When I first entered the health and fitness industry 20 years ago there were pet peeves and misconceptions but they were more of the gym etiquette variety--things like using the power rack for curls, putting a towel on a piece of equipment to 'hold it' while doing something else, or men wearing spandex pants and tank tops while working out.
Nowadays, there are newer, far more insidious pet peeves and misconceptions that do far more damage than simply irritating other gym users. If you missed it, Pt 1 is here:
Pet Peeve #4
The proliferation of experts who are experts at cross-promoting each other's products in order to rise to the top of google searches. I'm sure at one time these marketing experts actually trained people and got results but now all they do is create processes to e-market their products. Not that I'm against marketing, it's just that the internet is getting clogged up with websites that exist solely to cash in on the affiliate marketing boom. Finding something useful on the internet is extremely challenging for a fitness professional, I can only imagine how confusing and frustrating it must be for a person trying to take the first step.
Pet Peeve #5
The belief that the program is the "magic bullet". You've seen them, maybe you've even been one. The gym members always looking for the perfect program, trying out a different workout every week (or even worse, not committing to do anything until they've found the 'best' program) in the faint hope that they'll find that program that shows results overnight. What's really important is doing something and giving it a chance to work. There's a great post on Dr. John Berardi's blog about an experiment they performed that showed various protocols all got results provided there was compliance with the program. The main difference between the protocols was the disparity in drop-out rates between the different protocols.
You can train with light weights if your goals are increased strength or muscle mass. I often see men and women training with weights far lighter than would be required to give their muscles adequate stimulation. I'm sure they become winded and it feels tiring but if they really wanted to maintain or even increase their muscle mass, they'd be far better off using heavier weights and cutting the volume (number of sets) way down until their conditioning improves. It does help explain why many avid gym members don't show results, they're using the wrong tools at the wrong time. This leads me to misconception #4
Building muscle and getting stronger doesn't have to be uncomfortable. Somehow this misconception gets into the heads of probably 75% of casual gym members. You see them 'working out' on the machines or even the free weights and you can't even tell they're working. Unless I have happened upon a gym full of Buddhist monks, there's no way they're all showing peaceful serenity on the outside while feeling muscle-building, strength-building strain on the inside! News Flash: Changing your body is very uncomfortable! Think about it...you have 3-10 hours every week to create the necessary stress for postive adaptations. If those hours are spent at an effort only minimally higher than the other 155-165, do you really think you're doing anything more than trying to empty the ocean with a teacup? The hours you commit to exercise have to be markedly different than the hours you spend working, sleeping, etc. Make them count!! The benefit of working hard is worth it!