Fatigue Management for Optimal Performance

COROS GPS Watch Fatigue - EvoLab

At the elite level of human performance metrics, training load and fatigue management become the difference between winning and a dreaded second place. Keeping track of all this information can be tough. Your COROS device will help keep you on track and ready for your next PR! 


Fatigue, on the physiological level, is the inability to maintain or repeat a given level of muscle force production. This results in an acute impairment of performance. It happens to everyone, even the best of the best. Monitoring your training and race day fatigue factors can help slingshot your performance to the next level. Fatigue management includes a variety of factors. Each factor carrying a different amount of weight based on where you are in your training phases and the performance goal.


After long training runs, refueling and getting ready to race, your job is not done. You still need to be mindful of fatigue factors during long events, have a plan to minimize their effect and be prepared. This means fueling during events. Muscles prefer carbohydrates as a fuel source. Research on supplementation with carbohydrates during exercise shows that fatigue can be delayed. Avoid hitting the wall by ingesting glucose about 30 minutes before you usually see a decline in performance. This allows glucose to be absorbed and maximized for continued muscle force production.

Repeatedly running for long periods of time—longer than two hours—helps you combat the psychological and neural causes of fatigue. Our bodies are good at recognizing threats and working to survive by tapping into fuel reserves. Getting in enough carbohydrates following a long run encourages skeletal muscles to respond well to the “empty tank.” This allows the body to be more prepared to fight through that fatigue during future long runs at a high pace. 


Hydrating is part of fueling and is just as important for fighting fatigue during events! Since your sweat rate exceeds your ability to ingest fluids while running, dehydration is difficult to prevent. Research shows that endurance performance declines with a two-to-three percent loss of body weight. It’s critical to minimize this effect in order to fight off performance loss. During marathons, drink fluids with sodium. Why sodium? Water goes wherever sodium goes. This means the kidneys conserves more water when you ingest sodium with the water and builds a ‘reserve’.

Environmental factors also play a large role in sweat rate, dehydration and fatigue management. Acclimate to the environment that you will be competing in. Train for heat, humidity and altitude. 

COROS Metrics

Ok so this is a lot and there is more to come. Your COROS device and Training Hub are designed to make it easier for you to perform at your best! COROS metrics and what they mean for fatigue management are below:

Marathon Level
Marathon Level in Training Hub

Marathon Level measures how you perform on a flat road over the marathon distance. This metric considers your recent running performance and vital fitness data. A higher score means you will complete a full marathon faster than when you have a lower score. Marathon level is a reflection of high quality training and consistency.

  • Beginner (0-40): Completes a full marathon for over 5 hours.
  • Recreational (41-60): Completes a full marathon between 4 to 5 hours.
  • Intermediate (61-70): Completes a full marathon between 3.5 to 4 hours.
  • Advanced (71-80): Completes a full marathon between 3 to 3.5 hours.
  • Elite (81-100): Completes a full marathon between 2 to 3 hours.

COROS ranks your Marathon Level compared to other users in the same age group and sex. This way you can go into your next competition with an idea of where you stand and an even better idea of how to maximize results. Poor fatigue management will show up here by lowering your score overtime. If you see this happening, its time to make some changes!

Running Performance
This runner PR’d Sunday’s race.

Marathon level doesn’t change daily, but a variety of factors including sleep, recovery, previous training, and even mental stress, influence your daily performance.

Running Performance provides feedback on how well your last run was in comparison to your overall running fitness. This is your immediate outcome metric. Running Performance ranges from 80% to 120% with five distinct levels. Over 105% means you are outperforming yourself and likely to peak in races. Lower than 95% indicates that you may need more rest to bounce back. If you are seeing consistently low running performance, it might be time to look at other metrics. Decide if you need to rest and allow recovery to reach optimal performance.

Fatigue found in “Training Load Management” within Training Hub

Fatigue in your COROS Training Hub is the difference between Base Fitness (long term fitness) and Load Impact (stress from recent training) in a carefully designed 0 – 100 scale system. It reflects the amount of fatigue your body is carrying daily from recent training while considering your ability to sustain training load impact. A low value means your body is ready to take on more intensity while a high value indicates you need to rest.

Fatigue 7-day trend displays your daily fatigue over the past 7 days. It is a powerful and objective tool to help provide accurate feedback to avoid injuries and overtraining. When looking at your fatigue trend it can be a great reminder that sometimes fatigue is psychological while other times its physical. Knowing the difference – when to push and when to rest – is critical to maintaining elite performance over months, years and an entire career.

  • Minimal (0-19): Your current training load is light and may reduce your fitness in the long term.
  • Performance (20-39): Your current training load is reduced to allow for optimal performance in races.
  • Optimized (40-59): Your current training load is ideal for maintaining or improving your fitness.
  • High (60-79): Your current training may be unproductive due to the high recent load.
  • Excessive (80-100): Your current training load is excessive and increases the risk of injury.

Like every other factor in elite sport performance – cadence is incredibly specific to an individual. What works for some might not work for others. Cadence means more if you have an idea of where you are consistently. Then you can go into events knowing what it feels like when you are off your goal cadence. Deviating from cadence goals can be a sign of fatigue and an indicator of poor overall performance if you can not recover. Training for this and appropriate fatigue management overtime will help push to the finish line.

Resting Heart Rate
Resting Heart Rate found in “EvoLab Metrics” in Training Hub

In general, the more fit you are, the lower your resting heart rate (RHR) will be. Athletes can have a resting heart rate lower than 40 bpm. If Resting Heart Rate is increasing over time and your training has not changed, it is likely a sign of illness or fatigue. This should serve as a red flag. Poor fatigue management will undoubtedly show up in RHR day-to-day. Make small adjustments daily, then look for improvements. If there is not improvement, more drastic steps might be necessary to ensure you are able to perform come race day.

Training Heart Rate & Zones

Training various HR zones helps to prepare the body for the onset of fatigue and aid in fatigue management. As you are peaking and focusing more specifically on heart rate, athletes and coaches can manually adjust these targets.

  • Heart Rate Zone 1 & Pace Zone 1 (Aerobic Endurance Zone)
  • Heart Rate Zone 2 & Pace Zone 2 (Aerobic Power Zone)
  • Heart Rate Zone 3 & Pace Zone 3 (Threshold Zone)
  • Pace Zone 4 (Above Threshold Zone)
  • Heart Rate Zone 4 & Pace Zone 5 (Anaerobic Endurance Zone)
  • Heart Rate Zone 5 & Pace Zone 6 (Anaerobic Power Zone)

Everyone has a bad day, but fatigue management for performance is looking at how to course correct over time.

As you are cycling through planned training programs, these fatigue factors can help you establish the benefits of the training program day-to-day. This helps coaches and athletes make micro adjustments to daily habits, recovery, and training to elicit elite performance on race day.  

These factors are of high importance for elite performers. These metrics can mean qualifying, setting a record, winning or potentially showing up to a race with too much fatigue.

Taylor Heppner
Taylor Heppner

Taylor Heppner is the Director of Total Performance at Elite Speed Sport Performance. She is a PhD Candidate at Rocky Mountain University in Health Science, Human & Sport Performance. While Taylor has several other industry certifications and educational background she truly just has a passion for helping people reaching the maximal potential through human performance. Her goal is always reducing the risk of injuries and protecting future movement while maximizing performance outcomes now. Taylor grew up as a multisport athletes competing in alpine ski racing, softball and rowing through high school and early college years before diving into coaching full-time. She gets her fix mostly from skiing and hiking in mountains.

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