Correlates of Toddlers' Physical Activity Levels and Sedentary Behavior During Unstructured Outdoor Play in Early Childhood Education and Daycare Settings.

Despite recent research showing that early childhood education and daycare settings (ECEC) have an important role in promoting toddlers' physical activity (PA), crucial information gaps remain regarding toddlers' PA and sedentary behavior (SB) in these outdoor settings. We aimed in this study to: (a) analyze PA patterns and SB during unstructured outdoor play time in preschool and daycare environments using accelerometry and systematic observation; (b) provide concurrent accelerometry and observational data to help validate the Observational System for Recording Physical Activity in Children-Preschool Version (OSRAC-P); and (c) examine individual, social and environmental correlates of PA and SB during toddlers' unstructured outdoor play time. We found that: (a) toddlers displayed high amounts of PA with no sex, BMI, and/or age differences in PA and SB levels,; (b) environmental variables (e.g., fixed equipment and playground density) were not associated with PA levels or SB intensity; (c) the OSRAC-P was a reliable and valid means of observing and analyzing toddlers' PA patterns during unstructured outdoor play time; and (e) different social patterns between boys and girls did not impact PA levels or patterns. Combining different measurement methods permitted an improved understanding of unstructured outdoor play in preschool and daycare settings.

A descriptive-comparative study to analyse physical activity levels and patterns during structured movement sessions in early childhood education: special focus on the role of teachers / Estudio descriptivo-comparativo para analizar los niveles y patrones de actividad física durante sesiones estructuradas de movimiento en Educación Infantil: especial atención al papel del profesorado

Because teacher behaviour and children’s gender are correlates of young children’s physical activity during structured movement sessions in early years, teachers should develop effective teaching strategies to promote physical activity, with a special focus on girls. Following a descriptive-comparative study, the aims of this research were: (a) to analyse the physical activity levels and patterns during two structured movement sessions under the framework of experiential psychomotricity using accelerometry and direct observation methods; (b) to evaluate the impact of a formalised short intervention that focuses on physical activity during structured movement sessions; and (c) to explore young children’s experience of movement during both sessions using drawings. Our major findings were as follows: (a) the intervention had a positive impact on the physical activity levels and patterns in young girls during a structured movement session; (b) the teacher’s active role during sessions could have a positive impact on the physical activity levels favouring more diverse group compositions, especially with the girls; (c) the graphic representation act as a source of knowledge that help both the teacher and the child to make sense of their movement experience. Our results are useful for understanding how the teacher’s role during experiential psychomotricity could promote physical activity in young children. (AU)

Dado que el comportamiento del profesorado y el género del estudiantado son correlatos de la actividad física durante las sesiones de movimiento estructurado en la primera infancia, los profesores deben desarrollar estrategias de enseñanza eficaces para promover la actividad física, con especial atención a las niñas. Siguiendo un diseño descriptivo-comparativo, los objetivos de este estudio fueron: (a) analizar los niveles y patrones de actividad física durante dos sesiones de movimiento estructurado bajo el marco de la psicomotricidad experiencial utilizando métodos de acelerometría y observación directa; (b) evaluar el impacto de una intervención corta formalizada que se centra en el análisis de la actividad física durante las sesiones de movimiento estructurado; y (c) explorar a través del dibujo infantil, la experiencia de movimiento de los niñas y niños durante ambas sesiones. Nuestros principales resultados fueron los siguientes: (a) la intervención tuvo un impacto positivo en los niveles y patrones de actividad física en las niñas durante una sesión de movimiento estructurado; (b) el papel activo de la maestra durante las sesiones podría tener un impacto positivo en los niveles de actividad física favoreciendo composiciones de grupo más diversas, especialmente con las niñas; (c) la representación gráfica actúa como una fuente de conocimiento que ayuda tanto a la maestra como a las niñas y niños a dar sentido a sus experiencias de movimiento. Nuestros resultados son útiles para comprender cómo el papel del profesorado durante la psicomotricidad experiencial puede promover la actividad física en la primera infancia. (AU)

Role of Spanish Toddlers' Education and Care Institutions in Achieving Physical Activity Recommendations in the COVID-19 Era: A Cross-Sectional Study.

To our knowledge, there are no published studies that describe the physical activity (PA) levels and objectively measure them through accelerometry in toddlers (2-3 years old) attending early childhood education and care (ECEC) institutions during the COVID-19 pandemic. The aims of this study were two-fold: (a) to analyse toddlers' PA levels and sedentary behaviour (SB) during school hours in ECEC institutions, as well as the rate of adherence to specific recommendations on total PA (TPA) and moderate-vigorous PA (MVPA); and (b) to evaluate the characteristics correlates (age, gender, and body mass index -BMI) of young children and the school environment on toddlers' TPA, light PA (LPA), MVPA, and SB during school hours in ECEC institutions. PA was evaluated with ActiGraph accelerometers. The main findings were that: (a) toddlers engaged in very high amounts of TPA and MVPA during ECEC hours; (b) girls and boys displayed similar levels of LPA, TPA, and SB, while girls had lower levels of MVPA, compared to boys, and younger toddlers were less active than older ones; (c) BMI was not associated with PA of any intensity or SB; (d) playground and classroom density were not associated with higher levels of PA of any intensity, though classroom density was associated with SB. These ECEC institutions provide and challenge the new COVID-19 scenario, as well as supportive environments for toddlers' PA.

Relationship Between the Physical Environment and Physical Activity Levels in Preschool Children: A Systematic Review.

PURPOSE OF REVIEW: The aim of this study was to understand the influence of the physical environment on the physical activity (PA) behavior of preschool children (aged 2 to 6 years), in order to provide an overview of these influences from the perspective of the ecological model. RECENT FINDINGS: PA is of great importance for the prevention of obesity and cardiovascular diseases since childhood. The physical environment has a direct relationship with the different domains, where people can spend their time being physically active. Nonetheless, despite the importance of the physical environment to engagement in PA, very few reviews have focused on this relationship in the context of the growing problem of physical inactivity among preschool children. Studies that had analyzed the school domain had found that greater availability of a wider variety of portable play equipment, presence of certain fixed playground equipment, and presence of open spaces had favored PA levels. Furthermore, different studies had shown that the natural environment and the presence of hills were important for children's PA. Thus, despite the associations with PA we were able to identify in this review, new studies will still be needed to link the physical environment with PA levels, especially regarding transportation and leisure time. In conclusion, promoting studies on this subject from an early age will allow us to obtain information that could allow the adaptation, design, and construction of healthier homes, neighborhoods, and schools that promote children's health.

Physical Activity and Motor Competence in Preschool Children.

Longitudinal evidence has demonstrated that engagement in physical activity (PA) and the development of motor competence (MC) have numerous tangible health and developmental benefits [...].

The Role of Preschool Hours in Achieving Physical Activity Recommendations for Preschoolers.

Research on physical activity (PA) in different educational settings could elucidate which interventions promote a healthy school lifestyle in early childhood education (ECE). The aims of this study were: (a) to analyse the PA levels of preschoolers during school hours, as well as the rate of compliance with specific recommendations on total PA (TPA) and moderate-vigorous PA (MVPA); (b) to examine the role of structured movement sessions and recess time in the MVPA levels during school hours; (c) to evaluate the sociodemographic correlates of preschoolers and the school environment on MVPA behaviour during school hours. PA was evaluated with Actigraph accelerometers. Our main findings were that: (a) preschoolers engaged in very little TPA and MVPA during school hours; (b) children showed significantly higher MVPA levels on days with versus without structured movement sessions, and the contribution of the structured sessions to MVPA was significantly higher than that of recess time; (c) gender and age were associated with PA, and a high density of young children on the playground was associated with high levels of vigorous PA, whereas in the classroom, high density was associated with more sedentary behaviour. Structured PA could reduce the gap in achieving international recommendations.

Importancia de la música para y en la formación del fisioterapeuta / Importance of music for and in the training of the physiotherapist / Importância da música para e no treinamento do fisioterapeuta

Resumen Introducción: son muchos los especialistas de Ciencias de la Salud que han demostrado lo interesante y significativo de utilizar la Música en sus tratamientos terapéuticos. No obstante, en España, solo una universidad pública cuenta con formación musical para capacitarlos en su utilización. Objetivo: esta investigación intentó demostrar la necesidad de formación musical desde el Grado de Fisioterapia, a través de propuestas de Movimiento con Música desde la perspectiva dalcroziana. Materiales y métodos: se realizaron una serie de prácticas de concienciación corporal con Música, atendiendo al trabajo de distintos elementos musicales y partiendo de las propuestas de Jaques-Dalcroze; que terminaron concretándose después en role-playing extrapolables a sus sesiones de prácticas fisioterapéuticas. Se distribuyeron a lo largo de cuatro semanas de trabajo, a razón de tres horas semanales de trabajo, que finalizaban con el feedback aportado por las propuestas prácticas adaptadas a sus futuras sesiones de Fisioterapia. Resultados: los datos mostraron la importancia que el fisioterapeuta concede al estímulo auditivo musical como motivador y no solo como relajante. Los resultados centrados en la interiorización-corporización, por parte del fisioterapeuta, fueron significativos porque se produjo un aumento de la concienciación acerca del propio movimiento corporal; hecho que, posibilitó una incorporación de sus propias propuestas durante el período de Prácticum. Conclusiones: Se pudo comprobar cómo la implementación de una materia musical en el Grado de Fisioterapia podrá contribuir al desarrollo de las competencias genéricas, específicas y transversales vinculadas a dicha titulación. La Universidad de Valencia se convirtió, así, en pionera al ofertar Musicoterapia a sus estudiantes.

Abstract Introduction: there are many specialists in Health Sciences who have shown how interesting and meaningful to use music in their therapeutic treatments. However, in Spain, only one public university has musical training to train the in its use. Objective: this research attempted to demonstrate the need for musical training from the Degree of Physiotherapy, through proposals of Movement with Music from the Jaques-Dalcrozian perspective. Materials and methods: a series of body awareness practices with Music was carried out, based on the works of different musical elements and based on Dalcroze's proposals; that ended up being concreted later in role-playing extrapolables to their sessions of physiotherapeutic practices. They were di stributed over four weeks of work, at the rate of three hours per week of work, which ended with the feedback provided by the practical proposals adapted to their future physiotherapy sessions. Results: the data showed the importance that the physiotherapist gives to the musical auditory stimulus as motivator and not only as relaxing. The results focused on the internationalization-embodiment by the physiotherapist, were significant because there was an increase in awareness about one's body movement; fact that, it made possible an incorporation of its own proposals during the Practicum period. Conclusions. It was possible to verify how the implementation of a musical subject in the Degree of Physiotherapy can contribute to the development of the generic, specific and transversal competences linked to said degree. The University of Valencia thus became a pioneer in offering Music Therapy to its students.

Resumo Introdução: muitos especialistas em ciências da saúde mostraram como é interessante e significativo usar a música em seus tratamentos terapêuticos. No entanto, na Espanha, apenas uma universidade pública possui treinamento musical para treiná-las em seu uso. Objetivo: esta pesquisa procurou demonstrar a necessidade de treinamento musical a partir do Grau de Fisioterapia, através de propostas de Movimento com Música na perspectiva dalroziana. Materiais e métodos: realizou-se uma série de práticas de consciência corporal com a música, atendendo ao trabalho de diferentes elementos musicais e com base nas propostas de Jaques-Dalcroze; que acabaram-se concretizando na encenação extrapolada para as sessões de prática fisioterapêutica. Eles foram distribuídos ao longo de quatro semanas de trabalho, na proporção de três horas por semana de trabalho, terminando com o feedback fornecido pelas propostas práticas adaptadas às suas futuras sessões de Fisioterapia. Resultados: os dados mostraram a importância que o fisioterapeuta atribui ao estímulo auditivo musical como motivador e não apenas como relaxante. Os resultados focados na incorporação-incorporação, pelo fisioterapeuta, foram significativos porque houve um aumento na consciência do próprio movimento corporal; fato que possibilitou a incorporação de suas próprias propostas durante o período de estágio. Conclusões: foi possível verificar como a implementação de uma disciplina musical no Grau de Fisioterapia poderia contribuir para o desenvolvimento de competências genéricas, específicas e transversais vinculadas a esse diploma. A Universidade de Valência tornou-se assim pioneira em oferecer Musicoterapia aos seus alunos.

Neighborhood Built Environment and Socioeconomic Status are Associated with Active Commuting and Sedentary Behavior, but not with Leisure-Time Physical Activity, in University Students.

The role of neighborhood characteristics in promoting physical activity and sedentary behaviors (SB) has not been extensively studied in university students. The study purpose was to analyze the associations of neighborhood built environment and neighborhood socioeconomic status (SES) with active commuting, leisure-time physical activity (LTPA), and SB among university students. This is a cross-sectional study of 308 undergraduate students from two urban universities in Valencia, Spain. Participants' residential neighborhoods were classified according to walkability and SES levels. Walkability was defined as an index of three built environment attributes (i.e., residential density, land-use mix, and street connectivity) based on geographical information system data. Active commuting to and from university (ACU), active commuting in the neighborhood, LTPA, and SB were evaluated through a questionnaire. Mixed model regression analyses were performed. There were no significant SES-walkability interactions for any of the outcomes analyzed. However, university students living in more walkable areas reported two more ACU trips per week compared to those living in less walkable neighborhoods (p < 0.01). University students living in lower-SES neighborhoods reported more ACU trips per week than those living in higher-SES neighborhoods (p < 0.05). Regarding LTPA, there were no significant SES or walkability main effects. Neighborhood SES was negatively related to active commuting in the neighborhood and to time spent in SB (all p < 0.05). Participants living in lower-SES neighborhoods reported more active commuting per week and had the highest average minutes spent in SB. This study highlights the relevance of assessing university's residential environment when active transportation and SB are analyzed.

Pharmacological properties of physical exercise in the elderly.

Scientific evidence links physical activity to several benefits. Recently, we proposed the idea that exercise can be regarded as a drug. As with many drugs, dosage is of great importance. However, to issue a public recommendation of physical activity in aging is not an easy task. Exercise in the elderly needs to be carefully tailored and individualized with the specific objectives of the person or group in mind. The beneficial effects of exercise in two of the main age-related diseases, sarcopenia and Alzheimer's Disease, are dealt with at the beginning of this report. Subsequently, dosage of exercise and the molecular signaling pathways involved in its adaptations are discussed. Exercise and aging are associated with oxidative stress so the paradox arises, and is discussed, as to whether exercise would be advisable for the aged population from an oxidative stress point of view. Two of the main redox-sensitive signaling pathways altered in old skeletal muscle during exercise, NF-κB and PGC-1α, are also reviewed. The last section of the manuscript is devoted to the age-associated diseases in which exercise is contraindicated. Finally, we address the option of applying exercise mimetics as an alternative for disabled old people. The overall denouement is that exercise is so beneficial that it should be deemed a drug both for young and old populations. If old adults adopted a more active lifestyle, there would be a significant delay in frailty and dependency with clear benefits to individual well-being and to the public's health.

Altitude exposure in sports: the Athlete Biological Passport standpoint.

The Athlete Biological Passport (ABP) is principally founded on monitoring an athlete's biological variables over time, to identify abnormal biases on a longitudinal basis. Several factors are known to influence the results of these markers. However, the manner in which the altitude factor is taken into account still needs to be standardized. Causal relationships between haematological variables should be correctly integrated into ABP software. In particular, modifications of haematological parameters during and after exposure to different altitudes/hypoxic protocols need to be properly included within detection models.

PPARgamma agonist pioglitazone does not enhance performance in mice.

Peroxisome-proliferator-activated receptor (PPAR) delta and adenosine monophosphate (AMP)-activated protein kinases (AMPKs) regulate the metabolic and contractile characteristics of myofibres. PPAR proteins are nuclear receptors that function as transcription factors and regulate the expression of multiple genes. AMPK has been described as a master metabolic regulator which also controls gene expression through the direct phosphorylation of some nuclear proteins. Since it was discovered that both PPARdelta agonists (GW1516) and AMPK activators (5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside, known as AICAR) are very effective performance-enhancing substances in sedentary mice, the World Anti-doping Agency (WADA) included AICAR and GW1516 in the prohibited list of substances as metabolic modulators in the class 'Hormone and metabolic modulators'. Thiazolidinediones are PPARgamma agonists that can induce similar biological effects to those of PPARdelta and PPARdelta-AMPK agonists. Thus in this study, the effects of pioglitazone on mitochondrial biogenesis and performance were evaluated. Blood glucose levels and the protein expression of the intermediates involved in the mitochondrial biogenesis pathway and the citrate synthase activity were determined in both gastrocnemius and soleus muscles. Maximal aerobic velocity (MAV), endurance capacity, and grip strength before and after the training period were also determined. The MAV endurance capacity and grip strength of trained animals significantly increased. We found that the peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) and the nuclear respiratory factor-1 (NRF-1) protein content and citrate synthase activity significantly increased in the soleus muscle of trained animals. No effect of treatment was found. Therefore in our study, pioglitazone administration did not affect mitochondrial biogenesis signaling pathway.

Blood rheology effect of submaximal exercise on young subjects.

Nowadays cardiac and metabolic diseases are a matter of concern. Exercise is a valid treatment and method of prevention for not only adults, but also young subjects. Physical activity causes transient blood rheology impairment in adults. However little is known about the effects of exercise on blood flow characteristics in young subjects. The aim of the study was to assess the effects of a light aerobic exercise session on blood rheology in young subjects. Ten young subjects (aged 12-16 years) performed 1 hour of submaximal aerobic exercise (70% HRmax). Blood samples were drawn just before and after exercise. We determined blood and plasma viscosity, fibrinogen, erythrocyte deformability and aggregability. No changes in blood viscosity (p > 0.05), erythrocyte aggregation (p > 0.05) and fibrinogen (p > 0.05) were observed. Hematocrit (p = 0.025) and plasma viscosity (p = 0.018) rose with exercise, while erythrocyte elongation index lowered (p < 0.001). Plasma volume slightly reduced which may explain the lack of changes in blood viscosity. The results of the present study indicate a similar hemorheological response to submaximal exercise in both young people and adults.

Effects of acute exercise and xanthine oxidase inhibition on novel cardiovascular biomarkers.

Several sports have been associated with a postexercise increase of cardiac, liver, and skeletal muscle biomarkers of injury. Exhaustive or acute physical exercise causes an increased generation of reactive oxygen species, resulting in cellular injury. Thus, exercise and training may trigger pathophysiological changes in serum concentrations of a variety of biomarkers. In this study, we aimed to evaluate the variation of novel biomarkers of stress and cardiovascular disease such as copeptin, midregional part of proadrenomedullin (MR-proADM), growth differentiation factor 15 (GDF15), soluble vascular endothelial growth factor receptor, and placental growth factor along with uric acid before and after acute high-intensity exercise and allopurinol administration. We also assessed whether allopurinol administration may affect the circulating levels of these biomarkers by inhibition of XO activity. This is a double-blind, placebo-controlled study in which 12 professional football players were divided into 2 experimental groups. An oral dose of 300 mg of allopurinol was administered to one group of six participants 4 hours before a match of the Spanish Football League, whereas the other 6 participants received placebo (cellulose). Venous blood samples were obtained before the match (baseline) and twelve hours afterwards (post-match). Serum MR-proADM levels increased significantly in the placebo group, whereas serum GDF15 levels increased significantly in both the placebo and allopurinol group after the match. No differences in the other parameters tested were found after the match in any experimental group. The trend toward postexercise increase of serum MR-proADM and GDF15 levels shows that the metabolism of these proteins is clearly imbalanced after exercise, which thereby represents a potential source of biological variability in their clinical assessment.

Vitamin C supplementation does not improve hypoxia-induced erythropoiesis.

Hypoxia induces reactive oxygen species production. Supplements with antioxidant mixtures can compensate for the decline in red cell membrane stability following intermittent hypobaric hypoxia by decreasing protein and lipid oxidation. We aimed to determine whether supplementation with vitamin C is implicated in the regulation of erythropoiesis and in the oxygen-carrying capacity of the blood, and also whether antioxidant supplementation prevents the oxidative stress associated to intermittent hypoxia. Twenty-four male Wistar rats were randomly divided into four experimental groups: normoxia control (n=6), normoxia + vitamin C (n=6), hypoxia control (12 h pO(2) 12%/12 h pO(2) 21%) (n=6), and hypoxia + vitamin C (n=6). Animals were supplemented with vitamin C at a dose of 250 mg·kg(-1)·day(-1) for 21 days. Red blood cell count, hemoglobin, hematocrit, reticulocytes, erythropoietin, and oxidative stress parameters such as malondialdehyde and protein oxidation in plasma were analyzed at two different time points: basal sample (day zero) and final sample (day 21). Similar RBC, Hb, Hct, and Epo increments were observed in both hypoxic groups regardless of the vitamin C supplementation. There was no change on MDA levels after intermittent hypoxic exposure in any experimental group. However, we found an increase in plasma protein oxidation in both hypoxic groups. Vitamin C does not affect erythropoiesis and protein oxidation in rats submitted to intermittent hypoxic exposure.

Three weeks of erythropoietin treatment hampers skeletal muscle mitochondrial biogenesis in rats

The blood O(2)-carrying capacity is maintained by the O(2)-regulated production of erythropoietin (Epo), which stimulates the proliferation and survival of red blood cell progenitors. Epo has been thought to act exclusively on erythroid progenitor cells. However, recent studies have identified the erythropoietin receptor (EpoR) in other cells, such as neurons, astrocytes, microglia, heart, cancer cell lines, and skeletal muscle provides evidence for a potential role of Epo in other tissues. In this study we aimed to determine the effect of recombinant human erythropoietin (rHuEpo) on skeletal muscle adaptations such as mitochondrial biogenesis, myogenesis, and angiogenesis in different muscle fibre types. Fourteen male Wistar rats were randomly divided into two experimental groups, and saline or rHuEpo (300 IU) was administered subcutaneously three times a week for 3 weeks. We evaluated the protein expression of intermediates involved in the mitochondrial biogenesis cascade, the myogenic cascade, and in angiogenesis in the oxidative soleus muscle and in the glycolytic gastrocnemius muscle. Contrary to our expectations, rHuEpo significantly hampered the mitochondrial biogenesis pathway in gastrocnemius muscle (PGC-1Alpha, mTFA and cytochrome c). We did not find any effect of the treatment on cellular signals of myogenesis (MyoD and Myf5) or angiogenesis (VEGF) in either soleus or gastrocnemius muscles. Finally, we found no significant effect on the maximal aerobic velocity at the end of the experiment in the rHuEpo-treated animals. Our findings suggest that 3 weeks of rHuEpo treatment, which generates an increase of oxygen carrying capacity, can affect mitochondrial biogenesis in a muscle fibre-specific dependent manner

Inhibition of xanthine oxidase by allopurinol prevents skeletal muscle atrophy: role of p38 MAPKinase and E3 ubiquitin ligases.

Alterations in muscle play an important role in common diseases and conditions. Reactive oxygen species (ROS) are generated during hindlimb unloading due, at least in part, to the activation of xanthine oxidase (XO). The major aim of this study was to determine the mechanism by which XO activation causes unloading-induced muscle atrophy in rats, and its possible prevention by allopurinol, a well-known inhibitor of this enzyme. For this purpose we studied one of the main redox sensitive signalling cascades involved in skeletal muscle atrophy i.e. p38 MAPKinase, and the expression of two well known muscle specific E3 ubiquitin ligases involved in proteolysis, the Muscle atrophy F-Box (MAFbx; also known as atrogin-1) and Muscle RING (Really Interesting New Gene) Finger-1 (MuRF-1). We found that hindlimb unloading induced a significant increase in XO activity and in the protein expression of the antioxidant enzymes CuZnSOD and Catalase in skeletal muscle. The most relevant new fact reported in this paper is that inhibition of XO with allopurinol, a drug widely used in clinical practice, prevents soleus muscle atrophy by ~20% after hindlimb unloading. This was associated with the inhibition of the p38 MAPK-MAFbx pathway. Our data suggest that XO was involved in the loss of muscle mass via the activation of the p38MAPK-MAFbx pathway in unloaded muscle atrophy. Thus, allopurinol may have clinical benefits to combat skeletal muscle atrophy in bedridden, astronauts, sarcopenic, and cachexic patients.

Three weeks of erythropoietin treatment hampers skeletal muscle mitochondrial biogenesis in rats.

The blood O(2)-carrying capacity is maintained by the O(2)-regulated production of erythropoietin (Epo), which stimulates the proliferation and survival of red blood cell progenitors. Epo has been thought to act exclusively on erythroid progenitor cells. However, recent studies have identified the erythropoietin receptor (EpoR) in other cells, such as neurons, astrocytes, microglia, heart, cancer cell lines, and skeletal muscle provides evidence for a potential role of Epo in other tissues. In this study we aimed to determine the effect of recombinant human erythropoietin (rHuEpo) on skeletal muscle adaptations such as mitochondrial biogenesis, myogenesis, and angiogenesis in different muscle fibre types. Fourteen male Wistar rats were randomly divided into two experimental groups, and saline or rHuEpo (300 IU) was administered subcutaneously three times a week for 3 weeks. We evaluated the protein expression of intermediates involved in the mitochondrial biogenesis cascade, the myogenic cascade, and in angiogenesis in the oxidative soleus muscle and in the glycolytic gastrocnemius muscle. Contrary to our expectations, rHuEpo significantly hampered the mitochondrial biogenesis pathway in gastrocnemius muscle (PGC-1α, mTFA and cytochrome c). We did not find any effect of the treatment on cellular signals of myogenesis (MyoD and Myf5) or angiogenesis (VEGF) in either soleus or gastrocnemius muscles. Finally, we found no significant effect on the maximal aerobic velocity at the end of the experiment in the rHuEpo-treated animals. Our findings suggest that 3 weeks of rHuEpo treatment, which generates an increase of oxygen carrying capacity, can affect mitochondrial biogenesis in a muscle fibre-specific dependent manner.

Age associated low mitochondrial biogenesis may be explained by lack of response of PGC-1α to exercise training.

Low mitochondriogenesis is critical to explain loss of muscle function in aging and in the development of frailty. The aim of this work was to explain the mechanism by which mitochondriogenesis is decreased in aging and to determine to which extent it may be prevented by exercise training. We used aged rats and compared them with peroxisome proliferator-activated receptor-γ coactivator-1α deleted mice (PGC-1α KO). PGC-1α KO mice showed a significant decrease in the mitochondriogenic pathway in muscle. In aged rats, we found a loss of exercise-induced expression of PGC-1α, nuclear respiratory factor-1 (NRF-1), and of cytochrome C. Thus muscle mitochondriogenesis, which is activated by exercise training in young animals, is not in aged or PGC-1α KO ones. Other stimuli to increase PGC-1α synthesis apart from exercise training, namely cold induction or thyroid hormone treatment, were effective in young rats but not in aged ones. To sum up, the low mitochondrial biogenesis associated with aging may be due to the lack of response of PGC-1α to different stimuli. Aged rats behave as PGC-1α KO mice. Results reported here highlight the role of PGC-1α in the loss of mitochondriogenesis associated with aging and point to this important transcriptional coactivator as a target for pharmacological interventions to prevent age-associated sarcopenia.