I happened to run across a new Swedish study:
PLOS ONE: Endurance Exercise Enhances the Effect of Strength Training on Muscle Fiber Size and Protein Expression of Akt and mTOR

which found it's good to ride before lifting. Some of you here may know that I've been in favor of doing this for years. Riding first didn't hurt their increases in the weight room, plus they got much better muscle fiber development than those who did not ride first. Which is also what I've personally found.

interesting read.

I've always followed the "cardio after weights" philosophy for the fat loss benefits. Might have to switch it up a bit, I've a cycle home tonight so some weights might be the order of the day!

interesting stuff, thanks for the link

cycle erg + leg press + measure results in quads is very tightly focused

Was it 'endurance training' per se that helped or just extra volume of work for the quads?

What effect would the cycle endurance training have on hamstrings? glutes? upper body?

Would a few sets of leg extensions added to the leg presses have the same effect as leg press + cycle erg?

Sounds like the entire resistance workout was the leg presses. If it were a more realistic full body or even general legs workout would the fatigue from endurance training become a negative?

Interesting that the resistance only group had a reduction in slow twitch area. Would have expected a little hypertrophy.

I'm starting to prefer to run 5k on strength training days because it takes less time than riding. I can be home in half an hour vs having to put on special clothes, top off my tires, put shoes on, carry the bike up and down the stairs, and then ride enough to be worth it. It's sad because there's very little enjoyment in running.

The researchers made several interesting decisions and there is too much we don't know about the participants' activities outside the lab.

I surmise that one would not see that increase in CSA of the type 1 fibers without the endurance training, and it's endurance performance that road cyclists are after. In the gym, I'm an oddity in that I can do sets of 30 with relatively heavy weights if I want. So the type 1 fibers are in there working during the lifting program.

I would think that any muscle which is worked hard during endurance training would see the same effect as the quads saw in the study.

No, I don't think see any reason that other lifting exercises would so stimulate the type 1 fibers. Powerlifters have no use for type 1 fibers and they of course do many different weight exercises. During the off season, I do several different leg exercises. What one works gets stronger both on and off the bike. During the season I only do squats, single leg presses, and calf raises for leg exercises, though of course I also do upper body and core work.

You are right to wonder about the effect of adding the stress of lifting to an already full endurance training program. My practice has been to do weights twice a week during the off season and then once a week during my season. That works, in that during the off season I see nice steady increases in my weights and during the season, if I'm able to find the time to lift, my weights don't decrease. But that's a big if. Some weeks during the season I can't lift due to tours, vacation, or simply spare time limitations, so my max weights may fall off a little. That doesn't seem to negatively affect my endurance performance in the short term, though it does seem to hurt my sprint, about what one would expect.

I hear you. I usually do roller work on strength training days for exactly those reasons. Plus of course weather around here! One has to change clothes twice whether one runs or bikes, but biking does add a third change. I lay my clothes out ahead of time to make the transitions quicker. I have resistance on my rollers so I can do whatever interval work might be called for. I wouldn't say there's huge enjoyment in rollers, either. However there is the benefit of specificity.

From skimming the page I didn't really see enough to draw conclusions about the timing of the activities. They had a test group that did strength-only, and a test group that did cycling followed by lifting. But no test groups that did lifting followed by cycling or split the activities on different days.

That's a good point. However they did show that cycling first had no effect on performance during the weight workout. I believe was the point of the study: is concurrent training beneficial?

I've also tried cycling after the weight workout and can report that does have an effect on performance during the cycling workout so it's not as much fun. However whether one would get similar increases in type 1 and 2 CSAs with that protocol is unknown, as you say. Whether one would get performance increases from splitting the routines between two different days is beside the point. We know that many endurance athletes engage in endurance training on every day which is not a rest day.

Interesting that they fed the two groups different recovery drinks. The endurance-resistance group got protein + maltodextrin, while the resistance group got protein only.

Putting carbs in the recovery drink could have contributed to the difference.

I not sure anything can be ascertained from that study, except that you can do a little cardio and recover enough to do a very light, high rep rep weight session. And if there are nutritional differences between the two groups it would certainly invalidate the whole study. It's also questionable that the two groups did not do the exact same amount of training volume overall, because you are introducing other factors like hormonal response per time spent exercising (irrespective of the type of exercise performed). The study also used subjects who normally did not exercise regularly, so the results are of no value for those who already exercise on a regular basis.

Practical Considerations for Combining Cardio and Lifting ? Strengtheory

Cardio isn't going to kill your gains. Need more evidence? You got it. ? Strengtheory

"It could simply be that the added training volume from the cycling was the determining factor for the different hypertrophy responses."

This is the problem with the OP's study. The volume was low, and they were not trained previously. Also these are male 20-30 year old subjects. Basically any amount of training at less than 12 hours a day with enough nutrition and sleep is going to result in gains. I have never believed that a reasonable amount of cardio does anything to limit strength gains, and it is well known that light cardio can speed recovery. But a real study would need to include a greater age range, trained athletes, and have similar levels of nutrition and volume for all the subjects. For example, would a strength-strength group have the same gains as a cardio-strength group?

There's a fairly simple way to validate or invalidate the OP study for one's self: try it out. That is, if one has already been lifting regularly and can thus see any difference. True, it won't be scientific, but who cares?

I started training concurrently when I used a gym spin class. The classes were hard and taught by racers. My legs were rather jello-y after but I was already at the gym, so I tried lifting after the class. To my shock, the lifting went fine. No performance difference. Since I only have riding and rest days, the concurrent training came naturally and I've done it ever since. I've had pretty decent strength gains, even at 70, but interestingly not much size gain. That could be just my physiology or an effect of the endurance training, but it's a very good thing for a cyclist. Strength gains with no weight penalty is our dream!

My pre-lift workouts are usually an hour on the rollers, doing either recovery, steady-state endurance (VT1), speed work, short intervals, or one-legged pedaling. Lifting results were the same for all, as far as I could tell. I told myself it worked because lifting uses different energy systems, which might even have something to do with it. One thing I did notice was that after cycling, I had to have a bottle of sports drink at the gym to get good results, even though I didn't need anything while cycling. Otherwise my blood sugar dropped out. Which again could be just me, or some more universal effect.

Downside of concurrent training: one has to add in the training effect of lifting. I see a TSS of 30-40 for my in-season short lifting program.

My own experience is that it depends on what your goals are and your diet. If you are trying to develop pure power, limit the cardio to 30 minutes or less before the weight session and the day after to prevent delaying your recovery. If you goal is endurance, pretty much anything goes. For bulk, the more volume the better, provided you eat enough. Light cardio after strength training reduces recovery time regardless of what you are doing.

My approach has been to lift on my "rest" days, eg off-bike days. Usually I ride 5-6 days a week and lift once or twice week. Those 5-6 bike days include a polarized approach (eg easy or hard, not much tempo except group ride or racing on the weekend), with the day after weights usually being a really easy recovery spin that may gradually increase toward upper zone 2/VT1 if the legs feel like it (sometime they do, sometimes they don't). Interestingly, I found that riding hard on Sat/Sun doesn't really seem to interfere with lifting on Monday. When I first started this schedule, I would often go into the gym with the legs feeling flat/tired from the weekend's riding and being sure the weight workout was going to go poorly. But it just didn't happen.

I definitely can't do hard intervals on the bike the day after squats/deadlifts, though; hence the easy ride Tues, with interval work following on Weds.

Exactly. The point of the study was to say, "So try doing the weights immediately after a non-exhausting ride rather than spoiling a rest day with them." I agree, doing weights first or the previous day doesn't work. I once did heavy legs the night before going alpine skiing. Disaster. However I can ski 20,000', come home, ride the bike for an hour, and then lift just fine. Rest next day of course. I'll usually do the week's hard group ride on Sunday, recovery ride Monday, endurance, short intervals, OLP, or FastPedal Tuesday with weights after, then endurance Wednesday, intervals Thursday, recovery or cross training Friday, and rest Saturday. In winter, I also lift after the Thursday intervals.

Interesting. I work out sometimes at lunch between 7am & 4pm commutes but my aim is to maintain a lean body not grow muscle...or i think

I guess it partly depends on what works best for one's schedule. I don't have time to both lift and ride on weekdays, and my weekend rides don't qualify as "non-exhausting"; trying to lift on Sunday, for instance, after my morning interval workout would not be fun at all. So lifting on my "rest" days works best for me and I don't feel like this spoils them.