Energy expenditure and influence of physiologic factors during marathon running

This study examined energy expenditure and physiologic determinants for marathon performance in recreational runners. Twenty recreational marathon runners participated (10 males aged 41 +/- 11.3 years, 10 females aged 42.7 +/- 11.7 years). Each subject completed a V(.-)O2max and a 1-hour treadmill run at recent marathon pace, and body composition was indirectly determined via dual energy X-ray absorptiometry. The male runners exhibited higher V(.-)O2max (ml x kg(-1) x min(-1)) values (52.6 +/- 5.5) than their female counterparts (41.9 +/- 6.6), although ventilatory threshold (T-vent) values were similar between groups (males: 76.2 +/- 6.1 % of V(.-)O2max, females: 75.1 +/- 5.1%). The male runners expended more energy (2,792 +/- 235 kcal) for their most recent marathon as calculated from the 1-hour treadmill run at marathon pace than the female runners (2,436 +/- 297 kcal). Body composition parameters correlated moderately to highly (r ranging from 0.50 to 0.87) with marathon run time. Also, V(.-)O2max (r = -0.73) and ventilatory threshold (r = -0.73) moderately correlated with marathon run time. As a group, the participants ran near their ventilatory threshold for their most recent marathon (r = 0.74). These results indicate the influence of body size on marathon run performance. In general, the larger male and female runners ran slower and expended more kilocalories than smaller runners. Regardless of marathon finishing time, the runners maintained a pace near their T-vent, and as T-vent or V(.-)O2max increased, marathon performance time decreased.     

Influence of acute plasma volume expansion on VO2 kinetics, VO2 peak, and performance during high-intensity cycle exercise.

The purpose of this study was to examine the influence of acute plasma volume expansion (APVE) on oxygen uptake (V(O2)) kinetics, V(O2peak), and time to exhaustion during severe-intensity exercise. Eight recreationally active men performed "step" cycle ergometer exercise tests at a work rate requiring 70% of the difference between the gas-exchange threshold and V(O2max) on three occasions: twice as a "control" (Con) and once after intravenous infusion of a plasma volume expander (Gelofusine; 7 ml/kg body mass). Pulmonary gas exchange was measured breath by breath. APVE resulted in a significant reduction in hemoglobin concentration (preinfusion: 16.0 +/- 1.0 vs. postinfusion: 14.7 +/- 0.8 g/dl; P < 0.001) and hematocrit (preinfusion: 44 +/- 2 vs. postinfusion: 41 +/- 3%; P < 0.01). Despite this reduction in arterial O(2) content, APVE had no effect on V(O2) kinetics (phase II time constant, Con: 33 +/- 15 vs. APVE: 34 +/- 12 s; P = 0.74), and actually resulted in an increased V(O2peak) (Con: 3.90 +/- 0.56 vs. APVE: 4.12 +/- 0.55 l/min; P = 0.006) and time to exhaustion (Con: 365 +/- 58 vs. APVE: 424 +/- 64 s; P = 0.04). The maximum O(2) pulse was also enhanced by the treatment (Con: 21.3 +/- 3.4 vs. APVE: 22.7 +/- 3.4 ml/beat; P = 0.04). In conclusion, APVE does not alter V(O2) kinetics but enhances V(O2peak) and exercise tolerance during high-intensity cycle exercise in young recreationally active subjects.     

Relation between maximal aerobic power and the ability to repeat sprints in young basketball players

The aim of this study was to examine the effects of maximal aerobic power (V(.-)O2max peak) level on the ability to repeat sprints (calculated as performance decrement and total sprinting time) in young basketball players. Subjects were 18 junior, well-trained basketball players (age, 16.8 +/- 1.2 years; height, 181.3 +/- 5.7 cm; body mass, 73 +/- 10 kg; V(.-)O2max peak, 59.6 +/- 6.9 ml x kg(-1) x min(-1)). Match analysis and time-motion analysis of competitive basketball games was used to devise a basketball-specific repeated-sprint ability protocol consisting of ten 15-m shuttle run sprints with 30 s of passive recovery. Pre, post, and post plus 3-minute blood lactate concentrations were 2.5 +/- 0.7, 13.6 +/- 3.1, and 14.2 +/- 3.5 mmol x L(-1), respectively. The mean fatigue index (FI) value was 3.4 +/- 2.3% (range, 1.1-9.1%). No significant correlations were found between V(.-)O2max peak and either FI or total sprint time. A negative correlation (r = -0.75, p = 0.01) was found between first-sprint time and FI. The results of this study showed that V(.-)O2max peak is not a predictor of repeated-sprint ability in young basketball players. The high blood lactate concentrations found at the end of the repeated-sprint ability protocol suggest its use for building lactate tolerance in conditioned basketball players.     

Exercise-induced prostacyclin release positively correlates with VO(2max) in young healthy men

In this study we have evaluated the effect of maximal incremental cycling exercise (IE) on the systemic release of prostacyclin (PGI(2)), assessed as plasma 6-keto-PGF(1alpha) concentration in young healthy men. Eleven physically active - untrained men (mean +/- S.D.) aged 22.7 +/- 2.1 years; body mass 76.3 +/- 9.1 kg; BMI 23.30 +/- 2.18 kg . m(-2); maximal oxygen uptake (VO(2max)) 46.5 +/- 3.9 ml . kg(-1) . min(-1), performed an IE test until exhaustion. Plasma concentrations of 6-keto-PGF(1alpha), lactate, and cytokines were measured in venous blood samples taken prior to the exercise and at the exhaustion. The net exercise-induced increase in 6-keto-PGF(1alpha) concentration, expressed as the difference between the end-exercise minus pre-exercise concentration positively correlated with VO(2max) (r=0.78, p=0.004) as well as with the net VO(2) increase at exhaustion (r=0.81, p=0.003), but not with other respiratory, cardiac, metabolic or inflammatory parameters of the exercise (minute ventilation, heart rate, plasma lactate, IL-6 or TNF-alpha concentrations). The exercise-induced increase in 6-keto-PGF(1alpha) concentration?? was significantly higher (p=0.008) in a group of subjects (n=5) with the highest VO(2max) when compared to the group of subjects with the lowest VO(2max), in which no increase in 6-keto-PGF(1alpha) concentration was found. In conclusion, we demonstrated, to our knowledge for the first time, that exercise-induced release of PGI(2) in young healthy men correlates with VO(2max), suggesting that vascular capacity to release PGI(2) in response to physical exercise represents an important factor characterizing exercise tolerance. Moreover, we postulate that the impairment of exercise-induced release of PGI(2) leads to the increased cardiovascular hazard of vigorous exercise.     

Effects of isocaloric carbohydrate vs. carbohydrate-protein supplements on cycling time to exhaustion

The purpose of this study was to investigate the effects of isocaloric carbohydrate (CHO) and carbohydrate-protein (CHO-Pro) supplements on time to exhaustion. Eleven moderately aerobically fit adults (V[Combining Dot Above]O2max= 48.3 ± 6.5 ml·kg·min) performed a maximal cycle ergometer test for the determination of V[Combining Dot Above]O2max. At least 72 hours later, the participants performed a time-to-exhaustion test at a power output equivalent to the power output when subjects were at 75% of their V[Combining Dot Above]O2max. Either the CHO or the CHO-Pro supplement was administered at 0, 30, 60, 90, and 120 minutes after this test. After 3 hours of recovery and supplement ingestion, a second time-to-exhaustion test was performed. This testing protocol was repeated for the third visit, but the supplement not given during the second visit was administered. The results indicated that there was no significant difference in time to exhaustion after isocaloric CHO (pretest 22.4 ± 2.84 minutes, posttest 25.4 ± 4.45 minutes) and CHO-Pro (pretest 22.3 ± 3.46 minutes, posttest 24.0 ± 5.08 minutes) supplementation. Carbohydrate and CHO-Pro ingestion after exercise appear to have similar effects on short-term recovery.     

Pre-exercise hyperhydration delays dehydration and improves endurance capacity during 2 h of cycling in a temperate climate

Whether the use of pre-exercise hyperhydration could improve the performance of athletes who do not hydrate sufficiently during prolonged exercise is still unknown. We therefore compared the effects of pre-exercise hyperhydration and pre-exercise euhydration on endurance capacity, peak power output and selected components of the cardiovascular and thermoregulatory systems during prolonged cycling. Using a randomized, crossover experimental design, 6 endurance-trained subjects underwent a pre-exercise hyperhydration (26 ml of water x kg body mass(-1) with 1.2 g glycerol x kg body mass(-1)) or pre-exercise euhydration period of 80 min, followed by 2 h of cycling at 65% maximal oxygen consumption (VO(.)2max) (26-27 degrees C) that were interspersed by 5, 2-min intervals performed at 80% V(.)O2max. Following the 2 h cycling exercise, subjects underwent an incremental cycling test to exhaustion. Pre-exercise hyperhydration increased body water by 16.1+/-2.2 ml.kg body mass(-1). During exercise, subjects received 12.5 ml of sports drink x kg body mass(-1). With pre-exercise hyperhydration and pre-exercise euhydration, respectively, fluid ingestion during exercise replaced 31.0+/-2.9% and 37.1+/-6.8% of sweat losses (p>0.05). Body mass loss at the end of exercise reached 1.7+/-0.3% with pre-exercise hyperhydration and 3.3+/-0.4% with pre-exercise euhydration (p<0.05). During the 2 h of cycling, pre-exercise hyperhydration significantly decreased heart rate and perceived thirst, but rectal temperature, sweat rate, perceived exertion and perceived heat-stress did not differ between conditions. Pre-exercise hyperhydration significantly increased time to exhaustion and peak power output, compared with pre-exercise euhydration. We conclude that pre-exercise hyperhydration improves endurance capacity and peak power output and decreases heart rate and thirst sensation, but does not reduce rectal temperature during 2 h of moderate to intense cycling in a moderate environment when fluid consumption is 33% of sweat losses.     

Dietary carbohydrate, muscle glycogen content, and endurance performance in well-trained women.

This study examined the ability of well-trained eumenorrheic women to increase muscle glycogen content and endurance performance in response to a high-carbohydrate diet (HCD; approximately 78% carbohydrate) compared with a moderate-carbohydrate diet (MD; approximately 48% carbohydrate) when tested during the luteal phase of the menstrual cycle. Six women cycled to exhaustion at approximately 80% maximal oxygen uptake (VO(2 max)) after each of the randomly assigned diet and exercise-tapering regimens. A biopsy was taken from the vastus lateralis before and after exercise in each trial. Preexercise muscle glycogen content was high after the MD (625.2 +/- 50.1 mmol/kg dry muscle) and 13% greater after the HCD (709.0 +/- 44.8 mmol/kg dry muscle). Postexercise muscle glycogen was low after both trials (MD, 91.4 +/- 34.5; HCD, 80.3 +/- 19.5 mmol/kg dry muscle), and net glycogen utilization during exercise was greater after the HCD. The subjects also cycled longer at approximately 80% VO(2 max) after the HCD vs. MD (115:31 +/- 10:47 vs. 106:35 +/- 8:36 min:s, respectively). In conclusion, aerobically trained women increased muscle glycogen content in response to a high-dietary carbohydrate intake during the luteal phase of the menstrual cycle, but the magnitude was smaller than previously observed in men. The increase in muscle glycogen, and possibly liver glycogen, after the HCD was associated with increased cycling performance to volitional exhaustion at approximately 80% VO(2 max).     

Hypohydration adversely affects lactate threshold in endurance athletes

The purpose of this investigation was to observe the effect of hypohydration (-4% body mass) on lactate threshold (LAT) in 14 collegiate athletes (8 men and 6 women; age, 20.9 +/- 0.5 years; height, 171.1 +/- 2.4 cm; weight, 64.8 +/- 2.3 kg; V(O)2 max, 62.8 +/- 1.9 ml x kg(-1) x min(-1); percentage of fat, 11.4 +/- 1.5%). Subjects performed 2 randomized, discontinuous treadmill bouts at a dry bulb temperature (T(db)) of 22 degrees C to volitional exhaustion in 2 states of hydration, euhydrated and hypohydrated. The hypohydrated condition was achieved in a thermally neutral environment (T(db), 22 degrees C; humidity, 45%), with exercise conducted at a moderate intensity as defined by rating of perceived exertion (RPE, approximately 12) 12-16 hours before testing. On average, subjects decreased 3.9% of their body mass before the hypohydration test. Blood lactate, hematocrit, V(O)2, minute ventilation (VE), R value, heart rate (HR), and RPE were measured during each 4-minute stage of testing. In the hypohydrated condition, LAT occurred significantly earlier during exercise and at a lower absolute V(O)2, VE, respiratory exchange ratio, RPE, and blood lactate concentration. Also, the blood lactate concentration was significantly lower in the hypohydrated condition (6.7 +/- 0.8 mmol) compared with the euhydrated condition (10.2 +/- 0.9 mmol) at peak exercise. There were no differences in HR or percentage of maximum HR at LAT nor did plots of V(CO2):V(O)2 reveal differences in bicarbonate buffering during exercise between the 2 conditions. From these results, we speculate that hypohydration did not significantly alter cardiovascular function or buffering capacity but did cause LAT to occur at a lower absolute exercise intensity.     

Exercise effects on chromium excretion of trained and untrained men consuming a constant diet

Chromium excretion of eight trained and five sedentary men was determined on rest days and after exercise to exhaustion at 90% of maximum O2 consumption (VO2max) to determine if degree of physical fitness affects urinary Cr losses. Subjects were fed a constant daily diet containing approximately 9 micrograms Cr/1,000 kcal. VO2max of the trained runners was in the good or above range based on their age and that of the sedentary subjects was average or below. While consuming the control diet, basal urinary Cr excretion of subjects who exercise regularly was significantly lower than that of the sedentary control subjects, 0.09 +/- 0.01 and 0.21 +/- 0.03 microgram/day (mean +/- SE), respectively. When subjects consumed self-chosen diets, basal urinary Cr excretion of the trained subjects was also significantly lower than that of the untrained subjects. Daily urinary Cr excretion of trained subjects was significantly higher on the day of a single exercise bout at 90% VO2max compared with nonexercise days, 0.12 +/- 0.02 and 0.09 +/- 0.01 microgram/day, respectively. Urinary Cr excretion of sedentary subjects was not altered after controlled exercise. These data demonstrate that basal urinary Cr excretion and excretion in response to exercise are related to VO2max and therefore degree of physical fitness.     

Comparison of cardiorespiratory responses of moderately trained men and women using two different treadmill protocols

In practice, the Bruce protocol is the most commonly used treadmill protocol to assess maximal oxygen consumption (V(.-)O2max). It has been suggested that a running protocol (e.g., Astrand) may elicit a comparatively higher V(.-)O2max and different cardiorespiratory responses when applied to moderately trained runners. Thus, the purpose of this study was to compare V(.-)O2max and other cardiorespiratory responses as elicited by the standard Bruce and a modified Astrand treadmill protocol in moderately trained runners. Fifteen women (age = 21 years, height = 171.5 cm, weight = 63 kg, and body fat = 18%) and 15 men (age = 26 years, height = 177 cm, weight = 72 kg, and body fat = 9%) who were moderately trained runners completed a standard Bruce and modified Astrand protocol (random order), separated by approximately 7 days. Heart rate, Borg ratings of perceived exertion, blood pressure, and pulmonary gas exchange variables were measured during the exercise tests using standard laboratory procedures. This study revealed V(.-)O2max values between the Bruce protocol (51.3 +/- 11.6 ml x kg(-1) x min(-1)) and modified Astrand (51.5 +/- 10.9 ml x kg(-1) x min(-1)) were not significantly different in either the men or the women. However, the Bruce protocol elicited significantly higher maximum treadmill time in men and maximum respiratory exchange ratio (RERmax) and maximum minute ventilation (VEmax) values in both genders. Conversely, the modified Astrand elicited a higher HRmax. These data suggest that V(.-)O2max in both moderately trained men and women runners is independent of treadmill protocol despite differences in HRmax, RERmax, and VEmax.     

Effects of a carbohydrate-, protein-, and ribose-containing repletion drink during 8 weeks of endurance training on aerobic capacity, endurance performance, and body composition

This study compared a carbohydrate-, protein-, and ribose-containing repletion drink vs. carbohydrates alone during 8 weeks of aerobic training. Thirty-two men (age, mean ± SD = 23 ± 3 years) performed tests for aerobic capacity (V(O2)peak), time to exhaustion (TTE) at 90% V(O2)peak, and percent body fat (%fat), and fat-free mass (FFM). Testing was conducted at pre-training (PRE), mid-training at 3 weeks (MID3), mid-training at 6 weeks (MID6), and post-training (POST). Cycle ergometry training was performed at 70% V(O2)peak for 1 hours per day, 5 days per week for 8 weeks. Participants were assigned to a test drink (TEST; 370 kcal, 76 g carbohydrate, 14 g protein, 2.2 g d-ribose; n = 15) or control drink (CON; 370 kcal, 93 g carbohydrate; n = 17) ingested immediately after training. Body weight (BW; 1.8% decrease CON; 1.3% decrease TEST from PRE to POST), %fat (5.5% decrease CON; 3.9% decrease TEST), and FFM (0.1% decrease CON; 0.6% decrease TEST) decreased (p ≤ 0.05), whereas V(O2)peak (19.1% increase CON; 15.8% increase TEST) and TTE (239.1% increase CON; 377.3% increase TEST) increased (p ≤ 0.05) throughout the 8 weeks of training. Percent decreases in %fat from PRE to MID3 and percent increases in FFM from PRE to MID3 and MID6 were greater (p ≤ 0.05) for TEST than CON. Overall, even though the TEST drink did not augment BW, V(O2)peak, or TTE beyond carbohydrates alone, it did improve body composition (%fat and FFM) within the first 3-6 weeks of supplementation, which may be helpful for practitioners to understand how carbohydrate-protein recovery drinks can and cannot improve performance in their athletes.     

Effects of recovery beverages on glycogen restoration and endurance exercise performance

The restorative capacities of a high carbohydrate-protein (CHO-PRO) beverage containing electrolytes and a traditional 6% carbohydrate-electrolyte sports beverage (SB) were assessed after glycogen-depleting exercise. Postexercise ingestion of the CHO-PRO beverage, in comparison with the SB, resulted in a 55% greater time to exhaustion during a subsequent exercise bout at 85% maximum oxygen consumption (VO(2)max). The greater recovery after the intake of the CHO-PRO beverage could be because of a greater rate of muscle glycogen storage. Therefore, a second study was designed to investigate the effects of after exercise CHO-PRO and SB supplements on muscle glycogen restoration. Eight endurance-trained cyclists (VO(2)max = 62.1 +/- 2.2 ml.kg(-1) body wt.min(-1)) performed 2 trials consisting of a 2-hour glycogen-depletion ride at 65-75% VO(2)max. Carbohydrate-protein (355 ml; approximately 0.8 g carbohydrate (CHO).kg(-1) body wt and approximately 0.2 g protein.kg(-1) body wt) or SB (355 ml; approximately 0.3 g CHO.kg(-1) body wt) was provided immediately and 2 hours after exercise. Trials were randomized and separated by 7-15 days. Ingestion of the CHO-PRO beverage resulted in a 17% greater plasma glucose response, a 92% greater insulin response, and a 128% greater storage of muscle glycogen (159 +/- 18 and 69 +/- 32 micromol.g(-1) dry weight for CHO-PRO and SB, respectively) compared with the SB (p < 0.05). These findings indicate that the rate of recovery is coupled with the rate of muscle glycogen replenishment and suggest that recovery supplements should be consumed to optimize muscle glycogen synthesis as well as fluid replacement.     

Oxygen deficit is related to the exercise time to exhaustion at maximal aerobic speed in middle distance runners

The purpose of this study was to show the relationship between oxygen deficit and the time to exhaustion (tlim) at maximal aerobic speed (MAS). The minimum speed that elicits VO(2max) was assumed to be the maximal aerobic speed (MAS). Fourteen subelite male runners (mean (SD: age = 27 +/- 5 yrs: VO(2max) = 68.9 +/- 4.6 ml kg (-1). min ( -1); MAS = 21.5 +/- 1 km h (-1) ) participated in the study. Each subject performed an incremental test to determine and MAS. The subjects ran to exhaustion at velocities corresponding to 100 and 120 % MAS. Oxygen deficit was measured during the period exercise to exhaustion at 120% of MAS and was calculated from the difference between O(2) demand and the accumulated O 2 uptake. The tlim values at 100% MAS were correlated with the values of tlim at 120% MAS (r = 0.52). The results reveal that the oxygen deficit was related to the time to exhaustion at MAS and indicate that the greater the oxygen deficit, the greater the time to exhaustion at MAS. It was also noted that the adjustment of oxygen consumption is related to the oxygen deficit. In other words, the subjects who have an important anaerobic capacity are the most efficient during an exercise time to exhaustion at MAS. The time limit values can be expressed by a linear regression making intervene MAS and anaerobic capacity. This conclusion could be of great interest in the training of middle distance runners.     

Estimated times to exhaustion at the PWC V O2, PWC HRT, and VT

The purpose of this study was to validate the Physical Working Capacity at the Heart Rate Threshold (PWC HRT) and Physical Working Capacity at the Oxygen Consumption Threshold (PWC V O2) tests by 1) using individual power vs. duration relationships to estimate the times to exhaustion (ETTE) at the PWC HRT and PWC V O2, and 2) comparing the power outputs and ETTE values of the PWC HRT and PWC V O2 with those of the ventilatory threshold (VT). Ten adults (mean age +/- SD = 23 +/- 1 years) performed an incremental test to exhaustion on a cycle ergometer for the determination of V O2 peak and VT. The subjects also performed four randomly ordered workbouts to exhaustion at different power outputs (ranging from 98 to 246 W) to determine the PWC V O2, PWC HRT, and power vs. duration relationship. Power curve analyses (y = ax b) were used to define the hyperbolic power vs. duration relationship for each subject and to determine the ETTE at the PWC V O2, PWC HRT, and VT. Two separate one-way repeated-measures analyses of variance indicated that there were significant differences among the fatigue thresholds (PWC V O2 > PWC HRT) and ETTE values (PWC HRT > PWC V O2): PWC V O2 (mean +/- SD = 147 +/- 43 W; ETTE = 21 +/- 3 minutes), PWCHRT (136 +/- 37 W; ETTE = 29 +/- 6 minutes), and VT (143 +/- 44 W; ETTE = 27 +/- 11 minutes). These findings were consistent with previous studies that indicated that the PWC HRT occurred at a lower power output than the PWC V O2. Furthermore, the PWC HRT was maintained for a mean of 29 minutes, whereas the PWC V O2 and VT were maintained for 21 and 27 minutes, respectively. These findings indicate that the ETTE values for the PWC V O2 and PWC HRT were substantially less than those suggested in previous studies.     

Diet-induced metabolic acidosis and the performance of high intensity exercise in man

The influence of four isolated periods of dietary manipulation upon high intensity exercise capacity was investigated in six healthy male subjects. Subjects consumed their 'normal' (N) diet (45 +/- 2% carbohydrate (CHO), 41 +/- 3% fat, 14 +/- 3% protein) for four days after which they exercised to voluntary exhaustion at a workload equivalent to 100% VO2max. Three further four-day periods of dietary manipulation took place; these were assigned in a randomised manner and each was followed by a high intensity exercise test. The dietary treatments were: a low CHO (3 +/- 1%), high fat (71 +/- 5%), high protein (26 +/- 3%) diet (HFHP); a high CHO (73 +/- 2%), low fat (12 +/- 2%), normal protein (15 +/- 1%) diet (HCLF); and a normal CHO (47 +/- 3%), low fat (27 +/- 2%), high protein (26 +/- 2%) diet (LFHP). Acid-base status and blood lactate concentration were measured on arterialised-venous blood at rest prior to dietary manipulation on each day of the different diets, immediately prior to exercise and at 2, 4, 6, 10 and 15 min post-exercise. Other metabolite concentrations were measured in the blood samples obtained prior to dietary manipulation and immediately prior to exercise. Exercise time to exhaustion after the HFHP diet (179 +/- 63 s) was shorter when compared with the N (210 +/- 65 s; p less than 0.01) and HCLF (219 +/- 69 s; p less than 0.05) diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Small weight gain is not associated with development of insulin resistance in healthy, physically active individuals.

We investigated whether weight gain alters insulin sensitivity and leptin levels in physically active individuals. Six (5 males and 1 female; age 26.6+/-1.0 years; BMI 21.5+/-0.9, body fat 17.4+/-2.2%) healthy individuals were enrolled in an overfeeding study (caloric surplus 22.5-26.5 kcal/kg/day) to achieve up to 10% weight gain over 4-6 week period with subsequent weight maintenance over additional 2 weeks. The participants were requested to maintain their previous physical activity which in all of them included 45-60 min training sessions at the gym 2-3 times/week. RESULTS: BMI increased to 23.4+/-0.9 (4.4 kg weight gain; p<0.05) and body fat to 21.0+/-2.8% (p < 0.05) over the period of active weight gain and remained stable over the two week period of weight maintenance; fasting plasma glucose and serum insulin remained unchanged; serum leptin nearly doubled (3.8+/-1.0 vs 6.4+/-1.9 ng/ mL; p < 0.05); insulin sensitivity, when expressed per kg of the total body (11.1+/-1.6 vs 12.4+/-2.1 mg/kg/min; p = NS), and lean body mass (13.4+/-1.9 vs 15.7+/-2.6 mg/kgLBM/min; p = NS), did not decrease after weight gain. On the contrary, insulin action had improved in 5 out of 6 individuals. In conclusion, the data presented in this preliminary report indicate that a small weight gain due to overfeeding in lean, healthy, physically active individuals is associated with rise in circulating leptin levels but not with worsening of insulin action.     

Effect of acute severe hypoxia on peripheral fatigue and endurance capacity in healthy humans

We hypothesized that severe hypoxia limits exercise performance via decreased contractility of limb locomotor muscles. Nine male subjects [mean +/- SE maximum O(2) uptake (Vo(2 max)) = 56.5 +/- 2.7 ml x kg(-1) x min(-1)] cycled at > or =90% Vo(2 max) to exhaustion in normoxia [NORM-EXH; inspired O(2) fraction (Fi(O(2))) = 0.21, arterial O(2) saturation (Sp(O(2))) = 93 +/- 1%] and hypoxia (HYPOX-EXH; Fi(O(2)) = 0.13, Sp(O(2)) = 76 +/- 1%). The subjects also exercised in normoxia for a time equal to that achieved in hypoxia (NORM-CTRL; Sp(O(2)) = 96 +/- 1%). Quadriceps twitch force, in response to supramaximal single (nonpotentiated and potentiated 1 Hz) and paired magnetic stimuli of the femoral nerve (10-100 Hz), was assessed pre- and at 2.5, 35, and 70 min postexercise. Hypoxia exacerbated exercise-induced peripheral fatigue, as evidenced by a greater decrease in potentiated twitch force in HYPOX-EXH vs. NORM-CTRL (-39 +/- 4 vs. -24 +/- 3%, P < 0.01). Time to exhaustion was reduced by more than two-thirds in HYPOX-EXH vs. NORM-EXH (4.2 +/- 0.5 vs. 13.4 +/- 0.8 min, P < 0.01); however, peripheral fatigue was not different in HYPOX-EXH vs. NORM-EXH (-34 +/- 4 vs. -39 +/- 4%, P > 0.05). Blood lactate concentration and perceptions of limb discomfort were higher throughout HYPOX-EXH vs. NORM-CTRL but were not different at end-exercise in HYPOX-EXH vs. NORM-EXH. We conclude that severe hypoxia exacerbates peripheral fatigue of limb locomotor muscles and that this effect may contribute, in part, to the early termination of exercise.     

Heart rate at lactate threshold and cycling time trials

The purpose of this investigation was to relate the heart rate and lactate response during simulated cycling time trials to incremental laboratory tests. Subjects (N = 10) were tested for .V(O2)max (56.1 +/- 2.4 ml.kg(-1).min(-1) ) and lactate threshold during incremental tests to exhaustion. Power output and heart rate (HR) at threshold was assessed by 3 methods: lactate deflection point (LaT), onset of blood lactate accumulation (OBLA), and the point on the lactate curve at maximal distance from a line connecting starting and finishing power output (Dmax). Power output determined at these thresholds was 282.1 +/-4.2, 302.5 +/-1.3, and 296.0 +/- 1.8 W, respectively, whereas HR was determined to be 88.6 +/- 0.01, 92.2 +/- 0.01, and 91.0 +/- 0.01% of maximum, respectively. Power output and HR were significantly lower for LaT than for the other 2 methods (p < 0.05). On separate visits, cyclists were instructed to perform maximum efforts for 30 and 60 minutes (30TT and 60TT). Lactate, HR, perceived exertion (RPE), and metabolic variables were measured during the time trials. During the 30TT, participants sustained a significantly higher lactate level (5.29 +/- 0.3 vs. 3.43 +/- 0.3 mmol.L(-1), p < 0.001), percentage of maximum HR (%HRmax) (90.3 +/- 0.02 vs. 84.6 +/- 0.01, p = 0.009), and overall RPE (15.5 +/- 0.5 vs. 14.4 +/- 0.5, p = 0.009), than during the 60TT. .V(O2) was not significantly different between the time trials; however, .V(CO2) (p = 0.008), ventilation (p = 0.004), and respiratory exchange ratio (p = 0.02) were significantly higher during the 30TT. Correlations were found between HR at LaT (r = 0.78), OBLA (r = 0.78), and Dmax (r = 0.71) for the 60TT, but not for the 30TT. These data suggest that despite a large variability in blood lactate during time trial efforts of 30 and 60 minutes (from 1.8 to 10.8 mmol.L(-1)), HR was consistently 90% of maximum for the 30TT and 85% for the 60TT. HR during the 30TT was approximated by HR corresponding to OBLA and Dmax, whereas HR during 60TT was approximated by LaT.     

Achievement of v[combining dot above]o2max criteria during a continuous graded exercise test and a verification stage performed by college athletes

ABSTRACT: Mier, CM, Alexander, RP, and Mageean, AL. Achievement of V[Combining Dot Above]O2max criteria during a continuous graded exercise test and a verification stage performed by college athletes. J Strength Cond Res 26(10): 2648-2654, 2012-The purpose of this study was to determine the incidence of meeting specific V[Combining Dot Above]O2max criteria and to test the effectiveness of a V[Combining Dot Above]O2max verification stage in college athletes. Thirty-five subjects completed a continuous graded exercise test (GXT) to volitional exhaustion. The frequency of achieving various respiratory exchange ratio (RER) and age-predicted maximum heart rate (HRmax) criteria and a V[Combining Dot Above]O2 plateau within 2 and 2.2 ml·kg·min (<2SD of the expected increase in V[Combining Dot Above]O2) were measured and tested against expected frequencies. After 10 minutes of active recovery, 10 subjects who did not demonstrate a plateau completed a verification stage performed at supramaximal intensity. From the GXT, the number of subjects meeting V[Combining Dot Above]O2max plateau was 5 (≤2 ml·kg·min) and 7 (≤2.2 ml·kg·min), RER criteria 34 (≥1.05), 32 (≥1.10), and 24 (≥1.15), HRmax criteria, 35 (<85%), 29 (<10 b·min) and 9 (HRmax). The V[Combining Dot Above]O2max and HRmax did not differ between GXT and the verification stage (53.6 ± 5.6 vs. 55.5 ± 5.6 ml·kg·min and 187 ± 7 vs. 187 ± 6 b·min); however, the RER was lower during the verification stage (1.15 ± 0.06 vs. 1.07 ± 0.07, p = 0.004). Six subjects achieved a similar V[Combining Dot Above]O2 (within 2.2 ml·kg·min), whereas 4 achieved a higher V[Combining Dot Above]O2 compared with the GXT. These data demonstrate that a continuous GXT limits the college athlete's ability to achieve V[Combining Dot Above]O2max plateau and certain RER and HR criteria. The use of a verification stage increases the frequency of V[Combining Dot Above]O2max achievement and may be an effective method to improve the accuracy of V[Combining Dot Above]O2max measurements in college athletes.