Can anyone explain why running decreases your power output?

Ok, I generally run 4-6 miles 3 x a week with my soldiers in the morning. Sometimes as much as 5 times. I have found an interesting correlation. The bottom line is when I run in the AM (around 630) and then ride a 2 x 20 L4 in the evening, I am running around 20-30 watts lower in power on average then if not.

I recovery greatly during the day but has anyone else seen this effect from running? I have played with hard runs and softer runs and unless I am pulling anything quicker then a 6 minute mile, it does not matter what I do, I still average around 20-30 watts lower.

Finally, has anyone figured how in include a accurate TSS factor from a Polar 625/725 in WKO+?

The obvious answer to me is it's because you're doing two workouts in one day. Have you isolated running as a cause? What happens if you ride in the AM then evaluate power in the evening?

I've pretty much isolated the running by as you've stated, flipping the workouts a bit. The L4 training impedes the following mornings run a bit but not as proportionally as the running does the riding. With that said. do you think there value in working the legs runningwise to build power?

Try a cycling workout in the morning and then your cycling workout in the afternoon. What changes?

Or, try cycling in the morning and running in the afternoon.

Thirdly, stop running if you want to improve cycling. Cycle. (realizing that your n=1 survey will work for you...at least).

I don't have enough personal experience to answer properly.

I run in the winter for weight maintenance (it's hard to put in the bike km when it's dark and rainy) but I don't notice any improvement in cycling. Since there are different muscles and muscle motions in use I'm not shocked by that.

Power is sports specific to a great degree.
For example.... Lets talk about threshold power while cycling. It is not just a function of the cardiovascular system, it has much to do with what is happening at the cellular level in the leg muscles. While running does work the legs it doesn't work the legs in the "same" way cycling does...there are different loading forces, different angles, different quad and hamstring emphasis etc etc. Running works the quads pretty darn hard and also uses way "more" hamstrings than cycling. If you run up hill then the quads are very strongly worked. Calves are also worked more in running.

So to answer your question the answer is Yes and No. Yes it will help build power on the bike as it does work the legs in "some" ways that are the same as on the bike, and also you will be building your "general fitness" and increasing your VO2 max.
However, NO, it will not build power on the bike in the same way or to the same degree as training on the bike does.

The "cross over affect" is there to some degree when you go from an exercise where there one uses MORE muscle mass. ie: Running and Nordic skiing work more muscle mass in the legs than cycling does so the cross over affect to cycling is not bad. However, swimming does not cross over well to anything, since so little lower body mass is used. Cycling does not cross over very well to running or nordic skiing as less muscle mass is compared to these sports.

My recommendation to you is to do a trainer workout on the bike at least a hour before you run with the guys. Be sure to eat plenty of carbs after the trainer workout. Try 2 X 20 at just under your FTP.
As was mentioned, running before cycling in the day is not the ideal way to approach this. If you can't train on the bike before running then train on the bike after dinner at say 7 or 8 pm or just do L2 work or perhaps just L1 recovery rides for 30 minutes on the bike on running days.


You only have "so much" recuperative powers so a lot of running will hamper gains on the bike. Six miles three times a week is the most you should do. More than this and and you will be cutting into recuperative powers that could be used for cycling training. Also, your legs will always be fatigued as running really "hammers" them compared to an equal time on the bike(even at L4).

Fascinating.... Thanks for taking the time to put that together and it points me in the right direction. I take it when you say the running will hamper the gains on the bike, that is because the running does not allow for recuperation and thus the 'hammering' effect? Do you recommend sustained carb intake thru out the day to regen?

Running fatigues the legs quite a bit and it has less to do with glycogen depletion than plain old muscle fatigue/stress. Part of it also has to do with your total training stress from the running and the cycling.

It is more difficult to recover from a brisk hour run than an hour cycling at L4.

Some of the negative impact that running will have also has to do with your body type and biomechanics/efficiency during the running. If you are not "built" for running it will have MUCH MORE negative impact on your cycling.
Body weight?muscle mass also has a big impact in regards to how stressful a run will be for you. If you are above 170 lbs a brisk run can be tough, unless you are 6 feet tall or taller.
There is a reason why the top runners are sticks...like 5'6-11" and 120-140lbs!!!

A good carb intake throughout the day will help but what the legs will really need is time off to recover from the combined load of running and cycling.

So it might be best to simply not ride at all on running days or cycle before the run....that way if anything "suffers" during the day it will be your run and not your ride. But a ride before a run will have way less impact on running performance than the negative impact a run will have upon a ride, if done first in the day.

Do you, or anyone else, know how to get the TSS inputted into Cycling Peaks WKO+ from a Polar HRM? I download the data but it seems running is not really computed into TSS.

No, but I'd have thought that the pace of your running/intervals would be a more useful set of data than HR in order to approximate a running equivalent of TSS. Some have attempted to approximate TSS from HR data on the bike but it just doesn't work with enough precision. I'd make better guesstimates of TSS based on RPE than I would with HR.

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