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Sleep and the Lactate Threshold

If your workouts involve moderate intensity for prolonged periods, sleep deprivation can cause you to reach your lactate threshold more quickly. This can result in a drop in performance sooner than expected, making it difficult to maintain your pace in the final moments of the session.

Cardiovascular and Respiratory Impacts

Sleep deprivation affects not only energy metabolism but also the heart and lungs' ability to sustain prolonged exertion. A Brazilian study analyzed the relationship between sleep quality and cardiorespiratory parameters in athletes and reached the following conclusions:

• Individuals with good sleep quality had higher VO2max and lower maximum heart rate compared to those with poor sleep quality.

• Sleep duration had a direct impact on the athletes' maximum power output.

Another study found that lack of sleep affects cardiovascular performance more significantly in men than in women, possibly due to hormonal and metabolic differences.

Furthermore, the relationship between power and heart rate also changes with sleep deprivation. Australian researchers analyzed how different sleep patterns influence performance over four days of endurance training. They found that athletes with limited sleep had a greater ratio of external load to internal load, similar to what happens during extreme stress in competitions like the Tour de France.

What does this mean in practice?

If you sleep poorly before an intense session, your heart may need to work harder to produce the same effort. This can lead to premature fatigue and slower recovery in the following days.

Lower Resistance and Greater Perceived Effort

In addition to physiological changes, sleep deprivation also affects mental endurance. Studies evaluating time to exhaustion under different sleep conditions have shown that:

• After a single night of only 4 hours of sleep, athletes covered shorter distances, recorded slower average speeds, and reported greater physical discomfort.

• In exhaustion tests on a treadmill at 80% VO2max, sleep-deprived participants reduced their time to failure by about 11%.

• Perceived exertion (RPE) increased significantly after a night of poor sleep, indicating that, even if the body can still maintain good performance, mental fatigue can cause athletes to reduce intensity or end the session early.

What does this mean in practice?

If you wake up feeling like you didn't sleep well, it can affect not only your performance, but also your motivation and ability to tolerate the discomfort of training.

How to Monitor the Impact of Sleep on Workouts?

If you're an athlete or coach, you can monitor the impact of sleep quality on performance in a number of ways:

1. RPE (Rating of Perceived Exertion) Assessment

- If you notice a progressive increase in perceived exertion without a corresponding increase in training load, it may be a sign of inadequate sleep.

2. Heart Rate Variability (HRV) Measurement

- A consistently reduced HRV may indicate that the autonomic nervous system is under chronic stress, possibly due to sleep deprivation.

3. Pace and Intensity Monitoring

- If your times or power output start to drop for no apparent reason, it may be worth analyzing your sleep patterns.

4. Using Apps and Wearables

- Devices like Garmin, WHOOP, or Oura Ring can provide insights into your sleep quality and how it affects recovery and performance.

Conclusion

Sleep isn't just a factor in recovery; it's an essential component of performance. When athletes sleep poorly, fatigue sets in sooner, cardiorespiratory fitness is reduced, and perceived exertion increases. To maximize performance and longevity in endurance sports, it's crucial to include sleep as a fundamental part of your training and recovery strategy.

If you want to optimize your performance, make sure you get enough sleep and maintain a consistent sleep routine. Small adjustments to your rest can be as impactful as a well-structured training session!