Why not bike instead of run on easy days?

Specificity of training is important.

If you cannot run, then do what you can to train. As long as you're not overtraining, then any exercise is better than not.

Why can't you run when it's pitch black? I used to do it all the time

the point isnt just to raise your heart rate

your argument is like saying if the point of thershold runs is to raise your heart rat to 90% then why dont you just bike at 90%

A hr @ 90% of max is just an indication of the body is flushing out lactate at the same rate that it's producing it: that it's at LT. A hr @ 70% of max is just an indication that the body is promoting slow-twitch muscles, etc: that it's at the aerobic threshold. My point is that if the body does both those things on both a bike and while running, why not just bike? Like I said, hr is just an indication of actual physiologic adaptations, not the reason why you're doing the run. I probably worded it funny in the original post. Sorry.

Muscle memory issues.

because running (even on tired legs) is a technical skill

Specificity and muscle memory is the issue, but there's nothing wrong with the occasional substitute, if you're otherwise putting in the run miles. I good spin on the bike on your rest day can really help if you have a high level of run fatigue. It's low impact and loosens everything up.

Easy running isn't just about getting your heart rate up.

More running will improve your running performance, up to the point at which you get injured or overtrained. The tricky thing is identifying in advance when you'll reach that point.

Once you've done as much running as your body will tolerate, then there's some benefit in adding in some cross training.

Of course, given the choice between doing nothing and riding a bike, then sure - ride the bike.

Another thing to consider is whether you'd be better off spending the time doing some strength training.

Unless you're really short of time, it's not usually a choice between one or the other... most people have plenty of time for both. Just look at the stats for how much time people spend watching TV or surfing the web.

Many elites including East Africans use the spin bike more than what is reported.

JSLINDK wrote:

Specificity and muscle memory is the issue, but there's nothing wrong with the occasional substitute, if you're otherwise putting in the run miles. I good spin on the bike on your rest day can really help if you have a high level of run fatigue. It's low impact and loosens everything up.

I tend to agree with that.

Funny thing: Having a road HM in october, as well as due to a personnal preference of avoiding too remote trails when hunting season is on and a week of hollydays inbetween were I ran in a park, I mostly ran on roads/very smouth trails august through october.

I had a trail race early november, on more technical terrains (roots, cobbles...). I noticed my ankles and various ankle-stabilizing muscles were weaker than usual during that race. I simply hadn't done enough technical-trail-specific work.

From experience, for this specific part, running easy days on technical trails and putting on the milage is by far the most efficient training.

I would also argue that even if spinning works the calves, quads and glutes, it precisely lacks the impacts to build muscle, bones and joints strength. You can replace part of your easy running with spinning, especially if you are temporarilly hurt and need to take it easy on impacts, but I would also add some running drills to the regimen and you need to do running milage somewhen anyway.

anonanonanon1234 wrote:

A hr @ 90% of max is just an indication of the body is flushing out lactate at the same rate that it's producing it: that it's at LT. A hr @ 70% of max is just an indication that the body is promoting slow-twitch muscles, etc: that it's at the aerobic threshold. My point is that if the body does both those things on both a bike and while running, why not just bike? Like I said, hr is just an indication of actual physiologic adaptations, not the reason why you're doing the run. I probably worded it funny in the original post. Sorry.

You got some good replies so far. Read them and learn.

My little theory is that slow twitch muscle needs to be and can be trained every day. The purpose of easy runs is to train the slow twitch muscles without activating any of the big boys that help you run faster but that need more recovery

You can train fast twitch fibers every day. Tinman would say it's a good idea to train them more often. And if you are training for a championship which involves several round and a final on consecutive days, you need to practice that at some point in the build up.

You could build up to having several hard days and then several easy days for example

The point of the easy days is to recover. You should do them when you need them, when a faster pace would hurt your recovery.

hobby trail jogger wrote:

I would also argue that even if spinning works the calves, quads and glutes, it precisely lacks the impacts to build muscle, bones and joints strength. You can replace part of your easy running with spinning, especially if you are temporarilly hurt and need to take it easy on impacts, but I would also add some running drills to the regimen and you need to do running milage somewhen anyway.

Former triathlete here. I only got better in running when I started to change volume from biking/swimming into running. The biking and swimming gave me a good level of base fitness, and made me fit, but I could only run a 20:30 5k off that. As soon as I replaced biking miles and swimming miles with actual running, my running times improved massively and now I run 16:10 less than years after running 20:30.

Cycling builds immense quads and glutes. But not very helpful for running, which is a hamstring/calf activity primarily (and needs good form/posture). Very little transfer takes place, since the aerobic adaptions for mitochondria etc are all local and specific to the running motion.

Otherwise, cyclists would be the best runners. They train 40-50 hours a week, got insane quads and glutes and phenomenal cardiovascular systems. However, even Armstrong himself, was struggling to break 3 hours in his first marathon despite being optimally paced by El Guerrouj himself. With massive training, he got it down to the 2:40s, but that's still nothing compared to the amount of training he has put in his whole life (not even to mention PEDs). Average hobby joggers can reach 2:40s marathons on maybe 5-6 hours of training a week for 2-3 years, Armstrong trained 40+ hours a week for 20+ years and was still slower.

The good thing with cross-training is, you can get in more aerobic training, and burn more calories. So instead of doing 6 hours of running a week, you can do 6 hours running + 6 hours cycling, which will help you stay lean and improve your heart/CV system which is useful too. It's also great for general fitness.

LateRunnerPhil wrote:

Cycling builds immense quads and glutes. But not very helpful for running, which is a hamstring/calf activity primarily (and needs good form/posture). Very little transfer takes place, since the aerobic adaptions for mitochondria etc are all local and specific to the running motion.

Did you just make that up? Cycling mitochondria are different to running mitochondria? Really? Explain how?

What you can do is run easy in the morning and bike easy in the evening. Maybe throw in some core / weights & finish it off with stretching.

bs detection service wrote:

LateRunnerPhil wrote:

Cycling builds immense quads and glutes. But not very helpful for running, which is a hamstring/calf activity primarily (and needs good form/posture). Very little transfer takes place, since the aerobic adaptions for mitochondria etc are all local and specific to the running motion.

Did you just make that up? Cycling mitochondria are different to running mitochondria? Really? Explain how?

I just told you - mitochondria are developed in specific muscles. Biking primarily uses quads and glute contraction to produce force, running the hamstrings and calves. Or do you also think that swimming with a pull buoy is gonna help you build mitochondria in your legs that make you a faster runner? No, but it will make you fitter, work your upper body and burn calories (=indirect benefits that can make you a better runner).

LateRunnerPhil wrote:

bs detection service wrote:

Did you just make that up? Cycling mitochondria are different to running mitochondria? Really? Explain how?

I just told you - mitochondria are developed in specific muscles. Biking primarily uses quads and glute contraction to produce force, running the hamstrings and calves. Or do you also think that swimming with a pull buoy is gonna help you build mitochondria in your legs that make you a faster runner? No, but it will make you fitter, work your upper body and burn calories (=indirect benefits that can make you a better runner).

So now you're an expert on mitochondria too? Then explain to us what "building mitchondria" actually means?

And explain the difference in how specific muscles are used in running vs cycling in terms of force production and angle of pennation.

LateRunnerPhil wrote:

Average hobby joggers can reach 2:40s marathons on maybe 5-6 hours of training a week for 2-3 years.

When you spout total nonsense like this it pretty much invalidates anything else you have to say.

Interestingly, my personal experience was exactly the opposite. The problem for me is injuries. My joints just don't seem to be able to take the beating that daily runs bring. If I substitute an easy run with swimming/biking, I can get in more overall volume without getting injured, as you said. The quality days are that much better when my joints aren't bothering me. Running actually becomes more enjoyable. Its what works for me.

That said, I'm a bona fide hobby jogger, who's not even close to peak fitness, so really any aerobic training will benefit me. If I were, specificity would of course be the correct approach.

I do agree with what you are saying, but only if injuries aren't a consideration.