Combined Training Improves Gene Expression Related to Immunosenescence in Obese Type 2 Diabetic Individuals.

Purpose: The aim of this study was to investigate the effects of moderate combined training (CT) on both the gene expression of pro- and anti-inflammatory markers and senescence in the immune system in peripheral blood mononuclear cells (PBMCs) and subcutaneous adipose tissue (SAT) of obese middle-aged individuals with type 2 diabetes (T2D). Methods: Thirty obese individuals (50.2 ± 9.4 years; body mass index: 31.8 ± 2.3 kg/m²) with T2D underwent 16 weeks of a CT group [CT; aerobic (50-60% of VO2max) plus resistance (50-75% of 1RM) training; 3 times/week, 70 min/session; n = 16)] or a control group (CG, n = 14). Nutritional patterns, muscle strength (1RM), cardiorespiratory fitness (VO2max), waist circumference (WC), body composition (Air Displacement Plethysmograph) and blood collections for biochemical (serum leptin, IL-2, IL-4, IL-6, IL-10, TNF-α and anti-CMV) and molecular (gene expression of leptin, IL-2, IL-4, IL-6, IL-10, TNF-α, PD-1, P16ink4a, CCR7, CD28 and CD27 in PBMCs and SAT) analyses were assessed before (Pre) and after (Post) the 16 weeks of the experimental period. Results: Significant decreases were observed in WC and IL4, TNF-α, PD-1 and CD27 expression in PBMCs for CT. Furthermore, significant increases were observed in 1RM and VO2max for CT after the experimental period. Conclusion: Moderate CT contributed to a reduction in the gene expression of markers associated to chronic inflammation and immunosenescence in PBMCs of obese middle-aged individuals with T2D.

Serum metabolites associated with increased insulin resistance and low cardiorespiratory fitness in overweight adolescents.

BACKGROUND AND AIMS: Obesity affects metabolism, increasing the risk of developing non-communicable diseases in adolescence, due to excess adipose tissue and low cardiorespiratory fitness (CRF). The metabolomics approach allows the elucidation of metabolites, which may have the concentrations altered by several factors, such as body composition (BC). We aimed to analyze the metabolomic profile of normal-weight and overweight adolescents and associate the metabolites with clinical markers related to BC, insulin resistance (IR), and CRF. METHODS AND RESULTS: The sample was composed of 57 adolescents and divided into two groups: the normal-weight group (NWG, n = 24) and the overweight group (OWG, n = 33). They underwent blood collection and anthropometric, BC, and CRF assessment. Blood serum samples were analyzed by 1H-NMR spectroscopy (600 MHz). The OWG presented higher values of body weight (BW), body mass index (BMI), waist circumference (WC), fasting glucose, insulin, IR, cholesterol, and percentage of fat mass (%FM) and lower levels of peak oxygen consumption (VO2 peak) compared with the NWG. The OWG presented lower concentrations of 3-hydroxyisovalerate, glutamate, and methionine as well as higher concentrations of aspartate, asparagine, creatine, glycerol, myo-inositol, proline, pyruvate, tyrosine, and valerate compared with the NWG. The concentrations of glutamate, myo-inositol, creatine, methionine, and valerate correlated with %FM; pyruvate and valerate positively correlated with IR; and glutamate, tyrosine, and valerate negatively correlated with CRF. CONCLUSION: Changes in the BC lead to changes in the metabolomic profile of adolescents, and the altered metabolites are associated with increased IR and low CRF. These results indicate new targets for health monitoring and prevention of cardiovascular and metabolic diseases in adolescents.

Understanding the Relationship between Intrinsic Cardiorespiratory Fitness and Serum and Skeletal Muscle Metabolomics Profile.

Intrinsic cardiorespiratory fitness (iCRF) indicates the CRF level in the sedentary state. However, even among sedentary individuals, a wide interindividual variability is observed in the iCRF levels, whose associated molecular characteristics are little understood. This study aimed to investigate whether serum and skeletal muscle metabolomics profiles are associated with iCRF, measured by maximal power output (MPO). Seventy sedentary young adults were submitted to venous blood sampling, a biopsy of the vastus lateralis muscle and iCRF assessment. Blood serum and muscle tissue samples were analyzed by proton nuclear magnetic resonance (1H NMR) spectroscopy. Metabolites related to iCRF were those supported by three levels of evidence: (1) correlation with iCRF, (2) significant difference between individuals with low and high iCRF, and (3) metabolite contribution to significant pathways associated with iCRF. From 43 serum and 70 skeletal muscle analyzed metabolites, iCRF was positively associated with levels of betaine, threonine, proline, ornithine, and glutamine in serum and lactate, fumarate, NADP+, and formate in skeletal muscle. Serum betaine and ornithine and skeletal muscle lactate metabolites explained 31.2 and 16.8%, respectively, of the iCRF variability in addition to body mass. The results suggest that iCRF in young adults is positively associated with serum and skeletal muscle metabolic levels, indicative of the amino acid and carbohydrate metabolism.

Obesity Increases Gene Expression of Markers Associated With Immunosenescence in Obese Middle-Aged Individuals.

Recently, it has been argued that obesity leads to a chronic pro-inflammatory state that can accelerate immunosenescence, predisposing to the early acquisition of an immune risk profile and health problems related to immunity in adulthood. In this sense, the present study aimed to verify, in circulating leukocytes, the gene expression of markers related to early immunosenescence associated with obesity and its possible relationships with the physical fitness in obese adults with type 2 diabetes or without associated comorbidities. The sample consisted of middle-aged obese individuals (body mass index (BMI) between 30-35 kg/m²) with type 2 diabetes mellitus (OBD; n = 17) or without associated comorbidity (OB; n = 18), and a control group of eutrophic healthy individuals (BMI: 20 - 25 kg/m²) of same ages (E; n = 18). All groups (OBD, OB and E) performed the functional analyses [muscle strength (1RM) and cardiorespiratory fitness (VO2max)], anthropometry, body composition (Air Displacement Plethysmograph), blood collections for biochemical (anti-CMV) and molecular (gene expression of leptin, IL-2, IL-4, IL-6, IL-10, TNF-α, PD-1, P16ink4a, CCR7, CD28 and CD27) analyses of markers related to immunosenescence. Increased gene expression of leptin, IL-2, IL-4, IL-10, TNF-α, PD-1, P16ink4a, CCR7 and CD27 was found for the OBD and OB groups compared to the E group. Moreover, VO2max for the OBD and OB groups was significantly lower compared to E. In conclusion, obesity, regardless of associated disease, induces increased gene expression of markers associated with inflammation and immunosenescence in circulating leukocytes in obese middle-aged individuals compared to a eutrophic group of the same age. Additionally, increased adipose tissue and markers of chronic inflammation and immunosenescence were associated to impairments in the cardiorespiratory capacity of obese middle-aged individuals.

Altered metabolomic profiling of overweight and obese adolescents after combined training is associated with reduced insulin resistance.

Exercise training and a healthy diet are the main non-pharmacological strategies for treating chronic conditions, such as obesity and insulin resistance (IR), in adolescents. However, the isolated metabolic changes caused by exercise training without dietary intervention have not yet been established. We investigated how combined training (CT) without dietary intervention altered the concentrations of serum metabolites, biochemical, anthropometric and functional parameters in overweight and obese adolescents. Thirty-seven adolescents (14.6 ± 1.05 years), of both sexes, were randomly assigned to the control group (CG, n = 19) or the training group (TG, n = 18). The CT was composed by resistance training and aerobic training performed in the same session (~ 60 min), three times a week, for 12 weeks. All assessments were performed pre and post-intervention. Metabolomics analyses were conducted using nuclear magnetic resonance spectroscopy (1H NMR) in a 600 MHz spectrometer. There was a decrease in body weight (BW), body mass index (BMI), waist circumference (WC), % body fat (%BF), fasting glucose, insulin levels, and insulin resistance (IR), by HOMA-IR, in the TG. An increase in fat-free mass (FFM) was also observed in the CG. The metabolic changes were given mainly by changes in the levels of metabolites 2-oxoisocaproate (↓TG), 3-hydroxyisobutyrate (↑CG and ↓TG), glucose (↓TG), glutamine (↓CG and ↑TG) and pyruvate (↓TG). These findings demonstrate the positive effects of CT program without dietary intervention on metabolomic profile, body composition, biochemical markers, and glucose metabolism in overweight and obese adolescents.

Acute low- compared to high-load resistance training to failure results in greater energy expenditure during exercise in healthy young men.

The objective of the present study was to verify the energy expenditure (EE), energy system contributions and autonomic control during and after an acute low-load or high-load resistance training (RT) protocol to momentary failure (MF) in young adults. Eleven young men (22 ± 3 yrs, 71.8 ± 7.7 kg; 1.75 ± 0.06 m) underwent a randomized crossover design of three knee extension acute protocols: a low-load RT [30% of their maximal strength (1RM); RT30] or a high-load RT (80% of 1RM; RT80) protocol, with all sets being performed to MF; or a control session (Control) without exercise. Participants were measured for EE, energy system contributions, and cardiac autonomic control before, during, and after each exercise session. Exercise EE was significantly higher for RT30 as compared to RT80. Furthermore, post measurements of blood lactate levels and the anaerobic lactic system contribution were significantly greater for RT30 as compared to RT80. In addition, parasympathetic restoration was lower for RT30 as compared to RT80. In conclusion, a low-load (30% 1RM) RT session produced higher EE during exercise than a high-load (80% 1RM) RT session to MF, and may be a good option for fitness professionals, exercise physiologists, and practitioners when choosing the optimal RT protocol that provides more EE, especially for those who want or need to lose weight.

Augmented Anabolic Responses after 8-wk Cycling with Blood Flow Restriction.

INTRODUCTION: Low-intensity endurance training (ET) performed with blood flow restriction (BFR) can improve muscle strength, cross-sectional area (CSA) and cardiorespiratory capacity. Whether muscle strength and CSA as well as cardiorespiratory capacity (i.e., V˙O2max) and underlying molecular processes regulating such respective muscle adaptations are comparable to resistance and ET is unknown. PURPOSE: To determine the respective chronic (i.e., 8 wk) functional, morphological, and molecular responses of ET-BFR training compared with conventional, unrestricted resistance training (RT) and ET. METHODS: Thirty healthy young men were randomly assigned to one of three experimental groups: ET-BFR (n = 10, 4 d·wk, 30-min cycling at 40% of V˙O2max), RT (n = 10, 4 d·wk, 4 sets of 10 repetitions leg press at 70% of one repetition maximum with 60 s rest) or ET (n = 10, 4 d·wk, 30-min cycling at 70% of V˙O2max) for 8 wk. Measures of quadriceps CSA, leg press one repetition maximum, and V˙O2max as well as muscle biopsies were obtained before and after intervention. RESULTS: Both RT and ET-BFR increased muscle strength and hypertrophy responses. ET-BFR also increased V˙O2max, total cytochrome c oxidase subunit 4 isoform 1 abundance and vascular endothelial growth factor mRNA abundance despite the lower work load compared to ET. CONCLUSIONS: Eight weeks of ET-BFR can increase muscle strength and induce similar muscle hypertrophy responses to RT while V˙O2max responses also increased postintervention even with a significantly lower work load compared with ET. Our findings provide new insight to some of the molecular mechanisms mediating adaptation responses with ET-BFR and the potential for this training protocol to improve muscle and cardiorespiratory capacity.

Acute, short-, and long-term effects of different types of exercise in central arterial stiffness: a systematic review and meta-analysis.

INTRODUCTION: The independent predictor of cardiovascular mortality, central arterial stiffness (CAS), is modulated by exercise depending on type of exercises, arteries assessed, sample features and time to exposure. Thus, this study aim to determine the endurance, resistance and combined exercise effects on CAS over time in humans. EVIDENCE ACQUISITION: MEDLINE database for studies published between January 1st, 1990 and February 3rd, 2015. Studies measuring the effects of exercise on CAS, measured by aortic pulse wave velocity or carotid arterial compliance measured by ultrasound were included. Two independent reviewers extracted the 56 studies meta-analyzed and allocated among type of exercise and time effects categories: acute (10 minutes to 24 hours post-exercise session effect), short-term (interventional studies testing basal CAS from 1 to 24 weeks of exercise) and long-term (cross-sectional studies comparing trained and untrained individuals). EVIDENCE SYNTHESIS: We calculated standard difference in means 95% CIs, applying random or fixed-effects models, according to presence or absence of true heterogeneity, respectively. Endurance exercise reduced CAS in short and long-term analysis (-0.42 [-0.53 to -0.31] and -0.62 [-0.95 to -0.29], respectively), however it did not modify CAS acutely; higher magnitude of reduction occurred in normal weight individuals, with longer duration, higher weekly frequency and continuous (rather than interval) protocols. Resistance exercise increases CAS acutely (0.30 [0.01 to 0.58]) and after long-term (0.47 [0.19 to 0.75]), while short-term resistance exercise did not modify CAS significantly. No significant effect was found for short-term combined exercises and there was not enough number of studies for acute and long-term effects to be meta-analysed. CONCLUSIONS: Endurance and resistance exercise have opposite long-term effects, being beneficial and deleterious, respectively, while the combined exercise showed to be innocuous.

Exercise training protects human and rodent ß cells against endoplasmic reticulum stress and apoptosis.

Prolonged exercise has positive metabolic effects in obese or diabetic individuals. These effects are usually ascribed to improvements in insulin sensitivity. We evaluated whether exercise also generates circulating signals that protect human and rodent ß cells against endoplasmic reticulum (ER) stress and apoptosis. For this purpose, we obtained serum from humans or mice before and after an 8 wk training period. Exposure of human islets or mouse or rat ß cells to human or rodent sera, respectively, obtained from trained individuals reduced cytokine (IL-1ß+IFN-γ)- or chemical ER stressor-induced ß-cell ER stress and apoptosis, at least in part via activation of the transcription factor STAT3. These findings indicate that exercise training improves human and rodent ß-cell survival under diabetogenic conditions and support lifestyle interventions as a protective approach for both type 1 and 2 diabetes.-Paula, F. M. M., Leite, N. C., Borck, P. C., Freitas-Dias, R., Cnop, M., Chacon-Mikahil, M. P. T., Cavaglieri, C. R., Marchetti, P., Boschero, A. C., Zoppi, C. C., Eizirik, D. L. Exercise training protects human and rodent ß cells against endoplasmic reticulum stress and apoptosis.

Effects of combined training on total ghrelin and tumor necrosis factor-α in obese middle-aged men

Abstract AIMS The aim of the present study was to investigate the effects of combined training (CT) on total ghrelin and tumor necrosis factor-α (TNF-α) levels in obese middle-aged individuals. METHODS Twenty two obese middle-aged men (49.32 ± 5.74 years; Body mass index: 30.88 ± 1.64 kg/m²) were randomly assigned to a combined training group (CTG, n = 12) or a control group (CG, n = 10). The CT consisted of aerobic (50-85% of VO2peak) and resistance (6-10 RM) training performed three times per week, 60 min per session for 24 weeks. The anthropometric measurements, cardiorespiratory test (VO2peak), maximal strength assessment (1RM) and plasma concentrations of total ghrelin and TNF-α were determined before (Pre) and after 24 weeks (Post) of the experimental period. RESULTS Decreases were found in body fat percentage (Δ% -19.8) and waist circumference (Δ% -2.8) for CTG at the Post moment as compared to the Pre moment. In addition, the CTG demonstrated increases for VO2peak (Δ% 13.4) and for 1-RM of bench press (Δ% 78.1), leg press (Δ% 22.3) and arm curl (Δ% 19.3) at the Post moment as compared to the Pre moment. However, total ghrelin levels remained unchanged for CTG and CG after the experimental period, while TNF-α levels increased for CG (p ≤ 0.05). CONCLUSION the CT protocol performed was not effective in repairing total ghrelin levels and was not correlated with changes in the TNF-α; however, the exercise training was able to improve body composition and functional capabilities and contained the worsening of systemic inflammation associated to obesity.

Metabolomics Approach in the Investigation of Metabolic Changes in Obese Men after 24 Weeks of Combined Training.

Obesity is associated with comorbidities related to metabolic disorders due to excess of adipose tissue. Physical exercise has a major role in the prevention of obesity. Combined training (CT), in particular, has been shown to improve markers of health. In this study, we used 1H NMR-based metabolomics to investigate changes in the metabolism of obese men after 24 weeks of CT. Twenty-two obese (body mass index 31 ± 1.4 kg/m2), middle-aged men (48.2 ± 6.1 years) were randomly assigned to a control group (CG, n = 11) or CT group (n = 11). The CT was performed three times a week (resistance and aerobic training) for 24 weeks. Blood samples were collected before and after experimental period. There was an improvement in body composition and physical fitness indices after CT training. Multivariate PCA and PLS-DA models showed a distinct separation between groups. Twenty metabolites with importance for projection (VIP) >1.0 were identified, and four were classified as best discriminators (tyrosine, 2-oxoisocaproate, histidine, pyruvate). Some metabolites were correlated with strength, VO2 peak, fat and lean body mass, waist circumference, and insulin. In conclusion, 24 weeks of CT was effective for functional improvements and metabolic changes in obese middle-aged men.

Interleukin-6 increases the expression and activity of insulin-degrading enzyme.

Impairment of the insulin-degrading enzyme (IDE) is associated with obesity and type 2 diabetes mellitus (T2DM). Here, we used 4-mo-old male C57BL/6 interleukin-6 (IL-6) knockout mice (KO) to investigate the role of this cytokine on IDE expression and activity. IL-6 KO mice displayed lower insulin clearance in the liver and skeletal muscle, compared with wild type (WT), due to reduced IDE expression and activity. We also observed that after 3-h incubation, IL-6, 50 and 100 ng ml-1, increased the expression of IDE in HEPG2 and C2C12 cells, respectively. In addition, during acute exercise, the inhibition of IL-6 prevented an increase in insulin clearance and IDE expression and activity, mainly in the skeletal muscle. Finally, IL-6 and IDE concentrations were significantly increased in plasma from humans, after an acute exercise, compared to pre-exercise values. Although the increase in plasma IDE activity was only marginal, a positive correlation between IL-6 and IDE activity, and between IL-6 and IDE protein expression, was observed. Our outcomes indicate a novel function of IL-6 on the insulin metabolism expanding the possibilities for new potential therapeutic strategies, focused on insulin degradation, for the treatment and/or prevention of diseases related to hyperinsulinemia, such as obesity and T2DM.

Acute low-intensity cycling with blood-flow restriction has no effect on metabolic signaling in human skeletal muscle compared to traditional exercise.

PURPOSE: Autophagy is an intracellular degradative system sensitive to hypoxia and exercise-induced perturbations to cellular bioenergetics. We determined the effects of low-intensity endurance-based exercise performed with blood-flow restriction (BFR) on cell signaling adaptive responses regulating autophagy and substrate metabolism in human skeletal muscle. METHODS: In a randomized cross-over design, nine young, healthy but physically inactive males completed three experimental trials separated by 1 week of recovery consisting of either a resistance exercise bout (REX: 4 × 10 leg press repetitions, 70% 1-RM), endurance exercise (END: 30 min cycling, 70% VO2peak), or low-intensity cycling with BFR (15 min, 40% VO2peak). A resting muscle biopsy was obtained from the vastus lateralis 2 weeks prior to the first exercise trial and 3 h after each exercise bout. RESULTS: END increased ULK1Ser757 phosphorylation above rest and BFR (~37 to 51%, P < 0.05). Following REX, there were significant elevations compared to rest (~348%) and BFR (~973%) for p38γ MAPKThr180/Tyr182 phosphorylation (P < 0.05). Parkin content was lower following BFR cycling compared to REX (~20%, P < 0.05). There were no exercise-induced changes in select markers of autophagy following BFR. Genes implicated in substrate metabolism (HK2 and PDK4) were increased above rest (~143 to 338%) and BFR cycling (~212 to 517%) with END (P < 0.001). CONCLUSION: A single bout of low-intensity cycling with BFR is insufficient to induce intracellular "stress" responses (e.g., high rates of substrate turnover and local hypoxia) necessary to activate skeletal muscle autophagy signaling.

Time Course of Resistance Training-Induced Muscle Hypertrophy in the Elderly.

Extended periods of resistance training (RT) induce muscle hypertrophy. Nevertheless, to date, no study has investigated the time window necessary to observe significant changes in muscle cross-sectional area (CSA) in older adults. Therefore, this study investigated the time course of muscle hypertrophy after 10 weeks (20 sessions) of RT in the elderly. Fourteen healthy older subjects were randomly allocated in either the RT (n: 6) or control group (n: 8). The RT was composed of 4 sets × 10 repetitions (70-80% 1 repetition maximum [1RM]) in a leg press machine. The time course of vastus lateralis muscle hypertrophy (CSA) was assessed on a weekly basis by mode-B ultrasonography. Leg press muscle strength was assessed by dynamic 1RM test. Our results demonstrated that the RT group increased leg press 1RM by 42% (p ≤ 0.05) after 10 weeks of training. Significant increases in vastus lateralis muscle CSA were observed only after 18 sessions of training (9 weeks; p ≤ 0.05; 7.1%). In conclusion, our training protocol promoted muscle mass accrual in older subjects, and this was only observable after 18 sessions of RT (9 weeks).

Vastus lateralis muscle cross-sectional area ultrasonography validity for image fitting in humans.

The present study aimed to determine the concurrent validity of ultrasound (US) measurement of the vastus lateralis muscle (VL) cross-sectional area (CSA) having magnetic resonance imaging (MRI) as the gold standard measurement, in a heterogeneous sample of participants. Thirty-one individuals (52.44 ± 16.37 years; 1.67 ± 0.11 m; 75.25 ± 13.82 kg) volunteered to participate in the study. All the images were performed in the right leg. Image-fitting technique (US) and computerized planimetry technique (US and MRI) were used to determine the VL CSA. The typical error (TE) of measurement was used to determine the concurrent validity of the US measurements. Our results demonstrated good validity of the US compared with the MRI measurements (TE = 0.37 cm; coefficient of variation = 1.75%). The Bland-Altman plot demonstrated bias of 0.07 ± 0.53 cm and limits of agreement of 0.96-1.11 cm. Based on our TE, bias and limits of agreement, we concluded that the US image-fitting technique is valid to assess the VL CSA in a heterogeneous sample of participants. Thereby, US can be used instead of MRI to assess changes in skeletal muscle morphology.

Effects of concurrent training on interleukin-6, tumour necrosis factor-alpha and C-reactive protein in middle-aged men.

The purpose of this study was to evaluate the effects of moderate- to high-intensity resistance and concurrent training on inflammatory biomarkers and functional capacity in sedentary middle-aged healthy men. Participants were selected on a random basis for resistance training (n = 12), concurrent training (n = 11) and a control group (n = 13). They performed three weekly sessions for 16 weeks (resistance training: 10 exercises with 3 × 8-10 repetition maximum; concurrent training: 6 exercises with 3 × 8-10 repetition maximum, followed by 30 minutes of walking or running at 55-85% [Vdot]O(2peak)). Maximal strength was tested in bench press and leg press. The peak oxygen uptake ([Vdot]O(2peak)) was measured by an incremental exercise test. Tumour necrosis factor-α, interleukin-6 and C-reactive protein were determined. The upper- and lower-body maximal strength increase for both resistance (+42.52%; +20.9%, respectively) and concurrent training (+28.35%; +21.5%, respectively) groups (P = 0.0001).[Vdot]O(2peak) increased in concurrent training when comparing pre- and post-training (P = 0.0001; +15.6%). No differences were found in tumour necrosis factor-α and interleukin-6 for both groups after the exercise. C-reactive protein increased in resistance training (P = 0.004). These findings demonstrated that 16 weeks of moderate- to high-intensity training could improve functional capacity, but did not decrease inflammatory biomarkers in middle-aged men.

Electromyographic activity and rate of muscle fatigue of the quadriceps femoris during cycling exercise in the severe domain.

This study compared the activation pattern and the fatigue rate among the superficial muscles of the quadriceps femoris (QF) during severe cycling exercise. Peak oxygen consumption (VO(2)peak) and maximal accumulated oxygen Deficit (MAOD) were established by 10 well-trained male cyclists (27.5 ± 4.1 years, 71.0 ± 10.3 kg, 173.4 ± 6.6 cm, mean VO(2)peak 56.7 ± 4.4 ml·kg·min(-1), mean MAOD 5.7 ± 1.1 L). Muscle activity (electromyographic [EMG] signals) was obtained during the supramaximal constant workload test (MAOD) and expressed by root mean square (RMS) and median frequency (MF slope). The RMS of the QF, vastus lateralis (VL) and vastus medialis (VM) muscles were significantly higher than at the beginning after 75% of exercise duration, whereas for the rectus femoris (RF), this was observed after 50% of exercise duration (p ≤ 0.05). The slope of the MF was significantly higher in the RF, followed by the VL and VM (-3.13 ± 0.52 vs. -2.61 ± 0.62 vs. -1.81 ±0.56, respectively; p < 0.05). We conclude that RF may play an important role in limiting performance during severe cycling exercise.

Determinação do máximo déficit acumulado de oxigênio: efeito da duração dos testes submáximos para predição da demanda de oxigênio / Determination of the maximum accumulated oxygen deficit: effects of the submaximal tests duration for prediction of oxygen demand

O objetivo do presente estudo foi verificar a influência de diferentes tempos de análise dos testes submáximos para determinação do máximo déficit acumulado de oxigênio (MAOD), adotando diferentes janelas de tempo 4-6min, 6-8min e 8-10min. Participaram do estudo 10 ciclistas com idade média de 27,5 ± 4,1 anos, massa corporal 74,4 ± 12,7kg e tempo médio de prática de 9,8 ± 4,7 anos. Os atletas realizaram um teste de esforço progressivo para determinação do consumo de oxigênio de pico (VO2pico) e quatro testes retangulares submáximos (60, 70, 80 e 90 por cento VO2pico) com 10min de duração para estimar os valores da demanda de O2 (DEO2). Os valores médios de VO2 obtidos nas cargas para o tempo 4-6min, 6-8min e 8 a 10min foram aplicados em uma regressão linear entre a intensidade e o consumo de O2 para cada janela de tempo. Os sujeitos realizaram ainda um teste retangular supramáximo (110 por cento VO2pico) para a quantificação do MAOD. Não foi constatada nenhuma diferença significativa no VO2 entre os diferentes períodos de tempo dos testes submáximos (P > 0,05). Da mesma forma, nenhuma diferença significativa foi constatada no DEAO2 e MAOD nos diferentes períodos de análise (P > 0,05). Verificou-se ainda que os valores de MAOD obtidos nos três intervalos de tempo apresentaram boa concordância e forte correlação. Dessa forma, os dados sugerem que os testes submáximos utilizados para gerar os valores do MAOD podem ser reduzidos ao menos nesse tipo de amostra e com a utilização de ciclossimulador.

The aim of this study was to investigate the influence of different assessment time periods of submaximal tests on the determination of the maximal accumulated oxygen deficit (MAOD), through the adoption of different time slots of 4 to 6, 6 to 8 and 8 to 10 min. Ten cyclists with mean age of 27.5 ± 4.1 years, body mass 74.4 ± 12.7 kg and time experience of 9.8 ± 4.7 years participated in this study. The athletes underwent an incremental exercise test to determine the peak oxygen consumption (VO2peak), and four submaximal constant work-load test sessions (60, 70, 80 and 90 percent VO2peak) of 10 min in order to estimate the O2 demand (DEO2). The mean VO2 values obtained on each constant work-load for the 4 to 6, 6 to 8 and 8 to 10 min time-periods intervals were used to perform a linear regression between the intensity and O2 consumption for each time-period. In addition, the subjects performed one supramaximal rectangular test (110 percent VO2peak) for the quantification of MAOD. There was no significant difference in VO2 between the different time-periods for all submaximal tests (P> 0.05). Similarly, no significant difference was found in DEAO2 and MAOD (P> 0.05). Furthermore, the values of MAOD for the three time-periods intervals showed good agreement and strong correlation. Thus, the data suggest that the submaximal tests used to estimate the values of MAOD can be reduced, at least in this type of sample, and with the use of a cycle simulator.