Browsing Faculty of Medicine, Dentistry and Life Sciences by Subjects
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Energy expenditure, metabolic power and high speed activity during linear and multi-directional runningObjectives: The purpose of the study was to compare measures of energy expenditure derived from indirect calorimetry and micro-technology, as well as high power and high speed activity during linear and multi-directional running. Design: Repeated measures Methods: Twelve university standard team sport players completed a linear and multi-directional running condition. Estimated energy expenditure, as well as time at high speed (> 14.4 km.h-1) and high power (> 20 W.kg-1) were quantified using a 10 Hz micro-technology device and compared with energy expenditure derived from indirect calorimetry. Results: Measured energy expenditure was higher during the multi-directional condition (9.0 ± 2.0 cf. 5.9 ± 1.4 kcal.min-1), whereas estimated energy expenditure was higher during the linear condition (8.7 ± 2.1 cf. 6.5 ± 1.5 kcal.min-1). Whilst measures of energy expenditure were strongly related (r > 0.89, p < 0.001), metabolic power underestimated energy expenditure by 52% (95% LoA: 20-93%) and 34% (95% LoA: 12-59%) during the multi-directional and linear condition, respectively. Time at high power was 41% (95% LoA: 4-92%) greater than time at high speed during the multi-directional condition, whereas time at high power was 5% (95% LoA: -17-9%) lower than time at high speed during the linear condition. Conclusions: Estimated energy expenditure and time at high metabolic power can reflect changes in internal load. However, micro-technology cannot be used to determine the energy cost of intermittent running.
Muscle glycogen utilisation during Rugby match play: Effects of pre-game carbohydrateObjectives: Although the physical demands of Rugby League (RL) match-play are well-known, the fuel sources supporting energy-production are poorly understood. We therefore assessed muscle glycogen utilisation and plasma metabolite responses to RL match-play after a relatively high (HCHO) or relatively low CHO (LCHO) diet. Design: Sixteen (mean ± SD age; 18 ± 1 years, body-mass; 88 ± 12 kg, height 180 ± 8 cm) professional players completed a RL match after 36-h consuming a non-isocaloric high carbohydrate (n = 8; 6 g kg day−1) or low carbohydrate (n = 8; 3 g kg day−1) diet. Methods: Muscle biopsies and blood samples were obtained pre- and post-match, alongside external and internal loads quantified using Global Positioning System technology and heart rate, respectively. Data were analysed using effects sizes ±90% CI and magnitude-based inferences. Results: Differences in pre-match muscle glycogen between high and low carbohydrate conditions (449 ± 51 and 444 ± 81 mmol kg−1 d.w.) were unclear. High (243 ± 43 mmol kg−1 d.w.) and low carbohydrate groups (298 ± 130 mmol kg−1 d.w.) were most and very likely reduced post-match, respectively. For both groups, differences in pre-match NEFA and glycerol were unclear, with a most likely increase in NEFA and glycerol post-match. NEFA was likely lower in the high compared with low carbohydrate group post-match (0.95 ± 0.39 mmol l−1 and 1.45 ± 0.51 mmol l−1, respectively), whereas differences between the 2 groups for glycerol were unclear (98.1 ± 33.6 mmol l−1 and 123.1 ± 39.6 mmol l−1) in the high and low carbohydrate groups, respectively. Conclusions: Professional RL players can utilise ∼40% of their muscle glycogen during a competitive match regardless of their carbohydrate consumption in the preceding 36-h.