When exercising at altitude, it can be **difficult to match the intensity carried out at sea level**. This is mainly due to the change in environment, i.e., reduced oxygen, **restricting the full capability of performance in a demanding environment that is typically carried out in a ‘normal’ environment**. If this is the case, should the relative exercise intensity be reduced at altitude? And if so, by how much?

Researchers in Qatar have recently published some work that informs the **effects of altitude on cycling performance**. 9 well-trained cyclists completed time trials at varying levels of simulated altitude (250, 1250, 2250, 3250 and 4250 m) on separate occasions. **Critical power** (sustained power for a specified period of time) was then determined from each time trial.

The results showed that, as expected, critical power across all time trials reduced as elevation above altitude increased. Critical power was ~275 W at 250 m, whereas, this reduced to ~200 W at 4250 m. At 2250 m (almost equivalent to the hypoxic chamber), critical power was ~240 W. However, it can be considered inaccurate to reduce critical power by ~35 W when exercising in the chamber. After a great deal of statistical modelling, the authors produced an equation (see below) to calculate the percentage reduction in critical power for a given level of altitude.

**y = 0.0016×3 – 0.0157×2 – 0.027x +1.0025**

N.B. y is the percentage reduction in critical power; x is the level of altitude in kilometres (2.7 in the chamber).

So, if you are statistically fluent, have a scientific calculator to hand and want to increase the precision of your training **this will be worth calculating**! Alternatively, we can calculate this for you.

In summary, **exercising at altitude is demanding** and may lead to negative implications, such as overtraining, if the correct procedures for maintaining effort and managing the intensity are unknown or wrongly estimated. It is now possible to accurately calculate the reduction in critical power for a given altitude, which will **reduce the potential of over-training, under-training and managing fatigue**.

**Study details**

Townsend et al. (2017). Prediction of critical power and ‘W’ in hypoxia: Application to work-balance modelling. Frontiers in Physiology.