Increased Hypoxic Dose After Training at Low Altitude with 9h Per Night at 3000m Normobaric Hypoxia.

This study examined effects of low altitude training and a live-high: train-low protocol (combining both natural and simulated modalities) on haemoglobin mass (Hbmass), maximum oxygen consumption (VO2max), time to exhaustion, and submaximal exercise measures. Eighteen elite-level race-walkers were assigned to one of two experimental groups; lowHH (low Hypobaric Hypoxia: continuous exposure to 1380 m for 21 consecutive days; n = 10) or a combined low altitude training and nightly Normobaric Hypoxia (lowHH+NHnight: living and training at 1380 m, plus 9 h.night(-1) at a simulated altitude of 3000 m using hypoxic tents; n = 8). A control group (CON; n = 10) lived and trained at 600 m. Measurement of Hbmass, time to exhaustion and VO2max was performed before and after the training intervention. Paired samples t-tests were used to assess absolute and percentage change pre and post-test differences within groups, and differences between groups were assessed using a one-way ANOVA with least significant difference post-hoc testing. Statistical significance was tested at p < 0.05. There was a 3.7% increase in Hbmass in lowHH+NHnight compared with CON (p = 0.02). In comparison to baseline, Hbmass increased by 1.2% (±1.4%) in the lowHH group, 2.6% (±1.8%) in lowHH+NHnight, and there was a decrease of 0.9% (±4.9%) in CON. VO2max increased by ~4% within both experimental conditions but was not significantly greater than the 1% increase in CON. There was a ~9% difference in pre and post-intervention values in time to exhaustion after lowHH+NH-night (p = 0.03) and a ~8% pre to post-intervention difference (p = 0.006) after lowHH only. We recommend low altitude (1380 m) combined with sleeping in altitude tents (3000 m) as one effective alternative to traditional altitude training methods, which can improve Hbmass. Key pointsIn some countries, it may not be possible to perform classical altitude training effectively, due to the low elevation at altitude training venues. An additional hypoxic stimulus can be provided by simulating higher altitudes overnight, using altitude tents.Three weeks of combined (living and training at 1380 m) and simulated altitude exposure (at 3000 m) can improve haemoglobin mass by over 3% in comparison to control values, and can also improve time to exhaustion by ~9% in comparison to baseline.We recommend that, in the context of an altitude training camp at low altitudes (~1400 m) the addition of a relatively short exposure to simulated altitudes of 3000 m can elicit physiological and performance benefits, without compromise to training intensity or competition preparation. However, the benefits will not be greater than conducting a traditional altitude training camp at low altitudes.

High-level performances following low altitude training and tapering in warm environments in elite racewalkers.

Current guidelines for prolonged altitude exposure suggest altitude levels ranging from 2000 to 2500 m to optimize an increase in total hemoglobin mass (Hbmass). However, natural low altitude locations (<2000 m) remain popular, highlighting the interest to investigate any possible benefit of low altitude camps for endurance athletes. Ten elite racewalkers (4 women and 6 men) underwent a 4-week "live high-train high" (LHTH) camp at an altitude of 1720 m (PIO2 = 121 mmHg; 20.1°C; 67% relative humidity [RH]), followed by a 3-week tapering phase (20 m; PIO2 = 150 mmHg; 28.3°C; 53% RH) in preparation for the World Athletics Championships (WC). Venous blood samples were withdrawn weekly during the entire observation period. In addition, blood volumes were determined weekly by carbon monoxide rebreathing during altitude exposure and 2 weeks after return to sea level. High-level performances were achieved at the WC (five placings among the Top 10 WC races and three all-time career personal bests). A slight but significant increase in absolute (+1.7%, p = 0.03) and relative Hbmass (+2.3%, p = 0.02) was observed after 4-week LHTH. In addition, as usually observed during LHTH protocols, weekly training distance (+28%, p = 0.02) and duration (+30%, p = 0.04) significantly increased during altitude compared to the pre-LHTH period. Therefore, although direct causation cannot be inferred, these results suggest that the combination of increased training load at low altitudes with a subsequent tapering period in a warm environment is a suitable competition-preparation strategy for elite endurance athletes.

The Temporal Effects of Altitude and Low Energy Availability Manipulation on Resting Metabolic Rate in Female Race Walkers.

PURPOSE: To investigate the temporal effects of ~1,800 m altitude exposure and energy availability (EA) manipulation on resting metabolic rate (RMR). METHODS: Twenty elite female race walkers underwent a 3-week training camp at an altitude of ~1,800 m. During the first two weeks, athletes consumed a high EA (HEA) diet of 45 kcal·kg fat free mass (FFM) -1 ·day -1 . During the final week, half the athletes consumed a low EA (LEA) diet of 15 kcal·kg FFM -1 ·day -1 while the others continued on a HEA diet. Athletes followed individualized training plans throughout the study. To assess the effect of altitude on RMR, athletes in the HEA group had RMR measured at baseline (~580 m) prior to altitude exposure (Pre-alt), at 36-hours (36 h-alt), 2 weeks (Wk2-alt) and 3 weeks into altitude exposure (Wk3-alt), and at 36 hours post-altitude exposure at ~580 m (36 h-post). To assess the effect of LEA exposure on RMR while at altitude, athletes in the LEA group underwent RMR measurements at Pre-alt and before (Wk2-alt) and after the 7-days of LEA (Wk3-alt). RESULTS: Compared to Pre-alt, the RMR of HEA athletes was increased at 36 h-alt (+5.3 ± 3.1%; p = 0.026) and Wk2-alt (+4.9 ± 4.9%; p = 0.049), but was no longer elevated at Wk3-alt (+1.7 ± 4.2%; p = 0.850). The RMR of HEA athletes at 36 h-post was lower than all timepoints at altitude (p < 0.05) but was not different from Pre-alt (-3.9 ± 7.2%; p = 0.124). The 7-day period of LEA exposure at altitude did not affect RMR (p = 0.347). CONCLUSIONS: RMR was transiently increased with ~1,800 m altitude exposure in female athletes and was unaffected by short-term LEA. However, the altitude-induced increase was small (~25-75 kcal/day) and was unlikely to have clinically significant implications for daily energy requirements.

Competing in Hot Conditions at the Tokyo Olympic Games: Preparation Strategies Used by Australian Race Walkers.

Introduction: The Tokyo 2021 Olympic Games was anticipated to expose athletes to the most challenging climatic conditions experienced in the history of the modern Olympic Games. This study documents strategies executed by Australian endurance athletes during the team holding camp and Olympic Games experiences, including (1) baseline physiological data, training data, and heat acclimation/acclimatization practices; (2) pre- and in-race cooling and nutritional strategies, and (3) Olympic Games race performance data. Methods: Six athletes (three males, three females; age 24 ± 4 years; VO2max 63.2 ± 8.7 mL⋅kg-1⋅min-1; sum of 7 skinfolds 53.1 ± 23.4 mm) were observed prior to and during the team holding camp held in Cairns, QLD, Australia. Athletes completed 6-7 weeks of intermittent heat acclimation training, utilizing a combination of 2-4 passive and active acclimation sessions per week. Active acclimation was systematically increased via exposure time, exercise intensity, temperature, and humidity. In the team holding camp, athletes undertook a further 23 heat acclimatization training sessions over 18 days in a continuous fashion. Hyperhydration (using sodium and glycerol osmolytes), and internal and external pre-and in-race cooling methods were also utilized. A low energy availability intervention was implemented with two athletes, as a strategy to periodize ideal race body composition. Race performance data and environmental conditions from the 2021 Olympic Games were also documented. Results: The highest values for aerobic capacity were 63.6 mL⋅kg-1⋅min-1 for female race walkers and 73.7 mL⋅kg-1⋅min-1 for males. Training volume for the six athletes was the highest in the second week of the team holding camp, and training intensity was lowest in the first week of the team holding camp. Performance outcomes included 6th place in the women's 20 km event (1:30:39), which was within 2% of her 20 km personal best time, and 8th place in the men's 50 km event (3:52:01), which was a personal best performance time. Conclusion: Periodized training, heat acclimation/acclimatization, cooling and nutritional strategies study may have contributed to the race outcomes in Olympic Games held hot, humid conditions, for the race walkers within this observational study.

Postexercise Hot-Water Immersion Does Not Further Enhance Heat Adaptation or Performance in Endurance Athletes Training in a Hot Environment.

PURPOSE: Hot-water immersion (HWI) after training in temperate conditions has been shown to induce thermophysiological adaptations and improve endurance performance in the heat; however, the potential additive effects of HWI and training in hot outdoor conditions remain unknown. Therefore, this study aimed to determine the effect of repeated postexercise HWI in athletes training in a hot environment. METHODS: A total of 13 (9 female) elite/preelite racewalkers completed a 15-day training program in outdoor heat (mean afternoon high temperature = 34.6°C). Athletes were divided into 2 matched groups that completed either HWI (40°C for 30-40 min) or seated rest in 21°C (CON), following 8 training sessions. Pre-post testing included a 30-minute fixed-intensity walk in heat, laboratory incremental walk to exhaustion, and 10,000-m outdoor time trial. RESULTS: Training frequency and volume were similar between groups (P = .54). Core temperature was significantly higher during immersion in HWI (38.5 [0.3]) than CON (37.8°C [0.2°C]; P < .001). There were no differences between groups in resting or exercise rectal temperature or heart rate, skin temperature, sweat rate, or the speed at lactate threshold 2, maximal O2 uptake, or 10,000-m performance (P > .05). There were significant (P < .05) pre-post differences for both groups in submaximal exercising heart rate (∼11 beats·min-1), sweat rate (0.34-0.55 L·h-1) and thermal comfort (1.2-1.5 arbitrary units), and 10,000-m racewalking performance time (∼3 min). CONCLUSIONS: Both groups demonstrated significant improvement in markers of heat adaptation and performance; however, the addition of HWI did not provide further enhancements. Improvements in adaptation appeared to be maximized by the training program in hot conditions.

Neither Beetroot Juice Supplementation nor Increased Carbohydrate Oxidation Enhance Economy of Prolonged Exercise in Elite Race Walkers.

Given the importance of exercise economy to endurance performance, we implemented two strategies purported to reduce the oxygen cost of exercise within a 4 week training camp in 21 elite male race walkers. Fourteen athletes undertook a crossover investigation with beetroot juice (BRJ) or placebo (PLA) [2 d preload, 2 h pre-exercise + 35 min during exercise] during a 26 km race walking at speeds simulating competitive events. Separately, 19 athletes undertook a parallel group investigation of a multi-pronged strategy (MAX; n = 9) involving chronic (2 w high carbohydrate [CHO] diet + gut training) and acute (CHO loading + 90 g/h CHO during exercise) strategies to promote endogenous and exogenous CHO availability, compared with strategies reflecting lower ranges of current guidelines (CON; n = 10). There were no differences between BRJ and PLA trials for rates of CHO (p = 0.203) or fat (p = 0.818) oxidation or oxygen consumption (p = 0.090). Compared with CON, MAX was associated with higher rates of CHO oxidation during exercise, with increased exogenous CHO use (CON; peak = ~0.45 g/min; MAX: peak = ~1.45 g/min, p < 0.001). High rates of exogenous CHO use were achieved prior to gut training, without further improvement, suggesting that elite athletes already optimise intestinal CHO absorption via habitual practices. No differences in exercise economy were detected despite small differences in substrate use. Future studies should investigate the impact of these strategies on sub-elite athletes' economy as well as the performance effects in elite groups.

Altitude and Heat Training in Preparation for Competitions in the Heat: A Case Study.

PURPOSE: To quantify, for an elite-level racewalker, altitude training, heat acclimation and acclimatization, physiological data, and race performance from January 2007 to August 2008. METHODS: The participant performed 7 blocks of altitude training: 2 "live high:train high" blocks at 1380 m (total = 22 d) and 5 simulated "live high:train low" blocks at 3000 m/600 m (total = 98 d). Prior to the 2007 World Championships and the 2008 Olympic Games, 2 heat-acclimation blocks of ~6 weeks were performed (1 session/week), with ∼2 weeks of heat acclimatization completed immediately prior to each 20-km event. RESULTS: During the observation period, physiological testing included maximal oxygen uptake (VO2max, mL·kg-1·min-1), walking speed (km·h-1) at 4 mmol·L-1 blood lactate concentration [La-], body mass (kg), and hemoglobin mass (g), and 12 × 20-km races and 2 × 50-km races were performed. The highest VO2max was 67.0 mL·kg-1·min-1 (August 2007), which improved 3.1% from the first measurement (64.9 mL·kg-1·min-1, June 2007). The highest percentage change in any physiological variable was 7.1%, for 4 mmol·L-1 [La-] walking speed, improving from 14.1 (June 2007) to 15.1 km·h-1 (August 2007). Personal-best times for 20 km improved from (hh:mm:ss) 1:21:36 to 1:19:41 (2.4%) and from 3:55:08 to 3:39:27 (7.1%) in the 50-km event. The participant won Olympic bronze and silver medals in the 20- and 50-km, respectively. CONCLUSIONS: Elite racewalkers who regularly perform altitude training may benefit from periodized heat acclimation and acclimatization prior to major international competitions in the heat.

Core Temperature Responses to Elite Racewalking Competition.

PURPOSE: The core temperature responses during exercise and effects of different cooling strategies on endurance performance under heat stress have been investigated in recreational athletes. This investigation aimed to determine peak rectal temperatures during elite racewalking competitions and to detail any cooling strategies used. METHODS: Rectal temperature was measured in 14 heat-adapted elite/preelite race walkers (9 females) via a telemetric capsule across 4 outdoor events, including the 2018 Commonwealth Games (race 1: 20 km, 25°C, 74% relative humidity [RH], n = 2) and 3 International Association of Athletics Federations-sanctioned 10-km events (race 2: 19°C, 34% RH, n = 2; race 3: 29°C, 47% RH, n = 14; and race 4: 23°C, 72% RH, n = 11). All athletes completed race 3, and a subsample completed the other events. Their use of cooling strategies and symptoms of heat illness were determined. RESULTS: Peak rectal temperatures >40°C were observed in all events. The highest rectal temperature observed during an event was 41.2°C. These high rectal temperatures were observed without concomitant heat illness, with the exception of cramping in one athlete during race 1. The rectal temperatures tended to reach a steady state in the second half of the 20-km event, but no steady state was observed in the 10-km events. The athletes used cooling strategies in race 1 only, implementing different combinations of cold-water immersion, ice-slurry ingestion, ice-towel application, ice-vest application, and facial water spraying. CONCLUSIONS: Elite/preelite race walkers experience rectal temperatures >40°C during competition despite only moderate-warm conditions, and even when precooling and midcooling strategies are applied.

Training to Compete at Altitude:Natural Altitude or Simulated Live High:Train Low?

PURPOSE: To compare the effects of natural altitude training (NAT) and simulated (SIM) live high:train low altitude training on road-race walking performance (min), as well as treadmill threshold walking speed (km·h-1) at 4 mmol·L-1 and maximal oxygen consumption, at 1380 m. METHODS: Twenty-two elite-level male (n = 15) and female (n = 7) race walkers completed 14 d of NAT at 1380 m (n = 7), SIM live high:train low at 3000:600 m (n = 7), or control conditions (600-m altitude; CON, n = 8). All preintervention and postintervention testing procedures were conducted at 1380 m and consisted of an incremental treadmill test, completed prior to a 5 × 2-km road-race walking performance test. Differences between groups were analyzed via mixed-model analysis of variance and magnitude-based inferences, with a substantial change detected with >75% likelihood of exceeding the smallest worthwhile change. RESULTS: The improvement in total performance time for the 5 × 2-km test in NAT was not substantially different from SIM but was substantially greater (85% likely) than CON. The improvement in percentage decrement in the 5 × 2-km performance test in NAT was greater than in both SIM (93% likely) and CON (93% likely). The increase in maximal oxygen consumption was substantially greater (91% likely) in NAT than in SIM. Improvement in threshold walking speed was substantially greater than CON for both SIM (91% likely) and NAT (90% likely). CONCLUSIONS: Both NAT and SIM may allow athletes to achieve reasonable acclimation prior to competition at low altitude.

An attempt to quantify the placebo effect from a three-week simulated altitude training camp in elite race walkers.

PURPOSE: To quantify physiological and performance effects of hypoxic exposure, a training camp, the placebo effect, and a combination of these factors. METHODS: Elite Australian and International race walkers (n = 17) were recruited, including men and women. Three groups were assigned: 1) Live High:Train Low (LHTL, n = 6) of 14 h/d at 3000 m simulated altitude; 2) Placebo (n = 6) of 14 h/d of normoxic exposure (600 m); and 3) Nocebo (n = 5) living in normoxia. All groups undertook similar training during the intervention. Physiological and performance measures included 10-min maximal treadmill distance, peak oxygen uptake (VO2peak), walking economy, and hemoglobin mass (Hbmass). RESULTS: Blinding failed, so the Placebo group was a second control group aware of the treatment. All three groups improved treadmill performance by approx. 4%. Compared with Placebo, LHTL increased Hbmass by 8.6% (90% CI: 3.5 to 14.0%; P = .01, very likely), VO2peak by 2.7% (-2.2 to 7.9%; P = .34, possibly), but had no additional improvement in treadmill distance (-0.8%, -4.6 to 3.8%; P = .75, unlikely) or economy (-8.2%, -24.1 to 5.7%; P = .31, unlikely). Compared with Nocebo, LHTL increased Hbmass by 5.5% (2.5 to 8.7%; P = .01, very likely), VO2peak by 5.8% (2.3 to 9.4%; P = .02, very likely), but had no additional improvement in treadmill distance (0.3%, -1.9 to 2.5%; P = .75, possibly) and had a decrease in walking economy (-16.5%, -30.5 to 3.9%; P = .04, very likely). CONCLUSION: Overall, 3-wk LHTL simulated altitude training for 14 h/d increased Hbmass and VO2peak, but the improvement in treadmill performance was not greater than the training camp effect.