Impossible suggested workout SPRINT with Tacx Flux S

The aim of sprint training is to develop power in the sprinter. It’s not impossible to achieve 380W average power in 10s intervals if the sprinter has the strength to do so. The whole purpose of sprint training is to develop power. To develop power the sprinter has to get stronger and be able to apply that strength quicker. Once those two factors have been achieved then it becomes possible to average 380W and over in 10s.

So, while 380W average in 10s might seem difficult it’s not the fault of the device it’s the sprinter who needs to work on developing the strength and speed to achieve the target. Note also that when 10s sprints are suggested there is no target. In reality it’s head down and pedal as hard and as fast as possible.

It’s nothing to do with the training device.

Hi Philip,  you only read the headline of honzas post? The power intervals do not last long enough! 
ben

benfret said:

you only read the headline of honzas post?

No. There's a fundamental misunderstanding of the purpose of a short sprint interval. Simply put, it's about pushing as hard as possible for the 10s. It's not about chasing the average number. If a cyclist has the ability to achieve a very high power then the average over the time period is achievable. Depending on the cyclist it is quite possible that a maximum power for the sprint in excess of 500W might be required to get the average power required. The 380W average does not represent the maximum. It's not the resistance in the training device that is the issue. It's the ability of the cyclist to apply sufficient strength, quickly to the pedals to achieve the desired outcome.

Power is force x velocity. Simply put. applying more force into the pedal at the highest possible cadence will result in a higher average power for the duration of the sprint.

Dr Phil said:

It’s nothing to do with the training device.

I have a Neo 2 and can perform 10 second sprintervals in erg mode and hit my targets, but there is lag in the increasing resistance, overshoot of peak power, and then wobbly averaging over the 10 seconds to make the numbers. The lag at the start is matched by a corresponding lag at the end of the interval, so overall the sprint duration is about right, even though it lags the workout by a couple of seconds.

For a less capable trainer it might be better to forget erg and simply smash the pedals for a true "sprint" for 10 seconds and not worry about the sprint power number too much.

Here is an example of a Garmin 10 second sprinterval workout executed in Zwift.

By the way, the workout is the workout. It is not for the watch to second guess the trainer abilities and adjust the workout. Would it be any different with Trainer Road, Sufferfest etc? I don't use them, but I imagine not. If you really want to compensate for trainer shortcomings then you could always build your own custom sprint workouts. 

You wouldn't want to use a trainer where the resistance increased instantly. It would be like riding into a wall. Trainer manufacturers (not just Tacx) increase the power over a period of several seconds for a very good reason.

Most good coaches are aware of this lag in power, and design their training plans accordingly. Certainly Kevin Poulton (who wrote most of the Zwift training plans that feature in @eezytiger post)  would be aware of this.

Unfortunately, many athletes are not.

The workout is being executed pretty much as the coach intended.

Example power profile from Neo 2 10 second sprint with target 475W in erg mode.

I can do 500W, but the problem is, that the trainer is 5 seconds (after starting interval) increasing the resistance to desired 380W, no matter how fast and strong I'm cycling... So I'm on 380W only about half time of the interval.

honza_81 said:

but the problem is, that the trainer is 5 seconds (after starting interval) increasing the resistance to desired 380W,

And that's the way it should be.

Of course that it can't jump immediately to desired power, but it could start increasing the resistance 5 seconds before interval, so it will be possible to do whole interval at desired power. That's all.