2x20 advice

A light bike doesn't replace good fitness.

Moderator: Moderator Team

Post Reply
Posts: 69
Joined: Sun Jan 24, 2010 10:34 pm


Hi all, looking for a bit of advice concerning my 2x20 intervals as I would like to make sure I am doing them correctly and getting the most out of the session.

I aim to complete one 90min 2x20 interval session on the trainer per week, the rest of the week is allocated to other indoor/outdoor workouts (SST, under & over threshold intervals and LSD/tempo rides, about 10-12hrs per wk) so to ensure I get enough recovery between workouts I limit it to one per week and usually the first workout of the week following a complete rest day.

I train by HR and RPE and at 42yo my current LTHR is 169 (I test usually every 4 weeks, i.e. 30min TT and take the avg HR of the final 20mins)

Here is a screen shot of the session I completed this morning showing HR and cadence, I have a good solid 30 min warm up and then complete 2x20min intervals with 5min RBI and then cool down, I have an avg HR of 160 for both intervals and my RPE feels like around 16-17/20. At the start of each interval I bring my HR up into Z4 and try to hold it mid zone and keep my cadence at about 90-95, towards the end of each interval I try to ramp it a bit, especially during the final interval after which I am pretty cooked.


How does this look in terms of being a good example of a LTHR workout, should I be aiming to push and try and maintain a higher avg HR during each interval i.e. deeper into Z4 closer to my LTHR?

Thanks for reading.
Last edited by ACDC on Wed Apr 04, 2012 2:35 pm, edited 1 time in total.

User avatar
Posts: 2585
Joined: Thu May 03, 2007 10:39 am

by Tapeworm

Quick question, when you, "At the start of each interval I bring my HR up into Z4 and try to hold it mid zone," how quickly does this occur?

By ramping HR too quickly the responding power can drop and then return but it will appear that the HR is steady.

Otherwise looks good.
"Physiology is all just propaganda and lies... all waiting to be disproven by the next study."
"I'm not a real doctor; But I am a real worm; I am an actual worm." - TMBG

by Weenie

Posts: 69
Joined: Sun Jan 24, 2010 10:34 pm


It usually take my about 2mins to bring my HR up to mid Z4 following my warm up (I include some 30 sec sprints >Z4 within my warm up and then cool down slightly Z2/Z3 for 5 mins before the interval)
"I can accept failure. Everyone fails at something. But I can't accept not trying."
Michael Jordan

Posts: 112
Joined: Fri Jul 11, 2008 12:53 pm

by Ste_S

Can't see the graph (blocked at my work). Normally for 2x20 your heart rate will start below threshold, then drift through and then above threshold to the end of the session.

Heart rate can be helpful to give you an idea of what Threshold feels like, after that I'd just rely on perceived exertion

User avatar
Posts: 3039
Joined: Sat Jan 03, 2009 9:43 pm
Location: Canada

by devinci

2min sounds a bit fast to get in z4 but it depends on the individual, your extensive warm up probably helps speeding up the hr response.

Fwiw, pay attention to trainer warm up. I know I need to add one or two resistance level on my trainer to maintain the same power for a given cadence. If your cadence increases it would be a good idea to add resistance. Going harder in the last 4-5min could be a good strategy to ensure you really work at threshold too.

Your RPE seams spot on

Posts: 69
Joined: Sun Jan 24, 2010 10:34 pm


Thanks for the replies, it's a great help to know I am heading in the right direction. I know what you mean about trainer warm up, I can feel it during the first 5-10 mins, I just adjust my gearing to suit and increase the resistance so that I can keep my cadence steady.

Posts: 301
Joined: Tue Sep 16, 2008 12:03 am
Location: Melbourne

by mvogt46

I used to do trainer intervals by HR as well, but as is well proven HR drift means that it is very hard (almost guess work) to hold a constant power for the 20min duration, especially by the second interval. I discovered that another unit of measurement on the trainer was speed, as while it's not 100% linear the speed vs. power relationship on an indoor trainer is fairly constant. Also using speed on a trainer removes pretty much most of the variability the results in it not being an accurate standard of measurement out on the road.

One method I used was to do a LT test on the trainer by average speed, then base my interval speed on this data.
To validate this I also borrowed a powertap a year ago and found that this method was remarkebly reliable. I have a Minoura, rim drive trainer by the way. Just another method to consider if you think you may be having difficulty judging your effort by RPE & HR.

Posts: 20
Joined: Wed Oct 06, 2010 8:52 am
Location: Sheffield, United Kingdom

by amaferanga

I suspect that if you could measure power during your sessions you'd be seeing a steady drop off through the interval before a blip upwards at the end.

I invested in a PowerTap a few years back to remove some of the uncertainty involved in training with HR or turbo trainer speed. I've since stopped using HR completely, but was still using it last year and here's an example of a 2x20 session on my turbo:


Power (the red line) was roughly constant, ramping up a little at the end of the first 20min and a bit more at the end of the second one, but note what HR (the blue line) does. And that was with 2 BIG fans blowing cold air at me, so it's not a cooling issue.

I would suggest you need to aim to reach your target HR after 5-10 minutes and work to keep your HR rising steadily throughout the 20 minutes, finishing several bpm above your target. Looking at the HR traces, it looks like you ramp your HR up quickly, then basically ease up until you pick the effort up again in the final few minutes, which I suspect is not really what you want to be doing.

by Weenie

Posts: 69
Joined: Sun Jan 24, 2010 10:34 pm


Thanks all, a great help, I have replaced the chart with the un-smoothed version which gives a much better picture of the session :thumbup: I aim to keep my speed on the trainer constant @ 18-19mph and cadence steady @ 90 rpm throughout the interval up to the end when I increase the effort, It's so tempting when you see your HR starting to climb slowly during the interval to back off on the speed just a little so your HR is constant :wink:

Post Reply
  • Similar Topics
    Last post