Hi Ted,
Big topic but here's some answers.
TSS, IF, FTP and a host of other metrics are objective measures for planning workouts in a structured fashion. They allow us to scale workouts based on the fitness of a rider as measured by a power meter. These are all published measures from TrainingPeaks and developed by Hunter Allen, Andrew Coggan and Joe Friel. They were the gold standard for training with power and pretty much everyone licensed them (Garmin for example), or reverse engineered (Strava for example) for use in their training products.. There are some new proprietary measures from Training peaks that are better, but that's the land of coaches right now and they will take time for athletes to learn.
http://help.trainingpeaks.com/hc/en-us/articles/204071944-Training-Stress-Scores-Explained
So an Athlete's FTP is measured by a 8 minute test, 20 minute test, or a 1 hour "Race" data file. The resulting FTP value is a relative measure of how hard you can sustain work before you blow up. It's often mistakenly thought of as your 1 hour sustainable power but it's really a range of about 35minutes - 70 minutes. The creators state this and everyone ignores it and over simplifies it to "1 hour power" (humans be lazy).
When you ride at your FTP when you hit your limiting time you basically fall right off the cliff from a power output measure.
Once we know you FTP we can make workouts and "scale" them to your personal ability. The same workout can be then used by 1000's of people and they can get the same "difficulty" from it relative to their strength because of the scaling. TSS then tells us how much training stress you incurred relative to your strength. As you do this training.
Each week a person can only absorb so much TSS. Age, genetics, and fitness determine what you can handle. This is why there are Low, Medium and High volume plans. A single person can absorb more TSS when "in shape" than when "out of shape". So a beginner or someone lacking fitness will need to do a low volume plan. As they get stronger they can progress up to a Mid volume plan and eventually if they want to; a high volume plan. As we get older the high volume stuff becomes harder to maintain, and we some times have to drop back to the mid volume plan or lengthen the "Training Week" in the plans to be 8 days to insert extra rest days.
What do we mean by absorb TSS? That's the idea of exhaustion and recovery. As the TSS piles up you get more and more tired; and will struggle to exercise more and more. Aka fatigue. When you Rest and take the day off the body reacts to the TSS levels and adapts to become stronger out of fear that you might do that again in a few days. So each week we up the TSS then rest; then more TSS then rest. Each time we rest the body gets stronger. This is the important statement: training hard doesn't make you stronger. Resting AFTER training hard makes you stronger. If you never rest you don't improve. How often you need to rest is a function again of Age, Genetics and Fitness; and this is why there is a Low, Medium and High plan so that you can find one that walks the line between too little and too much rest.
Lastly we can only increase the TSS week over week for so long. Depending on the plan either week 4 or week 6 we have to "back off" on the TSS; because by the start of that week the athlete will be exhausted; so we do an easy week; by the end of the "easy" week the athlete feels better and becomes stronger.. (sometimes day 1 of the rest week is the worst of the entire 4 or 6 weeks block in terms of how you feel)....
After 4 or 6 weeks we then re-tested the Athletes FTP; if they got stronger then FTP goes up; this is important; follow along.
- Your FTP goes up
- The same workouts are now easier because you are stronger
- If nothing changed you'd accumulated less TSS relative to your strength
- Training would stall and you wouldn't get stronger
- Instead you tell the training software that you are stronger by putting in a higher FTP value
- The software sees the FTP increase and makes the workouts harder.
- The hard workouts now give you the correct TSS relative to your strength
- Your TSS is now accurate to your strength and you can continue to manage the "stimulus" you get from your training.
- It's important not to be "macho" about FTP it's just a measure and what ever yours is you have to train to that level;
- Don't compare FTP values to other people. Compare watts/kg over a time windows 1min, 5min, 20min, instead and if their's is better than yours then train harder.
So it's a cycle
- Measure fitness
- Train over a period of 4 to 6 weeks with increasing load relative to your fitness
- Rest to fully absorb and react to the training
- Re-measure fitness
- Scale workouts to new fitness
- Train over a period of 4 to 6 weeks with increasing load relative to your fitness
- Rest to fully absorb and react to the training
- Re-measure fitness
- repeat 2 to 4 four times a season then take a Big rest of 3-4 weeks off and start again.
Now with all that as a background.
The TSS in the plans tell you how much TSS each week will throw at you; this helps the experienced athlete figure out whether Low, Med or High volume is something they can handle. The IF value tells them how much each workout is going to Hurt. This is useful for getting physched up ahead of time so you can take it; and so you can plan you eating so you have the fuel on board for the effort. If you FTP is correct, an IF of 0.65 is a cake walk for most people. 0.80-0.85 hurts, and 0.95-1.1 is cursing at the coach and puking on the pedals hard.
There is a lot more but see if after a couple of reads this starts to make sense.
