Seasonal variation in physical performance-related variables in male NCAA Division III soccer players.

The purpose of this study was to examine changes in various aerobic and anaerobic physical performance measures in male National Collegiate Athletic Association (NCAA) Division III soccer players during the competitive soccer season. Twelve starters of the men's soccer team (mean +/- SD; age = 20.0 +/- 0.9 years, height = 175.7 +/- 8.1 cm, body mass = 73.9 +/- 11.00 kg, body mass index [BMI] 24.0 +/- 3.0 kg.m2, and percent body fat = 10.6 +/- 5.4%) were tested at the beginning (PRS) and the end (POS) of the collegiate soccer season. Each experimental trial included a maximal aerobic capacity test (VO2max); 10-, 30-, and 40-m sprints; pro-agility test; and the Wingate anaerobic power test (WAnT). From PRS to POS, VO2max significantly increased (51.05 +/- 5.97 vs. 54.64 +/- 4.90 ml.kg-1.min-1), and the 10- and 30-m sprint were significantly lower (2.03 +/- 0.15 vs. 1.96 +/- 0.11 seconds and 4.72 +/- 0.26 vs. 4.51 +/- 0.24 seconds, respectively). Anthropometric measures, 40-m sprint, pro-agility test, and WAnT were not significantly different between PRS and POS. The results of this study indicate that NCAA Division III male soccer players appear to improve aerobic and anaerobic performance measures during the competitive soccer season. It is arguable that these performance improvements may represent a poor preseason conditioning level that may result in a competitive disadvantage during the early stages of the season. An ongoing process of recruiting better-quality players that may closely follow the off-season training regimen may partially remedy this problem.

Extended access to nicotine self-administration leads to dependence: Circadian measures, withdrawal measures, and extinction behavior in rats.

The present study characterized nicotine intake, circadian patterns of food and water intake, precipitated somatic signs of withdrawal, and extinction of nicotine-seeking behavior in rats with 23-h access to intravenous self-administration (IVSA). Separate groups of animals were allowed access to nicotine IVSA (0.015, n = 9; 0.03, n = 14; 0.06, n = 16; mg/kg/0.1 ml infusion/s; fixed ratio 1) and trained to nosepoke for food and water 23 h/day for 40 consecutive days. Somatic signs of nicotine withdrawal were examined following saline or mecamylamine administration (1.5 mg/kg i.p.), and extinction of nicotine-seeking behavior was assessed. A dose-dependent decrease in lever responding and an increase in nicotine intake were observed, with the highest nicotine dose producing the lowest amount of lever responding and the highest amount of nicotine intake. Nicotine acutely reduced diurnal and nocturnal food intake, producing smaller and fewer meals, and an increased rate of eating. Differences in rate of nicotine intake between the light and dark phase decreased significantly, especially in rats receiving higher unit nicotine doses (0.03 and 0.06 mg/kg), along with long-term decreases in the circadian profile and amplitude of feeding. Mecamylamine precipitated robust withdrawal signs, the magnitude of which was positively correlated with the total amount of self-administered nicotine. Extinction of nicotine-seeking behavior was observed and was facilitated by removal of nicotine-associated cues. The results demonstrate that rats will self-administer nicotine to the point of producing dependence, as measured by somatic signs, resistance to extinction, and measures of food intake.

Diminished nicotine withdrawal in adolescent rats: implications for vulnerability to addiction.

RATIONALE: Enhanced reinforcing effects of nicotine during adolescence appear to contribute to the rapid development of dependence in this age group. However, the contribution of nicotine withdrawal to dependence in adolescents is unclear. OBJECTIVE: We compared motivational and somatic signs of nicotine withdrawal in adolescent and adult rats. MATERIALS AND METHODS: In experiment 1, motivational signs of nicotine withdrawal were compared using intracranial self-stimulation procedures after administration of mecamylamine (1.5 mg/kg, i.p.) in adolescent and adult rats made dependent on nicotine (9 mg/kg/day). Somatic signs of withdrawal were compared in two experiments using various doses of nicotine (adolescent doses: 0, 1.6, 3.2, 4.7 mg/kg/day; adult doses: 0, 1, 2.1, 3.2 mg/kg/day, expressed as nicotine base) to produce dependence and one dose of mecamylamine (1.5 mg/kg, i.p.) to precipitate withdrawal (experiment 2) and in a subsequent experiment, using various doses of mecamylamine (0, 0.75, 1.5, 3.0 mg/kg, i.p.) to precipitate withdrawal and a dose of nicotine (adolescent dose: 4.7 mg/kg/day; adult dose: 3.2 mg/kg/day) that produced equivalent nicotine blood levels in these age groups (experiment 3). RESULTS: Adolescents did not display the decreases in brain reward function observed in adults experiencing withdrawal, and displayed fewer somatic signs of nicotine withdrawal relative to adults regardless of the dosing procedure used. CONCLUSION: The negative effects of nicotine withdrawal are lower during adolescence relative to later periods of development. Both the enhanced rewarding effects and the diminished nicotine withdrawal likely contribute to the rapid development of nicotine use during adolescence.

Enhanced alcohol self-administration after intermittent versus continuous alcohol vapor exposure.

BACKGROUND: Ethanol self-administering rats exhibit enhanced responding during withdrawal from continuous exposure to ethanol vapor. This study compared self-administration of ethanol during withdrawal from continuous versus intermittent ethanol vapor. METHODS: Experiment 1 examined self-administration of ethanol in rats trained to self-administer ethanol after continuous, intermittent (14 hr on and 10 hr off), or no (i.e., controls) ethanol vapor exposure. Exposure time was equalized such that the intermittent group received 4 weeks of exposure and the continuous group received 2 weeks of exposure. Four self-administration tests were conducted 2 hr after removal from vapor, and each test was separated by 3 to 4 days of ethanol vapor. Experiment 2 examined self-administration of ethanol after 2 weeks of intermittent vapor either 2 or 8 hr after removal from vapor. Experiment 3 addressed the specificity of the increased responding for ethanol by examining saccharin self-administration after 2 weeks of intermittent vapor. RESULTS: Four weeks of intermittent exposure produced an increase in ethanol self-administration during the first withdrawal relative to controls and relative to animals receiving 2 weeks of continuous exposure. The continuous group was indistinguishable from controls on the first test and gradually increased their responding across tests. Two weeks of intermittent exposure also increased ethanol self-administration, and there was no difference in this effect 2 or 8 hr after removal from vapor. There was no difference in saccharin self-administration in control rats and those given 2 weeks of intermittent exposure. CONCLUSIONS: The finding that intermittent exposure produces more rapid increases in self-administration of ethanol relative to continuous exposure suggests that intermittent exposure may be associated with a more rapid escalation of the allostatic processes responsible for excessive ethanol self-administration. The mechanisms that drive the increases in drinking during withdrawal are similar after 2 and 8 hr of withdrawal and seem to be specific to ethanol.