There are many types of muscles in the human body; however, it’s the skeletal muscles are that used for everyday movement, including for sitting and standing. (1) More than 600 muscles are attached to your skeleton. (1) The chief muscles used to sit and stand are groups of large and small muscles working together, located in your legs and lower torso.
Legs Muscles (used Ref 2 for entire section)
Your large groups of leg muscles are your quadriceps and hamstrings. Your quadriceps are the four muscles in the front of your thigh; whereas your hamstrings are the three muscles situated in the back of your thigh. In addition to these large muscles, your gastrocnemius muscles – which are one of your calf muscles – are also engaged. Together, your leg muscles are responsible for lifting, flexing and straightening out your body as you sit and stand.
Lower Torso Muscles (used Ref 2 for entire section except for lower back/Ref 4)
Your lower torso mainly consists of large muscle groups that include your abdominals, obliques, lower back and glutes. Your rectus abdominus are situated on the front of your stomach. Obliques are the muscles located on the sides of your waist. Your lower back is made up of a group of muscles called the erector spinae -- sometimes referred to as your sacrospinal muscle group.(4) Your glutes or gluteus muscles, makes up your buttocks, with the gluteus maximus being the largest muscle in the human body. Your abs and obliques – sometimes referred to as your core – works together with your lower back and glutes to help you rotate, balance and stabilize body during sitting and standing.
As the Journal of the American Physical Therapy Association reports, variables such as seat height and the presence of arm rests effects how you sit or stand. (3) For example, the lower the seat height, the more challenging sitting and standing movements become. (3) Also, the presence of arm rests affects how far of an extension movement is needed. (3) These variables may engage additional muscles in your arm or upper torso.
Additional Muscles (used Ref 2 for entire section)
If your arms are used to help push out of a seated position for standing or assist in stabilizing your body as sit down, biceps and triceps may be utilized. Your biceps are located on the front of your upper arm, whereas your triceps are found in the back of your upper arm. Muscles that may be engaged in your upper torso are your deltoids, which are situated of the top of your shoulder, and your latissimus dorsi, which are your upper back muscles. Both deltoids and latissimus dorsi are used in pulling or pushing motions.