@glevinso Yes, understand and agree with your points around reasons not to do such a long workout as a general practice. A bit more context around my PT's comments may help clarify:

I have been dealing with a recurring calf/achilles issue that is caused by a neurological problem. Specifically, my glute muscles don't always engage, particularly after long periods in hip flexion (eg 3 hr bike ride) . When the glute doesn't fire, then other muscles take over to do the work, such as my calf muscle. This leads to overuse problems, such as soreness, seizing, etc.

To combat this, PT has me doing strengthening work in the gym. I'm also doing frequent hip flexor stretches, immediately followed by glute activations ( a few quick squats) to train my body to make the transition from Hip flexion to glute activation more automatic for me.

With this in mind, I have made solid improvements, but the problem still occurs occasionally during long workouts. This season, as I trained for the Timberman race, I had an occurrence during mile 11 of a 13 mile Sunday long run. Most recently, during the Timberman race, I came off the bike feeling pretty good, but was hit with the calf cramping issue at mile 3 of the run segment and had to slow to almost a walking pace to bring it under control and I stayed at a reduced pace for the remaining 10 miles. Cost me roughly 15 minutes in my finishing time.

So the PT made 2 suggestions: 1) Be more vigilant in my stretching and drills, particularly pre workout, and 2) try to build up muscle endurance in the glutes to build up resistance to fatigue and the breakdown that seems to occurs during prolonged workouts. (3 hrs&)

Finally, my PT comes from a Gymnastics background and is not a triathlete, so she suggested I check with other sources, and perhaps a tri coach, to get suggestions on how to address this problem through training.

A bit long, but that's the context.