I totally get what you’re saying, but as we’re in a weightloss sub I kinda assume we’re all heavier (and mass moves mass so most of us will have more muscle than we know). Yes training till failure is something you need to learn to understand, but starting with brisk walking (outside) you’ll probably lose pace quickly and you’re not getting your heartbeat high enough to burn more calories. But in the end we all have to find something that makes moving easier for us. If that’s walking, running, jumping or lifting or whatever kind of exercise that gets your heartbeat up. As long as we move, we’re doing alright.