e62 Thursday 16 October Papers / Journal of Science and Medicine in Sport 18S (2014) e23–e71

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Dopamine D1 deceptor mediatescaffeine-influenced exercised performance,thermoregulation and brain neurotransmission

X. Zheng

Hiroshima University, Australia

Background: Caffeine is widely consumed to improve exer-cise performance. Recently, we observed that caffeine improvedendurance exercise performance, increased core body tempera-ture (Tcore) and extracellular dopamine release in the preopticarea and anterior hypothalamus (PO/AH) in exercising rats (Zhengand Hasegawa, 2014). However, it is difficult to conclude caffeine-improved exercise performance is due to central dopaminergicactivation. To address this issue, it is necessary to examinethe effect of blockage of central dopaminergic neurotransmis-sion on the ergogenic and hyperthermic effects of caffeine.Moreover, the blockage of dopamine D1 receptor preventedcaffeine-induced hyperactivity and hyperthermia at rest. The pur-pose of this study was to examine the alterations in caffeineaffected-thermoregulation, neurotransmitter release in the PO/AH,and endurance exercise performance after the administration of adopamine D1 receptor antagonist.

Methods: Tcore, tail skin temperature (Ttail: an index of heatloss), and oxygen consumption (VO2: an index of heat produc-tion) were measured. A microdialysis probe was inserted into thePO/AH for measurement of extracellular dopamine, noradrenalineand serotonin levels. After 40 min of baseline collection, rats wereintraperitoneally injected with either dopamine D1 receptor antag-onist (SCH: SCH23390, 1 mg/kg) or saline (SAL). Rats were nextintraperitoneally injected with either 10 mg/kg caffeine (CAF) orSAL, 60 min before the start of exercise. Rats ran until fatigue onthe treadmill with a 5% grade at a speed of 18 m min−1 at 23 ◦C.

Results: The run time to fatigue (RTTF) in SAL was longerthan that in SCH and SCH-CAF, but there was no differenceof RTTF between SCH and SCH-CAF (SAL: 99.3 ± 25.4 min, SCH:20.8 ± 20.0 min, SCH-CAF: 19.4 ± 15.1 min). SCH increased Tcore,decreased Ttail and extracellular dopamine in the PO/AH. Pre-treatment with SCH inhibited caffeine-increased Tcore, Ttail, VO2,and dopamine release. Neither caffeine nor SCH affected noradren-aline and serotonin in the PO/AH.

Discussion: Consistent with Balthazar et al. (2010), we foundthat SCH-impaired exercise capacity may be related to the block-age of dopamine release in the PO/AH-induced the decrease ofthe tolerance to heat storage. Increased brain dopamine releaseimproved the exercise capacity through overriding the criticallimiting Tcore. In this study, SCH prevented caffeine-increaseddopamine, inhibited heat loss, increased Tcore, induced fatigue,impaired the ergogenic effect of caffeine. Our results indicatethat central dopaminergic pathways play an important role in theergogenic effect of caffeine.

http://dx.doi.org/10.1016/j.jsams.2014.11.285

96

Emerging technologies for physical activitybehavior change in children and adolescents:Opportunities, challenges and future directions

D. Lubans

Priority Research Centre in Physical Activity andNutrition, School of Education, University ofNewcastle, Australia

Background: In recent years there has been a proliferation oftechnology-based physical activity interventions in various popula-tions. Although emerging technologies have considerable potentialfor engaging users, evidence of their utility for increasing physicalactivity in young people is far from convincing. The aim of this pre-sentation is to provide an overview of emerging technologies forincreasing physical activity in children and adolescents.

Methods: A narrative review of technology-based interventionsfor increasing physical activity in young people was undertaken.The review was focused on mobile health (mHealth) interven-tions and smartphone applications (apps) and next-generationelectronic lifestyle activity monitors (e.g., Fitbit, Jawbone andNike). Product characteristics and inclusion of behavior changetechniques, as well as intervention efficacy and feasibility wereexplored.

Results: Recent reviews have evaluated the quality of smart-phone apps, yet few mHealth interventions utilizing apps havebeen conducted with children and adolescents. The majority ofexisting smartphone apps designed for young people do notinclude evidence-based behavior change techniques or adhereto expert recommendations for obesity prevention. Commonfunctions of existing apps include: (i) physical activity demon-strations/instructions, (ii) movement powered gamification, (iii)information about health benefits of physical activity, and (iv)self-monitoring and goal setting. Common behavior change tech-niques integrated into next-generation electronic lifestyle activitymonitors include: (i) goal setting and self-monitoring, (ii) feed-back on physical activity behavior, (iii) social support, comparisonand rewards, and (iv) information about health benefits of physi-cal activity. Interventions incorporating mHealth technology haveachieved some success in reducing screen-time and improvingweight status in adolescents, but intervention effects for physi-cal activity have been modest. No studies evaluating the efficacyof physical activity interventions using next-generation lifestyleactivity monitors in children and adolescents were found. Toofew studies have been conducted to understand the challengesof implementing mHealth interventions, but cost and access todevices may be barriers in specific populations. In addition, dif-ficulties maintaining user interest due to competition from othercommercial and social media efforts may reduce effectiveness.

Discussion: It is unlikely that technology-based interventionswill provide a ‘silver bullet’ for the global pandemic of inactiv-ity, but they may have utility for engaging low-active youth andaccessing ‘hard-to-reach’ populations. Future studies are neededto determine if smartphone apps and next-generation electroniclifestyle activity monitors are appropriate as stand-alone strategiesor as adjuncts to face-to-face behavior change interventions.

http://dx.doi.org/10.1016/j.jsams.2014.11.286