induce significant elevation of cortisol, testosterone or GH in the studied population. On the other hand, the session performed at 80 percent of 1-RM promoted significant elevations on the testosterone/cortisol ratio three hours post exercises when compared to basal values, in older women.

Conceitos fisiológicos do treinamento físico-esportivo: estresse, homeostase e alostase / Physiological concepts in physical education and sports training: stress, homeostasis and allostasis

O objetivo desta revisão é discutir criticamente os conceitos de estresse e homeostase (homeos = igual; stasis = constância) e expor suas limitações em função de recentes evidências que demonstram que a suposta estabilidade interna dos organismos vivos é apenas aparente, inclusive sendo independente de fatores ambientais. Essa instabilidade interna é freqüentemente constatada por pesquisadores dos ritmos circadianos (secreções hormonais), séries temporais (freqüência cardíaca) e comportamento (fome e saciedade), que argumentam a favor da substituição da teoria da homeostase pela noção de alostase (allo = diferente; stasis = constância). Na verdade, o propósito da regulação e controle segundo os mesmos não é a constância. Duas conseqüências para a Educação Física e Esporte com a aceitação da alostase como paradigma fisiológico são: 1. O conceito de estresse de Selye deve sofrer nova definição e interpretação, interferindo claramente nanoção de carga ou sobrecarga de trabalho e, 2. A hipótese do governo central de Noakes na explicação da fadiga decorrente do exercício físico intenso perde o sentido, como será discutido neste trabalho. Além disso, é muito difícil explicar através da estabilidade pela constância como o desempenho é alterado pelo treinamento físico e porque temos predisposição para esse tipo de atividade reconhecidamente anti-homeostática. Pretendemos neste trabalho mostrar, portanto, a possibilidade de que com a noção de estabilidade pela mudança da alostase essas contradições perdem o sentido...

The objective of this review article is to discuss the concepts of stress and homeostasis (homeos = equal; stasis= stable) and to expose their limitations on the basis of recent evidence demonstrating that the supposed internal stability of living organisms is merely apparent, and is even independent of environmental factors. This internal instability is oftenobserved by researchers investigating circadian rhythms (hormone secretion), temporal series (heart rate) and behavior (hunger and satiety), who argue in favor of substituting the theory of homeostasis by the concept of allostasis (allo =different; stasis = stable). Indeed, these researchers suggest that the objective of regulation and control is not stability. Thereare two consequences for Physical Education and Sport if allostasis is accepted as a physiological paradigm: 1. Selyeãs concept of stress requires a new defi nition and interpretation, with a clear impact on the concept of load and overload; 2. Noakesã central governor hypothesis to explain the fatigue resulting from intense physical exercise loses its relevance, as will be discussed in this paper. Furthermore, it is very diffi cult for the model of stability by staying the same to explain why performance is improved by physical training or why we have a predisposition for this type of recognizedly anti-homeostaticactivity. We intend to demonstrate the possibility that the allostatic concept of stability through change can explain these contradictions...