Morphological and biochemical characteristics of biopsies obtained from gastrocnemius (GAS) and triceps brachii muscle (TRI), as well as maximal O2 uptake (VO2 max) and O2 deficit, were determined in 10 well-trained cross-country skiers before and after a 2-wk stay (2,100 m above sea level) and training (2,700 m above sea level) at altitude. On return to sea level, VO2 max was the same as the prealtitude value, whereas an increase in O2 deficit (29%) and in short-term running performance (17%) was observed (P less than 0.05). GAS showed maintained capillary supply but a 10% decrease in mitochondrial enzyme activities (P less than 0.05), whereas an increase in capillary supply (P less than 0.05) but unchanged mitochondrial enzyme activities were observed in TRI. Buffer capacity was increased by 6% in both GAS and TRI (P less than 0.05). A positive correlation was found between the relative increase in buffer capacity of GAS and short-term running time (P less than 0.05). Thus the present study indicates no effect of 2 wk of altitude training on VO2 max but provides evidence to suggest an improvement in short-term exercise performance, which may be the result of an increase in muscle buffer capacity.

In this systematic review, we summarised and evaluated the evidence for benefits of immersive nature-experience on children and adolescents' mental, physical and social health. An electronic search was performed for English language articles published between January 2004 and May 2017.Data were extracted from 84 publications that met the inclusion criteria. Study quality was assessed for a subset of the studies, i.e. controlled between-and within-subjects studies, using a systematic assessment scheme, and the quality of the evidence was reviewed at an outcome level. Across heterogeneous types of immersive nature-experience, there was conditional support for benefits on self-esteem, self-efficacy, resilience and academic and cognitive performance. Correlational research evidenced higher levels of physical activity in natural environments than comparison conditions. Benefits for outcomes such as self-concept, problem solving, and mood were more inconclusive. In addition, social skill-oriented and behavioural indicators were improved, although the categories comprised different outcomes. Risk of bias, insufficient sampling methods and unsuited comparison groups were common study limitations.

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