My gym has sporadic phone signal, so in between exercises, I spend a lot of time watching what people around me are doing. And I see a lot of people making the same mistakes.

I don’t mean mistakes like not putting their equipment away or wiping it down at the end of a session, though this is annoying and people need to stop doing this. I mean mistakes that are preventing them from getting the most out of the gym and, potentially, them hurting themselves.

1 Bad technique

If I owned a gym, I would spend 10 minutes with every new joiner making sure they had squats and lunges nailed, because they’re so easy to correct but so commonly done wrong. There’s many more moves that you can mess up, but these are two entry level exercises that have an endless number of variations and progressions, so let’s get everyone nailing the basics.

Most obviously, look down or into a mirror and see where your knee goes. It shouldn’t be moving forward over your toes or leaning in, it should stay above your ankle. So on a squat, you need to make your bum go backwards and down as though you’re sitting on an invisible chair. If you’re lunging, you probably need to take a slightly bigger step forwards and lower your body straight down, not forwards and down.

Have a look in the mirror, that’s what they’re there for despite what those flexing their guns in them all the time might think. You can also ask a PT or gym assistant to have a look at your technique. They’re primarily there for your safety, which I think covers proper technique. They would probably also jump at the chance to have a 5 min chat with you because it might make you think about booking a 1-1 session with them.

2 Not having a plan

Heading to the gym without a plan for what you’re going to do while you’re there means you’re going to wander round a bit aimlessly and waste a lot of time. At the very least, decide whether you’re going to focus on cardio or weights – so for runners, doing a run session on the treadmill or cross-training on a bike Vs strength training. Most of us are short on time, so it’s best not to a bit of bit of both without giving either you’re full attention.

If you’re going to be doing some strength training, what area are you focusing on? All session should include some core work (done at the end), so start by putting together a few core exercises that you know how to do and that will work on all areas of your core. Ideally you’d get a PT to put something together for you but that’s not an option for everyone. You can find unlimited workout online or in books and magazines. You can then write these down in your phone so you can refer back to this at the gym.

3 Using weights that are too light

Here’s a simple tip: nobody other than those being rehabilitated from serious illness or injury needs to use the 1kg weights for bicep curls or shoulder presses. Nobody. You regularly pick up things heavier than this in your daily life without even thinking about it.

If you can whaft a weight around with ease and do any exercise 15+ times without even feeling it, your weight is too light. I know that a lot of people are concerned about hurting themselves with heavy weights but if you’ve got your technique right, be bold about choosing a weight that you can feel. And, although this point might be getting a bit repetitive, get some advice.

4 Wearing their running shoes

OK, I know that working out can get a little costly and I don’t want you to feel forced to spend even more money on it. But if you’re able to wear a lighter weight shoe to the gym, it’s a good idea.

If you wear supportive trainers to run in, these are going to do some of the work of stabilising you at the gym. And this takes the fun out of it. Because when your foot is unshod, you have to work harder to keep your balance and a whole load of muscles in your lower leg and feet that you haven’t felt before will come to life.

5 Sticking to what they know too rigidly

You put together your plan so you know what you’re going to do at the gym. But then someone is using the leg press when you want to use it. So either you wait it out, or you skip that bit of your workout.

If you have a couple of options for working each muscle group, not only will it help you vary your workout between sessions so you don’t get bored, but when the equipment you want to use is in use, you have an alternative exercise to substitute it for. So next time someone is hogging the leg press, do some weighted squat instead. Just make sure you’ve got your technique right. Did I say that already?

If you’re working towards your first 10k, you’ll find a simple strength plan in my 10k Training Guide.