Apnea: una alternativa a la hipoxia para mejorar el rendimiento en el ciclismo

Abstract

Introduction Cycling encompasses various disciplines, with races ranging from a few seconds to several hours. There is a wide range of sprint or short-duration races, as well as longer endurance races that require a strong start to achieve a good result. In these events, the performance differences among professional cyclists are minimal, so even a small improvement can lead to a significant change in the final result. In the attempt to achieve these gains, it has been common to employ techniques related to manipulating oxygen delivery, such as hypoxia. Recently, it has been proposed that apnoea may be an alternative method to hypoxia. Holding one’s breath triggers hypoxemia and hypercapnia in the body, eliciting not only long-term adaptations but also a series of rapid physiological responses that could potentially enhance performance in the following minutes Aims There are two main objectives: (i) to assess the acute impact of repeated dry dynamic apnoeas during warm-up on a repeated sprint ability (RSA) test and (ii) in a time-toexhaustion test at maximal aerobic power intensity. Additionally, (iii) to validate a near-infrared spectroscopy (NIRS) device to measure haemoglobin concentration and monitor changes in its magnitude during exercise. Methods Four studies were conducted involving a total of 132 cyclists from the Spanish national cycling team. First, the use of two NIRS devices to measure resting haemoglobin was investigated by comparison of the data provided with the real blood value. Subsequently, to assess the possibilities of monitoring changes in haemoglobin concentration during exercise, one of them was validated as an instrument to determine the intensity of the second lactate threshold. Finally, two studies were conducted to examine the impact of performing five maximal dry dynamic apnoeas while cycling during warm-up on subsequent performance. One study involved 23 cyclists who competed in sprint events performing an RSA test –five six-second sprints, with a one-minute recovery between efforts– and a Wingate test. One study involved 23 cyclists who competed in sprint events performing an RSA test - five six-second sprints, with a one-minute recovery between efforts - and a Wingate test. In the other study, 90 endurance cyclists performed a graded exercise test to identify their maximal aerobic power and then a time-toexhaustion test at that intensity. Results Regarding objectives (i) and (ii), when performing apnoeas, the average power in all sprints of the RSA test improved by a mean of 33.7 W –0.45 W/kg–, with no significant differences in peak power. There were also no differences in the Wingate test or the time-to-exhaustion test. Breath-holding reduced the heart rate, which resulted in a decrease in cardiac rhythm at the end of the warm-up. In addition, apnoea also resulted in a 1 mmol/L decrease in lactate concentration –only significant for endurance cyclists– after the time-to-exhaustion test or the Wingate test. In several cases, the duration of apnoeas was shorter than necessary to elicit substantial changes in the physiological response, which is probably why performance did not improve as expected. For objective (iii), both NIRS devices yielded lower values of haemoglobin concentration than the true level in blood at rest, showing poor reproducibility. Moreover, their measurements were particularly affected by adipose tissue thickness. However, during exercise, the NIRS device tested was able to identify changes in muscle oxygenation during a graded exercise test, reporting a high correlation and an acceptable level of agreement in the determination of the second lactate threshold intensity. Conclusions Results of this thesis suggest that, in professional cyclists, it could be interesting to implement the use of apnoeas during the warm-up prior to races in which short all-out repeated efforts are performed. However, they have not produced the expected results in longer efforts, as they have not improved performance. This could be due to the short duration of the apnoeas, so it would be interesting to check what happens after prior familiarisation with the sensations of holding one's breath. As for NIRS devices, although they are not recommended as a valid instrument for measuring resting haemoglobin concentration in blood, they are able to identify changes in oxygenation during exercise.