If you're spending a lot of time thinking about how long it's going to take to get fit or reach a specific fitness goal, you're using up energy that you could be using to get started. Being "fit" means different things for different people, depending on their current level of activity. For some it means weight loss, for others it means big muscles. No matter what your goal though, the first step is to get out there and start exercising.
If you're currently sedentary, expect to see changes to your body and your overall mood after about two to four weeks of regular physical activity, suggests the American Council on Exercise. When you first get started, your focus should be on increasing your mobility and gaining enough strength to keep your body stable, as well as gaining confidence and learning to enjoy what you're doing. You shouldn't expect to get extremely "fit" during this time, but after those first few weeks, you can expect to be less sore after exercise, experience happier moods and feel more confident about exercising.
The general exercise guidelines for all adults, as recommended by the U.S. Department of Health & Human Services, are to get at least 150 minutes of moderate-intensity cardiovascular exercise each week, as well as doing strength training exercises that work all major muscle groups two days a week. That's a general recommendation for healthy adults, but if you're starting from the point of no exercise at all, don't just jump in and think you need to adhere to the guidelines letter-for-letter right away.
Building Cardiovascular Endurance
When it comes to cardiovascular exercise, sedentary people should focus on intervals of even five to 10 minutes at a time, suggests ACE. Start with low-intensity, low-impact exercises such as walking or riding a bike. When you can do 10 minutes with little effort, add five more minutes, and then add another five or 10 minutes the following week. When you're able to do about 20 minutes of steady exercise and can carry on a conversation of more than a few words at a time, it's safe to say that you've achieved an "aerobic base." At that time, you're ready to move onto more intense forms of cardiovascular exercise. If you stick to a schedule of low-intensity exercise at least five days a week, expect to achieve that aerobic base in two to six weeks. Sedentary people shouldn't hit the weight room right away, but instead spend some time gaining mobility and stability, suggests ACE. That includes floor stretches such as the cat-camels, pelvic tilts, shoulder bridges and balancing on one foot.
After that initial period, you'll be able to move into a phase where you continue to improve your aerobic fitness and build strength. From here, the timeframe for getting even more fit will be dependent on the amount of time you have to spend on fitness and the intensity at which you work out. Continue adding time to your aerobic workouts, and consider doing more intense forms of cardio, such as attending a low-impact aerobics class, jogging or swimming. As you did in the first phase, add time as the workouts get easier. For strength training, start doing bodyweight-bearing exercises such as squats, lunges, crunches and pushups. When you can do 12 to 15 repetitions of these exercises safely, you may be ready to lift weights or use exercise machines. If you started from no exercise at all, expect to be able to progress to this phase within a few months.