Cycling it littered with TLAs (3 letter acronyms), of them all FTP is the one that draws cyclists and triathletes focus the most; to improve, to passively love and hate, to pretend to ignore and to generally obsess over! As a reminder FTP or Functional Threshold Power is defined by Andy Coggan as;
“FTP is the highest power that a rider can maintain in a quasi-steady state without fatiguing for approximately one hour. When power exceeds FTP, fatigue will occur much sooner, whereas power just below FTP can be maintained considerably longer”.
A more holistic acronym to pay attention to is W/Kg (watts / kilograms). Put simply W/Kg is you Power to Weight Ratio.
The benefits of reviewing this metric allow you to identify strengths and weaknesses across your Power Profile. Typically, your W/Kg are calculated for the following durations; 20 minutes, 5 minutes, 1 minute and 5 seconds. A hill climber or triathlete would have more focus on their longer durations vs. a track or crit racer whose focus would be on the shorter durations. Knowing these numbers provides an important insight into your data which you can relate to your cycling discipline and future events.
From a coaching perspective W/Kg lets coaches compare riders with different body compositions. For example:
Rider 1 who is 120lb with an FTP of 175 has a W/Kg 3.14
Rider 2 who is 175lb with an FTP of 260 has a W/Kg 3.38
Rider 3 who is 220lb with an FTP of 325 FTP W/Kg W/Kg 3.25
There are only three ways in which you can change in your W/kg:
- An increase in power output with a constant weight
- A decrease in weight with a constant power output
- An increase in power output and a decreased weight
There is a priority, depending on the athlete, on which way is the best way. At face value the low hanging fruit is to lose weight however particularly lean athletes should be cautioned as a loss in weight can also result in a loss in power. An alternative is to improve muscular strength, not through more cycling, but by focused gym/weight work
An increase in lean muscle and reduction in body fat will improve your strength to weight ratio. A tertiary benefit is the increase in water retention. Muscles retain 7X the volume of water compared to fat. This is a huge number when you factor in that a 3% loss in weight due to dehydration can have an 8% loss in performance! If you have ever weighed yourself before a long ride and then weighed yourself when you have finished, you may have seen that number change significantly.
To continue with our rider examples
Rider 1 who is 120lb would drop to 116.4lbs a 3.6lb loss
Rider 2 who is 175lb would drop to 119.7lbs a 5.3lb loss
Rider 3 who is 220lb would drop to 213.4lbs a 6.6lb loss
This is something that is easily done on a 3-4 hour ride in June and is why Tour de France riders get through two bidons an hour!
These change in your body’s composition also has additional cellular adaptations. As you improve your Power Profile through sprints, intervals, hill repeats and strength training you’re also changing the way your body consumes oxygen and processes lactate. Your uptake of oxygen also known as VO2Max increases as you build strength and aerobic capacity. This increase lets you hold a VO2 effort for longer…or put another way, go harder for longer! Now you see why we sprinkle in those 125 and 150% FTP efforts!
So you may ask how does this translate to the road…literally? Well, if your focus is on flat Time Trials, then FTP should be your metric of choice. If you are riding anything that goes up or down using W/Kg allows you to highlight your strengths and identify your weaknesses over a complete Power Profile vs. a static pin on the Profile and lets you compare yourself to others on an apples to apples basis
FTP is really on part of the equation and only tells half the story. Using W/kg normalizes different athletes’ sizes and strengths. It provides an outline of the athlete, a charcoal sketch if you like…
If you’re looking for more detail with color, texture and depth that really creates a complete picture then W/Kg should be your metric of choice!