Originally Posted by kopride
Felt Rider is the king of mixing resistance and cycling. He may be able to give you a better idea of the effect of two a days; and which to do first.
I will take the safe approach and say, "it depends."
But if it were me and the goals that I have I would do strength training first if I had to do both within the same hours.
Why? Based on opinion and experience I see it like this.
1. Safety first - strength training takes good technique and focused concentration, which one has more when fresh. The more fatigued a person becomes the less focus on technique and focus is shifted toward surviving the interval or lift. In other words people tend to get sloppy with more fatigue. Lifting in general with free weights has greater risks and kettle bells even more so. Whereas, cycling one is at less risk because it is a bit more predictable. Of course outdoor cycling has its risks as well, but there is not as much technique and variability as there is in lifting.
2. Progressive training - if one is really focused in on gaining strength it is best to hit those heaviest lifts when fresh. When I was at my peak we did our warm up sets with just enough, but not too much so that we had our greatest strength available for the lift. Even too much warm up could distract from hitting those targets for the day.
However, the converse is true if cycling performance is the primary goal and one is doing higher intensity training from L4 or higher intervals. If one is lifting in a manner that fatigues the body and uses up stored energy those intense intervals following lifting are going to be harder and one might miss those targets as well. But if one is content with a milder aerobic cardio after lifting there should not be much of an issue.
Now another "but" to consider. But if one is doing a milder aerobic cardio after lifting it takes a whole lot more duration in order for it to have any sort of benefit to improved cycling performance. I will say that when I competed in bodybuilding that I was able to lift heavy and was able to do a short session of HIT/cardio after lifting fairly successfully. I could not do it the other way around by doing HIT/cardio first as I did not have enough in me to lift heavy or with a progressive load.
There is a lot to this subject and I am not a sports scientist so I best stop at those two comments. I will just say that I am glad to split resistance training (morning) apart from my cycling training (evening).
Just consider this is my opinion and it really goes back to "it depends" on your personal goals.
Best wishes