However, it is important to not confuse exercise (such as doing a sport or attending a fitness class) and movement (active play, walking all or part of the way to school/work/the shop, hanging the washing out). As American biomechanist Katy Bowman demonstrates in Move your DNA, exercise is only one category of movement. It is possible to be both sporty (being very active for two hours a day) and sedentary (sitting or remaining in any other fixed position, such as looking at a screen, for the bulk of the day).
Due to lack of movement, some muscles simply switch off and waste away. I witnessed it on human cadavers. The gluteal muscles become very weak because of long hours spent sitting. The muscle fibers actually come apart, just like in an overcooked bit of chicken. Get the picture? When the glutes don't engage, other muscles take on extra work that they were not designed to do, resulting in imbalances and eventually pain or injury.
Exercise usually involves a repetitive motion, using the same groups of muscles in the same or very similar way, which is likely to create imbalances and possibly injuries in the long run. To prevent any weaknesses developing, it is important to move every cell in the body.
Ideally, adults would be moving while working and children would be moving while learning. When that's not possible, movement at every other opportunity is the next best thing. The movements don't have to be big, just varied.
A change of attitude may be necessary, such as being happy when you need to put the bins out, do some weeding, or pop to the shops. Instead of "oh no, not another chore", try "yes, a chance to move my body!".
What are the opportunities for movement in your life?