Concurrent Training - Effects on Strength and Power

I got an email last week with a link to this article from the NSCA's Journal of Strength and Conditioning Research. It caught my attention because I've done "concurrent training" in the past and I'm currently tinkering in the weight room 2-3x a week while running and cycling. Further, it seems as though resistance training for runners is a hot topic as of late.

In my post from March on concurrent training, I essentially concluded that through a number of possible mechanisms, same session strength and endurance training may limit the adaptations that you would get from resistance training alone or in a separate session. For example, if you go for a 2 hour long run then completing plyometrics or a weight workout -- you may not get the benefits from that second workout to the same extent as you would if you had separated those workouts. Cellular signaling, fatigue/overtraining, decreased glycogen content may all be part of the reason. Think about it -- how many sets and reps can you squat at 70% 1RM? Now how many can you squat after a hard set of intervals, or a 2 hour long run at marathon pace? Then go do leg press, lunges, step-ups, etc. My point being -- endurance training may limit an athlete's strength, power, and muscular endurance when conducted immediately before resistance training. And if intensity is decreased, can an athlete get the same adaptations?

In the article linked above, two groups would perform concurrent training with a resistance training and an aerobic training component. One group, however, would also perform maximal effort cycling. It was hypothesized that "combining 3 modes of training (weight training, treadmill running, and maximal-effort cycling) would enhance strength and power."

Standing broad jump was used to assess lower-body power and seated chest press to assess upper-body strength.

The authors' hypothesis was proven incorrect.  The addition of 2 x 10-45s maximal effort cycling had no effect on standing broad jump or chest press. But the authors state, "The most significant piece of evidence supporting the hypothesis was the trend toward improved standing broad jump performance in the SEC group." That trend can be seen here: 

Standing broad jump (cm)

Maybe they would've found statistical significance if they had more subjects.

One key point we can take from this study: concurrent training did result in improvements in power and strength (though not significant). It is unfortunate that there was not a third, non-concurrent training group that only performed resistance training and/or maximal effort cycling to see if the concurrent training groups would improve a similar amount.

One problem I have with this study is that I hardly consider their concurrent training, "concurrent training." The subjects only performed 15:00 of aerobic running per session. For the competitive endurance athlete, 15:00 is not training; 15:00 is a short warm-up. I would like to see 60+ minutes of aerobic work. In total, all the training was completed in 45 minutes, and only done twice a week. I can't help but wonder if this data is applicable to competitive athletes who are training 10 or more hours per week. It only makes sense that adding maximal effort cycling 2x/wk would improve lower body power when the participants are only training an hour and a half a week. But once an athlete begins approaching overtraining or diminishing marginal returns... Then, where can the athlete get the biggest bang for his buck? Concurrent training or non-concurrent training? Same session, or alternate session? And so on...