Niall

The following may be a little stupid and the answer that I just need to work very hard, but...

On the flat I find getting my heart rate above 85% and up to 90% quite difficult. I can maintain the rate once I get up there but just getting there is particularly hard on the legs. Now I know it's meant to be hard, that's the point, but I'm not necessarily out of breath getting up there or even maintaining it, just it seems hard to get it up there (much harder than if I was hammering up a hill).

The problem is worse on the turbo trainer where I end up on a high setting and having to use a relatively low cadence (I normally spin around the 90 mark for hard efforts outdoors), working my thighs pretty hard (or grinding!). I just can't seem to get my heart going whilst spinning.

Am 185cm and 62kg if that has any bearing on matters.

Any reasons for this or does my first sentence apply?

DannoXYZ 

Well, how long are you able to hold 85-90% effort? If it's more than 5-minutes, I'd say you're doing a darn good job! Keep it up!

To work out the heart more and save the legs, spin at 100rpm+, and use bigger gears on the trainer for more resistance.

Pelon

I have the same problem. Getting my heart rate up to 85 - 90% is no problem on the hills, but on the flats, my legs fatigue long before my heart rate gets up into that range. I'm wondering if working
on muscle endurance could help this problem?

Roody

Maybe I'm missing something but it seems pretty easy to me. First keep in mind that your heart starts beating faster after your leg muscles "tell" the heart that they need more blood to bring them more oxygen and glucose.

When you climb a hill, your legs are suddenly working much harder, so your heart starts to beat faster almost immediately. But when you hammer in the flats, your legs are not working quite as hard, so it takes longer for them to "tell" your heart to start beating faster. By the time the heart finally does start beating faster, your legs are already tired.

Niall

That makes sense. So how do I go about riding at high heart rates on the flat?

Do I just have to build up eack interval more gradually? ie start going hard but but not really hammering and wait for the heart to respond, then build it up to the required level

I presume a build-up period isn't included in references to lengths of intervals?

DannoXYZ 

I always do my intervals at a set intensity & speed, say 90-98% of an all-out sprint. HR starts at 50% and steadily climbs to 100% by the end. The distance or time of the interval is then based upon the intensity. At 98% and 28mph, I can hold for about 1 minute before max-HR stops me. At 95% and 27mph, I can hold for 2 minutes, etc.

The critical point is the LT, practice determining what speed/RPM combos you can hold for 20minutes+, that's your LT. Then structure your intervals at intensities above LT.

RiPHRaPH

what gearing are you using for this interval?
it is a lot easier when you are being pushed by someone else.

Blonde Warrior

I have this exact same thing happening to me both outdoor riding and on the trainer and was always wondering why. My legs will get tired way before I get winded. Once my heart rate gets to 85% it is not hard to sustain, but getting to 85% is hard on me.

Any advice?

DannoXYZ 

Sounds like you and the OP are pushing too big a gear. In general:

1. If lungs/heart hurts but legs feel fine, then use bigger/harder gears and mash the pedals harder

2. If legs hurt, but lungs/heart feels fine, then use smaller/easier gears and spin more

Difficulty in accelerating and getting sore legs by the time you get up to speed is typically a sign of using too big of a gear, so the solution is #2, spin easier gears faster. You can accelerate faster with lower leg-effort. It's just like in a car, downshifting to a lower gear and spinning the engine faster gives you faster acceleration.

alpe d'issaquah

Why not just do then on a hill? Your body can't really tell the difference. I actually ask this question because I don't have a trainer yet and the there are no flat roads that I can hammer along for 20 min.s without a traffic light etc. however there is a small mountain/hill that takes about 25 min. to climb. Opinions? Thanks

blue_nose

I personally prefer hill repeats for interval training.

However, there are many posters on BF that live in places where they do not have access to hills, so they have no choice to do their speed work on flat course or indoor trainers.