Allan G. Hahn

''Live high, train low'' does not change the total haemoglobin mass of male endurance athletes sleeping at a simulated altitude of 3000 m for 23 nights

Abstract The purpose of this study was to document the effect of 23 days of “live high, train low” on the haemoglobin mass of endurance athletes. Thirteen male subjects from either cycling, triathlon or cross-country skiing backgrounds participated in the study. Six subjects (HIGH) spent 8−10 h per night in a “nitrogen house” at a simulated altitude of 3000 m in normobaric hypoxia, whilst control subjects slept at near sea level (CONTROL, n = 7). Athletes logged their daily training sessions, which were conducted at 600 m. Total haemoglobin mass (as measured using the CO-rebreathing technique) did not change when measured before (D1 or D2) and after (D28) 23 nights of hypoxic exposure [HIGH 990 (127) vs 972 (97) g and CONTROL 1042 (133) vs 1033 (138) g, before and after simulated altitude exposure, respectively]. Nor was there any difference in the substantial array of reticulocyte parameters measured using automated flow cytometry prior to commencing the study (D1), after 6 (D10) and 15 (D19) nights of simulated altitude, or 1 day after leaving the nitrogen house (D28) when HIGH and CONTROL groups were compared. We conclude that red blood cell production is not stimulated in male endurance athletes who spend 23 nights at a simulated altitude of 3000 m.

Simulated moderate altitude elevates serum erythropoietin but does not increase reticulocyte production in well-trained runners

Abstract The purpose of this study was to investigate whether the modest increases in serum erythropoietin (sEpo) experienced after brief sojourns at simulated altitude are sufficient to stimulate reticulocyte production. Six well-trained middle-distance runners (HIGH, mean maximum oxygen uptake, V˙O2max = 70.2 ml · kg−1 · min−1) spent 8–11 h per night for 5 nights in a nitrogen house that simulated an altitude of 2650 m. Five squad members (CONTROL, mean V˙O2max = 68.9 ml · kg−1 · min−1) undertook the same training, which was conducted under near-sea-level conditions (600 m altitude), and slept in dormitory-style accommodation also at 600 m altitude. For both groups, this 5-night protocol was undertaken on three occasions, with a 3-night interim between successive exposures. Venous blood samples were measured for sEpo after 1 and 5 nights of hypoxia on each occasion. The percentage of reticulocytes was measured, along with a range of reticulocyte parameters that are sensitive to changes in erythropoiesis. Mean serum erythropoietin levels increased significantly (P < 0.01) above baseline values [mean (SD) 7.9 (2.4) mU · ml−1] in the HIGH group after the 1st night [11.8 (1.9) mU · ml−1, 57%], and were also higher on the 5th night [10.7 (2.2) mU · ml−1, 42%] compared with the CONTROL group, whose erythropoietin levels did not change. After athletes spent 3 nights at near sea level, the change in sEpo during subsequent hypoxic exposures was markedly attenuated (13% and −4% change during the second exposure; 26% and 14% change during the third exposure; 1st and 5th nights of each block, respectively). The increase in sEpo was insufficient to stimulate reticulocyte production at any time point. We conclude that when daily training loads are controlled, the modest increases in sEpo known to occur following brief exposure to a simulated altitude of 2650 m are insufficient to stimulate reticulocyte production.

The effect of altitude on cycling performance: a challenge to traditional concepts.

Acute exposure to moderate altitude is likely to enhance cycling performance on flat terrain because the benefit of reduced aerodynamic drag outweighs the decrease in maximum aerobic power [maximal oxygen uptake (V̇O2max)]. In contrast, when the course is mountainous, cycling performance will be reduced at moderate altitude.Living and training at altitude, or living in an hypoxic environment (~2500m) but training near sea level, are popular practices among elite cyclists seeking enhanced performance at sea level. In an attempt to confirm or refute the efficacy of these practices, we reviewed studies conducted on highly-trained athletes and, where possible, on elite cyclists. To ensure relevance of the information to the conditions likely to be encountered by cyclists, we concentrated our literature survey on studies that have used 2- to 4-week exposures to moderate altitude (1500 to 3000m). With acclimatisation there is strong evidence of decreased production or increased clearance of lactate in the muscle, moderate evidence of enhanced muscle buffering capacity (βm) and tenuous evidence of improved mechanical efficiency (ME) of cycling.Our analysis of the relevant literature indicates that, in contrast to the existing paradigm, adaptation to natural or simulated moderate altitude does not stimulate red cell production sufficiently to increase red cell volume (RCV) and haemoglobin mass (Hbmass). Hypoxia does increase serum erthyropoietin levels but the next step in the erythropoietic cascade is not clearly established; there is only weak evidence of an increase in young red blood cells (reticulocytes).Moreover, the collective evidence from studies of highly-trained athletes indicates that adaptation to hypoxia is unlikely to enhance sea level V̇O2max. Such enhancement would be expected if RCV and Hbmass were elevated.The accumulated results of 5 different research groups that have used controlled study designs indicate that continuous living and training at moderate altitude does not improve sea level performance of high level athletes. However, recent studies from 3 independent laboratories have consistently shown small improvements after living in hypoxia and training near sea level. While other research groups have attributed the improved performance to increased RCV and V̇O2max, we cite evidence that changes at the muscle level (βm and ME) could be the fundamental mechanism. While living at altitude but training near sea level may be optimal for enhancing the performance of competitive cyclists, much further research is required to confirm its benefit. If this benefit does exist, it probably varies between individuals and averages little more than 1%.

Physiological characteristics of successful mountain bikers and professional road cyclists

The aims of this study were to compare the physiological and anthropometric characteristics of successful mountain bikers and professional road cyclists and to re-examine the power-to-weight characteristics of internationally competitive mountain bikers. Internationally competitive cyclists (seven mountain bikers and seven road cyclists) completed the following tests: anthropometric measurements, an incremental cycle ergometer test and a 30 min laboratory time-trial. The mountain bikers were lighter (65.3 - 6.5 vs 74.7 - 3.8 kg, P = 0.01; mean - s ) and leaner than the road cyclists (sum of seven skinfolds: 33.9 - 5.7 vs 44.5 - 10.8 mm, P = 0.04). The mountain bikers produced higher power outputs relative to body mass at maximal exercise (6.3 - 0.5 vs 5.8 - 0.3 W·kg -1 , P = 0.03), at the lactate threshold (5.2 - 0.6 vs 4.7 - 0.3 W·kg -1 , P = 0.048) and during the 30 min time-trial (5.5 - 0.5 vs 4.9 - 0.3 W·kg -1 , P = 0.02). Similarly, peak oxygen uptake relative to body mass was higher in the mountain bikers (78.3 - 4.4 vs 73.0 - 3.4 ml·kg -1 ·min -1 , P = 0.03). The results indicate that high power-to-weight characteristics are important for success in mountain biking. The mountain bikers possessed similar anthropometric and physiological characteristics to previously studied road cycling uphill specialists.

Effects of a 12-day live high, train low camp on reticulocyte production and haemoglobin mass in elite female road cyclists

Abstract The aim of this study was to document the effect of “living high, training low” on the red blood cell production of elite female cyclists. Six members of the Australian National Womens road cycling squad slept for 12 nights at a simulated altitude of 2650 m in normobaric hypoxia (HIGH), while 6 team-mates slept at an altitude of 600 m (CONTROL). HIGH and CONTROL subjects trained and raced as a group throughout the 70-day study. Baseline levels of reticulocyte parameters sensitive to changes in erythropoeisis were measured 21 days and 1 day prior to sleeping in hypoxia (D1 and D20, respectively). These measures were repeated after 7 nights (D27) and 12 nights (D34) of simulated altitude exposure, and again 15 days (D48) and 33 days (D67) after leaving the altitude house. There was no increase in reticulocyte production, nor any change in reticulocyte parameters in either the HIGH or CONTROL groups. This lack of haematological response was substantiated by total haemoglobin mass measures (CO-rebreathing), which did not change when measured on D1, D20, D34 or D67. We conclude that in elite female road cyclists, 12 nights of exposure to normobaric hypoxia (2650 m) is not sufficient to either stimulate reticulocyte production or increase haemoglobin mass.

Reduced performance of male and female athletes at 580 m altitude

Abstract This study examined the effect of mild hypobaria (MH) on the peak oxygen consumption (O2peak) and performance of ten trained male athletes [ (SEM); O2peak = 72.4 (2.2) ml · kg−1 · min−1] and ten trained female athletes [O2peak = 60.8 (2.1) ml · kg−1 · min−1]. Subjects performed 5-min maximal work tests on a cycle ergometer within a hypobaric chamber at both normobaria (N, 99.33 kPa) and at MH (92.66 kPa), using a counter-balanced design. MH was equivalent to 580 m altitude. O2peak at MH decreased significantly compared with N in both men [− 5.9 (0.9)%] and women [− 3.7 (1.0)%]. Performance (total kJ) at MH was also reduced significantly in men [− 3.6 (0.8)%] and women [− 3.8 (1.2)%]. Arterial oxyhaemoglobin saturation (SaO2) at O2peak was significantly lower at MH compared with N in both men [90.1 (0.6)% versus 92.0 (0.6)%] and women [89.7 (3.1)% versus 92.1 (3.0)%]. While SaO2 at O2peak was not different between men and women, it was concluded that relative, rather than absolute, O2peak may be a more appropriate predictor of exercise-induced hypoxaemia. For men and women, it was calculated that 67–76% of the decrease in O2peak could be accounted for by a decrease in O2 delivery, which indicates that reduced O2 tension at mild altitude (580 m) leads to impairment of exercise performance in a maximal work bout lasting ≈ 5 min.

Glycerol hyperhydration improves cycle time trial performance in hot humid conditions

Abstract Eight competitive cyclists [mean peak oxygen consumption, (V˙O2peak) = 65 ml · min−1 · kg−1] undertook two 60-min cycle ergometer time trials at 32°C and 60% relative humidity. The time trials were split into two 30-min phases: a fixed-workload phase and a variable-workload phase. Each trial was preceded by ingestion of either a glycerol solution [1 g · kg−1 body mass (BM) in a diluted carbohydrate (CHO)-electrolyte drink] or a placebo of equal volume (the diluted CHO-electrolyte drink). The total fluid intake in each trial was 22 ml · kg−1 BM. A repeated-measures, double blind, cross over design with respect to glycerol was employed. Glycerol ingestion expanded body water by ≈600 ml over the placebo treatment. Glycerol treatment significantly increased performance by 5% compared with the placebo group, as assessed by total work in the variable-workload phase (P < 0.04). There were no significant differences in rectal temperature, sweat rate or cardiac frequency between trials. Data indicate that the glycerol-induced performance increase did not result from plasma volume expansion and subsequently lower core temperature or lower cardiac frequencies at a given power output as previously proposed. However, during the glycerol trial, subjects maintained a higher power output without increased perception of effort or thermal strain.

Practical precooling: Effect on cycling time trial performance in warm conditions

Abstract The purpose of this study was to compare the effects of two practical precooling techniques (skin cooling vs. skin + core cooling) on cycling time trial performance in warm conditions. Six trained cyclists completed one maximal graded exercise test ([Vdot]O2peak 71.4 ± 3.2 ml · kg−1 · min−1) and four ∼40 min laboratory cycling time trials in a heat chamber (34.3°C ± 1.1°C; 41.2% ± 3.0% rh) using a fixed-power/variable-power format. Cyclists prepared for the time trial using three techniques administered in a randomised order prior to the warm-up: (1) no cooling (control), (2) cooling jacket for 40 min (jacket) or (3) 30-min water immersion followed by a cooling jacket application for 40 min (combined). Rectal temperature prior to the time trial was 37.8°C ± 0.1°C in control, similar in jacket (37.8°C ± 0.3°C) and lower in combined (37.1°C ± 0.2°C, P < 0.01). Compared with the control trial, time trial performance was not different for jacket precooling (−16 ± 36 s, −0.7%; P = 0.35) but was faster for combined precooling (−42 ± 25 s, −1.8%; P = 0.009). In conclusion, a practical combined precooling strategy that involves immersion in cool water followed by the use of a cooling jacket can produce decrease in rectal temperature that persist throughout a warm-up and improve laboratory cycling time trial performance in warm conditions.

Physique traits of lightweight rowers and their relationship to competitive success

Objectives: Physique traits and their relationship to competitive success were assessed amongst lightweight rowers competing at the 2003 Australian Rowing Championships. Methods: Full anthropometric profiles were collected from 107 lightweight rowers (n = 65 males, n = 45 females) competing in the Under 23 and Open age categories. Performance assessments were obtained for 66 of these rowers based on results in the single sculls events. The relationship between physique traits and competitive success was then determined. Results: Lower body fat (heat time estimate −8.4 s kg−1, p<0.01), greater total body mass (heat time estimate −4.4 s kg−1, p = 0.03), and muscle mass (heat time estimate −10.2 s kg−1, p<0.01) were associated with faster 2000 m heat times. Conclusions: The more successful lightweight rowers were those who had lower body fat and greater total muscle mass.

Effect of simulated altitude during sleep on moderate-severity OSA

Objective:  These studies were conducted to test the hypothesis that isobaric hypoxia would switch OSA to central sleep apnoea (CSA).