Eva-Maria Riso

Review on aging, unloading and reloading: Changes in skeletal muscle quantity and quality

Aging and muscle unloading are associated with a decline in muscle mass, structure, force and changes in the mechanical properties of skeletal muscle. There is a perception that reloading restores muscle architecture and function but differences in the regeneration capacity of intra- and extra-cellular compartments, age dependent susceptibility to muscle damage, particularly in the contractile machinery, make it difficult to attribute the main role of the above mentioned components. This review briefly summarizes studies that examine aging skeletal muscle during unloading and reloading. The article highlights changes in muscle mass, structure, extra-cellular matrix (ECM) components, strength, locomotion, adaptability to exercise, peculiarities of protein metabolism, susceptibility to glucocorticoids and recovery of muscle from injury.

Different Methods Yielded Two-Fold Difference in Compliance with Physical Activity Guidelines on School Days.

Introduction The aim was to compare the average and the days method in exploring the compliance of children with physical activity guidelines and describe their physical activity patterns in different school day segments. Methods Physical activity was objectively measured in 472 children aged 6–13 for one school week. Children were compliant when fulfilling PA recommendations 1) on average over all measured days (average method) or 2) on at least four measured days (days method). To explore the difference in moderate to vigorous physical activity (MVPA) minutes between compliant and non-complaint children (using both the average and days method) in various day segments, linear mixed models was used. Results Compliance with physical activity guidelines was significantly higher with the average compared to the days method (51.7% and 23.7%, respectively). In segmented-day analysis, compliant children accrued more MVPA minutes in all day segments, especially during after-school. Gender differences appeared only during the in-school segments, where girls spent less time in MVPA (average method: -4.39 min, 95% CI = -5.36,-3.42, days method: -4.45 min, 95%CI = -5.46,-3.44). Older children accrued more MVPA minutes during physical education classes, but less during breaks, compared to younger children. Conclusions The used methods yielded remarkably different prevalence estimates for compliance to physical activity recommendations. To ensure comparability between studies, interventions and reports, there is a need for internationally agreed operationalization and assessment methods of physical activity guidelines. As non-compliant children had lower MVPA during all day segments, greater efforts should be made to provide physical activity opportunities both during and after school.

Relationship between extracellular matrix, contractile apparatus, muscle mass and strength in case of glucocorticoid myopathy

The purpose of this study was to evaluate the effect of dexamethasone on the contractile apparatus and extracellular matrix (ECM) components of slow-twitch (ST) soleus (Sol) and fast-twitch (FT) extensor digitorum longus (EDL) muscle. The specific aim was to assess the development of glucocorticoid-induced myopathy on the level of contractile apparatus and ECM, paying attention to the expression of fibrillar forming collagen types I and III and nonfibrillar type IV collagen expression in extracellular compartment of muscle. Degradation of myofibrillar proteins increased from 2.62+/-0.28 to 5.58+/-0.49% per day during glucocorticoids excess. Both fibril- and network-forming collagen-specific mRNA levels decreased at the same time in both types of skeletal muscle. Specific mRNA level for MMP-2 did not change significantly during dexamethasone administration. Hindlimb grip strength simultaneously decreased. The effect of excessive glucocorticoids on the extracellular compartment did not differ significantly in skeletal muscles with different twitch characteristics.

Physical Education Increases Daily Moderate to Vigorous Physical Activity and Reduces Sedentary Time

BACKGROUND Physical activity (PA) is important to mental and physical health. Physical education (PE) lessons have the potential to increase daily moderate to vigorous PA (MVPA) and reduce sedentary time (SED). We measured MVPA and SED in primary school PE, determined the contribution of PE to daily MVPA and SED, and compared PA on days with and without PE. METHODS PA was measured in 504 first (ages 7-9) and second (ages 10-12) school level children for 1 school week, with inclusion criteria of at least 10 hours of valid data. Linear mixed methods were used for data analysis. RESULTS In PE, students spent 28.6 ± 16.5% in MVPA and 29.3 ± 19.8% in SED. Each additional MVPA minute in PE was associated with 1.4 more daily MVPA minutes. On days with PE, students had 12.8 (95% CI 10.5; 15.0) minutes more MVPA and 9.7 (95% CI 16.3; 3.1) minutes less SED compared with days without PE. CONCLUSIONS Although MVPA in PE was relatively low and SED high, PE significantly increased daily MVPA and reduced SED, confirming the important role of PE in supporting the healthy development of children.

Remodelling of Skeletal Muscle Extracellular Matrix: Effect of Unloading and Reloading

This chapter summarizes studies that examine remodelling of extracellular matrix (ECM) and role of regulatory factors of ECM during unloading and reloading. Hypokinesia has a catabolic effect on both the contractile apparatus and ECM of the skeletal muscle, causing the formation of muscle atrophy, the decrease of the synthesis of contractile proteins and disturbance of the collagen metabolism. The metabolism of fibrillar and non-fibrillar collagens in ECM plays a crucial role in exercise and sport, influencing the strength development through transmission of contractile force in skeletal muscle. The impair‐ ment of motor activity and muscle strength is accompanied by the muscle atrophy. The muscle atrophy caused by inactivity and recovery from atrophy demonstrates the plasticity of muscle. Muscle mass and volume increase in a relatively short time, but the recovery of strength takes much longer and is related with the regeneration of the muscle structures. The recovery period of the contractile apparatus and ECM structures is different in slow-and fast-twitch skeletal muscle. Although the muscle tissue’s response to inactivity is more pronounced than the response of ECM, important changes occur in the connective tissue structures during unloading, causing the impairment of the functional characteristics of the skeletal muscle.

Perspectives of children and adolescents on the perceived determinants of physical activity during recess

Abstract Promotion of healthy lifestyles in youth focuses on school-based interventions with the aim to increase physical activity (PA) during school days. Drawing on seventeen focus group discussions from three purposively selected Estonian schools, we explored factors that perceivably affect students’ recess physical activity (RPA). Both inductive and deductive principles of data analysis were used to extract major and subthemes related to factors that inhibit or enhance RPA. Participants identified barriers and facilitators to recess PA as originating mainly from physical and organizational school environment. Also, unsuitable weather was described as a barrier to being active. Additionally, feelings, behavioral and normative beliefs were described as constraining or facilitating RPA. Results highlighted two culture-specific unique perceived determinants of RPA that need to be addressed during the development of school-based interventions to increase PA.

Physical Activity, Sedentary Behaviour, Sleep Duration and Well-Being Among Estonian Schoolchildren: A Thematic Review

The knowledge of the importance of physical activity (PA) during childhood and adolescence has increased internationally, but physical inactivity of children and youth is still a growing problem all over the world. It is well known that increasing screen-time and sedentary activities compete with physical activities in leisure time. The level of PA decreases during growth and maturation, but the habits of healthy lifestyle have to form in this age. Physical activity is directly associated with healthy body composition. Therefore, the promotion of PA is an essential strategy to improve the physical and mental health and well-being of schoolchildren. At the same time sleep duration of schoolchildren is often not sufficient. The schoolsetting is a good environment for population-based PA interventions to introduce healthy life-style regardless of the socio-economic status of every student involved. To take action against increasing obesity rates and sedentary behaviour, and reducing PA levels among children, a number of organizations have issued their PA recommendations. To compile present chapter, the available data about the studies with Estonian school children were used and compared with contemporary related data obtained from studies with children from foreign countries. According to the recent studies, the PA levels of Estonian children, similarly to other European children are alarmingly low. To fight the increasing level of physical inactivity, various intervention programmes should be created and implemented to increase daily PA of children. In order to develop effective intervention programmes it is essential to estimate PA, sedentary behaviour and health indicators among Estonian children. Accordingly, the present thematic review includes the contemporary data of objectively measured PA studies of Estonian schoolchildren, which were compared to the results of peers in other countries. This enables to assess the position of Estonian children in the world according to their PA habits. The benefits of PA and adverse effects of excessive sedentary time should be emphasized in all educational instances.