Optimal time of arrival for performance at moderate altitude (1700 m)

PURPOSE: The time course of physiological exercise responses after acute ascent to moderate altitude was investigated. METHODS: Fifteen young male subjects (16.5 +/- 0.8 yr) completed one familiarization and then two further sea level sessions to determine sea level values (SL). Subjects were then tested 6 h (ALT1), 18 h (ALT2), and 47 h (ALT3) after arrival at 1700 m. Subjects completed a 5-min submaximal cycle test, shuttle run test, and 45-s repeated push-up test. Hemoglobin (Hb) and hematocrit (Hct) were measured. RESULTS: Cycle test heart rate (HR) was higher at ALT1 than SL (182 +/- 15 vs 177 +/- 16 b.min(-1), P < 0.01) but had returned to 177 +/- 13 and 176 +/- 12 b.min(-1) at ALT2 and ALT3, respectively. At ALT1, only five subjects completed the full 5 min. Postexercise plasma lactate was not different. Shuttle test HR was higher at ALT1 than SL (191 +/- 8 vs 185 +/- 14 b.min(-1), P = 0.01) but had returned to 185 +/- 10 and 183 +/- 16 b.min(-1) at ALT2 and ALT3. Shuttle run time (SRT) was 37% shorter at ALT1 than SL (251 +/- 134 vs 401 +/- 115 s, P < 0.001) and remained impaired at ALT2 and ALT3 (330 +/- 124 and 344 +/- 115 s, both P < 0.001 vs SL). There was a significant relationship between magnitude of increased HR and reduction in SRT between SL and ALT1 (r = 0.52, P < 0.05). Push-up HR, Hb, and Hct were not affected by altitude. CONCLUSIONS: These findings indicate that detrimental effects of acute ascent to 1700 m on exercise performance are greater after 6 h than after 18 or 47 h. Performance was not entirely restored to SL values even after 47 h, despite restoration of easily measured physiological parameters. The results suggest travel to moderate altitude should occur as early as is practical before competition.     

Carbohydrate supplementation and endurance performance of moderate altitude residents at 4300 m

Recent work from our laboratory demonstrated that carbohydrate supplementation (CHOS) during exercise improved prolonged time-trial (TT) performance of sea-level residents (SLR) living at 4300 m while they were in daily negative energy balance (- 1250 kcal x day (-1); [ ]). The purposes of the current study were to determine during initial exposure to 4300 m:1) whether CHOS also improves TT performance of moderate altitude residents (MAR) who are in energy balance and 2) if acclimatization to moderate elevations benefits TT performance. Fifteen Air Force Academy (AFA) active duty members (age: 30 +/- 1 yrs; mean +/- SE), who had been living at approximately 2000 m for 21 +/- 3 months performed a maximal-effort 720-kJ cycle TT at the AFA and at Pikes Peak (PP), CO, (4300 m) on days 1 (PP1) and 3 (PP3). Daily energy intake and expenditure were maintained similarly at the AFA and PP. At the start of the TTs at PP, and then every 15 min thereafter, 9 subjects drank a 10 % CHO solution (0.175 g x kg (-1) body weight) and 6 subjects drank a placebo (PLA) solution. All subjects were allowed to freely adjust the power output of the cycle ergometer and drank water AD LIBITUM. Performance time did not differ between groups on PP1 (CHOS vs. PLA; 101 +/- 8 vs. 116 +/- 10 min) or PP3 (95 +/- 8 vs. 107 +/- 12 min). For both groups, cycle times on PP1 and PP3 were longer compared to the AFA (p<0.01) and were improved from PP1 to PP3 (p<0.05). Exercise intensity (i.e., % peak oxygen uptake) was maintained similarly at approximately 62 % during the TTs at the AFA and PP. Blood glucose was 1.5 to 2.0 mmol x L (-1) higher for CHOS vs. PLA (p<0.01). It was concluded that CHOS provided no TT performance benefit for MAR at 4300 m when energy balance was maintained. However, the decrements in TT performance and exercise intensity were attenuated at 4300 m in MAR compared to those of SLR as a result of acclimatization attained while living for nearly 2 years at approximately 2000 m.     

Evaluation of stress responses to interval training at low and moderate altitudes

PURPOSE: The purpose of the present field study was to explore whether extensive interval training (IT) performed with a similar behavior of blood lactate (LA) at an altitude of 1800 m (ALT) and near sea level (SL) goes along with a comparable hormonal, metabolic, and acute phase response in highly trained endurance athletes. METHODS: Twelve distance runners (VO2 64.6 +/- 6.9 mL.kg(-1) ) performed IT (10 x 1000 m, 2-min rest) at SL with a running velocity (V) corresponding to 112% of the individual anaerobic threshold (IAT). After an acclimatization period of 7 d, IT was repeated with a lower V (107% IAT) at ALT. Blood samples were drawn at rest, 0, 0.3, 3, and 24 h after IT. LA during IT was similar at SL and ALT (5.4 +/- 1.3/5.3 +/- 1.2 mmol.L(-1)), whereas HR tended to be higher at SL. RESULTS: Postexercise rises in plasma noradrenaline (NA), NA sulfate, adrenaline, glucose, interleukin-6 (IL-6), and neutrophils were significantly more pronounced at ALT. The increase of cortisol and human growth hormone showed an insignificant trend toward higher values at ALT. A slight but significant increase of plasma erythropoietin was only apparent after IT at ALT. No differences between either condition were observed for exercise-related changes in free fatty acids, IL-8, lympho-, or monocyte counts. CONCLUSIONS: In spite of a matched accumulation pattern of LA between ALT and N, stress responses, such as sympathetic activation and hepatic glucose release, still appear to be greater at ALT. This additional impact of moderate ALT on the stress response to IT should be taken into account if repeated training sessions are performed within a short period of time.     

The role of the right ventricle during hypobaric hypoxic exercise: insights from patients after the Fontan operation

OBJECTIVES: The principal objective of this study was to examine the importance of the right ventricle for maximal systemic oxygen transport during exercise at high altitude by studying patients after the Fontan operation. BACKGROUND: High-altitude-induced hypoxia causes a reduction in maximal oxygen uptake. Normal right ventricular pump function may be critical to sustain cardiac output in the face of hypoxic pulmonary vasoconstriction. We hypothesized that patients after the Fontan operation, who lack a functional subpulmonary ventricle, would have a limited exercise capacity at altitude, with an inability to increase cardiac output. METHODS: We measured oxygen uptake (VO2, Douglas bag), cardiac output (Qc, C2H2 rebreathing), heart rate (HR) (ECG), blood pressure (BP) (cuff), and O2 Sat (pulse oximetry) in 11 patients aged 14.5+/-5.2 yr (mean +/- SD) at 4.7+/-1.6 yr after surgery. Data were obtained at rest, at three submaximal steady state workrates, and at peak exercise on a cycle ergometer. All tests were performed at sea level (SL) and at simulated altitude (ALT) of 3048 m (10,000 ft, 522 torr) in a hypobaric chamber. RESULTS: At SL, resting O2 sat was 92.6+/-4%. At ALT, O2 sat decreased to 88.2+/-4.6% (P < 0.05) at rest and decreased further to 80+/-6.3% (P < 0.05) with peak exercise. At SL, VO2 increased from 5.1+/-0.9 mL x kg(-1) x min(-1) at rest to 23.5+/-5.3 mL x kg(-1) x min(-1) at peak exercise and CI (Qc x m(-2)) increased from 3.3+/-0.7 L x m(-2) to 6.2+/-1.2 L x m(-2). VO2 peak, 17.8+/-4 mL x kg(-1) x min(-1) (P < 0.05), and CI peak, 5.0+/-1.5 L x m(-2) (P < 0.05), were both decreased at ALT. Remarkably, the relationship between Qc and VO2 was normal during submaximal exercise at both SL and ALT. However at ALT, stroke volume index (SVI, SV x m(-2)) decreased from 37.7+/-8.6 mL x min(-1) x m2 at rest, to 31.3+/-8.6 mL x min(-1) x m2 at peak exercise (P < 0.05), whereas it did not fall during sea level exercise. CONCLUSIONS: During submaximal exercise at altitude, right ventricular contractile function is not necessary to increase cardiac output appropriately for oxygen uptake. However, normal right ventricular pump function may be necessary to achieve maximal cardiac output during exercise with acute high altitude exposure.     

Hematological and physiological adaptations following 46 weeks of moderate altitude residence

Although acclimatization to moderate altitude (MA) is thought to be unnecessary or to require minimal adaptation, retrospective data from the U.S. Air Force Academy (USAFA), a military college located at 2210 m, suggested otherwise. To further examine the utility of USAFA as a model for MA acclimatization, a longitudinal experimental design was prospectively utilized to determine the magnitude and time course of selected hematological and performance parameters following 46 weeks at this unique MA setting. Incoming USAFA male freshmen (n=55) were divided into experimental groups based on prior residence at sea level (SL) or MA. Hematological and performance parameters were repeatedly assessed during their entire first year at MA. Hematological data consisted of a complete blood count (CBC) with reticulocyte parameters, as well as determination of serum levels of ferritin, erythropoietin, and soluble transferrin receptor (sTfR). Performance testing included aerobic (1.5-mile run) and physical (push-ups, sit-ups, pull-ups, and standing long jump) fitness tests, maximal aerobic capacity, and running economy. Significant (p<0.05; main effect) hematological differences between SL and MA subjects were observed for the majority of the study. MA subjects had a significantly higher hemoglobin concentration ([Hb], +5.5%), hematocrit (+2.8%), and serum ferritin (+59.0%) and significantly lower sTfR (-11.4%) values than their SL peers. Although both serum ferritin and sTfR demonstrated a significant altitude group x time interaction, [Hb] and hematocrit did not. A significant main effect of altitude without interaction was also observed for performance parameters, with SL subjects having a significantly lower Vo2peak (-5.9%), slower 1.5- mile run time (+5.4%), poorer running economy (+6.6%), and lower composite physical fitness test score (-13.9%) than MA subjects. These results suggest that complete acclimatization to 2210 m by former SL residents may require lengthy physiological adaptations, as both hematological and physical performance differences persisted between groups. Further research at this uniquely well controlled MA setting is warranted.     

Plasma sodium-osmotic dissociation and hormonal interaction with drinking-induced hypervolemia at 2800 m altitude

PURPOSE: To study hormonal factors that may account for the dissociation between beverage-induced plasma sodium p[Na+] and osmotic p[Osm] concentrations that appear to refute the high theoretical correlation between p[Na+] and p[Osm]. METHODS: Ten men (24 +/- SD 3 yr of age) sat reclining (head up) for 12 h in a chamber (21-23 degrees C dry bulb, 25-33% relative humidity) at 2800 m (9184 ft, 539 mm Hg) altitude (ALT), and at 321 m (1053 ft, 732 mm Hg) on the ground (GND). During 1000-1030 hours they consumed 3 fluids (12 ml x kg(-1),X = 948 ml x d(-1)) with large differences in sodium and osmotic contents: AstroAde (AA) with 185 mEq x L(-1) Na+ and 283 mOsm x kg(-1), Performance 1 (Shaklee) (P1) with 22 mEq x L(-1) Na+ and 365 mOsm kg(-1), or H2O at ALT; and only H2O on the GND. RESULTS: After drinking: plasma volume (PV) increased at 1200 hours by 8.3% (p < 0.05) with AA but was not significantly (NS) changed in the other sessions (Xdelta = +0.9%, range -0.9 to 2.8%); p[Na+] and p[Osm] were unchanged. Urinary rates and free-water clearances were attenuated with AA and P1 vs. those with H2O. Correlations between and among p[Na+] and p[Osm] suggest that the pNa+ ion is more tightly controlled than pOsm; and that there was no clear hormonal response that could account for this dissociation from theoretical considerations. CONCLUSIONS: There is significant dissociation between plasma sodium and osmotic concentrations after fluid intake. Induction and maintenance of hypervolemia requires increased (near isotonic) drink Na+ osmols rather than increased non-ionic osmols.     

Reproducibility of a laboratory-based 40-km cycle time-trial on a stationary wind-trainer in highly trained cyclists

The purpose of the present study was to examine the reproducibility of laboratory-based 40-km cycle time-trial performance on a stationary wind-trainer. Each week, for three consecutive weeks, and on different days, forty-three highly trained male cyclists (x +/- SD; age = 25 +/- 6 y; mass = 75 +/- 7 kg; peak oxygen uptake [VO (2)peak] = 64.8 +/- 5.2 ml x kg (-1) x min (-1)) performed: 1) a VO (2)peak test, and 2) a 40-km time-trial on their own racing bicycle mounted to a stationary wind-trainer (Cateye - Cyclosimulator). Data from all tests were compared using a one-way analysis of variance. Performance on the second and third 40-km time-trials were highly related (r = 0.96; p < 0.001), not significantly different (57 : 21 +/- 2 : 57 vs. 57 : 12 +/- 3 : 14 min:s), and displayed a low coefficient of variation (CV) = 0.9 +/- 0.7 %. Although the first 40-km time-trial (58 : 43 +/- 3 : 17 min:s) was not significantly different from the second and third tests (p = 0.06), inclusion of the first test in the assessment of reliability increased within-subject CV to 3.0 +/- 2.9 %. 40-km time-trial speed (km x h (-1)) was significantly (p < 0.001) related to peak power output (W; r = 0.75), VO (2)peak (l x min (-1); r = 0.53), and the second ventilatory turnpoint (l x min (-1); r = 0.68) measured during the progressive exercise tests. These data demonstrate that the assessment of 40-km cycle time-trial performance in well-trained endurance cyclists on a stationary wind-trainer is reproducible, provided the athletes perform a familiarization trial.     

Cardiac MRI of elite junior Olympic weight lifters

Cardiac magnetic resonance imaging was performed on 14 junior elite Olympic weight lifters and 14 controls (means +/- Se, age = 18.4 +/- 0.5 and 17.8 +/- 0.4 years, weight = 76.5 +/- 3.6 and 78.8 +/- 3.3 kg, % fat = 6.5% +/- 0.8% and 11.5% +/- 1.7%, respectively). Controls were individually matched to the lifters to within 2 years of age and 2.5 kg of body weight. Systolic (S) and diastolic (D) left posterior wall thickness (LPW), left ventricular short axis (LSA), left ventricular transverse long axis (LLA), spetal wall thickness (SW), right ventricular wall thickness (RWT), and right ventricular short axis (RSA) were determined. Variables were examined in absolute (mm), relative to body surface area (BSA, mm/m2), total body weight (BW, mm/kg), and lean body mass (LBM, mm/kg) terms. In absolute terms S LPW (21.1 +/- 1.7 vs 13.3 +/- 0.5 mm), S SW (15.3 +/- 1.3 vs 11.7 +/- 0.6 mm), and D LLA (75.2 +/- 1.6 vs 69.1 +/- 2.4 mm) were significantly greater and S LSA (23.4 +/- 2.4 vs 36.7 +/- 2.3 mm) and S LLA (46.5 +/- 3.7 vs 58.2 +/- 3.8 mm) were significantly less in the lifters vs the controls. S LPW/BW, S LPW/BSA, S LPW/LBM, S SW/BW, S SW/BSA, S SW/LBM, D LSA/BSA, and D LLA/BSA were significantly greater and S LSA/BW, B LSA/BSA, S LSA/LBM, S LLA/BSA, S LLA/LBM, and D SW/LBM were significantly less in the lifters than the controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term intermittent hypoxia increases O2-transport capacity but not VO2max

Long-term intermittent hypoxia, characterized by several days or weeks at altitude with periodic stays at sea level, is a frequently occurring pattern of life in mountainous countries demanding a good state of physical performance. The aim of the study was to determine the effects of a typical South American type of long-term intermittent hypoxia on VO2max at altitude and at sea level. We therefore compared an intermittently exposed group of soldiers (IH) who regularly (6 months) performed hypoxic-normoxic cycles of 11 days at 3550 m and 3 days at sea level with a group of soldiers from sea level (SL, control group) at 0 m and in acute hypoxia at 3550 m. VO2max was determined in both groups 1 day after arrival at altitude and at sea level. At altitude, the decrease in VO2max was less pronounced in IH (10.6 +/- 4.2%) than in SL (14.1 +/- 4.7%). However, no significant differences in VO2max were found between the groups either at sea level or at altitude, although arterial oxygen content (Ca(O(2) )) at maximum exercise was elevated (p < 0.001) in IH compared to SL by 11.7% at sea level and by 8.9% at altitude. This higher Ca(O(2) ) mainly resulted from augmented hemoglobin mass (IH: 836 +/- 103 g, SL: 751 +/- 72 g, p < 0.05) and at altitude also from increased arterial O(2)-saturation. In conclusion, acclimatization to long-term intermittent hypoxia substantially increases Ca(O(2) ), but has no beneficial effects on physical performance either at altitude or at sea level.     

Erythropoiesis and performance after two weeks of living high and training low in well trained triathletes

The purpose of our study was to evaluate hematologic acclimatization during 2 weeks of intensive normoxic training with regeneration at moderate altitude (living high-training low, LHTL) and its effects on sea-level performance in well trained athletes compared to another group of equally trained athletes under control conditions (living low - training low, CONTROL). Twenty-one triathletes were ascribed either to LHTL (n = 11; age: 23.0 +/- 4.3 yrs; VO 2 max: 62.5 +/- 9.7 [ml x min -1 x kg -1]) living at 1956 m of altitude or to CONTROL (n = 10; age: 18.7 +/- 5.6 yrs; VO 2 max: 60.5 +/- 6.7 ml x min -1 x kg -1) living at 800 m. Both groups performed an equal training schedule at 800 m. VO 2 max, endurance performance, erythropoietin in serum, hemoglobin mass (Hb tot, CO-rebreathing method) and hematological quantities were measured. A tendency to improved performance in LHTL after the camp was not significant (p < 0.07). Erythropoietin concentration increased temporarily in LHTL (Delta 14.3 +/- 8.7 mU x ml -1; p < 0.012). Hb tot remained unchanged in LHTL whereas was slightly decreased from 12.5 +/- 1.3 to 11.9 +/- 1.3g x kg -1 in CONTROL (p < 0.01). As the reticulocyte number tended to higher values in LHTL than in CONTROL, it seems that a moderate stimulation of erythropoiesis during regeneration at altitude served as a compensation for an exercise-induced destruction of red cells.     

Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage

INTRODUCTION: The purpose of this study was to determine whether endurance cycling performance and postexercise muscle damage were altered when consuming a carbohydrate and protein beverage (CHO+P; 7.3% and 1.8% concentrations) versus a carbohydrate-only (CHO; 7.3%) beverage. METHODS: Fifteen male cyclists (mean (.-)VO(2peak) = 52.6 +/- 10.3 mL x kg x min) rode a cycle ergometer at 75% (.-)VO(2peak) to volitional exhaustion, followed 12 - 15 h later by a second ride to exhaustion at 85% (.-)VO(2peak). Subjects consumed 1.8 mL x kg BW of randomly assigned CHO or CHO+P beverage every 15 min of exercise, and 10 mL x kg BW immediately after exercise. Beverages were matched for carbohydrate content, resulting in 20% lower total caloric content per administration of CHO beverage. Subjects were blinded to treatment beverage and repeated the same protocol seven to 14 d later with the other beverage. RESULTS: In the first ride (75% (.-)VO(2peak)), subjects rode 29% longer (P < 0.05) when consuming the CHO+P beverage (106.3 +/- 45.2 min) than the CHO beverage (82.3 +/- 32.6 min). In the second ride (85% (.-)VO(2peak)), subjects performed 40% longer when consuming the CHO+P beverage (43.6 +/- 12.5 min) than when consuming the CHO beverage (31.2 +/- 8.7 min). Peak postexercise plasma CPK levels, indicative of muscle damage, were 83% lower after the CHO+P trial (216.3 +/- 122.0 U x L) than the CHO trial (1318.1 +/- 1935.6 U x L). There were no significant differences in exercising levels of (.-)VO(2), ventilation, heart rate, RPE, blood glucose, or blood lactate between treatments in either trial. CONCLUSION: A carbohydrate beverage with additional protein calories produced significant improvements in time to fatigue and reductions in muscle damage in endurance athletes. Further research is necessary to determine whether these effects were the result of higher total caloric content of the CHO+P beverage or due to specific protein-mediated mechanisms.     

Adaptations to short-term high-fat diet persist during exercise despite high carbohydrate availability.

PURPOSE: Five days of a high-fat diet produce metabolic adaptations that increase the rate of fat oxidation during prolonged exercise. We investigated whether enhanced rates of fat oxidation during submaximal exercise after 5 d of a high-fat diet would persist in the face of increased carbohydrate (CHO) availability before and during exercise. METHODS: Eight well-trained subjects consumed either a high-CHO (9.3 g x kg(-1) x d(-1) CHO, 1.1 g x kg(-1) x d(-1) fat; HCHO) or an isoenergetic high-fat diet (2.5 g x kg(-1) x d(-1) CHO, 4.3 g x kg(-1) x d(-1) fat; FAT-adapt) for 5 d followed by a high-CHO diet and rest on day 6. On day 7, performance testing (2 h steady-state (SS) cycling at 70% peak O(2) uptake [VO(2peak)] + time trial [TT]) of 7 kJ x kg(-1)) was undertaken after a CHO breakfast (CHO 2 g x kg(-1)) and intake of CHO during cycling (0.8 g x kg(-1) x h(-1)). RESULTS: FAT-adapt reduced respiratory exchange ratio (RER) values before and during cycling at 70% VO(2peak); RER was restored by 1 d CHO and CHO intake during cycling (0.90 +/- 0.01, 0.80 +/- 0.01, 0.91 +/- 0.01, for days 1, 6, and 7, respectively). RER values were higher with HCHO (0.90 +/- 0.01, 0.88 +/- 0.01 (HCHO > FAT-adapt, P < 0.05), 0.95 +/- 0.01 (HCHO > FAT-adapt, P < 0.05)). On day 7, fat oxidation remained elevated (73 +/- 4 g vs 45 +/- 3 g, P < 0.05), whereas CHO oxidation was reduced (354 +/- 11 g vs 419 +/- 13 g, P < 0.05) throughout SS in FAT-adapt versus HCHO. TT performance was similar for both trials (25.53 +/- 0.67 min vs 25.45 +/- 0.96 min, NS). CONCLUSION: Adaptations to a short-term high-fat diet persisted in the face of high CHO availability before and during exercise, but failed to confer a performance advantage during a TT lasting approximately 25 min undertaken after 2 h of submaximal cycling.     

Changes in ventilatory threshold at high altitude: effect of antioxidants

PURPOSE: To investigate the effects of prolonged hypoxia and antioxidant supplementation on ventilatory threshold (VT) during high-altitude (HA) exposure (4300 m). METHODS: Sixteen physically fit males (25 +/- 5 yr; 77.8 +/- 8.5 kg) performed an incremental test to maximal exertion on a cycle ergometer at sea level (SL). Subjects were then matched on VO2peak, ventilatory chemosensitivity, and body mass and assigned to either a placebo (PL) or antioxidant (AO) supplement group in a randomized, double-blind manner. PL or AO (12 mg of beta-carotene, 180 mg of alpha-tocopherol acetate, 500 mg of ascorbic acid, 100 mug of selenium, and 30 mg of zinc daily) were taken 21 d prior to and for 14 d at HA. During HA, subjects participated in an exercise program designed to achieve an energy deficit of approximately 1400 kcal.d(-1). VT was reassessed on the second and ninth days at HA (HA2, HA9). RESULTS: Peak power output (Wpeak) and VO2peak decreased (28%) in both groups upon acute altitude exposure (HA2) and were unchanged with acclimatization and exercise (HA9). Power output at VT (WVT) decreased from SL to HA2 by 41% in PL, but only 32% in AO (P < 0.05). WVT increased in PL only during acclimatization (P < 0.05) and matched AO at HA9. Similar results were found when VT was expressed in terms of % Wpeak and % VO2peak. CONCLUSIONS: VT decreases upon acute HA exposure but improves with acclimatization. Prior AO supplementation improves VT upon acute, but not chronic altitude exposure.     

Reducing the dose of combined caffeine and ephedrine preserves the ergogenic effect

BACKGROUND: Ingestion of a combination of 5 mg x kg(-1) caffeine (C), and 1 mg x kg(-1) ephedrine (E) was reported to have an ergogenic effect on high intensity aerobic exercise performance, but 25% of the subjects experienced vomiting and nausea while engaging in hard exercise after the treatment. The present study was undertaken to investigate whether reduced levels of C+E would alleviate the problem and maintain the ergogenic effect. METHODS: Twelve healthy untrained male subjects completed four randomized and double-blind, cycle ergometer trials to exhaustion at a power output equivalent to approximately 85% Vo2peak 1.5-2 hours after ingesting a placebo (P) or a mixture of C+E in the following doses: 5 mg x kg(-1) of C plus 0.8 mg x kg(-1) of E (CLE); 4 mg x kg(-1) of C plus 1 mg x kg(-1) of E (LCE); or 4 mg x kg of C plus 0.8 mg x kg(-1) of E (LCLE). Trials were separated by 1 wk. Venous blood samples were obtained and analyzed for caffeine and ephedrine levels 1.5 h post-drug ingestion. Vo2, Vco2, VE, and RQ were measured every minute throughout the exhaustion ride. Heart rate and perceived exertion (RPE) were also recorded every 5 min and at the end of the exercise session. RESULTS: Plasma levels of C and E immediately before the exhaustion ride were (mean +/- SD): 38.7+/-5.2 micromol x L(-1) C, 1.285+/-0.275 micromol x L(-1) E in the CLE trial; 33.2+/-5.8 micromol x L(-1) C, 1.462+/-0.283 micromol x L(-1) E in the LCE trial; 33.0+/-2.9 micromol x L(-1) C, 1.229+/-0.202 micromol x L(-1) E in the LCLE trial. The times to exhaustion for the treatment trials (CLE = 27.5+/-12.4 min, LCE = 27.6+/-10.9 min, LCLE = 28.2+/-9.3 min) were similar and were significantly greater than placebo (p = 17.0+/-3.0 min). The drugs did not affect Vo2, Vco2, or VE. Heart rates were significantly higher for the drug trials while RPE was lower compared with P. No incidents of nausea or vomiting occurred with the lowest dose of the C+E, LCLE. CONCLUSIONS: A lower dose of C+E resulted in an ergogenic effect similar in magnitude to that reported previously with a higher dose, and with a reduced incidence of negative side effects.     

Comparison of isokinetic peak force and work parameters in youth with and without mental retardation.

PURPOSE: The purpose of this study was to compare isokinetic knee (flexion and extension) strength of nondisabled youth (ND; 15 males, 15 females; males = 12.7 +/- 2 yr; females = 13.4 +/- 2 yr) and youths with mental retardations (MR, 17 males + 13 females; male = 14.7 +/- 2 yr; females = 13.6 +/- 2 yr). METHODS: Subjects were evaluated on a Kin-Con isokinetic dynamometer at a speed of 60 degrees x s(-1). Parameters measured were peak torque (PT), time to PT, angle of PT, total work (W), and PT hamstrings/quadriceps (HQ) ratio. Peak torque was also corrected by weight (BW) and body mass index (BMI). Peak torque, time to peak torque, angle of peak torque, and total work were analyzed using a 2 x 2 x 2 (groups x gender x muscle) repeated measures analysis of variance (MANOVA). Flexion/extension ratios, BMI, and BW were analyzed by separate 2 x 2 (group x gender) analyses of variance. RESULTS: Results of this study suggest that: 1) while gender differences are apparent in the ND population they are not evident in individuals with MR; 2) knee extension strength is higher for ND youth, thus causing lower PT HQ ratios when compared with those in youth with MR; 3) angle of PT and time to PT were similar among groups; and 4) total work performed is lower in individuals with MR. CONCLUSIONS: It was concluded that parameters of strength production in individuals with MR are not consistent and do not follow the same pattern as their nonretarded peers.     

Elevated plasma cholecystokinin at high altitude: metabolic implications for the anorexia of acute mountain sickness

The aims of the present study were to measure the satiety neuropeptide cholecystokinin (CCK) in humans at terrestrial high altitude to investigate its possible role in the pathophysiology of anorexia, cachexia, and acute mountain sickness (AMS). Nineteen male mountaineers aged 38 +/- 12 years participated in a 20 +/- 5 day trek to Mt. Kanchenjunga basecamp (BC) located at 5,100 m, where they remained for 7 +/- 5 days. Subjects were examined at rest and during a maximal exercise test at sea-level before/after the expedition (SL1/SL2) and during the BC sojourn. There was a mild increase in Lake Louise AMS score from 1.1 +/- 1.2 points at SL1 to 2.3 +/- 2.3 points by the end of the first day at BC (P < 0.05). A marked increase in resting plasma CCK was observed on the morning of the second day at BC relative to sea-level control values (62.9 +/- 42.2 pmol/L(-1) vs. SL1: 4.3 +/- 8.3 pmol/L(-1), P < 0.05 vs. SL2: 26.5 +/- 25.2 pmol/L(-1), P < 0.05). Maximal exercise increased CCK by 78.5 +/- 24.8 pmol/L(-1), (P < 0.05 vs. resting value) during the SL1 test and increased the plasma concentration of non-esterified fatty acids and glycerol at BC (P < 0.05 vs. SL1/SL2). The CCK response was not different in five subjects who presented with anorexia on Day 2 compared with those with a normal appetite. While there was no relationship between the increase in CCK and AMS score at BC, a more pronounced increase in resting CCK was observed in subjects with AMS (> or =3 points at the end of Day 1 at BC) compared with those without (+98.9 +/- 1.4 pmol/L(-1) vs. +67.6 +/- 37.2 pmol/L(-1), P < 0.05). Caloric intake remained remarkably low during the stay at BC (8.9 +/- 1.4 MJ.d(-1)) despite a progressive decrease in total body mass (-4.5 +/- 2.1 kg after 31 +/- 13 h at BC, P < 0.05 vs. SL1/SL2), which appeared to be due to a selective loss of torso adipose tissue. These findings suggest that the satiogenic effects of CCK may have contributed to the observed caloric deficit and subsequent cachexia at high altitude despite adequate availability of palatable foods. The metabolic implications of elevated CCK in AMS remain to be elucidated.     

Metabolic demands of body armor on physical performance in simulated conditions

The purpose of this study was to examine physical work performance, energy cost, and physiological fatigue in military personnel during simulated operational conditions. Using a within-subject, repeated-measures design, 34 military personnel volunteered to undergo two experimental conditions: with body armor (BA+) and without BA (BA-). Subjects walked on a treadmill for 30 minutes and completed a physical performance battery during each of two sessions, which were separated by > or = 5 days. Subjects with BA+ as compared with BA- had significantly greater increases in: oxygen uptake (VO2) at slow (16.8 +/- 1.5 vs. 18.8 +/- 1.7 mL x kg(-1) x min(-1)) and moderate paces (34.8 +/- 3.9 vs. 40.8 +/- 5.0 mL x kg(-1) x min(-1)); blood lactate at a moderate pace (4.0 +/- 2.4 vs. 6.7 +/- 2.6 mmol/L); heart rate at slow (107 +/- 14 vs. 118 +/- 16 beats per minute) and moderate paces (164 +/- 16 vs. 180 +/- 13 beats per minute); and ratings of perceived physical exertion at slow (8.4 +/- 1.5 vs. 10.4 +/- 1.8) and moderate paces (14.3 +/- 2.3 vs. 16.7 +/- 2.1). Physical tasks were significantly affected by BA: under BA+, men performed 61% fewer pull-ups and women's hang time was reduced by 63%; stair stepping was reduced by 16% for both men and women. BA significantly impacted the physical work capacity of militarily relevant tasks. Specifically, wearing BA significantly increased VO2 when walking at both slow and moderate paces. The potential for physical exhaustion is high and performance of physical tasks is markedly impaired when wearing BA.     

Hematological and lipid profile changes in sea-level natives after exposure to 3550-m altitude for 8 months

The aim of this epidemiological study was to determinate the effects on hematological and lipid profile in a young group of newcomers to altitude after being exposed chronically for 8 months to 3550 m (n = 50), age 17.8 +/- 0.7; and not overweight, BMI 22.9 +/- 0.5). Readings taken at altitude on day 1 and on month 8 were hematocrit (Hct, %), hemoglobin (Hb, g/dL), Sa(O(2)), total leukocyte and subset count (mm(3), %), and lipid profile (mg/dL). The same measurements were taken in a comparative group (CG) at sea level (SL). At altitude, elevations of Hct (44.6 +/- 0.4; 51.2 +/- 0.4) and Hb (15.5 +/- 0.1; 17.3 +/- 0.1) were seen (p < 0.001) and none with Hb >/= 21 g/dL. No correlation was observed between Hb and Sa(O(2)), r = 0.11, p > 0.05. Total leukocyte count showed no changes (6037 +/- 74; 6002 +/- 43), but a relative neutropenia (55.2 + -1.5; 50.6 + -1.3) and lymphocytosis (34.2 + 1; 42.4 + 1, p < 0.001) between periods were found and also when compared to SL. Also, an inverse relationship between Sa(O(2)) and total leukocytes on month 8 (r = 0.46; r(2) = 0.204), suggesting a probable representation of a hypoxia effect. Total cholesterol (153.8 +/- 4.5; 157.3 +/- 5.1; p, ns) showed no changes, but a mild decrease of LDL-cholesterol (88.4 +/- 3.3; 81.0 +/- 3.9; p < 0.05), and a rise in triglycerides (121.6 +/- 10.9; 178.8 +/- 11.7; p < 0.001) was found. Changes observed in leukocytes subset count and triglycerides could suggest a contributory role of hypoxic conditions, raising some future epidemiological concerns regarding immune system and fatty acid behaviour at altitude.     

Interval training program optimization in highly trained endurance cyclists

PURPOSE: The purpose of this study was to examine the influence of three different high-intensity interval training (HIT) regimens on endurance performance in highly trained endurance athletes. METHODS: Before, and after 2 and 4 wk of training, 38 cyclists and triathletes (mean +/- SD; age = 25 +/- 6 yr; mass = 75 +/- 7 kg; VO(2peak) = 64.5 +/- 5.2 mL x kg(-1) min(-1)) performed: 1) a progressive cycle test to measure peak oxygen consumption (VO(2peak)) and peak aerobic power output (PPO), 2) a time to exhaustion test (T(max)) at their VO(2peak) power output (P(max)), as well as 3) a 40-km time-trial (TT(40)). Subjects were matched and assigned to one of four training groups (G(2), N = 8, 8 x 60% T(max) at P(max), 1:2 work:recovery ratio; G(2), N = 9, 8 x 60% T(max) at P(max), recovery at 65% HR(max); G(3), N = 10, 12 x 30 s at 175% PPO, 4.5-min recovery; G(CON), N = 11). In addition to G(1), G(2), and G(3) performing HIT twice per week, all athletes maintained their regular low-intensity training throughout the experimental period. RESULTS: All HIT groups improved TT(40) performance (+4.4 to +5.8%) and PPO (+3.0 to +6.2%) significantly more than G(CON) (-0.9 to +1.1%; P < 0.05). Furthermore, G(1) (+5.4%) and G(2) (+8.1%) improved their VO(2peak) significantly more than G(CON) (+1.0%; P < 0.05). CONCLUSION: The present study has shown that when HIT incorporates P(max) as the interval intensity and 60% of T(max) as the interval duration, already highly trained cyclists can significantly improve their 40-km time trial performance. Moreover, the present data confirm prior research, in that repeated supramaximal HIT can significantly improve 40-km time trial performance.     

Physiological and performance responses to a 6-day taper in middle-distance runners: influence of training frequency

The purpose of this investigation was to examine the influence of training frequency on performance and some physiological responses during a 6-day taper. After 18 weeks of training, 9 male middle-distance runners were assigned to a high frequency taper (HFT, n = 5) or a moderate frequency taper (MFT, n = 4), consisting of training daily or resting every third day of the taper. Taper consisted of an 80% nonlinear progressive reduction in high intensity interval training. Blood samples were obtained, and 800 m performance and peak blood lactate ([La] peak ) measured before and after taper. Performance improved significantly after HFT (121.8 +/- 4.7 vs 124.2 +/- 4.9 s, p < 0.05), but not after MFT (126.6 +/- 2.8 vs 127.1 +/- 2.1 s). Neutrophils (2.89 +/- 0.68 vs 2.56 +/- 0.61 10 (3) x mm(-3)), granulocytes (3.08 +/- 0.70 vs 2.77 +/- 0.66 10 (3) x mm(-3)), haptoglobin (79.7 +/- 47.9 vs 60.7 +/- 33.6 mg x dl(-1)), total testosterone (7.39 +/- 1.67 vs 5.52 +/- 0.88 microg x l(-1)) and [La] peak (15.5 +/- 1.5 vs 14.4 +/- 2.0 mmol x l(-1)) significantly increased with taper. [La] peak correlated with performance time before taper (r = -0.76, p < 0.05), and change in [La] peak with change in serum cortisol (r = -0.75, p < 0.05) and total testosterone:cortisol ratio (r = 0.82, p < 0.01). In conclusion, training daily during a 6-day taper brought about significant performance gains, whereas resting every third day did not. High [La] peak and a hormonal milieu propitious to anabolic processes seemed to be necessary for optimum performance.