Back to Back longs - with cycling

"Anyone else notice this effect from back2backs where the 2nd is faster?"

Yes. This happens to me all the time. I'm not sure why it happens, though. FWIW, when I was doing Ironmans, I really believed that all the cycling helped my running. However, the opposite did not appear true (for me, at least).

increased blood volume from the previous long day without overworking the same muscles

my gut is telling me the biking is helping my running too although I don't find too many proponents to the strategy - most seem to argue specificity - but I'm wondering based on my data if the biking complements the running quite nicely.

I was thinking it might be blood volume. I do a homegrown routine to lower my heatrate in marathons by running in double sweats for about a dozen miles a few days before a marathon - the speed-boost effect is very similar to what I see in this back2back longs and I've always thought that was a blood volume effect.

Recently I saw others mention a concept of interleukin-6 (IL-6) benefit to training in a glycogen depleted state and thought maybe this is what was going on - or maybe both IL-6 and blood volume.

The speed-boost seems to go away after a few days whether from back2backs or from double sweats.

I agree with the specificity. Running more is best. But if running more is counterproductive for whatever reason (available time, injuries, etc.), then cycling may be a good "2nd or 3rd best" option.

on the different muscles point:

I seem to see the effect whether same or different muscles involved - true for Bike-Bike, Bike-Run and Run-Bike. I haven't tried Run-Run but I've seen anacodoal evidence in others that the same seems to be true although the pounding effect of back2back runs probably dilute the perceptions.

It is non-weight bearing (which actually weakens bones) and the excessive sweating causes the bones to loose large amounts of calcium over time, leading to osteopenia and osteoporosis of the legs, hips, and lower spine. This is no bull.

http://cyclingnutrition.blogspot.com/2007/11/cycling-and-osteoporosis.html

http://www.medindia.net/news/Cycling-Boosts-Osteoporosis-Risk-48179-1.htm

I have a 2004 Equinox 9 and had been riding for about a month because I believed it might help improve my aerobic capacity. My family doctor brought the above to my attention so I quit and just increased my mileage.

Thanks for the links - interesting articles - especially the part of loosing 200 mg / hour of sweating. Since my outage was in fact a stress fracture in the sacrum after a marathon where I did a 12 mile run 3 days prior trying to sweat as much as possible (worked for the speed - PR performance - but still - started a year off) --- the concept gives me some pause to think about - Ca replacement has not been a focus of mine.

Of course the studies were focussed on biking ONLY - not mixing running/biking but at least it's motivating me to go get some more Ca suppliments as my bottle ran out several months ago...

That's kind of a dumb reason to stop cycling. Consume more calcium and also do weight bearing exercise. We're on a running website, remember?

without rereading the articles (i read them last year), i don't think you have to worry too much about losing calcium.

professional cyclists spend hours and hours training, 5-6 hours a day sweating. you can lose a lot of luids training for 20-30 hours a week in the sun and the wind. . . not much to worry about with 6-8 hours a week on the bike. . .

So you're doing a 2.5-4 hour bike ride on friday and then doing a long run on saturday?

January/February weekends days ranged from 45 to 100 mile rides with typically two rides between fri/sat/sun. March/April I built up the long run on one of those days - had a couple good runs after biking day prior and two very lousy 20 miler runs before the bike. Mid April I did 180 miles over two days Sat/Sun (MS150) then went and jogged the Boston Marathon faster than any of my longruns to date at a very low heartrate average.

Now with the pattern established I plan my better running for the weekend and do a bikeride (45-55 miles) on Friday. Had a killer workout Sunday cranking out sub6 milers again at around mp heartrate - much slower running on Thursday before the bikeride.

I still appreciated the Calcium reminder. Even in running there is a lot of sweating - especially this time of year in humid Houston where I live - a little extra Ca focus during the summer maybe might have reduced the risk of the stress fracture after a summer of hot running. With this summer having a portion on the bike - even more important for me I would think - got my bottle of pills yesterday.