IHT vs. RSH: Which Altitude Training Actually Works for You?

Altitude training sounds cool… but the traditional version comes with a big catch: most people don’t have the time, budget, or flexibility to disappear to the mountains for several weeks.

That’s exactly why Live Low Train High (LLTH) has become such a practical alternative. Instead of relocating or sleeping in an altitude tent every night, you keep your normal life - sleeping, working, recovering at sea level - and simply add specific training sessions in a hypoxic environment.

Simple. Efficient. Actually doable.

In other words, you get the stimulus of altitude without turning your entire routine upside down.

Within this approach, two methods stand out: Intermittent Hypoxic Training (IHT) and Repeated Sprint Training in Hypoxia (RSH) or Repeated Suffering in Hypoxia, as we like to call it. They’re often mentioned together, but they target very different adaptations, and understanding that difference is key if you want to use altitude training effectively.

What LLTH actually changes in your body

Before comparing the two, it’s important to understand what LLTH is really doing.

Unlike traditional altitude strategies like Live High Train Low (LHTL), which aim to increase red blood cell mass, LLTH mostly drives what are called non-haematological adaptations. That means the improvements come from how your muscles use oxygen, manage energy, and tolerate fatigue, rather than from simply carrying more oxygen in your blood.

You’re not just adding capacity, you’re making the system more efficient.

IHT: building your aerobic engine

Intermittent Hypoxic Training is essentially interval training performed in a low-oxygen environment. The intensity is typically controlled but still demanding, usually above 70% of your maximum heart rate. You’re working hard, but you’re not sprinting all-out.

Because of that, IHT primarily targets the aerobic system. Over time, it improves mitochondrial efficiency, enhances aerobic energy production, and can lead to measurable increases in VO₂ max - even without changes in red blood cell count.

This is one of the most interesting aspects of IHT. The body becomes better at using the oxygen it already has, which translates into improved endurance performance. For athletes who rely on sustained efforts - cyclists, runners, triathletes - this is exactly what matters most.

For IHT, the goal is to stress the aerobic system without completely overwhelming it. Because of that, simulated altitudes are typically in a moderate range, usually around 2000 to 3000 meters (sometimes slightly higher depending on the athlete and protocol).

At this level, oxygen availability is reduced enough to challenge your cardiorespiratory system and improve efficiency, but still allows you to maintain quality during intervals. If the altitude is too high, intensity drops, and you lose the aerobic stimulus you’re actually aiming for.

While there can be some crossover benefits into anaerobic performance, the main goal of IHT remains clear: improving your ability to go longer and maintain power over time.

RSH: training your ability to suffer repeatedly

Repeated Sprint Training in Hypoxia takes a very different approach. Instead of controlled intervals, it revolves around short, maximal efforts - typically under 30 seconds - combined with deliberately short recovery periods.

This detail is crucial. The recovery is intentionally incomplete, meaning you start each new sprint while still fatigued. As the session progresses, performance naturally drops, and that’s not a failure of the session - it’s the point.

The goal of RSH is to stress the body’s ability to repeatedly produce high power under fatigue. This leads to strong recruitment of fast-twitch muscle fibres, which are responsible for explosive efforts, and forces adaptations that improve fatigue resistance and buffering capacity. RSH has been shown to significantly delay the onset of muscle fatigue, allowing athletes to complete a higher number of sprints before reaching exhaustion.

Since the goal is to maximise metabolic stress and fast-twitch fibre recruitment, protocols are often performed at higher simulated altitudes, typically around 3000 to 4500 meters.

Here, the reduced oxygen accelerates fatigue between sprints, making it much harder to maintain power output across repetitions. That’s exactly what drives the adaptation - your body is forced to cope with repeated high-intensity efforts under stress. As always, more is not better. The right altitude is the one that allows you to hit the intended training intensity, not just the lowest oxygen possible!

Unlike IHT, RSH does not significantly improve VO₂max. The aerobic system is still involved, but it’s not the primary target. Instead, RSH is about maintaining performance when intensity is high and recovery is limited.

This makes it particularly relevant for athletes in intermittent sports like football, where performance depends on the ability to sprint, recover quickly, and sprint again - often under pressure and fatigue. In professional rugby players and football teams, RSH produces faster mean sprint times and smaller speed decrements compared to identical training performed in normal oxygen conditions (normoxia). This attribute is vital for maintaining physical involvement during the final stages of a match.

The real difference

At a glance, both IHT and RSH involve training in hypoxia, but the similarity mostly ends there.

IHT is about controlled intensity and aerobic development. It helps you sustain effort, improve efficiency, and build a stronger endurance base.

RSH, on the other hand, is built around maximal effort and incomplete recovery. It challenges your ability to produce and repeat high-intensity efforts, even when your body would prefer to slow down.

If you simplify it, IHT helps you go longer, while RSH helps you go hard again and again.

Why intensity changes everything

The defining difference between the two methods comes down to intensity.

IHT stays in a demanding but sustainable zone, where the aerobic system is doing most of the work. RSH pushes you into maximal efforts, which are necessary to fully recruit fast-twitch muscle fibres. These fibres only become heavily involved when intensity is very high, and they are central to the adaptations RSH is trying to achieve.

Without that level of effort, RSH simply doesn’t work as intended. It’s not just about training in hypoxia - it’s about combining hypoxia with maximal intensity and limited recovery.

Choosing the right approach

Which method is “better” depends entirely on what you need.

If your goal is to improve endurance, increase VO₂ max, and become more efficient over longer efforts, IHT is the more relevant tool. It fits naturally into the training of endurance athletes and supports steady performance improvements over time.

If your sport demands repeated high-intensity efforts with limited recovery, RSH becomes far more specific. It prepares you for exactly the kind of fatigue and intensity you experience in competition.

In practice, most athletes can benefit from both. IHT can be used to build a strong aerobic foundation, while RSH can be introduced closer to competition to sharpen high-intensity performance.

Final thought

Altitude training doesn’t have to mean committing to weeks of disrupted sleep and a completely different lifestyle.

With LLTH, you can stay in your normal environment and apply altitude stimulus in a targeted, time-efficient way. Whether you choose IHT, RSH, or a combination of both, the real advantage is flexibility - you can train for exactly the demands of your sport without overcomplicating your life.