Background: Obesity-induced alterations in biomechanics and muscle recruitment during activities of daily living, such as sit-to-stand (STS) are often attributed to increases in adipose tissue (AT) mass. Central or peripheral distribution of AT may differently affect biomechanics and muscle recruitment. Methods: Fifteen healthy, normal weight (BMI 22.4 ± 1.9 kg/m2, 24.1 ± 4.2 years) subjects volunteered. External loads equivalent to a 5 kg/m2 BMI increase were applied in three conditions: unloaded (UN), centrally loaded (CL), and peripherally loaded (PL). Subjects completed three successful STS movements in a backless chair under each load condition in random order. Motion analysis and lower extremity surface electromyography (EMG) were measured. Results: Compared to UN and CL, PL significantly increased support width during STS. PL also significantly increased maximum trunk flexion compared to CL. Peak and total VM EMG activity were significantly increased during CL, compared to UN and PL. During CL, peak VL EMG activity was significantly greater than UN. Conclusions: Central and peripheral weight gain induce different biomechanical adaptations during STS. Central weight gain increases knee extensor muscle activity during STS independent of biomechanical changes. In contrast, peripheral weight gain increases support width and trunk flexion with minimal EMG changes during STS.

Background: Vitamin D is crucial for skeletal muscle function. 25-hidroxyvitamin D (25(OH)D) has been correlated with skeletal muscle mass and intramyocellular lipid (IMCL) content. The purpose of this study was to understand how calcitriol, the active vitamin D metabolite, directly affects myocellular size and lipid partitioning. Methods: C2C12 myotubes were treated with calcitriol (100nM) or vehicle control for 24 or 96 h. Myotube diameter and protein synthesis rate were measured to determine effects of calcitriol on myocellular size. Intramyocellular triacylglycerol (IMTG), diacylglycerol (DAG), and ceramide content were measured by LC/MS. Expression of genes involved in lipid packaging and lipolysis were measured by RT-PCR. Insulin-stimulated phosphorylated Akt (Thr 308) was determined by western blot. Results: Calcitriol did not affect myocellular size or protein synthesis rate. Calcitriol increased total DAG and ceramides in a sub-species specific manner. Calcitriol increased IMTG area, but did not affect total IMTG content. Calcitriol reduced mRNA content of diglyceride acyltransferase and increased mRNA content of lipid packaging genes. Calcitriol did not negatively affect insulin-stimulated pAkt. Conclusions: These results suggest calcitriol directly alters lipid content and packaging in skeletal muscle cells. Altering the expression of lipid packaging genes and increasing IMCL subspecies content may be mechanisms by which vitamin D improves skeletal muscle function in vivo.

Les travaux conduits dans le cadre de cette thèse avaient pour objectif d’étudier les mécanismes psychophysiologiques impliqués dans la mobilisation et la gestion des ressources nécessaires à la réalisation d’une performance de haut niveau en cyclisme sur route. Les mécanismes centraux et les paramètres psychologiques susceptibles d’influencer la commande motrice ont ainsi été analysés dans le contexte de compétitions cyclistes de haut-niveau.L’ensemble des résultats obtenus mettent en évidence que les mécanismes de régulation de l’intensité d’exercice, évalués à l’aide de la nouvelle méthode « Exposure Variation Analysis » (EVA) développée dans le cadre de cette thèse, seraient des paramètres déterminants pour la performance cycliste en contre-la-montre (CLM). En compétition officielle, la capacité du cycliste à exploiter au mieux ses qualités physiques et donc à développer la plus haute puissance moyenne possible était directement reliée à sa capacité à maintenir un niveau d’intensité d’exercice constant sur l’ensemble du CLM. De plus, cette justesse de régulation de l’intensité de l’effort serait également liée aux paramètres psychologiques de plaisir ressenti et de focus attentionnel : plus l’athlète ressentait un plaisir important et était capable de focaliser ses pensées sur des éléments extérieurs pertinents pour la performance et plus il était capable de maintenir un niveau de puissance constant sur l’ensemble de l’effort. Ainsi, la performance cycliste serait dépendante de l’interaction complexe entre les paramètres psychologiques, les mécanismes de régulation de l’effort et les qualités physiques des athlètes.Cependant, les résultats des études menées dans le cadre de cette thèse mettent également en évidence que les mécanismes de régulation de l’intensité d’exercice et les paramètres psychologiques associés varient selon le contexte environnemental et les caractéristiques de l’effort réalisé. Par exemple, la présence d’un équipier en montée permettrait au cycliste de ressentir un plaisir plus élevé pendant l’effort et de puiser davantage dans ses réserves afin de réaliser un sprint final plus important dans les derniers mètres avant l’arrivée. A l’inverse, les cyclistes de niveau élite possèderaient des qualités de gestion de l’effort remarquables leur permettant de réguler l’effort de manière identique lors de plusieurs montées répétées que lors d’un effort unique. L’étude de la performance cycliste doit donc prendre en compte le contexte environnemental ainsi que les caractéristiques des athlètes et de l’effort réalisé afin de réellement permettre une compréhension complète de la performance cycliste de haut-niveau.De plus, ces résultats mettent également en évidence que les mécanismes de régulation de l’effort peuvent évoluer entre les différentes compétitions, et pourraient ainsi expliquer les variations journalières de performance pour un même niveau de qualité physique. Les travaux menés dans le cadre de cette thèse ont ainsi tenté d’optimiser la méthode EVA afin de permettre le suivi de la justesse des mécanismes de régulation de l’effort du cycliste lors de plusieurs CLM. Cette méthode pourrait se révéler très intéressante pour les entraîneurs et les athlètes sur le terrain afin de tenter d’optimiser leurs mécanismes de régulation de l’effort avec l’entraînement dans le but d’exploiter au mieux leurs qualités physiques. Des techniques psychologiques pourraient notamment être utilisées afin d’augmenter le plaisir ressenti des athlètes ou d’optimiser leur gestion des pensées pendant l’effort, leur permettant ainsi de mieux réguler l’intensité d’exercice et d’améliorer leurs performances en CLM. / The studies conducted during this PhD thesis aimed to analyse the psychophysiological mechanisms of effort regulation during elite road cycling performance. Central mechanisms and psychological parameters influencing motor units recruitment were studied in different contexts of elite road cycling competitions.All the results show that exercise intensity regulation, quantified using the “Exposure Variation Analysis” method developed during this PhD, is a key parameter of cycling individual time-trial (ITT) performance. During official competitive ITT, the cyclists’ abilities to have a maximal use of their physical capacities in order to develop the highest mean power output possible was strongly related to their abilities to maintain a constant level of exercise intensity during the entire ITT. These exercise intensity regulation mechanisms were also strongly related to pleasure and attentional focus psychological parameters: the more the athletes felt a high level of pleasure and were able to focus mainly on external thoughts salient to the performance, the more they were able to maintain a constant power output over the entire ITT. Cycling performance seems related to the complex interaction between psychological parameters, exercise intensity regulation mechanisms and physical capacities.However, the studies conducted also revealed that exercise intensity regulation mechanisms and psychological parameters varied depending on the environmental context and the characteristics of the effort. For example, a leading teammate in uphill cycling allowed the athlete to increase their pleasure and to dig deeper into their physiological reserves in order to perform a greater end-spurt. Conversely, elite cyclists exhibited outstanding exercise intensity regulation capacities which allowed them to regulate their effort during repeated uphill ITT in the same way that during single ITT. Consequently, the study of elite cycling performance must consider both environmental context and characteristics of the athletes concerned to allow a complete understanding of the mechanisms underlying performance.Furthermore, these results also underline that exercise intensity regulation mechanisms can vary between races, and consequently can explain the day-to-day variability in cycling performance despite similar physical capacities. Thus, the EVA method was optimised in order to monitor exercise intensity regulation mechanisms during several ITT performed by the same athletes. This method can be interesting for coaches and athletes on the field to try to improve their exercise intensity regulation with training. Specific psychological interventions can be added to the training programs in order to help the athlete to increase their pleasure or to improve their attentional focus, allowing them to improve their exercise intensity regulation and to have a greater use of their physical capacities during ITT.

Pre-training muscle characteristics of subjects who are obese determine how well exercise training will improve their insulin responsiveness. J Strength Cond Res 31(3): 798–808, 2017—Only half of prediabetic subjects who are obese who underwent exercise training without weight loss increased their insulin responsiveness. We hypothesized that those who improved their insulin responsiveness might have pretraining characteristics favoring a positive response to exercise training. Thirty nondiabetic subjects who were obese volunteered for 8 weeks of either strength training or endurance training. During training, subjects increased their caloric intake to prevent weight loss. Insulin responsiveness by euglycemic clamps and muscle fiber composition, and expression of muscle key biochemical pathways were quantified. Positive responders initially had 52% higher intermediate muscle fibers (fiber type IIa) with 27% lower slow-twitch fibers (type I) and 23% lower expression of muscle insulin receptors. Whether after weight training or stationary bike training, positive responders' fiber type shifted away from type I and type IIa fibers to an increased proportion of type IIx fibers (fast twitch). Muscle insulin receptor expression and glucose transporter type 4 (GLUT4) expression increased in all trained subjects, but these moderate changes did not consistently translate to improvement in whole-body insulin responsiveness. Exercise training of previously sedentary subjects who are obese can result in muscle remodeling and increased expression of key elements of the insulin pathway, but in the absence of weight loss, insulin sensitivity improvement was modest and limited to about half of the participants. Our data suggest rather than responders being more fit, they may have been less fit, only catching up to the other half of subjects who are obese whose insulin responsiveness did not increase beyond their pretraining baseline.

Introduction Insulin resistance in obesity is decreased after successful diet and exercise. Aerobic exercise training alone was evaluated as an intervention in subjects with the metabolic syndrome. Methods Eighteen nondiabetic, sedentary subjects, 11 with the metabolic syndrome, participated in 8 wk of increasing intensity stationary cycle training. Results Cycle training without weight loss did not change insulin resistance in metabolic syndrome subjects or sedentary control subjects. Maximal oxygen consumption (V˙O2max), activated muscle AMP-dependent kinase, and muscle mitochondrial marker ATP synthase all increased. Strength, lean body mass, and fat mass did not change. The activated mammalian target of rapamycin was not different after training. Training induced a shift in muscle fiber composition in both groups but in opposite directions. The proportion of type 2x fibers decreased with a concomitant increase in type 2a mixed fibers in the control subjects, but in metabolic syndrome, type 2x fiber proportion increased and type 1 fibers decreased. Muscle fiber diameters increased in all three fiber types in metabolic syndrome subjects. Muscle insulin receptor expression increased in both groups, and GLUT4 expression increased in the metabolic syndrome subjects. The excess phosphorylation of insulin receptor substrate 1 (IRS-1) at Ser337 in metabolic syndrome muscle tended to increase further after training in spite of a decrease in total IRS-1. Conclusions In the absence of weight loss, the cycle training of metabolic syndrome subjects resulted in enhanced mitochondrial biogenesis and increased the expression of insulin receptors and GLUT4 in muscle but did not decrease the insulin resistance. The failure for the insulin signal to proceed past IRS-1 tyrosine phosphorylation may be related to excess serine phosphorylation at IRS-1 Ser337, and this is not ameliorated by 8 wk of endurance exercise training.

Submitted by WILMER ALEJANDRO ZAMORA RESTAN null (alejomvz1208@gmail.com) on 2017-03-21T13:20:32Z No. of bitstreams: 1 Dissertação Final[924].pdf: 1300036 bytes, checksum: a71c43e8746de0b8643dcf3f0300ac03 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-03-22T14:28:53Z (GMT) No. of bitstreams: 1 zamorarestan_wa_me_jabo.pdf: 1300036 bytes, checksum: a71c43e8746de0b8643dcf3f0300ac03 (MD5) / Made available in DSpace on 2017-03-22T14:28:53Z (GMT). No. of bitstreams: 1 zamorarestan_wa_me_jabo.pdf: 1300036 bytes, checksum: a71c43e8746de0b8643dcf3f0300ac03 (MD5) Previous issue date: 2017-02-22 / O propósito deste estudo foi comparar métodos para determinação dos limiares relacionados com curvas de lactato plasmático e suas intensidades. Determinaram-se os limiares (1) de lactato (LTv) e (2) glicêmico (GTv) visualmente, (3) o limiar de lactato por meio do modelo polinomial (LTp), (4) limiar de glicose pelo modelo polinomial (GTp) e (5) o ponto de deflexão da frequência cardíaca (FCdp). Dezoito Beagles foram submetidos a teste de esforço incremental (IET). O IET foi realizado numa esteira, sendo concluído quando os cães mostraram sinais de fadiga. Os LTv GTv e FCdp foram determinados visualmente; LTp e GTp foram obtidos matematicamente por meio de função polinomial. Análise de variância (ANOVA), correlação de Pearson, regressão ordinária dos produtos mínimos e Bland-Altman foram utilizadas para avaliar a concordância entre as variáveis. Não houve diferença entre as velocidades relacionadas aos limiares (P >0.05). Houve correlação entre LTv e GTv (r = 0,91), LTv e LTp (r = 0,96), LT e GTp (r = 0,94) e a velocidade de corrida no ponto de deflexão da freqüência cardíaca (Vdp) e LT (r = 0,95 ) (P < 0,05). Foi observado viés constante entre LTv e LTp. Foi possível a determinação dos limiares de lactato e glicêmico em cães, sendo que a concordância entre LTv e FCdp indicou que a FC pode ser utilizada como método indireto para a obtenção do limiar de lactato. / The aim of this study was to compare methods to determining visually (1) lactate threshold (LTv), (2) glycemic threshold (GTv) and (3) lactate threshold by the polynomial model (LTp), (4) glucose threshold by the polynomial model (GTp), and (5) heart rate deflection point (HRdp). Eighteen Beagles underwent an incremental exercise testing (IET). IET was performed on the treadmill. The IET was completed when the dogs showed signs of fatigue. The LTv, GTv and HRdp were determined visually; LTp and GTp were obtained from the polynomial function. One-way analysis of variance, Pearson correlation, ordinary least product regressions and Bland-Altman plot were used to assess the agreement between the variables. There was no difference between the velocities corresponding to the thresholds (P >0,05). There was a correlation between LTv and GTv (r = 0.91), LTv and LTp (r = 0.96), LT and GTp (r = 0.94) and the running speed at the heart rate deflection point (Vdp) and LT (r = 0.95) (p <0.05). A constant bias was observed between LTv and LTp. It was possible to determine the lactate and glycemic thresholds in dogs, and the agreement between LTv and FCdp indicated that the HR can be used as an indirect method to obtain the lactate threshold.

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The pathophysiology of atherosclerotic cardiovascular disease (CVD) is highlighted by vascular dysfunction and low-grade vascular inflammation. Furthermore, the site-specific distribution of atherosclerosis throughout the arterial vasculature is primarily determined by local hemodynamic force. Therefore, this dissertation outlines three experiments designed to investigate the role of acute mental and physical (i.e., aerobic exercise), and vascular wall shear stress (SS) on the inflammatory aspects of atherosclerosis. Chapter 2 examines the effect of acute laboratory-induced mental stress on intracellular pro-inflammatory signaling pathways in peripheral blood mononuclear cells. Chapter 3 investigates the impact of acute laboratory-induced mental stress and maximal aerobic exercise on the concentration of soluble VCAM-1 (sVCAM-1) and CX3CL1/fractalkine (sCX3CL1) in human serum. Lastly, Chapter 4 examines the role of short- (30 min) and long-term (24 hr) low-to-negative oscillating SS (LOSS) and high laminar SS (HLSS) on the expression and secretion (i.e., cleavage) of cell-membrane VCAM-1 and CX3CL1 by human umbilical vein endothelial cell cultures in vitro. Together, these experiments provide evidence that acute psychological stress, maximal aerobic exercise, and HLSS influence vascular inflammation and adhesive properties of the vessel wall. More specifically, the results from Chapter 2 provide evidence that acute mental stress promotes the immune-cell mediated synthesis of pro-inflammatory cytokines in circulation. In addition, Chapter 3 and Chapter 4 demonstrate that the elevations in blood flow and hemodynamic force associated with maximal aerobic exercise, and unidirectional high SS may have the capacity to alter the expression of endothelial-bound cellular adhesion molecules, in part by eliciting their release from the vessel wall.

The research presented in this thesis examined the issue of the compatibility of strength and endurance training within one training regime, termed concurrent training, in recreational cyclists. Various research designs used in the previous literature resulted in inconclusive findings. The overall aim of this thesis was therefore to examine, in three systematically designed studies, the effects of various components of concurrent training regimes on cycling efficiency and recovery, and to identify some of the mechanisms that may be responsible for the interference or impedance of strength and/or endurance adaptations.