Slowed muscle oxygen uptake kinetics with raised metabolism are not dependent on blood flow or recruitment dynamics

Oxygen uptake kinetics (τ[Image: see text]) are slowed when exercise is initiated from a raised metabolic rate. Whether this reflects the recruitment of muscle fibres differing in oxidative capacity, or slowed blood flow ([Image: see text]) kinetics is unclear. This study determined τ[Image: see text] in canine muscle in situ, with experimental control over muscle activation and [Image: see text] during contractions initiated from rest and a raised metabolic rate. The gastrocnemius complex of nine anaesthetised, ventilated dogs was isolated and attached to a force transducer. Isometric tetanic contractions (50 Hz; 200 ms duration) via supramaximal sciatic nerve stimulation were used to manipulate metabolic rate: 3 min stimulation at 0.33 Hz (S1), followed by 3 min at 0.67 Hz (S2). Circulation was initially intact (SPON), and subsequently isolated for pump-perfusion (PUMP) above the greatest value in SPON. Muscle [Image: see text] was determined contraction-by-contraction using an ultrasonic flowmeter and venous oximeter, and normalised to tension-time integral (TTI). τ[Image: see text]/TTI and τ[Image: see text] were less in S1(SPON) (mean ± s.d.: 13 ± 3 s and 12 ± 4 s, respectively) than in S2(SPON) (29 ± 19 s and 31 ± 13 s, respectively; P < 0.05). τ[Image: see text]/TTI was unchanged by pump-perfusion (S1(PUMP), 12 ± 4 s; S2(PUMP), 24 ± 6 s; P < 0.001) despite increased O(2) delivery; at S2 onset, venous O(2) saturation was 21 ± 4% and 65 ± 5% in SPON and PUMP, respectively. [Image: see text] kinetics remained slowed when contractions were initiated from a raised metabolic rate despite uniform muscle stimulation and increased O(2) delivery. The intracellular mechanism may relate to a falling energy state, approaching saturating ADP concentration, and/or slowed mitochondrial activation; but further study is required. These data add to the evidence that muscle [Image: see text] control is more complex than previously suggested

Who poisoned Hugh? - The STAR framework: integrating learning objectives with storytelling

Little research in Interactive Digital Storytelling (IDS) has been given to writing stories that convey a set of Learning Objectives (LOs). This is particularly important for educational IDS games. In this paper, we propose the STAR framework for formalizing the design of IDS stories for educational interventions. The story is designed as a set of red-herrings and clue puzzle in which the LOs are integrated. We present one of the three IDSes we designed based on this framework; we use one as a case study and present its evaluation. A study was undertaken to evaluate the game effectiveness in conveying the educational message. This study performed with 145 players shows that the players’ knowledge improved as a result of playing the game and that the change was statistically significant