The psychobiological model: a new explanation to intensity regulation and (in)tolerance in endurance exercise

The mechanisms underpinning fatigue and exhaustion, and the specific sources of exercise-endurance intensity regulation and (in)tolerance have been investigated for over a century. Although several scientific theories are currently available, over the past five years a new framework called Psychobiological model has been proposed. This model gives greater attention to perceptual and motivational factors than its antecedents, and their respective influence on the conscious process of decision-making and behavioral regulation. In this review we present experimental evidences and summarize the key points of the Psychobiological model to explain intensity regulation and (in)tolerance in endurance exercise. Still, we discuss how the Psychobiological model explains training-induced adaptations related to improvements in performance, experimental manipulations, its predictions, and propose future directions for this investigative area. The Psychobiological model may give a new perspective to the results already published in the literature, helping scientists to better guide their research problems, as well as to analyze and interpret new findings more accurately.

Predição da performance de corredores de endurance por meio de testes de laboratório e pista

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

Endurance exercise training increases APPL1 expression and improves insulin signaling in the hepatic tissue of diet-induced obese mice, independently of weight loss

Hepatic insulin resistance is the major contributor to fasting hyperglycemia in type 2 diabetes. The protein kinase Akt plays a central role in the suppression of gluconeogenesis involving forkhead box O1 (Foxo1) and peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1a), and in the control of glycogen synthesis involving the glycogen synthase kinase beta (GSK3 beta) in the liver. It has been demonstrated that endosomal adaptor protein APPL1 interacts with Akt and blocks the association of Akt with its endogenous inhibitor, tribbles-related protein 3 (TRB3), improving the action of insulin in the liver. Here, we demonstrated that chronic exercise increased the basal levels and insulin-induced Akt serine phosphorylation in the liver of diet-induced obese mice. Endurance training was able to increase APPL1 expression and the interaction between APPL1 and Akt. Conversely, training reduced both TRB3 expression and TRB3 and Akt association. The positive effects of exercise on insulin action are reinforced by our findings that showed that trained mice presented an increase in Foxo1 phosphorylation and Foxo1/PGC-1a association, which was accompanied by a reduction in gluconeogenic gene expressions (PEPCK and G6Pase). Finally, exercised animals demonstrated increased at basal and insulin-induced GSK3 beta phosphorylation levels and glycogen content at 24?h after the last session of exercise. Our findings demonstrate that exercise increases insulin action, at least in part, through the enhancement of APPL1 and the reduction of TRB3 expression in the liver of obese mice, independently of weight loss. J. Cell. Physiol. 227: 29172926, 2012. (C) 2011 Wiley Periodicals, Inc.

Similar health benefits of endurance and high-intensity interval training in obese children

Purpose: To compare two modalities of exercise training (i.e., Endurance Training [ET] and High-Intensity Interval Training [HIT]) on health-related parameters in obese children aged between 8 and 12 years. Methods: Thirty obese children were randomly allocated into either the ET or HIT group. The ET group performed a 30 to 60-minute continuous exercise at 80% of the peak heart rate (HR). The HIT group training performed 3 to 6 sets of 60-s sprint at 100% of the peak velocity interspersed by a 3-min active recovery period at 50% of the exercise velocity. HIT sessions last similar to 70% less than ET sessions. At baseline and after 12 weeks of intervention, aerobic fitness, body composition and metabolic parameters were assessed. Results: Both the absolute (ET: 26.0%; HIT: 19.0%) and the relative VO2 peak (ET: 13.1%; HIT: 14.6%) were significantly increased in both groups after the intervention. Additionally, the total time of exercise (ET: 19.5%; HIT: 16.4%) and the peak velocity during the maximal graded cardiorespiratory test (ET: 16.9%; HIT: 13.4%) were significantly improved across interventions. Insulinemia (ET: 29.4%; HIT: 30.5%) and HOMA-index (ET: 42.8%; HIT: 37.0%) were significantly lower for both groups at POST when compared to PRE. Body mass was significantly reduced in the HIT (2.6%), but not in the ET group (1.2%). A significant reduction in BMI was observed for both groups after the intervention (ET: 3.0%; HIT: 5.0%). The responsiveness analysis revealed a very similar pattern of the most responsive variables among groups. Conclusion: HIT and ET were equally effective in improving important health related parameters in obese youth.

Endurance training stimulates growth and survival pathways and the redox balance in rat pancreatic islets

Calegari VC, Abrantes JL, Silveira LR, Paula FM, Costa JM Jr, Rafacho A, Velloso LA, Carneiro EM, Bosqueiro JR, Boschero AC, Zoppi CC. Endurance training stimulates growth and survival pathways and the redox balance in rat pancreatic islets. J Appl Physiol 112: 711-718, 2012. First published December 15, 2011; doi:10.1152/japplphysiol.00318.2011.-Endurance training has been shown to increase pancreatic beta-cell function and mass. However, whether exercise modulates beta-cell growth and survival pathways signaling is not completely understood. This study investigated the effects of exercise on growth and apoptotic markers levels in rat pancreatic islets. Male Wistar rats were randomly assigned to 8-wk endurance training or to a sedentary control group. After that, pancreatic islets were isolated; gene expression and the total content and phosphorylation of several proteins related to growth and apoptotic pathways as well as the main antioxidant enzymes were determined by real-time polymerase chain reaction and Western blot analysis, respectively. Reactive oxygen species (ROS) production was measured by fluorescence. Endurance training increased the time to reach fatigue by 50%. Endurance training resulted in increased protein phosphorylation content of AKT (75%), AKT substrate (AS160; 100%), mTOR (60%), p70s6k (90%), and ERK1/2 (50%), compared with islets from control group. Catalase protein content was 50% higher, whereas ROS production was 49 and 77% lower in islets from trained rats under basal and stimulating glucose conditions, respectively. Bcl-2 mRNA and protein levels increased by 46 and 100%, respectively. Bax and cleaved caspase-3 protein contents were reduced by 25 and 50% in islets from trained rats, respectively. In conclusion, these results demonstrate that endurance training favors the beta-cell growth and survival by activating AKT and ERK1/2 pathways, enhancing antioxidant capacity, and reducing ROS production and apoptotic proteins content.

Isokinetic Strength and Endurance in Proximal and Distal Muscles in Patients With Peripheral Artery Disease

Background: The objective of this study was to analyze the muscle strength and endurance of the proximal and distal lower-extremity muscles in peripheral artery disease (PAD) patients. Methods: Twenty patients with bilateral PAD with symptoms of intermittent claudication and nine control subjects without PAD were included in the study, comprising 40 and 18 legs, respectively. All subjects performed an isokinetic muscle test to evaluate the muscle strength and endurance of the proximal (knee extension and knee flexion movements) and distal (plantar flexion and dorsiflexion movements) muscle groups in the lower extremity. Results: Compared with the control group, the PAD group presented lower muscle strength in knee flexion (-14.0%), dorsiflexion (-26.0%), and plantar flexion (-21.2%) movements (P < 0.05) but similar strength in knee extension movements (P > 0.05). The PAD patients presented a 13.5% lower knee flexion/extension strength ratio compared with the control subjects (P < 0.05), as well as lower muscle endurance in dorsiflexion (-28.1%) and plantar flexion (-17.0%) movements (P < 0.05). The muscle endurance in knee flexion and knee extension movements was similar between PAD patients and the control subjects (P > 0.05). Conclusion: PAD patients present lower proximal and distal muscle strength and lower distal muscle endurance than control patients. Therefore, interventions to improve muscle strength and endurance should be prescribed for PAD patients.

The effects of long-term endurance training on the immune and endocrine systems of elderly men: the role of cytokines and anabolic hormones

Abstract Background a decline in immune and endocrine function occurs with aging. The main purpose of this study was to investigate the impact of long-term endurance training on the immune and endocrine system of elderly men. The possible interaction between these systems was also analysed. Results elderly runners showed a significantly higher T cell proliferative response and IL-2 production than sedentary elderly controls. IL-2 production was similar to that in young adults. Their serum IL-6 levels were significantly lower than their sedentary peers. They also showed significantly lower IL-3 production in comparison to sedentary elderly subjects but similar to the youngs. Anabolic hormone levels did not differ between elderly groups and no clear correlation was found between hormones and cytokine levels. Conclusion highly conditioned elderly men seem to have relatively better preserved immune system than the sedentary elderly men. Long-term endurance training has the potential to decelerate the age-related decline in immune function but not the deterioration in endocrine function.

Anaerobic energy provision does not limit Wingate exercise performance in endurance-trained cyclists

[EN] The aim of this study was to evaluate the effects of severe acute hypoxia on exercise performance and metabolism during 30-s Wingate tests. Five endurance- (E) and five sprint- (S) trained track cyclists from the Spanish National Team performed 30-s Wingate tests in normoxia and hypoxia (inspired O(2) fraction = 0.10). Oxygen deficit was estimated from submaximal cycling economy tests by use of a nonlinear model. E cyclists showed higher maximal O(2) uptake than S (72 +/- 1 and 62 +/- 2 ml x kg(-1) x min(-1), P < 0.05). S cyclists achieved higher peak and mean power output, and 33% larger oxygen deficit than E (P < 0.05). During the Wingate test in normoxia, S relied more on anaerobic energy sources than E (P < 0.05); however, S showed a larger fatigue index in both conditions (P < 0.05). Compared with normoxia, hypoxia lowered O(2) uptake by 16% in E and S (P < 0.05). Peak power output, fatigue index, and exercise femoral vein blood lactate concentration were not altered by hypoxia in any group. Endurance cyclists, unlike S, maintained their mean power output in hypoxia by increasing their anaerobic energy production, as shown by 7% greater oxygen deficit and 11% higher postexercise lactate concentration. In conclusion, performance during 30-s Wingate tests in severe acute hypoxia is maintained or barely reduced owing to the enhancement of the anaerobic energy release. The effect of severe acute hypoxia on supramaximal exercise performance depends on training background.

Design and Prototyping High Endurance Multi-Rotor

The topic of this thesis fo cus on the preliminary design and the p erformance analysis of a multirotor platform. A multirotor is an electrically p owered Vertical Take Off (VTOL) machine with more than two rotors that lift and control the platform. Multirotor are agile, compact and robust, making them ideally suited for b oth indo or and outdo or application especially to carry-on several sensors like electro optical multisp ectral sensor or gas sensor. The main disadvantage is the limited endurance due to heavy Li-Po batteries and high disk loading through the use of different small prop ellers. At the same time, the design of the multirotor do es not follow any engineering principle but it follow the ideas of amateurs’ builder. An adaptation of the classic airplane design theory for the preliminary design is implemented to fill the gap and detailed study of the endurance is p erformed to define the right way to make this kind of VTOL platforms.

A hypoxia complement differentiates the muscle response to endurance exercise

Metabolic stress is believed to constitute an important signal for training-induced adjustments of gene expression and oxidative capacity in skeletal muscle. We hypothesized that the effects of endurance training on expression of muscle-relevant transcripts and ultrastructure would be specifically modified by a hypoxia complement during exercise due to enhanced glycolytic strain. Endurance training of untrained male subjects in conditions of hypoxia increased subsarcolemmal mitochondrial density in the recruited vastus lateralis muscle and power output in hypoxia more than training in normoxia, i.e. 169 versus 91% and 10 versus 6%, respectively, and tended to differentially elevate sarcoplasmic volume density (42 versus 20%, P = 0.07). The hypoxia-specific ultrastructural adjustments with training corresponded to differential regulation of the muscle transcriptome by single and repeated exercise between both oxygenation conditions. Fine-tuning by exercise in hypoxia comprised gene ontologies connected to energy provision by glycolysis and fat metabolism in mitochondria, remodelling of capillaries and the extracellular matrix, and cell cycle regulation, but not fibre structure. In the untrained state, the transcriptome response during the first 24 h of recovery from a single exercise bout correlated positively with changes in arterial oxygen saturation during exercise and negatively with blood lactate. This correspondence was inverted in the trained state. The observations highlight that the expression response of myocellular energy pathways to endurance work is graded with regard to metabolic stress and the training state. The exposed mechanistic relationship implies that the altitude specificity of improvements in aerobic performance with a 'living low-training high' regime has a myocellular basis.

REGULATION OF WHOLE-BODY ENERGY HOMEOSTASIS WITH GROWTH HORMONE REPLACEMENT THERAPY AND ENDURANCE EXERCISE

We hypothesized that network analysis is useful to expose coordination between whole body and myocellular levels of energy metabolism and can identify entities that underlie skeletal muscle's contribution to growth hormone-stimulated lipid handling and metabolic fitness. We assessed 112 metabolic parameters characterizing metabolic rate and substrate handling in tibialis anterior muscle and vascular compartment at rest, after a meal and exercise with growth hormone replacement therapy (GH-RT) of hypopituitary patients (n = 11). The topology of linear relationships (| r | ≥ 0.7, P ≤ 0.01) and mutual dependencies exposed the organization of metabolic relationships in three entities reflecting basal and exercise-induced metabolic rate, triglyceride handling, and substrate utilization in the pre- and postprandial state, respectively. GH-RT improved aerobic performance (+5%), lean-to-fat mass (+19%), and muscle area of tibialis anterior (+2%) but did not alter its mitochondrial and capillary content. Concomitantly, connectivity was established between myocellular parameters of mitochondrial lipid metabolism and meal-induced triglyceride handling in serum. This was mediated via the recruitment of transcripts of muscle lipid mobilization (LIPE, FABP3, and FABP4) and fatty acid-sensitive transcription factors (PPARA, PPARG) to the metabolic network. The interdependence of gene regulatory elements of muscle lipid metabolism reflected the norm in healthy subjects (n = 12) and distinguished the regulation of the mitochondrial respiration factor COX1 by GH and endurance exercise. Our observations validate the use of network analysis for systems medicine and highlight the notion that an improved stochiometry between muscle and whole body lipid metabolism, rather than alterations of single bottlenecks, contributes to GH-driven elevations in metabolic fitness.