I have noticed that many of the recommended efforts that are listed in the endurance programming are based on Max HR. For years I had based my own training on Lactate Threshold. Is there more benefit in focusing solely on Max HR?
We started using Max Heart Rate (MHR) - an absolute value - to simplify discussion and programming for those who either can't or won't test to learn lactate threshold data (and continue doing so to adjust intensity as that value changes). MHR is a fairly stable figure and simple for people to test. However, it isn't accurate enough to cause precise adaptations as one nears the limit of his/her potential. Upon reaching that point, the athlete who needs it can begin using more refined guidelines.
If you have been basing training on your LT value, and stayed on top of testing to adapt intensity as that value changes over the course of a training cycle, and you have had good benefit from it, then don't switch to MHR - especially if you are satisfied with the progress you have made. However, if you are stagnating it may be time to take a look at some other ideas.
I spent a couple of years enslaved to the data from the power meter on my bike. Having the equivalent of One-Rep Max information for every duration (5-seconds to 60-minute) allowed me to scale output accordingly and to design training to target specific characteristics. A few experiences made me evaluate whether I used those numbers as tools to progress or if the fact they were lodged in my brain and appeared objective and certain actually held me back. Too much emphasis on HR data can affect one in the same way. A fellow racer was in the break with a couple of guys two seasons ago, pushing really hard. At a certain point he realized he had been over his tested max HR for a couple of minutes and voluntarily dialed back to preserve himself. The break went up the road and he never saw them again. What might have happened if he hadn't been so connected to the HRM?
When I saw this stuff happening I gave the power meter away and went back to training by feel. The following year (2010) I had my best racing season ever. I knew which aspects of fitness kept me from racing well. I also knew that - like everyone else - I tended to do what I liked and not what I needed. Doing what's necessary to improve fitness is painful in the moment. Doing the same thing over and over to no benefit is only painful on race day. Training by feel requires more self-discipline and honesty than using a power meter or HRM to define the work but ultimately, training by feel is more appropriate: the body knows what condition it is in, what it can tolerate, what it needs with far greater accuracy than conscious thought can comprehend.
Circling back to the lactate threshold, no matter what metric you use, it is worth examining what does what when we choose a particular training intensity. Does working at 101-105% of LT drag that "threshold" upward? Does working at 90-95% of it push it upward? And how does work done at 75-85% of LT affect that threshold in the long term? Does the long, easy stuff really give the best bang for the buck, or are 3x20-minute intervals done at 5% below threshold where the magic is? And for Ultra distance efforts, how much do we really need to even consider the notion of LT other than to avoid it like the plague on race day?