Low carbohydrate diet affects the oxygen uptake on-kinetics and rating of perceived exertion in high intensity exercise

The aim of this study was to determine if the carbohydrate (CHO) availability alters the rate of increase in the rating of perceived exertion (RPE) during high intensity exercise and whether this would be associated with physiological changes. Six males performed high intensity exercise after 48 h of controlled, high CHO (80%) and low CHO (10%) diets. Time to exhaustion was lower in the low compared to high CHO diet. the rate of increase in RPE was greater and the VO(2) slow component was lower in the low CHO diet than in the control. There was no significant condition effect for cortisol, insulin, pH, plasma glucose, potassium, or lactate concentrations. Multiple linear regression indicated that the total amplitude of VO(2) and perceived muscle strain accounted for the greatest variance in the rate of increase in RPE. These results suggest that cardiorespiratory variables and muscle strain are important afferent signals from the periphery for the RPE calculations.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Univ Fed Alagoas, Fac Nutr, Sports Sci Res Grp, BR-7072970 Maceio, Alagoas, BrazilUniv São Paulo, Sch Phys Educ & Sport, São Paulo, BrazilUniversidade Federal de São Paulo, Div Nutr Physiol, Dept Physiol, São Paulo, BrazilUniversidade Federal de São Paulo, Hosp Kidney & Hypertens, Div Nephrol, São Paulo, BrazilUniversidade Federal de São Paulo, Div Nutr Physiol, Dept Physiol, São Paulo, BrazilUniversidade Federal de São Paulo, Hosp Kidney & Hypertens, Div Nephrol, São Paulo, BrazilFAPESP: 2006-60641-6Web of Scienc

RELATIONSHIP BETWEEN TRAINING STATUS AND MAXIMAL FAT OXIDATION RATE

This study aimed to compare maximal fat oxidation rate parameters between moderate- and low-performance runners. Eighteen runners performed an incremental treadmill test to estimate individual maximal fat oxidation rate (Fatmax) based on gases measures and a 10,000-m run on a track. The subjects were then divided into a low and moderate performance group using two different criteria: 10,000-m time and VO2max values. When groups were divided using 10,000-m time, there was no significant difference in Fatmax (0.41 ± 0.16 and 0.27 ± 0.12 g.min-1, p = 0.07) or in the exercise intensity that elicited Fatmax (59.9 ± 16.5 and 68.7 ± 10.3 % O2max, p = 0.23) between the moderate and low performance groups, respectively (p > 0.05). When groups were divided using VO2max values, Fatmax was significantly lower in the low VO2max group than in the high VO2max group (0. 29 ± 0.10 and 0.47 ± 0.17 g.min-1, respectively, p < 0.05) but the intensity that elicited Fatmax did not differ between groups (64.4 ± 14.9 and 61.6 ± 15.4 %VO2max). Fatmax or %VO2max that elicited Fatmax was not associated with 10,000 m time. The only variable associated with 10,000-m running performance was %VO2max used during the run (p < 0.01). In conclusion, the criteria used for the division of groups according to training status might influence the identification of differences in Fatmax or in the intensity that elicits Fatmax

Effects of Caffeine Ingestion on Anaerobic Capacity in a Single Supramaximal Cycling Test

The aim of this study was to verify the effects of caffeine on anaerobic capacity estimated by the sum of the estimated glycolytic [E[La]] and phosphagen [EPCr] metabolism based on blood lactate and excess post-oxygen consumption responses (AC[La−]+EPOCfast). Fourteen male cyclists were submitted to a graded exercise test to determine the maximal oxygen uptake (V°O2max) and intensity associated with V°O2max (iV°O2max). Subsequently, the participants performed two supramaximal efforts at 115% of iV°O2max to determine the AC[La−]+EPOCfast, after previous supplementation with caffeine (6 mg·kg−1) or a placebo (dextrose), in a cross over, randomized, double blind, and placebo-controlled design. The time to exhaustion was higher in the caffeine (186.6 ± 29.8 s) than in the placebo condition (173.3 ± 25.3 s) (p = 0.006) and a significant correlation was found between them (r = 0.86; P = 0.00008). Significant differences were not found between AC[La−]+EPOCfast values from the placebo (4.06 ± 0.83 L and 55.2 ± 5.7 mL·kg−1) and caffeine condition (4.00 ± 0.76 L and 54.6 ± 5.4 mL·kg−1); however, a significant correlation was observed only for AC[La−]+EPOCfast expressed in absolute values (r = 0.74; p &lt; 0.002). The E[La] and EPCr also presented no significant differences and they were significantly correlated (r = 0.82 and r = 0.55, respectively; p &lt; 0.05). We conclude based on the overall comparison of mean values between two treatments that acute caffeine ingestion improves the time to exhaustion but does not affect anaerobic capacity estimation

Effect of performance level on pacing strategy during a 10-km running race

The aim of this study was to examine the influence of the performance level of athletes on pacing strategy during a simulated 10-km running race, and the relationship between physiological variables and pacing strategy. Twenty-four male runners performed an incremental exercise test on a treadmill, three 6-min bouts of running at 9, 12 and 15 km h−1, and a self-paced, 10-km running performance trial; at least 48 h separated each test. Based on 10-km running performance, subjects were divided into terziles, with the lower terzile designated the low-performing (LP) and the upper terzile designated the high-performing (HP) group. For the HP group, the velocity peaked at 18.8 ± 1.4 km h−1 in the first 400 m and was higher than the average race velocity (P 0.05) and this initial velocity was not different from LP average racing velocity (14.5 ± 0.7 km h−1). The velocity then decreased non-significantly until 9,600 m (P > 0.05), followed by an increase at the end (P < 0.05). The peak treadmill running velocity (PV), running economy (RE), lactate threshold (LT) and net blood lactate accumulation at 15 km h−1 were significantly correlated with the start, middle, last and average velocities during the 10-km race. These results demonstrate that high and low performance runners adopt different pacing strategies during a 10-km race. Furthermore, it appears that important determinants of the chosen pacing strategy include PV, LT and RE