Maximal oxidative capacity during exercise is associated with muscle power output in patients with long coronavirus disease 2019 (COVID-19) syndrome. A moderation analysis.

BACKGROUND & AIMS: Long COVID syndrome (LCS) involves persistent symptoms experienced by many patients after recovering from coronavirus disease 2019 (COVID-19). We aimed to assess skeletal muscle energy metabolism, which is closely related to substrate oxidation rates during exercise, in patients with LCS compared with healthy controls. We also examined whether muscle power output mediates the relationship between COVID-19 and skeletal muscle energy metabolism. METHODS: In this cross-sectional study, we enrolled 71 patients with LCS and 63 healthy controls. We assessed clinical characteristics such as body composition, physical activity, and muscle strength. We used cardiopulmonary exercise testing to evaluate substrate oxidation rates during graded exercise. We performed statistical analyses to compare group characteristics and peak fat oxidation differences based on power output. RESULTS: The two-way analysis of covariance (ANCOVA) results, adjusted for covariates, showed that the patients with LCS had lower absolute maximal fatty acid oxidation (MFO), relative MFO/fat free mass (FFM), absolute carbohydrates oxidation (CHox), relative CHox/FFM, and oxygen uptake (V˙˙O2) at maximum fat oxidation (g min-1) than the healthy controls (P < 0.05). Moderation analysis indicated that muscle power output significantly influenced the relationship between LCS and reduced peak fat oxidation (interaction ß = -0.105 [95% confidence interval -0.174; -0.036]; P = 0.026). Therefore, when muscle power output was below 388 W, the effect of the LCS on MFO was significant (62% in our study sample P = 0.010). These findings suggest compromised mitochondrial bioenergetics and muscle function, represented by lower peak fat oxidation rates, in the patients with LCS compared with the healthy controls. CONCLUSION: The patients with LCS had lower peak fat oxidation during exercise compared with the healthy controls, potentially indicating impairment in skeletal muscle function. The relationship between peak fat oxidation and LCS appears to be mediated predominantly by muscle power output. Additional research should continue investigating LCS pathogenesis and the functional role of mitochondria.

Evaluación de los dominios de la actividad física y los componentes de la condición física en niños de 4-5 años en un centro de salud / Assessment of physical activity domains and physical fitness components in 4-5 year old children in a health centre

Introducción: la falta de actividad física y el sedentarismo en niños se asocia con una mayor adiposidad, bajo nivel de aptitud cardiovascular y riesgo de enfermedades cardiovasculares. Sin embargo, cumplir con las recomendaciones de actividad física se relaciona con mejoras en la salud mental, disminución de la ansiedad y depresión, así como adopción de hábitos saludables. Objetivos: evaluar la relación entre los diferentes dominios de la actividad física y del sedentarismo, medidos de forma objetiva, y los componentes de la condición física en niños españoles de 4 y 5 años. Población y métodos: estudio transversal dentro del proyecto “Observatorio y programa de intervención de ejercicio físico y estilos de vida en familia para niños y niñas de 4 a 5 años en Atención Primaria” (https://observatorioactividadfisica.es). La condición física se evaluó con la batería PREFIT y la cantidad e intensidad de actividad física mediante un acelerómetro tri-axial GENEActiv durante 7 días consecutivos las 24 horas del día. Resultados: la muestra evaluada fue de 70 niños (38 niños y 32 niñas) con una media (intervalo de confianza [IC] del 95%) de 4,83 años. No se observaron diferencias significativas en la condición física entre niños y niñas. Los niños realizaron una actividad física de mayor intensidad y tiempo que las niñas. Además, se encontró una fuerte relación significativa entre los componentes de la condición física y los dominios de la actividad física. Conclusiones: estos hallazgos resaltan la importancia de promover estilos de vida activos desde temprana edad y la necesidad de programas de entrenamiento estructurado para reducir el sedentarismo y mejorar la condición física en esta población (AU)

Introduction: lack of physical activity and sedentary lifestyles in children are associated with increased adiposity, low cardiovascular fitness, and risk of cardiovascular disease. On the other hand, adherence to physical activity recommendations is associated with improvements in mental health, decreased anxiety and depression, and healthier habits.Objectives: to assess the relationship between different domains of physical activity and sedentary behaviour, measured objectively, and components of physical fitness in Spanish children aged 4 and 5 years.Population and methods: cross-sectional study within the project “Observatory and intervention programme on physical exercise and lifestyles in families for children aged 4 to 5 years in primary care” (https://observatorioactividadfisica.es). Physical fitness was assessed with the PREFIT battery. To measure the amount and intensity of physical activity, participants wore a GENEActiv triaxial accelerometer on the non-dominant hand for 7 consecutive days, 24 hours a day.Results: the study sample included 70 children (38 boys and 32 girls) with a mean age of 4.83 years (95% confidence interval [CI]). There were no significant differences in physical fitness between boys and girls, but we found differences in physical activity. Boys were physically active for longer durations and with higher intensity than girls. We also found a significant and strong association between the components of physical fitness and physical activity domains in children aged 4 and 5 years.Conclusions: these findings highlight the importance of promoting active lifestyles from an early age and the need for structured training programs to reduce sedentary behaviour and improve physical fitness in this population. (AU)

Centile reference curves of the ultrasound-based characteristics of the rectus femoris muscle composition in children at 4-11 years old.

Quantitative diagnostic ultrasound has been proposed as a way to characterize muscle structure, but there is a lack of normative data for children. This study aims to establish age-specific normal ranges for echo-intensity (EI), cross-sectional area (CSA), muscular thickness (MT), and subcutaneous adipose thickness (SAT) values of the rectus femoris muscle in typically developing children. The study recruited 497 children (288 boys and 209 girls) aged 4-10.9 years (mean age 7.39 years), and muscle parameters were measured using 2D B-mode ultrasound. Percentile values and reference curves were calculated using the Lambda, Mu, and Sigma method (LMS). The results showed small variation between measurements for boys compared to girls, with the most significant difference in EI, CSA, and MT values. EI decreased with age, with the most pronounced curve in boys. SAT increased in both sexes, with a slightly higher increase in girls after the age of 9.0 years. This study provides the first age-specific reference norms for the rectus femoris muscle architecture in children, and further research is needed to validate these curves and determine their clinical utility.

Associations between basic motor competencies and physical fitness in Spanish pre-schoolers: a cross-sectional study.

BACKGROUND: Basic motor competencies (BMC) play a vital role in child development and are a primary focus of physical education. However, there is a lack of research on BMC in preschool-aged children, making this study particularly significant. The present study aims to examine the relationship between BMC and physical fitness components in Spanish preschool children. METHODS: This cross-sectional study was conducted on 101 children (n = 52 boys, average age of 4.80 years) living in Pamplona, North Spain. Components of physical fitness (handgrip strength, standing long jump, speed-agility, and cardiorespiratory fitness) were assessed using the PREFIT Battery. Overall physical fitness was computed from the four selected fitness components separately for boys and girls. Higher z-scores values in physical fitness indicate better fitness performance. To assess BMC, the MOBAK KG test battery was applied (subscales of object control and self-movement). Sex, age, and body mass index were used as main confounders. RESULTS: After adjustment for confounding factors, the BMC was positively associated with single (z-scores) components and overall physical fitness sum of z-scores (R2 from 0.178 to 0.469, all P-values < 0.05). Additional percentile scores weakened the associations, but they still remained significant (R2 from 0.146 to 0.337, all P-values < 0.05). Compared with participants in the lowest tertile, those in the highest tertile of the MOBAK KG sum score, and in both object movement and self-movement test subscales had significantly higher scores in single fitness component (z-scores or percentile) and overall physical fitness sum of z-scores (all P for trend < 0.001). CONCLUSIONS: Our results revealed that higher BMC is associated with better physical fitness in Spanish preschool children. The findings emphasize the crucial role that basic motor competence plays in promoting physical activity in preschool children.

Gamified family-based health exercise intervention to improve adherence to 24-h movement behaviors recommendations in children: "3, 2, 1 Move on Study".

BACKGROUND: Evidence suggests that movement patterns, including physical activity, sedentary behavior, and sleep duration, throughout a 24-h period, have a significant impact on biological processes and health outcomes for both young and adult populations. However, 80% of adolescents worldwide are not sufficiently active, and many children do not meet international physical activity recommendations for their age. Thus, the aim of this study is to evaluate the impact of a 12-week gamified family-based health and exercise intervention on physical fitness, basic motor competencies, mental and behavioral health, and adherence to 24-h movement guidelines in children aged 4 to 5 years old. The study will evaluate changes in sedentary levels, physical fitness, basic motor competencies, mental and behavioral disorders, adherence to the exercise program, and compliance with physical activity recommendations. In addition, the aim of this protocol is to describe the scientific rationale in detail and to provide information about the study procedures. METHODS/DESIGN: A total of 80 children, aged 4 to 5 years old, will be randomly assigned in a 1:1 ratio to one of two groups: the exercise group and the routine care group. The exercise group will undergo a 12-week exercise intervention, followed by a 12-week follow-up period. On the other hand, the routine care group will undergo a 12-week period of routine care, followed by a 12-week follow-up control period. The exercise program will be implemented in a family setting and facilitated through a gamified web platform with online supervision, with the hypothesis that it will have a positive impact on physical fitness, anthropometric measures, basic motor competencies, and adherence to 24-h movement guidelines. DISCUSSION: The results of this study will provide valuable insights into the impact of a gamified, family-oriented health and exercise program on various aspects of health, including physical fitness, basic motor competencies, mental and behavioral well-being, and adherence to 24-h movement guidelines. The findings will contribute to closing the gap in current knowledge on the effectiveness of these types of interventions for children and their parents. These findings will also contribute to  the development of future guidelines for promoting physical activity in children who do not meet the World Health Organization's recommended levels. An online "3, 2, 1 Move on Study" is believed to increase accessibility, promoting health equity, and reducing economic barriers for all children and their families across diverse social groups. TRIAL REGISTRATION: Trial registration: NCT05741879 . Registered February 14, 2023, Version 1.

Reduced muscle strength in patients with long-COVID-19 syndrome is mediated by limb muscle mass.

Understanding the impact of COVID-19 on muscle strength may help to elucidate the organ systems that contribute to acute and chronic COVID-19 sequelae. We questioned whether patients with postdischarge symptoms after COVID-19 had compromised muscle strength compared with a control group, and if this potential relationship was mediated by the lower appendicular lean mass index (ALMI). A total of 99 patients with long-COVID-19 and 97 control participants were screened. Maximal grip strength was assessed with a TKK 5101 digital dynamometer, and leg extension 1RM was measured using EGYM Smart Strength machines. Body composition (fat mass percentage, lean mass, visceral fat, and appendicular lean mass index) was determined using a whole body dual-energy X-ray densitometer. Results showed that grip strength and leg extension strength were significantly higher in controls than in COVID-19 survivors (mean [SD], 32.82 [10.01] vs. 26.94 [10.33] kg; difference, 5.87 kg; P < 0.001) and (mean [SD], 93.98 [33.73] vs. 71.59 [33.70] kg; difference, 22.38 kg; P < 0.001), respectively). The relationship between long-COVID syndrome and grip/leg strength levels was partly mediated by ALMI, which explained 52% of the association for grip strength and 39% for leg extension. Our findings provide novel insights into the mechanisms underlying the relationship between long-COVID syndrome and grip/leg strength levels, supporting the negative effects of long-COVID syndrome on muscle function.NEW & NOTEWORTHY The causes of post-COVID-19 syndrome are uncertain. Limb muscle wasting common to patients with COVID-19 limits daily activities and exercise. In this cross-sectional study, we found that patients with long-COVID-19 syndrome had significantly lower absolute and relative muscle strength measurements than control participants. Interestingly, we identified that these relationships were mostly mediated by limb muscle mass. Our data thus suggest that the evident reduced upper and lower muscle mass is a putative cause of-or contributor to-the functional limitation of patients with long-COVID-19 syndrome.

Resistance training and clinical status in patients with postdischarge symptoms after COVID-19: protocol for a randomized controlled crossover trial "The EXER-COVID Crossover Study".

BACKGROUND: Physical exercise induces a coordinated response of multiple organ systems, including the immune system. In fact, it has been proposed that physical exercise may modulate the immune system. However, the potential effect of an exercise program on COVID-19 survivors has not been investigated. Thus, the aim of this study is to evaluate the modifications in immunological parameters, physical condition, inflammatory profile, and perceived persistent symptoms after 6 weeks of supervised resistance training (RT), in addition to the standard care on the clinical status of patients with persistent COVID-19 symptoms. The objective of this protocol is to describe the scientific rationale in detail and to provide information about the study procedures. METHODS/DESIGN: A total of 100 patients with postdischarge symptoms after COVID-19 will be randomly allocated into either a group receiving standard care (control group) or a group performing a multicomponent exercise program two times a week over a period of 6 weeks. The main hypothesis is that a 6-week multicomponent exercise program (EXER-COVID Crossover Study) will improve the immunological and inflammatory profile, physical condition, and persistent perceived symptoms (fatigue/tiredness, musculoskeletal pain, and shortness of breath) in patients with postdischarge symptoms after COVID-19. DISCUSSION: Our results will provide insights into the effects of a multicomponent exercise program on immunological parameters, physical condition, inflammatory profile, and persistent perceived symptoms in patients with postdischarge symptoms after COVID-19. Information obtained by this study will inform future guidelines on the exercise training rehabilitation of patients with postdischarge symptoms after COVID-19. TRIAL REGISTRATION: NCT04797871 , Version 2. Registered on March 15, 2021.

Relationship between parents' and children's objectively assessed movement behaviours prior to and during the COVID-19 pandemic.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic could have provoked undesirable harmful effects on movement behaviours among children. OBJECTIVE: To compare levels of physical activity (PA), sedentary behaviour (SB), and sleep time in children prior to and during the COVID-19 pandemic (after the lockdown) and to determine the association between changes in moderate-to-vigorous PA (MVPA), total PA (TPA), SB, and sleep time between mothers and fathers with their children. METHODS: A total of 110 children (aged 4-7 years) and their parents (63 mothers and 52 fathers) wore GENEActiv accelerometers for 6 days (4 weekdays and 2 weekend days) prior to the pandemic and 1 year into the pandemic to assess SB, MVPA, TPA, and sleep time. RESULTS: Children performed more MVPA on weekdays (p = 0.002), had higher SB (p = 0.001), and slept fewer hours during the pandemic than before (p < 0.001). Likewise, children performed more weekend day MVPA and TPA (p < 0.001) during the pandemic, and slept less than prior to the pandemic (p = 0.002). On weekdays, an increase in mother's MVPA and TPA (categorized as tertiles) was associated with higher increased on MVPA (p = 0.030) and TPA in their children (p = 0.023), respectively. On weekends, an increase in mother's MVPA was also associated with higher increases in MVPA (p = 0.011) in their children. CONCLUSION: During the pandemic, children got more MVPA, more SB, and slept fewer hours than before. Changes in PA seem to be associated with mother's behaviours, especially during weekdays.

Associations between physical fitness components with muscle ultrasound parameters in prepuberal children.

BACKGROUND/OBJECTIVES: Muscle ultrasound is a convenient technique to visualize normal and pathological muscle tissue as it is non-invasive and real-time. This technique is related to several physical performance parameters and body composition components in adults; however, this relationship remains unexplored in early aged. We aimed to evaluate the association between physical fitness components with muscle ultrasound parameters in prepuberal children. METHODS: A sample of 282 prepuberal children aged 5-9 years (144 boys) participated in the study. A trained sonographer obtained six B-mode images from femoral rectus for muscle thickness, subcutaneous adipose tissue (SAT) and area of the muscle of interest, were captured, and muscle ultrasound parameters (echo-intensity: EI uncorrected, EI correct equations) and intramuscular adipose tissue (IMAT) were extracted. Lean muscle tissue has low EI, whereas intramuscular fat and connective tissue have high EI. Physical fitness components (cardiorespiratory fitness, upper and lower muscle strength, speed-agility, and overall fitness levels) were also evaluated. Children were categorized as fit or unfit for each specific fitness test. RESULTS: After adjustment for sex and age, higher physical fitness components and overall fitness (z-score) levels were negatively associated with EI, IMAT, and SAT (cardiorespiratory fitness ß range = -0.264 to -0.298; upper-muscular strength ß range = -0.389 to -0.457; and lower-muscular strength ß range = -0.202 to -0.279; and speed-agility ß range = -0.257 to -0.302). Children categorized as fit according to four physical fitness components had lower EI uncorrected, EI correct equation 1-2, IMAT, and SAT than unfit children for each respective tests (all Ps < 0.001). CONCLUSION: Physical fitness components are inversely associated with EI, IMAT, SAT after adjusting for potential confounders, including sex and age, in prepuberal children. The present study strengthens the idea that muscle and adiposity parameters is affected by physical fitness even from early childhood.