Interesting article on this same subject brought to my attention by
@Danny Moore
The Interference Effect: Can you Train Strength and Endurance Concurrently?
"avoid combining
hypertrophy strength training (i.e. 10+ reps) with
high intensity endurance training. That’s mainly where you’ll see an interference effect.
Low intensity endurance combined with
hypertrophy strength training (10+ reps) is acceptable. As well, you can combine
max strength training (5 reps or less) with high intensity endurance."
And from this I also infer that there would be no problem combining max strength training with low intensity endurance.
A bit of the reasoning on these combinations is briefly explained in the article.
I agree with
@Steve Freides that the statement "an endurance adaptation occurs at the expense of strength" is overly simplistic. I feel like I've been successfully combining endurance activity and strength training for several years now, and the longer I do it, the better it works. Now, are there some trade-offs? Yes... for example, where I really noticed a drop-off in my bike riding was last year when I was training for the TSC. Doing heavy deadlifts working towards a max, and regularly training pull-ups which are pretty difficult strength-wise for me, and also trying to peak on a 5-minute snatch... these are already conflicting demands which left my bike riding in the dust for a bit. Even then we're just talking about a 2 mph average difference for a regular bike ride, but endurance cyclists know that much is noticeable. A couple of months later when I eased up on the other training, it came back.
Edit: As for the Rippetoe article, I don't buy it -- I tend to believe Dr. Kenneth Jay about the dangers of strength training only, with regard to heart health. Cardio is necessary for us to be healthy, IMO.