ABSTRACT
This study examined the effects of pre-exercise carbohydrate availability on the time to exhaustion for moderate and heavy exercise. Seven men participated in a randomized order in two diet and exercise regimens each lasting 3 days with a 1-week interval for washout. The tests were performed at 50 percent of the difference between the first (LT1) and second (LT2) lactate breakpoint for moderate exercise (below LT2) and at 25 percent of the difference between the maximal load and LT2 for heavy exercise (above LT2) until exhaustion. Forty-eight hours before each experimental session, subjects performed a 90-min cycling exercise followed by 5-min rest periods and a subsequent 1-min cycling bout at 125 percent VO2max/1-min rest periods until exhaustion to deplete muscle glycogen. A diet providing 10 percent (CHOlow) or 65 percent (CHOmod) energy as carbohydrates was consumed for 2 days until the day of the experimental test. In the exercise below LT2, time to exhaustion did not differ between the CHOmod and the CHOlow diets (57.22 ± 24.24 vs 57.16 ± 25.24 min). In the exercise above LT2, time to exhaustion decreased significantly from 23.16 ± 8.76 min on the CHOmod diet to 18.30 ± 5.86 min on the CHOlow diet (P < 0.05). The rate of carbohydrate oxidation, respiratory exchange ratio and blood lactate concentration were reduced for CHOlow only during exercise above LT2. These results suggest that muscle glycogen depletion followed by a period of a low carbohydrate diet impairs high-intensity exercise performance.
Subject(s)
Adult , Humans , Male , Carbohydrate Metabolism/physiology , Dietary Carbohydrates/metabolism , Energy Metabolism/physiology , Physical Endurance/physiology , Physical Exertion/physiology , Dietary Carbohydrates/administration & dosage , Exercise Test/methods , Time FactorsABSTRACT
The widespread consumption of anorectics and combined anorectic + alcohol misuse are problems in Brazil. In order to better understand the interactive effects of ethanol (EtOH) and diethylpropion (DEP) we examined the locomotion-activating effects of these drugs given alone or in combination in mice. We also determined whether this response was affected by dopamine (DA) or opioid receptor antagonists. A total of 160 male Swiss mice weighing approximately 30 g were divided into groups of 8 animals per group. The animals were treated daily for 7 consecutive days with combined EtOH + DEP (1.2 g/kg and 5.0 mg/kg, ip), EtOH (1.2 g/kg, ip), DEP (5.0 mg/kg, ip) or the control solution coadministered with the DA antagonist haloperidol (HAL, 0.075 mg/kg, ip), the opioid antagonist naloxone (NAL, 1.0 mg/kg, ip), or vehicle. On days 1, 7 and 10 after the injections, mice were assessed in activity cages at different times (15, 30, 45 and 60 min) for 5 min. The acute combination of EtOH plus DEP induced a significantly higher increase in locomotor activity (day 1: 369.5 + or - 34.41) when compared to either drug alone (day 1: EtOH = 232.5 + or - 23.79 and DEP = 276.0 + or - 12.85) and to control solution (day 1: 153.12 + or - 7.64). However, the repeated administration of EtOH (day 7: 314.63 + or - 26.79 and day 10: 257.62 + or - 29.91) or DEP (day 7: 309.5 + or - 31.65 and day 10: 321.12 + or - 39.24) alone or in combination (day 7: 459.75 + or - 41.28 and day 10: 427.87 + or - 33.0) failed to induce a progressive increase in the locomotor response. These data demonstrate greater locomotion-activating effects of the EtOH + DEP combination, probably involving DA and/or opioid receptor stimulation, since the daily pretreatment with HAL (day 1: EtOH + DEP = 395.62 + or - 11.92 and EtOH + DEP + HAL = 371.5 + or - 6.76; day 7: EtOH + DEP = 502.5 + or - 42.27 and EtOH + DEP + HAL = 281.12 + or - 16.08; day 10: EtOH + DEP = 445.75 + or - 16.64 and EtOH + DEP + HAL = 376.75 + or - 16.4) and NAL (day 1: EtOH + DEP = 553.62 + or - 38.15 and EtOH + DEP + NAL = 445.12 + or - 55.67; day 7: EtOH + DEP = 617.5 + or - 38.89 and EtOH + DEP + NAL = 418.25 + or - 61.18; day 10: EtOH + DEP = 541.37 + or - 32.86 and EtOH + DEP + NAL = 427.12 + or - 51.6) reduced the locomotor response induced by combined administration of EtOH + DEP. These findings also suggest that a major determinant of combined anorectic-alcohol misuse may be the increased stimulating effects produced...