Optimized Training Stress (OTS)

We are introducing a new and improved power-based metric to measure an athlete’s training stress: Optimized Training Stress (OTS).

The development of OTS includes three improvements to existing training stress metrics:

#1 OTS accounts for the fatigue that accumulates within an exercise session. Your long ride feels harder during the 4th hour than it did during the first hour because your physiology changed during the ride.

#2 OTS accounts for the increase in fatigue and stress that results from not eating enough carbohydrates during the ride.

#3 OTS accounts for periods of coasting and does not provide training “credit” for that time.

Listen to Dr. Phil Skiba and Frank Overton's podcast about OTS 👇

These improvements result in a way of accounting for training stress that is more reflective of the actual work and time the athlete puts in.

OTS will help athletes, coaches and sports scientists better quantify training load to help them fine tune the appropriate balance between training and recovery.

How does OTS work?

It is likely that an athlete’s “threshold power” (scientifically known as the Critical Power (CP) and often estimated by FTP) decreases with time. For example, a recent study by Clark et al. demonstrated that the CP may drop considerably over the course over even a two-hour ride. This drop is in part related to carbohydrate consumption while on the bike. For example, an athlete with a threshold power / CP of 250 watts at the beginning of a ride may be unable to produce even 200 watts after 3, or 4 or 5 hours of riding if they do not eat enough. Athletes are able to mitigate fatigue and decreases in power output with carbohydrate consumption. OTS automatically accounts for this by varying the stress recorded based on carbohydrate intake.

Figure 1: Relationship between the drop in CP/"Threshold" power as a result of different levels of carbohydrate intake. Note that the drop is both steeper and deeper with decreasing carbohydrate intake. 

Duration (hours)

Carbohydrate Consumption (grams)



60 - 120 



20 - 60



No carbohydrate


Table 1: An athlete with a CP/"threshold" power of 300W does a 3 hour ride a t steady manageable pace. How difficult this ride feels is directly related to how much carbohydrate they eat. The OTS reflects this difference in training stress.

Embracing the future!

OTS is being continually refined to account for physiological changes that determine the impact of training on the human body. Watch this space as we continue to innovate! Our goal with OTS is to help athletes, coaches and sports scientists better quantify training load and help them determine with a higher degree of confidence the appropriate balance between training and recovery. 


Clark et al. Dynamics of the power-duration relationship during prolonged endurance exercise and influence of carbohydrate ingestion. J Appl Physiol. 127: 726–736, 2019.

Puchowicz et al. Development and field validation of an omni-domain power-duration model. J Sports Sci. 38(7):801-813, 2020. 

Marquet et al. Enhanced endurance performance by periodization of carbohydrate intake: “sleep low” strategy. Med Sci Sports Exerc. 48(4): 663-672, 2016. 


Dr. Phil Skiba is an algorithmic performance engineer, elite endurance coach and Sports Medicine doctor.  Phil recently worked on Nike’s Breaking 2 project to help Eliud Kipchoge run a sub-2 hour marathon.

Frank Overton is the founder and CEO of FasCat Coaching with 20 years experience coaching and analyzing data from pro’s to enthusiasts of all abilities all over the world. 

OTS is in development and the technology will be available in our app for a monthly subscription this Summer.  Subscribe to our email newsletter 👇 to be notified of its release! Please read how we are combining OTS with your wearable data to Optimize your training which will also be a part of our new app.

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To talk with a FasCat Coach about your Optimized Training Stress, please fill out a New Athlete Questionnaire to set up a FREE Coaching Consultation.