I'm wondering if steady state exercise at 60-70% percent of hr max is enough to improve an athletes aerobic capacity. From what I understand MAF pace is most effective.
Thanks!
It depends.
What sport? What's the athlete's training history? How much 60-70%MHR work have they been doing? How much would be added? Is there a performance issue?
It might also depend on what you mean by aerobic capacity.
To me it means (from Training for the Uphill Athlete) "the ability of the main locomotive muscles' ability to produce ATP via aerobic metabolism." If you mean this, then yes, steady state @ 60-70%MHR will improve aerobic capacity (you will have a bigger and better aerobic engine), depending on the steady state and the athlete's needs. Maffetone's HR estimation generally puts someone in these heart rate range. My personal predilection is to base this off of breathing rather than heart rate, but properly applied you end up in a similar place.
Some people use aerobic capacity to basically refer to VO2 max training, which I would call (again based on TFTUA) aerobic utilization. If you mean this (does slow steady state improve max VO2) I would side step the question and suggest training to improve VO2 max might not be the best use of an athlete's time - working to improve an athlete's VO2 max might not be correlated to improved performance.
For me, in both cases, the question becomes "Does steady state in the 60-70%MHR improve the athlete's performance?" and that is HIGHLY dependent on the sport and athlete in question... Although in general I would recommend including some in training as it has a lot of indirect value (such as health related, but also the ability to recover from training bouts quicker). But again, very athlete and sport dependent, as well as what you are looking to get out of it.
I want to caveat by saying that I have minimal work with athletes and none working with high level athletes.