Seasonal variations in physical activity among Norwegian elementary school children in Arctic regions.

The aim of this study was to measure seasonal variations in physical activity (PA) during Polar Nights (PN) and Polar Days (PD) among elementary school children in the Arctic regions of Norway. One hundred and seventy-eight schoolchildren from 1st, 3rd, 5thand 7th grade participated in the study. Physical activity was measured for seven consecutive days with an ActiGraph GT3X-BT accelerometer and is expressed as total PA incounts per minute (cpm) and moderate-to-vigorous activity (MVPA) (min∙day-1). During PN, 51% of boys and 33% of girls met the PA recommendations, whereas 36% of boys and 34% of girls met the recommendations during PD. Time spent doing MVPA did not differ between the two seasons (all p ≥ 0.073). Overall, the children accumulated 613 ±154 cpm during PN, which was lower than during PD 704 ± 269 cpm, p < 0.001). A larger proportion of boys than girls met the PA recommendations during PN compared with PD. Our findings did not show any clear seasonal variation for MVPA or total PA among children,except for some differences within sexes in different grades. This study indicates that interventions aimed at increasing PA should be implemented throughout the year in the Arctic regions. .

Physiological Comparisons of Elite Male Visma Ski Classics and National Level Cross-Country Skiers During Uphill Treadmill Roller Skiing.

Longer distance cross-country ski (14-220 km) races such as the Visma Ski Classics (VSC) has recently gained attention in addition to the traditional Olympic distances (5-50 km) associated with cross-country (XC) skiing. These long-distance races are characterized by extensive use of the upper body while double poling (DP). While there is a substantial amount of research on Olympic distance XC skiing, the physiological capacities of VSC skiers has not yet been explored. We recruited seven elite male VSC skiers and seven well-trained national level male XC skiers to undergo three tests in the laboratory: (1) a one repetition maximum (1RM) strength test in a cable pulldown; (2) roller skiing tests on a treadmill (10.5% inclination) for determination of gross efficiency (GE) at submaximal speeds (8 and 10 km·h-1) in DP and diagonal stride (DS); (3) two ramp protocols to exhaustion (15% inclination, starting speed 7 km·h-1) in DP and DS for the assessment of peak and maximal oxygen uptake ( V . O2peak and V . O2max), respectively. Compared with the national level XC skiers, the VSC skiers performed similar in the 1RM cable pulldown, displayed 12.2% higher GE in DP at 8 km·h-1 but did not display any difference at 10 km·h-1, and had lower blood lactate concentration and heart rate at both submaximal speeds. The VSC skiers had longer time to exhaustion compared with the national level XC skiers during the two ramp protocols in DS (18%) and in DP (29%). The V . O2max was 10% higher in DS compared with DP, with no differences between the groups. The V . O2peak/ V . O2max-ratio of 90% did not differ between the two groups. In conclusion, the main differences were lower cardiorespiratory and metabolic responses at submaximal speeds as well as longer time to exhaustion in VSC skiers compared with national level XC skiers. This suggest efficiency to be the main difference between VSC and national level XC skiers.