Coming back off injury and have been doing back to back longs most weekends this year. Initially this was 2.5-4 hour bike rides but later as the running came back it was Bike/Run or Run/Bike combos. What I noticed is the second long was near always the better of the two - HR was lower and I went faster/stronger. As I get my speed back in running I'm finding my weekend running is much improved if I throw a long bikeride in on Friday. I've been experimenting with trying to maximize the effect - seems even more so if I go to depletion on this bikeride with minimal carbs.
Since biking creates little pounding fatigue I'm considering maintaining this practice as I transition into marathon training for the fall. The running before this depletion bikeride vs after seem night and day - I run much faster for the same heartrate (~30 sec/mile faster). I'm still at pretty low mileage (30-40 mpw) but the former speed is about 90% back.
Is this effect from improved fatburning caused by the depletion?
Anyone else notice this effect from back2backs where the 2nd is faster?
Background on me - I'm a 2:39 master marathoner coming back from a little over a year off injury outage. On another angle to this strategy - I'm feeling a bit injury averse so if changing out 25% of my training load with biking gives nearly same benefits I'd sign up for that training program as an injury prevention measure. I'm wondering if at 43 swapping out some of the pounding with cycling just makes sense.