What sitting all day and training regularly actually do to the same muscles
Nicola Tik
Many people who train regularly assume that exercise offsets the effects of a sedentary working day. The reality is a little more complicated than that, and understanding it can help you get more from both your training and your working day.
Prolonged sitting places certain muscles in sustained shortened or lengthened positions for hours at a time. The hip flexors, the muscles at the front of the hips, hold the legs in a seated position all day. The muscles of the lower back work continuously to maintain an upright position. The chest and front of the shoulders are held forward. The glutes, the large muscles of the backside, are largely switched off.
When you then go to the gym, a run, or a fitness class, these same muscles are asked to perform. But they are not starting from a neutral state. They are starting from several hours of sustained load, compression, or inactivity. The hip flexors that have been shortened all day are now being asked to extend fully. The glutes that have been inactive for hours are suddenly required to drive movement. The lower back that has been quietly working all day is now under additional training load.
This does not mean training after a desk day is harmful. It means the body needs a little more time and attention to transition effectively from one state to the other.
Lower back pain is one of the most common places this pattern becomes noticeable. The lumbar spine takes significant load during sitting, and when training is added on top without adequate preparation, the muscles supporting it can be asked to do more than they are ready for. This is particularly common in exercises that load the posterior chain, the back, glutes, and hamstrings, which are precisely the muscles most affected by prolonged sitting.
The hips are another area where the mismatch between sitting and training shows up frequently. Tight hip flexors affect the range of movement available during squats, lunges, and running, and can alter the way load is distributed through the lower back and knees as a result.
The shoulders follow a similar pattern. Hours of forward-reaching desk work shortens the chest and front of the shoulder while the muscles of the upper back lengthen and fatigue. Training that loads the shoulders, particularly overhead movements or pressing exercises, asks these already-compromised muscles to perform under significant load.
Evidence supports what many people experience intuitively. Sedentary time and exercise volume are related but separate variables. Studies have found that high levels of daily sitting are associated with increased injury risk and reduced training performance, even in people who meet physical activity guidelines. The body does not simply bank the benefits of a morning run against an afternoon of sitting. Each state has its own effect.
Research also shows that the muscles most affected by prolonged sitting, particularly the glutes and deep stabilisers of the spine, are among the last to activate fully during exercise without deliberate warm-up. This means they are often undercontributing during training, leaving other muscles to compensate and increasing the risk of overload in those areas.
A few things that many people find make a genuine difference. Taking short movement breaks through the working day keeps the muscles cycling through different positions rather than holding one sustained state for hours. Even standing up briefly every hour reduces the degree to which the hip flexors shorten and the glutes switch off.
Warming up with intention before training rather than going straight into working sets gives the body time to transition. A few minutes of movement that activates the glutes, opens the hips, and mobilises the spine helps the muscles that have been sitting all day come online before they are asked to perform.
Building strength in the posterior chain, the glutes, hamstrings, and muscles of the upper back, supports both training performance and the body's resilience during the working day. These are the areas most depleted by desk work and most worth investing in.
If you would like to try some guided movement that supports both your training and your working day, VIDA has exercises you can follow at your own pace.