Threshold work: Intervals vs. Continuous

Correct me if I’m mistaken, as I recall, Lydiard favored continuous work below threshold to intervals. I’ve seen numerous Threshold Workouts structured with intervals ranging from 4 to 30 minutes. Am I missing something by doing this work (about 90% FTP) in a continuous (40 - 60 min’s) vs internal manner?

to give this a bump and as well to ask a somewhat similar question of the coaches @ryan @trevor here I have this one as well:
if you are trying to increase intervals in a weekly manner to progress say for instance you have a week 1 interval with 1 minute 130% of a threshold power of say 200, with 4 min RBI, time say 8 intervals. There are numerous ways to increase this to add weekly increments to your plan (one change hols all others same)
1- increase the threshold power so intervals are say 5% higher (in this case both high intensity and rest)
2- increase duration of high intensity interval but hold threshold power constant
3- reduce duration of rest interval
4 increase power of rest interval but hold intensity interval constant
5 increase the number of intervals
there of course are other options but let’s say these are the possible changes.
How would each of these changes impact the focus of the improvement? Would some improve say threshold more than endurance/ durability? What systems would different changes impact?

1- increase the threshold power so intervals are say 5% higher (in this case both high intensity and rest)
→ increases fatigue ,longer recovery needs, potentially further development of max power
2- increase duration of high intensity interval but hold threshold power constant
→ increases fatigue, will probably improve durability at high intensity
3- reduce duration of rest interval
→ increases fatigue, will support the development of aerobic system will doing intervals, might reduce power output (and effectiveness) of work bouts
4 increase power of rest interval but hold intensity interval constant
→ increases fatigue, will contribute more to aerobic system assuming rest interval power is within limits of aerobic system, probably improves recovery capability
5 increase the number of intervals
→ increases fatigue, may contribute to VO2 max development, probably increases high intensity durability.


thanks for the info that is very interesting feedback… it does help show how small things may have different impacts on training. It sort of goes to show how slight changes in a progression can have different impacts or outcomes. It all depends upon what your goal is.

Thanks for bumping the thread.

Any comments on continuous vs interval work at sub-threshold intensities?

‘Below threshold’ is a broad range covering both aerobic and anaerobic contributions.
The question is always: what is the goal of the session?
Continuous and intervals are both fine. But if you wish to build your aerobic capabilities, make sure the session as long as possible. You can also do that by starting with intervals and just continuing as long as you can say a comfortable place. Or include a few sub maximal accelerations in a long ride.

excellent info so far.

all I would really add is thinking of the sport you are training for, there needs to be attention paid to the variability index of the intervals to help carry the fitness into the competition.

So for mountain bike although I spend a lot of time working on my athletes endurance and tempo abilities, I need to make sure that some of the intervals have the right variability index before competition. Now I often use competition for just this in advance of peaking, but intervals can be built in a way to mimic competition VI


This IMO is one of the all time best Fast Talk episodes. There are so many nuggets of wisdom in it:

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Really interesting conversation with some excellent points. Always enjoy reading these threads when I can.

I only have one thing I think I can add to the conversation. What stood out to me is the first sentence in your question which contains “to increase intervals in a weekly manner”. It’s important to remember that we don’t adapt in a week. So, making significant changes in the intervals on a weekly basis is more likely to change the nature of the intervals and what energy systems they target - especially if you start changing the power significantly.

I’d recommend waiting at least three weeks before making any changes (I believe in his book, Joe Friel recommended six weeks with many interval types, but it’s been a bit since I read the book, so I may be remembering wrong.) Once you’ve progressed and you’re ready to bump up the intervals but still want to target the same systems, I recommend strongly that you either increase wattage (trying to keep heart rate the same) or add an extra repetition/set. If you’re doing threshold-focused work, then increasing the length of the interval is also a good option.

Hope that helps!


Excellent addition @trevor !

This is where structured training really helps. When progress stagnates you will see it in the data: time to move on.

I still use hr to structure my sessions. Power increases when i progress. No need to change the intervals during the entire year.

thanks for the reply, what I meant was to deal with progressive overload… or progressive load plain and simple. Most weekly plans do some sort of slight increase in some aspect of a workout incrementally week on week. The thought that struck me was related to how different changes (as was described in the podcast) related to load or duration of not only the work interval but also the rest intervals… which got me wondering about how they change to focus of the workout. If I want to improve my durability and ability to ride hard then recover which is best… (this is not a racing question but a group ride question). Last year it would be that I would get beaten up and eventually not be able to recover enough to the point it became a struggle to stay with the pack. I want to do better this year.

Fair enough. I’m thinking everything between 80% - 95% of FTP.

If I want to improve my durability and ability to ride hard then recover which is best

Aerobic capacity is your friend.
You might also need to try longer threshold intervals.

I have been working more on longer intervals, and I try to use my heart rate as a guide for recovery. I try to get back to about 75% of HRM in the interval longer just seems to me to be wasted time since once I reach that point I am easily ready to repeat a 5 minute interval as long as it is not an all out effort. I find longer than 10 minutes starts to get too boring on the trainer.

Sounds great. I never understood those who take more rest after HR is back in zone 2. At least in my own training, I don’t see higher work bout power if I rest longer. I consider longer rest as a wasted opportunity to train the aerobic system.
I have to admin, during group training extra rest is nice for talking…group training is bad for training :wink:

yes that seems to be the problem with most training programs that are power based. They do not have the ability to react to heart rate… One way I guess is to use the advance button in a workout, watch heart rate and when it hits the recovery point advance to the next intensity interval then repeat, only the amount of recovery needed to drop back to that base range.

I have played around with recovering to a certain heart rate - say 65% of max.

Try during an endurance ride - every 15m stop and check recovery time (it shouldn’t be long.

Then try same during a tempo ride - whatever interval duration you are using, after that stop and recover to the 65% and time it.

Then same for threshold.

I have found that once this recovery gets beyond 90s the workout should be over. This seems to agree with what I see in muscle oxygen sat as well.

I have also found that it is a great way to progress tempo durations.

If you do 20m of tempo, recovery in 40s go again, recover in 75s go again, recover past 90s? how much tempo work did you get in? exceed your goal? less than you thought?


that is interesting, I get to 75% pretty fast but to 65% is a longer time to reach or get close. Again I think some of that relates, most probably, to over all fitness? So this might be a great thing to track as well. There is this thing called an LSCT (Lamberts Submaximal Cycling Test) that you do based upon heart rate and the last step is a 90 second rest and watch the rate of decline in heart rate, the other steps are to see what power is at those defined heart rates. edited to add: What I meant to add was the LSCT may be a way to see heart rate recovery timing… the last stage of LSCT is 90% of HR max

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Hi @scooter, you bring up some really good points. I’m a big fan of increasing the overall training stress across a three four weeks, so I hear what you’re saying.

Personally, how I increase it depends on the point in the year and what we’re focused on. In the base season, I won’t touch the interval work very much. It’ll stay constant (at most add an additional set.) What I’ll focus on, to increase training stress, is volume and maybe adding some sweet spot work to the long rides on the big weeks. During the season, I’ll focus a little more on increasing intensity on the bigger weeks. But again, I’ll tend to do that by adding a third interval session vs making big changes to the individual interval days.

One thing I’d recommend against is increasing the power of the recovery phases in your interval workouts. The purpose of those recoveries is to allow you to get ready for the next interval and being able to do it at highest quality. Trying to go harder during those recoveries just puts you in an “in-between” place and will hurt the quality of the part of the workout that counts.

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Thanks for that reply @trevor I appreciate your input on my question. It just struck me as I looked at my workout calendar plan that there were more than one way to increase workload, and they are probably not equivalent and as you point out in the case of increasing the power setting upward during recovery is likely counter productive.