Imaginary chair explained

The imaginary chair or wall sit is a means of exercise or punishment, where one positions themselves against a wall as if seated.

A wall sit specifically refers to an exercise done to strengthen the quadriceps muscles.^[1] The exercise is characterized by the two right angles formed by the body, one at the hips and one at the knees. The person wall sitting places their back against a wall with their feet shoulder-width apart and a little ways out from the wall. Then, keeping their back against the wall, they lower their hips until their knees form right angles. This is a very intense workout for the quadriceps muscles, and it can be very painful to hold this position for extended periods. Wall sits are used as a primary strengthening exercise in many sports requiring strong quadriceps including fencing, ice hockey, sailing (mostly small boat racing), skiing and track and field.

Method

The participant should lean against the wall with their feet planted firmly on the ground, shoulder-width apart. Their feet should also be about two feet away from the wall (though the optimal distance will be somewhat dependent on the participant's height).
Once in such a position, the participant should slowly slide down the wall with their back pressed against it until their legs are bent at a right angle. This angle is very crucial because if the thighs are not parallel to the ground, the quadriceps will be bearing less load and the effectiveness of the exercise will be diminished.
The participant's knees should also be directly above their ankles and their back should be touching the wall at all times.
Depending on the participant's strength, they should hold the position for 20 seconds to a minute (or longer for more advanced athletes). If performing multiple repetitions of the exercise (three is often a recommended number), the participant should rest for half a minute in between to allow their muscles to recuperate.
As the participant gains strength, they can increase their holding time by small increments such as 10 seconds. While a burning feeling in the quadriceps muscles is normal, if the participant feels even a little pain in their knee or kneecap, they should be advised to immediately stop the activity.
The participant can hold a medicine ball or dumbbell while they sit to increase the intensity.

Benefits

Wall sitting primarily builds isometric strength and endurance in glutes, calves, quadriceps, hamstrings, and adductor muscles. A study in the British Journal of Sports Medicine of 270 trials found that isometric exercises which involve engaging muscles without movement, such as wall sits and planks, were more effective than other types of exercise for reducing blood pressure. Four repetitions of a two-minute wall sit followed by two minutes' rest, three times per week, was recommended to reduce blood pressure.^[2]

Notes and References

http://www.nismat.org/traintip/ski/ski.html Getting Ready for That Ski Trip
Web site: Bawden . Anna . Planks and wall sits best exercise for lowering blood pressure, study says . the Guardian . 25 July 2023 .