A three-week traditional altitude training increases hemoglobin mass and red cell volume in elite biathlon athletes

It is well known that altitude training stimulates erythropoiesis, but only few data are available concerning the direct altitude effect on red blood cell volume (RCV) in world class endurance athletes during exposure to continued hypoxia. The purpose of this study was to evaluate the impact of three weeks of traditional altitude training at 2050 m on total hemoglobin mass (tHb), RCV and erythropoietic activity in highly-trained endurance athletes. Total hemoglobin mass, RCV, plasma volume (PV), and blood volume (BV) from 6 males and 4 females, all members of a world class biathlon team, were determined on days 1 and 20 during their stay at altitude as well as 16 days after returning to sea-level conditions (800 m, only males) by using the CO-rebreathing method. In males tHb (14.0 +/- 0.2 to 15.3 +/- 1.0 g/kg, p < 0.05) and RCV (38.9 +/- 1.5 to 43.5 +/- 3.9 ml/kg, p < 0.05) increased at altitude and returned to near sea-level values 16 days after descent. Similarly in females, tHb (13.0 +/- 1.0 to 14.2 +/- 1.3 g/kg, p < 0.05) and RCV (37.3 +/- 3.3 to 42.2 +/- 4.1 ml/kg, p < 0.05) increased. Compared to their sea-level values, the BV of male and female athletes showed a tendency to increase at the end of the altitude training period, whereas PV was not altered. In male athletes, plasma erythropoietin concentration increased up to day 4 at altitude (11.8 +/- 5.0 to 20.8 +/- 6.0 mU/ml, p < 0.05) and the plasma concentration of the soluble transferrin receptor was elevated by about 11 % during the second part of the altitude training period, both parameters indicating enhanced erythropoietic activity. In conclusion, we show for the first time that a three-week traditional altitude training increases erythropoietic activity even in world class endurance athletes leading to elevated tHb and RCV. Considering the relatively fast return of tHb and RCV to sea-level values after hypoxic exposure, our data suggest to precisely schedule training at altitude and competition at sea level.     

Blood volume and hemoglobin mass in elite athletes of different disciplines

Although it is well known that athletes have considerably larger blood volumes than untrained individuals, there is no data available describing the blood volume variability among differently trained athletes. The first aim of the study was to determine whether athletes from different disciplines are characterized by different blood volumes and secondly to what extent the blood volume can possibly limit endurance performance within a particular discipline. We investigated 94 male elite athletes subdivided into the following 6 groups: downhill skiing (DHS), swimming (S), running (R), triathlon (TA), cycling junior (CJ) and cycling professional (CP). Two groups of untrained subjects (UT) and leisure sportsmen (LS) served as controls. Total hemoglobin (tHb) and blood volume (BV) were measured by the CO-rebreathing method. In comparison to UT (mean +/- SD: tHb 11.0 +/- 1.1 g/kg, BV 78.3 +/- 7.9 ml/kg) tHb and BV were about 35 - 40 % higher in the endurance groups R, TA, CJ, and CP (e. g. in CP: tHb 15.3 +/- 1.3 g/kg, BV 107.1 +/- 7.0 ml/kg). Within the endurance groups we found no significant differences. The anaerobic discipline DHS was characterized by very low BV (87.6 +/- 3.1 ml/kg). S had an intermediate position (BV 97.4 +/- 6.1 ml/kg), probably because of the immersion effects during training in the water. VO(2)max was significantly related to tHb and BV not only in the whole group but also in all endurance disciplines. The reasons for the different BVs are an increased adaptation to training stimuli and probably also individual predisposing genetic factors.     

Induced hypervolemia, cardiac function, VO2max, and performance of elite cyclists.

OBJECTIVE: To determine whether plasma volume expansion (PVexp) in elite endurance-trained (ET) cyclists, who already possess both a high blood volume (BV) and a high VO2max, leads to further enhancements in their cardiac function, VO2max, and endurance performance (time to exhaustion at 95% VO2max). METHODS: Nine male ET cyclists (V02max = 68.9 +/- 0.6 (SEM) mL x kg(-1) x min(-1)) were studied employing a double blind, cross-over design; i) before PVexp, ii) after sham PVexp (Sham), iii) after restoration of normocythemia, iv) after PVexp (6% dextran), and v) upon reestablishment of normocythemia. RESULTS: PVexp resulted in a 547 +/- 61 mL increase in BV (P < 0.05). Maximal cardiac output and maximal stroke volume were higher (P < 0.05) after PVexp, but the magnitude of these increases was only sufficient to counter the hemodilution effect (lowered O2 content) of PVexp, such that O2 transport, VO2max, and endurance performance remained unchanged. CONCLUSIONS: Expansion of BV in elite ET cyclists, who already possess a high BV, does not improve their VO2max and endurance performance. Elite ET athletes may already be at an optimal BV, which is at or near the limits of their diastolic reserve capacity.     

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.     

Noninvasive profiling of exercise-induced hypoxemia in competitive cyclists

The purpose of this case study was to profile maximal exercise and the incidence of exercise-induced arterial hypoxemia (EIAH) at three different altitudes within a group of competitive cyclists residing and training at 1,500 m. Ten male cyclists (category I or II professional road cyclists: ages, 27.7 +/- 6.1; weight, 69.9 +/- 6.9 kg) participated in three randomly assigned VO2max tests at sea level (SL), 1,500 m and 3000 m. Arterial saturation (pulse oximetry), ventilation, and power output (PO) were recorded continuously throughout the test. The SaO2 percentages at VO2max were significantly higher at SL when compared with 1500 m (p < 0.001); however, no difference was observed between VO2max values at either altitude (SL: 72.3 +/- 2.5 mL.kg-1.min-1, 1,500 m: 70.6 +/- 2.3 mL.kg-1.min-1), only when compared with 3,000 m: 63.9 +/- 2.1 mL.kg-1.min-1, p < 0.021. Percent SaO2 did correspond with maximal PO, and there was an overall main effect observed between POs as they continually declined from SL to 3,000 m (SL: 403.3 +/- 10.6 W; 1,500 m: 376.1 +/- 9.8 W; 3,000 m: 353.9 +/- 7.8 W; p < 0.0001). The results of this case study revealed that training and residing at 1,500 m did not reduce the incidence of EIAH during maximal exercise at 1,500 m for this selected group of cyclists.     

Sleep quality responses to atmospheric variation: Case studies of two elite female cyclists

Strategies applied during sleep to potentially enhance athlete performance use different atmospheric conditions. High altitude conditions are known to affect sleep adversely but the effects of mild-moderate altitude and O2 enrichment at mild altitude are uncertain. We performed case studies using two elite female road cyclists (mass and maximal aerobic power of 62 kg, 65.8 ml x kg(-1) x min(-1); 57 kg, 62.7 ml x kg(-1) x min(-1)) to examine changes in sleep for different atmospheric conditions applied throughout the preparation for, and during, an International Stage race. Conditions were: i) normoxia (600 m), ii) simulated moderate altitude (2650 m), iii) natural mild altitude (1380 m) and iv) O2 enrichment at mild altitude (30% O2@ 1300-1500 m). We measured respiratory disturbances, arousals, number of awakenings, blood oxygen saturation (SpO2), heart rate (HR), rapid eye movement sleep (REM) and deep sleep. Respiratory disturbances, SpO2 and HR responses were similar for both cyclists for all conditions. Compared with normoxia, both cyclists had somewhat reduced REM at natural mild altitude and moderate simulated altitude but differed in their REM and deep sleep responses to O2 enrichment. Compared with mild altitude, both showed increased awakenings and deep sleep with O2 enrichment. Only one cyclist clearly increased her REM sleep with O2 enrichment compared to mild altitude. Our data highlight two different sleep quality responses to atmospheric variation.     

The effect of training on running economy and performance in recreational athletes

PURPOSE: To analyze the effect of an 8-wk training program on the energy cost of running (C) and the performance of 16 recreational males. METHODS: A training group (TG, N = 8, 25.3 +/- 2.9 yr, 183.6 +/- 7.3 cm, 80.9 +/- 9.6 kg) and a control group (CG, N = 8, 24.3 +/- 3.7 yr, 179.3 +/- 6.1 cm, 75.5 +/- 8.0 kg) performed three two-stage tests (TST) at weeks 0, 4, and 8 (W0, W4, W8). Speeds of the first (v-slow) and second stage (v-fast) were 2.4 +/- 0.3 vs 2.5 +/- 0.4 m x s(-1) and 3.7 +/- 0.3 vs 3.9 +/- 0.4 m.s (TG vs CG), respectively. Maximum running time at v-fast (T) served as the measure of performance. C was calculated from oxygen uptake above rest, blood lactate concentration, and speed. The TG trained 3-5x wk(-1) at an HR of +/-10 beats of the HR measured at v-slow at W0 (161 +/- 12 bpm). The CG did not train. RESULTS: At W0, there were no significant differences between the groups in T (377 +/- 47 vs 335 +/- 34 s) and C (v-slow: 4.1 +/- 0.3 vs 4.3 +/- 0.4 J x kg(-1) x m(-1); v-fast: 4.2 +/- 0.4 vs 4.0 +/- 0.4 J x kg(-1) x m(-1)). In the CG, T and C remained almost unchanged at W4 (363 +/- 38 s, 4.0 +/- 0.4 J x kg(-1) x m(-1)) and at W8 (342 +/- 49 s, 4.0 +/- 0.3 J x kg(-1) x m(-1)). In the TG, T increased (P < 0.05) at W4 (469 +/- 45 s) and at W8 (591 +/- 109 s). At v-fast, also C increased (P < 0.05) at W8 (4.6 +/- 0.4 J x kg(-1) x m(-1)), whereas at v-slow, C decreased (P < 0.05) at W4 (3.7 +/- 0.4 J x kg(-1) x m(-1)) with no further change at W8 (3.7 +/- 0.4 J x kg(-1) x m(-1)). CONCLUSION: The training successfully increased running performance in terms of T. During the initial training period, C could be reduced at the speed predominantly used in training. However, at high running speeds, C may even increase if the corresponding running time is largely increased.     

Heart rate variability and performance at two different altitudes in well-trained swimmers

The aim of this study was to compare the effects of training at two different altitudes on heart rate variability (HRV) and performance in well-trained swimmers. Eight national-level male swimmers (age = 17.0 +/- 1.8 yrs, weight = 67.0 +/- 6.6 kg, height = 180.4 +/- 7.2 cm, V(O2max) = 60.4 +/- 4.0 ml.min(-1). kg(-1)) trained 17 days at 1200 m altitude (T1200), then, after 6 weeks of moderate training at sea level, reproduced the same training plan at 1850 m (T1850). The training was mainly aerobic with 86 % and 84 % < or = anaerobic threshold for T 1200 and T1850, respectively. Four HRV analysis tests were performed during T1200 and T1850, respectively (pre-test = day 0, test 2 = day 5, test 3 = day 11, post-test = day 17), in supine and standing position. Performance was measured over a 2000-m freestyle test at the altitude of 1200 m. A difference in HRV changes was observed between the two altitudes: during T1200, addition of parasympathetic and sympathetic activity in supine (TP(SU)) (p < 0.05) and standing (TP(ST)) (p < 0.05) position, supine parasympathetic activity (HF(SU)) (p < 0.05), and standing sympathetic activity (LF(ST)) (p < 0.05) were increased and the 2000-m performance was improved (p < 0.05) whereas none of these parameters was changed during T1850. Change in performance was correlated with increase in HF(SU) (r = 0.73; p < 0.05) and tended towards correlation with increase in LF(ST) (r = 0.73; p = 0.06). Conclusion: the same training loads induced a positive effect on HRV and performance at 1200 m but not at 1850 m. This may be the consequence of greater stress due to an interaction between greater hypoxic stimulus and the same training loads. These results highlight two opposing effects: aerobic training increases, whereas hypoxia decreases HF(SU), due to the correlation between HRV and changes in performance during altitude training.     

Arterial oxygen saturation and hemoglobin mass in postmenopausal untrained and trained altitude residents

Because of lacking ventilatory stimulation by sex hormones in postmenopausal women (PW), one might expect a lowered arterial oxygen saturation (S(O(2))) in hypoxia and therefore a stronger erythropoietic reaction than in young women (YW). Nine untrained (UTRPW) and 11 trained (TRPW) postmenopausal altitude residents (2600 m) were compared to 16 untrained (UTRYW) and 16 trained young women (TRYW) to check this hypothesis and to study the combined response to hypoxia and training. S(O(2)) was decreased in PW (89.2% +/- 2.2 vs. 93.6 +/- 0.7% in YW, p < 0.01). Hb mass, however, was similar in UT (UTRYW: 9.2 +/- 0.9 g/kg(1), UTRPW: 8.7 +/- 1.0 g/kg). But if body fat rise with age was excluded by relation to fat-free mass, Hb mass was increased in UTRPW (+1.2 g/kg, p < 0.05) compared to UTRYW. Training caused a similar rise of Hb mass in PW and YW (0.3 g/kg per mL/kg x min(1) rise in V(O(2peak))). There was no difference in erythropoietin among the groups. Ferritin was higher in PW than YW. The results show that female hormones and fitness level have to be considered in studies on erythropoiesis at altitude. The role of erythropoietin during chronic hypoxia still has to be clarified.     

Heart rate and performance parameters in elite cyclists: a longitudinal study

PURPOSE: This study was designed to evaluate the stability of target heart rate (HR) values corresponding to performance markers such as lactate threshold (LT) and the first and second ventilatory thresholds (VT1, VT2) in a group of 13 professional road cyclists (VO2max, approximately 75.0 mL x kg(-1) x min(-1)) during the course of a complete sports season. METHODS: Each subject performed a progressive exercise test on a bicycle ergometer (ramp protocol with workload increases of 25 W x min(-1)) three times during the season corresponding to the "active" rest (fall: November), precompetition (winter: January), and competition periods (spring: May) to determine HR values at LT, VT1 and VT2. RESULTS: Despite a significant improvement in performance throughout the training season (i.e., increases in the power output eliciting LT, VT1, or VT2), target HR values were overall stable (HR at LT: 154 +/- 3, 152 +/- 3, and 154 +/- 2 beats x min(-1); HR at VT1: 155 +/- 3, 156 +/- 3, and 159 +/- 3 beats x min(-1); and at VT2: 178 +/- 2, 173 +/- 3, and 176 +/- 2 beats x min(-1) during rest, precompetition, and competition periods, respectively). CONCLUSION: A single laboratory testing session at the beginning of the season might be sufficient to adequately prescribe training loads based on HR data in elite endurance athletes such as professional cyclists. This would simplify the testing schedule generally used for this type of athlete.     

The effects of exercise training intensification on glucose disposal in elite cyclists

To assess the effect of training on glucose disposal, we performed a longitudinal study of 11 elite cyclists before and after 4 months of intensive training compared to 11 sedentary subjects. Insulin sensitivity (SI) and glucose effectiveness (Sg) were measured using Bergman's minimal model. Sg includes basal insulin effectiveness (BIE) and a parameter termed glucose effectiveness at zero insulin (GEZI). After overnight fasting glucose was administered intravenously (0.5 g x kg(-1), 30% solution given over 3 min), and insulin (0.02 U x kg(-1), 1 -2U) was injected immediately after 19 min. Sg, SI and BIE, were significantly higher in elite cyclists both before and after training than in sedentary subjects (P < 0.01). However, the non-insulin-dependent component of Sg (GEZI) was higher only after the intensive training in the cyclists (3.31 +/- 0.67% x min(-1)) than in sedentary subjects (1.7 +/- 0.2% x min(-1), P < 0.02). We conclude that insulin sensitivity (SI) and glucose effectiveness (Sg) are higher in elite cyclists than in sedentary subjects and that these high and almost optimal values are not further improved by additional training. However, the improvement in GEZI, as reflected by the difference between post-training GEZI and sedentary control values, raises the possibility of an increase of the non-insulin-mediated mobilization of glucose transporters.     

Metabolic demands of intense aerobic interval training in competitive cyclists

PURPOSE: To investigate the metabolic demands of a single session of intense aerobic interval training in highly trained competitive endurance cyclists. METHODS: Seven cyclists (peak O2 uptake [VO2 peak] 5.14 +/- 0.23 L x min(-1), mean +/-SD) performed 8 x 5 min work bouts at 86 +/- 2% of VO2 peak with 60-s recovery. Muscle biopsies were taken from the vastus lateralis immediately before and after the training session, whereas pulmonary gas exchange and venous blood were sampled at regular intervals throughout exercise. RESULTS: Muscle glycogen concentration decreased from 501 +/- 91 to 243 +/- 51 mmol x kg (-1) dry mass (P < 0.01). High rates of total carbohydrate oxidation were maintained throughout exercise (340 micromol.kg(-1).min(-1)), whereas fat oxidation increased from 16 +/- 8 during the first to 25 +/- 13 micromol x kg(-1) x min(-1) during the seventh work bout (P < 0.05). Blood lactate concentration remained between 5 and 6 mM throughout exercise, whereas muscle lactate increased from 6 +/- 1 at rest to 32 +/- 12 mmol x kg(-1) d.m. immediately after the training session (P < 0.01). Although muscle pH decreased from 7.09 +/- 0.06 at rest to 7.01 +/- 0.03 at the end of the session (P < 0.01), blood pH was similar after the first and seventh work bouts (7.34). Arterial oxygen saturation (% S(P)O2) fell to 95.6 +/- 1% during the first work bout and remained at 94% throughout exercise: the 60-s rest intervals were adequate to restore % S(P)O2) to 97%. CONCLUSION: Highly trained cyclists are able to sustain high steady state aerobic power outputs that are associated with high rates of glycogenolysis and total energy expenditure similar to those experienced during a 60-min competitive ride.     

Hemoglobin mass after 21 days of conventional altitude training at 1816 m

The underlying mechanisms of altitude training are still a matter of controversial discussion but erythropoietic adaptations with an increase of total haemoglobin mass (tHb) have been shown in several studies, partly depending on an adequate hypoxic dose. The aim of this retrospective study was to investigate if a 3 weeks sojourn at moderate altitude (1816 m) with conventional training sessions (live and train at moderate altitude), especially under real and uncontrolled conditions, results in an increased tHb. tHb was measured in seven male cyclists competing at elite level (German national cycling team, U23 category) prior to the ascent to altitude and immediately after descent to sea-level. The athletes completed a 21 days altitude training camp living at 1816 m and training at 1800–2400 m during the competitive season. No significant difference was found in tHb after the altitude sojourn (prior 927 ± 109 g vs. 951 ± 113 g post, 95% CI ?13–61 g). Additionally, the analysis of red cell volume, plasma volume and blood volume or haemoglobin concentration [Hb] as well as haematocrit (Hct) did not reveal any significant changes. The data supports the theory that an adequate hypoxic dose is required for adaptations of the erythropoietic system with an increase of tHb and a threshold of approximately 2100–2500 m has to be exceeded.     

Inverse relationship between VO2max and economy/efficiency in world-class cyclists

PURPOSE: To determine the relationship that exists between VO2max and cycling economy/efficiency during intense, submaximal exercise in world-class road professional cyclists. METHODS Each of 11 male cyclists (26+/-1 yr (mean +/- SEM); VO2max: 72.0 +/- 1.8 mL x kg(-1) x min(-1)) performed: 1) a ramp test for O2max determination and 2) a constant-load test of 20-min duration at the power output eliciting 80% of subjects' VO2max during the previous ramp test (mean power output of 385 +/- 7 W). Cycling economy (CE) and gross mechanical efficiency (GE) were calculated during the constant-load tests. RESULTS: CE and GE averaged 85.2 +/- 2.3 W x L(-1) x min(-1) and 24.5 +/- 0.7%, respectively. An inverse, significant correlation was found between 1) VO2max (mL x kg(-0.32) x min(-1)) and both CE (r = -0.71; P = 0.01) and GE (-0.72; P = 0.01), and 2) VO2max (mL x kg(-1) x min(-1)) and both CE (r = -0.65; P = 0.03) and GE (-0.64; P = 0.03). CONCLUSIONS: A high CE/GE seems to compensate for a relatively low VO2max in professional cyclists.     

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.     

Level ground and uphill cycling ability in professional road cycling.

PURPOSE: To evaluate the physiological capacities and performance of professional road cyclists in relation to their morphotype-dependent speciality. METHODS: 24 world-class cyclists, classified as flat terrain (FT, N = 5), time trial (TT, N = 4), all terrain (AT, N = 6). and uphill (UH, N = 9) specialists, completed an incremental laboratory cycling test to assess maximal power output (Wmax), maximal oxygen uptake (VO2max), lactate threshold (LT), and onset of blood lactate accumulation (OBLA). RESULTS: UH had a higher frontal area (FA):body mass (BM) ratio (5.23 +/- 0.09 m2 x kg(-1) x 10(-3)) than FT and TT (P < 0.05). FT showed the highest absolute Wmax (481 +/- 18 W), and UH the highest Wmax relative to BM (6.47 +/- 0.33 W x kg(-1)). WLT and W(OBLA) values were significantly higher in FT (356 +/- 41 and 417 +/- 45 W) and TT (357 +/- 41 and 409 +/- 46 W) than in UH (308 +/- 46 and 356 +/- 41). Scaling of these values relative to FA and BM exponents 0.32 and 0.79 minimized group differences, but considerable differences among mean group values remained. FT and TT had the highest Wmax per FA unit (1300 +/- 62 and 1293 +/- 57 W x m2), whereas TT had the highest absolute W x kg(-0.32) and W x kg(-0.79), as well as W x kg(-0.32), W x kg(-0.79), and W x m2 at the LT and OBLA. CONCLUSIONS: i) Scaling of maximal and submaximal physiological values showed a performance advantage of TT over FT, AT, and UH in all cycling terrains and conditions; and ii) mass exponents of 0.32 and 1 were the most appropriate to evaluate level and uphill cycling ability, respectively, whereas absolute Wmax values are recommended for performance-prediction in short events on level terrain, and W(LT) and W(OBLA) in longer time trials and uphill cycling.     

Physiological changes following a 12 week gym based stair-climbing, elliptical trainer and treadmill running program in females

AIM: Despite the growing popularity in recent years of the elliptical trainer aerobic exercise modality the physiological changes induced following a training program using elliptical trainers remains unknown. The present study investigated the metabolic and cardiorespiratory improvements following a 12-week aerobic training program using elliptical trainer, treadmill or stair-climbing modalities. METHODS: Twenty-two moderately active females (28.6 +/- 5.3 y, 1.65 +/- 0.05 m) were randomly assigned to treadmill running (n=7), elliptical trainer (n=8) or stair-climber (n=7) groups and trained 3 days x week(-1) initially at 70-80% of maximum heart rate (HRmax) for 30 min, progressing to 80-90% HRmax for 40 min. Subjects performed incremental exercise to volitional exhaustion using an electronically loaded cycle ergometer before and upon completion of the program. In addition, subjects performed sub-maximal fixed load tests at 0, 4, 8 and 12 weeks, using ergometers specific to their exercise group. RESULTS: No significant inter-group differences were recorded for pre-training VO2max or VEmax. Significant (p<0.05) post-training increases in cycling VO2max and VEmax were observed for treadmill (mean +/- SEM, 40.7 +/- 2.2 vs 43.4 +/- 2.6 ml x kg(-1) x min(-1) and 82.9 +/- 5.1 vs 90.2 +/- 6.4 l x min(-1)), elliptical trainer (36.9 +/- 2.5 vs 39.6 +/- 2.4 ml x kg(-1) x min(-1) and 86.8 +/- 2.3 vs 92.5 +/- 4.1 l x min(-1)) and stair-climber (37.4 +/- 2.9 vs 39.2 +/- 3.1 ml x kg(-1) x min(-1) and 95.9 +/- 5.8 vs 97.4 +/- 5.8 l x min(-1)) modalities, however, the increases were not significantly different between groups. For all groups, sub-maximal HR significantly decreased from week 0 to 4, and from week 4 to 8. CONCLUSION: In moderately active females similar physiological improvements were observed using stair-climber, elliptical trainer and treadmill running when training volume and intensity were equivalent.     

Acclimation to intermittent hypobaric hypoxia modifies responses to cold at sea level

INTRODUCTION: Residence at high altitude modifies thremoregulatory responses to cold stress upon return to lower altitude. These changes are difficult to explain since several stresses related to high altitude may interact, including hypoxia, cold, solar radiation, and physical exertion. We hypothesized that adaptation to hypoxia without cold exposure would produce at least part of the observed changes. METHODS: Five men underwent acclimation to intermittent hypoxia (AIH) in a hypobaric chamber (8 h daily for 4 d, and 6 h on the last day, 4500 to 6000 m) at 24 degrees C. Cold stress responses were tested during a whole-body standard cold air test (1 degrees C, 2 h at rest at sea level) both before and after AIH. RESULTS: Increased reticulocyte counts and percentages confirmed acclimation to hypoxia after AIH. Changes in thermoregulation during the cold test included lower mean skin temperature after 60-80 min (18.8 +/- 0.7 degrees C vs. 19.4 +/- 0.7 degrees C); higher mean metabolic heat production (127 +/- 8 W x m(-2) vs. 118 +/- 6 W x m(-2)); and lower heat debt (7.7 +/- 1.3 kJ x kg(-1) vs. 10.3 +/- 1.2 kJ x kg(-1)), without significant change in rectal temperature. Time to onset for continuous shivering decreased after AIH (12 +/- 5 min vs. 21 +/- 6.3 min), and shivering activity occurred at higher mean skin but not rectal temperatures. CONCLUSION: AIH in comfortable ambient temperature leads to a normothermic-insulative-metabolic general cold adaptation. We conclude that AIH modifies the thermoregulatory responses to cold at sea level without cold exposure leading to a cross-adaptation.     

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.     

Trapezius muscle metabolism measured with NIRS in helicopter pilots flying a simulator

INTRODUCTION: This study examined metabolic and hemodynamic responses during night vision goggle (NVG) induced neck strain among military helicopter pilots. We hypothesized that near infrared spectroscopy (NIRS) would be capable of identifying metabolic differences in the trapezius muscles of pilots between simulated flights with and without NVG. METHODS: There were 33 pilots who were monitored on consecutive days during Day and NVG flight simulator missions. NIRS probes were attached bilaterally to the trapezius muscles at the C7 level to record total oxygenation index (TOI, %), total hemoglobin (tHb), oxyhemoglobin (HbO2), and deoxyhemoglobin (HHb). RESULTS: Significant differences in tHb were found between Day (0.51+/-2.31 micromol x cm (-1)) and NVG (4.14 +/- 2.74 micromol x cm(-1)) missions, and for HbO2 (Dayend 2.63+/-1.64 micromol x cm(-1); NVGend 5.77+/-1.98 micromol x cm(-1)). Significant left and right side differences between Day and NVG were found for tHb (NVGleit -1.83+/-2.55; NVGright 10.45+/-2.86 micromol x cm(-1)), HbO2 (NVGleft 1.77+/-1.90; NVGright 9.95+/-2.07 micromol x cm(-1)), and HHb (Dayleft -1.84+/-0.95; Dayright -2.32+/-0.87 micromol x cm (-1); NVGleft -3.60+/-1.05 micromol x cm(-1); NVGright 0.49+/-1.16 micromol x cm(-1). DISCUSSION: These results support NIRS's utility in assessing the significant metabolic and hemodynamic effects of NVG on neck musculature during real-time missions for 1) left and right side differences; and 2) Day vs. NVG missions. The additional mass of the NVG equipment does increase the metabolic stress of these muscles during simulated missions.