Just wanted to update this thread...
I've been a big fan of the XVest-84 lbs firefighter model obviously, just recently purchased and have been training with the V-MAX 150 lbs weighted vest from weightvest.com. Have been training power-walks and hill repeats mostly.
What I've noticed so far from the 150lbs vest...
-Stronger feet/ankles, this seems to be the first adaptation. My initial 1 mile walk with the 150lbs vest fatigued the feet muscle significantly, but after over a month I noticed the feet/ankles are very strong.
-Upper back strength, the traps are taxed quite a bit but haven't noticed much growth from the vest alone. The mid-upper back postural muscles are definitely popping out in different kinds of ways and I can feel it after a long walk.
-Core strength, needless to say walking with 150 lbs requires a lot of core stability. The endurance transfers nicely to keeping tight during squats.
-Conditioning, burning lots of calories for sure. Plus regular activities I have a lot more energy for which is a very nice benefit.
-It is painful. There's no denying that. Major downside is the nerve compression in the shoulders... I am going to have to weigh my options and see how it goes for the next few months.
-Makes me feel like I have overcome very challenging physical activity -- confidence in my strength/conditioning.
Longest walk so far was 2.2 miles including major hills. The first 5 minutes sucks because body hasn't responded to the weight, quads cramping abit -- could use a better warm up maybe. Then halfway through (on the way up the biggest hill) my lower back starts aching. Once I pass that sticking point, it seems like all the endorphins kick in and I'm just autopilot all the way home one step at a time.
I really can't say that complete benefits of using a weighted vest in this fashion. All I can say is that I'm testing it out and seeing what it does for me. I definitely have more mental fortitude from enduring these heavy walks (and now I know what it feels like to weigh 350lbs and powerwalk 2 miles). Overall the abs seems to be developing nicely and my squat continues to improve so I am happy.
Will keep updating in the next few months...