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Purpose: The aim of the study was to examine the effects of a post-prandial 20 min nap on a short-term physical exercise and subsequent sleep in athletes keeping their usual sleep schedules and in 5-h phase-advance condition., Methods: Sixteen healthy young male athletes (age 22.2 ± 1.7 years, non-habitual nappers) participated in the study. After a baseline 8-h time in bed in normal and 5-h advanced sleep schedules, a standardized morning and lunch in a laboratory environment, subjects underwent either a nap (20 min of sleep elapsed from 3 epochs of stage 1 or 1 epoch of stage 2), or a rest without sleep by lying in a bed, between 13:00 and 14:00 hours in non-shifted condition or 08:00 and 09:00 hours in shifted condition, after which anaerobic exercises were performed twice 2 h apart. Core body temperature was recorded throughout the study period., Results: The nap extended sleep onset latency from 6.72 ± 3.83 to 11.84 ± 13.44 min, after shifted condition but did not modify sleep architecture of the post-trial night among athletes, whether shifted or not. Moreover, napping did not improve physical performance but it delayed acrophase and batyphase of core body temperature rhythm parameters., Conclusion: Napping showed no reliable benefit on short-term performances of athletes exercising at local time or after a simulated jet lag.

This study investigated (a) changes in ghrelin and peptide YY (PYY) concentrations during a weight reduction programme and (b) baseline ghrelin and PYY levels as predictors of weight loss in 32 severely obese adolescents (BMI z score = 4.1). Subjects spent an academic year in an institution for childhood obesity. Fasting ghrelin and PYY, leptin, insulin levels and insulin resistance were measured at baseline (month 0) and during the programme (months 3, 6, 9). In addition, 15 normal-weight teenagers served as reference for the baseline assessments. At baseline, obese teenagers had lower ghrelin and PYY concentrations than normal-weight adolescents (P < 0.05). Moreover, they showed significantly higher leptin, insulin levels and homeostasis model assessment (HOMA) (P < 0.0001). During the lifestyle modification, there was a significant decrease in body weight among obese teenagers, associated with an increase in ghrelin (apparent from month 6; P < 0.05), a decrease in leptin (from month 3; P < 0.05) and a decrease in insulin and HOMA (from month 3; P < 0.0001), without any significant change in PYY. Anthropometrical changes were correlated neither with baseline ghrelin levels nor with changes in ghrelin and PYY after the lifestyle modification. However, higher baseline PYY tended to correlate with greater anthropometrical changes (P < 0.1). In adolescents with severe obesity, a long-term combination of supervised aerobic exercises and a balanced diet led to weight reduction and increased ghrelin concentrations, without any change in PYY concentrations. Moreover, baseline PYY concentrations might be considered as predictors of weight loss.