Should my FTP Drop on my TT Bike?
Updated: Jan 18, 2021
A competitive cyclist came to see me with discomfort on his time trial (TT) bike and concerns about producing less power than on his road bike. When I asked how much less power, it was roughly 20% less! (He uses a power meter on both bikes). His previous coach was happy to accept “some” power loss on his TT bike, which prompts the question “should I be losing any power on my TT bike compared to my road bike?” and if so “how much would be normal or acceptable?”
The short answer to these questions is NO! Your ability to generate power should be the same with two caveats:
1. Your position on the TT bike is optimised and
2. You have practised riding your TT bike regularly to allow ADPATATION to the position, since the TT position is significantly more demanding on your musculoskeletal system.
This fellow was losing such significant amounts of power due to a poor TT position, and once corrected his FTP was equal on both bikes and his TT speed faster (which is the name of the game). This is not an uncommon story, so it’s worth digging deeper as to why a TT position may not let a rider produce full power.
For a TT bike fit the goal is always to create a position that allows the rider to go as fast as possible for the target distance. To arrive at the best TT position for fastest speeds, the dual needs of power production and aerodynamics must be considered whilst maintaining a level of comfort. Most often errors come from an obsession with the aerodynamic side of the equation without understanding how a minor change in position can make a large negative change in power generating capacity. If an aero obsession sounds like you, please remember that there are no prizes for the most aero position, just the fastest time. Sacrificing power for a perceived aero benefit makes no sense – you are seeking the “sweet spot” balancing the too variables that is sustainable in terms of comfort over your distance to optimise your TT speed. This balance may shift as the target distance shifts, with the extremes of distance being a 4km individual pursuit (IP) position on the velodrome versus the 180km time trial in an iron man triathlon. The more aggressive IP position simply is not comfortable enough for a 180km event! However the principles of fitting remain the same.
If a rider is fitting themselves to their TT rig, and if we assume that the rider has actually attained their optimal saddle height, to improve aerodynamics most will look to lower their handlebar position. This closes the hip angle (in simple terms this means that your knee starts to hit your chest at the top of the pedal stroke). Closing the hip reduces the power you can produce and greatly increases the chance of being uncomfortable or injured (both of which will further reduce your power). If the hip angle is overly closed it will compromise spinal posture and consequently may impair your ability to breathe, both having a negative impact on performance. The spinal posture typically ends up rounded (changing the lever arms of the gluteals, hamstrings and rectus femoris portion of the quads) instead of having a relatively flat back, and the hips may well start rocking. The typical response to remedy this is to move the saddle forwards to help open the hip angle. And that’s about as far as a self-fitting athlete gets, without ever measuring their own musculoskeletal attributes, their own torso or hip angles (which by the way is near impossible to do on yourself whilst pedalling), and as a result the rider is unable to obtain a great position except by sheer fluke.
If we think further about this scenario, it raises another set of relevant questions like “how far is too far forwards, and why?”, and “how low is too low such that power loss negates any aero benefit?” For me it also raises key questions such as “can the athletes body actually handle the position?” and “has crank length been considered?” And “how do all of these variables interact?” And they do!
Can you position your saddle too far forwards – of course you can! You’ll end up with too much pressure on your knees, poor recruitment of the gluteals and hamstrings, and too much weight on the front wheel which destroys bike handling. It places too much weight on your upper body leading neck and upper quadrant complaints.
Handlebar drop (or more accurately elbow pad position) is an important and misunderstood concept. It’s not often that I see someone who is too high relative to their own flexibility or strength (this is different to someone who is appropriately high because they are very tight, and in some cases so high that they would be better off using a road bike until they address their own musculoskeletal limiters). Too low is a frequent issue, and more recent field tests measuring the coefficient of drag (otherwise known as Cda, a measure of aerodynamics) suggest the most common positional change to improve aerodynamic drag is raising the bars, not lowering! Too low not only kills your power and comfort but also changes the shape of airflow over your curved back, increasing turbulence and drag. Speed usually comes from a better spinal posture (flatter back) to smooth the airflow and obtain a lower level of drag.
The amount of handlebar drop that is optimal for an individual is highly dependent on both crank length and the riders personal musculoskeletal attributes like flexibility and strength. If you are tight, and hamstring tightness is common to the point of being almost universal in triathletes, then your ability to get low is compromised (if you can’t touch your toes the chances of riding a reasonable handlebar drop on your TT bike are minimal). The only way around this is a shorter crank length so your knee isn’t pushed up into your chest at the top of the pedal stroke. Consequently a more common difference between a road and TT position is crank length, particularly if your hip flexibility is less than ideal. The tighter you are the shorter the cranks will need to be in order to obtain an aerodynamic position. Before you “have a go” at guessing how short you might need, please come in and get professionally fitted before you make an expensive error.
This leads into yet another massive consideration for TT positioning, and that is your muscular system. The main driving muscles when pedalling are your quads, gluteals and hamstrings, and the goal of a great bike fit is to allow each of these large muscle groups to perform optimally. When you lower the torso angle on your TT bike, you change the length (or level of stretch) for your hip muscles which will have to contract at a longer length. Muscles have a well-documented “length-tension relationship”, which means that how hard they contract depends on what length (or amount of stretch) you are trying to work them at. At extremes of stretch muscles lose power, which is exactly what happens on your TT bike if your bars are too low or your cranks are too long (or both). It is also what happens when someone whose muscles are tight (ie too short) copies the position that someone really flexible can attain – relatively speaking their tighter muscles are at an extreme level of stretch and produce less power. Even once we get all of these factors right, the difference in posture, joint angles, length-tension relationship and overall positon means that riders need some time each week on their TT rigs to ADAPT to the position so that their muscles can learn to produce seated power at the slightly longer lengths compared to their road position. Everyone acutely (ie immediately) loses a small amount of power once your torso is lowered and hip angle is closed (according to the 3 scientific investigations performed to date), but providing the angles are not excessive and you adapt to the position over several weeks, your power will come back up.
You shouldn’t ignore you own bodies capabilities or try to mimic someone else.
Your body is unique and so is your TT position.
Once you’ve spent 4-6 weeks regularly riding your TT bike, should your FTP drop compared to your road bike? No! Unless your bike fit is wrong, it should be pretty much the same (assuming you tested it in the same conditions). If it’s not then you need a bike fit now. Spending loads of money on a second bike, on coaching and huge effort training only to be in a terrible position makes no sense.
Want to understand more about your body, bike fitting for performance and injury management? Start with this article by David Wadsworth: