How Hard is "Hard"?

Physiological rules guide training prescriptions. Different energy systems relate to each other in a predictable way. Training is designed to strengthen those energy systems and tailored to maximize the ones that are specific and necessary for success in your chosen events. But as in most of life, there are exceptions to the rules.

Individual athletes respond differently to the same training and even the same athlete responds differently over the years. If you’ve trained with us or followed the VQ information for some time, you’ve undoubtedly encountered the ideas of “building range” and “establishing reference points”. Both these ideas are aimed at trying to bring athletes closer to maximum achievable physiological parameters and making adjustments for individual variations.

So the question that arises is: how hard is “hard”? Consider the case of functional threshold power (FTP). By definition, this is the highest steady-state power that can be maintained for an extended time, usually at least 40-60 minutes. At VQ, we test FTP with a protocol of two 20-minute maximal efforts, taking 95% of the highest effort as your training FTP. Oftentimes, training percentages are further reduced by 5-10% to make them more manageable. Take, for example, a maximum 20-minute test result of 250 watts. This results in an FTP training value of 237 watts. On a workout of 3x15 minutes at 95%, you would be completing 3x15 minutes at 225 watts. Keeping in mind that you already produced 250 watts for 20 minutes and that the initial reduction theoretically adjusts this result to something that can be sustained for nearly an hour, you can see how it should be reasonable to complete the aforementioned workout 12 watts below that hour power mark.

That is not to say the workout will be easy, but it should be achievable. FTP serves as the reference point for training energy systems both above and below. At lower power outputs, effort can be maintained for a long time with proper pacing and fueling. But as power increases above FTP, the sustainable duration begins to decay rapidly.

Below you can see some typical markers we might use for different types of workouts and interval durations.


Power (% FTP)

Typical Effort Duration (and Total Effort Time in a Single Session)



3-5 hours



1-3 hours

Sweet Spot


20-30 minutes, 45-120 minutes in a workout



8-20 minutes, 30-60 minutes in a workout



4 minutes, 20-30 minutes in a workout


3 minutes, 15-30 minutes in a workout


2 minutes, 10-25 minutes in a workout


1 minute, 10-20 minutes in a workout


30 seconds, 10-15 minutes in a workout

How do your own power outputs for different durations compare to these baselines? At the upper end of the duration for each workout, that effort is going to become “hard”, but should, for the most part, remain achievable. Noticing specific areas where you are more challenged than others should help to indicate areas of your fitness that need some tuning up. Strong on the longer durations, but lacking on the short efforts?

More short, hard training with plenty of rest. Great range but you have difficulty holding power for longer efforts? Endurance and sub-threshold work should feature in your plan. If you find yourself consistently overperforming these baselines that might be an indication that your FTP reference point is too low and you need to re-evaluate it. On the other hand, if you find yourself often falling short or feeling like every workout is a hard one, this may point to the need for increased fitness across the board or perhaps that your FTP is not what it once was. (That’s why we encourage everyone to test regularly and update their FTP to reflect current fitness rather than trying to train at “summer numbers”.) Those final statements are intentionally overgeneralized. Training is, of course, much more complicated and dynamic than that and needs to be qualified by your real-life experience. It takes time to accumulate the necessary data to really know where your true capacity lies. A season should get you close, but you can’t truly compare the information until you’ve been through two years of consistent work.

Armed with that knowledge, you will approach workouts from a different perspective, making adjustments for your own physiology and being sure to work at intensities high enough to elicit desired changes.