Force v Power for Ironman bike training


Swimming a little too fast during the Ironman will not kill your end results… Over-biking will.

Implications for Ironman Bike Training

This article about Ironman bike training is designed to take you through the difference in ‘force’ and ‘power’ work in cycling, giving you the knowledge to manage and optimise your training load and ultimately improve your racing.

What is ‘Power’ = (+Speed x Force)

In cycling terms • High-speed = cadence (90/ 105 rpm) • Force = amount of load exerted through the whole pedal revolution


With power sessions you will see a higher elevated heart rate and increased oxygen consumption. This is due to the higher total energy output (measured in watts), leading to greater reliance on glycogen for energy. Moreover it is believed you will be recruiting more type 1a and b fibers (Slow twitch). Currently more work still needs to be done in this area to determining exactly what goes on at cell level during the two different types of session.

Taking your FTP (Functional threshold power) as your moderate power, we can increase the power output by a level (15/30w or 15–20 BPM heart rate) to elicit top end Ironman power (To go beyond this will produce neuromuscular power i.e. sprinting type work). This type of work (see below) makes you stronger/more powerful and thus increases the size of your “cycling engine”.

Ironman Power Sets:

When training for Ironman your high-intensity sessions (H I S) are around one training level above your aerobic threshold or FTP. While average training for Olympic distance H I S will be two levels higher or the 70.3 athletes possibly one level higher - both these latter athletes tapping into some lactate tolerance work and recruiting more total fibres.

Be careful when training for ironman as going into the higher intensity training zones (at or above FTP) will eat up precious energy that may be needed specifically for the endurance type sessions.  Remember we don't have an infinite amount of energy, smashing yourself today will leave you asking harder questions tomorrow.

Look to do the longer reps at the start of each training phase (Four week block) and the shorter reps as you fatigue towards the end, prior to the recovery or “freshening up” phase.

Phase one: 1. 4 x 6mins @ +FTP with 1:1 rec (6mins) 2. 6 x 4mins @ +FTP with 3mins rec Phase two: 3. 4 x 8mins @+FTP with 8mins easy spin between 4. 8 x 4mins @ +FTP with 4mins rec Phase three: 5. 4 x 10mins @ +FTP with 10mins spin between 6. 8 x 5mins @ +FTP with 5mins recovery between Race week: 7. 2nd to last bike session in race week 4 x 3mins @ FTP 6+ min rec between 8. Last bike session in race week = 4 x 90 sec’s @ FTP 3+ min rec between

What is ‘Force’? (-Speed x force)

In cycling terms • Low Speed = Cadence (55-75 rpm) • Force = Amount of load/ torque exerted through whole pedal revolution.

With force sessions, you’ll see a much lower heart rate and oxygen consumption than power sessions. This is due to the lower cadence and the possible recruitment of more type 2a & b fibres (Fast twitch). Cycling is obviously an endurance sport, but due to the greater ‘load’ exerted during high force/ low cadence work, it makes sense that more or different fibres will be recruited. Moreover, this is a much better cadence to enhance fat burning capabilities of the athlete, due to the lower heart rate, a key reason many Ironman athletes adopt this lower riding cadence.

Most athletes are quite surprised the first time they go out onto the road and do a live force session. As for quite minimal relative effort they can see power and speeds way in excess of that normally seen during higher cadence rides. Then their first thought is “wow – if I can do this for the whole Ironman I will smash my bike PB” and they’re not wrong, however it comes with a warning…

Warning: It is key you maintain a smooth and full revolution when doing force work, maintaining optimum torque throughout the pedalling action. If you start pedalling squares (just pushing the foot down), forgetting the momentum phase (hip flexors/hamstrings) you will fatigue your quads very quickly and possibly blow up.

Using watts (power meter) as a gauge: Because you are now taking away part of that power equation and dropping the speed element (i.e. taking your cadence down) we have to adjust our thinking on power (watts). As you begin to do force workouts I would recommend putting your bike into the biggest (hardest) gear you feel you can move at the given cadence and rolling that gear. Rolling a big gear is a skill and trying to “muscle it” will end in disaster - master the skill, don’t muscle it.

Ironman forced sets: Look to do longer reps similarly to the power sessions at the start of the phase of training and the shorter rep’s as you fatigue towards the end, prior to freshening up.

Phase one: 1. 3 x 15mins @ 65 rpm 3.30 min rec 2. 5 x 8 mins @ 55 rpm with 2min rec Phase two: 3. 3 x 30 mins @ 65 rpm with 7mins easy spin 4. 8 x 11 mins @ 55 rpm with 3mins easy spin Phase three: 5. 3 x 45 mins @ 65 rpm with 10 mins easy spin between 6. 11 x 15 mins @ 55 rpm with 4 mins easy spin between Race week: 1. 2nd to last bike session in race week 4 x 3mins @ FTP 6+ min rec between 2. Last bike session in race week = 4 x 90 sec’s @ FTP 3+ min rec between

Power or force for me? Simply… Both. No matter what you’re going to do on race day you need to train both sides of the cycling coin. Similarly to preparing for swimming and running, you want to tap into all energy systems. You would not neglect speed work in the pool or with your running, right? Similarly with power and force work, both need to be trained.

Personally I like the guys I’m coaching to alternate one week to the next, if during profiling we have established they have a weakness in one area and the other, we will lean more towards that area when we can.

What cadence is best for you? This is not an easy question to answer and there’s not a one size that fits all. For example imagine you have two athletes - both have to lift one time (1000 kg) on a bar, you can either put on a heavy weight and lift a few times (10×100 kg) or you put on a lighter weight and lift many more times (20×50 kg). Both will give you the same end result however you the athlete will be better suited to one type of lift or the other.

Elite ITU Elites cycling in the Olympic distance triathlon required high speed and power output for the front packs. On some courses you may have 15 dead turns per lap on a flat course, or, for example, the Rio course has 8 x 25% incline. You’ll find it very difficult to ride this type of course and stay in a pack at 55-65 rpm! Therefore I would suggest maintaining a high cadence 90-95+.

Junior or new to cycling: Young athletes or athletes new to cycling need to learn optimum cycling revolution, developing the cycling neural pathways. Therefore doing lots of skill work, single leg drills/ spin ups etc will help enhance this neural adaptation thus elicit a smoother cycling revolution. A great initiative British triathlon have started is to restrict the gears of young riders, similar to that seen in cycling thus making “spinning” the gear the aim not becoming more powerful as they need to develop running legs.

Bigger or more powerful athletes: Possibly low cadence and take advantage of the unique fiber type/strength and ride around 65-75 rpm.

Lighter cardiovascular superior athletes: Possibly look to use a high cadence this time take advantage of their well-developed cardiovascular system riding around 90-95 rpm.

Happy medium: A rider who is not at the extreme end of either spectrum may look to ride at or around 80 rpm. Personally I like to ride with a little bit more rhythm than that seen in the lower end cadence, but not spinning too high cadence thus riding around 80 rpm.

The key here is to learn about you the rider and use both ends of the spectrum during training, working out which is better for you. Moreover, humans have some muscle fibres that are trainable (they can become more fast or slow twitch depending on the prescribed exercise) so even if you have a history of one type of cadence or the other, with training you may feel you are drawn the opposite way because that is better performance outcome for you the individual.

Happy riding!