The 11 pieces of fitness advice you thought were true. They aren't.

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Have you ever seen a fitness meme on Instagram, or overheard a passing comment made by your spin class neighbour at the gym, that makes you think, ‘That can’t possibly be good advice’?

You’re not the only one — fitness gurus encounter these popular myths all the time. According to personal trainer Kirsty Welsh, these little tidbits of misinformation are often spread with good intentions, and aren’t wholly untrue, but they’re too all-or-nothing to be good advice for everyone.

RELATED: The fitness myth we all believe but shouldn’t

“Yes, [the advice] will reach the purpose they’re after, but it’s probably not best in terms of health on the body,” Kirsty says.

Here are just 11 of the fitness ‘pearls of wisdom’ that maybe aren’t so wise after all:

1. “Situps will give you a flat stomach”

"I would hear that at least on a fortnightly basis. It's all well and good to do situps, despite the fact they're not the most effective ab exercise, but when it comes to 'torching the fat' a large portion of that is going to come down to nutrition. Despite people being a little more educated around that space, we're still a long way off really understand how to get rid of stomach fat and how to have abs." — Blake Worrall-Thompson, trainer — Wellbeing By Blake 

2. "It's better to work out at [insert time of day]."

This sounds legit — and it is in terms of certain times being less crazily busy at the gym — but there's no solid evidence to suggest that one particular time of the day is most effective for everyone. Rather, your own body's circadian rhythm and your schedule are the best ways to determine what time suits you best to squeeze in exercise on a consistent basis. If you bound out of bed in the morning and like to go to bed at a reasonable hour, an a.m. workout is probably right up your alley. For other people, that perfect time might be in the evening after work.

"[F]ind a time that helps you make your exercise a regular, consistent part of your life," Stephen Aldana from the department of exercise sciences at Brigham Young University tells WebMD. "This is more important than the time of day."

3. "No pain, no gain!"

"Often people avoid exercise as they think the only way to get benefit is if it is painful. We need to think of exercise as movement and get some every day. Exercise is as important to the body's function as eating, drinking and breathing. The old cliché of 'no pain no gain' only really works if you want to look like a body builder but not everyone wants this. Most people want to feel better, feel stronger and have more confidence. When people train with me my aim is to have them finish a session feeling better at the end then when they started. Because at the end of the day 'no pain, no pain!'" - Greg Stark, Personal Trainer at Better Being, lululemon athletica Ambassador

Forget No pain no gain — we prefer these honest and far more sane fitness motivation posters (post continues after gallery):

4. "I've got a nutrition plan that works for everyone!"

"Nothing could be further from the truth! You are an individual. Your body is extremely complex and as such needs to be individually assessed before understanding the depths of what will and won't work for you. Start simple and think of what ultimately benefits your body's functionality, immune strength and digestion. Eliminate one thing at a time that you know is not good for you and replace it with something positive you feel works for you and benefits your energy levels. e.g. eliminate artificial soft drinks and replace with a fresh veggie juice." - Marissa Frew, Program director and Personal Trainer at Life Elements, lululemon athletica ambassador

"When it comes to diet... I am really keen on each of my clients understanding how their body responds. You can have a bad reaction to something that's really healthy; it's really important to almost create an individualised program by listening to your body and seeing how you feel and seeing what energises you." - Blake Worrall-Thompson

5. "I have to run to lose weight."

"This old saga is horrible too. Obviously [running] is the highest calorie burn for the amount of time, and effective weight loss in terms of stripping stored energy from your body, but no two bodies are the same. For example, I think it's harder for a taller person to run and keep their body in alignment and in balance because there's more lever length; everything's longer so there's more force and shock through the joints ... Not everyone can be a runner — find what feels good in your body." - Kirsty Welsh, personal trainer

RELATED: 7 workouts for people who suck at running

"Most people spend their entire day 'running'. Even if they're just running through emotions and stress, their body still thinks they are running. To add to this by running, or spending an hour keeping your heart under stress like that [through extreme cardio], can again add more stress to the body and actually cause further weight gain." — Leila Lutz, Master Trainer of NLP and Matrix Therapies at Momentum for Life, lululemon ahtletica Ambassador

6. "It's not possible to over-stretch"

"It's so possible. I've seen this a lot recently - you'll be against the wall, trying to force your body into middle split ... and people will pop weights on their legs in order to force them down toward the floor and open the middle split further. Part of me feels that is so horrendous, because your body's tight for a reason, it's not just suddenly tight. It means it's not strong enough to hold that extra range of motion. If you're trying to force flexibility into your body, where the opposing muscle group is not strong enough to support that joint structure and you try to force them open more, that's an accident waiting to happen. And if you're popping weights on your body to stretch it out further, that's brute strength, that's not cool." - Kirsty Welsh

Love a good stretch that won't do damage to your body? Try one of these back-friendly yoga moves (post continues after gallery)

7. "Women who lift heavy won't get big muscles"

"This is really based on the perspective of the individual and what, to them classifies 'big muscles'. For Example: You're not going to find the delicate long, lean, toned muscles of those who focus predominantly on yoga and Pilates within a cross-fit space. Those girls regularly lifting heavy weights with minimal repetition have the muscles to show for it. Be clear on what you want for yourself so you can structure your training to suit your desired outcome." - Marissa Frew

RELATED: Your contoured fancy gym pants are basically bullshit.

8. "I can outrun a bad diet"

"It's just been proven thousands of times that it's impossible to outrun a bad diet. You'll always hear people giving that advice on how to get lean - just go for a run, you'll be fine, or you've been for a run you can eat whatever you like now. People have this incredible ability to turn cheat meals into cheat days or cheat weekends, which isn't the most effective approach when you drag it out. I think people loosen the rules a little bit." — Blake Worrall-Thompson

RELATED: The biggest mistake you’re making with your eating habits

"Most people who are on bad diets are actually nutrient deficient and starving. The role of food is to replenish the body to give us fuel. Exercising without proper nutrition as #1 is a huge stress on the body and a stress that can put on weight." - Leila Lutz

9. "Stretching doesn't make you strong"

"You can't find optimal strength without flexibility; in order to have one you have to have the other. By increasing your flexibility you allow for more range within each movement which will push your muscles to strengthen at their full capacity. Have you ever met a muscle obsessed gym junkie that can't squat past 90degrees. It aint pretty and looks rather uncomfortable." - Marissa Frew

10. "You need to start exercising to lose weight"

"The real benefit comes from the increase in physical activity not the losing weight. Low cardiovascular fitness is the number one indicator of premature death. People often fool themselves into thinking, 'Because I am skinny I am healthy'. Being overweight isn't a good thing, but studies show it is better to be fat and fit then it is to be thin and unfit." - Greg Stark

RELATED: Make a real difference to your health in less than 6 minutes.

11. "Arse to the grass"

"People will be like, 'the lower you squat, the better'. But I know a lot of my clients are not strong enough to support the weight when you're down at that extreme range [of motion], then you're not going to be using your body properly. So if you've loaded up your back squatting with 40, 50, 60 kilograms and you're cool in that first bit of motion, but say your legs and hips aren't actually strong enough to support you with that 'arse to the grass' theory, then you're doing more damage than good." - Kirsty Welsh

Do you have any to add?