Extended Desaturation Training For Respiratory Limited Athletes
In this article, I'll discuss the use of extended desaturation training to improve respiratory limitations caused by diaphragm muscle fatigue and pulmonary diffusion limitations. If you want to understand how to train a respiratory limited athlete more holistically, you can read my previous article titled, Training The Respiratory Limited Athlete.
An important consideration when training the respiratory limited athlete is that the amount of training volume they accumulate at a high percentage of their peak oxygen consumption (VO2peak) is a primary driver of performance improvements. However, the amount of training that an athlete's muscles, bones, and joints can tolerate in a given week is finite, limiting how much work they can conceivably do at a high percentage of their VO2peak while still performing training in other intensity domains. This is especially true for mixed sport athletes, like Crossfit competitors, who can only dedicate so much time to energy system development given all of the sport-specific training they do year-round. As a result, it's crucial that these athletes find a way to elicit the adaptations associated with training at a high percentage of VO2peak while accumulating as little volume as is necessary to do so.
One of my go-to methods for these athletes is extended desaturation training (EDT). When I prescribe EDT I'll have athletes work at a fast, but not maximal, power output. So, for example, if they are on the rower, echo bike, or Skierg i'll have them work at ~80-85%, 60-65%, and 85-90% of their maximal power output, respectively. It's important that we pick an output that causes the athlete to ramp up their oxygen extraction to a meaningful degree, but not so quickly that they cannot sustain their output for a minimum of 30 seconds. On each work interval, i'll have the athlete hold the aforementioned fixed power output until they outstrip their oxygen supply, which occurs when their muscle oxygen saturation stops decreasing and plateaus at a local minimum. At this point, the rate of change of muscle oxygen saturation (ΔSmO2) will go from a negative value to a number approximating a rate of change of zero percent per second.
The picture above shows a muscle oxygen saturation trend from an athlete performing the same EDT session twice, with three weeks between sessions. By calculating the area over the curve of muscle oxygen saturation (SmO2) during each work bout, we can quantify the total energy turnover for each interval. For example, you can see that from the first to second time the athlete performed this workout, they not only extended the time it took for muscle oxygen saturation to reach a nadir, but they also increased their total energy turnover as well.
Keep in mind, the progression from the first to the second session was not forced. In addition, the interval lengths and total work performed are based on live physiologic data, so the differences in performance represent improvements in the cardiopulmonary system's ability to uptake and transport oxygen, as well as the athlete's ability to breath off excess carbon dioxide. Going forward, we'll have this athlete continue repeating this session until they no longer make quantitative improvements. At that point, we will identify their current energetic limiter and cater training towards improving it. For example, If this athlete still presents with a respiratory limitation we may decide to substitute EDT for hard-start interval training.
Hard-start interval training is in opposition to traditional interval training sessions where athletes complete a series of fixed pace intervals. During hard-start intervals athletes are instructed to start at a very fast pace and descend in speed across the interval. Numerous studies have shown that hard start intervals induce higher mean oxygen consumption levels than traditional interval structures despite similar average speeds, indicating that hard start intervals are a good strategy for interval sessions aiming to accumulate more time at a high percentage of VO2peak with less wear and tear (similar to EDT training). Practically, this could entrail replacing fixed pace 500m rowing intervals where the average pace equals 1:40/500m for a 500m rowing interval where an athlete perform the first 125m at 1:34/500m, the next 125m segment at 1:38/500m, and the next two 125m segments at 1:42/500m and 1:46/500m respectively.
In the image below you’ll find examples of NIRS guided and auto regulated EDT sessions (left-most cell), an example hard-start interval session (middle cell), and a sample cardiac-respiratory coordination session (right-most cell).
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