Heat and altitude may improve your performance
Rugby union, widely known as rugby, has evolved dramatically over the last decades. The advent of professionalisation of rugby following the 1995 South Africa World Cup and, nearly 20 years later, at the 2016 Rio Olympic Games in rugby sevens, financial contracting and sport marketing, and some changes in the rules, all contributed to that. Today, the game is faster and more attractive for fans and players than before.
It has also become increasingly more attractive for female athletes. Globally, more than eight million registered and non-registered players engage in rugby. Two million of them are women. That means every fourth rugby player is female today. In France, 210,000 men and 22,000 women are registered in rugby union. But, notably, 20 men and 23 women are professional players in rugby sevens at the French Rugby Federation (FFR).
These players look for innovative training methods to optimise their performance in preparation for major competitions, such as the Olympic Games. With the rapid development of sport sciences, we are in a position to offer approaches that are backed by our research.
What is environmental stress
Using environmental stress to enhance performance has become a key preoccupation for us as sport scientists. You might know that stress can be both negative and positive. As a training concept, we use mainly altitude and heat exposure. These may be perceived as negative stressors, but can achieve changes in the body that positively affect performance.
Training under hypoxic conditions, meaning with lower oxygen levels in the blood than normal, is not new. It has been used for about 50 years. It boosts athletes’ aerobic capacity via haematological benefits in endurance sports, such as biathlon or cycling. Haematological refers to the blood, where hypoxic training increases the number of red blood cells that carry oxygen. In fact, the 1968 Olympic Games in Mexico represented the starting point of scientific research on hypoxic training.
In team sports such as rugby, we began to use hypoxic stress more recently and for different reasons (such as the development of more hypoxia facilities, new methods, etc. …). Furthermore, training under hot conditions is used to improve heat tolerance when players compete in hot locations around the globe. This includes acclimatization in a natural environment and acclimation in an artificial environment.
Based on the exploration of the current scientific literature and my practical experience over the years, I want to share strategies around environmental stress in this blog. We use these successfully in the FFR to develop the capacity and performance of female rugby sevens players.
Environmental stress component one: hypoxia
We know that additional hypoxia during training, which in itself causes hypoxic stress, results in even higher metabolic stress, especially in our muscles. By adding such stress, we promote desired adaptive responses that lead to improved athletic performance. This goes beyond what we can achieve with training alone and mostly results from aerobic adaptations. Recent data has also shown that repeated-sprint training in hypoxia (RSH) can improve repeated sprint ability in team sports players.
With the French women’s rugby sevens teams, we performed two different training camps to fully exploit the benefits of hypoxia stress. One training camp in Tignes, France, was held before the 2016 Summer Olympic Games in Rio. There, we used hypobaric hypoxia, meaning players inspired air with normal oxygen content but reduced barometric pressure. Barometric pressure is caused by the weight of the air. At the training camp in Doha, Qatar, before the 2017 Dubai Seven’s Tournament, we used normobaric hypoxia. This means players inspired air with decreased oxygen content under normal barometric pressure.
Hypoxia stress during altitude training
The first training camp in Tignes offered what we call natural stress hypoxia. The altitude of the location leads to a decrease in the amount of oxygen in the blood due to a drop in barometric pressure. The concentration of oxygen in the air remains unchanged compared to sea level.
For effective altitude training, we have to carefully manage the hypoxic dose, depending on the duration and the severity of altitude exposure. We need to understand that either too fast or too high, or both, may be detrimental to players’ health. Hence, we monitored different parameters for each player: First, we ensured appropriate fitness levels, no sickness, and good blood results in the three months before the camp. Second, we checked effective hydration and sleep quality during the camp. We consider this crucial to prevent potential health issues for our players during the actual training sessions.
Practically, we performed rugby training sessions at 2100 m of altitude and repeated sprint sessions at 3000 m altitude. After each session, we asked our players how they felt. Their answers showed highly individual reactions. Some players suffered more than others from the stress of altitude. This is why it is so essential to individualize certain sequences to accompany the whole group during the team sessions.
Video 1 (we thank the FFR for this video) illustrates a typical RSH session: Each player performed three sets of 10 x 6-second all-out efforts with 24 seconds of recovery. The aim was to improve repeated sprint ability.
Hypoxia stress during training in an environmental chamber
The second training camp in Doha offered what we call artificial stress hypoxia that is produced by training in an environmental chamber. This stress hypoxia is defined by a decrease in the amount of oxygen in the blood due to a decrease of oxygen in the inspired air.
Similar to what I underlined above for natural altitude conditions, defining the appropriate hypoxic dose is paramount for protecting the health and achieving optimal performance effects in each athlete. During this experiment, players performed repeated sprints on a cycle at 5000 m altitude. Practically, this meant a total of four sets of 5 x 5-second all-out efforts with 25-second recovery intervals. Between the sets, players recovered in normoxia, outside the chamber.
Video 2 (we thank P. Albaladejo for this ) illustrates a typical RSH session. The chamber enabled us to introduce a small, but important difference to natural conditions: While the efforts were performed with maximal intensity under hypoxia, we used three-minute recovery periods between each set under normal oxygen concentrations. This allowed players to preserve their performance (peak power) across sets better, thereby maintaining training quality.
Hypoxia stress may benefit female athletes
What I have learnt from these two rugby training camps is that many female athletes would benefit from training under hypoxia conditions. However, such training needs to supervised by an exercise physiologist or sport scientist to effectively manage the training loads. This will prevent negative impacts resulting from overloading.
Environmental stress component two: heat
Training and competing under heat stress induce thermoregulatory strain on the body. Thermoregulation is a process that allows your body to maintain its core temperature. At the same time, other regulatory systems in the body are also stressed. This stress may occur to a degree where it negatively impacts exercise capacity during endurance events.
We use acclimatization in a natural environment and acclimation in an artificial environment to enable athletes to acclimate to hot conditions and improve their heat tolerance.
In rugby sevens, training or competition often take place in the heat. In fact, the effort can lead to a decrease in endurance capacity, or a high core temperature (called hyperthermia) may compromise players’ fatigue resistance during repeated sprints.
Heat stress during training in an environmental chamber
Recently, the National Rugby Center of the FFR was equipped with an environmental room that allows managing hypoxia, heat, and humidity in an area of 80 m2 (available for rent for a team or individual athlete). We set out to assess the effect of acclimation in the French women sevens’ team before the 2019 Dubai tournament.
During a ten-day period before travelling to Dubai, a group of our players performed five heat training sessions consisting of three sets of 12 x 6-second all-out contact, cycling, and sprinting efforts with a 24-second recovery period. The other group of players did not perform heat training sessions.
Many studies used low-intensity and long-duration training in the heat to improve performance. However, others found that high-intensity intermittent training in the heat, even when of short duration (30–45 min), can achieve similar adaptations. It also increased intermittent running exercise capacity in female athletes. We wanted to more closely replicate the training and game demands of rugby sevens, which predominantly involves accelerations and contact efforts. Therefore, we designed our heat training around repeated high-intensity efforts.
Heat acclimation may benefit female athletes
In Dubai, our players who had performed heat acclimation before the event reported better heat tolerance and more comfort when training in the heat than players who had not been exposed to heat prior to departure. This suggested that our short-term heat acclimation protocol was effective at lowering heat sensitivity. However, it has to be added that the environmental stress was considered as mild at the competition site (26–28 °C, about 50% relative humidity).
At the same time, this reduced heat sensitivity in Dubai was reported despite the heat acclimation group having had trained harder, meaning they had covered more total distance and high-speed distance than the other players. Our study adds to the current knowledge and may be of interest to athletes, coaches, and staff preparing for competitions to be held in hot environments, such as the 2021 Tokyo Olympic Games.
To illustrate that, video 3 (many thanks to the FFR) shows our players performing repeated high intensity exercises: SkiErg, contact (tackle/ruck), cycling, Assault Bike, and sprinting efforts (three sets of 12 x 6-second all-out with a 24-second recovery period).
What do our findings on hypoxia and heat stress mean to you as a female athlete?
One lesson learned is that many female athletes would benefit from training in hypoxic conditions, whether natural or artificial. However, it is critical that the training is supervised by a conditioning specialist to define the most adequate hypoxic dose and maximise an individual’s adaptation responses.
Concerning heat training, we have demonstrated that five sessions of heat training performed in the days before departure to a hot outdoor environment can induce moderate-to-large reductions in heat sensitivity.
In elite sport, the difference can be in the details—a hundredth of a second, a centimetre… Thus, environmental stress as a strategy, if appropriately managed, can allow you or your team to cross a milestone. Or, perhaps, to climb on the podium.