Isokinetic eccentric resistance training prevents loss in mechanical muscle function after running

The aim of the study was to verify whether 8 weeks of resistance training employing maximal isokinetic eccentric (IERT) knee extensor actions would reduce the acute force loss observed after high-intensity treadmill running exercise. It was hypothesized that specific IERT would induce protective effects against muscle fatigue and ultrastructural damages, preventing or reducing the loss in mechanical muscle function after running. Subjects were tested before and after IERT protocol for maximal isometric, concentric and eccentric isokinetic knee extensor strength (60 and 180 s-1). In a second session, subjects performed treadmill running (~35 min) and the previously mentioned measurements were repeated immediately after running. Subsequently, subjects were randomized to training (n = 12) consisting of 24 sessions of maximal IERT knee extensors actions at 180 s-1, or served as controls (n = 8). The effects of acute running-induced fatigue and training on isokinetic and isometric peak torque, and rate of force development (RFD) were investigated. Before IERT, running-induced eccentric torque loss at 180 s-1 was -8 %, and RFD loss was -11 %. Longitudinal IERT led to reduced or absent acute running-induced losses in maximal IERT torque at 180 s-1 (+2 %), being significantly reduced compared to before IERT (p < 0.05), however, RFD loss remained at -11 % (p > 0.05). In conclusion, IERT yields a reduced strength loss after high-intensity running workouts, which may suggest a protective effect against fatigue and/or morphological damages. However, IERT may not avoid reductions in explosive muscle actions. In turn, this may allow more intense training sessions to be performed, facilitating the adaptive response to running training. © 2013 Springer-Verlag Berlin Heidelberg.

Monitoring muscle damage markers during a four-week downhill walking exercise program

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Strength gain through eccentric isotonic training without changes in clinical signs or blood markers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cardiac autonomic responses induced by a single bout of exercise with flexible pole

Background: Flexible poles are tools used to provide rapid eccentric and concentric muscle contractions. It lacks in the literature studies that analyze acute cardiovascular responses in different exercises performed with this instrument. It was investigated the acute effects of exercise with flexible poles on heart period in healthy women. Methods: The study was performed on 32 women between 18 and 25 years old. It was evaluated the heart rate variability (HRV) in the time (SDNN, RMSSD and pNN50) and frequency domain (HF, LF and LF/HF ratio). The subjects remained at rest for 10 minutes. After the rest period, the volunteers performed the exercises with the flexible poles. Immediately after the exercise protocol, the volunteers remained seated at rest for 60 minutes and HRV were analyzed. Results: It was observed no significance changes in the time domain (SDNN: p = 0.14; RMSSD: p = 0.8 and pNN50: p = 0.86) and frequency domain indices (LF (nu): 0.4; LF (ms2): p = 0.34; HF (nu): p = 0.4; HF (ms2): p = 0.8 and LF/HF ratio: p = 0.3) between before and after single bout of exercise with flexible pole. Conclusion: A single bout of exercise with flexible pole did not significantly change cardiac autonomic regulation in healthy women.

A single bout of exercise with a flexible pole induces significant cardiac autonomic responses in healthy men

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Acute effects of flexible pole exercise on heart rate dynamics

Introduction: Exercise with flexible poles provides fast eccentric and concentric muscle contractions. Although the literature reports significant muscle chain activity during this exercise, it is not clear if a single bout of exercise induces cardiac changes. In this study we assessed the acute effects of flexible pole exercise on cardiac autonomic regulation.Methods: The study was performed on 22 women between 18 and 26 years old. We assessed heart rate variability (HRV) in the time (SDNN, RMSSD and pNN50) and frequency (HF, LF and LF/HF ratio) domains and geometric indices of HRV (RRTri, TINN, SD1, SD2 and SD1/SD2 ratio). The subjects remained at rest for 10 min and then performed the exercises with the flexible poles. Immediately after the exercise protocol, the volunteers remained seated at rest for 60 min and HRV was analyzed.Results: We observed no significant changes in time domain (SDNN: p=0.72; RMSSD: p=0.94 and pNN50: p=0.92) or frequency domain indices (LF [nu]: p=0.98; LF [ms(2)]: p=0.72; HF [nu]: p=0.98; HF [ms(2)]: p=0.82 and LF/HF ratio: p=0.7) or in geometric indices (RRTri: p=0.54; TINN: p=0.77; SD1 p=0.94; SD2: p=0.67 and SD/SD2: p=0.42) before and after a single bout of flexible pole exercise.Conclusion: A single bout of flexible pole exercise did not induce significant changes in cardiac autonomic regulation in healthy women. (C) 2014 Sociedade Portuguesa de Cardiologia. Published by Elsevier Espana, S.L.U. All rights reserved.

Eccentric torque-producing capacity is influenced by muscle length in older healthy adults

Considering the importance of muscle strength to functional capacity in the elderly, the study investigated the effects of age on isokinetic performance and torque production as a function of muscle length. Eleven younger (24.2±2.9years) and seventeen older men (62.7±2.5years) were subjected to concentric and eccentric isokinetic knee extension/flexion at 60°.s-1 and 120°.s-1 through a functional range of motion. The older group presented lower peak torque (Nm) than the young group for both isokinetic contraction types (age effect, p<0.001). Peak torque deficits in the older group were near 30% and 29% for concentric and eccentric contraction, respectively. Concentric peak torque was lower at 120.s-1 than at 60.s-1 for both groups (angular velocity effect, p<0.001). Eccentric knee extension torque was the only exercise tested that showed an interaction effect between age and muscle length (p<0.001), which suggested different torque responses to the muscle length between groups. Compared with the young group, the eccentric knee extension torque was 22% to 56% lower in the older group, with the deficits being lower in the shortened muscle length (22-27%) and higher (33-56%) in stretched muscle length. In older men, the production of eccentric knee strength seems to be muscle length-dependent. At more stretched positions, older subjects lose the capacity to generate eccentric knee extension torque. More studies are needed to assess the mechanisms involved in eccentric strength preservation with aging and its relationship with muscle length.

Effects of circuit-based exercise programs on the body composition of elderly obese women

Aim: The aim of this study was to investigate the impact of circuit-based exercise on the body composition in obese older women by focusing on physical exercise and body weight (BW) gain control in older people. Methods: Seventy older women (>60 years old) voluntarily took part in the study. Participants were randomized into six different groups according to body mass index (BMI): appropriate weight (AW) control (AWC) and trained (AWT) groups, overweight (OW) control (OWC) and trained (OWT) groups, and obesity (O) control (OC) and trained (OT) groups. The exercise program consisted of 50 minutes of exercise three times per week for 12 weeks. The exercises were alternated between upper and lower body using rest between sets for 40 seconds with intensity controlled by heart rate (70% of work). The contraction time established was 5 seconds to eccentric and concentric muscular action phase. The following anthropometric parameters were evaluated: height (m), body weight (BW, kg), body fat (BF, %), fat mass (FM, kg), lean mass (LM, kg), and BMI (kg/m(2)). Results: The values (mean +/- standard deviation [SD]) of relative changes to BW (-8.0% +/- 0.8%), BF (-21.4% +/- 2.1%), LM (3.0% +/- 0.3%), and FM (-31.2% +/- 3.0%) to the OT group were higher (P < .05) than in the AWT (BW: -2.0% +/- 1.1%; BF: -4.6% +/- 1.8%; FM: -7.0% +/- 2.8%; LM: 0.2% +/- 1.1%) and OWT (BW: -4.5% +/- 1.0%; BF: -11.0% +/- 2.2%; FM: -16.1% +/- 3.2%; LM: -0.2% +/- 1.0%) groups; additionally, no differences were found for C groups. While reduction (P < .03) in BMI according to absolute values was observed for all trained groups (AWT: 22 +/- 1 versus 21 +/- 1; OWT: 27 +/- 1 versus 25 +/- 1, OT: 34 +/- 1 versus 30 +/- 1) after training, no differences were found for C groups. Conclusion: In summary, circuit-based exercise is an effective method for promoting reduction in anthropometrics parameters in obese older women.

Different molecular and structural adaptations with eccentric and conventional strength training in elderly men and women

Reprogramming of gene expression contributes to structural and functional adaptation of muscle tissue in response to altered use. The aim of this study was to investigate mechanisms for observed improvements in leg extension strength, gain in relative thigh muscle mass and loss of body and thigh fat content in response to eccentric and conventional strength training in elderly men (n = 14) and women (n = 14; average age of the men and women: 80.1 ± 3.7 years) by means of structural and molecular analyses. Biopsies were collected from m. vastus lateralis in the resting state before and after 12 weeks of training with two weekly resistance exercise sessions (RET) or eccentric ergometer sessions (EET). Gene expression was analyzed using custom-designed low-density PCR arrays. Muscle ultrastructure was evaluated using EM morphometry. Gain in thigh muscle mass was paralleled by an increase in muscle fiber cross-sectional area (hypertrophy) with RET but not with EET, where muscle growth is likely occurring by the addition of sarcomeres in series or by hyperplasia. The expression of transcripts encoding factors involved in muscle growth, repair and remodeling (e.g., IGF-1, HGF, MYOG, MYH3) was increased to a larger extent after EET than RET. MicroRNA 1 expression was decreased independent of the training modality, and was paralleled by an increased expression of IGF-1 representing a potential target. IGF-1 is a potent promoter of muscle growth, and its regulation by microRNA 1 may have contributed to the gain of muscle mass observed in our subjects. EET depressed genes encoding mitochondrial and metabolic transcripts. The changes of several metabolic and mitochondrial transcripts correlated significantly with changes in mitochondrial volume density. Intramyocellular lipid content was decreased after EET concomitantly with total body fat. Changes in intramyocellular lipid content correlated with changes in body fat content with both RET and EET. In the elderly, RET and EET lead to distinct molecular and structural adaptations which might contribute to the observed small quantitative differences in functional tests and body composition parameters. EET seems to be particularly convenient for the elderly with regard to improvements in body composition and strength but at the expense of reducing muscular oxidative capacity.

Gene expression in skeletal muscle of coronary artery disease patients after concentric and eccentric endurance training

Low-intensity concentric (CET) and eccentric (EET) endurance-type training induce specific structural adaptations in skeletal muscle. We evaluated to which extent steady-state adaptations in transcript levels are involved in the compensatory alterations of muscle mitochondria and myofibrils with CET versus EET at a matched metabolic exercise intensity of medicated, stable coronary patients (CAD). Biopsies were obtained from vastus lateralis muscle before and after 8 weeks of CET (n=6) or EET (n=6). Transcript levels for factors involved in mitochondrial biogenesis (PGC-1alpha, Tfam), mitochondrial function (COX-1, COX-4), control of contractile phenotype (MyHC I, IIa, IIx) as well as mechanical stress marker (IGF-I) were quantified using an reverse-transcriptase polymerase chain reaction approach. After 8 weeks of EET, a reduction of the COX-4 mRNA level by 41% and a tendency for a drop in Tfam transcript concentration (-33%, P=0.06) was noted. This down-regulation corresponded to a drop in total mitochondrial volume density. MyHC-IIa transcript levels were specifically decreased after EET, and MyHC-I mRNA showed a trend towards a reduction (P=0.08). Total fiber cross-sectional area was not altered. After CET and EET, the IGF-I mRNA level was significantly increased. The PGC-1alpha significantly correlated with Tfam, and both PGC-1alpha and Tfam significantly correlated with COX-1 and COX-4 mRNAs. Post-hoc analysis identified significant interactions between the concurrent medication and muscular transcript levels as well as fiber size. Our findings support the concept that specific transcriptional adaptations mediate the divergent mitochondrial response of muscle cells to endurance training under different load condition and indicate a mismatch of processes related to muscle hypertrophy in medicated CAD patients.

Mechanisms of protein regulation in rat skeletal muscle during resistance exercise and training

The cellular mechanisms through which adult rat skeletal muscle protein is regulated during resistance exercise and training was investigated. A model of non-voluntary resistance exercise was described which involves the electrically-stimulated contraction of the lower leg muscles of anesthetized rats against a weighted pulley-bar. Muscle protein synthesis rates were measured by in vivo constant infusion of $\sp3$H-leucine following a single bout of resistance exercise. Specific messenger RNA levels were determined by dot-blot hybridization analysis using $\sp{32}$P-labelled DNA probes after a single bout and multiple bouts of phasic training. The effects of phasic training on increasing skeletal muscle mass was assessed. Between 12 and 36 hours following a single resistance exercise bout (24-192 contractions), total mixed and myofibril protein synthesis rates were significantly increase (32%-65%) after concentric (gastrocnemius m.) and eccentric (tibialis anterior m.) contractions. Eccentric contractions had greater effects on myofibril synthesis with more prolonged increases in synthesis rates. Lower numbers of eccentric than concentric contractions were required to increase synthesis. Cellular RNA was increased after exercise but the relative levels of skeletal $\alpha$-actin and cytochrome c mRNAs were unchanged. Since increases in synthesis rates exceeded increases in RNA, post-transcriptional mechanisms may be primarily responsible for increased protein synthesis after a resistance exercise bout. After 10-22 weeks of phasic eccentric resistance training, muscle enlargement (16%-30%) was produced in the tibialis anterior m. after all training paradigms examined. In contrast, gastrocnemius m. enlargement after phasic concentric training occurred after moderate (24/bout) but not after high (192/bout) repetition training. The absence of muscle growth in the gastrocnemius m. after high repetition training despite increased synthesis rates after the initial bout and RNA and possibly mRNA accumulation during training suggests a role for post-translational mechanisms (protein degradation) in the control of muscle growth in the gastrocnemius m. It is concluded that muscle protein during resistance exercise and training is regulated at several cellular levels. The particular response may be influenced by the exercise intensity and duration, the training frequency and the type of contractile work (eccentric vs. concentric) performed. ^

Effect Of Exercise Test On Pulmonary Function Of Obese Adolescents.

to investigate the pulmonary response to exercise of non-morbidly obese adolescents, considering the gender. a prospective cross-sectional study was conducted with 92 adolescents (47 obese and 45 eutrophic), divided in four groups according to obesity and gender. Anthropometric parameters, pulmonary function (spirometry and oxygen saturation [SatO2]), heart rate (HR), blood pressure (BP), respiratory rate (RR), and respiratory muscle strength were measured. Pulmonary function parameters were measured before, during, and after the exercise test. BP and HR were higher in obese individuals during the exercise test (p = 0.0001). SatO2 values decreased during exercise in obese adolescents (p = 0.0001). Obese males had higher levels of maximum inspiratory and expiratory pressures (p = 0.0002) when compared to obese and eutrophic females. Obese males showed lower values of maximum voluntary ventilation, forced vital capacity, and forced expiratory volume in the first second when compared to eutrophic males, before and after exercise (p = 0.0005). Obese females had greater inspiratory capacity compared to eutrophic females (p = 0.0001). Expiratory reserve volume was lower in obese subjects when compared to controls (p ≤ 0,05). obese adolescents presented changes in pulmonary function at rest and these changes remained present during exercise. The spirometric and cardiorespiratory values were different in the four study groups. The present data demonstrated that, in spite of differences in lung growth, the model of fat distribution alters pulmonary function differently in obese female and male adolescents.

[recommendations For Physical Exercise Practice During Pregnancy: A Critical Review].

Physical exercise is recommended for all healthy pregnant women. Regular practice of exercises during pregnancy can provide many physical and psychological benefits, with no evidence of adverse outcomes for the fetus or the newborn when exercise is performed at mild to moderate intensity. However, few pregnant women engage in this practice and many still have fears and doubts about the safety of exercise. The objective of the present study was to inform the professionals who provide care for Brazilian pregnant women about the current recommendations regarding physical exercise during pregnancy based on the best scientific evidence available. In view of the perception that few systematic models are available about this topic and after performing several studies in this specific area, we assembled practical information of interest to both the professionals and the pregnant women. We also provide recommendations about the indications, contraindications, modalities (aerobics, resistance training, stretching and pelvic floor training), frequency, intensity and duration indicated for each gestational trimester. The review addresses physical exercise recommendation both for low risk pregnant women and for special populations, such as athletes and obese, hypertensive and diabetic subjects. The advantages of an active and healthy lifestyle should be always reinforced during and after gestation since pregnancy is an appropriate period to introduce new habits because pregnant women are usually more motivated to adhere to recommendations. Thus, routine exams, frequent returns and supervision are recommended in order to provide new guidelines that will have long-term beneficial effects for both mother and child.

Acute Exercise Decreases Trb3 Protein Levels In The Hypothalamus Of Obese Rats.

To evaluate the effects of acute exercise on the TRB3 protein levels and interaction between TRB3/Akt proteins in the hypothalamus of obese rats. In addition, we evaluated the relationship between TRB3 and endoplasmic reticulum stress (ER stress) and verified whether an acute exercise session is able to influence these processes. In the first part of the study, the rats were divided into three groups: control (lean) - fed with a standard rodent chow, DIO - fed with a high fat diet and DIO submitted to a swimming acute exercise protocol (DIO-EXE). In the second part of the study, we used other three groups: control (lean) receiving an intracerebroventricular (i.c.v.) infusion of vehicle, lean receiving an i.c.v. infusion of thapsigargin, and lean receiving an i.c.v infusion of thapsigargin and performing an acute exercise session. Four hours after the exercise session, the food intake was measured and the hypothalamus was dissected and separated for subsequent protein analysis by immunoblotting and Real Time PCR. The acute exercise session reduced the TRB3 protein levels, disrupted the interaction between TRB3/Akt proteins, increased the phosphorylation of Foxo1 and restored the anorexigenic effects of insulin in the hypothalamus of DIO rats. Interestingly, the suppressive effects of acute exercise on TRB3 protein levels may be related, at least in part, to the decrease of ER stress (evaluated though pancreatic ER kinase phosphorylation - pPERK and C/EBP homologous protein - CHOP protein levels) in the hypothalamus. In conclusion, the reduction of hypothalamic TRB3 protein levels mediated by exercise may be associated with the reduction of ER stress. These data provided a new mechanism by which an acute exercise session improves insulin sensitivity in hypothalamus and restores food intake control in obesity.

[physical Exercise During Pregnancy].

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