The effect of caffeine supplementation on exercise performance evaluated by a novel animal model

Introduction: Caffeinated drinks are used for improve performance. Animal models represent investigational strategy that circumvents most of the drawbacks of research in humans, including motivational factors and the placebo effect. No animal model that could test whether different forms of administering caffeine affect exercise propensity was found in the literature. Methods: An animal model of grouped voluntary exercise was tested. Two-month-old male C57/bl mice were housed in a cage fitted with one running wheel and a monitoring system. Six animals per cage were introduced individually. To assess the sensitivity of the model, the effect of different caffeinated drinks was observed in mice exercising ad libitum. During 2 days, the mice received: 1) pure anhydrous caffeine 0.125 mg/mL (PC), 2) cola drink (CC), and 3) caffeine-taurine-glucuronolactone drink (CTG), intercalating wash-out periods of 2 days, receiving pure water. Results: The distance run during the periods of water ingestion was significantly lower than during the periods of stimulant drinks ingestion: PC (5.6 ± 1.3 km; p = 0.02), of CC ingestion (7.6 ± 0.6 km; p = 0.001), and of CTG ingestion (8.3 ± 1.6 km; p = 0.009). The performances when ingesting the three caffeinated drinks do not follow a dose-response curve. Conclusions: The model described here was able to measure the effect of caffeine intake on voluntary exercise of mice. The sensitivity of the model to the effect of caffeine needs to be further validated. The action of each component of the drinks on exercise performance needs to be clarified in future research. The present model is adequate for such investigation (AU)

Immediate and overnight recumbence-dependent changes of neck circumference: relationship with OSA severity in obese and nonobese subjects.

BACKGROUND: Overnight increases in neck circumference - attributed to rostral fluid displacement - correlate with the severity of obstructive sleep apnea (OSA). No studies were found investigating the relationship between OSA severity and recumbence-related immediate changes in neck circumference. We evaluated the relationship of OSA severity with immediate recumbence-related and overnight changes in neck circumference in obese and nonobese subjects. METHODS: Male patients undergoing full-night in-laboratory polysomnography had their neck and ankle circumferences determined before and after sleep, both while standing and supine. Circumference changes were calculated by the difference between standing and recumbent positions (Immediate Change) and between before and after sleep (Overnight Change). RESULTS: Immediate Change in neck circumference showed a linear significant correlation with apnea-hypopnea index (AHI; r=0.37373; p=0.012) and with lowest O2 saturation (r=-0.35355; p=0.017). In a multivariate model to predict AHI, adjusting for age and obesity, Immediate Change in neck circumference is the only significant regressor (beta=0.34; p=0.03). The Overnight Change in neck circumference correlated neither with the AHI nor with the lowest SaO2. CONCLUSION: Correlation of AHI with the immediate increase in neck circumference on assuming recumbence indicates that fast components of tissue displacement, besides overnight fluid displacement, may have implications in the pathogenesis of OSA.