When it comes to exercise, we think about how to “get” fit. But often, starting out is not the problem. “The big problem is maintaining it,” says Falko Sniehotta, a professor of behavioural medicine and health psychology at Newcastle University. The official UK guidelines say adults should do strength exercises, as well as 150 minutes of moderate activity, or 75 minutes of vigorous activity, every week. According to the Health Survey for England in 2016, 34% of men and 42% of women are not hitting the aerobic exercise targets, and even more – 69% and 77% respectively – are not doing enough strengthening activity. A report from the World Health Organization last week found that people in the UK were among the least active in the world, with 32% of men and 40% of women reporting inactivity. Meanwhile, obesity is adding to the chronic long-term diseases cited in Public Health England’s analysis, which shows women in the UK are dying earlier than in most EU countries.

We all know we should be doing more, but how do we keep moving when our motivation slips, the weather takes a turn for the worse or life gets in the way? Try these 25 pieces of advice from experts and Guardian readers to keep you going.

1 Work out why, don’t just work out

Our reasons for beginning to exercise are fundamental to whether we will keep it up, says Michelle Segar, the director of the University of Michigan’s Sport, Health and Activity Research and Policy Center. Too often “society promotes exercise and fitness by hooking into short-term motivation, guilt and shame”. There is some evidence, she says, that younger people will go to the gym more if their reasons are appearance-based, but past our early 20s that doesn’t fuel motivation much. Nor do vague or future goals help (“I want to get fit, I want to lose weight”). Segar, the author of No Sweat: How the Simple Science of Motivation Can Bring You a Lifetime of Fitness, says we will be more successful if we focus on immediate positive feelings such as stress reduction, increased energy and making friends. “The only way we are going to prioritise time to exercise is if it is going to deliver some kind of benefit that is truly compelling and valuable to our daily life,” she says.

2 Get off to a slow start

The danger of the typical New Year resolutions approach to fitness, says personal trainer Matt Roberts, is that people “jump in and do everything – change their diet, start exercising, stop drinking and smoking – and within a couple of weeks they have lost motivation or got too tired. If you haven’t been in shape, it’s going to take time.” He likes the trend towards high-intensity interval training (HIIT) and recommends people include some, “but to do that every day will be too intense for most people”. Do it once (or twice, at most) a week, combined with slow jogs, swimming and fast walks – plus two or three rest days, at least for the first month. “That will give someone a chance of having recovery sessions alongside the high-intensity workouts.”

3 You don’t have to love it

It is helpful not to try to make yourself do things you actively dislike, says Segar, who advises thinking about the types of activities – roller-skating? Bike riding? – you liked as a child. But don’t feel you have to really enjoy exercise. “A lot of people who stick with exercise say: ‘I feel better when I do it.’” There are elements that probably will be enjoyable, though, such as the physical response of your body and the feeling of getting stronger, and the pleasure that comes with mastering a sport.

“For many people, the obvious choices aren’t necessarily the ones they would enjoy,” says Sniehotta, who is also the director of the National Institute for Health Research’s policy research unit in behavioural science, “so they need to look outside them. It might be different sports or simple things, like sharing activities with other people.”

4 Be kind to yourself

Individual motivation – or the lack of it – is only part of the bigger picture. Money, parenting demands or even where you live can all be stumbling blocks, says Sniehotta. Tiredness, depression, work stress or ill family members can all have an impact on physical activity. “If there is a lot of support around you, you will find it easier to maintain physical activity,” he points out. “If you live in certain parts of the country, you might be more comfortable doing outdoor physical activity than in others. To conclude that people who don’t get enough physical activity are just lacking motivation is problematic.”

Segar suggests being realistic. “Skip the ideal of going to the gym five days a week. Be really analytical about work and family-related needs when starting, because if you set yourself up with goals that are too big, you will fail and you’ll feel like a failure. At the end of a week, I always ask my clients to reflect on what worked and what didn’t. Maybe fitting in a walk at lunch worked, but you didn’t have the energy after work to do it.”

5 Don’t rely on willpower

“If you need willpower to do something, you don’t really want to do it,” says Segar. Instead, think about exercise “in terms of why we’re doing it and what we want to get from physical activity. How can I benefit today? How do I feel when I move? How do I feel after I move?”

6 Find a purpose

Try to move more at work. Illustration: Mark Long

Anything that allows you to exercise while ticking off other goals will help, says Sniehotta. “It provides you with more gratification, and the costs of not doing it are higher.” For instance, walking or cycling to work, or making friends by joining a sports club, or running with a friend. “Or the goal is to spend more time in the countryside, and running helps you do that.”

Try to combine physical activity with something else. “For example, in my workplace I don’t use the lift and I try to reduce email, so when it’s possible I walk over to people,” says Sniehotta. “Over the course of the day, I walk to work, I move a lot in the building and I actually get about 15,000 steps. Try to make physical activity hit as many meaningful targets as you can.”

7 Make it a habit

When you take up running, it can be tiring just getting out of the door – where are your shoes? Your water bottle? What route are you going to take? After a while, points out Sniehottta, “there are no longer costs associated with the activity”. Doing physical activity regularly and planning for it “helps make it a sustainable behaviour”. Missing sessions doesn’t.

8 Plan and prioritise

What if you don’t have time to exercise? For many people, working two jobs or with extensive caring responsibilities, this can undoubtedly be true, but is it genuinely true for you? It might be a question of priorities, says Sniehotta. He recommends planning: “The first is ‘action planning’, where you plan where, when and how you are going to do it and you try to stick with it.” The second type is ‘coping planning’: “anticipating things that can get in the way and putting a plan into place for how to get motivated again”. Segar adds: “Most people don’t give themselves permission to prioritise self-care behaviours like exercise.”

9 Keep it short and sharp

A workout doesn’t have to take an hour, says Roberts. “A well-structured 15-minute workout can be really effective if you really are pressed for time.” As for regular, longer sessions, he says: “You tell yourself you’re going to make time and change your schedule accordingly.”

10 If it doesn’t work, change it

It rains for a week, you don’t go running once and then you feel guilty. “It’s a combination of emotion and lack of confidence that brings us to the point where, if people fail a few times, they think it’s a failure of the entire project,” says Sniehotta. Remember it’s possible to get back on track.

If previous exercise regimes haven’t worked, don’t beat yourself up or try them again – just try something else, he says. “We tend to be in the mindset that if you can’t lose weight, you blame it on yourself. However, if you could change that to: ‘This method doesn’t work for me, let’s try something different,’ there is a chance it will be better for you and it prevents you having to blame yourself, which is not helpful.”

11 Add resistance and balance training as you get older

“We start to lose muscle mass over the age of around 30,” says Hollie Grant, a personal training and pilates instructor, and the owner of PilatesPT. Resistance training (using body weight, such as press-ups, or equipment, such as resistance bands) is important, she says: “It is going to help keep muscle mass or at least slow down the loss. There needs to be some form of aerobic exercise, too, and we would also recommend people start adding balance challenges because our balance is affected as we get older.”

12 Up the ante

“If you do 5k runs and you don’t know if you should push faster or go further, rate your exertion from one to 10,” says Grant. “As you see those numbers go down, that’s when to start pushing yourself a bit faster.” Roberts says that, with regular exercise, you should be seeing progress over a two-week period and pushing yourself if you feel it is getting easier. “You’re looking for a change in your speed or endurance or strength.”

13 Work out from home

You don’t need complex equipment. Illustration: Mark Long

If you have caring responsibilities, Roberts says you can do a lot within a small area at home. “In a living room, it is easy to do a routine where you might alternate between doing a leg exercise and an arm exercise,” he says. “It’s called Peripheral Heart Action training. Doing six or eight exercises, this effect of going between the upper and lower body produces a pretty strong metabolism lift and cardiovascular workout.” Try squats, half press-ups, lunges, tricep dips and glute raises. “You’re raising your heart rate, working your muscles and having a good general workout.” These take no more than 15-20 minutes and only require a chair for the tricep dips – although dumbbells can be helpful, too.

14 Get out of breath

We are often told that housework and gardening can contribute to our weekly exercise targets, but is it that simple? “The measure really is you’re getting generally hot, out of breath, and you’re working at a level where, if you have a conversation with somebody while you’re doing it, you’re puffing a bit,” says Roberts. “With gardening, you’d have to be doing the heavier gardening – digging – not just weeding. If you’re walking the dog, you can make it into a genuine exercise session – run with the dog, or find a route that includes some hills.”

15 Be sensible about illness

Joslyn Thompson Rule, a personal trainer, says: “The general rule is if it’s above the neck – a headache or a cold – while being mindful of how you’re feeling, you are generally OK to do some sort of exercise. If it’s below the neck – if you’re having trouble breathing – rest. The key thing is to be sensible. If you were planning on doing a high-intensity workout, you would take the pace down, but sometimes just moving can make you feel better.” After recovering from an illness, she says, trust your instincts. “You don’t want to go straight back into training four times a week. You might want to do the same number of sessions but make them shorter, or do fewer.”

16 Seek advice after injury

Clearly, how quickly you start exercising again depends on the type of injury, and you should seek advice from your doctor. Psychologically, though, says Thompson Rule: “Even when we’re doing everything as we should, there are still dips in the road. It’s not going to be a linear progression of getting better.”

17 Take it slowly after pregnancy

Again, says Thompson Rule, listen to your body – and your doctor’s advice at your six-week postnatal checkup. After a caesarean section, getting back to exercise will be slower, while pregnancy-related back injuries and problems with abdominal muscles all affect how soon you can get back to training, and may require physiotherapy. “Once you’re walking and have a bit more energy, depending on where you were before (some women never trained before pregnancy), starting a regime after a baby is quite something to undertake,” says Thompson Rule. “Be patient. I get more emails from women asking when they’re going to get their stomachs flat again than anything. Relax, take care of yourself and take care of your baby. When you’re feeling a bit more energised, slowly get back into your routine.” She recommends starting with “very basic stuff like walking and carrying your baby [in a sling]”.

18 Tech can help

For goal-oriented people, Grant says, it can be useful to monitor progress closely, but “allow some flexibility in your goals. You might have had a stressful day at work, go out for a run and not do it as quickly and then think: ‘I’m just not going to bother any more.’” However, “It can start to get a bit addictive, and then you don’t listen to your body and you’re more at risk of injury.”

19 Winter is not an excuse

“Winter is not necessarily a time to hibernate,” says Thompson Rule. Be decisive, put your trainers by the door and try not to think about the cold/drizzle/greyness. “It’s the same with going to the gym – it’s that voice in our head that make us feel like it’s a hassle, but once you’re there, you think: ‘Why was I procrastinating about that for so long?’”

READERS’ TIPS

20 Keep it bite-size

Alex Tomlin

I’ve tried and failed a few times to establish a consistent running routine, but that was because I kept pushing myself too hard. Just because I can run for an hour doesn’t mean I should. Running two or three times a week for 20-30 minutes each time has improved my fitness hugely and made it easier to fit in.

21 Reward yourself

Neil Richardson

I keep a large bag of Midget Gems in my car to motivate myself to get to the gym, allowing myself a handful before a workout. Sometimes I toss in some wine gums for the element of surprise.

22 Call in the reinforcements

Niall O’Brien

I tapped into the vast network of fitness podcasts and online communities. On days I lacked drive, I would listen to a fitness podcast, and by the time I got home, I would be absolutely determined to make the right choices. In fact, I would be excited by it. Your brain responds very well to repetition and reinforcement, so once you have made the difficult initial change, it becomes much easier over time.

23 Use visual motivation

Siobhan King

I have kept a “star chart” on my calendar for the past two years, after having three years of being chronically unfit. I put a gold star on days that I exercise, and it’s a good visual motivator for when I am feeling slug-like. I run, use our home cross-trainer and do a ski fitness programme from an app. My improved core strength has helped my running and ability to carry my disabled child when needed.

24 Keep alarms out of reach

Sally Crowe

If, like me, you need to get up early to exercise or it just doesn’t happen, move your alarm clock away from your bed and next to your kit. Once you have got up to turn it off, you might as well keep going!

25 Follow the four-day rule

Joanne Chalmers

I have one simple rule which could apply to any fitness activity – I do not allow more than four days to elapse between sessions. So, if I know I have a busy couple of days coming up, I make sure I run before them so that I have “banked” my four days. With the exception of illness, injury or family emergencies, I have stuck to this rule for 10 years.