Utilizing Training Stress Score (TSS)
The Training Stress Score (TSS) is an important metric developed in order to measure the load of a quasi-proportionate dose in relation to the individual’s current level of fitness. It combines both the exercise duration and heart rate, giving you a holistic understanding of the effort made.
Calculating TSS
TSS defines an intensity factor (IF), which is calculated by comparing the normalized power of a workout to the functional threshold power (FTP) of an athlete. The formula is:
TSS = (Time in seconds x (Normalized Power) x (IF)) / (FTP x 3600) x 100
For example, if an athlete has a Functional Threshold Power (FTP) of 250 watts and performs a one-hour workout at 230 watts of normalized power and with an Intensity Factor (IF) of 0.92, the TSS score would be: 100 TSS.
TSS = (3600 x 230 x 0.92) / (250 x 3600) x 100TSS = 85
A score over the 50 mark means that an athlete has experienced a significant workout compared with where they are currently.
Application in Training Plans
TSS is used by coaches and individual athletes to structure effective training plans. By programming to certain TSS values within workouts they are making sure the athlete is not undertraining or overreaching (decreased performance), which is creating potential for optimal performance gains. There will be specific times when the athlete tapers and the TSS reduces significantly to allow for recovery and adaptation, leading up to a major race where the TSS creeps up from week to week, peaking the athlete and allowing for maximal fitness at that race.
Preparing for a Marathon
Take a marathon runner who wants to run her fastest time on race day. For a 16-week preparation, their coach schedules a weekly TSS may rise from 200 to 500 over the course of preparation. One week might include a combination of high-intensity interval training (HIIT) sessions, long slow distance (LSD) runs, and recovery workouts, each providing their own contribution to the weekly TSS sum. The tweaking of TSS precisely assures that the athlete peaks at just the right time without overtraining.
Monitoring and Adjusting from TSS
Elite athletes and coaches closely track TSS, tweaking training loads depending on performance metrics and their subjective feelings of fatigue. If a more experienced athlete shows either an inability to recover from higher volume weeks (TSS >400 per week leads to consistent signs of fatigue) or responds best when moderate volume weeks still peak at a TSS lower than last time, the coach will adapt their plan so they continue to move forward toward their performance goal wisely, safely and without over-reaching.
Applying Normalized Power (NP) Calculations
Normalized Power (NP) is a measure of the true physiological cost of a cycling workout, especially one with variable power a race or a series of hard, short intervals. Whereas normalised power takes account of those peaks, so would be far more representative of the load as they are still working at full outrength, just at a lower volume.
Understanding NP Calculations
NP is computed as the 4th root of the average of the 30-second-smoothed 4th powers. Then the average of those values is then taken and the fourth root is extracted to give this one single power number. This method of calculation during higher outputs places a much greater physiological demand.
Trigger warning: a cyclist will alternate intervals, perhaps, of 300 watts for 1 minute to 150 watts for a few moments. If they do intense intervals during a generally moderate effort ride, the average power might be deceiving, but the NP won’t be.
Integrating NP into Training
The NP is used by coaches to design workouts to increase the amount of time an athlete can sustain and recover from power. By looking at the NP from previous sessions, a coach can prescribe interval workouts with specific targets to incrementally increase the athlete’s resistance to higher power outputs over longer intervals.
Adding NP in a Training Cycle
Take a triathlete preparing to race an Ironman and using NP. The coached looks back at months of training data to determine what the athlete can hold for a 4-hour ride at 1.0 IF. A gradual progression in target NP of key workouts is effective in improving the endurance and power-handling ability of the athlete. This gradual increase could look like intervals that increase NP 10-15 watts above baseline every few weeks, interspersed with longer endurance rides at a lower, more sustainable NP.
Monitoring Progress and Revisions
Setting regular NP markers means athletes and coaches can see improvements in power management and endurance over time. If an athlete is appearing to be over-reaching to reach higher NP targets, the coach may make the plan more about building foundational endurance or make time for additional recovery. This flexible approach works really well, by making sure added load is more easily handled, utilised and therefore contributes to improved performance.
Monitoring Chronic Training Load (CTL)
Chronic Training Load (CTL): Approximate average daily training load, standardized over a fairly extended period (perhaps 42 days). It is super important for showing how an athletes overall fitness trends/regresses over the longer term (referred to as ‘fitness’ in Mumziel’s language).
Calculating CTL
CTL = The average of the exponentially weighted moving averages of daily Training Stress Scores (TSS) in a given time range. The weight of each day’s TSS decreases with increasing time from that day so that doing higher intensity work outs today is more important then higher intensity work outs in the next period. This formula takes the decay and response factors for each of the variables and smoothens the data to approximate them as real physiological changes.
Take an athlete that averages 100 TSS a day over 42 days; their CTL would be close to 100, suggesting they are on a very high training load day-to-day. More or higher intensity work will increase CTL,thus making it a useful qualitative proxy of TP.
CTL as a Tool for Planning Your Training Phases
CTL is what coaches actually use to plot out the macrocycles of an athlete’s training schedule (i.e. a build, peak, taper). This method guarantees an incremental increase in CTL during the build phase, allowing the athlete to gradually increase their endurance and fatigue resistance. The peak phase is when the athlete must peak and by maintaining a high CTL, the athlete is ready, but the taper phase is when CTL comes down a bit to allow some recovery while still allowing for good performance on race day.
Marathon Runner Training
Take a marathon runner beginning a cycle with a baseline CTL of 50, and a target peak of 120 for the peak of the season. Some training plan should allow for an increase towards 5-10 units a week in CTL through a mix of long days, high intensity days and around day, providing a balanced build in both volume and quality.
Getting CT Level right for peak performance
Keeping an eye on your CTL not only aids you in mapping-out your future training sessions, but it will also enable you to make decisions in real-time. When an athlete experiences a plateau or decrease in performance, it may be causative of CTL buildup too rapidly and a decrease in training load would be needed or an supported recovery focus.
Analyzing Acute Training Load (ATL)
ATL or Fatigue: This feature typically measures the training load of an athlete over a short period (e.g. 7 days) This metric is used to measure how hard an athlete is working out, and the amount of fatigue that will immediately be sent to their body, which indicates how tired they are.
Calculating ATL
ATL uses the same method as CTL but for a much shorter period. It calculates a daily Training Stress Score (TSS) exponential moving average that has a stronger emphasis on recent sessions. This method would provide a real-time insight into current fitness and fatigue levels which would include the effect of recent workouts.
An athlete may come out of an extremely hard training session with a TSS of 150 and their ATL would increase substantially reflecting that they are much more fatigued and they might need to take it easy and recover that day.
Practical Application of ATL
In terms of practice it is NOT an ideal tool for a coach trying to keep the athletes from being over trained in the short term (ATL). By monitoring ATL, coaches can implement rest or lighter training days when needed, all while ensuring the training load is optimized to avoid burnout and maximize physiological responses to training.
Pre-Race Cyclist
This could be a cyclist increasing their training in preparation for a race by working hard on back-to-back days. Monitoring these ATLs allows a coach to gauge when this accumulated fatigue might be getting too high and risking overtraining or injury. If, on the other hand, the cyclist’s ATL jumps up to 130 from a base of 70 in a week, the coach may choose to add more recovery before progressing to high-intensity efforts.
Changes In Strategy Based On ATL Data
This analysis of ATL grant unique possibilities to cultivate your decision making, in terms of the optimal equilibration between training and recovery. It is very important for competition preparedness, to have athletes fit enough to not be undertrained, that means to be ready for a competition and not too fatigued from overtraining. Workouts or activities that coaches may include in the training plan include passive and active recovery days in order to facilitate recovery these may involve stretching, massage or light cross training that the coach deems appropriate based upon the readings of ATL.
Using Performance Management Chart (PMC)
Visual representation of an athlete’s training load, CTL, ATL, and the balance between these two, TSB, in the Performance Management Chart (PMC). This graph is an invaluable tool for both athletes and coaches to visibly see training progression, fatigue and form throughout the season.
Components of the PMC combines three important factors:
CTL (Fitness) : Athlete fitness over a longer period of time.
ATL (Fitness) = short term training load and fatigue that results from it.
TSB (Form): an indication of how ready the athlete is to perform calculated as CTL minus ATL
If an athletes CTL is 150 and ATL 120, his TSB will equal 30, meaning hes well rested and therefore ready to perform but not overly tired.
Application in Training
It helps you plan your training and racing thanks to the PMC. By staying on top of current trends and modifications with respect to CTL, ATL, and TSB, coaches can better plan intensification blocks, taper periods, and recovery days. It is designed to peak the athlete at the right time for major competitions.
Preview Your PMC for an Upcoming Marathon
The runs right before sending a marathon (prior to the peak event of the PMC), a runner’s CTL will progressively increase going into the peak race, whereas the ATL will collect as spikes (sharp increases) over time (immediate or 7 day periods) as specific higher intensity workouts or long runs. At best, their TSB should be trending toward a positive number in the days leading up to the race (i.e. well rested and relatively well adapted).
Strategic Use of PMC Data
What it comes down to is the fact that you must adjust based on realtime PMC data. A high ATL in the PMC relative to CTL will alert the coach to an unexpected increase in fatigue and give them the opportunity to adjust training intensity or prescribe more rest. Taking this initiative can go a long way in keeping the body in check and helps prevent sustained injury and especially overtraining.
